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The nature of consciousness in the visually deprived brain.

Kupers R, Pietrini P, Ricciardi E, Ptito M - Front Psychol (2011)

Bottom Line: 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?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.

View Article: PubMed Central - PubMed

Affiliation: Institute of Neuroscience and Pharmacology, Panum Institute, University of Copenhagen Copenhagen, Denmark.

ABSTRACT
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.

No MeSH data available.


Related in: MedlinePlus

Anatomical and metabolic changes in the congenitally blind brain. (A) Axial brain slices showing reductions in gray (red) and white matter (blue) in congenitally blind compared to matched sighted control subjects. All components of the visual system in the blind are reduced in volume (after Ptito et al., 2008b). (B) Differences in cortical thickness between congenitally blind and sighted control subjects. Despite a reduction in volume of the occipital cortex, cortical thickness of the cuneus is increased in congenitally blind subjects (unpublished data from our lab). (C) Mid-sagittal brain slices showing increased resting-state glucose metabolism in the congenitally blind brain. Illustrative examples of cerebral glucose metabolism in a congenitally blind (left) and a normal sighted control (right) subject (Kupers et al., 2009).
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Figure 2: Anatomical and metabolic changes in the congenitally blind brain. (A) Axial brain slices showing reductions in gray (red) and white matter (blue) in congenitally blind compared to matched sighted control subjects. All components of the visual system in the blind are reduced in volume (after Ptito et al., 2008b). (B) Differences in cortical thickness between congenitally blind and sighted control subjects. Despite a reduction in volume of the occipital cortex, cortical thickness of the cuneus is increased in congenitally blind subjects (unpublished data from our lab). (C) Mid-sagittal brain slices showing increased resting-state glucose metabolism in the congenitally blind brain. Illustrative examples of cerebral glucose metabolism in a congenitally blind (left) and a normal sighted control (right) subject (Kupers et al., 2009).

Mentions: The results of VBM studies have revealed a significant gray matter atrophy of all brain structures of the visual pathways, including the lateral geniculate nucleus (LGN), the posterior pulvinar, the striate and extrastriate visual areas and the inferior temporal gyrus and lateral orbital cortex, regions that are part of the ventral stream which is involved in object recognition (Noppeney et al., 2005; Shimony et al., 2006; Pan et al., 2007; Ptito et al., 2008b; Figure 2A). These changes are massive with volume reductions ranging from 20% in extrastriate visual areas up to 25% in the primary visual cortex (Ptito et al., 2008b). Gray matter reductions also occur in non-visual areas such as the hippocampus (Chebat et al., 2007; Fortin et al., 2008), the extrapyramidal motor system (caudate, lenticular nuclei, and fornix), the prefrontal cortex and the posterior insula. Besides these volumetric reductions in gray matter, congenitally blind subjects show an increase in cortical thickness in the cuneus (Figure 2B) which is likely due to a reduction in pruning during the early maturation phase of the cortex, resulting from the absence of visual input.


The nature of consciousness in the visually deprived brain.

Kupers R, Pietrini P, Ricciardi E, Ptito M - Front Psychol (2011)

Anatomical and metabolic changes in the congenitally blind brain. (A) Axial brain slices showing reductions in gray (red) and white matter (blue) in congenitally blind compared to matched sighted control subjects. All components of the visual system in the blind are reduced in volume (after Ptito et al., 2008b). (B) Differences in cortical thickness between congenitally blind and sighted control subjects. Despite a reduction in volume of the occipital cortex, cortical thickness of the cuneus is increased in congenitally blind subjects (unpublished data from our lab). (C) Mid-sagittal brain slices showing increased resting-state glucose metabolism in the congenitally blind brain. Illustrative examples of cerebral glucose metabolism in a congenitally blind (left) and a normal sighted control (right) subject (Kupers et al., 2009).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3111253&req=5

Figure 2: Anatomical and metabolic changes in the congenitally blind brain. (A) Axial brain slices showing reductions in gray (red) and white matter (blue) in congenitally blind compared to matched sighted control subjects. All components of the visual system in the blind are reduced in volume (after Ptito et al., 2008b). (B) Differences in cortical thickness between congenitally blind and sighted control subjects. Despite a reduction in volume of the occipital cortex, cortical thickness of the cuneus is increased in congenitally blind subjects (unpublished data from our lab). (C) Mid-sagittal brain slices showing increased resting-state glucose metabolism in the congenitally blind brain. Illustrative examples of cerebral glucose metabolism in a congenitally blind (left) and a normal sighted control (right) subject (Kupers et al., 2009).
Mentions: The results of VBM studies have revealed a significant gray matter atrophy of all brain structures of the visual pathways, including the lateral geniculate nucleus (LGN), the posterior pulvinar, the striate and extrastriate visual areas and the inferior temporal gyrus and lateral orbital cortex, regions that are part of the ventral stream which is involved in object recognition (Noppeney et al., 2005; Shimony et al., 2006; Pan et al., 2007; Ptito et al., 2008b; Figure 2A). These changes are massive with volume reductions ranging from 20% in extrastriate visual areas up to 25% in the primary visual cortex (Ptito et al., 2008b). Gray matter reductions also occur in non-visual areas such as the hippocampus (Chebat et al., 2007; Fortin et al., 2008), the extrapyramidal motor system (caudate, lenticular nuclei, and fornix), the prefrontal cortex and the posterior insula. Besides these volumetric reductions in gray matter, congenitally blind subjects show an increase in cortical thickness in the cuneus (Figure 2B) which is likely due to a reduction in pruning during the early maturation phase of the cortex, resulting from the absence of visual input.

Bottom Line: 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?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.

View Article: PubMed Central - PubMed

Affiliation: Institute of Neuroscience and Pharmacology, Panum Institute, University of Copenhagen Copenhagen, Denmark.

ABSTRACT
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.

No MeSH data available.


Related in: MedlinePlus