Long-Term Memory

Memory is the mental power, process, or capacity to remember, retain, or recall what has been learned. Research tells us that our brains are actively at work both storing and recalling information and that this process of creating memories does not occur in one single area of the brain.

Humans have the capacity to store both short-term and long-term memories. Long-term memory [Page 1003]is the storage of information over a long period of time. Some information stored in lasting long-term memory may be lost, but long-term memory has an unlimited capacity and the information stored can last a lifetime. This entry first discusses the differences between long-term memory and short-term memory and those between implicit memory and explicit memory. It then discusses research on long-term memory.

Over the course of an individual’s lifetime, memories from experiences and events are initially received as sensory input and briefly stored in short-term memory. Short-term memory is termed working memory, because it is temporary yet active. Some believe the capacity of short-term, working memory is between 15 and 30 seconds, while long-term memory is anything that lasts for more than 24 hours.

In 1956, George Miller described the capacity of short-term memory as “the magical number seven, plus or minus two.” Miller suggested that short-term memory has a limited number of storage spots and adults can only store between five and nine items at one time. For various reasons, some of the information and experiences that are briefly stored in short-term memory are lost. However, with practice and under certain circumstances, initial experiences stay long enough to be moved to long-term memory with the potential for permanent storage.

Different regions of the brain are devoted to different functions related to storing memories. Short-term and long-term memories are housed in different places. Short-term memories of events and experiences are stored in a region of the brain called the hippocampus. The hippocampus is an important part of the limbic system of our brains that plays a vital role in learning and memory formation. In the hippocampus, short-term memories begin to be converted to long-term memories. When an event is experienced for the first time, a link is formed in the hippocampus. Other links are created and connected to the initial link. Memories are stored when connections between neurons are active and strengthened over time. The stronger the link, the quicker we are able to retrieve stored memories.

The conversion from short-term to long-term memory takes time. Memories moved to long-term memory become resistant to competing stimuli in the brain and other outside influences. Eventually, our experiences maintain a permanent place in our memory.

As experiences stored in short-term memory are collected and organized, immediate changes happen in our brains. Neurons, or nerve cells, play a part in creating or enhancing synapses in the brain. For long-term memories to survive for a long period of time, we must recall the memories from time to time. When we recall or remember something, we strengthen connections between neurons, or nerve cells, in our brain. These nerve cells exchange information and help us remember events and experiences.

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