Perspective-taking in blindness: electrophysiological evidence of altered action representations

It is well established that the mental simulation of actions involves visual and/or somatomotor representations of those imagined actions. To investigate whether the total absence of vision affects the brain activity associated with the retrieval of motor representations, we recorded the readiness potential (RP), a marker of motor preparation preceding the execution, as well as the motor imagery of the right middle-finger extension in the first-person (1P; imagining oneself performing the movement) and in the third-person (3P; imagining the experimenter performing the movement) modes in 19 sighted and 10 congenitally blind subjects. Our main result was found for the single RP slope values at the Cz channel (likely corresponding to the supplementary motor area). No difference in RP slope was found between 1P and 3P in the sighted group, suggesting that similar motor preparation networks are recruited to simulate our own and other people's actions in spite of explicit instructions to perform the task in 1P or 3P. Conversely, reduced RP slopes in 3P compared with 1P found in the blind group indicated that they might have used an alternative, nonmotor strategy to perform the task in 3P. Moreover, movement imagery ability, assessed both by means of mental chronometry and a modified version of the Movement Imagery Questionnaire-Revised, indicated that blind and sighted individuals had similar motor imagery performance. Taken together, these results suggest that complete visual loss early in life modifies the brain networks that associate with others' action representations.