Publications

Abstract

CONTEXT Recent studies have shown an association between cigarettes per day (CPD) and a nonsynonymous single-nucleotide polymorphism in CHRNA5, rs16969968. OBJECTIVE To determine whether the association between rs16969968 and smoking is modified by age at onset of regular smoking. DATA SOURCES Primary data. STUDY SELECTION Available genetic studies containing measures of CPD and the genotype of rs16969968 or its proxy. DATA EXTRACTION Uniform statistical analysis scripts were run locally. Starting with 94 050 ever-smokers from 43 studies, we extracted the heavy smokers (CPD >20) and light smokers (CPD ≤10) with age-at-onset information, reducing the sample size to 33 348. Each study was stratified into early-onset smokers (age at onset ≤16 years) and late-onset smokers (age at onset >16 years), and a logistic regression of heavy vs light smoking with the rs16969968 genotype was computed for each stratum. Meta-analysis was performed within each age-at-onset stratum. DATA SYNTHESIS Individuals with 1 risk allele at rs16969968 who were early-onset smokers were significantly more likely to be heavy smokers in adulthood (odds ratio [OR] = 1.45; 95% CI, 1.36-1.55; n = 13 843) than were carriers of the risk allele who were late-onset smokers (OR = 1.27; 95% CI, 1.21-1.33, n = 19 505) (P = .01). CONCLUSION These results highlight an increased genetic vulnerability to smoking in early-onset smokers.

Abstract

Cultural transmission is a key component of human evolution. Two of humans' closest living relatives, chimpanzees and orangutans, have also been argued to transmit behavioral traditions across generations culturally [ [1], [2] and [3]], but how much the process might resemble the human process is still in large part unknown. One key phenomenon of human cultural transmission is majority-biased transmission: the increased likelihood for learners to end up not with the most frequent behavior but rather with the behavior demonstrated by most individuals. Here we show that chimpanzees and human children as young as 2 years of age, but not orangutans, are more likely to copy an action performed by three individuals, once each, than an action performed by one individual three times. The tendency to acquire the behaviors of the majority has been posited as key to the transmission of relatively safe, reliable, and productive behavioral strategies [ [4], [5], [6] and [7]] but has not previously been demonstrated in primates.

Abstract

We used functional magnetic resonance imaging (fMRI) to investigate the neural basis of comprehension and perceptual learning of artificially degraded [noise vocoded (NV)] speech. Fifteen participants were scanned while listening to 6-channel vocoded words, which are difficult for naive listeners to comprehend, but can be readily learned with appropriate feedback presentations. During three test blocks, we compared responses to potentially intelligible NV words, incomprehensible distorted words and clear speech. Training sessions were interleaved with the test sessions and included paired presentation of clear then noise-vocoded words: a type of feedback that enhances perceptual learning. Listeners' comprehension of NV words improved significantly as a consequence of training. Listening to NV compared to clear speech activated left insula, and prefrontal and motor cortices. These areas, which are implicated in speech production, may play an active role in supporting the comprehension of degraded speech. Elevated activation in the precentral gyrus during paired clear-then-distorted presentations that enhance learning further suggests a role for articulatory representations of speech in perceptual learning of degraded speech.

Abstract

Background Reduced total brain volume is a consistent finding in children with Attention Deficit/Hyperactivity Disorder (ADHD). In order to get a better understanding of the neurobiology of ADHD, we take the first step in studying the dimensionality of current self-reported adult ADHD symptoms, by looking at its relation with total brain volume. Methodology/Principal Findings In a sample of 652 highly educated adults, the association between total brain volume, assessed with magnetic resonance imaging, and current number of self-reported ADHD symptoms was studied. The results showed an association between these self-reported ADHD symptoms and total brain volume. Post-hoc analysis revealed that the symptom domain of inattention had the strongest association with total brain volume. In addition, the threshold for impairment coincides with the threshold for brain volume reduction. Conclusions/Significance This finding improves our understanding of the biological substrates of self-reported ADHD symptoms, and suggests total brain volume as a target intermediate phenotype for future gene-finding in ADHD.

Abstract

We investigated 4- and 5-year-old children’s mapping strategies in a spatial task. Children were required to find a picture in an array of three identical cups after observing another picture being hidden in another array of three cups. The arrays were either aligned one behind the other in two rows or placed side by side forming one line. Moreover, children were rewarded for two different mapping strategies. Half of the children needed to choose a cup that held the same relative position as the rewarded cup in the other array; they needed to map left–left, middle–middle, and right–right cups together (aligned mapping), which required encoding and mapping of two relations (e.g., the cup left of the middle cup and left of the right cup). The other half needed to map together the cups that held the same relation to the table’s spatial features—the cups at the edges, the middle cups, and the cups in the middle of the table (landmark mapping)—which required encoding and mapping of one relation (e.g., the cup at the table’s edge). Results showed that children’s success was constellation dependent; performance was higher when the arrays were aligned one behind the other in two rows than when they were placed side by side. Furthermore, children showed a preference for landmark mapping over aligned mapping.

Abstract

The experimental investigation of language-mediated visual attention is a promising way to study the interaction of the cognitive systems involved in language, vision, attention, and memory. Here we highlight four challenges for a mechanistic account of this oculomotor behavior: the levels of representation at which language-derived and vision-derived representations are integrated; attentional mechanisms; types of memory; and the degree of individual and group differences. Central points in our discussion are (a) the possibility that local microcircuitries involving feedforward and feedback loops instantiate a common representational substrate of linguistic and non-linguistic information and attention; and (b) that an explicit working memory may be central to explaining interactions between language and visual attention. We conclude that a synthesis of further experimental evidence from a variety of fields of inquiry and the testing of distinct, non-student, participant populations will prove to be critical.

Abstract

Being ostracized or excluded, even briefly and by strangers, is painful and threatens fundamental needs. Recent work by Zhong and Leonardelli (2008) found that excluded individuals perceive the room as cooler and that they desire warmer drinks. A perspective that many rely on in embodiment is the theoretical idea that people use metaphorical associations to understand social exclusion (see Landau, Meier, & Keefer, 2010). We suggest that people feel colder because they are colder. The results strongly support the idea that more complex metaphorical understandings of social relations are scaffolded onto literal changes in bodily temperature: Being excluded in an online ball tossing game leads to lower finger temperatures (Study 1), while the negative affect typically experienced after such social exclusion is alleviated after holding a cup of warm tea (Study 2). The authors discuss further implications for the interaction between body and social relations specifically, and for basic and cognitive systems in general.

