The human brain has an amazing capacity for retaining information, despite being constantly bombarded by sensory signals. Most of this incoming sensory information is retained for less than a second before it is forgotten, but others can go on to form lasting memories that we’ll treasure – or look back on and cringe – forever.
The part of the brain that sorts out what information to store and which to forget is called the hippocampus. It’s also essential for transferring memories from the short to long-term storage. Some of this memory consolidation happens in dreaming as the brain rehearses the day’s activities.
Short versus long term
Short-term memories tend to be based on sound, also known as echoic memory. So if you’re trying to remember a phone number, for example, it often helps to rehearse it vocally in your head. Without concentrating too hard, short-term memory can hold around seven items for 20 to 30 seconds.
Long-term memories, however, tend to be stored more abstractly, by concept, while other memories are stored as sensory echoes, allowing entire experiences to be reconstructed. Human memory is associative; it works by linking pieces of information together. This means that memories are not stored as individual entities, but reconstructed using several different parts of the brain.
Once the trace of a memory is formed, the pathway can be consolidated with use. The more often a synapse is used, the stronger it becomes. That’s why it helps to repeat information over and over when revising for exams. If a synapse is used repeatedly, it becomes increasingly sensitive to stimulation, producing more receptors and strengthening the connection.
Like a computer, the brain is very good at making associations, and incoming information is compared to stored data, allowing us to quickly recall things we already know or have experienced before. Memories are rarely stored in isolation and one pathway is linked to others. Recognition and recall can both trigger other related memories.
There is also another type of memory, known as an implicit memory. These types of memories do not require conscious recall and are often based on motor skills. By repeating tasks, like riding a bike or playing the piano, pathways become automatic. Explicit memories, on the other hand, are accessed consciously. They can be stored as episodes, linked to a specific event or place, or stored by category as more abstract knowledge.
Here’s a handy diagram to help you remember…
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