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Repeatability of Motor and Working-Memory Tasks in Healthy Older Volunteers: Assessment at Functional MR Imaging¹

¹ From the Depts of Medical Physics (I.M.), Psychiatry (E.S., K.P.E., E.J.R.), Psychology (I.J.D.), Geriatric Medicine (A.M.), Clinical Neurosciences (J.M.W., F.M.C.), and Informatics (N.G.); SHEFC Brain Imaging Research Ctr (I.M., I.J.D., K.P.E., J.M.W., N.G.); Ctr for Functional Imaging Studies (I.M., N.G.); and Ctr for the Study of the Ageing Brain (I.J.D., J.M.W.), Univ of Edinburgh, Western General Hosp, Edinburgh EH4 2XU, Scotland. Received Nov 5, 2003; revision requested Jan 27, 2004; revision received Feb 13; accepted Mar 23. Supported in part by a SHEFC research development grant and a small project grant from the Chief Scientist Office of the Scottish Executive. I.J.D. supported by a Royal Society-Wolfson Research Merit Award. Address correspondence to I.M. (e-mail: ian.marshall@ed.ac.uk).

View larger version (55K): [in a new window]   Figure 1a. (a) Diagrammatic representation of brain activation induced by left-hand finger tapping. All six results (three MR imaging sessions times two task runs) are shown for subject 3, who showed good task repeatability (RI = 0.49). Within each block, sagittal (top left image), coronal (top right image), and transverse (bottom left image) projections are shown. (b) Corresponding transverse MR image sections overlaid with a reliability map show numbers of times (out of maximum of six) voxels in the motor cortex were classified as activated during six runs of the finger-tapping task. Colors range from dark blue (indicating voxels were classified as activated one time) to red (six times). Background images are a template derived from the mean of 20 normalized inversion-recovery-prepared gradient-echo MR images (8/3.4/600, 15° flip angle) obtained in a group of healthy elderly men. Images are shown in neurologic convention (ie, image left corresponds to subject left).

View larger version (141K): [in a new window]   Figure 1b. (a) Diagrammatic representation of brain activation induced by left-hand finger tapping. All six results (three MR imaging sessions times two task runs) are shown for subject 3, who showed good task repeatability (RI = 0.49). Within each block, sagittal (top left image), coronal (top right image), and transverse (bottom left image) projections are shown. (b) Corresponding transverse MR image sections overlaid with a reliability map show numbers of times (out of maximum of six) voxels in the motor cortex were classified as activated during six runs of the finger-tapping task. Colors range from dark blue (indicating voxels were classified as activated one time) to red (six times). Background images are a template derived from the mean of 20 normalized inversion-recovery-prepared gradient-echo MR images (8/3.4/600, 15° flip angle) obtained in a group of healthy elderly men. Images are shown in neurologic convention (ie, image left corresponds to subject left).

View larger version (51K): [in a new window]   Figure 2a. (a) Diagrammatic representation of brain activation induced by left-hand finger tapping. All six results (three MR imaging sessions times two task runs) are shown for subject 7, who showed poor task repeatability (RI = 0.13). Within each block, sagittal (top left image), coronal (top right image), and transverse (bottom left image) projections are shown. (b) Corresponding transverse MR image sections overlaid with a reliability map show numbers of times (out of maximum of six) voxels in the motor cortex were classified as activated during six runs of the finger-tapping task. Colors range from dark blue (indicating voxels were classified as activated one time) to red (six times). Background images are a template derived from the mean of 20 normalized inversion-recovery-prepared gradient-echo MR images (8/3.4/600, 15° flip angle) obtained in a group of healthy elderly men. Images are shown in neurologic convention (ie, image left corresponds to subject left).

View larger version (144K): [in a new window]   Figure 2b. (a) Diagrammatic representation of brain activation induced by left-hand finger tapping. All six results (three MR imaging sessions times two task runs) are shown for subject 7, who showed poor task repeatability (RI = 0.13). Within each block, sagittal (top left image), coronal (top right image), and transverse (bottom left image) projections are shown. (b) Corresponding transverse MR image sections overlaid with a reliability map show numbers of times (out of maximum of six) voxels in the motor cortex were classified as activated during six runs of the finger-tapping task. Colors range from dark blue (indicating voxels were classified as activated one time) to red (six times). Background images are a template derived from the mean of 20 normalized inversion-recovery-prepared gradient-echo MR images (8/3.4/600, 15° flip angle) obtained in a group of healthy elderly men. Images are shown in neurologic convention (ie, image left corresponds to subject left).

View larger version (93K): [in a new window]   Figure 3. Twenty-four transverse MR image sections on the group repeatability map generated for nine subjects who participated in a total of 53 task runs show numbers of times (out of maximum of 53) voxels in the motor cortex were classified as activated. Colors range from dark blue (indicating voxels were classified as activated one time) to orange (28 times) during 53 runs of the finger-tapping task. Background images are a template derived from the mean of 20 normalized inversion-recovery-prepared gradient-echo MR images (8/3.4/600, 15° flip angle) obtained in a group of healthy elderly men. Images are shown in neurologic convention (ie, image left corresponds to subject left).

View larger version (143K): [in a new window]   Figure 4. Thirty transverse MR image sections on a random effects group analysis map generated for nine subjects who performed the N-back working-memory task. Brain activation increased with increasing task difficulty, as indicated by the red, orange, and yellow areas. Brain activation also increased with decreasing task difficulty, as indicated by the blue areas. Background images are a template derived from the mean of 20 normalized inversion-recovery-prepared gradient-echo MR images (8/3.4/600, 15° flip angle) obtained in a group of healthy elderly men. Images are shown in neurologic convention (ie, image left corresponds to subject left).