What is the relationship between the external and internal globus pallidus?

The correct choice highlights the relationship between the external and internal globus pallidus in terms of their neural interactions. The external globus pallidus plays a critical role in the regulation of motor control by providing inhibitory output to its neighboring internal globus pallidus. This means that the external globus pallidus influences the activity of the internal globus pallidus, which in turn is involved in modulating the thalamus and subsequently motor pathways. By inhibiting its medial counterpart, the external globus pallidus helps coordinate proper motor function, making the relationship between these two structures essential for movement regulation.

This dynamic of inhibition is crucial in the context of the basal ganglia circuitry, as it contributes to the balance of excitatory and inhibitory signals that govern motor planning and execution. The internal globus pallidus is primarily responsible for sending inhibitory signals to the thalamus, and the external globus pallidus supports this by modulating its activity through inhibition.