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

Language processing does not take place in isolation from the sensory environment. Listeners are able to recognise spoken words in many different situations, ranging from carefully articulated and noise-free laboratory speech, through casual conversational speech in a quiet room, to degraded conversational speech in a busy train-station. For listeners to be able to recognize speech optimally in each of these listening situations, they must be able to adapt to the constraints of each situation. We investigated this flexibility by comparing the dynamics of the spoken-word recognition process in clear speech and speech disrupted by radio noise. In Experiment 1, Dutch participants listened to clearly articulated spoken Dutch sentences which each included a critical word while their eye movements to four visual objects presented on a computer screen were measured. There were two critical conditions. In the first, the objects included a cohort competitor (e.g., parachute, “parachute”) with the same onset as the critical spoken word (e.g., paraplu, “umbrella”) and three unrelated distractors. In the second condition, a rhyme competitor (e.g., hamer, “hammer”) of the critical word (e.g., kamer, “room”) was present in the display, again with three distractors. To maximize competitor effects pictures of the critical words themselves were not present in the displays on the experimental trials (e.g.,there was no umbrella in the display with the 'paraplu' sentence) and a passive listening task was used (Huettig McQueen, 2007). Experiment 2 was identical to Experiment 1 except that phonemes in the spoken sentences were replaced with radio-signal noises (as in AM radio listening conditions). In each sentence, two,three or four phonemes were replaced with noises. The sentential position of these replacements was unpredictable, but the adjustments were always made to onset phonemes. The critical words (and the immediately surrounding words) were not changed. The question was whether listeners could learn that, under these circumstances, onset information is less reliable. We predicted that participants would look less at the cohort competitors (the initial match to the competitor is less good) and more at the rhyme competitors (the initial mismatch is less bad). We observed a significant experiment by competitor type interaction. In Experiment 1 participants fixated both kinds competitors more than unrelated distractors, but there were more and earlier looks to cohort competitors than to rhyme competitors (Allopenna et al., 1998). In Experiment 2 participants still fixated cohort competitors more than rhyme competitors but the early cohort effect was reduced and the rhyme effect was stronger and occurred earlier. These results suggest that AM radio noise changes the dynamics of spoken word recognition. The well-attested finding of stronger reliance on word onset overlap in speech recognition appears to be due in part to the use of clear speech in most experiments. When onset information becomes less reliable, listeners appear to depend on it less. A core feature of the speech-recognition system thus appears to be its flexibility. Listeners are able to adjust the perceptual weight they assign to different parts of incoming spoken language.