Abstract

During aging, intracranial volume remains unchanged and represents maximally attained brain size, while various interacting biological phenomena lead to brain volume loss. Consequently, intracranial volume and brain volume in late life reflect different genetic influences. Our genome-wide association study (GWAS) in 8,175 community-dwelling elderly persons did not reveal any associations at genome-wide significance (P < 5 × 10(-8)) for brain volume. In contrast, intracranial volume was significantly associated with two loci: rs4273712 (P = 3.4 × 10(-11)), a known height-associated locus on chromosome 6q22, and rs9915547 (P = 1.5 × 10(-12)), localized to the inversion on chromosome 17q21. We replicated the associations of these loci with intracranial volume in a separate sample of 1,752 elderly persons (P = 1.1 × 10(-3) for 6q22 and 1.2 × 10(-3) for 17q21). Furthermore, we also found suggestive associations of the 17q21 locus with head circumference in 10,768 children (mean age of 14.5 months). Our data identify two loci associated with head size, with the inversion at 17q21 also likely to be involved in attaining maximal brain size.

Abstract

Clahsen's characterization of nondefault inflection as based exclusively on lexical entries does not capture the full range of empirical data on German inflection. In the verb system differential effects of lexical frequency seem to be input-related rather than affecting morphological production. In the noun system, the generalization properties of -n and -e plurals exceed mere analogy-based productivity.

Abstract

Infectious diseases exert a constant evolutionary pressure on the innate immunity genes. TLR4, an important member of the Toll-like receptors family, specifically recognizes conserved structures of various infectious pathogens. Two functional TLR4 polymorphisms, Asp299Gly and Thr399Ile, modulate innate host defense against infections, and their prevalence between various populations has been proposed to be influenced by local infectious pressures. If this assumption is true, strong local infectious pressures would lead to a homogeneous pattern of these ancient TLR4 polymorphisms in geographically close populations, while a weak selection or genetic drift may result in a diverse pattern. We evaluated TLR4 polymorphisms in 15 ethnic groups of Iran, to assess whether infections exerted selective pressures on different haplotypes containing these variants. The Iranian subpopulations displayed a heterogeneous pattern of TLR4 polymorphisms, comprising various percentages of Asp299Gly and Thr399Ile alone or in combination. The Iranian sample as a whole showed an intermediate mixed pattern when compared with commonly found patterns in Africa, Europe, Eastern Asia and Americas. These findings suggest a weak or absent selection pressure on TLR4 polymorphisms in the Middle-East, that does not support the assumption of an important role of these polymorphisms in the host defence against local pathogens.

Abstract

Hereditary mixed polyposis syndrome (HMPS) is characterized by apparent autosomal dominant inheritance of multiple types of colorectal polyp, with colorectal carcinoma occurring in a high proportion of affected individuals. Here, we use genetic mapping, copy-number analysis, exclusion of mutations by high-throughput sequencing, gene expression analysis and functional assays to show that HMPS is caused by a duplication spanning the 3' end of the SCG5 gene and a region upstream of the GREM1 locus. This unusual mutation is associated with increased allele-specific GREM1 expression. Whereas GREM1 is expressed in intestinal subepithelial myofibroblasts in controls, GREM1 is predominantly expressed in the epithelium of the large bowel in individuals with HMPS. The HMPS duplication contains predicted enhancer elements; some of these interact with the GREM1 promoter and can drive gene expression in vitro. Increased GREM1 expression is predicted to cause reduced bone morphogenetic protein (BMP) pathway activity, a mechanism that also underlies tumorigenesis in juvenile polyposis of the large bowel.

Abstract

In this study, older adults monitored for pre-assigned target sounds in a target talker's speech in a quiet (no noise) condition and in a condition with competing-talker noise. The question was to which extent the impact of the competing-talker noise on performance could be predicted from individual hearing loss and from a cognitive measure of inhibitory abilities, i.e., a measure of Stroop interference. The results showed that the non-auditory measure of Stroop interference predicted the impact of distraction on performance, over and above the effect of hearing loss. This suggests that individual differences in inhibitory abilities among older adults relate to susceptibility to distracting speech.

Abstract

Microarrays provide a powerful analytical tool for the simultaneous detection of multiple pathogens. We developed diagnostic suspension microarrays for sensitive and specific detection of the biothreat pathogens Bacillus anthracis, Yersinia pestis, Francisella tularensis and Coxiella burnetii. Two assay chemistries for amplification and labeling were developed, one method using direct hybridization and the other using target-specific primer extension, combined with hybridization to universal arrays. Asymmetric PCR products for both assay chemistries were produced by using a multiplex asymmetric PCR amplifying 16 DNA signatures (16-plex). The performances of both assay chemistries were compared and their advantages and disadvantages are discussed. The developed microarrays detected multiple signature sequences and an internal control which made it possible to confidently identify the targeted pathogens and assess their virulence potential. The microarrays were highly specific and detected various strains of the targeted pathogens. Detection limits for the different pathogen signatures were similar or slightly higher compared to real-time PCR. Probit analysis showed that even a few genomic copies could be detected with 95% confidence. The microarrays detected DNA from different pathogens mixed in different ratios and from spiked or naturally contaminated samples. The assays that were developed have a potential for application in surveillance and diagnostics. © 2012 Janse et al.

Abstract

We investigated comprehension of and adaptation to speech in an unfamiliar accent in older adults. Participants performed a speeded sentence verification task for accented sentences: one group upon auditory-only presentation, and the other group upon audiovisual presentation. Our questions were whether audiovisual presentation would facilitate adaptation to the novel accent, and which cognitive and linguistic measures would predict adaptation. Participants were therefore tested on a range of background tests: hearing acuity, auditory verbal short-term memory, working memory, attention-switching control, selective attention, and vocabulary knowledge. Both auditory-only and audiovisual groups showed improved accuracy and decreasing response times over the course of the experiment, effectively showing accent adaptation. Even though the total amount of improvement was similar for the auditory-only and audiovisual groups, initial rate of adaptation was faster in the audiovisual group. Hearing sensitivity and short-term and working memory measures were associated with efficient processing of the novel accent. Analysis of the relationship between accent comprehension and the background tests revealed furthermore that selective attention and vocabulary size predicted the amount of adaptation over the course of the experiment. These results suggest that vocabulary knowledge and attentional abilities facilitate the attention-shifting strategies proposed to be required for perceptual learning.

Abstract

In this study we investigate whether speakers, in line with the predictions of the Hyper- and Hypospeech theory, speed up most during the least informative parts and less during the more informative parts, when they are asked to speak faster. We expected listeners to benefit from these changes in timing, and our main goal was to find out whether making the temporal organisation of artificially time-compressed speech more like that of natural fast speech would improve intelligibility over linear time compression. Our production study showed that speakers reduce unstressed syllables more than stressed syllables, thereby making the prosodic pattern more pronounced. We extrapolated fast speech timing to even faster rates because we expected that the more salient prosodic pattern could be exploited in difficult listening situations. However, at very fast speech rates, applying fast speech timing worsens intelligibility. We argue that the non-uniform way of speeding up may not be due to an underlying communicative principle, but may result from speakers’ inability to speed up otherwise. As both prosodic and segmental information contribute to word recognition, we conclude that extrapolating fast speech timing to extremely fast rates distorts this balance between prosodic and segmental information.

