Reduced Left Lateralization of Language in Congenitally Blind Individuals.

Language processing depends on a left-lateralized network of frontotemporal cortical regions. This network is remarkably consistent across individuals and cultures. However, there is also evidence that developmental factors, such as delayed exposure to language, can modify this network. Recently, it has been found that, in congenitally blind individuals, the typical frontotemporal language network expands to include parts of "visual" cortices. Here, we report that blindness is also associated with reduced left lateralization in frontotemporal language areas. We analyzed fMRI data from two samples of congenitally blind adults (n = 19 and n = 13) and one sample of congenitally blind children (n = 20). Laterality indices were computed for sentence comprehension relative to three different control conditions: solving math equations (Experiment 1), a memory task with nonwords (Experiment 2), and a "does this come next?" task with music (Experiment 3). Across experiments and participant samples, the frontotemporal language network was less left-lateralized in congenitally blind than in sighted individuals. Reduction in left lateralization was not related to Braille reading ability or amount of occipital plasticity. Notably, we observed a positive correlation between the lateralization of frontotemporal cortex and that of language-responsive occipital areas in blind individuals. Blind individuals with right-lateralized language responses in frontotemporal cortices also had right-lateralized occipital responses to language. Together, these results reveal a modified neurobiology of language in blindness. Our findings suggest that, despite its usual consistency across people, the neurobiology of language can be modified by nonlinguistic experiences.

"Visual" Cortex of Congenitally Blind Adults Responds to Syntactic Movement.

Human cortex is comprised of specialized networks that support functions, such as visual motion perception and language processing. How do genes and experience contribute to this specialization? Studies of plasticity offer unique insights into this question. In congenitally blind individuals, "visual" cortex responds to auditory and tactile stimuli. Remarkably, recent evidence suggests that occipital areas participate in language processing. We asked whether in blindness, occipital cortices: (1) develop domain-specific responses to language and (2) respond to a highly specialized aspect of language-syntactic movement. Nineteen congenitally blind and 18 sighted participants took part in two fMRI experiments. We report that in congenitally blind individuals, but not in sighted controls, "visual" cortex is more active during sentence comprehension than during a sequence memory task with nonwords, or a symbolic math task. This suggests that areas of occipital cortex become selective for language, relative to other similar higher-cognitive tasks. Crucially, we find that these occipital areas respond more to sentences with syntactic movement but do not respond to the difficulty of math equations. We conclude that regions within the visual cortex of blind adults are involved in syntactic processing. Our findings suggest that the cognitive function of human cortical areas is largely determined by input during development. SIGNIFICANCE STATEMENT: Human cortex is made up of specialized regions that perform different functions, such as visual motion perception and language processing. How do genes and experience contribute to this specialization? Studies of plasticity show that cortical areas can change function from one sensory modality to another. Here we demonstrate that input during development can alter cortical function even more dramatically. In blindness a subset of "visual" areas becomes specialized for language processing. Crucially, we find that the same "visual" areas respond to a highly specialized and uniquely human aspect of language-syntactic movement. These data suggest that human cortex has broad functional capacity during development, and input plays a major role in determining functional specialization.

Enhanced performance on a sentence comprehension task in congenitally blind adults.

People born blind habitually experience linguistic utterances in the absence of visual cues and activate "visual" cortices during sentence comprehension. Do blind individuals show superior performance on sentence processing tasks? Congenitally blind (n=25) and age and education matched sighted (n=52) participants answered yes/no who-did-what-to-whom questions for auditorily-presented sentences, some of which contained a grammatical complexity manipulation (long-distance movement dependency or garden path). Short-term memory was measured with a forward and backward letter-spans. A battery of control tasks included two speeded math tasks and vocabulary and reading tasks from Woodcock Johnson III. The blind group outperformed the sighted on the sentence comprehension task, particularly for garden-path sentences, and on short-term memory span tasks, but performed similar to the sighted on control tasks. Sentence comprehension performance was not correlated with span performance, suggesting independent enhancements.

Syntactic Creativity Errors in Children's Wh-Questions.

Previous work has reported that children creatively make syntactic errors that are ungrammatical in their target language, but are grammatical in another language. One of the most well-known examples is medial wh-question errors in English-speaking children's wh-questions (e.g., What do you think who the cat chased? from Thornton, 1990). The evidence for this non-target-like structure in both production and comprehension has been taken to support the existence of innate, syntactic parameters that define all possible grammatical variation, which serve as a top-down constraint guiding children's language acquisition process. The present study reports new story-based production and comprehension experiments that challenge this interpretation. While we replicated previous observations of medial wh-question errors in children's sentence production (Experiment 1), we saw a reduction in evidence indicating that English-speaking children assign interpretations that conform to the medial wh-question pattern (Experiment 2). Crucially, we found no correlation between production and comprehension errors (Experiment 3). We suggest that these errors are the result of children's immature sentence production mechanisms rather than immature grammatical knowledge.

Developing incrementality in filler-gap dependency processing.

