Influence of Motor Planning on Distance Perception within the Peripersonal Space

We examined whether movement costs as defined by movement magnitude have an impact on distance perception in near space. In Experiment 1, participants were given a numerical cue regarding the amplitude of a hand movement to be carried out. Before the movement execution, the length of a visual distance had to be judged. These visual distances were judged to be larger, the larger the amplitude of the concurrently prepared hand movement was. In Experiment 2, in which numerical cues were merely memorized without concurrent movement planning, this general increase of distance with cue size was not observed. The results of these experiments indicate that visual perception of near space is specifically affected by the costs of planned hand movements

Habituation:an event-related potential and dipole source analysis study

The goal of this study was to investigate habituation processes in the brain, and in particular, to identify the brain structures involved in these processes. Therefore, event-related potentials (ERPs) were recorded in response to a series of repeated, task-irrelevant, salient stimuli presented against the background of a cognitive task which required the subjects to attend to a fixation sign on a TV screen. Stimuli were presented randomly in one of four possible quadrants of the TV screen. Dipole analyses were performed in order to localize the source of stimulus repetition effects (habituation). As expected, there was a decrease in amplitude of the N1 and P3 components as a function of stimulus repetition; habituation of N1 occurred faster than that of the P3 component. It is suggested from the results of dipole analyses that the N1 effect concerns diffuse cortical activation. The P3 habituation effect seemed to involve the temporal cortex especially. (C) 2000 Elsevier Science B.V. All rights reserved