Awareness of self-initiated movement

Awareness of movement onset was studied in a series of three experiments. It was defined as the ability to detect computer-generated delays between the movement onset of the subject's hand and a visually displayed hand. This was accomplished by employing a Cyber Glove that rendered a computer-generated image of a hand on a computer screen.In the pilot study, an estimate of the average detection threshold of movement onset delays was obtained in 17 normal control subjects (9 females, 8 males). Peripheral view of the hands was blocked. No significant differences in detection thresholds between men and women, between left and right hands, and across types of movement (all-fingers, index-finger, index-middle-finger extension) were found.In the second study, data on detection thresholds in the absence of proprioceptive input was gathered from a patient diagnosed with sensory neuropathy of the left hand. No significant differences in detection thresholds between the affected and unaffected hand were recorded. Proprioception does not appear to be critical for awareness of movement onset delays.In the third study, 33 normal control subjects (31 females and 2 males) performed four experimental movement conditions, two passive and two active. During the passive conditions, a lever device moved the subject's finger while their hand was either visible (PF) or hidden (PH) from view. In the active condition the subject moved their own finger while their hand was either visible (AF) or hidden (AH) from view. Detection thresholds were significantly lower during the active than the passive conditions (p < 0.01). No significant main effect of view was present. It appears that internal feedback loops, as opposed to visual feedback loops, may play a critical role in awareness of movement onset.Taken together, data from all three studies suggest that the efferent copy plays an important role compared to visual or proprioceptive cues in the detection of movement onset delays