Short-term memory falls into two categories: working memory and storage-based memory. Working memory is an area in the brain's frontal lobe that holds information for quick cognitive manipulation. Storage-based short-term memory is an area in the brain's temporal lobe that stores information for minutes, hours or days. You can consciously attend to information in your head only once it enters working memory. Explicit decision-making, reasoning and calculation make use of information in working memory.
Keeping Important Information Active
People intentionally choose what information to feature in working memory depending on what they need it for, says University of Oregon psychologist Edward Awh. If you just looked up a phone number in the phone book and need to dial it, you can choose to keep that information active for long enough to dial the number. The method of chunking can assist in keeping information active. For example, to keep the 8-digit sequence "69911711" active, you can use the labels "U.S Route," "terrorism" and "convenience store."
Making Decisions
Working memory helps us make all the decisions we explicitly make--from choosing whether to buy soy milk or skim milk to deciding which graduate schools to apply to. Decision making requires generating and comparing options. When the hippocampus, which stores information, is too active, working memory in the prefrontal brain areas doesn't function properly, reports a Columbia University research team in the March 2007 issue of "Proceedings of the National Academy of Sciences." Hyperactivity in the hippocampus can get in the way of good decision-making by overflowing working memory with options, the scientists say.
Replaying Alternatives
The brain's main memory storage center, the hippocampus, unconsciously replays experiences in new ways, reports a research team in the March 2010 issue of "Neuron." The researchers measured brain activity in mice traveling a maze and found that the least traveled paths and the untraveled paths were replayed most frequently during decision-making. For example, if a mouse had traveled from A to B and from B to C but never from A to C, then neurons representing the path from A to C would fire. This indicates that one function of storage-based short-term memory is to create the alternatives available when making decisions.
Assisting in Long-Term Memory Formation
The brain stores information for a long time by creating neural networks, a strengthening of the synaptic connections in a group of neurons, says Montreal neuroscientist Wayne Sossin. Synaptic connections strengthen when new proteins are produced locally at the synapses. For information to move from short-term memory in the hippocampus to long-term storage in the cerebral cortex, an outer layer in the brain, the information must either replay itself or elicit a strong emotional response. Short-term memory helps long-term memory storage by assisting in replaying information.
Maintaining Long-Term Memory
Storing memories for a long time is not like carving letters in stone, says head of the Weizmann Institute's neurobiology department Yadin Dudai. Long-term memory is dynamic. The molecule machine at the synapses of the neurons in memory networks is hard at work maintaining strong connections. Dudai and his team carried out a study where they blocked the molecule machine in taste neural networks in rats. The rats' long-term taste memories were immediately wiped out. The replay function of short-term memory assists in keeping the synaptic molecule machine up and running.
References
- Science Daily: How We Keep Visual Details In Short-Term Memory
- "PNAS"; Paradoxical influence of hippocampal neurogenesis on working memory; Saxe et al; March 2007
- "Neuron"; Hippocampal Replay Is Not a Simple Function of Experience; Gupta et al; 2010
- Science Daily: First Image Of Memories Being Made
- "Science"; Rapid Erasure of Long-Term Memory Associations in the Cortex by an Inhibitor of PKM{zeta}; Shema et al.; Aug 2007
