The posterior parietal cortex contributes to visuomotor processing for saccades in blindsight macaques

Area of Science:

• Neuroscience
• Visual Neuroscience
• Cognitive Neuroscience

Background:

• Damage to the primary visual cortex (V1) results in loss of visual awareness but preserved visuomotor function, a phenomenon known as blindsight.
• The neural underpinnings of residual visuomotor control in blindsight remain incompletely understood.

Purpose of the Study:

• To investigate the role of the posterior parietal cortex, specifically the intraparietal sulcus (IPS), in mediating visuomotor functions in a non-human primate model of blindsight.
• To elucidate the contribution of bilateral lateral bank of the intraparietal sulcus (lbIPS) to visuomotor tasks following V1 lesions.

Main Methods:

• A unilateral V1 lesion model was created in non-human primates.
• Positron emission tomography (PET) was used to assess changes in saccade-related visuomotor activity.
• Single-unit recordings were performed in the lbIPS.
• Pharmacological inactivation (muscimol injection) of the lbIPS was employed to assess its causal role in visuomotor behavior.

Main Results:

• V1 lesions induced significant changes in saccade-related visuomotor activity in both ipsilesional and contralesional posterior parietal cortex.
• Single-unit recordings demonstrated visual responses in the lbIPS to targets in the V1 lesion-affected visual field.
• Inactivation of either ipsilesional or contralesional lbIPS significantly impaired saccades towards targets in the V1 lesion-affected visual field.

Conclusions:

• The bilateral lbIPS plays a critical role in supporting visuomotor functions in the context of blindsight.
• These findings highlight the distributed nature of visual processing and the compensatory mechanisms within the parietal cortex after V1 damage.