Abstract

This functional magnetic resonance imaging (fMRI) study investigates a crucial parameter in spatial description, namely variants in the frame of reference chosen. Two frames of reference are available in European languages for the description of small-scale assemblages, namely the intrinsic (or object-oriented) frame and the relative (or egocentric) frame. We showed participants a sentence such as “the ball is in front of the man”, ambiguous between the two frames, and then a picture of a scene with a ball and a man – participants had to respond by indicating whether the picture did or did not match the sentence. There were two blocks, in which we induced each frame of reference by feedback. Thus for the crucial test items, participants saw exactly the same sentence and the same picture but now from one perspective, now the other. Using this method, we were able to precisely pinpoint the pattern of neural activation associated with each linguistic interpretation of the ambiguity, while holding the perceptual stimuli constant. Increased brain activity in bilateral parahippocampal gyrus was associated with the intrinsic frame of reference whereas increased activity in the right superior frontal gyrus and in the parietal lobe was observed for the relative frame of reference. The study is among the few to show a distinctive pattern of neural activation for an abstract yet specific semantic parameter in language. It shows with special clarity the nature of the neural substrate supporting each frame of spatial reference

Abstract

The QWERTY keyboard mediates communication for millions of language users. Here, we investigated whether differences in the way words are typed correspond to differences in their meanings. Some words are spelled with more letters on the right side of the keyboard and others with more letters on the left. In three experiments, we tested whether asymmetries in the way people interact with keys on the right and left of the keyboard influence their evaluations of the emotional valence of the words. We found the predicted relationship between emotional valence and QWERTY key position across three languages (English, Spanish, and Dutch). Words with more right-side letters were rated as more positive in valence, on average, than words with more left-side letters: the QWERTY effect. This effect was strongest in new words coined after QWERTY was invented and was also found in pseudowords. Although these data are correlational, the discovery of a similar pattern across languages, which was strongest in neologisms, suggests that the QWERTY keyboard is shaping the meanings of words as people filter language through their fingers. Widespread typing introduces a new mechanism by which semanntic changes in language can arise.

Abstract

Curiosity is one of the most basic biological drives in both animals and humans, and has been identified as a key motive for learning and discovery. Despite the importance of curiosity and related behaviors, the topic has been largely neglected in human neuroscience; hence little is known about the neurobiological mechanisms underlying curiosity. We used functional magnetic resonance imaging (fMRI) to investigate what happens in our brain during the induction and subsequent relief of perceptual curiosity. Our core findings were that (1) the induction of perceptual curiosity, through the presentation of ambiguous visual input, activated the anterior insula and anterior cingulate cortex (ACC), brain regions sensitive to conflict and arousal; (2) the relief of perceptual curiosity, through visual disambiguation, activated regions of the striatum that have been related to reward processing; and (3) the relief of perceptual curiosity was associated with hippocampal activation and enhanced incidental memory. These findings provide the first demonstration of the neural basis of human perceptual curiosity. Our results provide neurobiological support for a classic psychological theory of curiosity, which holds that curiosity is an aversive condition of increased arousal whose termination is rewarding and facilitates memory.

Abstract

A. Caramazza, A. Costa, M. Miozzo, and Y. Bi(2001) reported a series of experiments demonstrating that the ease of producing a word depends only on the frequency of that specific word but not on the frequency of a homophone twin. A. Caramazza, A. Costa, et al. concluded that homophones have separate word form representations and that the absence of frequency-inheritance effects for homophones undermines an important argument in support of 2-stage models of lexical access, which assume that syntactic (lemma) representations mediate between conceptual and phonological representations. The authors of this article evaluate the empirical basis of this conclusion, report 2 experiments demonstrating a frequency-inheritance effect, and discuss other recent evidence. It is concluded that homophones share a common word form and that the distinction between lemmas and word forms should be upheld.

Abstract

Older listeners are more affected than younger listeners in their recognition of speech in adverse conditions, such as when they also hear a single-competing speaker. In the present study, we investigated with a speeded response task whether older listeners with various degrees of hearing loss benefit under such conditions from also seeing the speaker they intend to listen to. We also tested, at the same time, whether older adults need postperceptual processing to obtain an audiovisual benefit. When tested in a phoneme-monitoring task with single-talker noise present, older (and younger) listeners detected target phonemes more reliably and more rapidly in meaningful sentences uttered by the target speaker when they also saw the target speaker. This suggests that older adults processed audiovisual speech rapidly and efficiently enough to benefit already during spoken sentence processing. Audiovisual benefits for older adults were similar in size to those observed for younger adults in terms of response latencies, but smaller for detection accuracy. Older adults with more hearing loss showed larger audiovisual benefits. Attentional abilities predicted the size of audiovisual response time benefits in both age groups. Audiovisual benefits were found in both age groups when monitoring for the visually highly distinct phoneme /p/ and when monitoring for the visually less distinct phoneme /k/. Visual speech thus provides segmental information about the target phoneme, but also provides more global contextual information that helps both older and younger adults in this adverse listening situation.

Abstract

Using a referent detection paradigm, we examined whether listeners can determine the object speakers are referring to by using the temporal alignment between the motion speakers impose on objects and their labeling utterances. Stimuli were created by videotaping speakers labeling a novel creature. Without being explicitly instructed to do so, speakers moved the creature during labeling. Trajectories of these motions were used to animate photographs of the creature. Participants in subsequent perception studies heard these labeling utterances while seeing side-by-side animations of two identical creatures in which only the target creature moved as originally intended by the speaker. Using the cross-modal temporal relationship between speech and referent motion, participants identified which creature the speaker was labeling, even when the labeling utterances were low-pass filtered to remove their semantic content or replaced by tone analogues. However, when the prosodic structure was eliminated by reversing the speech signal, participants no longer detected the referent as readily. These results provide strong support for a prosodic cross-modal alignment hypothesis. Speakers produce a perceptible link between the motion they impose upon a referent and the prosodic structure of their speech, and listeners readily use this prosodic cross-modal relationship to resolve referential ambiguity in word-learning situations.

