Blakemore, Sarah-J; Frith, Chris D.
Functional neuroimaging studies of schizophrenia.
Brain mapping: The disorders.
Ed. John C. Mazziotta and Arthur W. Toga.
Academic Press, 2000.
523-544 of xx, 669 pp.
Abstract: This chapter discusses the neuropathology of schizophrenia and reviews structural studies on the subject. Also, neuroreceptor imaging of antipsychotics using positron emission tomography (PET), cognitive activation studies, imaging symptoms, and obstacles to functional neuroimaging and schizophrenia studies are addressed.
Monitoring the self in schizophrenia: The role of internal models.
Exploring the self: Philosophical and psychopathological perspectives
Dan Zahavi, Ed. John Benjamins Publishing Company,
Amsterdam, Netherlands. 2000. p. 185-202 of vi, 299 pp.
Series title: Advances in consciousness research.
Abstract: Discusses a series of studies that investigate how the sensory consequences of one's own actions are recognized. These studies are based on an established model of normal motor learning and control. The components of this model are summarized, and how an impairment of the model could lead to certain positive symptoms associated with schizophrenia is explained. The author then describes psychophysical and functional neuroimaging experiments investigating the normal behavioral and physiological basis of the components of the motor control model. Finally, preliminary results of a psychophysical experiment involving patients with auditory hallucinations and passivity phenomena are discussed in the context of an impairment of the functioning of the model.
Blakemore, Sarah-Jayne; Smith, J.; Steel, R.; Johnstone, E. C.; and others.
The perception of self-produced sensory stimuli in patients with auditory hallucinations and passivity experiences: Evidence for a breakdown in self-monitoring.
Psychological Medicine, 2000 Sep, v30 (n5):1131-1139.
Abstract: To examine whether certain psychotic symptomatology would be due to a defect in self-monitoring, the authors investigated the ability of 23 patients with schizophrenia and 18 with bipolar affective disorder or major depression to differentiate perceptually between self-produced and externally produced tactile stimuli. Responses to tactile stimulation were assessed in patients and in 15 normal controls. Within the psychiatric groups Subjects were divided on the basis of the presence of absence of auditory hallucinations and/or passivity experiences. Subjects were asked to rate the perception of a tactile sensation on the palm of their left hand. The tactile stimulation was either self-produced by movement of the Subject's right hand or externally produced by the experimenter. Normal controls and those psychiatric patients with neither auditory hallucinations nor passivity phenomena experienced self-produced stimuli as less intense, tickly, and pleasant than identical, externally produced tactile stimuli. In contrast, psychiatric patients with these symptoms did not show a decrease in their perceptual ratings for tactile stimuli produced by themselves as compared with those produced by the experimenter.
Frith, Chris D.; Blakemore, Sarah-Jayne; Wolpert, Daniel M.
Explaining the symptoms of schizophrenia: Abnormalities in the awareness of action.
Brain Research Reviews, 2000 Mar, v31 (n2-3):357-363.
Abstract: The authors propose that the primary cognitive deficit associated with delusions of control is a lack of awareness of certain aspects of motor control. This problem arises because of a failure in the mechanism by which the predicted consequences of an action are derived from a forward model based on the intended sequence of motor commands. This problem leads to a number of behavioural consequences, such as a lack of central error correction, many of which have been observed in patients with delusions of control and related symptoms. At the physiological level, delusions of control are associated with over-activity in parietal cortex. They suggest that this over-activity results from a failure to attenuate responses to sensations of limb movements even though these sensations can be anticipated on the basis of the movements intended. The lack of attenuation may arise from long range cortico-cortical disconnections which prevent inhibitory signals arising in the frontal areas which generate motor commands from reaching the appropriate sensory areas.
Blakemore, Sarah-J.; Frith, Chris D.; Wolpert, Daniel M.
Spatio-temporal prediction modulates the perception of self-produced stimuli.
Journal of Cognitive Neuroscience, 1999 Sep, v11 (n5):551-559.
