Learning-related changes in brain activity following errors and performance feedback in schizophrenia

Abstract

In previous studies of self-monitoring in schizophrenia, patients have exhibited reductions in the amplitude of the error-related negativity (ERN), a component of the event-related brain potential (ERP) elicited most prominently immediately following the execution of incorrect responses. In the current study, we examined the ERN and a related component, the feedback negativity (FBN) in 26 schizophrenia outpatients and 27 psychiatrically healthy comparison subjects during a probabilistic learning task in which participants could learn stimulus-response pairs by attending to feedback indicating response accuracy. The validity of the feedback varied in three conditions. In one condition, accuracy feedback was entirely consistent (i.e., a left response to one of the stimuli in this condition was always correct and a right response was always incorrect). In the second condition, feedback was valid on only 80% of the trials, and in the third condition, accuracy feedback was random. Changes in ERP amplitudes accompanying learning of stimulus-response pairs were examined. Schizophrenia patients exhibited reduced ERN amplitude compared to healthy subjects in all conditions. This finding extends the previously reported impairment to include disruption of self-monitoring on a task in which participants learn stimulus-response mappings by trial and error, rather than being told the mappings explicitly. Schizophrenia patients also exhibited reduced FBN amplitude compared to healthy subjects in the 100% condition during early trials when the feedback was essential for accurate performance. These findings suggest that reward-related brain activity is weakened in schizophrenia, perhaps reflecting diminished sensitivity to whether ongoing events are better or worse than expected.

Figure 1

Response-locked waveforms for correct and incorrect responses occurring before (“early”) and after (“late”) the behavioral learning threshold was met. Data shown in waveforms are from FCz channel. Incorrect-correct difference activity on post-learning trials at the latency of peak RN activity is shown on topographical maps.

Figure 2

Mean RN amplitude for correct and incorrect responses occurring before (“early”) and after (“late”) the behavioral learning threshold was met. Data shown are from FCz channel. Error bars indicate standard error.

Figure 3

Feedback-locked waveforms for correct and incorrect feedback occurring before (“early”) and after (“late”) the behavioral learning threshold was met. Data shown in waveforms are from FCz channel. Incorrect-correct difference activity on pre-learning trials at the latency of peak FBN activity is shown on topographical maps.

Figure 4

Mean FBN amplitude for correct and incorrect feedback occurring before (“early”) and after (“late”) the behavioral learning threshold was met. Data shown are from FCz channel. Error bars indicate standard error.