Some circuit operations in the mammalian brain.

Area of Science:

• Neuroscience
• Motor Control
• Systems Neuroscience

Background:

• Spinal cord neuronal connectivities follow Sherringtonian principles of divergence and convergence.
• Neuronal communication involves excitatory or inhibitory synapses mediated by neurotransmitters.
• Inhibitory neurons typically function in feedback or feedforward circuits.

Purpose of the Study:

• To explore the neural basis of voluntary movement initiation.
• To investigate the role of the supplementary motor area (SMA) in motor control.
• To elucidate the circuits involved in preprogramming voluntary movements.

Main Methods:

• Review of neuronal connectivities in the spinal cord.
• Analysis of Sherringtonian principles (divergence and convergence).
• Examination of evidence implicating the SMA in voluntary movement.

Main Results:

• Three lines of evidence suggest the supplementary motor area (SMA) is the primary neural site for voluntary movement initiation.
• The SMA engages in three main circuits for preprogramming movements: SMA-basal ganglia-thalamus, SMA-cerebellum-thalamus, and direct SMA-association cortex connections.
• The SMA serves as the 'liaison brain' for intention, with reciprocal information flow between mental intention and neuronal activity.

Conclusions:

• The supplementary motor area (SMA) plays a pivotal role in the initiation and preprogramming of voluntary movements.
• Understanding SMA circuitry provides insights into the neural mechanisms underlying intention and motor execution.
• The SMA integrates information for voluntary movement, acting as a critical hub for motor planning.