A neural systems theory of schizophrenia and tardive dyskinesia

Quantitative analyses of voluntary orofacial motor control in schizophrenia and tardive dyskinesia

This paper reports the results of an investigation of voluntary control of lip, jaw, and tongue movements in schizophrenic patients with and without tardive dyskinesia. The aims of the study were to determine if voluntary orofacial motor control is disrupted in schizophrenia and to evaluate the relationship between voluntary motor control deficits and selected neurological and behavioral variables. Twenty-two schizophrenic patients and 13 normal control subjects were studied. Of the patients, 11 had moderate to severe TD. Analyses were made of performance on pursuit tracking tasks to evaluate differences between TD and non-TD patients and between medicated and currently unmedicated patients. The results indicated significant group differences in voluntary orofacial motor control. The finding that many non-TD patients exhibited voluntary motor dyscontrol suggests that this may represent a disorder independent of the involuntary dyskinesia. The findings indicated that the level of neuroleptic and/or antiparkinsonian medication was unrelated to the degree of voluntary motor control impairment. The results are discussed in terms of probable neurophysiological mechanisms underlying the motor control deficits in schizophrenia.

A systems model of schizophrenic dysfunction

A review of pertinent literature suggests that central integrative, as opposed to peripheral, systems are primarily at fault in schizophrenia. More specifically, it is proposed that the central decision apparatus, defined as the subsystems which determine goals and end-states, is intermittently dysfunctional. This dysfunction, in turn, leads to a decoupling of the negative feedback system which normally aligns responses with the desired goal. The failure of these central systems is accompanied by an increase of diffuse activity within neural systems, semiautonomous activity on the part of subsystems, and a partial failure to regulate arousal systems. The paper closes with suggestions for future research in schizophrenia.

Parietal laterality and violence

To test whether laterality of parietal lobe cerebral functioning might relate to a history of violent behavior, a sample of 33 male and female, right-handed juvenile offenders, divided into less and more violent, each performed the Weighs Test. A lateralization index (left-hand score divided by right-hand score) formed the dependent variable. Differences for sexes and ages, but not ethnicities, required corrections. As hypothesized, poorer right- than left-parietal function related positively with the violence of past crimes. A sample of 18 additional subjects replicated the findings. The results were discussed in terms of a concept of cerebral "area-appropriateness," so that when the task-appropriate area performs less well than a less-appropriate area, we may begin to infer a dysfunction which may relate to "dyscontrol" and to violent behavior.

Oral dyskinesia in brain-damaged rats withdrawn from a neuroleptic: implication for models of tardive dyskinesia

Rats with ablated frontal sensorimotor cortex and one with ablated sensorimotor connections to forebrain showed more vacuous chewing movements following 6-week chronic administration of a neuroleptic than did occipitally damaged rats or normal controls who were treated in the same way. The effect was still present 1 month after withdrawal. It was not clearly enhanced by subsequent treatments. Other behaviors (e.g., walking, rearing, or grooming) were not similarly affected by drug withdrawal. Additional results of terminal probes with amphetamine, apormorphine, and haloperidol are described, including movements labeled 'sham eating', observed only in frontal rats given apomorphine (AP). The results are interpreted in terms of a Jacksonina model of levels of brain organization; such a model may be applicable to tardive dyskinesia, seen in many schizophrenic patients who are maintained on neuroleptics for long periods.