Functional relevance of cross-modal plasticity in blind humans

  title={Functional relevance of cross-modal plasticity in blind humans},
  author={Leonardo G. Cohen and Pablo A. Celnik and {\'A}lvaro Pascual-Leone and Brian N Corwell and Lala Faiz and James M. Dambrosia and Manabu Honda and Norihiro Sadato and Christian Gerloff and M. Dolores Catala´ and Mark Hallett},
Functional imaging studies of people who were blind from an early age have revealed that their primary visual cortex can be activated by Braille reading and other tactile discrimination tasks. Other studies have also shown that visual cortical areas can be activated by somatosensory input in blind subjects but not those with sight. The significance of this cross-modal plasticity is unclear, however, as it is not known whether the visual cortex can process somatosensory information in a… 

Critical Period for Cross-Modal Plasticity in Blind Humans: A Functional MRI Study

The primary visual cortex (V1) in congenitally blind humans has been shown to be involved in tactile discrimination tasks, indicating that there is a shift in function of this area of cortex, but the

Functional connectivity between somatosensory and visual cortex in early blind humans

Recurrent transcranial magnetic stimulation is used to probe the connection between primary somatosensory cortex (S1) and early visual cortex (V1 and neighboring areas), combining rTMS with positron emission tomography (PET).

Transcranial magnetic stimulation of the occipital cortex interferes with foot movements in blind individuals

It is shown that a rhythmic foot movement performed by acquired blind participants can be disrupted by transcranial magnetic stimulation to their primary and secondary visual cortex (V1/V2), which indicates that functional repurposing of the visual cortex may not be restricted to perception and cognitive functions, but also extended to motor function.

Cortical activity during tactile exploration of objects in blind and sighted humans.

These findings suggest that visual imagery is not an obligatory condition for object activation in visual cortex, and demonstrates the massive plasticity inVisual cortex of the blind for tactile object recognition that involves both the ventral and dorsal occipital areas, probably to support the high demand for this function in the blind.

TMS of the occipital cortex induces tactile sensations in the fingers of blind Braille readers

Results suggest the presence of a polysynaptic cortical pathway between the somatosensory cortex and the visual cortex in early blind subjects, and add new evidence that the activity of the occipital lobe in the blind takes its qualitative expression from the character of its new input source, therefore supporting the cortical deference hypothesis.

Cross-modal plasticity of tactile perception in blindness.

While visual cortical areas are clearly more involved in tactile microspatial processing in the blind than in the sighted, it still remains unclear how to reconcile these tactile processes with the growing literature implicating visual cortical activity in a wide range of cognitive tasks in theblind, including those involving language.

Regions of visual cortex responding to tactile stimulation in an individual with longstanding low vision are not causally involved in tactile processing performance

The data suggest that tactile responses in S’s foveal representation reflect unmasking of latent connections between visual and somatosensory cortices and not behaviourally relevant cross-modal plasticity, which is possible that the absence of complete visual loss in S has limited the degree of causally impactful cross- modal reorganisation.

Rapid and Reversible Recruitment of Early Visual Cortex for Touch

The findings suggest that sudden and complete visual deprivation in normally sighted individuals can lead to profound, but rapidly reversible, neuroplastic changes by which the occipital cortex becomes engaged in processing of non-visual information.



Activation of the primary visual cortex by Braille reading in blind subjects

In blind subjects, cortical areas normally reserved for vision may be activated by other sensory modalities, and positron emission tomography was used to determine whether the visual cortex receives input from the somatosensory system.

Magnetic coil suppression of extrafoveal visual perception using disappearance targets.

  • C. EpsteinA. Zangaladze
  • Psychology
    Journal of clinical neurophysiology : official publication of the American Electroencephalographic Society
  • 1996
We used magnetic brain stimulation with a butterfly coil over the occipital lobes to study extrafoveal visual field effects in six subjects. The visual test pattern was a grid of asterisks around a

Visual properties of neurons in a polysensory area in superior temporal sulcus of the macaque.

The properties of most STP neurons, such as large receptive fields, sensitivity to movement, insensitivity to form, and polymodal responsiveness, suggest that STP is more involved in orientation and spatial functions than in pattern recognition.

Attenuation in detection of somatosensory stimuli by transcranial magnetic stimulation.

Feasibility of a visual prosthesis for the blind based on intracortical microstimulation of the visual cortex.

The potentially greater microelectrode density and lower power requirements of ICMS compared with surface stimulation appears encouraging for a visual prosthesis, however, further studies with blind subjects are required to optimize stimulation parameters and test complex image recognition before the feasibility of aVisual prosthesis based on ICMS can be established.

Magnetic coil suppression of visual perception at an extracalcarine site.

The results suggest specific hypotheses about the effects of magnetic stimulation on visual physiology and identify superficial occipital cortex rather than the primary visual area as the site of perceptual suppression.