Serial pathways from primate prefrontal cortex to autonomic areas may influence emotional expression

Area of Science:

• Neuroscience
• Autonomic Nervous System Research
• Emotional Processing

Background:

• Emotional experiences involve the orbitofrontal and medial prefrontal cortices.
• Emotional expression relies on autonomic structures and peripheral organs.
• The neural pathways connecting cortical emotion centers to the periphery remain incompletely understood.

Purpose of the Study:

• To map the pathways transmitting emotional information from the cortex to the periphery.
• To investigate if hypothalamic autonomic centers serve as a key link between prefrontal cortices and autonomic structures.
• To determine if these pathways are involved in emotional arousal and expression.

Main Methods:

• Utilized neural tracers to map projections from the orbitofrontal cortex (OFC) and medial prefrontal cortex (mPFC) to the hypothalamus and downstream autonomic centers.
• Employed bidirectional tracers in the lateral hypothalamic area (LHA) to simultaneously trace cortical inputs and hypothalamic outputs to brainstem and spinal autonomic centers.
• Used anatomical tracing to identify direct synaptic connections between the mPFC and hypothalamic neurons.

Main Results:

• Orbitofrontal and medial prefrontal cortical axons converge in the hypothalamus with neurons projecting to brainstem and spinal autonomic centers.
• Densely distributed projection neurons in the OFC and mPFC lead to the hypothalamus.
• Hypothalamic axons terminate in brainstem structures and the intermediolateral column, innervating peripheral autonomic organs.
• Direct evidence shows mPFC axons synapse with hypothalamic neurons via large boutons.
• The OFC, mPFC, and hypothalamic autonomic centers are interconnected with the amygdala.

Conclusions:

• Descending pathways from the OFC and mPFC, connected to the amygdala, enable rapid prefrontal cortex influence on the autonomic system.
• These pathways are crucial for the appreciation and expression of emotions.
• The hypothalamus acts as a critical relay for emotional information from higher cortical areas to the autonomic periphery.