Schizophrenia patients show impaired response switching in saccade tasks

Working memory capacity and the antisaccade task: A microanalytic-macroanalytic investigation of individual differences in goal activation and maintenance

The association between working memory capacity (WMC) and the antisaccade task, which requires subjects to move their eyes and attention away from a strong visual cue, supports the claim that WMC is partially an attentional construct (Kane, Bleckley, Conway, & Engle, 2001; Unsworth, Schrock, & Engle, 2004). Specifically, the WMC-antisaccade relation suggests that WMC helps maintain and execute task goals despite interference from habitual actions. Related work has recently shown that mind wandering (McVay & Kane, 2009, 2012a, 2012b) and reaction time (RT) variability (Unsworth, 2015) are also related to WMC and they partially explain WMC's prediction of cognitive abilities. Here, we tested whether mind-wandering propensity and intraindividual RT variation account for WMC's associations with 2 antisaccade-cued choice RT tasks. In addition, we asked whether any influences of WMC, mind wandering, or intraindividual RT variation on antisaccade are moderated by (a) the temporal gap between fixation and the flashing location cue, and (b) whether targets switch sides on consecutive trials. Our quasi-experimental study reexamined a published dataset (Kane et al., 2016) comprising 472 subjects who completed 6 WMC tasks, 5 attentional tasks with mind-wandering probes, 5 tasks from which we measured intraindividual RT variation, and 2 antisaccade tasks with varying fixation-cue gap durations. The WMC-antisaccade association was not accounted for by mind wandering or intraindividual RT variation. WMC's effects on antisaccade performance were greater with longer fixation-to-cue intervals, suggesting that goal activation processes-beyond the ability to control mind wandering and RT variability-are partially responsible for the WMC-antisaccade relation. (PsycINFO Database Record

Brain activation differences in schizophrenia during context-dependent processing of saccade tasks

Background

Brain function in schizophrenia has been probed using saccade paradigms and functional magnetic resonance imaging, but little information exists about how changing task context impacts saccade related brain activation and behavioral performance. We recruited schizophrenia and comparison subjects to perform saccade tasks in differing contexts: (1) two single task runs (anti- or pro-saccades alternating with fixation) and (2) one dual task run (antisaccades alternating with prosaccades).

Results

Context-dependent differences in saccade circuitry were evaluated using ROI analyses. Distinction between anti- and pro-saccade activation across contexts (single versus dual task) suggests that the schizophrenia group did not respond to context in the same way as the comparison group.

Conclusions

Further investigation of context processing effects on brain activation and saccade performance measures informs models of cognitive deficits in the disorder and enhances understanding of antisaccades as a potential endophenotype for schizophrenia.

Electronic supplementary material

The online version of this article (doi:10.1186/s12993-016-0103-2) contains supplementary material, which is available to authorized users.

Electrophysiological Endophenotypes for Schizophrenia

Endophenotypes are quantitative, heritable traits that may help to elucidate the pathophysiologic mechanisms underlying complex disease syndromes, such as schizophrenia. They can be assessed at numerous levels of analysis; here, we review electrophysiological endophenotypes that have shown promise in helping us understand schizophrenia from a more mechanistic point of view. For each endophenotype, we describe typical experimental procedures, reliability, heritability, and reported gene and neurobiological associations. We discuss recent findings regarding the genetic architecture of specific electrophysiological endophenotypes, as well as converging evidence from EEG studies implicating disrupted balance of glutamatergic signaling and GABAergic inhibition in the pathophysiology of schizophrenia. We conclude that refining the measurement of electrophysiological endophenotypes, expanding genetic association studies, and integrating data sets are important next steps for understanding the mechanisms that connect identified genetic risk loci for schizophrenia to the disease phenotype.

Abnormal negative feedback processing in first episode schizophrenia: evidence from an oculomotor rule switching task

BACKGROUND

Previous studies have shown that patients with schizophrenia are impaired on executive tasks, where positive and negative feedbacks are used to update task rules or switch attention. However, research to date using saccadic tasks has not revealed clear deficits in task switching in these patients. The present study used an oculomotor 'rule switching' task to investigate the use of negative feedback when switching between task rules in people with schizophrenia.

METHOD

A total of 50 patients with first episode schizophrenia and 25 healthy controls performed a task in which the association between a centrally presented visual cue and the direction of a saccade could change from trial to trial. Rule changes were heralded by an unexpected negative feedback, indicating that the cue-response mapping had reversed.

RESULTS

Schizophrenia patients were found to make increased errors following a rule switch, but these were almost entirely the result of executing saccades away from the location at which the negative feedback had been presented on the preceding trial. This impairment in negative feedback processing was independent of IQ.

CONCLUSIONS

The results not only confirm the existence of a basic deficit in stimulus-response rule switching in schizophrenia, but also suggest that this arises from aberrant processing of response outcomes, resulting in a failure to appropriately update rules. The findings are discussed in the context of neurological and pharmacological abnormalities in the conditions that may disrupt prediction error signalling in schizophrenia.