Much work has demonstrated that children are able to use bottom-up linguistic cues to incrementally interpret sentences, but there is little understanding of the extent to which children's comprehension mechanisms are guided by top-down linguistic information that can be learned from distributional regularities in the input. Using a visual world eye tracking experiment and a corpus analysis, the current study investigates whether 5- and 6-year-old children incrementally assign interpretations to temporarily ambiguous wh-questions like What was Emily eating the cake with __? In the visual world eye-tracking experiment, adults demonstrated evidence for active dependency formation at the earliest region (i.e., the verb region), while 6-year-old children demonstrated a spill-over effect of this bias in the subsequent NP region. No evidence for this bias was found in 5-year-olds, although the speed of arrival at the ultimately correct instrument interpretation appears to be modulated by the vocabulary size. These results suggest that adult-like active formation of filler-gap dependencies begins to emerge around age 6. The corpus analysis of filler-gap dependency structures in adult corpora and child corpora demonstrate that the distributional regularities in either corpora are equally in favor of early, incremental completion of filler-gap dependencies, suggesting that the distributional information in the input is either not relevant to this incremental bias, or that 5-year-old children are somehow unable to recruit this information in real-time comprehension. Taken together, these findings shed light on the origin of the incremental processing bias in filler-gap dependency processing, as well as on the role of language experience and cognitive constraints in the development of incremental sentence processing mechanisms.

Developmental changes in misinterpretation of garden-path wh-questions in French.

This study explores (mis)interpretation of biclausal wh-questions by French-speaking adults and children, aiming to investigate cross-linguistic differences in sentence revision mechanisms. Following previous work in Japanese the ambiguity of wh-questions was manipulated: In ambiguous questions, the fronted wh-phrase could be associated with the first, main-clause verb or the second, embedded-clause verb, while in garden-path questions, an inserted filled-gap prepositional phrase (PP) blocked main-clause attachment. Importantly, French differs from Japanese in that the filled gap arises after the first verb-that is, after the wh-phrase has been interpreted within the main clause. Two story-based comprehension experiments were conducted to probe the effect of word order on revision performance. Adults and children frequently provided main-clause interpretations of ambiguous questions. In filled-gap questions, children displayed relatively acute sensitivity to the filled-gap in wh-argument questions (Experiment 2), but not in wh-adjunct questions (Experiment 1); adults showed surprisingly low sensitivity to it, frequently misinterpreting adjunct and argument questions. Acceptability ratings (Experiment 3) showed that adults systematically prefer in situ questions over wh-fronting questions. We conclude that timing of the error signal influences revision, and that whereas French-speaking children prioritize syntactic cues, adults prioritize distributional information about the optionality of wh-fronting in French.

Similarity of wh-Phrases and Acceptability Variation in wh-Islands.

In wh-questions that form a syntactic dependency between the fronted wh-phrase and its thematic position, acceptability is severely degraded when the dependency crosses another wh-phrase. It is well known that the acceptability degradation in wh-island violation ameliorates in certain contexts, but the source of this variation remains poorly understood. In the syntax literature, an influential theory - Featural Relativized Minimality - has argued that the wh-island effect is modulated exclusively by the distinctness of morpho-syntactic features in the two wh-phrases, but psycholinguistic theories of memory encoding and retrieval mechanisms predict that semantic properties of wh-phrases should also contribute to wh-island amelioration. We report four acceptability judgment experiments that systematically investigate the role of morpho-syntactic and semantic features in wh-island violations. The results indicate that the distribution of wh-island amelioration is best explained by an account that incorporates the distinctness of morpho-syntactic features as well as the semantic denotation of the wh-phrases. We argue that an integration of syntactic theories and perspectives from psycholinguistics can enrich our understanding of acceptability variation in wh-dependencies.

Hyper-active gap filling.

Much work has demonstrated that speakers of verb-final languages are able to construct rich syntactic representations in advance of verb information. This may reflect general architectural properties of the language processor, or it may only reflect a language-specific adaptation to the demands of verb-finality. The present study addresses this issue by examining whether speakers of a verb-medial language (English) wait to consult verb transitivity information before constructing filler-gap dependencies, where internal arguments are fronted and hence precede the verb. This configuration makes it possible to investigate whether the parser actively makes representational commitments on the gap position before verb transitivity information becomes available. A key prediction of the view that rich pre-verbal structure building is a general architectural property is that speakers of verb-medial languages should predictively construct dependencies in advance of verb transitivity information, and therefore that disruption should be observed when the verb has intransitive subcategorization frames that are incompatible with the predicted structure. In three reading experiments (self-paced and eye-tracking) that manipulated verb transitivity, we found evidence for reading disruption when the verb was intransitive, although no such reading difficulty was observed when the critical verb was embedded inside a syntactic island structure, which blocks filler-gap dependency completion. These results are consistent with the hypothesis that in English, as in verb-final languages, information from preverbal noun phrases is sufficient to trigger active dependency completion without having access to verb transitivity information.