Abstract

Although the human brain may have evolutionarily adapted to face-to-face communication, other modes of communication, e.g., telephone and e-mail, increasingly dominate our modern daily life. This study examined the neural difference between face-to-face communication and other types of communication by simultaneously measuring two brains using a hyperscanning approach. The results showed a significant increase in the neural synchronization in the left inferior frontal cortex during a face-to-face dialog between partners but none during a back-to-back dialog, a face-to-face monologue, or a back-to-back monologue. Moreover, the neural synchronization between partners during the face-to-face dialog resulted primarily from the direct interactions between the partners, including multimodal sensory information integration and turn-taking behavior. The communicating behavior during the face-to-face dialog could be predicted accurately based on the neural synchronization level. These results suggest that face-to-face communication, particularly dialog, has special neural features that other types of communication do not have and that the neural synchronization between partners may underlie successful face-to-face communication.

Abstract

The Possible Word Constraint limits the number of lexical candidates considered in speech recognition by stipulating that input should be parsed into a string of lexically viable chunks. For instance, an isolated single consonant is not a feasible word candidate. Any segmentation containing such a chunk is disfavored. Five experiments using the head-turn preference procedure investigated whether, like adults, 12-month-olds observe this constraint in word recognition. In Experiments 1 and 2, infants were familiarized with target words (e.g., rush), then tested on lists of nonsense items containing these words in “possible” (e.g., “niprush” [nip + rush]) or “impossible” positions (e.g., “prush” [p + rush]). The infants listened significantly longer to targets in “possible” versus “impossible” contexts when targets occurred at the end of nonsense items (rush in “prush”), but not when they occurred at the beginning (tan in “tance”). In Experiments 3 and 4, 12-month-olds were similarly familiarized with target words, but test items were real words in sentential contexts (win in “wind” versus “window”). The infants listened significantly longer to words in the “possible” condition regardless of target location. Experiment 5 with targets at the beginning of isolated real words (e.g., win in “wind”) replicated Experiment 2 in showing no evidence of viability effects in beginning position. Taken together, the findings suggest that, in situations in which 12-month-olds are required to rely on their word segmentation abilities, they give evidence of observing lexical viability constraints in the way that they parse fluent speech.

Abstract

Around their first birthday infants begin to talk, yet they comprehend words long before. This study investigated the event-related potentials (ERP) responses of nine-month-olds on basic level picture-word pairings. After a familiarization phase of six picture-word pairings per semantic category, comprehension for novel exemplars was tested in a picture-word matching paradigm. ERPs time-locked to pictures elicited a modulation of the Negative Central (Nc) component, associated with visual attention and recognition. It was attenuated by category repetition as well as by the type-token ratio of picture context. ERPs time-locked to words in the training phase became more negative with repetition (N300-600), but there was no influence of picture type-token ratio, suggesting that infants have identified the concept of each picture before a word was presented. Results from the test phase provided clear support that infants integrated word meanings with (novel) picture context. Here, infants showed different ERP responses for words that did or did not align with the picture context: a phonological mismatch (N200) and a semantic mismatch (N400). Together, results were informative of visual categorization, word recognition and word-to-world-mappings, all three crucial processes for vocabulary construction.

Abstract

Infants’ ability to recognize words in continuous speech is vital for building a vocabulary.We here examined the amount and type
of exposure needed for 10-month-olds to recognize words. Infants first heard a word, either embedded within an utterance or in
isolation, then recognition was assessed by comparing event-related potentials to this word versus a word that they had not heard
directly before. Although all 10-month-olds showed recognition responses to words first heard in isolation, not all infants showed
such responses to words they had first heard within an utterance. Those that did succeed in the latter, harder, task, however,
understood more words and utterances when re-tested at 12 months, and understood more words and produced more words at
24 months, compared with those who had shown no such recognition response at 10 months. The ability to rapidly recognize the
words in continuous utterances is clearly linked to future language development.

Abstract

Hand gestures combine with speech to form a single integrated system of meaning during language comprehension (Kelly et al., 2010). However, it is unknown whether gesture is uniquely integrated with speech or is processed like any other manual action. Thirty-one participants watched videos presenting speech with gestures or manual actions on objects. The relationship between the speech and gesture/action was either complementary (e.g., “He found the answer,” while producing a calculating gesture vs. actually using a calculator) or incongruent (e.g., the same sentence paired with the incongruent gesture/action of stirring with a spoon). Participants watched the video (prime) and then responded to a written word (target) that was or was not spoken in the video prime (e.g., “found” or “cut”). ERPs were taken to the primes (time-locked to the spoken verb, e.g., “found”) and the written targets. For primes, there was a larger frontal N400 (semantic processing) to incongruent vs. congruent items for the gesture, but not action, condition. For targets, the P2 (phonemic processing) was smaller for target words following congruent vs. incongruent gesture, but not action, primes. These findings suggest that hand gestures are integrated with speech in a privileged fashion compared to manual actions on objects.

Abstract

When you compare the behavior of two different age groups which are trying to master the same sensori-motor or cognitive skill, you are likely to discover varying learning routes: different stages, different intervals between stages, or even different orderings of stages. Such heterogeneous learning trajectories may be caused by at least six different types of factors: (1) Initial state: the kinds and levels of skills the learners have available at the onset of the learning episode. (2) Learning mechanisms: rule-based, inductive, connectionist, parameter setting, and so on. (3) Input and feedback characteristics: learning stimuli, information about success and failure. (4) Information processing mechanisms: capacity limitations, attentional biases, response preferences. (5) Energetic variables: motivation, emotional reactions. (6) Final state: the fine-structure of kinds and levels of subskills at the end of the learning episode. This applies to language acquisition as well. First and second language learners probably differ on all six factors. Nevertheless, the debate between advocates and opponents of the Fundamental Difference Hypothesis concerning L1 and L2 acquisition have looked almost exclusively at the first two factors. Those who believe that L1 learners have access to Universal Grammar whereas L2 learners rely on language processing strategies, postulate different learning mechanisms (UG parameter setting in L1, more general inductive strategies in L2 learning). Pienemann opposes this view and, based on his Processability Theory, argues that L1 and L2 learners start out from different initial states: they come to the grammar learning task with different structural hypotheses (SOV versus SVO as basic word order of German).

Abstract

In a recent Cognition paper (Cognition 85 (2002) B21), Bornkessel, Schlesewsky, and Friederici report ERP data that they claim “show that online processing difficulties induced by word order variations in German cannot be attributed to the relative infrequency of the constructions in question, but rather appear to reflect the application of grammatical principles during parsing” (p. B21). In this commentary we demonstrate that the posited contrast between grammatical principles and construction (in)frequency as sources of parsing problems is artificial because it is based on factually incorrect assumptions about the grammar of German and on inaccurate corpus frequency data concerning the German constructions involved.

Abstract

Remarques sur les facteurs intervenant dans le processus de formulation des énoncés.

