Aging is characterized by impairments in decision-making, memory, and learning. Classical theories suggest that the cognitive decline may be caused by increased neural variability, reducing the signal-to-noise ratio of information processing in the central nervous system. To explicitly test this hypothesis, we investigate behavior and brain activity in young and old mice performing a visual decision-making task. Old animals show relatively worse performance (a shallower psychometric curve and slower reaction times). We then used extracellular neural recordings to quantify single-neuron variability (using Fano Factors) in the cortex, hippocampus, and thalamus. Preliminary analyses of the neural data indicate that, in line with those classical theories, old animals show higher trial-to-trial firing rate variability of neurons from the dentate gyrus of hippocampus and thalamus. Old animals also exhibit smaller variability ‘quenching’ (variability decrease on stimulus onset) than the young animals in the hippocampus and thalamus. These aging effects vary across the different brain regions we examined. Our next steps will extend the current analysis to the local circuit level by exploring noise correlations between neurons. We also plan to link age-related changes in neural variability to decision-making behavior. This work will help us understand alterations of neural function that may contribute to age-related cognitive decline.