title: Granger causality analysis reveals distinct spatio-temporal connectivity patterns in motor and perceptual visuo-spatial working memory.
abstract: We employed spectral Granger causality analysis on a full set of 56 electroencephalographic recordings acquired during the execution of either a 2D movement pointing or a perceptual (yes/no) change detection task with memory and non-memory conditions. On the basis of network characteristics across frequency bands, we provide evidence for the full dissociation of the corresponding cognitive processes. Movement-memory trial types exhibited higher degree nodes during the first 2 s of the delay period, mainly at central, left frontal and right-parietal areas. Change detection-memory trial types resulted in a three-peak temporal pattern of the total degree with higher degree nodes emerging mainly at central, right frontal, and occipital areas. Functional connectivity networks resulting from non-memory trial types were characterized by more sparse structures for both tasks. The movement-memory trial types encompassed an apparent coarse flow from frontal to parietal areas while the opposite flow from occipital, parietal to central and frontal areas was evident for the change detection-memory trial types. The differences among tasks and conditions were more profound in α (8-12 Hz) and β (12-30 Hz) and less in γ (30-45 Hz) band. Our results favor the hypothesis which considers spatial working memory as a by-product of specific mental processes that engages common brain areas under different network organizations.
authors.affiliation: School of Applied Mathematics and Physical Sciences, National Technical University of Athens Athens, Greece.
authors.forename: Foteini
authors.initials: F
authors.lastname: Protopapa
authors.affiliation: School of Applied Mathematics and Physical Sciences, National Technical University of Athens Athens, Greece.
authors.forename: Constantinos I
authors.initials: CI
authors.lastname: Siettos
authors.affiliation: Neurology Department, National and Kapodistrian University of Athens, Aeginition Hospital Athens, Greece.
authors.forename: Ioannis
authors.initials: I
authors.lastname: Evdokimidis
authors.affiliation: Laboratory of Sensorimotor Control, University Mental Health Research Institute Athens, Greece ; Psychiatry Department, National and Kapodistrian University of Athens, Aeginition Hospital Athens, Greece.
authors.forename: Nikolaos
authors.initials: N
authors.lastname: Smyrnis
keywords: EEG; Granger causality; change detection; functional connectivity; movement planning