Impairments in action and perception after right intraparietal damage

Area of Science:

• Neuroscience
• Cognitive Neuroscience
• Visuospatial Processing

Background:

• The intraparietal sulcus (IPS) plays a critical role in sensorimotor transformations and visuospatial cognition.
• Previous research on optic ataxia suggests preserved accuracy in reaching to remembered targets.

Purpose of the Study:

• To investigate the impact of a small right intraparietal sulcus (pIPS) tumor resection on visually-guided reaching and perception.
• To determine if the pIPS utilizes an eye-centered reference frame for spatial encoding.
• To examine the effect of delayed versus immediate target presentation on reaching accuracy.

Main Methods:

• A patient with a resected right pIPS tumor performed visually-guided reaching tasks with and without vision, and with immediate or delayed target presentation.
• A simple perceptual task assessed visuospatial processing by presenting successive visual stimuli.
• Reaching errors and perceptual accuracy were analyzed for hemispatial differences and effects of visual guidance and delay.

Main Results:

• The patient exhibited increased reaching errors for left-sided targets when vision was available, but no hemispatial difference when vision was occluded, supporting an eye-centered reference frame.
• Contrary to previous findings, the patient was less accurate in delayed reaching compared to immediate reaching.
• A significant deficit in visuospatial perception was observed for stimuli presented to the left of fixation, indicating a perceptual impairment after dorsal stream lesion.

Conclusions:

• Resection in the right pIPS leads to deficits in visually-guided reaching and visuospatial perception, particularly affecting the left hemifield.
• The findings suggest the pIPS is essential for maintaining accurate spatial representations in an eye-centered coordinate system.
• The study highlights the role of the dorsal stream in both online motor control and spatial perception.