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Dorothe A Poggel, Eva M Mueller-Oehring, Janna Gothe, Sigrid Kenkel, Erich Kasten, Bernhard A Sabel; Pseudo-hallucinations in patients with visual field defects during spontaneous and training-induced recovery. Journal of Vision 2003;3(9):669. doi: 10.1167/3.9.669.
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© ARVO (1962-2015); The Authors (2016-present)
Visual pseudo-hallucinations are associated with spontaneous recovery after visual system lesions. They are observed in 10–15% of patients with homonymous field defects. We investigated whether visual illusions also occur during visual restitution training (VRT), a computer-based treatment for the detection of white light stimuli at the visual field border. The phenomenology of training-induced illusions was compared to pseudo-hallucinations during spontaneous recovery.
In a prospective study, 19 patients with post-genicular lesions performed perimetric baseline examinations before and after a period of six months of VRT and were repeatedly interviewed, including questions on illusions. Additionally, a group of 119 patients with different pre- and post-genicular lesions answered a questionnaire on pseudo-hallucinations after VRT.
In the prospective trial, 52.6% of the patients reported mainly complex visual illusions during spontaneous recovery (moving, colored, geometrical forms, real objects, or scenes). During training, significantly more patients experienced pseudo-hallucinations, but only those who had perceived those phenomena after the lesion. Training-induced illusions were usually simple (white flashes or spots) and associated with functional recovery temporally as well as topographically. In the larger sample, 36.4% had perceived pseudo-hallucinations in the context of the lesioning event, and 15.4% reported training-induced illusions. Pseudo-hallucinations during treatment occurred significantly more often in those patients who reported an increase of visual field size.
Visual illusions presumably reflect spontaneous activity in (partially) lesioned brain areas which may be the basis for functional recovery. After a lesion, V1 and higher cortical regions are activated, generating mostly complex illusions. During VRT, V1 is specifically activated, triggering more simple pseudo-hallucinations associated with training-induced visual field increase.
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