Abstract

Grammatical encoding and grammatical decoding (in sentence production and comprehension, respectively) are often portrayed as independent modalities of grammatical performance that only share declarative resources: lexicon and grammar. The processing resources subserving these modalities are supposed to be distinct. In particular, one assumes the existence of two workspaces where grammatical structures are assembled and temporarily maintained—one for each modality. An alternative theory holds that the two modalities share many of their processing resources and postulates a single mechanism for the online assemblage and short-term storage of grammatical structures: a shared workspace. We report two experiments with a novel “grammatical multitasking” paradigm: the participants had to read (i.e., decode) and to paraphrase (encode) sentences presented in fragments, responding to each input fragment as fast as possible with a fragment of the paraphrase. The main finding was that grammatical constraints with respect to upcoming input that emanate from decoded sentence fragments are immediately replaced by grammatical expectations emanating from the structure of the corresponding paraphrase fragments. This evidences that the two modalities have direct access to, and operate upon, the same (i.e., token-identical) grammatical structures. This is possible only if the grammatical encoding and decoding processes command the same, shared grammatical workspace. Theoretical implications for important forms of grammatical multitasking—self-monitoring, turn-taking in dialogue, speech shadowing, and simultaneous translation—are explored.

Abstract

The psychology of language as developed by Wilhelm Wundt in his fundamental work Die Sprache (1900) has a strongly mentalistic character. The dominating positions held by behaviorism in psychology and structuralism in linguistics have overruled Wundt’s language theory to the effect that it has remained relatively unknown. This situation has changed recently under the influence of transformational linguistics and cognitive psychology. The paper discusses how Wundt applied the basic psychological concepts of apperception and association to language behavior, in particular to the construction and production of sentences during unprepared speech. The final part of the paper is devoted to the work, published in 1917, of the Dutch linguistic scholar Jacques van Ginneken, who elaborated Wundt’s ideas towards an explanation of some syntactic phenomena during the language acquisition of children.

Abstract

This article reports on an individual differences study that investigated the role of implicit statistical learning in the acquisition of syntax in children. One hundred children ages 4 years 5 months through 6 years 11 months completed a test of implicit statistical learning, a test of explicit declarative learning, and standardized tests of verbal and nonverbal ability. They also completed a syntactic priming task, which provided a dynamic index of children's facility to detect and respond to changes in the input frequency of linguistic structure. The results showed that implicit statistical learning ability was directly associated with the long-term maintenance of the primed structure. The results constitute the first empirical demonstration of a direct association between implicit statistical learning and syntactic acquisition in children.

Abstract

Although the syntactic priming methodology is a promising tool for language acquisition researchers, using the technique with children raises issues that are not problematic in adult research. The current paper reports on an individual differences study that addressed some of these outstanding issues. (a) Does priming purely reflect syntactic knowledge, or are other processes involved? (b) How can we explain individual differences, which are the norm rather than the exception? (c) Do priming effects in developmental populations reflect the same mechanisms thought to be responsible for priming in adults? One hundred twenty-two (N = 122) children aged 4 years, 5 months (4;5)–6;11 (mean = 5;7) completed a syntactic priming task that aimed to prime the English passive construction, in addition to standardized tests of vocabulary, grammar, and nonverbal intelligence. The results confirmed the widely held assumption that syntactic priming reflects the presence of syntactic knowledge, but not in every instance. However, they also suggested that nonlinguistic processes contribute significantly to priming. Priming was in no way related to age. Finally, the children's linguistic knowledge and nonverbal ability determined the manner in which they were primed. The results provide a clearer picture of what it means to be primed in acquisition.

Abstract

Eisenberg (2002) presents data from an experiment investigating three- and four-year-old children's comprehension of restrictive relative clauses (RC). From the results she argues, contrary to Hamburger & Crain (1982), that children do not have discourse knowledge of the felicity conditions of RCs before acquiring the syntax of relativization. This note evaluates this conclusion on the basis of the methodology used, and proposes that an account of syntactic development needs to be sensitive to the real-time processing requirements acquisition places on the learner.

Abstract

How do Dutch and Korean listeners use acoustic–phonetic information when learning words in an artificial language? Dutch has a voiceless ‘unaspirated’ stop, produced with shortened Voice Onset Time (VOT) in prosodic strengthening environments (e.g., in domain-initial position and under prominence), enhancing the feature {−spread glottis}; Korean has a voiceless ‘aspirated’ stop produced with lengthened VOT in similar environments, enhancing the feature {+spread glottis}. Given this cross-linguistic difference, two competing hypotheses were tested. The phonological-superiority hypothesis predicts that Dutch and Korean listeners should utilize shortened and lengthened VOTs, respectively, as cues in artificial-language segmentation. The phonetic-superiority hypothesis predicts that both groups should take advantage of the phonetic richness of longer VOTs (i.e., their enhanced auditory–perceptual robustness). Dutch and Korean listeners learned the words of an artificial language better when word-initial stops had longer VOTs than when they had shorter VOTs. It appears that language-specific phonological knowledge can be overridden by phonetic richness in processing an unfamiliar language. Listeners nonetheless performed better when the stimuli were based on the speech of their native languages, suggesting that the use of richer phonetic information was modulated by listeners' familiarity with the stimuli.

Abstract

We used event-related potentials (ERPs) to investigate the timecourse of interactions between lexical-semantic and sub-lexical visual word-form processing during word recognition. Participants read sentence-embedded pseudowords that orthographically resembled a contextually-supported real word (e.g., “She measured the flour so she could bake a ceke …”) or did not (e.g., “She measured the flour so she could bake a tont …”) along with nonword consonant strings (e.g., “She measured the flour so she could bake a srdt …”). Pseudowords that resembled a contextually-supported real word (“ceke”) elicited an enhanced positivity at 130 msec (P130), relative to real words (e.g., “She measured the flour so she could bake a cake …”). Pseudowords that did not resemble a plausible real word (“tont”) enhanced the N170 component, as did nonword consonant strings (“srdt”). The effect pattern shows that the visual word recognition system is, perhaps counterintuitively, more rapidly sensitive to minor than to flagrant deviations from contextually-predicted inputs. The findings are consistent with rapid interactions between lexical and sub-lexical representations during word recognition, in which rapid lexical access of a contextually-supported word (CAKE) provides top-down excitation of form features (“cake”), highlighting the anomaly of an unexpected word “ceke”.

