The document discusses how memory and cognition are affected by aging. As people age, the hippocampus loses nerve cells and inhibitory neurons, impairing its ability to perform pattern separation and completion functions important for memory. Age-related declines also occur in working memory, ability to form new episodic memories, processing speed, and blood flow in memory-related brain regions. Structural changes in the aging brain like volume reduction, cortical thinning, and loss of synapses between neurons may undermine cognitive functions like learning and remembering. Declines in serotonin receptors and transporters are also associated with aging and influence various cognitive processes and behaviors.