Participants

1. Negative BOLD and Aging: An fMRI InvestigationK.M. McGregor1,2, K.D. White1,2,3, M. Benjamin1,3, W.K. Berg2, I. Fischler2, J. Craggs3, B. Crosson1,3 1Malcom Randall VA RR&D Brain Rehabilitation Research Center; 2Department of Psychology and 3Department of Clinical and Health Psychology, University of Florida, Gainesville, Florida This poster is available on the Web at www.BIRC.phhp.ufl.edu Background Method: Analysis Results: HRF Analysis • A negative BOLD response (NBR) appears as a “mirror image” of a positive BOLD response and is thought to indicate a decrease in metabolic/neuronal activity (Shmuel et al., 2006; Stefanovic et al., 2004) • Recent research has shown improved reliability in evoking NBR in the visual (Shmuel et al., 2002; Smith et al., 2004) and motor (Hamzei et al., 2002; Hummel et al., 2004; Newton et al., 2005) cortices • The effects of aging upon the BOLD signal are not well known. Further, few studies, if any, have investigated age related differences on the NBR • The current investigation compared BOLD response in four regions of interest across older and younger adults using a methodology previously shown to evoke a NBR in the primary motor cortex • Representations of the estimated hemodynamic response function averages of the most highly active voxel and four of its suprathreshold contiguous neighbors for older and younger adults during learned response execution. • Each of the four graphs shows a different region of interest (clockwise from top left: L M1, LSMA, RSMA, RM1). • Ordinate values are the magnitude of the hemodynamic response function (HRF) shown against time (in TR units) relative to the response event. • Large positive BOLD responses can be seen for older and younger adults in L M1. • Moderate positive BOLD responses are shown for each age group for SMA bilaterally. • R M1, younger adults show a moderate negative BOLD response while the older adults show a large positive BOLD response. • Deconvolution analysis using AFNI software using F-statistic for determination of activation • Selected most highly active voxel with four contiguous, suprathreshold (F>3.5, p<.001) neighboring voxels in four regions of interest • Right & left primary motor cortex (R & L M1) • Right & left supplementary motor cortex (R & L SMA) • Output estimate values of hemodynamic response function (HRF) from each of the voxel (N = 30 voxel: 5 voxels per region, 4 regions) • Compared age groups and regions on estimates of hemodynamic response function using split plot ANOVA (2 x 4 x 16) Participants Results: Behavioral Performance • All right handed & free from neurological/psychiatric disorder Results: HRF Examples Method Results: Means • Task: Unimanual (right hand) learned movement response • Participants trained to perform a timed 12 movement button press sequence • Three training phases (10 consecutive correct sequence executions required for advancement to next stage) • Familiarity: Self-paced sequence execution with visual reference • Memorization: Self-paced sequence execution with no visual reference • Cued: Externally paced sequence execution with no visual reference • Scanning: • Go/No Go paradigm (Go conditions evaluated for this analysis) • 40 Go stimulus presentations • 6 runs of 234 images (6 min 41 sec per run) • fMRI parameters: • Siemens Allegra (head-only) @ 3T • Axial plane gradient echo EPI (TR=1700ms; TE=25ms; FOV=240mm; 32 slices; 64x64 matrix) • Normalized group means for a) older adults and b) younger adults during GO response after area-under-the-curve analysis of estimated HRF. • Shown here are examples of activity in RM1 during GO conditions in an older adult – s01 (a) and a younger adult – s12 (b) • Images (c ) and (d) show the HRF estimates of the maximally active voxel in RM1 (bottom HRF) with four contiguous suprathreshold neighbors Yellow indicates large positive area, orange indicates moderate positive area, and blue indicates negative (below baseline) area c) a) a) b) Conclusions Red indicates p < 0.01, orange indicates p<0.005, yellow indicates p< 0.0001 . • During the current unimanual button press task, Older adults appear to show bilateral positive BOLD signal in M1 while younger adults show moderate negative BOLD in ipsilateral M1 • Results could indicate aging related changes in interhemispheric inhibition d) b)