During normal aging in the rhesus monkey, pyramidal cells in the dorsolateral prefrontal cortex (LPFC) undergo significant structural and functional changes that are likely associated with cognitive impairment, while pyramidal cells in the primary visual cortex (V1) are comparatively spared. The overall hypothesis of this project is that selective vulnerability of neurons and associated networks in LPFC compared to V1 during aging is due to a greater susceptibility to increases in oxidative stress, inflammation, and vascular dysfunction in LPFC than in V1. We further hypothesize that intervention with the potent antioxidant and anti-inflammatory polyphenol curcumin will prevent or reduce age-related dysfunction on multiple scales- from the molecular to the behavioral level. This project has three aims: 1) To assess the biomarker and ultrastructural characteristics of V1 and dlPFC neuropil. In situ immunofluorescence multiplexing of ~30 protein biomarkers will be used to determine the molecular phenotype of neurons, glia, vasculature and surrounding neuropil with a GE Global Research platform tailored for use in brain tissue, enabling quantitative, multimarker analyses with high throughput. Using 2D and 3D electron microscopy, inhibitory and excitatory synapses, mitochondria, myelin and axons of neurons as well as microglia and vascular elements will be quantitatively characterized. 2) To characterize the physiological and morphological properties of layer 3 (L3) pyramidal neurons and of interneurons in V1 and dlPFC across the adult lifespan of rhesus monkeys. Using whole-cell patch-clamp recordings we will assess passive membrane properties, AP firing patterns and underlying ionic currents, as well as excitatory and inhibitory postsynaptic currents of L3 excitatory and inhibitory neurons in in vitro slices of PFC and V1. We will then characterize the morphological properties (e.g. dendritic topology, density and detailed morphology of dendritic spines and neurotransmitter receptor and transporter distribution, as well as oxidative stress markers) of these same neurons using immunohistochemistry and ultra-high resolution confocal laser scanning microscopy. 3) To use computational models of V1 and dlPFC networks to predict the functional consequences?at the single neuron, network and behavioral levels?of changes revealed in Aims 1 and 2. Simplified models of LPFC and V1 neurons will be incorporated into model networks capable of persistent neural activity, oculomotor spatial working memory, and visual orientation tuning. Unique to this proposal is the combination of state-of-the art anatomical, physiological, and computational approaches together with concurrent behavioral assessment of the aging monkey under control conditions and following therapeutic treatment with curcumin. This project will yield entirely novel and critically needed information on the neural substrates of cognitive decline in the aging primate and provide important insight into the specific mechanisms of action of protective anti-inflammatory and anti-oxidants during normal aging.
The goal of this study is to characterize the changes that occur to neurons, glia and vasculature in the prefrontal cortex and visual cortex during normal aging in the rhesus monkey in order to gain insight into the neural substrates of age-related cognitive decline in the primate. Importantly we will also test the ability of curcumin, a very powerful antioxidant and anti-inflammatory agent, to prevent significant age-related changes to the brain. This study will thus reveal mechanisms underlying age-related brain dysfunction and suggest mechanisms that can compensate for changes to restore cellular function, and thus has broad implications for therapeutic strategies to reduce cognitive decline during normal aging, an important goal given our aging population.