Dissociation of neglect subtypes with transcranial magnetic stimulation.

OBJECTIVE

To identify two forms of hemispatial neglect, attentional and intentional, in healthy volunteers using frontal and parietal repetitive transcranial magnetic stimulation (rTMS).

METHODS

Ten healthy volunteers performed line bisection tasks while viewing stimuli on closed circuit TV. Direct view of the exploring hand and the target was precluded and the TV monitor guided performance. In the normal condition, the direction of hand movement on the table (workspace) was congruent with that on the monitor, and in the reversed condition, the lateral movement in the workspace occurred in the opposite direction on the monitor. The line bisections were performed in three conditions: without rTMS (control), with right frontal rTMS, and with right parietal rTMS.

RESULTS

In the normal condition, both right frontal and right parietal rTMS caused a significant rightward deviation (left hemispatial neglect). In the reversed condition, right frontal rTMS continued to cause rightward deviation in the workspace corresponding to leftward bias on the monitor, whereas right parietal rTMS caused leftward deviation in the workspace, corresponding to rightward bias on the monitor.

CONCLUSIONS

Right frontal repetitive transcranial magnetic stimulation causes motor-intentional neglect, whereas right parietal repetitive transcranial magnetic stimulation causes sensory-attentional neglect. Alternatively, these findings can also be explained based on a dichotomy related to an egocentric-oriented system.