A study of visual perseveration

The manifestations of disordered visual perception may, as established by Hughlings Jackson for neuro-logical deficits in general, be divided into the'negative' and the 'positive'. The negative commonly present as defective areas of visual field. The positive, also not uncommon, consist in visual impressions which are either endogenous or represent an exaggerated or distorted perception of the outside world. An un-usual variant of the latter is the increased apparent duration of visual stimuli known as visual per-severation (Robinson and Watt, 1947). This consists in the continuation or repetition of a visual sensation after the stimulus object which gave rise to it has been removed from sight (Critchley, 1950). Holmes (1931) mentioned a patient who, having