Affiliations: NeuroImaging and Analysis Group, Research Center for
Molecular and Cellular Imaging, Tehran University of Medical Sciences, Tehran,
Iran | School of Medicine, Shahid Beheshti University of
Medical Sciences, Tehran, Iran | Department of Neurology, Shariati Hospital, Tehran
University of Medical Sciences, Tehran, Iran | NeuroImaging and Analysis Group, Research Center for
Molecular and Cellular Imaging, Tehran University of Medical Sciences, Tehran,
Iran | Medical Imaging Center, Imam Khomeini Hospital, Tehran
University of Medical Sciences, Tehran, Iran
Note: [] Corresponding author: Mohammad Ali Oghabian, NeuroImaging and
Analysis Group, Research Center for Molecular and Cellular Imaging, Tehran
University of Medical Sciences, Tehran, Iran. E-mail:
oghabian@sina.tums.ac.ir
Abstract: Purpose: To evaluate patterns of activation, convergence and
divergence of three functional magnetic resonance imaging (fMRI) Working Memory
(WM) tasks in two different age groups. We want to understand potential impact
of task and subjects' age on WM activations as well as most important areas
with regard to WM functions. Materials and methods: Thirty-five healthy volunteers completed
visual, verbal, and novel auditory WM tasks. The subjects were selected from
age extremes to depict possible impact of normal aging. The General Linear
Model was used to report significant activations and the effect of age group.
Contrasts revealed differences in activation between tasks, and Combined Task
Analysis was performed to determine common regions of activation across tasks.
Results: Most of the observed differences between the tasks were
seen in areas that were responsible for feature processing. Frontal regions
were mainstay activation areas, regardless of the utilized stimulus. We found
an age-related reduction in activity of visual (in visually-presented tasks)
and auditory (in auditory task) cortices but an age-related increase in
prefrontal cortex for all tasks. Conclusion: Regardless of the type of the task stimuli, frontal
regions are the most important activation areas in WM processing. These areas
are also main targets of age-related changes with regard to activation
patterns. Our results also indicate that prefrontal overactivity in working
memory might be a compensatory effort to mask age-related decline in sensory
processing.
Keywords: Working memory, fMRI, task, stimulus type, age
