Motor control of schizophrenics--II. Manual control and tracking: sensory and motor deficits

Sequential neural changes during motor learning in schizophrenia

Positron emission tomography (PET) was used to investigate differences in neural plasticity associated with learning a unique motor task in patients with schizophrenia and healthy volunteers. Working with a robotic manipulandum, subjects learned reaching movements in a force field. Visual cues were provided to guide the reaching movements. PET rCBF measures were acquired while participants learned the motor skill over successive runs. The groups did not differ in behavioral performance but did differ in their rCBF activity patterns. Healthy volunteers displayed blood flow increases in primary motor cortex and supplementary motor area with motor learning. The patients with schizophrenia displayed an increase in the primary visual cortex with motor learning. Changes in these regions were positively correlated with changes in each group's motor accuracy, respectively. This is the first study to employ a unique arm-reaching motor learning test to assess neural plasticity during multiple phases of motor learning in patients with schizophrenia. The patients may have an inability to rapidly tune motor cortical neural populations to a preferred direction. The visual system, however, appears to be highly compensated in schizophrenia and the inability to rapidly modulate the motor cortex may be substantially corrected by the schizophrenic group's visuomotor adaptations.

The effect of peripheral visual motion on focal contrast sensitivity in positive- and negative-symptom schizophrenia

The aim of the present research was to investigate the effect of peripheral (ambient) stimulation on focal visual processing using the far-out jerk effect in normal observers and subgroups with positive- and negative-symptoms in schizophrenia. The far-out jerk effect refers to a reduction in sensitivity of a briefly presented stimulus in central vision in the presence of a sudden movement or oscillation of a stimulus in peripheral vision. In order to measure the far-out jerk effect the focal contrast sensitivity of 5.0Hz modulated sinusoidal target gratings (0.5, 1.0, 2.0, 4.0, and 8.0 number of cycles per degree (c/degrees )) was measured in the presence of three kinds of peripheral surround: a blank field, a stationary 0.75 c/degrees grating, and a 5.0Hz drifting 0.75 c/degrees grating (far-out jerk effect). The findings showed that there were no significant differences in focal contrast sensitivity between the control and positive-symptom group with a blank field and stationary grating surround. However, a 5.0Hz drifting grating surround resulted in a significant reduction in contrast sensitivity at 0.5, 1.0 and 2.0 c/degrees in the positive-symptom group. In comparison with the control group the negative-symptom group showed a generalised reduction in focal contrast sensitivity, a significantly smaller far-out jerk effect, and a significant reduction in contrast sensitivity at 0.5 c/degrees with a stationary grating surround. The finding that both stationary and moving peripheral surrounds have an inhibitory effect on focal contrast sensitivity suggests that there is a dispersion in the visual demarcation between stationary and temporal events in the perception of visual motion in the negative-symptom group.

Abnormalities of response processing in a chronic psychiatric group. A possible predictor of failure in rehabilitation programmes?

This study attempted to identify, in a mixed group of chronic patients, a specific measure of cognitive processing that may be of use in predicting dependence on psychiatric care. The measures investigated are derived from reaction-time tasks. Difficulties of response processing seem to account for the largest amount of variance in current service use. When compared with other variables shown to have some predictive power (e.g. social behaviour, symptoms and chronicity), the reaction time measures fare well. Functions derived from discriminant analyses using all the variables correctly classified 90% of those requiring day care and 95% of those requiring night care. Stepwise methods produced lower classification rates but always included reaction-time measures in the predictor set. Patients with continuing cognitive difficulties are likely to remain in more supportive psychiatric settings despite rigorous rehabilitation procedures.

Brain dysfunction during motor activation and corpus callosum alterations in schizophrenia measured by cerebral blood flow and magnetic resonance imaging

