Eyes and the Mind summarises the work of Japanese schizophrenia researchers from the early 1960s through to the present. Some 38 researchers contribute an overview of eye movement and its psychophysiological correlates in the context of schizophrenia.
Among the key topics addressed are discussions of specific types of eye movement and the correlation of neuropsychological and neuroimaging findings with deficits in these movements. The authors also consider familial factors, comparison between patients with schizophrenia and those with ‘organic’ brain lesions, and visually evoked potentials in health and disease.
When subjects have their eyes closed, they make two types of horizontal eye movement: rapid and slow. The former indicate tension and implicate limbic activity. The latter are thought to reflect relaxation and a release of brain-stem nuclei from cortical inhibition. Rapid and slow horizontal movements may be super-imposed on one another and are not in mutual equilibrium. But their relative contributions may be disturbed in neuropsychiatric disorder and in response to certain medications. In schizophrenia, even patients who have greatly deteriorated and exhibit pronounced negative symptoms show an accentuation of rapid eye movements in the resting state. The authors conclude that despite apparent apathy and withdrawal such patients are intensely aroused; such arousal may indicate limbic overactivity. These findings are congruent with reports of accentuated galvanic skin response in such patients.
When patients with schizophrenia explore visual patterns they make less exploratory eye movement than ‘normals’ and those with other neuropsychiatric disorders. This distinction is particularly marked when subjects are invited to check their responses to a visual display to see if they have correctly identified discrepancies in the patterns presented. The authors argue that this particular deficit (in ‘responsive search score’) is sufficiently sensitive and specific that through the application of discriminant analyses it may be used to diagnose schizophrenia.
The organic and neuropsychological correlates of such behaviours appear to implicate not a single brain focus but a network of regions, distributed especially throughout the right hemisphere. The closest correlation appears to be with deficits on neuropsychological tests putatively linked to right frontal impairment (although any such ‘localisation’ is likely to be an oversimplification).
Smooth-pursuit eye movements (SPEMs) have been found to be abnormal in patients with schizophrenia and their relatives since the ground-breaking work of Holzman and colleagues (Reference Holzman, Proctor and Hughes1973, Reference Holzman, Proctor and Levy1974) in the 1970s (although the idea for this approach goes back to Diefendorf & Doge (1908)). In the current text the authors build on this approach, attempting to discern whether a deficit in SPEMs (while following a target) is due to a central deficit in the control of information-processing or a failure to inhibit breakthrough saccades (the ‘catch-up’ movements occurring when SPEM breaks down). A dispassionate reading of the arguments would suggest that the current answer appears to be ‘a bit of both’. The brain systems implicated comprise a network spreading from the dorsolateral pre-frontal and orbito-frontal cortices through the caudate nuclei and substantia nigra to the superior colliculi. Relevant sensory data are processed in the temporal and parietal cortices.
This is a rewarding text to read, and it will acquaint many in the international community with the original insights into schizophrenia emerging in Japan.
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