Neural interaction between the basal forebrain and functionally distinct prefrontal cortices in the rhesus monkey

Area of Science:

• Neuroscience
• Primate Brain Research
• Prefrontal Cortex Connectivity

Background:

• The prefrontal cortex (PFC) is functionally diverse, with lateral regions linked to working memory and medial/orbitofrontal regions to emotions and long-term memory.
• Understanding the connections between the PFC and the basal forebrain (BF) is crucial for deciphering modulatory influences on cognitive and emotional processes.

Purpose of the Study:

• To investigate the specific and common connections between functionally distinct PFC regions (lateral, medial, orbitofrontal) and the basal forebrain in rhesus monkeys.
• To elucidate the topographical organization of ascending and descending projections within the PFC-BF circuitry.

Main Methods:

• Utilized neural tracers to map projections between the PFC and the basal forebrain.
• Identified BF nuclei using choline acetyltransferase (ChAT) for ascending projections.
• Characterized descending projections using striatal-related markers (dopamine, phosphoproteins) to delineate ventral pallidum and extended amygdala.

Main Results:

• Ascending BF projections showed partial overlap but a general topography: posterior nucleus basalis to lateral PFC; rostral sectors to medial/orbitofrontal PFC; diagonal band to medial/orbitofrontal PFC.
• Descending projections were specific, originating from posterior limbic PFC (medial/orbitofrontal) and terminating in the diagonal band and anterior nucleus basalis.
• Medial/orbitofrontal PFC also projected to the ventral pallidum and extended amygdala, linking to autonomic control systems.

Conclusions:

• Lateral PFC has unidirectional input from the BF, supporting working memory functions.
• Medial and orbitofrontal PFC exhibit robust bidirectional connections with the BF, crucial for emotion and long-term memory processing.
• The PFC-BF circuitry, particularly via medial/orbitofrontal pathways, modulates autonomic functions for emotional expression.