Memory web
Memory research is undergoing a revolution.
New technologies of imaging individual neurons,
and manipulating them, is helping scientists to gain,
more insights into the working of memory.
The working of memory involves many factors.
Individuals elements of memory, have to be integrated into a whole.
Elements of a face, have to be integrated, to recognise a person.
The memory needs to have a context.
We recall, "where" we saw the face.
We need to link memories over time.
We recall, "when" we saw the face.
We also link, certain impressions about the face.
Memories don't exist in isolation.
One memory is linked to other memories.
We can remember sequences of events.
Scientists are researching, how the brain,
links memories across space and time.
Most memories exists as part of a sequence of memories.
The brain uses specific rules to assign bits of learned information,
to a discreet group of neurons, in the brain regions forming the memory.
This concept is called memory allocation.
A particular gene, known as the CREB gene,
is know to be associated with formation of long term memories.
The CREB gene does this by encoding a protein, that regulates the expression,
of other genes, required for memory.
During some learning, some synapses are built up, or strengthened,
so as to facilitate communication between neurons.
The CREB protein acts like a molecular architect for memory.
Scientists studied the role of the CREB protein, in the Amygdala and the hippocampus.
The amygdala plays a role in emotional memory.
The hippocampus plays a role in the internal map, of our surroundings.
Scientists researched the role played by CREB, in the amygdala of mice.
They found that neurons with more CREB protein, was more likely to store fearful memories.
The same was true, for the hippocampus and the cortex, of the brain.
Scientists modified neurons in the amygdala, so as to produce more CREB.
A virus was used for delivering into the cell, extra copies of the gene that encodes the CREB protein.
They found that these neurons were more excitable.
It was more easy to switch on these neurons than others.
CREB spurred in making of new ions channels.
These neurons, with more ions channels, were more amenable to storing a memory.
It was found that these neurons, developed stronger synapses.
By this method, scientists induced certain neurons to store a fearful memory.
They also artificially excited the same neuron.
This induced an artificial recollection of the stored fearful memory.
These findings seem to indicate, that the CREB gene is involved,
in formation of memories.
This finding also helped to suggest how memories could be linked.
Memory allocation happens in neurons having higher CREB,
that are more easily activated.
This process primes these neurons to readily store another memory.
When two memories share many of the same neurons,
they are formally linked.
Activation of neurons during recall of one of the memories, triggers a recall,
of the other memory.
Memories formed during a smaller period of time, seem to be stored in neurons,
closer to each other.
Discrete memories formed at closely spaced intervals, are stored in the same brain area,
in overlapping population of neurons.
This overlap links the two memories, so that recall of one, brings to mind the other.
Scientists invented, a mini microscope or mini scope, closely to monitor the neurons in the brain.
This device could be fitted into the skull of an animal, like mice.
Neurons were genetically engineered, so that they fluoresce,
when the calcium levels in the cells increase.
The CA1 region of the hippocampus is involved in the role of learning and remembering places.
They found that memories formed within a few hours, were located in overlapping clusters of neurons.
Activating one memory resulted in activating the second memory.
Related memories share some neurons.
If these neurons are deactivated, the link between the two memories gets disrupted.
Some people's memory weakens with age.
This can be attributed to the linking neurons, not being as excitable as before.
In many cases, this process could be slowed down, by paying more attention.
These experiments seem to indicate, that events that happen, close to each other in time,
are linked together by shared neurons.
It is possible that a similar mechanism exists for associated memories.
For example, the sound of a bell may be associated with food.
Two and more memories, can be linked by association.
For example, we can associate a name or a face, with a funny story.
We can build stronger memories, by forming more links to other memories.
The more number of links the memory has, the easier is it to recall it.
This can be used as a learning tool.