Contralesional spatial bias in chronic hemianopia: the role of (ec)centric fixation, spatial cueing and visual search.

Patients with homonymous hemianopia often show a contralesional shift towards their blind field when bisecting horizontal lines ('hemianopic line bisection error', HLBE). The reasons for this spatial bias are not well understood and debated. Eccentric fixation and adaptive orienting of eye movements towards the blind field have been suggested as hypothetical explanations but were not tested experimentally yet. Moreover, the role of spatial attention and visual search in the blind field are unsettled issues. Here, we tested in 20 stroke patients with chronic homonymous hemianopia (10 left-sided, 10 right-sided) without visual neglect, 10 healthy control subjects and 10 neurological control patients without hemianopia whether the HLBE is related to (a) eccentric fixation and (b) is influenced by spatial-attentional cueing (left, right) and (c) related to the degree of oculomotor compensation in the blind field. Perimetric mapping of the blind spot in the ipsilesional eye was performed in 39/40 subjects. Both hemianopic patient groups showed the typical HLBE towards their blind field, while the two control samples showed only a small but significant leftward shift known as pseudoneglect. The horizontal and vertical position of the blind spot in the ipsilesional eye was within normal limits in 38 out of 40 subjects, and did not differ significantly between the four samples. Moreover, the HLBE was not significantly correlated to the horizontal or vertical position of the centre of the blind spot, thus excluding eccentric fixation as an explanation for this spatial error. Furthermore, spatial cueing by manipulating the starting position of the bisection cue (left, right) did not affect the HLBE, arguing against attentional cueing effects well known from the line bisection error in patients with spatial neglect. Finally, the size of the saccadic search field in the scotoma was not significantly correlated to the HLBE in hemianopia. We conclude that eccentric fixation, contralesional hyperattention or ipsilesional hypoattention, or good or poor oculomotor compensation of the field loss itself are not likely causes of the HLBE in chronic homonymous hemianopia. Implications of these findings and alternative explanations are discussed.

[Posturographic biofeedback training in equilibrium disorders]. / Posturographie-Biofeedback-Training bei Gleichgewichtsstörungen.

In addition to the usual physical training for treatment of ataxia, individually adaptable biofeedback training programs by means of a stationary posturographic platform and feedback via the screen of a connected microcomputer were developed, including not only static, but especially dynamic exercises. Through an open randomised study of 72 patients with ataxia of cerebellar, brainstem and vestibular origin the effect of this training was examined by analysing the training courses parameters, which were compared with the courses of 10 normal subjects, and by the patient and the physician rating the unsteadiness of stance and gait under everyday's conditions. In particular, a significant improvement of the common function could be shown at the biofeedback training group in comparison to the group only with physical training. It is therefore concluded, that this--highly accepted--training may be a valuable tool in neurological rehabilitation of atactic patients.