An event-related potential study on the time course of mental rotation in upper-limb amputees

- Amputees and controls showed a comparable P100 during early visual processing phase of a mental hand rotation task.
- Amputees exhibited a reduced N200 in the categorization of hand stimuli, and this abnormality was correlated with the duration since amputation.
- Amputees had a larger P300 for the intact upright hand in the mental rotation phase, indicating that the intact hand gained more significance.

ObjectiveMental rotation of body parts involves sequential cognitive processes, including visual processing, categorization and the mental rotation process itself. However, how these processes are affected by the amputation of a limb is still unclear.MethodsTwenty-five right upper-limb amputees and the same number of matched healthy controls participated in a hand mental rotation task. Thirty-two-channel electroencephalography (EEG) was recorded and the event-related potentials (ERPs) were analyzed.ResultsIn the early visual processing phase, amputees and controls showed a similar P100. During the categorization phase, the amputees exhibited a decreased N200 compared with controls, and the decline was positively correlated with the time since amputation. In the mental rotation phase, controls had a larger ERP for the right upright hand than for the left upright hand, while amputees had a larger ERP for the left (intact) upright hand than for the right (affected) upright hand.ConclusionsEarly visual processing was not affected by limb amputation. However, the perceptual salience of hand pictures decreased and the intact hand gained more significance in the amputees.SignificanceEvent-related potentials had the capability of showing the differences in categorization and mental rotation phases between amputees and controls.