Presentations

Abstract

Serial naming deficits have been identified as core symptoms of developmental dyslexia. A prominent hypothesis is that naming delays are due to inefficient phonological encoding, yet the exact nature of this underlying impairment remains largely underspecified. Here we used recordings of eye movements and word onset latencies to examine at what processing level the dyslexic naming deficit emerges: localized at an early stage of lexical encoding or rather later at the level of phonetic or motor planning. 23 dyslexic and 25 control adult readers were tested on a serial object naming task for 30 items and an analogous reading task, where phonological neighborhood density and word-frequency were manipulated. Results showed that both word properties influenced early stages of phonological activation (first fixation and first-pass duration) equally in both groups of participants. Moreover, in the control group any difficulty appeared to be resolved early in the reading process, while for dyslexic readers a processing disadvantage for low-frequency words and for words with sparse neighborhood also emerged in a measure that included late stages of output planning (eye-voice span). Thus, our findings suggest suboptimal phonetic and/or articulatory planning in dyslexia.

Abstract

Reading functions beyond early visual precessing are known to be lateralized to the left hemisphere, but how left-lateralization arises during literacy acquisition is an open question. Bilateral processing or rightward asymmetries have previously been associated with developmental dyslexia. However, it is unclear at present to what extent this lack of left-lateralization reflects differences in reading ability. In this study, a group of illiterate adults in rural India (N=29) participated in a literacy training program over the course of six months. fMRI measures were obtained before and after training on a number of different visual stimulus categories, including written sentences, false fonts, and object categories such as houses and faces. This training group was matched on demographic and socioeconomic variables to an illiterate no-training group and to low- and highly-literate control groups, who were also scanned twice but received no training (total N=90). In a cross-sectional analysis before training, reading ability was positively correlated with increased BOLD responses in a left-lateralized network including the dorsal and ventral visual streams for text and false fonts, but not for other types of visual stimuli. A longitudinal analysis of learning effects in the training group showed that beginning readers engage bilateral networks more than proficient readers. Lateralization of BOLD responses was further examined by calculating laterality indices in specific regions. We observed training-related changes in lateralization for processing written stimuli in a number of subregions in the dorsal and ventral visual streams, as well as in the cerebellum. Together with the cross-sectional results, these data suggest a causal relationship between reading ability and the degree of hemispheric asymmetry in processing written materials.

Abstract

Reading functions beyond early visual precessing are known to be lateralized to the left hemisphere, but how left-lateralization arises during literacy acquisition is an open question. Bilateral processing or rightward asymmetries have previously been associated with developmental dyslexia. However, it is unclear at present to what extent this lack of left-lateralization reflects differences in reading ability. In this study, a group of illiterate adults in rural India (N=29) participated in a literacy training program over the course of six months. fMRI measures were obtained before and after training on a number of different visual stimulus categories, including written sentences, false fonts, and object categories such as houses and faces. This training group was matched on demographic and socioeconomic variables to an illiterate no-training group and to low- and highly-literate control groups, who were also scanned twice but received no training (total N=90). In a cross-sectional analysis before training, reading ability was positively correlated with increased BOLD responses in a left-lateralized network including the dorsal and ventral visual streams for text and false fonts, but not for other types of visual stimuli. A longitudinal analysis of learning effects in the training group showed that beginning readers engage bilateral networks more than proficient readers. Lateralization of BOLD responses was further examined by calculating laterality indices in specific regions. We observed training-related changes in lateralization for processing written stimuli in a number of subregions in the dorsal and ventral visual streams, as well as in the cerebellum. Together with the cross-sectional results, these data suggest a causal relationship between reading ability and the degree of hemispheric asymmetry in processing written materials.

