24 April, 2008

I think, I remember and I retrieve

I needed to do something...
I needed to do something...

While learning a new fact, physical changes in the brain-structure occur. Theses are still too complex for us to completely understand what these changes are, how they are organized across the synapses and neurons, how they are encoded and decoded, even decades later.

Memory is divided into short-term memory (remembering a phone number just long enough to dial it) and long-term memory (what you did on your last birthday).
Within long-term memory, declarative memories (like names and facts) are distinct from non-declarative memories (riding a bicycle, being affected by a subliminal message), and within these general categories are numerous subtypes. Different brain structures seem to support different kinds of learning and memory; brain damage can lead to the loss of one type without disturbing the others.

In these memory types, molecular mechanisms seem to be at work. Theories of memory propose that memory storage depends on synapses, the tiny connections between brain cells. When two synapses are active at the same time, the connection between them strengthens; when they are not active at the same time, the connection weakens. Out of such synaptic changes emerges an association. Experience can, for example, strengthen the connections between the smell of coffee, its taste, its color and the feel of its warmth. Since the populations of neurons connected with each of these sensations are typically activated at the same time, the connections between them can cause all the sensory associations of coffee to be triggered by the smell alone.

But only associations – and strengthened connections between neurons – is not enough to explain memory. The great secret of memory is that it mostly encodes the relationships between things more than the details of the things themselves. When you memorize a melody, you encode the relationships between the notes, not the notes per se, which is why you can easily sing the song in a different key.

Memory retrieval is even more mysterious than storage. When asked if you know Elvis Presley, the answer is immediately obvious to you, and there is no good theory to explain how memory retrieval can happen so quickly.
But sometimes, our memory abandons us and we are not able to remember information. Then the desynapse technique is useful when standard recall techniques have failed. The user stops trying to recall information directly and allows the data to be recalled whilst focused on an unrelated subject.