Q. My father, aged 62, seems to be having memory problems. Do you think this could be related to his depression?
A. The short answer is probably. The longer answer involves some specifics about brain function. The human brain actually consists of several interconnecting brains, sometimes referred to as functional layers. Each is known for distinct functions, though all functional systems constantly interact.
Thinking brain layer—composed of two cerebral hemispheres, this portion of the brain orchestrates conscious rational/logical thought including executive functions and the managing of willpower and emotions.
Emotional brain layer—composed of several small brain organs, this portion includes the pain/pleasure center, some memory functions, and the surfacing of emotional impulses.
Action brain layer—composed of the brain stem and cerebellum, this portion houses instinctual responses, reflexes, survival impulses, and fight-or-flight reactions.
The emotional brain layer contains the hippocampus. It helps to coordinate incoming sensory data and organize the information into memories by forming associations between different sensory representations of the same object, event, or behavior. Information that involves two or more senses is more likely to be stored. The emotional brain layer also contains the amygdalae; two little almond-shaped brain organs that help to transfer information from short-term to long-term memory. What the brain decides to store (move into long-term memory) hinges on two factors: whether the information has emotional significance, and whether it is related to something you already know.
To recall a memory, the hippocampus searches the brain for bits and pieces (multiple associations) in order to reassemble the memory, much as a search engine helps locate information on the Internet. The emotional brain layer (containing the hippocampus and amygdalae) is the region of the brain believed to be the most sensitive to stress. There likely is a connection between prolonged and severe stress and damage to the hippocampus. Depression apparently can lead to atrophy of the hippocampus, as well, which, in turn, can impact memory. This is a good reason for taking steps to identify, treat/manage depression in a timely manner.