Contextual processing deficits in Parkinson's disease: the role of the frontostriatal system.
OBJECTIVE
We investigated the role of the frontostriatal system in contextual processing, by examining neural correlates of local contextual processing in Parkinson's disease (PD). Local context was defined as the occurrence of a short predictive series of visual stimuli occurring before delivery of a target event.


METHODS
EEG was recorded in eight PD patients and eight controls. Recording blocks consisted of targets preceded by randomized sequences of standards and by sequences including a predictive sequence signaling the occurrence of a subsequent target event. Subjects pressed a button in response to targets. Peak P3b amplitude and latency were evaluated for targets after predictive and non-predictive sequences.


RESULTS
Behavioral and electrophysiological measures showed that controls processed predicted and random targets differentially, while PD patients processed these similarly. Reaction times were shorter for predictable than for random targets in controls but not in patients. PD patients failed to generate the expected P3b latency shift between predicted and random targets, which is observed in controls.


CONCLUSIONS
These findings show that predictive local context effects on target detection are altered in PD patients.


CONCLUSIONS
The findings suggest a key role for the frontostriatal system in contextual processing.
Fogelson
Noa
N
Department of Psychology, University of A Coruña, La Coruña, Spain. Electronic address: nfogelson@udc.es.
Fernandez-Del-Olmo
Miguel
M
Department of Physical Education, University of A Coruña, La Coruña, Spain.
Santos-Garcia
Diego
D
Department of Neurology, Hospital A. Marcide, Ferrol, Spain.
D000368:Aged; D001288:Attention / Q000502:physiology; D003342:Corpus Striatum / Q000503:physiopathology*; D004569:Electroencephalography; D055724:Electrophysiological Phenomena; D005071:Evoked Potentials / Q000502:physiology; D005260:Female; D005625:Frontal Lobe / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D010300:Parkinson Disease / Q000503:physiopathology* / Q000523:psychology*; D010775:Photic Stimulation; D011597:Psychomotor Performance / Q000502:physiology; D011930:Reaction Time / Q000502:physiology; D014793:Visual Cortex / Q000503:physiopathology