Information processing in long delay memory-guided saccades: further insights from TMS

Area of Science:

• Neuroscience
• Cognitive Psychology
• Experimental Psychology

Background:

• Spatial working memory is crucial for guiding behavior.
• The dorsolateral prefrontal cortex (DLPFC) is implicated in executive functions, including working memory.
• Understanding the temporal dynamics of DLPFC involvement in spatial memory is essential.

Purpose of the Study:

• To investigate the role of the dorsolateral prefrontal cortex (DLPFC) in spatial working memory using transcranial magnetic stimulation (TMS).
• To examine how memory delay duration influences the impact of DLPFC disruption on memory-guided saccades.

Main Methods:

• Eight healthy subjects performed memory-guided saccades with short (3s) and long (30s) memorization delays.
• Single-pulse TMS was applied over bilateral DLPFC 1s after target presentation.
• Error in saccade amplitude was measured as the primary outcome.

Main Results:

• TMS over the DLPFC significantly increased saccade errors in both delay conditions.
• The disruptive effect of TMS was significantly more pronounced during the short delay compared to the long delay.
• This suggests a time-dependent role for the DLPFC in spatial working memory.

Conclusions:

• The DLPFC plays a critical role in the early, serial processing stages of spatial working memory.
• During longer delays, spatial memory processing appears to involve parallel mechanisms less dependent on the DLPFC.
• A mixed model of spatial working memory, incorporating serial and parallel processing, is proposed.