Sixteen unmedicated (14 never-medicated, 2 with washout periods of 1-2 weeks) schizophrenic patients displaying positive symptoms (e.g., formal thought disorder, hallucinations, delusions) without negative symptoms (e.g., flattening of affect, loss of energy, anhedonia--type I patients), 15 unmedicated (with washout periods from 1 week to 2 years) patients with marked negative symptomatology [type II patients; criterion score below 15/above 35 on the Munich version of the Scale of Assessment of Negative Symptoms (SANS), respectively], and 31 matched normal controls were investigated using regional cerebral blood flow [rCBF; dynamic single-photon emission computerized tomography (SPECT) with Xenon-133 as tracer] and magnetic resonance imaging (MRI; spin-echo technique, T1 weighted, midsagittal cuts). rCBF measurements were performed during both resting conditions and simple motor activation. Separately, on the same day, we performed a planimetric evaluation of the callosal-brain ratio in all subjects using MRI. In accordance with previous results on a smaller sample, we found signs of diffuse bilateral rCBF hyperactivation in type I patients, as compared with signs of nonreactivity in type II schizophrenics. Both activation patterns were different from a strictly contralateral sensorimotor rCBF activation seen in normal persons (only 8 studied with SPECT). The planimetry of relative callosal area did not reveal differences compared to normal persons, when type I/II patients were taken together. However, the threefold increased variance as compared with that found in normal persons suggested biological heterogeneity in patients. We found an increase of relative callosal size in type I as compared with type II patients. In the light of some recent findings linking lack of laterality of several brain functions to increased callosal size, we propose lack of laterality/diffuse hyperactivation and increased callosal size to be connected with positive symptomatology/good prognosis schizophrenia, and vice versa.

Further analysis of the control of voluntary saccadic eye movements in schizophrenic patients

Many schizophrenic patients reveal abnormalities in the antisaccade task. To better understand the nature of these abnormalities, in the present study we have assigned to schizophrenics the no-saccade task (subjects were required to remain fixated without being disturbed by a reflexive saccade) and memory-saccade task (subjects were required to look at a remembered target) in addition to the antisaccade and saccade tasks used previously. Many schizophrenics revealed higher error rates in the no-saccade task, and latencies of saccades to a memorized target were significantly longer than controls in the memory-saccade task. Peak velocities of saccades of large amplitudes in the memory-saccade and antisaccade tasks (but not in the saccade task) were significantly slower and durations of such saccades were longer than normal controls despite the similarity between the distributions of amplitudes of such saccades between the patients and controls. These results suggest that many schizophrenics have difficulty suppressing reflexive saccades and initiating and executing appropriate volitional saccades when the goal for the movements is known but not visible.

Psychomotor disturbances in psychiatric patients as a possible basis for new attempts at differential diagnosis and therapy. IV. Brain dysfunction during motor activation measured by EEG mapping

In parts I-III of this series psychometric evidence was reported of a "psychotic motor syndrome" (PMS) in schizophrenic and endogenous depressed patients, which was not found in non-endogenous depressed or healthy persons. An attempt is reported to establish signs of brain dysfunction in these patient groups during motor activation, using a 16-channel EEG mapping system. "Resting" conditions after a special relaxation procedure were compared with simple and complex motor tasks (and music perception/reproduction; to be reported separately). Two measurements, at least 2 weeks apart, were obtained for each subject, in order to obtain information on the influence of drug treatment and/or psychopathological improvement on brain dysfunction. In all, 23 male and 25 female schizophrenics, 11 male and 18 female non-endogenous depressed patients (not actually mediated, i.e. drug naive or wash-out period of 1 week to 17 years), and 26 male and 37 female endogenous depressed patients (medicated with tri- or tetracyclic antidepressants and/or benzodiazepines; no lithium treatment) were compared with 22 male and 17 female control persons (i.e. total n = 179). Major findings were obtained in the delta and alpha frequency bands yielding signs of "diffuse hyperactivation" in schizophrenic and endogenous depressed patients as compared with the patterns found in healthy persons. However, since in the non-endogenous patients a (less marked) hyperactivation of various EEG parameters was also found, unspecific effects such as anxiety/arousal may have influenced the results in psychotic patients, which was to be explored further. Drug treatment tended to "normalize" the activation pattern both in schizophrenics and endogenous depressed patients. Viewing the findings on schizophrenics using neuroimaging methods [single photon emission computerized tomography-(SPECT), magnetic resonance imaging-(MRI), positron emission tomography-(PET)], these results suggest pathological brain organization connected to an impaired motor performance (evident peripherally as PMS) in schizophrenic and endogenous depressed patients. If it is possible to further "externally validate" (by SPECT/MRI/PET) EEG mapping data this method may exclusively offer the possibility of innocuous long-term follow up of brain dysfunction in psychotic patients ("brain function monitoring"). This could enable the early recognition (and early therapy) of negative symptoms. Finally, the EEG mapping findings provide further neurophysiological basis for the use of motor training programs in the additional therapy of psychiatric patients.

