Activity in the caudate nucleus of monkey during spatial sequencing

Area of Science:

• Neuroscience
• Cognitive Neuroscience
• Primate Behavior

Background:

• The basal ganglia are implicated in the execution of behavioral sequences.
• The specific role of the caudate nucleus in spatial planning remains to be fully elucidated.

Purpose of the Study:

• To examine the function of the caudate nucleus in the construction, storage, and execution of spatial plans.
• To investigate neural activity within the caudate nucleus during sequential motor tasks.

Main Methods:

• Two rhesus macaques (Macaca mulatta) were trained on a task requiring sequential saccades and arm movements to spatially arranged targets.
• Single-unit activity was recorded from the caudate nucleus throughout task performance, analyzing neural responses during instruction, orientation, and execution phases.
• Neural activity was statistically compared across different sequences to identify sequence-specific firing patterns.

Main Results:

• Out of 2,100 recorded neurons, 387 (18.4%) were task-related, located in both the head and body of the caudate nucleus.
• Anticipatory neural activity (n=81) was observed preceding specific task events, with distinct neuronal populations showing predictive firing for target onset, sequence order, or specific target presentation.
• Phasic visual responses (n=48) to target onset were modulated by target rank, with many neurons responding selectively based on the target's position in the sequence.

Conclusions:

• The caudate nucleus plays a significant role in the sequential processing and execution of spatial plans.
• Specific neuronal populations within the caudate nucleus exhibit anticipatory and rank-dependent activity, supporting the construction and storage of behavioral sequences.
• The findings suggest that the caudate nucleus is critical for encoding the order and spatial information necessary for complex motor planning.