Society for Neuroscience Washington, D.C.
Nov. 12-16, 2005
F.Haist; T.Jung; J.Duann; M.Adamo; A.Vankov; S.Makeig , Department of Cognitive Science and Swartz Center for Computational Neuroscience, Institute for Neural Computation University of California San Diego, La Jolla CA, USA; Psychology, Univ. of Toronto, Toronto, ON, Canada
NEURODYNAMICALLY DEFINED MEMORY SYSTEMS FROM SIMULTANEOUS FMRI AND EEG MEASURES
Human memory depends on coordinated activity across discrete brain regions organized into information-processing systems. Yet, defining the organization of brain memory systems from regional activations obtained in functional imaging studies remains a challenge. Here, we describe a method for defining memory systems from functional magnetic resonance imaging (FMRI) and 71-channel electroencephalographic (EEG) data recorded simultaneously. Six healthy young adults participated in a verbal paired-associate test. Each studied 72 pairs of highly associated words (flower-rose) and 72 low associate pairs (army-table) prior to scanning. During testing, subjects were shown the first word of the pair for 1500 ms and encouraged to recollect the associated word. A second word was then shown and subjects made a yes/no decision as to whether it completed the studied pair. Subjects obtained a mean of 82% correct recognition. Traditional parametric analyses of the FMRI data identified several regions of activity, including a large region in the left prefrontal cortex (L-PFC). We demonstrate that independent components analysis (ICA) was able to identify two components capturing the activity in the L-PFC. A group analysis of these components revealed that activity in the left inferior frontal gyrus (BA 45; Brocas area) was linked to activity in left superior temporal gyrus (BA 22; Wernickes area), revealing a language-related co-activation in paired-associate recollection. Activity in left middle frontal gyrus (BA 9) was co-activated with a region in right middle frontal gyrus. These findings, merged with measures of temporal and spectral EEG modulations/perturbations can provide a convergent test for systems defined by BOLD ICA, and a more complete multi-resolution 4-D (space+time) description of memory task-related activities. The technical challenges of simultaneous EEG/FMRI acquisition will be discussed.