Quantifying Changes in Medial Prefrontal Cortex IEG Expression as a Function of Aging Related Cognitive Decline
Mentor 1
James R. Moyer Jr.
Location
Union Wisconsin Room
Start Date
29-4-2016 1:30 PM
End Date
29-4-2016 3:30 PM
Description
The United Nations projects that the world’s population of individuals over age 85 will increase by a startling 350% by 2050. Therefore, an increased understanding of changes in brain function throughout aging is vital for combating aging-related cognitive decline and improving quality of life for the growing elderly population. We used extinction of fear conditioning to investigate how aging alters the circuits that mediate behaviors susceptible to cognitive decline. Previously, our lab has demonstrated that aging rodents exhibit impaired fear extinction. Fear extinction, like most complex behaviors, involves precise interaction between multiple brain structures. In order to understand how aging-related changes in these structures correlate with behavioral deficits, we measured neuronal activity via expression of the immediate early gene (IEG) proteins Zif-268 and c-fos. Young, middle-aged, and aged rats were separated into four experimental groups; naïve, pseudo-conditioned (PSEUDO), fear conditioned (COND), and fear extinction (EXT). On day 1, COND and EXT rats received 10 fear conditioning trials (15s tone, 30s interval, 1s shock) whereas PSEUDO rats were presented with 10 tones and 10 shocks that were not explicitly paired. On days 2 and 3, EXT and PSEUDO rats were given 10 tone-alone presentations to extinguish the tone-shock association. On the 4th day, COND, EXT, and PSEUDO rats were given 2 tone presentations to obtain an index of conditioned fear. Following testing, brain slices were collected and assayed for expression of IEGs in the regions of interest. Our data suggests that within the prelimbic and infralimbic sub-regions of the prefrontal cortex, IEG expression is preferentially increased in young rats from PSEUDO, COND and EXT groups compared to aging rodents. Interestingly, behavioral differences between age groups were not significant, suggesting that aging alters the neural circuits that mediate fear learning.
Quantifying Changes in Medial Prefrontal Cortex IEG Expression as a Function of Aging Related Cognitive Decline
Union Wisconsin Room
The United Nations projects that the world’s population of individuals over age 85 will increase by a startling 350% by 2050. Therefore, an increased understanding of changes in brain function throughout aging is vital for combating aging-related cognitive decline and improving quality of life for the growing elderly population. We used extinction of fear conditioning to investigate how aging alters the circuits that mediate behaviors susceptible to cognitive decline. Previously, our lab has demonstrated that aging rodents exhibit impaired fear extinction. Fear extinction, like most complex behaviors, involves precise interaction between multiple brain structures. In order to understand how aging-related changes in these structures correlate with behavioral deficits, we measured neuronal activity via expression of the immediate early gene (IEG) proteins Zif-268 and c-fos. Young, middle-aged, and aged rats were separated into four experimental groups; naïve, pseudo-conditioned (PSEUDO), fear conditioned (COND), and fear extinction (EXT). On day 1, COND and EXT rats received 10 fear conditioning trials (15s tone, 30s interval, 1s shock) whereas PSEUDO rats were presented with 10 tones and 10 shocks that were not explicitly paired. On days 2 and 3, EXT and PSEUDO rats were given 10 tone-alone presentations to extinguish the tone-shock association. On the 4th day, COND, EXT, and PSEUDO rats were given 2 tone presentations to obtain an index of conditioned fear. Following testing, brain slices were collected and assayed for expression of IEGs in the regions of interest. Our data suggests that within the prelimbic and infralimbic sub-regions of the prefrontal cortex, IEG expression is preferentially increased in young rats from PSEUDO, COND and EXT groups compared to aging rodents. Interestingly, behavioral differences between age groups were not significant, suggesting that aging alters the neural circuits that mediate fear learning.
