ABSTRACT
Age-related memory decline has been associated with changes in the medial prefrontal cortex (mPFC) function. In order to explore the role of mPFC in taste recognition memory, we have assessed mPFC c-Fos immunoreactivity in adult (5-month-old) and aged (24-month-old) male Wistar rats during the first (Novel), second (Familiar I), and sixth (Familiar II) exposure to a cider vinegar solution. Adult brains showed higher c-Fos expression in the ventral but not the dorsal region of mPFC during the second taste exposure. Interestingly, old brains exhibited an altered activity pattern selectively in the dorsal peduncular cortex (DP) which can be associated with a delayed attenuation of vinegar neophobia in this group. These results support the involvement of this area in the formation of safe taste memory. Further research is needed for understanding the role of DP in taste recognition memory and the impact of aging on it.
Subject(s)
Habituation, Psychophysiologic/physiology , Prefrontal Cortex/metabolism , Taste Perception/physiology , Age Factors , Aging , Animals , Avoidant Restrictive Food Intake Disorder , Brain/metabolism , Brain/physiology , Cerebral Cortex/metabolism , Male , Memory , Prefrontal Cortex/physiology , Rats , Rats, Wistar , Recognition, Psychology , TasteABSTRACT
Previous studies have addressed the role of the nucleus accumbens core (NAcbC) and shell (NAcbSh) in taste aversion learning and in the processing of taste palatability which is affected by aging. However, little is known about its implication in safe taste memory and the aging impact. To explore the role of the NAcb in flavor neophobia and its attenuation during aging, we applied c-Fos immunohistochemistry as an index of neural activity of the NAcbC and NAcbSh. Twenty one adult (5-month-old) and 24 aged (24-month-old) male Wistar rats were exposed to a 3% cider vinegar solution for 1, 2 or 6 consecutive days (n = 7 adult and n = 8 aged rats per group). Aged rats exhibited slower attenuation of flavor neophobia than adult rats. Adult rats showed increased NAcbSh c-Fos activity on day 2 compared to days 1 and 6, while this increase was delayed to day 6 in aged rats. There were no differences in the number of NAcbC c-Fos positive cells. This suggests that changes in the activity of neural circuits of palatability processing during normal aging could contribute to the slower attenuation of flavor neophobia in aged rats.
Subject(s)
Age Factors , Nucleus Accumbens/metabolism , Proto-Oncogene Proteins c-fos/metabolism , Taste/physiology , Animals , Avoidance Learning/physiology , Conditioning, Classical/physiology , Female , Male , Memory/physiology , Rats , Rats, Wistar , Recognition, Psychology/physiologyABSTRACT
The relationship between the piriform cortex and flavor recognition memory was investigated in adult and aged rats. By using c-Fos immunohistochemistry, we assessed the piriform cortex activity induced by flavor familiarity. The results indicated increased activity in the rostral region of the posterior piriform cortex elicited by the most familiar cider vinegar solution after six exposures. Aged rats exhibited overall increased activity in the posterior, but not the anterior piriform cortex, which was not related to flavor familiarity. This suggests that the posterior piriform cortex is related to flavor recognition memory and that aging modifies its activity pattern which might underlie their slower attenuation of flavor neophobia.
Subject(s)
Aging , Piriform Cortex/physiology , Recognition, Psychology/physiology , Taste/physiology , Animals , Male , Proto-Oncogene Proteins c-fos/metabolism , Rats , Rats, Wistar , Statistics, NonparametricABSTRACT
Recognition memory is based on the ability to assess the familiarity of a previously encountered stimulus. It can be approached using tests for different sensorial modalities. Excitotoxic lesions of the perirhinal cortex (Prh) were performed in order to assess the relevance of its integrity for object and flavor recognition memory. Object recognition memory was impaired with a 24h retention interval. Flavor neophobia attenuation was prevented on a second encounter with the tastant. These results support a role of the perirhinal cortex in mediating the transition from novel to familiar, both in object and flavor recognition memory.
Subject(s)
Perirhinal Cortex/physiology , Recognition, Psychology/physiology , Space Perception/physiology , Taste Perception/physiology , Animals , Exploratory Behavior , Rats, WistarABSTRACT
Perirhinal cortex (PRh) pathology and chemosensory identification dysfunction are early signs of Alzheimer's disease. We have assessed the impact of normal aging on PRh activity during flavor recognition memory using c-Fos immunoreactivity as a marker for neuronal activity. Adult (5-month-old) and aged (24-month-old) Wistar male rats were exposed to a vinegar solution on a daily basis for a period of six days. Behavioral assessment indicated similar performance in both age groups but suggested slower attenuation of neophobia in aged rats. Regarding c-Fos immunoreactivity, an opposite pattern of PRh activity was found in adult and aged groups drinking the flavor solution during the first (Novel), second (Familiar I) or sixth (Familiar II) exposure as the flavor became familiar. While adult rats exhibited a higher number of PRh c-Fos-positive neurons during the presentation of the novel flavor than during the second and sixth presentation, in aged rats the number of PRh c-Fos-positive neurons was higher during the presentation of the familiar flavor in the last session than in the first and second. The results suggest that the role of the PRh changes during aging and can help to dissociate PRh dysfuntions induced by neurodegenerative diseases and normal aging.