Reduced top-down influences in contour detection in schizophrenia.
BACKGROUND
Chronic schizophrenia patients have previously demonstrated performance deficits in contour integration tasks. The purpose of this study was to investigate whether schizophrenia patients, spanning a range of illness severity, would demonstrate responsiveness to manipulations that recruit top-down processing strategies involving learning and sequencing effects in a contour integration task.


METHODS
We administered a contour integration test over four consecutive days and in two different presentation conditions each day. In one condition, the stimuli were administered in order of increasing difficulty, and in the other they were presented in random order. The order in which these two conditions were presented was counterbalanced across days and participants. In addition, a nonschizophrenia psychotic disorders control group was included to determine if past findings of a contour integration deficit in schizophrenia could be replicated in the presence of a symptomatically similar control group.


RESULTS
All groups demonstrated similar learning curves across the four days and generally similar overall levels of performance, with the exception of the group of the most chronic schizophrenia patients. In addition, the order in which the stimuli were presented to subjects affected their performance, with higher scores achieved for all groups in the condition where the stimuli were presented in increasing order of difficulty. Interaction effects revealed that the effects of order presentation were greater for nonpatient than for psychotic patients.


CONCLUSIONS
These data are further evidence that perceptual organization impairments in schizophrenia are illness severity-related, and that schizophrenia patients as a whole are less sensitive to top-down manipulations in this type of task.
Weill Medical College of Cornell University, White Plains, NY, USA. Steven.Silverstein@att.net
Steven M
SM
Silverstein
Michi
M
Hatashita-Wong
Lindsay S
LS
Schenkel
Sandra
S
Wilkniss
Ilona
I
Kovács
Akos
A
Fehér
Thomas
T
Smith
Claudia
C
Goicochea
Peter
P
Uhlhaas
Kelly
K
Carpiniello
Adam
A
Savitz
D000328:Adult; D014150:Antipsychotic Agents / Q000627:therapeutic use; D002908:Chronic Disease; D005260:Female; D005556:Form Perception; D006801:Humans; D008297:Male; D010364:Pattern Recognition, Visual; D010468:Perceptual Disorders / Q000175:diagnosis* / Q000209:etiology*; D012559:Schizophrenia / Q000150:complications* / Q000188:drug therapy; D012720:Severity of Illness Index
D014150:Antipsychotic Agents