The hierarchy of cortical monitors

This chapter explores the significance of the dual meaning of the driver inputs to the thalamus in more detail. What happens to these messages when they reach the cortical hierarchies? Currently we know little about how the cortex reacts to the two meanings of the incoming messages. The efference copies that reach the cortex may act both in the control of movements, as do efference copies in other parts of the brain, and may also act to generate a conscious anticipation of an action and its sensory consequences. Or it may do both, depending on the circumstances. Where the thalamic relay fails for any reason while the motor branch remains functional, actions may be assigned, as in schizophrenic patients, to external agents. For any one cortical area, we need to understand not only the messages it receives from the thalamus but also the motor instructions it sends out and how it fits into the cortical hierarchy.