THE EFFECTS OF ANTIOXIDANTS IN THE SENESCENT AUDITORY CORTEX

Authors: DE RIVERA, C - UNIVERSITY OF TORONTO; Shukitt-Hale, Barbara; Joseph, James; MENDELSON, J - UNIVERSITY OF TORONTO

Submitted to: Neurobiology of Aging
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/2/2005
Publication Date: 6/13/2006
Citation: De Rivera, C., Shukitt Hale, B., Joseph, J.A., Mendelson, J.R. 2006. The effects of antioxidants in the senescent auditory cortex. Neurobiology of Aging. 27(7):1035-1044.

Interpretive Summary: A common problem among the elderly is a difficulty in distinguishing speech sounds. This deficit may be due in part to an age-related decline in temporal processing speed, which means that the brain may be processing information that requires rapid rates of processing more slowly than normal. One hypothesis suggests that oxidative stress, an excess of free radicals, may be partially responsible for many age-related deficits. Previous research has shown that aged rats fed an antioxidant-enriched diet for 2 months show improvement in cognitive and motor behaviors. Thus, we investigated whether a two-month dietary supplementation of antioxidants in the form of blueberry phytochemicals, the micronutrients that have been found to have a beneficial effect on health, could reverse or retard the age-related decline in processing speed that has been observed in the aged rat. To this end, physiological recordings were taken from brain cells in the auditory cortex of aged Long Evans hooded rats that had been placed on either a regular (A-CR), corn-supplemented (A-CC), or blueberry-supplemented (A-BB) diet two months prior to the recording. Results showed that most cells in the auditory cortex recorded from A-BB rats responded similarly to that observed in young rats. The majority of cells recorded from A-CC and A-CR rats showed a decrement in processing. These results suggest that age-related changes in temporal processing speed in auditory cortex may be reversed by dietary supplementation of blueberry phytochemicals.

Technical Abstract: A common problem among the elderly is a difficulty in discriminating speech sounds. This deficit may be due in part to an age-related decline in temporal processing speed, observed as a decreased ability to process dynamic aspects of speech such as formant transitions. A useful stimulus for studying this decline is the frequency modulated (FM) sweep, which shares features in common with formant transitions. Studies have shown that the majority of cortical cells from young rats respond most vigorously to rapidly changing or fast FM sweeps, while the majority of cells in the senescent auditory cortex (A1) prefer slower sweeps. One hypothesis suggests that oxidative stress maybe partially responsible for many age-related deficits. Previous research has shown that aged rats fed an antioxidant-enriched diet for 2 months show improvement in cognitive and motor behaviors. Thus, we investigated whether a two-month dietary supplementation of antioxidants in the form of blueberry phytochemicals could reverse or retard the age-related decline in temporal processing speed that has been observed in the aged rat. To this end, single unit responses were recorded in A1 of aged Long Evans hooded rats that had been placed on either a regular (A-CR), corn-supplemented (A-CC), or blueberry-supplemented (A-BB) diet two months prior to the physiological recording. Linear FM sweeps (from low to high and from high to low) at four different rates of modulation were presented. Results showed that most cells recorded from A-BB rats responded most vigorously to fast FM sweeps, similar to that observed in young rats. The majority of cells recorded from A-CC and A-CR rats showed a preference for slow FM sweep rates. These results suggest that age-related changes in temporal processing speed in A1 may be reversed by dietary supplementation of blueberry phytochemicals.