Blakemore, Sarah-Jayne; (2000) Recognising the sensory consequences of one's own actions. Doctoral thesis (Ph.D), UCL (University College London).

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Abstract

This thesis presents a series of studies that investigate how we recognise the sensory consequences of our own actions. The studies are based on an established 'forward model' of normal motor control. It is proposed that this type of internal model makes a prediction of the sensory consequences of self-generated movements, and this prediction is then compared with the actual sensory feedback from the movement. Self-produced sensations can be correctly predicted on the basis of motor commands, and there will therefore be little or no sensory discrepancy resulting from the comparison between the predicted and actual sensory feedback. In contrast, externally generated sensations are not associated with any motor command and therefore cannot be predicted by the model and will produce a higher level of sensory discrepancy. Impairment of a component of the forward model might result in certain schizophrenic symptoms. It has been proposed that in people with schizophrenia self-produced sensations are interpreted as being generated by an external source, for example thoughts are interpreted as external voices (auditory hallucinations) and self-produced movements are interpreted as externally controlled (delusions of control or passivity phenomena) (Frith, 1992; Frith et al., 1999). Psychophysical and functional neuroimaging experiments that investigate the behavioural and physiological basis of forward models are described in this thesis. These studies support the notion that the forward model cancels the sensory consequences of self-produced actions in order to discriminate self-produced events from externally produced events and suggest that the cerebellum is involved in the predicting the sensory consequences of actions. Results of a psychophysical study involving psychotic patients with auditory hallucinations and passivity phenomena support the proposal that these symptoms are associated with an inability to distinguish self- and externally produced events. These symptoms are discussed in the context of an impairment of a component of the forward model.

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