Abstract: Investigated why self-produced tactile stimulation is perceived as less intense than the same stimulus produced externally. A tactile stimulus on the palm of the right hand was either externally produced, by a robot or self-produced by each of adult 16 Subjects. In the conditions in which the tactile stimulus was self-produced, Subjects moved the arm of a robot with their left hand to produce the tactile stimulus on their right hand via a second robot. Subjects were asked to rate intensity of the tactile sensation and consistently rated self-produced tactile stimuli as less tickly, intense, and pleasant than externally produced tactile stimuli. Using this robotic setup the authors were able to manipulate the correspondence between the action of the Subject's left hand and the tactile stimulus on their right hand. First, the delay between the movement of the left hand and the resultant movement of the tactile stimulus on the right hand was parametrically varied. Second, the authors implemented varying degrees of trajectory perturbation and varied the direction of the tactile stimulus movement as a function of the direction of left-hand movement. The tickliness rating increased significantly with increasing delay and trajectory perturbation.
Blakemore, Sarah-J.; Wolpert, Daniel M.; Frith, Chris D.
Central cancellation of self-produced tickle sensation.
Nature Neuroscience, 1998 Nov, v1 (n7):635-640.
Abstract: A self-produced tickle stimulus is perceived as less ticklish than an externally generated stimulus. A tactile stimulation device allowed a sinusoidal tactile stimulus to be applied to the left palm of Subjects (mean age 33 yrs) either by the Subjects' right hand or by the experimenter. Functional magnetic resonance imaging (MRI) recordings of neural responses were made during the 4 conditions: self-generated tactile stimulation, self-generated movement without tactile stimulation, externally generated tactile stimulation, and rest. More activity was found in somatosensory cortex when the stimulus was externally produced. Less activity in the cerebellum was associated with a movement that generated a tactile stimulus than with a movement that did not. This difference suggests that the cerebellum is involved in predicting the specific sensory consequences of movements, providing the signal that is used to cancel the sensory response to self-generated stimulation.
Blakemore, Sarah J.; Goodbody, Susan J.; Wolpert, Daniel M.
Predicting the consequences of our own actions: The role of sensorimotor context estimation.
Journal of Neuroscience, 1998 Sep, v18 (n18):7511-7518.
Abstract: During self-generated movement it is postulated that an efference copy of the descending motor command, in conjunction with an internal model of both the motor system and environment, enables us to predict the consequences of our own actions. Such a prediction is evident in the precise anticipatory modulation of grip force seen when one hand pushes on an object gripped in the other hand. Here the authors show that self-generation is not in itself sufficient for such a prediction. Two robots were used to simulate virtual objects held in one hand (of 14 adults aged 21-30 yrs) and acted on by the other. Precise predictive grip force modulation of the restraining hand was highly dependent on the sensory feedback to the hand producing the load. The results show that predictive modulation requires not only that the movement is self-generated, but also that the efference copy and sensory feedback are consistent with a specific context; in this case, the manipulation of a single object. A novel computational mechanism is proposed whereby the CNS uses multiple internal models, each corresponding to a different sensorimotor context, to estimate the probability that the motor system is acting within each context.
Blakemore, Sarah-Jayne; Rees, Geraint; Frith, Chris D.
How do we predict the consequences of our actions? A functional imaging study.
Neuropsychologia, 1998 Jun, v36 (n6):521-529.
Abstract: Examined brain responses to predictable sensory events (tones) and to similar unpredictable events, and how the processing of predictable sensory events is modified by the context of a causative self-generated action. Six male Subjects (mean age 31.5 yrs) participated in the study. Using positron emission tomography, increases in activity when the tones were unpredictable were seen in the inferior and superior temporal lobe bilaterally, the right parahippocampal gyrus, and the right parietal cortex. Self-generated actions produced activity in a number of motor and premotor areas, including dorsolateral prefrontal cortex. The authors observed an interaction between the predictability of stimuli and self-generated actions in several areas, including the medial posterior cingulate cortex, left insula, dorsomedial thalamus, superior colliculus and right inferior temporal cortex. This modulation of activity associated with stimulus predictability in the context of self-generated actions implies that these areas may be involved in self-monitoring processes.
Maintained by Francis F. Steen, Communication Studies, University of California Los Angeles