Transcranial magnetic stimulation over posterior parietal cortex disrupts transsaccadic memory of multiple objects

Area of Science:

• Neuroscience
• Cognitive Psychology
• Visual Perception

Background:

• The posterior parietal cortex (PPC) is implicated in spatial updating for eye and arm movements.
• Its role in updating perceptual memory, particularly across saccades, remains less understood.
• Previous work established transsaccadic memory capacity for multiple Gabor patch orientations.

Purpose of the Study:

• To investigate the role of the PPC in transsaccadic memory using transcranial magnetic stimulation (TMS).
• To determine if the left or right PPC is more critical for maintaining visual information across saccades.
• To examine the temporal dynamics of PPC involvement during saccade-related memory updating.

Main Methods:

• Single-pulse TMS was applied over the right PPC, left PPC, and control sites in eight healthy subjects.
• TMS was delivered at different time intervals relative to saccades or during fixation.
• Behavioral performance in a visual feature memory task (fixation and saccade tasks) was compared across conditions.

Main Results:

• TMS over the left PPC and control sites did not significantly affect memory performance.
• TMS over the right PPC significantly disrupted memory performance in both fixation and saccade tasks.
• The disruptive effect was most pronounced in the saccade task when TMS coincided closely with saccade timing, reducing memory capacity.

Conclusions:

• The right PPC plays a significant role in the spatial processing required for transsaccadic memory of visual features.
• Disruption of the right PPC impairs the ability to compare pre- and post-saccadic visual information.
• This suggests the right PPC utilizes saccade-related feedback signals for spatial updating in visual memory.