Movement Intention After Parietal Cortex Stimulation In Humans

Surgeons performed direct electrical stimulation under local anesthesia on patients in order to find out where the intention of actions originated from. To start off the surgeon informed the patient that a stimulation was about to start. The surgeon counted out loud to let the patient and experimenter know the beginning and end of a stimulation. The experimenter asked the patient whether he/she felt something or whether he/she moved. Other stimulations were done to determine areas potentially responsible for movement and language. It was found that even in the absence of actual motor responses, stimulation of the posterior parietal cortex caused patients to intend to move and to report having moved. Stimulation of the premotor cortex also triggered limb and mouth movements that weren’t consciously detected by patients. As a result it was concluded that motor intention and awareness are emerging consequences of increased parietal activity before movement execution. The subjective (and potentially illusory) feeling that we are executing a movement does not arise from movement itself, but is generated by prior conscious intention and its predicted consequences.