Neural Engineering
Mojdeh Faraji, PhD
Postdoctoral Associate
University of Florida
Gainesville, Florida, United States
Caesar Hernandez
Postdoc
University of Alabama, United States
Alexa-Rae Wheeler
student
University of Texas at Austin, United States
Tyler W. Ten Eyck
student
University of Florida, United States
Barry Setlow
Professor
University of Florida, United States
Jennifer Lynn Bizon
Professor and Chair
University of Florida, United States
Working memory is the temporary retention of information needed to conduct a task, and as such is crucial for different forms of decision-making and cognitive processing in daily life. Declines in working memory associated with aging affect quality of life in older adults by limiting their independence and efficiency in making decisions. Research in behavioral neuroscience supports the connection between age-related deficits in working memory and alterations in functions of the prefrontal cortex (PFC); however, the temporally-precise contributions of this brain region to working memory, and how such contributions change with age, are less well understood. Here we used an optogenetic approach to dissect the contributions of the PFC to temporally distinct phases of this cognitive function in a delayed response working memory task in young and aged rats.
The results show that mPFC stimulation during the retention delay interval improved working memory accuracy in aged rats (p= .022), whereas mPFC inactivation during information encoding impaired working memory accuracy in rats of both ages (p= .024). Interestingly, mPFC stimulation during recall enhanced working memory accuracy at long delays in young rats (p= .016), as did mPFC inactivation during the same period in aged rats (p= .019). Control experiments in which rats were transduced with non-opsin viruses showed no effects of light delivery alone on any component of working memory in rats of either age.
The results suggest that mPFC is critical during encoding information to be retained in working memory for later recall, and that working memory accuracy in aged rats can be enhanced via stimulation of mPFC during the retention delay interval. The fact that the latter effect was selective to aged rats suggests that mPFC activation during the retention delay period (when encoded information must be retained “on line” in working memory in order for successful recall to occur) remediates an age-specific deficit in maintaining such information.
This study supports the utility of PFC stimulation for improving working memory performance in aged adults. The differential effects of PFC manipulations in young and aged rats underscore the importance of evaluating potential therapeutic approaches across the full lifespan, as well as future work on neuroplasticity in aged individuals.