Working memory in schizophrenia: behavioral and neural evidence for reduced susceptibility to item-specific proactive interference.
BACKGROUND
Susceptibility to item-specific proactive interference (PI) contributes to interindividual differences in working memory (WM) capacity and complex cognition relying on WM. Although WM deficits are a well-recognized impairment in schizophrenia, the underlying pathophysiological effects on specific WM control functions, such as the ability to resist item-specific PI, remain unknown. Moreover, opposing hypotheses on increased versus reduced PI susceptibility in schizophrenia are both justifiable by the extant literature.


METHODS
To provide first insights into the behavioral and neural correlates of PI-related WM control in schizophrenia, a functional magnetic resonance imaging experiment was conducted in a sample of 20 patients and 20 well-matched control subjects. Demands on item-specific PI were experimentally manipulated in a recent-probes task (three runs, 64 trials each) requiring subjects to encode and maintain a set of four target items per trial.


RESULTS
Compared with healthy control subjects, schizophrenia patients showed a significantly reduced PI susceptibility in both accuracy and latency measures. Notably, reduced PI susceptibility in schizophrenia was not associated with overall WM impairments and thus constituted an independent phenomenon. In addition, PI-related activations in inferior frontal gyrus and anterior insula, typically assumed to support PI resistance, were reduced in schizophrenia, thus ruling out increased neural efforts as a potential cause of the patients' reduced PI susceptibility.


CONCLUSIONS
The present study provides first evidence for a diminished vulnerability of schizophrenia patients to item-specific PI, which is presumably a consequence of the patients' more efficient clearing of previously relevant WM traces and the accordingly reduced likelihood for item-specific PI to occur.
Department of Neurology, University Medical Center Freiburg, Freiburg; Freiburg Brain Imaging Center, University of Freiburg, Freiburg; BrainLinks-BrainTools Cluster of Excellence, University of Freiburg, Freiburg, Germany. Electronic address: christoph.kaller@uniklinik-freiburg.de.
Christoph P
CP
Kaller
Department of Neurology, University Medical Center Freiburg, Freiburg; Freiburg Brain Imaging Center, University of Freiburg, Freiburg; Biological and Personality Psychology, Department of Psychology, University of Freiburg, Freiburg.
Sandra V
SV
Loosli
Medical Psychology and Medical Sociology, University Medical Center Mainz, Mainz.
Benjamin
B
Rahm
Department of Neurology, University Medical Center Freiburg, Freiburg; Freiburg Brain Imaging Center, University of Freiburg, Freiburg.
Astrid
A
Gössel
Center for Psychiatry, Emmendingen.
Stephan
S
Schieting
Department of Neurology, University Medical Center Freiburg, Freiburg; Department of Psychiatry , University Medical Center Freiburg, Freiburg.
Tobias
T
Hornig
Freiburg Brain Imaging Center, University of Freiburg, Freiburg; Medical Physics, Department of Radiology, University Medical Center Freiburg, Freiburg; BrainLinks-BrainTools Cluster of Excellence, University of Freiburg, Freiburg, Germany.
Jürgen
J
Hennig
Freiburg Brain Imaging Center, University of Freiburg, Freiburg; Department of Psychiatry , University Medical Center Freiburg, Freiburg.
Ludger
L
Tebartz van Elst
Department of Neurology, University Medical Center Freiburg, Freiburg; Freiburg Brain Imaging Center, University of Freiburg, Freiburg; BrainLinks-BrainTools Cluster of Excellence, University of Freiburg, Freiburg, Germany.
Cornelius
C
Weiller
Department of Neurology, University Medical Center Freiburg, Freiburg; Freiburg Brain Imaging Center, University of Freiburg, Freiburg.
Michael
M
Katzev
D000293:Adolescent; D000328:Adult; D001921:Brain / Q000503:physiopathology*; D001931:Brain Mapping; D002755:Choice Behavior / Q000502:physiology; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008569:Memory Disorders / Q000150:complications / Q000503:physiopathology*; D008570:Memory, Short-Term / Q000502:physiology*; D008875:Middle Aged; D012559:Schizophrenia / Q000150:complications / Q000503:physiopathology*; D055815:Young Adult
Cognitive control; functional neuroimaging; prefrontal cortex; proactive interference; schizophrenia; working memory