Abstract

Many psycholinguistic experiments suggest that prediction is an important characteristic of language processing. Some recent theoretical accounts in the cognitive sciences (e.g., Clark, 2013; Friston, 2010) and psycholinguistics (e.g., Dell & Chang, 2014) appear to suggest that prediction is even necessary to understand language. I will evaluate this proposal. I will first discuss several arguments that may appear to be in line with the notion that prediction is necessary for language processing. These arguments include that prediction provides a unified theoretical principle of the human mind and that it pervades cortical function. We discuss whether evidence of human abilities to detect statistical regularities is necessarily evidence for predictive processing and evaluate suggestions that prediction is necessary for language learning. Five arguments are then presented that question the claim that all language processing is predictive in nature. I point out that not all language users appear to predict language and that suboptimal input makes prediction often very challenging. Prediction, moreover, is strongly context-dependent and impeded by resource limitations. I will also argue that it may be problematic that most experimental evidence for predictive language processing comes from 'prediction-encouraging' experimental set-ups. Finally, I will discuss possible ways that may lead to a further resolution of this debate. We conclude that languages can be learned and understood in the absence of prediction. Claims that all language processing is predictive in nature are premature.

Abstract

How do human cultural inventions such as reading result in neural re-organization? In this first longitudinal study with young completely illiterate adult participants, we measured brain responses to speech, text, and other categories of visual stimuli with fMRI before and after a group of illiterate participants in India completed a literacy training program in which they learned to read and write Devanagari script. A literate and an illiterate no-training control group were matched to the training group in terms of socioeconomic background and were recruited from the same societal community in two villages of a rural area near Lucknow, India. This design permitted investigating effects of literacy cross-sectionally across groups before training (N=86) as well as longitudinally (training group N=25). The two analysis approaches yielded converging results: Literacy was associated with enhanced, left-lateralized responses to written text along the ventral stream (including lingual gyrus, fusiform gyrus, and parahippocampal gyrus), dorsal stream (intraparietal sulcus), and (pre-) motor systems (pre-central sulcus, supplementary motor area) and thalamus (pulvinar). Significantly reduced responses were observed bilaterally in the superior parietal lobe (precuneus) and in the right angular gyrus. These effects corroborate and extend previous findings from cross-sectional studies. However, effects of literacy were specific to written text and (to a lesser extent) to false fonts. We did not find any evidence for effects of literacy on responses in the auditory cortex in our Hindi-speaking participants. This raises questions about the extent to which phonological representations are altered by literacy acquisition.

Abstract

We conceptualize objects based on sensory and motor information gleaned from real-world experience. But to what extent is such conceptual information structured according to higher level linguistic features too? Here we investigate whether classifiers, a grammatical category, shape the conceptual representations of objects. In three experiments native Mandarin speakers (speakers of a classifier language) and native Dutch speakers (speakers of a language without classifiers) judged the similarity of a target object (presented as a word or picture) with four objects (presented as words or pictures). One object shared a classifier with the target, the other objects did not, serving as distractors. Across all experiments, participants judged the target object as more similar to the object with the shared classifier than distractor objects. This effect was seen in both Dutch and Mandarin speakers, and there was no difference between the two languages. Thus, even speakers of a non-classifier language are sensitive to object similarities underlying classifier systems, and using a classifier system does not exaggerate these similarities. This suggests that classifier systems simply reflect, rather than affect, conceptual structure.