Pathological cerebral blood flow during motor function in schizophrenic and endogenous depressed patients

In this investigation we examined eight Type I (positive symptoms without marked negative symptomatology), eight Type II (marked negative symptoms) schizophrenic patients of the disordered and paranoid diagnostic subgroups (DSM-III 295.1 and 295.3), eight severely (HAMD above 35) and eight less severely (HAMD below 20) endogenous depressed patients, and eight control persons using the 133Xe inhalation method in resting condition and during motor activity of the dominant right hand. In all patient groups we found flow activation patterns that were different from those observed in normal control persons. During motor activation in Type I schizophrenics and in less severely endogenous depressed patients, we found a bilateral hyperflow and a diffuse cortical flow increase, also involving deeper cerebral structures. In Type II schizophrenics and severely endogenous depressed patients, however, we found a widespread nonreactivity of the regional cerebral blood flow (rCBF) to motor activation, with no flow increase in the contralateral primary motor area. In normal control individuals, we reproduced a 25% flow increase that was strictly limited to the contralateral primary motor area, as already reported by other authors. As only the schizophrenic patients were not under antipsychotic medication (4 with a washout of at least 1 week prior to the investigation, 12 never treated with drugs before), contaminating effects of the medication cannot be ruled out for the endogenous depressed patient groups. However, in schizophrenic patients, these results suggest a diffuse disorganization and lack of laterality of motor functional systems. In addition, the change from hyperactivity to hyporeactivity might indicate cerebral functional correlates of the change from Type I to Type II symptomatology in schizophrenic patients, which could possible prove to be of clinical importance.

Psychomotor disturbances in psychiatric patients as a possible basis for new attempts at differential diagnosis and therapy. II. Cross validation study on schizophrenic patients: persistence of a "psychotic motor syndrome" as possible evidence of an independent biological marker syndrome for schizophrenia

This study investigates the existence and course of psychomotor symptoms in schizophrenic patients (n = 57, both treated and untreated with antipsychotic drugs) as compared to 25 healthy controls. Previous psychometric studies had suggested the existence of a "psychotic motor syndrome" (PMS) both in (untreated) schizophrenic and endogenous depressed patients, consisting of disturbances of lip and tongue movements, fine and gross movements of the dominant right hand and impaired complex motor coordination of the extremities. We confirmed the existence of the PMS in this study. There was no correlation of the PMS with the psychopathological status of the patients, or with extrapyramidal side-effects of the drugs used, perhaps indicating an independent "basic syndrome" ("Basisstörung"). Factorial analyses revealed similar structures both in schizophrenic and healthy persons; the differences in motor performance may be due to an impairment of the first factor "general motor ability" in schizophrenic patients. The PMS did not disappear parallel to the psychopathological improvement of the patients, nor in the symptom-free remission interval. The role of the PMS as possible independent biological marker syndrome for schizophrenia can consequently be further supported, with its implications towards the differential diagnostic and therapeutical values of this syndrome.

Saccadic eye movements to seen and unseen targets: oculomotor errors in normal subjects resembling those of schizophrenics

Schizophrenic subjects have defects in oculomotor control which appear to be the result of inefficient processing of sensory information, not a problem in controlling the movement itself [Mather and Putchat (1983b) J. Psychiat Res. 17, 343-360]. A demonstration that manipulating sensory information by removing context information alters these same saccadic eye movements in normals is the subject of the present research. Without context information (in the dark) people make more double-jump saccades and overshoot a target, as schizophrenics do usually. Normals have a reduced number of double saccades, a different pattern of eye movement, when the target itself is not visible. These findings reinforce the suggestions that schizophrenics, despite their normal oculomotor reaction time, are less effective than normal subjects at processing the spatial information which guides their eye movement.

Eye movements of teenage children of schizophrenics: a possible inherited marker of susceptibility to the disease

Teenage children each having one schizophrenic parent showed deficits in oculomotor control which are also found in schizophrenic subjects compared with controls. They made significantly more saccadic eye movements interrupting smooth pursuit ocular tracking. They also made significantly more double-jump saccadic movements in a looking task. Since this latter difference was true only when the visual target was illuminated during the saccade (p less than 0.001), the cause was likely visual processing and not a fixation stability problem. The two measures correlated significantly for all subjects (r = 0.63), and half the experimentals had scores more than two standard deviations above the mean for controls. This suggests that a pattern of oculomotor dysfunction found in schizophrenics which comes from a single source may act as a marker for susceptibility of their offspring to the disease.