NEGLECT DETERMINED BY THE RELATIVE LOCATION OF RESPONSES

The aim of the present study was to assess the relevance of relative p osition coding of the effecters in the determination of neglect for th e space of response. Two groups of patients were selected: an experime ntal group, consisting of right brain-damaged patients with left unila teral neglect, and a control group, consisting of right brain-damaged patients without unilateral neglect. These patients participated in tw o different experiments. In Experiment 1 the stimuli were horizontally aligned to the left and the right of a fixation stimulus; in Experime nt 2 they were vertically aligned above and below the fixation stimulu s. The stimuli consisted either of the number '1' or the number '2'. I n both experiments, the patient was required to give a relative left k ey press response upon presentation of number '1' and a relative right key press response upon presentation of number '2'. The responses wer e recorded using the index and middle fingers of the right hand and th e response keyboard was located on the right side of body midline. In each experiment there were two hand response conditions: standard and reversed. Under the former condition the hand was in the normal uprigh t position; under the latter the hand and the response keyboard were r otated by similar to 180 degrees. Under the standard condition, the tw o effecters were located on the typical anatomical spatial position, i .e. the index finger, which was located on the left relative position, pressed the left key, and the middle finger, which was located on the right relative position, pressed the right key. Under the reversed co ndition, the positions of the two effecters were reversed, i.e. the mi ddle finger located on the left relative spatial position pressed the left key and the index finger, located on the right relative spatial p osition, pressed the right key. The results for both experiments showe d that neglect patients were always slower to respond when the task re quired a left key response. The effect was manifest under both the sta ndard and the reversed conditions. The neglect was therefore for the s pace of response and not for the anatomical spatial position of the ef fecters.