Different Properties of Visual Relearning after Damage to Early Versus Higher-Level Visual Cortical Areas

Abstract

The manipulation of visual perceptual learning is emerging as an important rehabilitation tool following visual system damage. Specificity of visual learning for training stimulus and task attributes has been used in prior work to infer a differential contribution of higher-level versus lower-level visual cortical areas to this process. The present study used a controlled experimental paradigm in felines to examine whether relearning of motion discrimination and the specificity of such relearning are differently influenced by damage at lower versus higher levels of the visual cortical hierarchy. Cats with damage to either early visual areas 17, 18, and 19, or to higher-level, motion-processing lateral suprasylvian (LS) cortex were trained to perform visual tasks with controlled fixation. Animals with either type of lesion could relearn to discriminate the direction of motion of both drifting gratings and random dot stimuli in their impaired visual field. However, two factors emerged as critical for allowing transfer of learning to untrained motion stimuli: (1) an intact LS cortex and (2) more complex visual stimuli. Thus, while the hierarchical level of visual cortex damage did not seem to limit the ability to relearn motion discriminations, generalizability of relearning with a damaged visual system appeared to be influenced by both the areas damaged and the nature of the stimulus used during training.

Benefit of multiple sessions of perilesional repetitive transcranial magnetic stimulation for an effective rehabilitation of visuospatial function

“…The evaluation of the rTMS effects was made against the backdrop of results from our laboratory (Rushmore et al ., ) and from other studies (Huxlin & Pasternak, , ; Sherk & Fowler, ; Das et al ., ) which show that unilateral ibotenic acid lesion‐induced deficits are consistent and robust, and spontaneous recovery is observed only if intensive specific training is instituted. Moreover, previous studies from our laboratory demonstrate that sham rTMS, delivered in single or accrued sessions, failed to induce visuospatial effects (Valero‐Cabré et al ., , ) and were therefore unlikely to produce recovery.…”

Acting without seeing: eye movements reveal visual processing without awareness

“…The retino-collicular pathway is associated with residual visual abilities in blindsight [8–11] and with the translation of unperceived visual signals into oculomotor outputs in these patients. In these studies, blindsight patients can be prompted with a visual cue presented in an area of normal vision or by a sound to shift their gaze to unperceived but salient stimuli in the blind hemifield.…”

“…We bring together these recent behavioral studies with neurophysiological, neuroimaging and clinical evidence supporting the role of the subcortical retino-collicular pathway [6,7] for visual processing without awareness. This fast-transmission pathway is associated with residual visual abilities in blindsight [8–11] and with the translation of unperceived visual signals into oculomotor outputs in these patients [12,13]. …”

Visual training in hemianopia alters neural activity in the absence of behavioural improvement: a pilot study

“…Several approaches have been taken to try to improve visual performance in cortical blindness, including attempting to strengthen the residual visual pathways that bypass V1. Two main types of rehabilitation training have been used: one involves presenting sinusoidal gratings repeatedly in the blind region of the visual field, and the other uses moving dot patterns . Improvements in visual performance have been reported with both protocols, in the latter case accompanied by an increase in cortical activity in response to stimulation of the blind field .…”