Abstract

How do human cultural inventions such as reading result in neural re-organization? Previous cross-sectional studies have reported extensive effects of literacy on the neural systems for vision and language (Dehaene et al [2010, Science], Castro-Caldas et al [1998, Brain], Petersson et al [1998, NeuroImage], Carreiras et al [2009, Nature]). In this first longitudinal study with completely illiterate participants, we measured brain responses to speech, text, and other categories of visual stimuli with fMRI before and after a group of illiterate participants in India completed a literacy training program in which they learned to read and write Devanagari script. A literate and an illiterate no-training control group were matched to the training group in terms of socioeconomic background and were recruited from the same societal community in two villages of a rural area near Lucknow, India. This design permitted investigating effects of literacy cross-sectionally across groups before training (N=86) as well as longitudinally (training group N=25). The two analysis approaches yielded converging results: Literacy was associated with enhanced, mainly left-lateralized responses to written text along the ventral stream (including lingual gyrus, fusiform gyrus, and parahippocampal gyrus), dorsal stream (intraparietal sulcus), and (pre-) motor systems (pre-central sulcus, supplementary motor area), thalamus (pulvinar), and cerebellum. Significantly reduced responses were observed bilaterally in the superior parietal lobe (precuneus) and in the right angular gyrus. These positive effects corroborate and extend previous findings from cross-sectional studies. However, effects of literacy were specific to written text and (to a lesser extent) to false fonts. Contrary to previous research, we found no direct evidence of literacy affecting the processing of other types of visual stimuli such as faces, tools, houses, and checkerboards. Furthermore, unlike in some previous studies, we did not find any evidence for effects of literacy on responses in the auditory cortex in our Hindi-speaking participants. We conclude that learning to read has a specific and extensive effect on the processing of written text along the visual pathways, including low-level thalamic nuclei, high-level systems in the intraparietal sulcus and the fusiform gyrus, and motor areas. The absence of an effect of literacy on responses in the auditory cortex in particular raises questions about the extent to which phonological representations in the auditory cortex are altered by literacy acquisition or recruited online during reading.

Abstract

To what extent is visual attention driven by the semantics of individual objects, rather than by their visual appearance? To investigate this we continuously measured eye movements, while observers searched through displays of common objects for an aurally instructed target. On crucial trials, the target was absent, but the display contained object s that were either semantically or visually related to the target. We hypothesized that timing is crucial in the occurrence and strength of semantic influences on visual orienting, and therefore presented the target instruction either before, during, or af ter (memory - based search) picture onset. When the target instruction was presented before picture onset we found a substantial, but delayed bias in orienting towards semantically related objects as compared to visually related objects. However, this delay disappeared when the visual information was presented before the target instruction. Furthermore, the temporal dynamics of the semantic bias did not change in the absence of visual competition. These results po int to cascadic but independent influences of semantic and visual representations on attention. In addition. the results of the memory - based search studies suggest that visual and semantic biases only arise when the visual stimuli are present. Although we consistent ly found that people fixate at locat ions previously occupied by the target object (a replication of earlier findings), we did not find such biases for visually or semantically related objects. Overall, our studies show that the question whether visual orienting is driven by semantic c ontent is better rephrased as when visual orienting is driven by semantic content.

Abstract

I will discuss recent research with illiterates and individuals with dyslexia which suggests that many cognitive ‚defi ciencies‘ proposed as possible causes of dyslexia are simply a consequence of decreased reading experience. I will argue that in order to make further progress towards an understanding of the causes of dyslexia it is necessary to appropriately distinguish between cause and effect.

Abstract

How do human cultural inventions such as reading result in neural re-organization? In this first longitudinal study with young completely illiterate adult participants, we measured brain responses to speech, text, and other categories of visual stimuli with fMRI before and after a group of illiterate participants in India completed a literacy training program in which they learned to read and write Devanagari script. A literate and an illiterate no-training control group were matched to the training group in terms of socioeconomic background and were recruited from the same societal community in two villages of a rural area near Lucknow, India. This design permitted investigating effects of literacy cross-sectionally across groups before training (N=86) as well as longitudinally (training group N=25). The two analysis approaches yielded converging results: Literacy was associated with enhanced, left-lateralized responses to written text along the ventral stream (including lingual gyrus, fusiform gyrus, and parahippocampal gyrus), dorsal stream (intraparietal sulcus), and (pre-) motor systems (pre-central sulcus, supplementary motor area) and thalamus (pulvinar). Significantly reduced responses were observed bilaterally in the superior parietal lobe (precuneus) and in the right angular gyrus. These effects corroborate and extend previous findings from cross-sectional studies. However, effects of literacy were specific to written text and (to a lesser extent) to false fonts. We did not find any evidence for effects of literacy on responses in the auditory cortex in our Hindi-speaking participants. This raises questions about the extent to which phonological representations are altered by literacy acquisition.

