Cerebral Cortex Advance Access originally published online on August 5, 2004
Cerebral Cortex 2005 15(4):409-418; doi:10.1093/cercor/bhh144
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Cerebral Cortex V 15 N 4 © Oxford University Press 2004; all rights reserved
Increased Action Potential Firing Rates of Layer 2/3 Pyramidal Cells in the Prefrontal Cortex are Significantly Related to Cognitive Performance in Aged Monkeys
1 Department of Anatomy and Neurobiology, Boston University School of Medicine, Boston, MA 02118, USA, 2 Yerkes National Primate Research Center, Emory University, Atlanta, GA 30322, USA and 3 Center for Behavioral Development, Department of Psychiatry, Boston University School of Medicine, Boston, MA 02118, USA
Address correspondence to Jennifer I. Luebke, Center for Behavioral Development, M923, Boston University School of Medicine, 85 E. Newton St., Boston, MA 02118, USA. Email: jluebke{at}bu.edu.
The neurobiological substrates of significant age-related deficits in higher cognitive abilities mediated by the prefrontal cortex (PFC) are unknown. To address this issue, whole-cell current-clamp recordings were used to compare the intrinsic membrane and action potential (AP) firing properties of layer 2/3 pyramidal cells in PFC slices from young and aged behaviorally characterized rhesus monkeys. Most aged subjects demonstrated impaired performance in Delayed Non-Match to Sample (DNMS) task acquisition, DNMS 2 min delay and the Delayed Recognition Span task. Resting membrane potential and membrane time constant did not differ in aged relative to young cells, but input resistance was significantly greater in aged cells. Single APs did not differ in terms of threshold, duration or rise time, but their amplitude and fall time were significantly decreased in aged cells. Repetitive AP firing rates were significantly increased in aged cells. Within the aged group, there was a U-shaped quadratic relationship between firing rate and performance on each behavioral task. Subjects who displayed either low or very high firing rates exhibited poor performance, while those who displayed intermediate firing rates exhibited relatively good performance. These data indicate that an increase in AP firing rate may be responsible, in part, for age-related PFC dysfunction.
Key Words: area 46 • current-clamp • patch-clamp • slice • working memory
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