[Abstract Title]. - Society for Neuroscience

288. Working Memory: Disorders, Genes and Connectivity
Time: Sunday, November 16, 2008, 1:00 pm - 5:00 pm
Program#/Poster#: 288.17/RR24
Topic: F.01.f. Working memory
Support: CIHR Grant 64431
MSFHR Scholar Award
Title: Constrained principal component analysis reveals functionally connected load-dependent
neural systems involved multiple phases of working memory
Authors: S. WEINSTEIN, E. FEREDOES, P. METZAK, E. T. C. NGAN, *T. S.
WOODWARD;
Psychiatry, Univ. British Columbia, Vancouver, BC, Canada
Abstract: Recent cognitive neuroscience models of working memory have posited that working
memory is an "emergent" behavior in which, when behaviorally necessary, a set of "top-down"
control processes are recruited to maintain or manipulate information in the same areas that
represent that information under non-memory conditions. As a result, multivariate approaches to
statistical analyses of fMRI data are becoming increasingly necessary in order to visualize
connectivity between anatomically separate control and perceptual/sensory/action brain regions.
Moreover, to test a central hypothesis of the model -- the same regions which encode the
information also maintain the information -- requires consideration of multiple task stages
together rather than modeling each separately.
We introduce a novel application of constrained principal component analysis (cPCA) based on
finite impulse responses (FIRs) which can provide functionally connected neural networks that
can be temporally mapped onto different task stages. We applied this cPCA approach to a verbal
delayed recognition task that varied the factor of memory load. Of the three extracted
components, two were involved in both the encoding and delay stage, and the third was involved
in both the delay and response stages. The encoding/delay functional networks were dominated
by activation in occipital, dorsal anterior cingulate, and sensori-motor cortical regions, and
deactivation in bilateral primary auditory cortex and "default network" regions. The
delay/response functional network was dominated by activations in dorsal anterior cingulate,
dorsolateral prefrontal cortex and left parietal cortex, with deactivations in the "default network"
regions and visual cortex. We also observed sensitivity of all components for load, although only
those involved in the encoding and delay phases reached significance.
Our novel approach provides maps of functionally connected neural networks in addition to