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

Full Abstract

The posterior parietal cortex (PPC) plays a role in spatial updating of goals for eye and arm movements across saccades, but less is known about its role in updating perceptual memory. We reported previously that transsaccadic memory has a capacity for storing the orientations of three to four Gabor patches either within a single fixation (fixation task) or between separate fixations (saccade task). Here, we tested the role of the PPC in transsaccadic memory in eight subjects by simultaneously applying single-pulse transcranial magnetic stimulation (TMS) over the right and left PPC, over several control sites, and comparing these to behavioral controls with no TMS. In TMS trials, we randomly delivered pulses at one of three different time intervals around the time of the saccade, or at an equivalent time in the fixation task. Controls confirmed that subjects could normally retain at least three visual features. TMS over the left PPC and a control site had no significant effect on this performance. However, TMS over the right PPC disrupted memory performance in both tasks. This TMS-induced effect was most disruptive in the saccade task, in particular when stimulation coincided more closely with saccade timing. Here, the capacity to compare presaccadic and postsaccadic features was reduced to one object, as expected if the spatial aspect of memory was disrupted. This finding suggests that right PPC plays a role in the spatial processing involved in transsaccadic memory of visual features. We propose that this process uses saccade-related feedback signals similar to those observed in spatial updating.

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Author information

Author/s: Prime, Steven L (SL); Vesia, Michael (M); Crawford, J Douglas (JD);

Affiliation: Centre for Vision Research, Toronto, Ontario, Canada.

Journal and publication information

Publication Type: Journal Article; Research Support, Non-U.S. Gov't

Journal: The Journal of neuroscience : the official journal of the Society for Neuroscience (J Neurosci), published in United States. (Language: eng)

Reference: 2008-Jul; vol 28 (issue 27) : pp 6938-49

Dates: Created 2008/07/03; Completed 2008/08/12;

PMID: 18596168, status: MEDLINE (last retrieval date: 11/6/2008)

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MeSH headings (categories)

This article was linked to the MESH Headings shown below.

Adult
Brain Mapping
Electromagnetic Fields - adverse effects
Feedback - physiology; radiation effects
Female
Fixation, Ocular - physiology; radiation effects
Functional Laterality - physiology
Humans
Male
Memory - physiology; radiation effects

Memory Disorders - etiology; physiopathology
Middle Aged
Neuropsychological Tests
Parietal Lobe - physiology; radiation effects
Pattern Recognition, Visual - physiology; radiation effects
Photic Stimulation
Saccades - physiology; radiation effects
Space Perception - physiology; radiation effects
Time Factors
Transcranial Magnetic Stimulation - adverse effects; methods

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