Failure of schizophrenia patients to overcome salient distractors during working memory encoding.
BACKGROUND
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.


METHODS
Patients with schizophrenia (n = 28) and healthy control subjects (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-second delay, stimuli reappeared and participants had to decide whether or not a probed item had shifted location.


RESULTS
In the unbiased condition where flickering and nonflickering stimuli were equally likely to be probed, both groups displayed a trend toward better memory 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 nonflickering stimuli were likely to be probed, only healthy control subjects showed selection of the nonflickering items. Patients displayed a trend toward preferential memory for the flickering items, as in the unbiased condition.


CONCLUSIONS
Both groups were able to select salient over nonsalient stimuli, but patients with schizophrenia were unable to select nonsalient 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.
Hahn
Britta
B
Maryland Psychiatric Research Center, University of Maryland School of Medicine, Baltimore, Maryland 21228, USA.
Robinson
Benjamin M
BM
Kaiser
Samuel T
ST
Harvey
Alexander N
AN
Beck
Valerie M
VM
Leonard
Carly J
CJ
Kappenman
Emily S
ES
Luck
Steven J
SJ
Gold
James M
JM
D000328:Adult; D000704:Analysis of Variance; D001289:Attention Deficit Disorder with Hyperactivity / Q000209:etiology*; D005260:Female; D005425:Flicker Fusion / Q000502:physiology; D006801:Humans; D008297:Male; D008570:Memory, Short-Term / Q000502:physiology*; D008875:Middle Aged; D009483:Neuropsychological Tests; D010775:Photic Stimulation / Q000379:methods; D011930:Reaction Time / Q000502:physiology; D012559:Schizophrenia / Q000150:complications*; D012565:Schizophrenic Psychology; D013028:Space Perception; D013223:Statistics as Topic; D055815:Young Adult