Abnormal mechanisms of antisaccade generation in schizophrenia patients and unaffected biological relatives of schizophrenia patients

Although errant saccadic eye movements may mark genetic factors in schizophrenia, little is known about abnormal brain activity that precedes saccades in individuals with genetic liability for schizophrenia. We investigated electrophysiological activity preceding prosaccades and antisaccades in schizophrenia patients, first-degree biological relatives of schizophrenia patients, and control subjects. Prior to antisaccades, patients had reduced potentials over lateral prefrontal cortex. Smaller potentials were associated with worse antisaccade performance. Relatives also exhibited reduced pre-saccadic potentials over lateral frontal cortex but additionally had reduced potentials over parietal cortex. Both patients and relatives tended toward increased activity over orbital frontal cortex prior to saccades. Results are consistent with lateral prefrontal dysfunction marking genetic liability for schizophrenia and underlying deficient saccadic control.

Response inhibition and response monitoring in a saccadic countermanding task in schizophrenia

BACKGROUND

Cognitive control deficits are pervasive in individuals with schizophrenia (SZ) and are reliable predictors of functional outcome, but the specificity of these deficits and their underlying neural mechanisms have not been fully elucidated. The objective of the present study was to determine the nature of response inhibition and response monitoring deficits in SZ and their relationship to symptoms and social and occupational functioning with a behavioral paradigm that provides a translational approach to investigating cognitive control.

METHODS

Seventeen patients with SZ and 16 demographically matched healthy control subjects participated in a saccadic countermanding task. Performance on this task is approximated as a race between movement generation and inhibition processes; this race model provides an estimate of the time needed to cancel a planned movement. Response monitoring can be assessed by reaction time adjustments on the basis of trial history.

RESULTS

Saccadic reaction time was normal, but patients required more time to inhibit a planned saccade. The latency of the inhibitory process was associated with the severity of negative symptoms and poorer occupational functioning. Both groups slowed down significantly after correctly cancelled and erroneously noncancelled stop signal trials, but patients slowed down more than control subjects after correctly inhibited saccades.

CONCLUSIONS

These results suggest that SZ is associated with a difficulty in inhibiting planned movements and an inflated response adjustment effect after inhibiting a saccade. Furthermore, behavioral results are consistent with potential abnormalities in frontal and supplementary eye fields in patients with SZ.

Response switching in schizophrenia patients and healthy subjects: effects of the inter-response interval

Schizophrenia patients show impaired saccadic response switching, pointing to action control deficits at the level of response selection. Previous studies on healthy subjects suggested that response switch effects might decrease if the prior response is longer ago, reflecting a slow dissipation of the response program persisting from the previous trial. The present study aimed at directly investigating whether response switch effects in schizophrenia patients and healthy subjects depend on the inter-response interval (IRI). Effects of response switching on pro- and antisaccade performance were analyzed in 19 schizophrenia patients and 19 healthy controls at 3 different IRIs (2,500, 3,000, 4,000 ms). Response switch effects of healthy subjects did not vary with the IRI, suggesting that the previous response program persists as long as no contrary response program is activated. In schizophrenia, response switch deficits were replicated at an IRI of 3,000 ms, whereas at IRIs of 2,500 and 4,000 ms, effects of response switching did not significantly differ from healthy subjects. This might suggest that there is a specific IRI range particularly sensitive to response switch deficits in schizophrenia. However, effects of response switching at different IRIs remain to be consolidated.

A new behavioral test for assessment of drug effects on attentional performance and its validity in cynomolgus monkeys

The assessment of drug effects on attention is important in non-clinical pharmacology, for both evaluation of safety and therapeutic efficacy of medicinal products. In the present study, we have developed a two-lever choice behavioral test to assess drug effects on attentional performance in monkeys. In each trial of this experiment, one of two lamps in front of a monkey was randomly illuminated for a brief period of time and the monkey was required to press a lever beneath the lamp 30 times to obtain a food reward. The percentage of correct responses, response latency of correct choice responses and response speed were measured. Using this test, we examined the effects of three sedative drugs, diazepam (0.25, 1 and 4 mg/kg, i.g.), ethanol (0.5, 1 and 2 g/kg, i.g.), and pentobarbital (0.25, 1 and 4 mg/kg, i.v.). Diazepam and pentobarbital lengthened response latency without significantly affecting the percentage of correct responses, response and response speed, suggesting selective disruptive effects on attentional performance. In contrast, ethanol at the high dose tested caused deterioration in all three measurements, which is thought to reflect a general sedative effect including motor impairment as reflected by lengthening response speed. It is suggested that the present behavioral test method could detect drug effects on attentional performance in monkeys and could be a useful tool for safety assessment in drug development.

Saccade generation and suppression in schizophrenia: effects of response switching and perseveration

Poor antisaccade performance is a reliable index of action control deficits in schizophrenia. To further elucidate the underlying cognitive impairments, the current study aimed to confirm effects of switching the response direction on saccadic performance and to investigate whether response switch effects relate to perseveration. Fourteen schizophrenia patients and 14 healthy controls performed sequences of 1 to 3 simple volitional saccades to one direction and a subsequent volitional saccade with distractor to the same or the opposite direction. Response switches increased error rates in schizophrenia if they followed 3 saccades to the opposite side, suggesting that response switching affects performance on conditions of strong persisting response programs. The increase of response switch error rates with multiple repetitions of the prior response points to a relationship between perseveration and response selection.