Abstract

The artificial language learning paradigm was used to investigate to what extent the use of prosodic features is universally applicable or specifically language driven in learning an unfamiliar language, and how nonnative prosodic patterns can be learned. Listeners of unrelated languages—Dutch (n = 100) and Korean (n = 100)—participated. The words to be learned varied with prosodic cues: no prosody, fundamental frequency (F0) rise in initial and final position, final lengthening, and final lengthening plus F0 rise. Both listener groups performed well above chance level with the final lengthening cue, confirming its crosslinguistic use. As for final F0 rise, however, Dutch listeners did not use it until the second exposure session, whereas Korean listeners used it at initial exposure. Neither group used initial F0 rise. On the basis of these results, F0 and durational cues appear to be universal in the sense that they are used across languages for their universally applicable auditory-perceptual saliency, but how they are used is language specific and constrains the use of available prosodic cues in processing a nonnative language. A discussion on how these findings bear on theories of second language (L2) speech perception and learning is provided.

Abstract

The acquisition of the past tense has received substantial attention in the psycholinguistics literature, yet most studies report data from English or closely related Indo-European languages. We report on a past tense elicitation study on 136 4–6-year-old children that were acquiring a highly inflected Finno-Ugric (Uralic) language—Finnish. The children were tested on real and novel verbs (N = 120) exhibiting (1) productive, (2) semi-productive, or (3) non-productive inflectional processes manipulated for frequency and phonological neighbourhood density (PND). We found that Finnish children are sensitive to lemma/base frequency and PND when processing inflected words, suggesting that even though children were using suffixation processes, they were also paying attention to the item level properties of the past tense verbs. This paper contributes to the growing body of research suggesting a single analogical/associative mechanism is sufficient in processing both productive (i.e., regular-like) and non-productive (i.e., irregular-like) words. We argue that seemingly rule-like elements in inflectional morphology are an emergent property of the lexicon.

Abstract

Gestures that spontaneously accompany speech convey information coordinated with the concurrent speech. There has been considerable theoretical disagreement about the process by which this informational coordination is achieved. Some theories predict that the information encoded in gesture is not influenced by how information is verbally expressed. However, others predict that gestures encode only what is encoded in speech. This paper investigates this issue by comparing informational coordination between speech and gesture across different languages. Narratives in Turkish, Japanese, and English were elicited using an animated cartoon as the stimulus. It was found that gestures used to express the same motion events were influenced simultaneously by (1) how features of motion events were expressed in each language, and (2) spatial information in the stimulus that was never verbalized. From this, it is concluded that gestures are generated from spatio-motoric processes that interact on-line with the speech production process. Through the interaction, spatio-motoric information to be expressed is packaged into chunks that are verbalizable within a processing unit for speech formulation. In addition, we propose a model of speech and gesture production as one of a class of frameworks that are compatible with the data.

Abstract

During the last 25 years, second language acquisition (SLA) research hasmade considerable progress, but is still far from proving a solid basis for foreign language teaching, or from a general theory of SLA. In addition, its status within the linguistic disciplines is still very low. I argue this has not much to do with low empirical or theoretical standards in the field—in this regard, SLA research is fully competitive—but with a particular perspective on the acquisition process: SLA researches learners' utterances as deviations from a certain target, instead of genuine manifestations of underlying language capacity; it analyses them in terms of what they are not rather than what they are. For some purposes such a "target deviation perspective" makes sense, but it will not help SLA researchers to substantially and independently contribute to a deeper understanding of the structure and function of the human language faculty. Therefore, these findings will remain of limited interest to other scientists until SLA researchers consider learner varieties a normal, in fact typical, manifestation of this unique human capacity.

Abstract

Starting with Ross (1970), various proposals have been made to classify elliptical coordinations and to characterize different languages according to the types of ellipses which they admit. Sanders (1977) discusses four of these proposals, shows that they are inadequate on various grounds and proposes a fifth typology whose central claim is 'evidently correct', as he states (p. 258). In the following, I shall briefly outline this typology and then show that it is inadequate, too. Since there is only one language 1 know — German — I will take all my examples from this language. Moreover, all examples will be straightforward and easy to be judged.

Abstract

Widespread minority language shift in Early Modern Europe is often ascribed to restrictive language policies and the migration of both majority- and minority-language speakers. However, without a sociohistorically credible account of the mechanisms through which these events caused a language shift, these policies lack explanatory power. Inspired by research on 'language histories from below,' we present an integrated sociohistorical and linguistic account that can shed light on the procresses taking place during a case of language shift in the 17th and 18th centuries. We present and analyze demographic data on the immigration and integration of French speakers in previously Dutch-speaking Dunkirk in this period, showing how moderate intermarriage of immigrants and locals could have represented a motive and a mechanism for language shift against a backdrop of larger language-political processes. We then discuss the modern language-shift dialect of Dunkirk in comparison with different dialects of French. The linguistic data suggests a large influence from the dialects of migrants, underlining their role in the language shift process. The combination of sociohistorical and linguistic evidence gives us a better understanding of language shift in this period, showing the value of an integrated 'from below' approach.

Abstract

Much of human communication and collaboration is predicated on making predictions about others’ actions. Humans frequently use predictions about others’ action mistakes to correct others and spare them mistakes. Such anticipatory correcting reveals a social motivation for unsolicited helping. Cognitively, it requires forward inferences about others’ actions through mental attributions of goal and reality representations. The current study shows that infants spontaneously intervene when an adult is mistaken about the location of an object she is about to retrieve. Infants pointed out a correct location for an adult before she was about to commit a mistake. Infants did not intervene in control conditions when the adult had witnessed the misplacement, or when she did not intend to retrieve the misplaced object. Results suggest that preverbal infants anticipate a person’s mistaken action through mental attributions of both her goal and reality representations, and correct her proactively by spontaneously providing unsolicited information.

Abstract

This study employed a new “anticipatory intervening” paradigm to tease apart false belief and ignorance-based interpretations of 18-month-olds’ helpful informing. We investigated in three experiments whether 18-month-old infants inform an adult selectively about one of the two locations depending on the adult’s belief about which of the two locations held her toy. In experiments 1 and 2, the adult falsely believed that one of the locations held her toy. In experiment 3, the adult was ignorant about which of the two locations held her toy. In all cases, however, the toy had been removed from the locations and the locations contained instead materials which the adult wanted to avoid. In experiments 1 and 2, infants spontaneously and selectively informed the adult about the aversive material in the location the adult falsely believed to hold her toy. In contrast, in experiment 3, infants informed the ignorant adult about both locations equally. Results reveal that infants expected the adult to commit a specific action mistake when she held a false belief, but not when she was ignorant. Further, infants were motivated to intervene proactively. Findings reveal a predictive action-based usage of “theory-of-mind” skills at 18 months of age.

