The premotor cortex resides in the frontal lobe, just in front of the primary motor cortex. It plays a role in voluntary movement, planning and preparing actions rather than simply executing them. This area is approximately six times larger than the primary motor cortex and contributes to motor control and cognitive functions.
Preparing for Action
The premotor cortex is involved in the initial stages of movement, acting as a preparatory hub. It helps plan and ready the body for upcoming actions. This preparatory activity often involves setting up postural muscles, especially in the trunk and shoulders, to stabilize the body before limb movement.
This region is active during the preparatory phase of goal-oriented movements, integrating sensory information to form motor commands. It specifies movement parameters such as direction, amplitude, and speed. Neurons in the dorsal premotor cortex become active during the delay period between an instruction and the actual movement, indicating their role in planning.
The premotor cortex contributes to anticipatory postural adjustments (APAs), which are automatic muscle activations that occur just before a voluntary movement. These adjustments help maintain balance and stability as the body shifts its weight or prepares for a focal movement. It is involved in these predictive balance controls.
Guiding Movement and Sensory Input
The premotor cortex integrates sensory information to guide and refine movements. It is active when movements respond to external cues, such as visual or auditory signals. This allows for precise actions, adapting to the surrounding environment.
The dorsal premotor cortex processes visual and somatosensory information for planning arm movement trajectories. Neurons in this area encode the relative positions of the target, hand, and eye in preparation for reaching. Perturbing activity in the dorsal premotor cortex can increase reaction times, highlighting its role in motor planning and sensory-guided actions.
The ventral premotor cortex coordinates visual-spatial movement, using sensory data to determine how and where to move. Its caudal portion primarily uses somatosensory information for movement coordination in the immediate space around the body. The rostral part is more visually driven, playing a part in coordinating and initiating grasping movements.
Social Understanding and Complex Behavior
Beyond basic movement control, the premotor cortex contributes to complex cognitive functions, including social understanding. This region contains “mirror neurons,” specialized cells that activate both when an individual performs an action and when they observe the same action performed by someone else. This dual activation contributes to understanding others’ actions and intentions, and facilitates imitation.
The ventral premotor cortex is part of the mirror neuron system, a network active during action execution and observation. These mirror neurons may encode an abstract representation of motor actions, helping to comprehend the goals behind observed movements. This system is also implicated in motor learning, particularly through observation.
The premotor cortex also plays a role in using abstract rules to guide behavior and select appropriate actions. The dorsal premotor cortex selects motor responses based on learned associations between sensory cues and specific movements. This function extends to the learning of motor skills and the cognitive control of movement.
How the Premotor Cortex Connects
The premotor cortex does not operate in isolation but is part of a larger, interconnected network within the brain. It has strong connections with the primary motor cortex, supplementary motor area, and regions of the parietal and prefrontal cortices. These connections enable seamless coordination of complex movements and integration of diverse information.
Fibers from the premotor cortex project directly to the spinal cord, influencing the control of trunk muscles. It also communicates with subcortical structures like the striatum and motor thalamus. Collaboration with the parietal cortex allows for planning reaching or grasping movements, as the parietal cortex integrates sensory information about body position and surroundings.