The Nature of Consciousness in the Visually Deprived Brain

Vision plays a central role in how we represent and interact with the world around us. The primacy of vision is structurally imbedded in cortical organization as about one-third of the cortical surface in primates is involved in visual processes. Consequently, the loss of vision, either at birth or later in life, affects brain organization and the way the world is perceived and acted upon. In this paper, we address a number of issues on the nature of consciousness in people deprived of vision. Do brains from sighted and blind individuals differ, and how? How does the brain of someone who has never had any visual perception form an image of the external world? What is the subjective correlate of activity in the visual cortex of a subject who has never seen in life? More in general, what can we learn about the functional development of the human brain in physiological conditions by studying blindness? We discuss findings from animal research as well from recent psychophysical and functional brain imaging studies in sighted and blind individuals that shed some new light on the answers to these questions

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

Neuropsychological and imaging studies have shown that the left supramarginal gyrus (SMG) is specifically involved in processing spatial terms (e.g. above, left of), which locate places and objects in the world. The current fMRI study focused on the nature and specificity of representing spatial language in the left SMG by combining behavioral and neuronal activation data in blind and sighted individuals. Data from the blind provide an elegant way to test the supramodal representation hypothesis, i.e. abstract codes representing spatial relations yielding no activation differences between blind and sighted. Indeed, the left SMG was activated during spatial language processing in both blind and sighted individuals implying a supramodal representation of spatial and other dimensional relations which does not require visual experience to develop. However, in the absence of vision functional reorganization of the visual cortex is known to take place. An important consideration with respect to our finding is the amount of functional reorganization during language processing in our blind participants. Therefore, the participants also performed a verb generation task. We observed that only in the blind occipital areas were activated during covert language generation. Additionally, in the first task there was functional reorganization observed for processing language with a high linguistic load. As the visual cortex was not specifically active for spatial contents in the first task, and no reorganization was observed in the SMG, the latter finding further supports the notion that the left SMG is the main node for a supramodal representation of verbal spatial relations

The role of visual processing in haptic representation - Recognition tasks with novel 3D objects

In perceiving and recognizing everyday objects we use different senses combined together (multisensory process). However, in the past authors concentrated almost completely on vision. However, it is also true that we can touch objects in order to acquire a whole series of information. Moreover, the combination of these two sensory modalities provides complete information about the explored object. So, I first analyzed the available literature on visual and haptic object representation and recognition separately; then, I concentrated on crossmodal visuo-haptic object representation. Finally I exposed and discussed the results obtained with the three experiments I conducted during my Ph.D. studies. These seem to be in line, as already previously proposed by different authors (Newell et al., 2005; Cattaneo et al. 2008; Lacey et al., 2009), with the existence of a supramodal object representation, which is unhooked from the encoding sensory moodality

Brain, images and imagination: how the brain represents the world

The present work aims to describe the main results obtained from the neuroimaging studies on the study of those cognitive processes related to imaging and imagination. A brief excursus on the development of modern neuroimaging techniques presents the methodological background of the many studies. The relationship between sight, blindness and conceptual representation is explored. Research has shown that the ventro-temporal cortex is responsible for recognizing the surrounding environment, to distinguish an object from a face and, in general, objects’ categorization. This area is responsible of imagery in both sighted and blind people, being its morpho-functional organization independent of the visual experience. It follows that a very precise classification of all categories of objects could be obtained in the human brain, and it is supported by a distributed cortical representation independent from the sensorial modality. The last part of the paper presents a series of studies, in which the study of imagery was related to aggressivity. The prefrontal cortex is deactivated when an individual imagines himself becoming aggressive, being this effect more relevant in females than in males. As a conclusion, the neuroscientific approach produced important results in the definition of what imagery is, and showed its relevance to the study of how mind and brain work

Attention shapes our expectations and perceptions: The neural mechanisms of top-down attention during adulthood and development

Top-down attention is the focusing of attention at one\u27s will through knowledge regarding a current task. There is evidence that top-down attention involves the modulation of sensory cortices by higher order regions. However, the mechanisms of top-down attention across sensory modalities, its influence on early sensory inputs, as well as interactions with motivational systems remain unclear. We performed the following set of electrophysiological experiments in typically developed adults and adolescents to examine these areas. 1) The supramodal attentional theory holds that parietally-based attentional mechanisms are shared across sensory modalities. We tested the supramodal theory by examining if lateralized parieto-occipital alpha-band activity, an established metric of top-down spatial attention, was observed in an audiospatial and visuospatial task. In support of the supramodal theory, we observed similar anticipatory alpha-band processes across auditory and visual tasks, but we also found an interaction of supramodal and sensory-specific attentional control processes. 2) There is evidence that top-down attention influences information immediately upon its arrival to sensory cortices, although there is debate in this area. In the current work, volitionally-driven top-down attention was engaged toward one of several overlapping surfaces in an illusion, in which the perceived brightness of the attended surface was enhanced. We observed the attentional enhancement of early visual evoked potentials, indicating that top-down attention shapes the earliest activations in visual cortices. 3) It is well known that motivation impacts attention, but the neural bases of these interactions remain unclear. We examined how level of interest in stimuli influenced top-down spatial attention mechanisms in typically-developing adolescents. Motivation enhanced established attentional processes during the anticipation of high vs. low interest stimuli, but also independently influenced frontal and parieto-occipital activations. These findings provide potential implications to inform clinical measures to improve impaired attentional processes in clinical populations (e.g. individuals with autism spectrum disorders). In sum, these studies revealed the powerful influence of top-down attentional control and its interacting systems on neural activations through several stages of anticipatory and post-stimulus processing during development and adulthood