Abstract

How do human
cultural
inventions
such as reading
result
in neural
re-organization?
In this first longitudinal
study
with young
completely
illiterate
adult
participants,
we measured
brain
responses
to speech,
text, and other
categories
of visual
stimuli
with fMRI
before
and after a group
of
illiterate
participants
in India
completed
a literacy
training
program
in which
they learned
to read and write
Devanagari
script.
A literate
and an illiterate
no-training
control
group
were
matched
to the
training
group
in terms
of socioeconomic
background
and were
recruited
from
the same
societal
community
in two villages
of a
rural area near Lucknow,
India.
This design
permitted
investigating
effects
of literacy
cross-sectionally
across
groups
before
training
(N=86)
as well as longitudinally
(training
group
N=25).
The two
analysis
approaches
yielded
converging
results:
Literacy
was
associated
with enhanced,
left-lateralized
responses
to written
text
along
the ventral
stream
(including
lingual
gyrus,
fusiform
gyrus,
and parahippocampal
gyrus),
dorsal
stream
(intraparietal
sulcus),
and (pre-)
motor
systems
(pre-central
sulcus,
supplementary
motor
area)
and thalamus
(pulvinar).
Significantly
reduced
responses
were observed
bilaterally
in the superior
parietal
lobe (precuneus)
and in the right angular
gyrus.
These
effects
corroborate
and extend
previous
findings
from
cross-sectional
studies.
However,
effects
of literacy
were
specific
to written
text and (to a lesser
extent)
to
false fonts.
We did not find any evidence
for effects
of literacy
on
responses
in the auditory
cortex
in our Hindi-speaking
participants.
This
raises
questions
about
the extent
to which
phonological
representations are altered by literacy acquisition.

Abstract

If a Mandarin speaker had walked past two rivers and wished to describe how many he had seen, he would have to say “two tiao river”, where tiao designates long, rope-like objects such as rivers, snakes and legs. Tiao is one of several hundred classifiers – a grammatical category in Mandarin. In two eye-tracking studies we presented Mandarin speakers with simple Mandarin sentences through headphones while monitoring their eye-movements to objects presented on a computer monitor. The crucial question is what participants look at while listening to a pre-specified target noun. If classifier categories influence general conceptual processing then on hearing the target noun participants should look at objects that are also members of the same classifier category – even when the classifier is not explicitly present. For example, on hearing scissors, Mandarin speakers should look more at a picture of a chair than at an unrelated object because scissors and chair share the classifier ba. This would be consistent with a Strong Whorfian position, according to which language is a major determinant in shaping conceptual thought (Sapir, 1921; Whorf, 1956). A weaker influence of language-on-thought could be predicted, where language shapes cognitive processing, but only when the language-specific category is actively being processed (Slobin, 1996). According to this account, eye-movements are not necessarily drawn to chair when a participant hears scissors, but they would be on hearing ba scissors. This is because hearing ba activates the linguistic category that both scissors and chair belong to. A third logical possibility is that classifiers are purely formal markers (cf. Greenberg, 1972; Lehman, 1979) that do not influence attentional processing even when they are explicitly present. The data showed that when participants heard a spoken word from the same classifier category as a visually depicted object (e.g. scissors-chair), but the classifier was not explicitly presented in the speech, overt attention to classifier-match objects (e.g. chair) and distractor objects did not differ (Experiment 1). But when the classifier was explicitly presented (e.g. ba, Experiment 2), participants shifted overt attention significantly more to classifier-match objects (e.g. chair) than to distractors. These data are incompatible with the Strong Whorfian hypothesis. Instead the findings support the Weak Whorfian hypothesis that linguistic distinctions force attention to properties of the world but only during active linguistic processing of that distinction (cf. Slobin, 1996).