Abstract

The aim of the study was to compare 3- to 8-year-old children’s propensity to antici- pate a comfortable hand posture at the end of a grasping movement ( end-state comfort effect ) between two different object manipulation tasks, the bar-transport task, and the overturned-glass task. In the bar-transport task, participants were asked to insert a verti- cally positioned bar into a small opening of a box. In the overturned-glass task, participants were asked to put an overturned-glass right-side-up on a coaster. Half of the participants experienced action effects (lights) as a consequence of their movements (AE groups), while the other half of the participants did not (No-AE groups). While there was no differ- ence between the AE and No-AE groups, end-state comfort performance differed across age as well as between tasks. Results revealed a significant increase in end-state comfort performance in the bar-transport task from 13% in the 3-year-olds to 94% in the 8-year- olds. Interestingly, the number of children grasping the bar according to end-state comfort doubled from 3 to 4 years and from 4 to 5 years of age. In the overturned-glass task an increase in end-state comfort performance from already 63% in the 3-year-olds to 100% in the 8-year-olds was significant as well. When comparing end-state comfort performance across tasks, results showed that 3- and 4-year-old children were better at manipulating the glass as compared to manipulating the bar, most probably, because children are more familiar with manipulating glasses. Together, these results suggest that preschool years are an important period for the development of motor planning in which the familiarity with the object involved in the task plays a significant role in children’s ability to plan their movements according to end-state comfort.

Abstract

The scope of linguistic planning, i.e., the amount of linguistic information that speakers prepare in advance for an utterance they are about to produce, is highly variable. Distinguishing between possible sources of this variability provides a way to discriminate between production accounts that assume structurally incremental and lexically incremental sentence planning. Two picture-naming experiments evaluated changes in speakers’ planning scope as a function of experience with message structure, sentence structure, and lexical items. On target trials participants produced sentences beginning with two semantically related or unrelated objects in the same complex noun phrase. To manipulate familiarity with sentence structure, target displays were preceded by prime displays that elicited the same or different sentence structures. To manipulate ease of lexical retrieval, target sentences began either with the higher-frequency or lower-frequency member of each semantic pair. The results show that repetition of sentence structure can extend speakers’ scope of planning from one to two words in a complex noun phrase, as indexed by the presence of semantic interference in structurally primed sentences beginning with easily retrievable words. Changes in planning scope tied to experience with phrasal structures favor production accounts assuming structural planning in early sentence formulation.

Abstract

A substantial tradition of linguistic inquiry has framed the knowledge of native speakers in terms of their ability to determine the grammatical acceptability of language forms that they encounter for the first time. In the domain of morphology, the productivity framework of Dressler (CLASNET Working papers 7, 1997) has emphasized the importance of this ability in terms of the graded potentiality of non-existing multimorphemic forms. The goal of this study was to investigate what role the notion of potentiality plays in online lexical well-formedness judgment among children who are native speakers of Austrian German. A total of 114 children between the ages of six and ten and a total of 40 adults between the ages of 18 and 30 (as a comparison group) participated in an online well-formedness judgment task which focused on pluralized German nouns. Concrete, picturable, high frequency German nouns were presented in three pluralized forms: (a) actual existing plural form, (b) morphologically illegal plural form, (c) potential (but not existing) plural form. Participants were shown pictures of the nouns (as a set of three identical items) and simultaneously heard one of three pluralized forms for each noun. Response latency and judgment type served as dependent variables. Results indicate that both children and adults are sensitive to the distinction between illegal and potential forms (neither of which they would have encountered). For all participants, plural frequency (rather than frequency of the singular form) affected responses for both existing and non-existing words. Other factors increasing acceptability were the presence of supplementary umlaut in addition to suffixation and homophony with existing words or word forms.

Abstract

The genetic FOXP2-CNTNAP2 pathway has been shown to be involved in the language capacity. We investigated whether a common variant of CNTNAP2 (rs7794745) is relevant for syntactic and semantic processing in the general population by using a visual sentence processing paradigm while recording ERPs in 49 healthy adults. While both AA homozygotes and T-carriers showed a standard N400 effect to semantic anomalies, the response to subject-verb agreement violations differed across genotype groups. T-carriers displayed an anterior negativity preceding the P600 effect, whereas for the AA group only a P600 effect was observed. These results provide another piece of evidence that the neuronal architecture of the human faculty of language is shaped differently by effects that are genetically determined.

Abstract

It is well-known that, within ERP paradigms of sentence processing, semantically anomalous words elicit N400 effects. Less clear, however, is what happens after the N400. In some cases N400 effects are followed by Late Positive Complexes (LPC), whereas in other cases such effects are lacking. We investigated several factors which could affect the LPC, such as contextual constraint, inter-individual variation and working memory. Seventy-two participants read sentences containing a semantic manipulation (Whipped cream tastes sweet/anxious and creamy). Neither contextual constraint nor working memory correlated with the LPC. Inter-individual variation played a substantial role in the elicitation of the LPC with about half of the participants showing a negative response and the other half showing an LPC. This individual variation correlated with a syntactic ERP as well as an alternative semantic manipulation. In conclusion, our results show that inter-individual variation plays a large role in the elicitation of the LPC and this may account for the diversity in LPC findings in language research.

Abstract

In natural environments, sensory information is embedded in temporally contiguous streams of events. This is typically the case when seeing and listening to a speaker or when engaged in scene analysis. In such contexts, two mechanisms are needed to single out and build a reliable representation of an event (or object): the temporal parsing of information and the selection of relevant information in the stream. It has previously been shown that rhythmic events naturally build temporal expectations that improve sensory processing at predictable points in time. Here, we asked to which extent temporal regularities can improve the detection and identification of events across sensory modalities. To do so, we used a dynamic visual conjunction search task accompanied by auditory cues synchronized or not with the color change of the target (horizontal or vertical bar). Sounds synchronized with the visual target improved search efficiency for temporal rates below 1.4 Hz but did not affect efficiency above that stimulation rate. Desynchronized auditory cues consistently impaired visual search below 3.3 Hz. Our results are interpreted in the context of the Dynamic Attending Theory: specifically, we suggest that a cognitive operation structures events in time irrespective of the sensory modality of input. Our results further support and specify recent neurophysiological findings by showing strong temporal selectivity for audiovisual integration in the auditory-driven improvement of visual search efficiency.

Abstract

In various applications of forensic phonetics the question arises as to how far aural-perceptual speaker recognition performance is reliable. Therefore, it is necessary to examine the relationship between speaker recognition results and human perception/production abilities like musicality or speech sensitivity. In this study, performance in a speaker recognition experiment and a speech sensitivity test are correlated. The results show a moderately significant positive correlation between the two tasks. Generally, performance in the speaker recognition task was better than in the speech sensitivity test. Professionals in speech and singing yielded a more homogeneous correlation than non-experts. Training in speech as well as choir-singing seems to have a positive effect on performance in speaker recognition. It may be concluded, firstly, that in cases where the reliability of voice line-up results or the credibility of a testimony have to be considered, the speech sensitivity test could be a useful indicator. Secondly, the speech sensitivity test might be integrated into the canon of possible procedures for the accreditation of forensic phoneticians. Both tests may also be used in combination.

