Benedikt Reuter

ERP correlates of conscious error recognition: aware and unaware errors in an antisaccade task

Event‐related potential (ERP) studies identified the error‐related negativity (Ne/ERN) and the error positivity (Pe) to be associated with performance errors. However, the functional significance of these components is not yet resolved. With the present study we intended to further investigate to what extent these components are related to error awareness. ERPs were recorded during an antisaccade task, and error awareness was obtained from accuracy ratings on each trial. In accordance with earlier findings, aware and unaware errors did not differ in Ne/ERN amplitude. Whereas the late Pe (400–600 ms) shows an increased parietal positivity for aware compared with unaware errors, the early Pe (200–300 ms) shows no dissociation between aware and unaware errors. These data lend further support to the view that the Ne/ERN and the (late) Pe reflect different processes in performance monitoring. In fact the present results provide a clear replication of [ S. Nieuwenhuis et al. (2001 ) Psychophysiology, 38, 752–760], showing that the Pe is associated with error awareness and remedial action. Furthermore, it has been shown that this is only true for the late Pe, whereas the early Pe like the Ne/ERN is not modulated by error awareness.

Effects of switching between leftward and rightward pro- and antisaccades

Previous studies suggested that random switching between pro- and antisaccades increases errors in both tasks. However, little is known about the effects of switching between leftward and rightward saccades (response switching). The present study investigated task and response switching using an alternating runs procedure. Tasks (i.e., prosaccades versus antisaccades) were switched every second trial. Response switches (i.e., leftward saccades versus rightward saccades) were counterbalanced across tasks and task-switching conditions. Task switching increased errors in both tasks. Response switching increased errors when antisaccades were preceded by antisaccades but not when antisaccades were preceded by prosaccades or for prosaccades regardless of the preceding saccade type. The task-switch effects suggest that both pro- and antisaccade trials activate specific production rules that can persist in a subsequent trial. The differential response-switch effects may reflect different modes of response activation in pro- and antisaccades (sensorimotor transformation of visual information versus selection of motor programs).

Poor antisaccade performance in schizophrenia: An inhibition deficit?

The antisaccade task appears to be particularly suitable for analyzing processes involved in executive control of action. Schizophrenic patients show enhanced rates of erroneous reflexive saccades in this task. This is commonly interpreted as a failure of inhibitory mechanisms. The role of volitional saccade generation is largely neglected in these accounts. In this study, experimental variations of the antisaccade task were applied to manipulate the contribution of volitional processes on antisaccade performance. Fifteen patients with a diagnosis of schizophrenia and 15 healthy control participants performed antisaccade tasks requiring them to look to the mirror location of a peripheral visual stimulus at the onset of this stimulus (standard antisaccade task) or after a brief delay (delayed antisaccade task). As expected, schizophrenic patients showed more reflexive saccade errors than controls. In the delay conditions, reflexive errors decreased, and this effect was significantly stronger in schizophrenic patients. Latencies of correct antisaccades tended to be longer in patients than in control participants. The results suggest that the generation of voluntary saccades is at least in part responsible for the antisaccade deficit in schizophrenic patients. More comprehensive models to account for executive deficits in the antisaccade task must be considered.

Distinct neural correlates for volitional generation and inhibition of saccades

The antisaccade task has proven highly useful in basic and clinical neuroscience, and the neural structures involved are well documented. However, the cognitive and neural mechanisms that mediate task performance are not yet understood. An event-related fMRI study was designed to dissociate the neural correlates of two putative key functions, volitional saccade generation and inhibition of reflexive saccades, and to investigate their interaction. Nineteen healthy volunteers performed a task that required (a) to initiate saccades volitionally, either with or without a simultaneous demand to inhibit a reflexive saccade; and (b) to inhibit a reflexive saccade, either with or without a simultaneous demand to initiate a saccade volitionally. Analysis of blood oxygen level-dependent signal changes confirmed a major role of the frontal eye fields and the supplementary eye fields in volitional saccade generation. Inhibition-related activation of a specific fronto-parietal network was highly consistent with previous evidence involved in inhibitory processes. Unexpectedly, there was little evidence of specific brain activation during combined generation and inhibition demands, suggesting that the neural processing of generation and inhibition in antisaccades is independent to a large extent.

Evidence for a deficit in volitional action generation in patients with obsessive-compulsive disorder

Obsessive-compulsive disorder (OCD) patients show deficits in tasks of executive functioning like the antisaccade (AS) task. These deficits suggest problems in response inhibition or volitional saccade generation. Thirty patients (15 nonmedicated) and 30 healthy subjects performed antisaccades and simple volitional saccades (SVS), that is, centrally cued saccades. In SVS, two aspects of volitional saccade generation were disentangled: response selection and initiation. Latencies of OCD patients were increased in volitional saccades independent of response selection demands. AS performance did not differ. Across groups, latencies in AS were faster than in SVS. Medicated patients did not differ from nonmedicated patients. In sum, response initiation is deficient in OCD patients, which may reflect a general problem in volitional action generation. This deficit did not affect antisaccade performance, possibly due to a lower volitional demand in that task.

