Contribution of the primate prefrontal cortex to the gap effect

Area of Science:

• Neuroscience
• Cognitive Neuroscience
• Primate Research

Background:

• The gap effect reduces saccadic reaction times (SRTs) by introducing a temporal gap before target presentation.
• Express saccades, very fast reflexive eye movements, are often linked to prefrontal cortex (PFC) dysfunction.
• Understanding PFC involvement in these phenomena is crucial for neurological disorder research.

Purpose of the Study:

• To investigate the role of the lateral prefrontal cortex (PFC) in the gap effect and express saccade generation.
• To analyze neuronal activity in the PFC during a gap saccade task in rhesus monkeys.

Main Methods:

• Two rhesus monkeys were trained on a gap saccade task with varying fixation point (FP) disappearance times (200 ms or 600 ms).
• Neuronal activity was recorded from the lateral PFC (areas 8 Ar and 46) in 214 neurons.
• Neurons were categorized based on their task-related activity patterns, including fixation, FP offset, preparatory, visual, post-saccadic, and reward-related neurons.

Main Results:

• 39% of recorded PFC neurons (84 out of 214) showed task-related activity.
• Fixation neurons exhibited decreased activity during the gap preceding express saccades.
• No significant topographical differences were observed among the categorized neuronal groups.

Conclusions:

• A reduction in the activity of PFC fixation-related neurons may underlie the increased incidence of express saccades observed in prefrontal disorders.
• These findings highlight the PFC's critical role in controlling saccadic eye movements and suppressing reflexive responses.