Impairment of willed actions and use of advance information for movement preparation in schizophrenia

Cued fluency protocol reveals dynamic symptomatic-dependent processes of goal-directed behaviours in schizophrenia

INTRODUCTION

Differential impairments of willed actions and routine behaviours are the subject of many studies into schizophrenia. These impairments in generating and controlling goal-directed behaviours are reported in studies showing the effect of cueing in cognitive or motor tasks in people with schizophrenia. The aim of this study was to assess the performance of people with schizophrenia in a cued fluency protocol reworked to fit the concept of goal-directed behaviour. The extent to which results could be better explained by goal-directed generation issues, according to a symptomatic framework, than by semantic retrieval or semantic processing impairments, was also investigated.

METHODS

We compared the performance of 43 individuals with schizophrenia to a control group of 26 participants. Participants were assessed with neuropsychological tests. The dominance of positive and negative symptoms, and apathetic profile, were also evaluated. All participants completed a cued fluency protocol.

RESULTS

Despite a significant improvement, not all people with schizophrenia exhibited equal cueing benefits. The participants with negative symptom dominance appeared to benefit more from cueing, even though their baseline performance was lower.

CONCLUSIONS

These results suggest that, in addition to semantic memory impairments, some cognitive tasks may be more broadly influenced by difficulties in generating goal-directed behaviours.

Response preparation and intra-individual reaction time variability in schizophrenia

Background. It is important to prepare response in advance to increase the efficiency of its execution. The process of response preparation is usually studied using the precueing paradigm. In this paradigm subjects have to employ the preceding information about further imperative stimulus to perform proper response preparation, which shortens the reaction time of subsequent response execution. Previous studies detected the impairment of response preparation in schizophrenia only with the help of electroencephalographic parameters, but not with the assessing of reaction time. Therefore, in this study we attempted to find a behavioural parameter that could detect impairment in response preparation of schizophrenia patients. It was recently found that appropriate response preparation not only shortens the reaction time but also increases its stability, which is measured with the intra-individual reaction time variability. It was also revealed that response stability could better find cognitive dysfunction in some studies of schizophrenia disorder than classical behavioural parameters. Hence, the main goal of this study was to verify if intra-individual reaction time variability could detect the impairment of response preparation in schizophrenia patients. Materials and methods. In order to achieve the main purpose, we carried out a study with 14 schizophrenia patients and 14 control group subjects. We used precueing paradigm in our research, in which participants had to employ information about stimulus probability for the proper response preparation. Results. Our main result showed that despite the responses of schizophrenia patients were faster to the high-probability stimulus than to the low-probability one (F (1, 13) = 30.9, p < 0.001), intra-individual reaction time variability did not differ in this group between the responses to more and less probable stimuli (F (1, 13) = 0.64, p = 0.44). Conclusions. Results of the study suggest that people with schizophrenia were able to use precueing probabilistic information only to shorten their reaction time, but not to increase response stability. Therefore, it was found that intra-individual reaction time variability parameter could detect response preparation impairment in schizophrenia, and could be used in clinical purposes.

Impaired anticipatory event-related potentials in schizophrenia

Deficits in anticipation are implicated across a variety of cognitive and emotional processes in schizophrenia. Although diminished anticipatory event-related potentials (ERPs) have been detected during tasks requiring motor response preparation in schizophrenia, no prior ERP study has examined non-motor-related anticipatory processes or used motivationally engaging stimuli. Thirty-four schizophrenia outpatients and 36 healthy controls completed a cued, reaction-time contingent picture viewing task to assess two types of anticipatory ERPs, one involving motor response preparation (Contingent Negative Variation [CNV]) and one not involving motor preparation (Stimulus Preceding Negativity [SPN]). The ERP paradigm included emotional and non-emotional pictures, and participants also completed trait anhedonia questionnaires. Patients and controls demonstrated similar patterns of reaction time and self-reported emotional responses to the pictures. However, patients demonstrated generally lower CNV and SPN across pleasant, neutral, and unpleasant picture conditions. Patients also reported lower anticipatory pleasure than controls on a trait questionnaire. Schizophrenia patients demonstrate diminished motor- and non-motor-related anticipatory processing, which may have wide-ranging adverse functional consequences.

