Memory is the ability to recall information that was previously learned. The brain acquires new information through experience—that is, it learns. The cellular basis for learning is achieved by a special communication pattern between pairs of neurons in certain parts of the brain that results in a “strengthening” of the normal neurotransmission signals. In some cases, the actual structure of the synapse changes to support the strengthened neural signals.
As information is learned, is it then processed as short-term or working memory. Working memory is transient and may last only a minute or two in the absence of repetition. For example, if you are trying to remember a phone number that has just been given to you, you might repeat the number aloud until you can write it down, releasing it from your short-term memory. The hippocampus is critically involved in the formation of new short-term memories and alcohol can easily disrupt the formation of the short-term memory by decreasing the electrical impulses in hippocampal neurons.
Read how alcohol slows electrical impulses in the hippocampus.
Short-term memory is converted to long-term memory through a series of cellular adaptations that allow the memory to be “stored”. These cellular adaptations may involve discrete changes in both gene and protein expression. Though more durable than short-term memory, this intermediate stage of memory remains vulnerable until all the cellular changes have been locked into place. When we need to access the stored long-term memory in the future, our brain initiates a program of “search and recall” that finds the altered neuronal connections and “reads” the encoded information. In this manner, the brain is often compared with modern computers. When alcohol disrupts the formation of the short-term memory, then a person can’t recall events that occurred while (s)he was drinking (i.e., impaired long-term memory).
The function of the hippocampus can be considered in terms of a simple computer. The hippocampus does not act as a storage site (or “hard drive”) for long-term memories—in fact, most patients with hippocampal damage experience no difficulty in recalling events or people. Instead, the hippocampus acts more like a computer processing unit (CPU), processing information that is relayed to other brain regions involved in memory storage. Without the processing work of the hippocampus, the data cannot be integrated into working memories.
In molecular terms, how does the hippocampus process sensory data into meaningful memories? The answer is still largely unknown, but much research is currently devoted to solving this mystery.