A recent story in Time magazine on what is known as the “Memory Man” caught my attention. The Memory Man can recall any date in his lifetime and relate every event that occurred that day, even down to the smells and tastes.
He is one of three individuals in the world who is an expert at remembering the most ludicrous details associated with any point in time, and he doesn’t even keep a diary. This made me investigate just how far memory research has come, and recent findings from the National Institute of Mental Health had some revealing information to showcase.
Researchers at the institute have worked with the genetically-engineered mice to isolate the actual component of the brain responsible for sustaining short- and long-term memory. In a way, it’s exciting because memory has pretty much been the holy grail, and unlike other body systems, has only been studied at a psychological level.
Long-term memory gains a foothold as new proteins are added. But so far, this is all we have ever known. Now, the mice studies have managed to trace the path of these proteins, specifically the ones at a synapse (think of your regular train junction) for a memory associated with fear. The synapses contain molecular tags to better chart the the proteins.
The other fascinating aspect of the research is the conclusion that neurons, which are usually activated when we first learn something, also light up when that memory is retrieved. Consequently, stronger memories come from a greater number of neurons.
What is interesting is the way that this was proven. The scientists engineered the mice with tagged neurons in the amygdala, the brain’s fear center. The genes lit red whenever the mice were shocked, and they lit green every time the same experience was repeated. The neurons were then isolated for this specific memory so that the exact brain circuitry involved in the specific learning experience of fear conditioning could be traced.
The scientists also conducted another study in which after conditioning fear in the mice, their AMPA receptors (the ones they had now traced to be responsible for the lit neurons) were triggered. The receptors were now targeted as green glows with the hippocampus, the part of the brain directly accountable for memory. As the mice were shocked again, the receptors in a matter of few hours, had migrated to the hippocampus, which was lit green.
On a molecular level, these studies promise a lot. The scientists have now isolated exactly which synapses of the hippocampus hold memory. They have also worked on spines, which are essentially small nubs on neurons at which the synaptic connection is made. Spines usually come in thin, stubby or mushroom shapes. Spines are altered in cases of Fragile-X syndrome, among other mental disorders.
The study was successful in isolating AMPA receptors to the mushroom-shaped spines, which interestingly, also came up in the opposing study. The opposing study worked on extinction learning, in which the mice were put in the settings that they had earlier been put for fear learning. This time, however, they were not shocked. This led the scientists to conclude the neuronal pathway is dual-faced, and that the neurons responsible for learning a memory, are also responsible for losing it.
Now that this study has taken place, more can be expected on the front of demystifying the parts of the brain that still remain foreign.
