Neuroplasticity in Blind Subjects After Repetitive Tactile Stimulation

• MRI Functional Connectivity of the visual pathway [ Time Frame: 1 year ] [ Designated as safety issue: No ]
  Functional Connectivity analysis (fcMRI) is a tool that allows functionally associated brain regions to be identified. fcMRI takes advantage of the observation that the brain regions exhibit spontaneous, low frequency variations as measured using blood oxygenation level-dependent (BOLD) imaging.
  
  

The investigators will use passive repetitive tactile stimulation over a period of 3 months, one hour a day for five days a week, with vertical, horizontal and oblique lines generated randomly by a tactile stimulator. Our aim is (a) to study if repetitive tactile stimulation can create cross-modality and improve recognition and localization of patterns in blind people, (b) to evaluate the impact of this training on brain activity the investigators performed high-density scalp EEG recording during the initial stimulation session and in the last one. And (c) measure the functional connectivity of the brain with resting state MRI pre and post training. The resting state MRI protocol consist on one run of T1WI and three bold runs (TE=30ms,TR=3000ms, flip angle 90º,voxel size 3mm, 124 time points, 0 gap).

Cross-modality sensory stimulation may offer a good opportunity to improve recognition, localization and navigation in blind people. Although the neural substrate of this multimodality integration is not fully understood yet. Some areas of the brain, mainly the lateral occipital cortex, are specialized for visual object recognition and they can be activated by tactile stimuli. This activation of the visual cortex might lead to visual-like perception, regardless of the sensory input modality.

In the blind the high demand required by object recognition appears to recruit also ventral and dorsal occipital areas. Blindness modifies neocortical processing of non-visual tasks, including frontoparietal and visual regions during tactile stimulation. It is also known that people with blindness proficient in the use of a visuo-tactile sensory substitution device that presents visual images as patterns of electric stimuli to the subject's tongue, like Bach-y-Rita and Ptito said, show occipital cortex activation in an orientation-discrimination task.

As far as the investigators know there are no studies aimed at understanding the relationship between activation of lateral occipital cortex and the ability to recognize objects presented to the hand along time. In particular, the investigators tested if repetitive passive tactile stimulation leads to activation of visual areas and recognition of spatial patterns in people with blindness.