Scientists may have cracked the code of memories by successfully tracing how they are imprinted on the brain. An experiment charted the nerve cell changes that occurred within rats’ brains as they made decisions—a process that could prove life changing if replicated in humans.
“For decades scientists have been trying to map memories in the brain. This study shows that scientists can begin to pinpoint the precise synapses where certain memories form and learning occurs,” explained James Gnadt, a program director at the National Institute of Neurological Disorders and Stroke.
Animals use sensory information to guide their behavior, the paper reads, but how this activity leads to appropriate action has not yet been explained. This research studied the synapses in the striatum—an area deep inside the brain that assists the translation of thoughts into actions—analyzing how auditory learning is both instigated and maintained.
The experiment challenged a group of rats to put their noses into three slots, the middle of which would sound either a high- or low-pitched noise. For one half of the rodents, the high-pitched sound equated to the left-hand slot containing food, while those who heard the lower pitch would find food behind the right-hand door. They quickly became adept at this task, establishing the connection between specific sounds and the location of the food, and gaining in speed as they sought it.
“This is pretty cool,” enthused Professor Ellen Carpenter, chair of UCLA’s undergraduate Neuroscience program, “because it demonstrates that it is possible to find the cellular source of learning. Previously we had thought that learning was much more distributed across the brain.”
After the performance task, the rats’ striata were then dissected, whereby scientists found that the sounds they had heard and actions these noises had provoked created a pattern in their synapses—one particularly visible due to the way sound is processed by the brain.
But the clarity of this memory map still surprised one of the study’s lead researchers, Professor Anthony Zador. “This animal has 100 million neurons, of which millions are in the auditory cortex. And yet out of all the things the animal learnt in its life we were able to interrogate this particular set of functions,” he said.
While the exact technologies used would be unsuitable for replication among humans, Professor Zador was optimistic that this could pave the way for charting certain behaviors in our brains. “Our work establishes how certain learned behaviors are encoded, and one could envision developing alternative technologies for decoding them in humans.” If developed, this process could also herald leaps forward in the understanding of a number of disorders in which the striatum is implicated, such as Parkinson’s and Huntington’s diseases, as well as OCD and addiction. “By studying these circuits at very high resolution, as we are doing, we are laying the foundation for much subtler therapies than are currently available for these conditions,” he added.
There is the risk, of course, that advancing our ability to read memories could open the door to a dystopian future—one where analyzing slices of the brain might become an accepted means of proving whether its holder has been telling the truth. If someone on death row denied engaging in a certain kind of criminal activity, for example, could this testing be carried out to assess whether or not they were lying?
“I'm not sure I would want to see the technology developed in this way!” Zador mused. “I think it would be horrible to live in a society where one could read out people's memories.”
But in the longer term, this process could be key to resolving one of the greatest mysteries of neuroscience: how memories are encoded. “If we knew that, we might even be able to build forms of artificial intelligence that operate on the same principles as we do,” Zador said.
Though mapping the memories of humans may not be on the immediate horizon, the development of such a process among other animals is a significant step forward in making this a possibility. Being able to analyze the forms certain diseases take in the striatum could lead to radically different treatments for a huge range of illnesses and addictions, thereby transforming our cognitive understanding forever.