We
use MRI images of brain anatomy in several ways. We coregister
our optical data to each subjects MRI brain image in order
to accurately determine which brain structures are being measured. In addition we use Voxel Based Morphometry (VBM)
to assess cortical volume Diffusion Tensor Imaging (DTI)) to trace fiber
tracts in the brain. These tools provide anatomical information that can be paired with our functinonal measures.
Functional
Magnetic Resonance Imaging (fMRI) is a technique which measures blood flow to asses neuronal activity. It provides
images with very good spatial resolution (0.5 cm or less) and has a
temporal resolution of the order of .5 to 5 seconds, depending on the
situation. Thus, whereas its temporal resolution is less than that of
ERPs and EROS, the spatial information it provides is excellent.
A recent study by our lab
(Schneider-Garces et al., 2009) used fMRI to assess different
processing in old and young adults during a memory task. Subjects were
shown a letter set ranging from 2-6 letters. After a brief interval
they were shown a single "probe" letter. Holding on to five or six
letters requires a great deal of more effort than holding onto two or
three.
It
turns out that older adults engaged more brain areas at low task demand
than younger adults do. Conversly the younger adults increase
recruitment of these areas only at high task demand
Age Differences: Trends represent areas that increase as load changes from 2-4 or 4-6.
Although they show different
patterns of recruitment, the areas that increase with task demand are
the same between young and old. Older adults simply need to recruit
these areas even at moderate task demands. This may represent aworking
memory system that is becoming impaired with age.
