Control of working memory in rhesus monkeys (Macaca mulatta)

Area of Science:

• Cognitive Neuroscience
• Animal Behavior

Background:

• Cognitive control is essential for effective working memory utilization.
• While human rehearsal strategies are known, active cognitive control in nonhuman primates remains poorly understood.
• Previous studies on nonhuman working memory lacked definitive evidence for active control.

Purpose of the Study:

• To investigate whether nonhuman primates exert cognitive control over their working memory.
• To determine if monkeys can actively modulate memory based on predictive cues.

Main Methods:

• Monkeys were trained on a visual matching-to-sample task with predictive memory cues (remember vs. forget).
• Probe trials with unexpected test types were used to assess memory control, controlling for reward and surprise.
• Performance was analyzed based on cued trial types and unexpected probe trials.

Main Results:

• Monkeys showed significantly lower matching accuracy following 'forget' cues compared to 'remember' cues.
• Discrimination accuracy remained consistent across both cue conditions.
• Memory performance was superior for expected memory tests versus unexpected tests, even with lists of items.

Conclusions:

• These findings provide strong evidence that monkeys actively control their working memory.
• The results indicate that nonhuman primates can strategically manage memory resources based on task demands.