Effective Connectivity of the Fronto-parietal Network during Attentional Control

The ACC, the dorsolateral prefrontal cortex (DLPFC), and the parietal cortex near/along the intraparietal sulcus (IPS) are members of a network subserving attentional control. Our recent study revealed that these regions participate in both response anticipation and conflict processing. However, little is known about the relative contribution of these regions in attentional control and how the dynamic interactions among these regions are modulated by detection of predicted versus unpredicted targets and conflict processing. Here, we examined effective connectivity using dynamic causal modeling among these three regions during a flanker task with or without a target onset cue. We compared various models in which different connections among ACC, DLPFC, and IPS were modulated by bottom–up stimulus-driven surprise and top–down conflict processing using Bayesian model selection procedures. The most optimal of these models incorporated contextual modulation that allowed processing of unexpected (surprising) targets to mediate the influence of the IPS over ACC and DLPFC and conflict processing to mediate the influence of ACC and DLPFC over the IPS. This result suggests that the IPS plays an initiative role in this network in the processing of surprise targets, whereas ACC and DLPFC interact with each other to resolve conflict through attentional modulation implemented via the IPS.

Abnormal externally guided movement preparation in recent-onset schizophrenia is associated with impaired selective attention to external input

Several theories propose that the primary cognitive impairment in schizophrenia concerns a deficit in the processing of external input information. There is also evidence, however, for impaired motor preparation in schizophrenia. This provokes the question whether the impaired motor preparation in schizophrenia is a secondary consequence of disturbed (selective) processing of the input needed for that preparation, or an independent primary deficit. The aim of the present study was to discriminate between these hypotheses, by investigating externally guided movement preparation in relation to selective stimulus processing. The sample comprised 16 recent-onset schizophrenia patients and 16 controls who performed a movement-precuing task. In this task, a precue delivered information about one, two or no parameters of a movement summoned by a subsequent stimulus. Performance measures and measures derived from the electroencephalogram showed that patients yielded smaller benefits from the precues and showed less cue-based preparatory activity in advance of the imperative stimulus than the controls, suggesting a response preparation deficit. However, patients also showed less activity reflecting selective attention to the precue. We therefore conclude that the existing evidence for an impairment of externally guided motor preparation in schizophrenia is most likely due to a deficit in selective attention to the external input, which lends support to theories proposing that the primary cognitive deficit in schizophrenia concerns the processing of input information.

Which perspectives can endophenotypes and biological markers offer in the early recognition of schizophrenia?

The early recognition of schizophrenia seems crucial; various studies relate a longer duration-of-untreated-psychosis to a worse prognosis. We give an overview over common psychopathological early recognition instruments (BSABS, CAARMS, SIPS, IRAOS, ERIraos). However, many clinical symptoms of prodromal schizophrenia stages are not sufficiently specific. Thus we review recent contributions of neuroimaging and electrophysiological as well as genetic studies: which new diagnostic perspectives offer endophenotypes (such as P300, P50 sensory gating, MMN, smooth pursuit eye movements; indicating a specific genetic vulnerability) together with a better understanding of schizophrenic pathophysiology (state-dependent biological markers, e.g. aggravated motor neurological soft signs during psychosis) in prodromal schizophrenia when still ambiguous clinical symptoms are present. Several examples (e.g. from COMT polymorphisms to working memory deficits) illustrate more specific underlying neuronal mechanisms behind behavioural symptoms. This way, a characteristic pattern of disturbed cerebral maturation might be distinguished in order to complement clinical instruments of early schizophrenia detection.

Willed action in schizophrenia

This study examined stimulus-driven and willed action in schizophrenic patients and healthy controls using an easy finger-tap task and a more demanding peg-placement task under unimanual, bimanual and dual-task conditions. Peg-placement externally cued by a metronome was also examined, as were practice effects. Patients with marked negative symptoms placed fewer pegs unimanually with and without practice and benefited most from metronome-cueing. Under dual-task conditions, when the participants placed pegs while concurrently finger-tapping, finger-tapping slowed down relative to unimanual scores in patients more than controls. Number of pegs placed also dropped off in controls and the patients with fewer negative symptoms. However, patients with more severe negative symptoms placed just as many pegs, and sometimes more, in the dual-task, compared to the unimanual, condition. These patients appeared to be using their finger-tapping just like an 'external' pacing-stimulus for peg-placement, thus rendering their peg-placement more stimulus-driven than willed. In contrast, patients with fewer negative symptoms and controls tried to self-generate maximal performance on both finger-tapping and peg-placement, with deleterious effects on both tasks. That the patients with marked negative symptoms performed best when their actions were more stimulus-driven than willed strengthens the case that negative schizophrenic symptoms reflect a disorder of willed action.

