New findings related to autonomic nervous system (ANS) functions may reveal some brain functions, since they can be observed by real time analysis. ANS parameters (skin potential and resistance, skin temperature and blood flow, instantaneous heart rate) and instantaneous respiratory frequency are quantified by original techniques and indices. Results show that ANS responses correlate with mental imagery. Imagery contents influence autonomic responses, thus making it comparable to real activity. Therefore, by using two shooting events as models, the almost identical nature of the ANS response is evidenced during real shooting and in mental concentration before shooting. Next, shooting activity imagery can be distinguished from neutral imagery but is comparable to the activity itself as far as ANS responses are concerned.