Visual Cortex Activation in Bilingual Blind Individuals during Use of Native and Second Language

Abstract

Recent neuroimaging and transcranial magnetic stimulation studies indicate that the occipital cortex of congenitally blind humans is functionally relevant for nonvisual tasks. There are suggestions that the underlying cortical reorganization is restricted by a critical period. These results were based on comparison between early and late blind groups, thereby facing the problem of great variability among individuals within each group. Using functional magnetic resonance imaging, we studied bilingual congenitally blind individuals during use of 2 languages: one acquired early (Hebrew), the other later in life (English, at approximately 10 years). The subjects listened to chimeric words consisting of superimposed Hebrew and English nouns. They were instructed to either covertly generate a verb to the heard noun or repeat the noun, in either Hebrew or English. Lateralized activation during verb generation (vs. repeat) was found in classical language areas, in congruence with previous studies in sighted subjects. Critically, in our study, the blind participants typically also had robust left lateralized occipital differential activation during verb generation (vs. repeat), in both languages. This suggests that the critical period for plasticity persists beyond 10 years or that the visual cortex of the blind might be engaged in abstract levels of language processing, common to the 2 languages.

“To see or not to see: that is the question.” The “Protection-Against-Schizophrenia” (PaSZ) model: evidence from congenital blindness and visuo-cognitive aberrations

“…In fact, there may be a specific critical period during which neurofunctional plasticity to sensory loss is maximal (Sathian, 2005). Until now, the duration of that time window has been unclear, but it has been proposed to be between 10 and 14 years for visual information processing (Cohen et al, 1999; Ofan and Zohary, 2007), implying that this may be a critical period for cortical changes regarding the protection and development of schizophrenia as well. Although changes in cortical functioning might not occur until several years after sensory deprivation (Cattaneo et al, 2008), the overall evidence implies that ontogenetic development must occur to establish the multi-sensory integration interferences observed in sighted individuals.…”

“…The fact that functional reorganization due to sensory deprivation is age-specific is important for all vision trainings (Cohen et al, 1999; Sathian, 2005; Ofan and Zohary, 2007; Cattaneo et al, 2008). For example, independent of sensory input or visual experience, certain brain areas maintain stimulus selectivity (Striem-Amit et al, 2012b), indicating that the human brain has intrinsic constraints with regard to functional plasticity (Striem-Amit et al, 2012d).…”

“…Note that the model does not make a concrete assumption on the association between vision capacity and risk for schizophrenia (linear, exponential, etc.). Instead, we suggest that extensive longitudinal and epidemiological investigations, also controlling for age-related visual capacity decline (Ofan and Zohary, 2007; Cattaneo et al, 2008), are necessary to elaborate this issue. In this context, visual capacity may comprise but is not limited to measures of visual acuity (near/far), sensitivity to light, motion, and color, visual field size, and stereoscopic vision.…”

Visual Motion Area MT+/V5 Responds to Auditory Motion in Human Sight-Recovery Subjects

“…Some studies report that in blind subjects, early visual areas are recruited to serve verbal and memory functions that do not clearly map onto to the known function of the visual cortex (Burton et al, 2002b;Amedi et al, 2003;Raz et al, 2005;Ofan and Zohary, 2007). In these cases, cross-modal plasticity could potentially lead to competition between the acquired function and any later restored visual function.…”

Spatial Language Processing in the Blind: Evidence for a Supramodal Representation and Cortical Reorganization

“…This constitutes further evidence of reorganization of the occipital cortex and adds to the established body of literature on reorganization. There is an increasing amount of evidence that the reorganization of the occipital cortex is functionally relevant and involved in the processing of language processing, Braille reading, spatial imagery and tactile discrimination [24], [30], [38], [39], [44], [61], [78], [79].…”