title: Mean signal and response time influences on multivoxel signals of contextual retrieval in the medial temporal lobe.
abstract: BACKGROUND
  The medial temporal lobe supports integrating the "what," "where," and "when" of an experience into a unified memory. However, it remains unclear how representations of these contextual features are neurally encoded and distributed across medial temporal lobe subregions.
  
  
  METHODS
  This study conducted functional magnetic resonance imaging of the medial temporal lobe, while participants retrieved pair, spatial, and temporal source memories. Multivoxel classifiers were trained to distinguish between retrieval conditions before and after correction for mean signal and response times, to more thoroughly characterize the multivoxel signal associated with memory context.
  
  
  RESULTS
  Activity in perirhinal and parahippocampal cortex dissociated between memory for associated items and memory for their spatiotemporal context, and hippocampal activity was linked to memory for spatial context. However, perirhinal and hippocampal classifiers were, respectively, driven by effects of mean signal amplitude and task difficulty, whereas the parahippocampal classifier survived correction for these effects.
  
  
  CONCLUSIONS
  These findings demonstrate dissociable coding mechanisms for episodic memory context across the medial temporal lobe, and further highlight a critical distinction between multivoxel representations driven by spatially distributed activity patterns, and those driven by the regional signal.
authors: Department of Neurosciences, University of California, San Diego 9500 Gilman Dr., La Jolla, California, 92093-0949.
authors: Emilie T
authors: ET
authors: Reas
authors: Department of Neurosciences, University of California, San Diego 9500 Gilman Dr., La Jolla, California, 92093-0949 ; Department of Radiology, University of California, San Diego 9500 Gilman Dr., La Jolla, California, 92093-0949.
authors: James B
authors: JB
authors: Brewer
mesh_terms: D000328:Adult; D001931:Brain Mapping; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D008568:Memory / Q000502:physiology*; D010775:Photic Stimulation; D013702:Temporal Lobe / Q000502:physiology*; D055815:Young Adult
keywords: Episodic memory; fMRI; medial temporal lobe; multivoxel pattern analysis; retrieval
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