Conscious visual abilities in a patient with early bilateral occipital damage

Giaschi, Deborah; Jan, James E.; Björnson, Bruce; Young, Sympascho; Tata, Matthew S.; Lyons, Christopher J.; Good, William V.; Wong, Peter K. H.

doi:10.1017/s0012162203001439

Cited by 16 publications

(15 citation statements)

References 73 publications

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“…In a case where damage appeared to be limited to V1, a child who had appeared blind at 2.5 years had improved basic visual function by 7 years, and no longer seemed visually impaired (Bova et al, 2008). In contrast the subject with extensive bilateral occipital damage from birth studied by Giaschi et al (2003) was severely visually impaired, although he could name a few colors and perceive rapid movements. Functional MRI activation patterns to the moving stimuli, however, were located predominantly in the posterior superior temporal sulcus bilaterally; there was no occipital activation.…”

Section: Introductionmentioning

confidence: 87%

Visual activation of extra-striate cortex in the absence of V1 activation

et al. 2010

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Research highlights▶ Gray matter of V1 shows abnormal T1 characteristics and its perfusion is reduced. ▶ Damage is confined to gray matter with no adjacent white matter involvement. ▶ BOLD activation levels in the calcarine sulcus are drastically reduced. ▶ Activation of extrastriate regions to visual stimulation is preserved. ▶ Pathway between LGN and V1 shows degeneration; between LGN and V5/MT is intact.

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Section: Introductionmentioning

confidence: 87%

Visual activation of extra-striate cortex in the absence of V1 activation

et al. 2010

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“…Recently, visual awareness of moving stimuli was also found in an individual with complete absence of both occipital lobes due to perinatal damage, as confirmed by structural and functional neuroimaging, further supporting the possibility of maintaining visual awareness in case of early damage. 75 In summary, early damage seems to be associated with an increased sensitivity towards the stimuli hitting the blind field, associated with an increased awareness of perception. The possible underlying mechanisms are discussed below.…”

Section: Level Of Subjective Awareness Of the Blind Visual Fieldmentioning

confidence: 96%

Plasticity of the visual system after early brain damage

Guzzetta

D’Acunto

Rose

et al. 2010

Develop Med Child Neuro

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The aim of this review is to discuss the existing evidence supporting different processes of visual brain plasticity after early damage, as opposed to damage that occurs during adulthood. There is initial evidence that some of the neuroplastic mechanisms adopted by the brain after early damage to the visual system are unavailable at a later stage. These are, for example, the ability to differentiate functional tissue within a larger dysplastic cortex during its formation, or to develop new thalamo-cortical connections able to bypass the lesion and reach their cortical destination in the occipital cortex. The young brain also uses the same mechanisms available at later stages of development but in a more efficient way. For example, in people with visual field defects of central origin, the anatomical expansion of the extrastriatal visual network is greater after an early lesion than after a later one, which results in more efficient mechanisms of visual exploration of the blind field. A similar mechanism is likely to support some of the differences found in people with blindsight, the phenomenon of unconscious visual perception in the blind field. In particular, compared with people with late lesions, those with early brain damage appear to have stronger subjective awareness of stimuli hitting the blind visual field, reported as a conscious feeling that something is present in the visual field. Expanding our knowledge of these mechanisms could help the development of early therapeutic interventions aimed at supporting and enhancing visual reorganization at a time of greatest potential brain plasticity.Brain plasticity consists of the modifications to the central nervous system in response to environmental stimulation, which allow us to learn new skills, remember new information, and recover from brain injury. 1 Mechanisms of neuronal plasticity are more powerful during early development. For example, children are faster than adults in learning a new language or in achieving complex skills such as playing a musical instrument. 2 Similarly, children lacking proper environmental inputs early in life are more susceptible to an abnormal development of the functions related to those inputs (the principle of sensitive periods 3 ).The presence of more powerful mechanisms of neuronal plasticity during early development should imply that recovery from brain damage is more effective after early lesions than after lesions occurring later in life. This principle was first suggested by Paul Broca in 1865 4 and then more systematically explored by Margaret Kennard in the late 1930s. 5 Since then, most of the studies of different species have supported this general principle, although describing a more complex picture, which takes into consideration several other aspects beyond timing of the insult, including the location and extension of injury (e.g. focal versus diffuse), the clinical phenotype (e.g. presence of seizures), or the genetic susceptibility of the individual. 6 Today, there is general agreement that the way the bra...

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“…We parametrically assessed motion coherence performance for three different speeds: very fast (27.27°/s, identical to the speed in the motion coherence threshold experiment, see above, similar to Meteyard et al , 2008; Gilaie-Dotan et al , 2013), fast (10.8°/s, similar to speeds in previously reported paradigms: Zihl et al , 1983; Rizzo et al , 1995; Scase et al , 1996; Noguchi et al , 2005; van Boxtel and Erkelens, 2006; Pilly and Seitz, 2009; Tailby et al , 2010), and medium (5.4°/s, used in previous studies: Scase et al , 1996; Rees et al , 2000; Giaschi et al , 2003). This allowed us to assess performance for motion speeds ranging from 5.4–27.27°/s.…”

Section: Methodsmentioning

confidence: 87%

The role of human ventral visual cortex in motion perception

Gilaie-Dotan¹,

Saygın²,

Lorenzi³

et al. 2013

Brain

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Visual motion perception is fundamental to many aspects of visual perception. Visual motion perception has long been associated with the dorsal (parietal) pathway and the involvement of the ventral ‘form’ (temporal) visual pathway has not been considered critical for normal motion perception. Here, we evaluated this view by examining whether circumscribed damage to ventral visual cortex impaired motion perception. The perception of motion in basic, non-form tasks (motion coherence and motion detection) and complex structure-from-motion, for a wide range of motion speeds, all centrally displayed, was assessed in five patients with a circumscribed lesion to either the right or left ventral visual pathway. Patients with a right, but not with a left, ventral visual lesion displayed widespread impairments in central motion perception even for non-form motion, for both slow and for fast speeds, and this held true independent of the integrity of areas MT/V5, V3A or parietal regions. In contrast with the traditional view in which only the dorsal visual stream is critical for motion perception, these novel findings implicate a more distributed circuit in which the integrity of the right ventral visual pathway is also necessary even for the perception of non-form motion.

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Conscious visual abilities in a patient with early bilateral occipital damage

Cited by 16 publications

References 73 publications

Visual activation of extra-striate cortex in the absence of V1 activation

Visual activation of extra-striate cortex in the absence of V1 activation

Plasticity of the visual system after early brain damage

The role of human ventral visual cortex in motion perception

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