Impaired volitional saccade control: first evidence for a new candidate endophenotype in obsessive–compulsive disorder

Recent research suggests that patients with obsessive–compulsive disorder (OCD) have deficits in the volitional control of saccades. Specific evidence comes from increased latencies of saccadic eye movements when they were volitionally executed but not when they were visually guided. The present study sought to test whether this deviance represents a cognitive endophenotype. To this end, first-degree relatives of OCD patients as genetic risk carriers were compared with OCD patients and healthy controls without a family history of OCD. Furthermore, as volitional response generation comprises selection and initiation of the required response, the study also sought to specify the cognitive mechanisms underlying impaired volitional response generation. Twenty-two unaffected first-degree relatives of OCD patients, 22 unmedicated OCD patients, and 22 healthy comparison subjects performed two types of volitional saccade tasks measuring response selection or only response initiation, respectively. Visually guided saccades were used as a control condition. Our results showed that unaffected first-degree relatives and OCD patients were significantly slowed compared to healthy comparison subjects in volitional response selection. Patients and relatives did not differ from each other. There was no group difference in the visually guided control condition. Taken together, the study provides first evidence that dysfunctional volitional response selection is a candidate endophenotype for OCD.

Schizophrenia patients show impaired response switching in saccade tasks

Action control deficits of schizophrenia patients result from frontostriatal brain abnormalities and presumably reflect an impairment of selective cognitive processes. This study aimed at dissociating two different levels of action control in saccades toward and away from visual stimuli (pro- and antisaccades). Results of previous studies suggested that task switch effects (between pro- and antisaccades) reflect the persistence of a task-specific production rule and refer to the level of task selection, whereas response switch effects (between leftward and rightward saccades) point to the persistence of a specific response program, referring to the level of response selection. In the present study, task switching and response switching were investigated in 20 schizophrenia patients and 20 control subjects. Groups did not differ concerning task switch effects. In contrast, response switching entailed a stronger enhancement of error rates in patients, suggesting a specific deficit on the level of response selection in schizophrenia. The deficit was associated with spatial working memory capacities, confirming and specifying existing hypotheses on a relationship between working memory and action control.

Neural correlates of impaired volitional action control in schizophrenia patients

Slowed initiation of volitional but not visually guided saccades indicates impaired volitional action control in schizophrenia patients (SZ). The present study aimed at identifying neural correlates of this specific deficit. Fourteen SZ and 13 healthy control participants (HC) underwent functional magnetic resonance imaging while performing volitional and visually guided saccades. SZ showed increased latencies in volitional but not in visually guided saccades. Brain activation during volitional saccades compared to visually guided saccades was increased in SZ compared to HC in several areas: the supplementary eye fields, suggesting inefficient production of volitional saccades; the prefrontal cortex, pointing to altered top down control on complex eye movements; and the left middle temporal area, suggesting changes in early sensory and attention processing during the volitional control of saccades in SZ.

Differential roles of the frontal and parietal cortices in the control of saccades

Although externally as well as internally-guided eye movements allow us to flexibly explore the visual environment, their differential neural mechanisms remain elusive. A better understanding of these neural mechanisms will help us to understand the control of action and to elucidate the nature of cognitive deficits in certain psychiatric populations (e.g., schizophrenia) that show increased latencies in volitional but not visually-guided saccades. Both the superior precentral sulcus (sPCS) and the intraparietal sulcus (IPS) are implicated in the control of eye movements. However, it remains unknown what differential contributions the two areas make to the programming of visually-guided and internally-guided saccades. In this study we tested the hypotheses that sPCS and IPS distinctly encode internally-guided saccades and visually-guided saccades. We scanned subjects with fMRI while they generated visually-guided and internally-guided delayed saccades. We used multi-voxel pattern analysis to test whether patterns of cue related, preparatory and saccade related activation could be used to predict the direction of the planned eye movement. Results indicate that patterns in the human sPCS predicted internally-guided saccades but not visually-guided saccades in all trial periods and patterns in the IPS predicted internally-guided saccades and visually-guided saccades equally well. The results support the hypothesis that the human sPCS and IPS make distinct contributions to the control of volitional eye movements.

Assessment of self-disorders in a non-clinical population: Reliability and association with schizotypy.

This study explores whether self-disorders occur and can be assessed reliably in a non-clinical sample, and whether the prevalence of these anomalies depends upon the degree of psychometrically defined schizotypy. Participants with either high (n=30) or low (n=20) schizotypy scores were interviewed using a modified version of the Examination of Anomalous Self-Experience (EASE). The degree to which interviewees experienced self-disorder symptoms was rated by the interviewer and an independent rater. Inter-rater reliability was calculated for each item, domain scores and the total score. For the total, sample most items (=66) showed substantial or perfect agreement (κ>0.61), with a few (=6) showing moderate agreement (κ>0.41). Reliability scores were only slightly lower when just the more homogeneous group of individuals with high Schizotypal Personality Questionnaire (SPQ) scores were examined. As expected, high SPQ scores were associated with a high level of self-disorders. In sum, the results suggest that self-disorders can be measured reliably in non-clinical samples and are particularly frequent in individuals with pronounced schizotypical traits.