Washington: Researchers have taken a significant step forward in unraveling the mechanisms of Pavlovian conditioning and understanding this will help understand how memories form and, ultimately, provide better treatments to improve memory in all ages.
"Memory is essential to our daily function and is also central to our sense of self. To a large degree, we are the sum of our experiences. When memories can no longer be retrieved or we have difficulty in forming new memories, the effects are frequently tragic. In the future, our work will enable us to have a better understanding of how human memories form," Gregg Roman, an associate professor of biology and biochemistry at University of Houston's said.
Roman along with his team studied the brains of fruit flies (Drosophila). Within the fly brain, Roman said, there are nerve cells that play a role in olfactory learning and memory.
Roman said they found that these particular nerve cells- the gamma lobe neurons of the mushroom bodies in the insect brain- are activated by odours. Training the flies to associate an odour with an electric shock changed how these cells responded to odours by developing a modification in gamma lobe neuron activity, known as a memory trace.
They found that training caused the gamma lobe neurons to be more weakly activated by odours that were not paired with an electric shock, while the odours paired with electric shock maintained a strong activation of these neurons. Thus, the gamma lobe neurons responded more strongly to the trained odour than to the untrained odour.
The team also showed that a specific protein - the heterotrimeric G(o) protein - is naturally involved in inhibiting gamma lobe neurons.
Roman said removing the activity of this protein only within the gamma lobe neurons resulted in a loss of the memory trace and, thus, poor learning. Therefore, inhibiting the release of neurotransmitters from these neurons through the actions of the G(o) protein is key to forming the memory trace and associative memories.
The significance of using fruit flies is that while their brain structure is much simpler with far fewer neurons, the mushroom body is analogous to the perirhinal cortex in humans, which serves the same function of sensory integration and learning.
The study was published in journal Current Biology.