HALLUCINATIONS FOLLOWING OCCIPITAL LOBE DAMAGE - THE PATHOLOGICAL ACTIVATION OF VISUAL REPRESENTATIONS

Neuropsychological investigation of hallucinations may provide insight into the nature of these subjective phenomena, as well as inform theo ries of perception and recall. We studied a man who described continuo us visual hallucinations of object fragments (e.g., lines, corners, pa tterns) in the left visual field following a stroke in the right occip ital cortex. The subject performed normally on standardized measures o f visual perception and other cognitive abilities. He had no personali ty disturbance, and EEG during hallucinations was normal. Review of ou r records of 211 cases with focal lesions involving visual cortex reve aled 5 patients with similar complaints. The hallucinatory experience of such patients probably reflects pathological activation of neural e nsembles in the regions bordering an occipital lesion. These regions a re presumed to contain records of visual feature fragments which are c o-activated by feedback projections in the earliest visual association cortices, where they produce meaningful patterns during normal recall .