MedicalResearch.com Interview with:
Samuel Schacher, PhD and
Jiangyuan Hu, PhD,
Department of Neuroscience
Columbia University Medical Cente
New York State Psychiatric Institute
New York, NY 10032, USA

MedicalResearch.com: What is the background for this study? What are the main findings?

Response: It is well established that learning and memory requires changes in the properties of specific neural circuits in the brain activated by the experience. The long-term storage of the memory is encoded through changes in the function of the synapses within the circuit. Synapses are sites of communication between neurons, and the changes in their function come in two varieties: increases in strength and decreases in strength. The encoding of memories typically requires some combination of these synaptic changes, synaptic plasticity, which can last a long time to contribute to long-term memory. Thus the maintenance of a memory will require the persistent change (long-term synaptic memory) in the function of specific synapses.

But memories come in different flavors. In the original experiment by Pavlov, a neutral tone, which dogs ignore, came to predict the immediate appearance of a meal. After several of these pairings, the dogs would become happily excited just with the tone. The same type of conditioning could have a negative valence – the tone could proceed a shock to one of the dog’s paw. Now the neutral tone would predict a negative stimulus and the dog would express fearful behavior just with the tone (associative learning). A non-associative form of memory would be the same types of stimuli but without the preceding neutral stimulus. At random times the animal will be given a meal or a shock. The behavior of the animal for some time will take on the positive or negative features of its environment – a contented versus depressed condition.

Each of these forms of long-term memory would be maintained by increases in the strength of specific synapses.

The questions addressed in our study published in Current Biology, based on previous work in my lab and the lab of my colleague Wayne Sossin at McGill, were:

1) Do the same molecules maintain increases in synaptic strength in the neurons of the circuit after stimuli that produce long-term classical conditioning (associative learning) and long-term sensitization (non-associative learning)?
2) If different molecules maintain the different synaptic memories, is it possible to reverse or erase the different synaptic memories by interfering with the function of the different molecules?
3) If true, can we reverse the different synaptic memories expressed in the same neuron by interfering with the function of the different molecules.

Continue reading →