Differences between target and non-target probe processing--combined evidence from fMRI, EEG and fMRI-constrained source analysis.
Previous studies reported heterogeneous findings in working memory tasks when examining differences between correct recognition (targets) and correct rejection (non-targets). In the present study, twenty human participants completed a delayed match-to-sample task in two separate functional magnetic resonance imaging (fMRI) and electroencephalography (EEG) sessions. Targets and non-target items were presented at different within-trial positions. We used fMRI-constrained source analysis to investigate the spatio-temporal neuronal dynamics of probe processing. Probe type-related differences were modulated by position in the trial or by the ratio of target stimuli to non-target stimuli at different trial positions. fMRI-constrained source analysis revealed a temporal pattern of source activities starting in occipital and temporal brain regions, followed by a simultaneous engagement of parietal and frontal brain regions and a later activity of a source in pre-SMA (supplementary motor area). Source activities demonstrated a specific involvement of left fusiform gyrus in the non-target condition compared to the target condition that might be associated with mental imagination of the target stimulus during non-target probe processing. Source activities, furthermore, showed the anterior cingulate to be particularly involved in target processing compared to non-target processing before response execution and the pre-SMA before and during response execution. These brain areas appear to be activated in different stages of conflict managing operations due to a lower stimulus frequency of target trials compared to non-target trials at different target positions in the present design.
Department of Neuropsychology and Behavioral Neurobiology, Center for Cognitive Sciences (ZKW), University of Bremen, Bremen, Germany; Center for Advanced Imaging (CAI), University of Bremen, Bremen, Germany. Electronic address: galashan@uni-bremen.de.
Daniela
D
Galashan
Department of Neuropsychology and Behavioral Neurobiology, Center for Cognitive Sciences (ZKW), University of Bremen, Bremen, Germany; Center for Advanced Imaging (CAI), University of Bremen, Bremen, Germany; Department of Neurology, Otto-von-Guericke University, Magdeburg, Germany. Electronic address: fehr@uni-bremen.de.
Thorsten
T
Fehr
Department of Neuropsychology and Behavioral Neurobiology, Center for Cognitive Sciences (ZKW), University of Bremen, Bremen, Germany; Center for Advanced Imaging (CAI), University of Bremen, Bremen, Germany. Electronic address: manfred.herrmann@uni-bremen.de.
Manfred
M
Herrmann
D000328:Adult; D002540:Cerebral Cortex / Q000502:physiology*; D004569:Electroencephalography; D005071:Evoked Potentials / Q000502:physiology*; D056344:Executive Function / Q000502:physiology*; D005260:Female; D059907:Functional Neuroimaging / Q000379:methods*; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008570:Memory, Short-Term / Q000502:physiology*; D011597:Psychomotor Performance / Q000502:physiology*; D055815:Young Adult
DMTS task; ERP; Match; P300; RT; Working memory