Task-switching in schizophrenia: active switching costs and passive carry-over effects in an antisaccade paradigm

Abstract

It has been hypothesized that impaired task-switching underlies some of the behavioural deficits in schizophrenia. However, task-switching involves many cognitive operations. In this study our goal was to isolate the effects on latency and accuracy that can be attributed to specific task-switch processes, by studying the inter-trial effects in blocks of randomly mixed prosaccades and antisaccades. By varying the preparatory interval between an instructional cue and the target, we assessed the costs of both (1) an active reconfiguration process that was triggered by the cue, and (2) passive carry-over effects persisting from the prior trial. We tested 15 schizophrenic subjects and 14 matched controls. A very short preparatory interval increased error rates and saccadic latencies in both groups, but more so in schizophrenia, suggesting difficulty in rapidly activating saccadic goals. However, the contrast between repeated and switched trials showed that the costs of task switching in schizophrenia were not significantly different from the controls, at either short or long preparatory intervals, for both antisaccades and prosaccades. These results confirm prior observations that passive carry-over effects are normal in schizophrenia, and show that active reconfiguration is also normal in this disorder. Thus problems with executive control in schizophrenia may not affect specific task-switching operations.

Consider the context: Blocked versus interleaved presentation of antisaccade trials

“…Our findings show no task-switch effects during the long-lead condition, but anti-saccade responses in the simultaneous condition showed a task-switch cost. This same effect was also observed by Barton et al (2006), Greenzang et al (2007), and Weber (1995), who noted a task-switch cost at short cue to target intervals (200 ms). Studies reporting task-switch benefits for anti-saccades (Barton et al, 2002, 2006; Cherkasova et al, 2002; Manoach et al, 2002) used a considerably longer cue-to- target interval (two sec) than we used here.…”

Cognitive effort avoidance and detection in people with schizophrenia

“…This task was administered on a different day from the Demand Selection Task. This condition was administered as a type of control as we anticipated that subjects who experienced greater switching costs might be more effort averse, and further expected that patients, as a group, might show increased switching costs (although the evidence in the literature on this point is conflicting; see Greenzang, Manoach, Goff, Barton, 2007; Ravizza, Moua, Long, Carter, 2010; Wylie, Clark, Butler, Javitt, 2010). …”

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

“…As a result of impaired dorsolateral PFC activity prior to antisaccades, relatives may rely more heavily upon orbital PFC than control subjects in an attempt to inhibit prepotent reflexive saccades. Recent work has provided evidence that a failure of schizophrenia patients to inhibit reflexive saccades (Manoach, Lindgren, Cherkasova, Goff, Halpern, et al, 2002) and not deficient switching between tasks (Greenzang, Manoach, Goff, & Barton, 2007) leads to poor antisaccade performance. We found schizophrenia patients had larger frontal polar potentials than controls from 120 to 0 ms prior to step prosaccade potentials.…”