Prior demonstrations of impaired attentional control in schizophrenia focused on conditions in which top-down control is needed to overcome prepotent response tendencies. Attentional control over stimulus processing has received little investigation. Here we test whether attentional control is impaired during working memory encoding when salient distractors compete with less salient task-relevant stimuli.
Patients with schizophrenia (n=28) and healthy controls (HC, n=25) performed a visuospatial working memory paradigm in which half of the to-be-encoded stimuli flickered to increase their salience. After a 2-s delay, stimuli reappeared and participants had to decide whether or not a probed item had shifted location.
In the Unbiased condition where flickering and non-flickering stimuli were equally likely to be probed, both groups displayed a trend towards better mesmory for the flickering items. In the Flicker-bias condition in which the flickering stimuli were likely to be probed, both groups displayed a robust selection advantage for the flickering items. However, in the Nonflicker-bias condition in which the non-flickering stimuli were likely to be probed, only HC showed selection of the non-flickering items. Patients displayed a trend toward preferential memory for the flickering items, as in the unbiased condition.
Both groups were able to select salient over non-salient stimuli, but patients with schizophrenia were unable to select non-salient over salient stimuli, consistent with impairment in the effortful control of attention. These findings demonstrate the generality of top-down control failure in schizophrenia in the face of bottom-up competition from salient stimuli as with prepotent response tendencies.