Ever wonder why certain odors trigger long-term memory and why the smell of sugar cookies can still transport you back to your grandmother’s kitchen in the build up to Christmas decades past?
Neuroscientists Christina Strauch and Denise Manahan-Vaughan from the Ruhr-Universität Bochum did and designed a study to investigate. They reported last month in Cerebral Cortex on their research that showed the piriform cortex, a part of the olfactory brain, is involved in the process of saving those memories. However, the mechanism only works in interaction with other brain areas.
"It is known that the piriform cortex is able to temporarily store olfactory memories. We wanted to know, if that applies to long-term memories as well," explains Christina Strauch.
Synaptic plasticity is responsible for the storing of memories in the memory structures of the brain: During that process the communication between neurons is altered so that a memory is created. Strauch and Manahan-Vaughan examined if the piriform cortex of rats is capable of expressing synaptic plasticity and if this change lasts for more than four hours; indicating that long-term memory may have been established.
The scientists used electrical impulses in the brain to emulate processes that trigger the encoding of an olfactory sensation as a memory. They used different stimulation protocols that varied in the frequency and intensity of the pulses. These protocols can induce long-term effects in the hippocampus. Strikingly, the same protocols did not induce long-term information storage in the form of synaptic plasticity in the piriform cortex.
The scientists wondered whether the piriform cortex needed to be instructed to create a long-term memory. They then stimulated the orbitofrontal cortex, which is responsible for the discrimination of sensory experiences. This time the stimulation of the brain area generated the desired change in the piriform cortex. "Our study shows that the piriform cortex is indeed able to serve as an archive for long-term memories. But it needs instruction from the orbitofrontal a higher brain area—indicating that an event is to be stored as a long-term memory," says Strauch.