Idiothetic orientation and path integration in unilateral hippocampal atrophy and sclerosis

Abstract

We determined the effects of hippocampal lesions on idiothetic spatial orientation by exposing 14 patients with unilateral hippocampal atrophy and/or sclerosis (HAS) and 10 normal controls to random rotational displacements ( $\pm {30}^{\circ }\text{–}{180}^{\circ }$ ) in darkness and examined their ability to rotate themselves back to the initial position. In comparison to controls, the patients responses were distinctly hypometric ( $\mathit{p}\mathrm{<}0.005$ ). Patients with right hippocampal lesions showed a trend towards higher come back errors ( $\mathit{p}=0.08$ ). Normal controls could maintain their accuracy over five consecutive trials. Patients, beginning with less accuracy, showed significant improvement after each trial ( $\mathit{p}\mathrm{<}0.001$ ). The findings suggest that unilateral HAS impair the immediate recall of idiothetic spatial information, but does not affect long-term spatial learning.