[Abstract Title]. - Society for Neuroscience

Topic: F.01.f. Working memory
Support: Drexel University Critical Research Fellowship
Title: Coherent oscillatory networks supporting short-term memory retention
Authors: *L. PAYNE, J. KOUNIOS;
Drexel Univ., Philadelphia, PA
Abstract: Recent research suggests that short-term memory (STM) is not simply a result of
neural activity within prefrontal, parietal, and temporal regions, but that it is an emergent
property of synchronous oscillations between these distant foci of activity. According to this
scenario, top-down activation, reflected by frontal-midline theta-band (4-8 Hz)
electroencephalogram (EEG) oscillations, is thought to strengthen the activation of a memory set
during STM retention. In addition, the amplitude of posterior alpha-band (8-13 Hz) oscillations
during STM retention is thought to reflect a sensory-gating mechanism that protects fragile STM
activations from interference by bottom-up visual inputs. The present study examined large-scale
network connectivity during STM retention by computing EEG wavelet coherence during the
retention period of a modified Sternberg task using visually-presented letters as stimuli. In each
trial, healthy, adult, participants judged whether a probe was one of the memory set which
consisted of 2, 4, or 6 consonants. Spectral analysis of the 2.8 s retention period revealed a peak
in alpha frequency over parietal-occipital regions that systematically increased with the number
of items held in STM. Alpha coherence increased between posterior-midline electrode PZ and
left-lateralized parietal-temporal sites only between set sizes 2 and 4. Although there was no
change in theta power, coherence in the theta band between frontal-midline electrode FZ and left
left-lateralized parietal-temporal sites strengthened as set size increased from 2 to 4 to 6
consonants. Interestingly, alpha coherence between PZ and left temporal electrode T7 increased
from 2 to 4 consonants, and then FZ/T7 theta coherence increased between 4 and 6 consonants.
Analysis of T7 theta coherence revealed enhancement of a frontal-temporal network with
simultaneous attenuation of temporal-posterior interactions. These findings support the view that
interactions between frontal-midline cortex and left temporal/parietal cortex serve to strengthen
the memory set. Furthermore, these results suggest that direct communication between posterior
midline cortex and left temporal/parietal cortex coordinates sensory gating which prevents
potential interference from bottom-up processes.
Disclosures: L. Payne , None; J. Kounios, None.
Poster
288. Working Memory: Disorders, Genes and Connectivity
Time: Sunday, November 16, 2008, 1:00 pm - 5:00 pm