Single cell activity in ventral prefrontal cortex of behaving monkeys

Area of Science:

• Neuroscience
• Cognitive Neuroscience
• Primate Neurophysiology

Background:

• The ventral prefrontal cortex (VPC) is crucial for cognitive functions, including short-term memory and decision-making.
• Understanding the specific roles of different VPC subregions at the cellular level is essential for elucidating their behavioral functions.

Purpose of the Study:

• To investigate single unit activity in distinct lateral and medial areas of the monkey VPC during short-term memory tasks.
• To characterize neuronal responses related to cue perception, memory retention, and reward processing.

Main Methods:

• Extracellular recordings of single unit activity in the VPC of monkeys performing spatial delayed response and delayed matching to sample tasks.
• Analysis of neuronal firing patterns during cue presentation, delay periods, and post-trial intervals related to reward.

Main Results:

• Two main categories of unit activity were identified: non-specific and discriminative discharges.
• Nearly half of units showed altered firing during the delay period, with 18% related to cue quality.
• Three types of post-trial activity were distinguished, potentially encoding reward availability (Type I), deviations from reward expectancy (Type II), and trial termination (Type III).
• Topographic differences in cell types were observed, with Type I more prevalent laterally and Type II medially, particularly in post-trial activity.

Conclusions:

• VPC neurons exhibit diverse activity patterns related to memory and reward processing.
• Distinct neuronal populations in lateral and medial VPC show topographic specialization, especially in post-trial reward-related activity.
• These cellular properties, combining cue/delay and post-trial activity, may underlie the known behavioral functional differences between VPC subregions.