Are Supramodality and Cross-Modal Plasticity the Yin and Yang of Brain Development? From Blindness to Rehabilitation

Abstract

Research in blind individuals has primarily focused for a long time on the brain plastic reorganization that occurs in early visual areas. Only more recently, scientists have developed innovative strategies to understand to what extent vision is truly a mandatory prerequisite for the brain’s fine morphological architecture to develop and function. As a whole, the studies conducted to date in sighted and congenitally blind individuals have provided ample evidence that several “visual” cortical areas develop independently from visual experience and do process information content regardless of the sensory modality through which a particular stimulus is conveyed: a property named supramodality. At the same time, lack of vision leads to a structural and functional reorganization within “visual” brain areas, a phenomenon known as cross-modal plasticity. Cross-modal recruitment of the occipital cortex in visually deprived individuals represents an adaptative compensatory mechanism that mediates processing of non-visual inputs. Supramodality and cross-modal plasticity appears to be the “yin and yang” of brain development: supramodal is what takes place despite the lack of vision, whereas cross-modal is what happens because of lack of vision. Here we provide a critical overview of the research in this field and discuss the implications that these novel findings have for the development of educative/rehabilitation approaches and sensory substitution devices (SSDs) in sensory-impaired individuals.

Recruitment of the occipital cortex by arithmetic processing follows computational bias in the congenitally blind

“…Previous studies have found that the "visual" cortex of CB people responds to a variety of auditory (Collignon et al, 2009;Gougoux et al, 2005;Ricciardi et al, 2014;Weeks et al, 2000) and tactile tasks (Büchel et al, 1998;Sadato et al, 1996). Several studies have shown that such a phenomenon follows the functional specialization of the colonized brain regions (Amedi et al, 2017;Bi et al, 2016;Cecchetti et al, 2016;Dormal and Collignon, 2011;Heimler et al, 2015). However, the observation that the occipital cortex of the CB also activates during higher cognitive operations considered distant from visual functions, such as arithmetic processing (Kanjlia et al, 2016), was used to challenge the idea that an intrinsic computational bias is a generic principle guiding the recruitment of the occipital cortex and that, in contrast, occipital regions are pluripotent early in development and able to engage in a vast array of cognitive functions that Brain activations significant (pcorr < .05 FWE) after correction over (*) small spherical volumes (SVC, 10 mm radius).…”

Visual imagery and visual perception induce similar changes in occipital slow waves of sleep

“…For instance, Lazzouni and colleagues (Lazzouni et al, 2012) reported that 6 h of visual deprivation led to clear changes in the (cross-modal) responsiveness of occipital areas to auditory stimuli in only half of participants. Along the same lines, these results may also have implications for our understanding of behavioral and functional heterogeneities in late blind individuals (Cattaneo et al, 2008;Cecchetti et al, 2016).…”

Distinctive interaction between cognitive networks and the visual cortex in early blind individuals

“…According to the metamodal/supramodal theory, the cortex is organized into task operators that are indifferent to sensory modality (Pascual-Leone and Hamilton 2001; Pietrini et al 2004). Hence, in the case of visual deprivation, auditory and tactile input to the visual cortex would be unmasked, leading to its involvement in non-visual perception (Cecchetti et al 2016). With the prediction that the same computations are carried out even in blindness, this theory cannot explain the drastic change from low-level visual processing to high-level non-perceptual computations.…”