| |
Abstract:
The use of functional neuroimaging to test hypotheses
regarding age-related changes in the neural substrates of cognitive
processes assumes that the coupling of neural activity to
neuroimaging signal does not change with age, but this assumption
has never been directly tested. Using BOLD fMRI, the spatial and
temporal characteristics of the hemodynamic response in primary
sensorimotor cortex between young and elderly subjects was examined
during the performance of a simple reaction time task. We found
that 75% of elderly subjects exhibited a detectable voxel-wise
relationship with the behavioral paradigm compared to 100% young
subjects. The number of suprathreshold voxels in young subjects was
four times greater than in elderly subjects. Young subjects had a
slightly greater signal:noise per voxel than the elderly subjects
due to a greater level of noise per voxel in the elderly subjects.
There was a trend towards greater within-group variability in the
shape of the hemodynamic responses in elderly subjects, but there
was no significant difference between young and elderly groups in
the shape of the hemodynamic response. The overall finding that
some aspects of the hemodynamic coupling between neural activity
and BOLD fMRI signal changes significantly with age suggests
caution in interpreting imaging studies that compare young and
elderly subjects. These results also have implications for the
design of event-related fMRI experiments.
|
