14 DAY TRIAL // Memories are still as mysterious as the universe itself. We still have not located a particular area in the brain that exclusively deals with memories and we cannot say if they are stored in a stable physical state or a changing one. Common theories say that long-term memories are stored in the form of proteins inside the neurons, while short-term memories are more unstable ones.
Now, a team led by Prof. Yadin Dudai, Head of the Weizmann Institute's Neurobiology Department, is challenging this concept. They have found that the process of storing long-term memories is much more dynamic, involving molecular processes running constantly. If the processes are jammed even for short periods, long term memories can be lost. This could lead to future treatments for memory problems.
Dudai's team trained rats to avoid certain tastes. After that they injected a drug blocking a specific protein into the taste cortex, a brain nucleus connected with taste memory. Based on their previous researches, the scientists supposed that the protein, called PKMzeta, works as a tiny memory "machine" that keeps memory functioning.
PKMzeta, found in the synapses, the functional contacts between two neurons, induces changes in some facets of the synaptic contacts. But to maintain this (and memory and learning processes), it must be continuously active. The researchers supposed that shutting off PKMzeta should reverse the synaptic change.
Indeed, no matter the taste the rats had learned to avoid, they forgot about their aversion after just one shot of the drug. This lasted for a month after the memories were formed (in terms of life span, this means years in humans). This is the first time when memories could be erased (and even unpleasant ones) long after their formation.
"This drug is a molecular version of jamming the operation of the machine. When the machine stops, the memories stop as well." said Dudai.
It appears that long-term memory is not a one-time inscription on the neuronal network, but an ongoing process which requires continuous maintenance, an important detail for boosting and stabilizing memory.