title: Coherence between fMRI time-series distinguishes two spatial working memory networks.
abstract: Widespread and distributed brain regions are thought to form networks that together support working memory. We recently demonstrated that different cortical areas maintain relatively different codes across a memory delay (Curtis et. al., J Neurosci, 2004; 24:3944-3952). The frontal eye fields (FEF), for example, were more active during the delay when the direction of the memory-guided saccade was known compared to when it was not known throughout the delay. Other areas showed the opposite pattern. Despite these task-dependent differences in regional activity, we could only assume but not address the functional interactions between the identified nodes of the putative network. Here, we use a bivariate technique, coherence, to formally characterize functional interactions between a seed region and other brain areas. We find that the type of representational codes that are being maintained in working memory biases frontal-parietal interactions. For example, coherence between FEF and other oculomotor areas was greater when a motor representation was an efficient strategy to bridge the delay period. However, coherence between the FEF and higher-order heteromodal areas, e.g., dorsolateral prefrontal cortex, was greater when a sensory representation must be maintained in working memory.
authors.affiliation: Department of Psychology and Center for Neural Science, New York University, NY 10003, USA. clayton.curtis@nyu.edu
authors.forename: Clayton E
authors.initials: CE
authors.lastname: Curtis
authors.forename: Felice T
authors.initials: FT
authors.lastname: Sun
authors.forename: Lee M
authors.initials: LM
authors.lastname: Miller
authors.forename: Mark
authors.initials: M
authors.lastname: D'Esposito
mesh_terms: D000293:Adolescent; D000328:Adult; D000465:Algorithms; D003463:Cues; D017352:Echo-Planar Imaging; D005133:Eye Movements / Q000502:physiology; D005260:Female; D005403:Fixation, Ocular / Q000502:physiology; D006801:Humans; D007090:Image Interpretation, Computer-Assisted; D008279:Magnetic Resonance Imaging; D008297:Male; D008570:Memory, Short-Term / Q000502:physiology*; D009415:Nerve Net / Q000502:physiology*; D010100:Oxygen / Q000097:blood; D017397:Prefrontal Cortex / Q000502:physiology; D013028:Space Perception / Q000502:physiology*
chemical_list: D010100:Oxygen