“Visual” Cortex of Congenitally Blind Adults Responds to Syntactic Movement

Abstract

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.

Reduced Left Lateralization of Language in Congenitally Blind Individuals

“…The questions required participants to attend to the thematic relations in the sentence (i.e., who did what to whom). Half of the sentences contained a syntactic movement dependency, making them more syntactically complex (Lane et al, 2015). The syntactic complexity manipulation is not analyzed here.…”

“…Both contrasts have been used in previous studies and are known to elicit canonical perisylvian responses (e.g., Monti, Parsons, & Osherson, 2012;Fedorenko, Hsieh, Nieto-Castañón, Whitfield-Gabrieli, & Kanwisher, 2010;Humphries, Binder, Medler, & Liebenthal, 2006;Friederici, Meyer, & von Cramon, 2000;Hagoort et al, 1999). The control conditions in Experiments 1 and 2 were high in working memory load so as to distinguish linguistic processes from general working memory and task difficulty effects (Lane et al, 2015). The stories > music contrast in Experiment 3 includes phonological as well as lexical and sentence level processes.…”

“…Across Experiments 1-3, there were no consistent differences, between blind and sighted participants in sentence comprehension performance. Behavioral performance in Experiments 1 and 2 has been described previously (Lane et al, 2015). In Experiment 3, all adult participants performed at ceiling (mean accuracy > 98% for both blind and sighted adults, (14) 96 (11) 4.59 (0.81) 3.69 (0.9)…”

“…Furthermore, the response profile of frontotemporal regions across conditions is similar between blind and sighted individuals. For example, in both groups, frontotemporal areas show greater responses to sentences that are grammatically complex (Lane et al, 2015;. Blind and sighted individuals also activate a similar middle temporal gyrus region during verb processing (Bedny et al, 2011).…”

“…"Visual" cortex language areas are sensitive to manipulations of grammatical complexity. Visual cortices of blind individuals respond more to sentences with syntactic movement than to matched sentences without syntactic movement (Lane, Kanjlia, Omaki, & Bedny, 2015;. There is also some evidence that occipital activity during language tasks is relevant to behavior.…”