Abstract

Heterozygous mutations of the human FOXP2 transcription factor gene cause the best-described examples of monogenic speech and language disorders. Acquisition of proficient spoken language involves auditory-guided vocal learning, a specialized form of sensory-motor association learning. The impact of etiological Foxp2 mutations on learning of auditory-motor associations in mammals has not been determined yet. Here, we directly assess this type of learning using a newly developed conditioned avoidance paradigm in a shuttle-box for mice. We show striking deficits in mice heterozygous for either of two different Foxp2 mutations previously implicated in human speech disorders. Both mutations cause delays in acquiring new motor skills. The magnitude of impairments in association learning, however, depends on the nature of the mutation. Mice with a missense mutation in the DNA-binding domain are able to learn, but at a much slower rate than wild type animals, while mice carrying an early nonsense mutation learn very little. These results are consistent with expression of Foxp2 in distributed circuits of the cortex, striatum and cerebellum that are known to play key roles in acquisition of motor skills and sensory-motor association learning, and suggest differing in vivo effects for distinct variants of the Foxp2 protein. Given the importance of such networks for the acquisition of human spoken language, and the fact that similar mutations in human FOXP2 cause problems with speech development, this work opens up a new perspective on the use of mouse models for understanding pathways underlying speech and language disorders.

Abstract

When people see a snake, they are likely to activate both affective information (e.g., dangerous) and non-affective information about its ontological category (e.g., animal). According to the Affective Primacy Hypothesis, the affective information has priority, and its activation can precede identification of the ontological category of a stimulus. Alternatively, according to the Cognitive Primacy Hypothesis, perceivers must know what they are looking at before they can make an affective judgment about it. We propose that neither hypothesis holds at all times. Here we show that the relative speed with which affective and non-affective information gets activated by pictures and words depends upon the contexts in which stimuli are processed. Results illustrate that the question of whether affective information has processing priority over ontological information (or vice versa) is ill posed. Rather than seeking to resolve the debate over Cognitive vs. Affective Primacy in favor of one hypothesis or the other, a more productive goal may be to determine the factors that cause affective information to have processing priority in some circumstances and ontological information in others. Our findings support a view of the mind according to which words and pictures activate different neurocognitive representations every time they are processed, the specifics of which are co-determined by the stimuli themselves and the contexts in which they occur.

Abstract

Disruption of FOXP2, a gene encoding a forkhead-domain transcription factor, causes a severe developmental disorder of verbal communication, involving profound articulation deficits, accompanied by linguistic and grammatical impairments. Investigation of the neural basis of this disorder has been limited previously to neuroimaging of affected children and adults. The discovery of the gene responsible, FOXP2, offers a unique opportunity to explore the relevant neural mechanisms from a molecular perspective. In the present study, we have determined the detailed spatial and temporal expression pattern of FOXP2 mRNA in the developing brain of mouse and human. We find expression in several structures including the cortical plate, basal ganglia, thalamus, inferior olives and cerebellum. These data support a role for FOXP2 in the development of corticostriatal and olivocerebellar circuits involved in motor control. We find intriguing concordance between regions of early expression and later sites of pathology suggested by neuroimaging. Moreover, the homologous pattern of FOXP2/Foxp2 expression in human and mouse argues for a role for this gene in development of motor-related circuits throughout mammalian species. Overall, this study provides support for the hypothesis that impairments in sequencing of movement and procedural learning might be central to the FOXP2-related speech and language disorder.

Abstract

Investigations of left hand praxis in imitation and object use in patients with callosal disconnection have yielded divergent results, inducing a debate between two theoretical positions. Whereas Liepmann suggested that the left hemisphere is motor dominant, others maintain that both hemispheres have equal motor competences and propose that left hand apraxia in patients with callosal disconnection is secondary to left hemispheric specialization for language or other task modalities. The present study aims to gain further insight into the motor competence of the right hemisphere by investigating pantomime of object use in split-brain patients. Three patients with complete callosotomy and, as control groups, five patients with partial callosotomy and nine healthy subjects were examined for their ability to pantomime object use to visual object presentation and demonstrate object manipulation. In each condition, 11 objects were presented to the subjects who pantomimed or demonstrated the object use with either hand. In addition, six object pairs were presented to test bimanual coordination. Two independent raters evaluated the videotaped movement demonstrations. While object use demonstrations were perfect in all three groups, the split-brain patients displayed apraxic errors only with their left hands in the pantomime condition. The movement analysis of concept and execution errors included the examination of ipsilateral versus contralateral motor control. As the right hand/left hemisphere performances demonstrated retrieval of the correct movement concepts, concept errors by the left hand were taken as evidence for right hemisphere control. Several types of execution errors reflected a lack of distal motor control indicating the use of ipsilateral pathways. While one split-brain patient controlled his left hand predominantly by ipsilateral pathways in the pantomime condition, the error profile in the other two split-brain patients suggested that the right hemisphere controlled their left hands. In the object use condition, in all three split-brain patients fine-graded distal movements in the left hand indicated right hemispheric control. Our data show left hand apraxia in split-brain patients is not limited to verbal commands, but also occurs in pantomime to visual presentation of objects. As the demonstration with object in hand was unimpaired in either hand, both hemispheres must contain movement concepts for object use. However, the disconnected right hemisphere is impaired in retrieving the movement concept in response to visual object presentation, presumably because of a deficit in associating perceptual object representation with the movement concepts.

Abstract

Since some patients with right hemisphere damage or with spontaneous callosal disconnection neglect the left half of space, it has been suggested that the left cerebral hemisphere predominantly attends to the right half of space. However, clinical investigations of patients having undergone surgical callosal section have not shown neglect when the hemispheres are tested separately. These observations question the validity of theoretical models that propose a left hemispheric specialisation for attending to the right half of space. The present study aims to investigate neglect and the use of space by either hand in gestural demonstrations in three split-brain patients as compared to five patients with partial callosotomy and 11 healthy subjects. Subjects were asked to demonstrate with precise gestures and without speaking the content of animated scenes with two moving objects. The results show that in the absence of primary perceptual or representational neglect, split-brain patients neglect left personal space in right-handed gestural demonstrations. Since this neglect of left personal space cannot be explained by directional or spatial akinesia, it is suggested that it originates at the conceptual level, where the spatial coordinates for right-hand gestures are planned. The present findings are at odds with the position that the separate left hemisphere possesses adequate mechanisms for acting in both halves of space and neglect results from right hemisphere suppression of this potential. Rather, the results provide support for theoretical models that consider the left hemisphere as specialised for processing the right half of space during the execution of descriptive gestures.