Response anticipation and response conflict: an event-related potential and functional magnetic resonance imaging study

Response anticipation and response conflict processes are supported by executive control. However, few neuroimaging studies have attempted to study the relationship between these two processes in the same experimental session. In this study, we isolated brain activity associated with response anticipation (after a cue to prepare vs relax) and with response conflict (responding to a target with incongruent vs congruent flankers) and examined the independence and interaction of brain networks supporting these processes using event-related potentials (ERPs) and functional magnetic resonance imaging. Response anticipation generated a contingent negative variation ERP that correlated with shorter reaction times, and was associated with activation of a thalamo-cortico-striatal network, as well as increased gamma band power in frontal and parietal regions, and decreased spectral power in theta, alpha, and beta bands in most regions. Response conflict was associated with increased activation in the anterior cingulate cortex (ACC) and prefrontal cortex of the executive control network, with an overlap in activation with response anticipation in regions including the middle frontal gyrus, ACC, and superior parietal lobule. Although the executive control network showed increased activation in response to unanticipated versus anticipated targets, the response conflict effect was not altered by response anticipation. These results suggest that common regions of a dorsal frontoparietal network and the ACC are engaged in the flexible control of a wide range of executive processes, and that response anticipation modulates overall activity in the executive control network but does not interact with response conflict processing.

Parkinsonism following bilateral lesions of the globus pallidus: performance on a variety of motor tasks shows similarities with Parkinson's disease

OBJECTIVES

The authors report the results of detailed investigations into the motor function of a patient who, after a heavy drinking binge and subsequent unconsciousness, respiratory acidosis, and initial recovery, developed parkinsonism characterised by hypophonic speech and palilalia, "fast micrographia", impaired postural reflexes, and brady/akinesia in proximal (but not distal) alternating upper limb movements.

METHODS

In addition to brain magnetic resonance imaging (MRI), different aspects of motor function were investigated using reaction time (RT) tasks, pegboard and finger tapping tasks, flex and squeeze tasks, movement related cortical potentials (MRCPs), and contingent negative variation (CNV). Cognitive function was also assessed. The results were compared to those previously reported in patients with Parkinson's disease (PD).

RESULTS

Brain MRI showed isolated and bilateral globus pallidus (GP) lesions covering mainly the external parts (GPe). These lesions were most probably secondary to respiratory acidosis, as other investigations failed to reveal an alternative cause. The results of the RT tasks showed that the patient had difficulties in preparing and maintaining preparation for a forthcoming movement. MRCP and CNV studies were in line with this, as the early component of the MRCP and CNV were absent prior to movement. The patient's performance on pegboard and finger tapping, and flex and squeeze tasks was normal when performed with one hand, but clearly deteriorated when using both hands simultaneously or sequentially.

CONCLUSIONS

In general, the present results were similar to those reported previously in patients with PD. This provides further indirect evidence that the output of globus pallidus is of major importance in abnormal motor function in PD. The possible similarities of the functional status of GP in PD and our case are discussed.

Perceptional and executive deficits of chronic schizophrenic patients in attentional and intentional tasks

The present study investigated whether schizophrenic patients could develop appropriate visual orientation and motor set under precuing conditions which contrasted attentional (input selective) and intentional (output selective) information. The aim was to evaluate perceptual performance in processing visuospatial information, and executive performance in response preparation. Stimuli and/or elicited responses were controlled for selective hemispheric engagement. Age, sex and handedness matched groups of 33 chronic schizophrenic patients and 33 normal subjects were tested on choice reaction time (RT) tasks in which warning signals were manipulated regarding either where a target stimulus would occur (selective attention) or which hand to use for responding (response preparation). All subjects benefited from precued information regarding subsequent responses. However, schizophrenic patients were not able to use intentional cues as effectively as control subjects did. Interhemispheric asymmetry of spatial attention was found in patients with schizophrenia, with slowing of responses to uncued targets presented in the right visual field. There was also a decreased advantage of within-hemisphere stimulus-response conditions in the schizophrenic group. Our results support the notion that a dysfunction involving parietal and premotor areas has potential importance in the schizophrenic illness. We replicated findings which indicate that deficits of information processing in schizophrenia may affect left hemispheric mechanisms to a larger extent. The results also point toward a possible abnormal connectivity between frontal and parietal circuits in schizophrenia.