Scientists have gained a clearer understanding of how our brains form memories of everyday events. Nerve cells in an area of the brain called the medial temporal lobe play an important role in the fast formation of new memories about personal experiences and life events, researchers at the University of Leicester and colleagues in the US have found.
Different types of memory involve different systems of nerve cells in multiple parts of the brain. Memory for events experienced through life is known as episodic memory; it enables you to recall information like where you first met a friend.
It is usually episodic memory that is first affected by Alzheimer’s disease, leaving people unable to recall events from their recent past even when they can remember abstract facts and other information.
In the study, 14 people with severe epilepsy had electrodes implanted to identify the brain location where their seizures arose. The devices also allowed the researchers to locate individual neurons that encode memories.
The subjects observed roughly 100 pictures of celebrities including Clint Eastwood, Julia Roberts, Tiger Woods, Halle Berry and Josh Brolin as well as places sucha as the White House, Pyramids, and Leaning Tower of Pisa.
Using the electrodes the researchers saw that different nerve cells respond to different images. For example, a nerve cell that fired when a participant saw a picture of a celebrity like Clint Eastwood wouldn’t fire when the person saw a landmark like the Eiffel Tower.
The subjects then were shown composite images which included both a familiar person and a place. The researchers tracked the activity of individual neurons as the patients processed new associations between people and places. The individual neuron that earlier had responded to Brolin’s image, for example, immediately began responding to the Eiffel Tower as well.
Dr Laura Phipps of Alzheimer’s Research UK said:
“Associating different aspects of a life experience is crucial for the formation of new memories and this research sheds new light on the biology underlying this process. While this study did not investigate memory in people with dementia, problems with the formation of new memories are characteristic of diseases like Alzheimer’s. These symptoms can be extremely distressing for the person experiencing them as well as for those around them. Understanding more about the way our brains form and retrieve memories is an important step towards understanding how diseases like Alzheimer’s affect the brain and what might be done to help those living with these conditions."
Rapid Encoding of New Memories by Individual Neurons in the Human Brain Matias J. Ison, Rodrigo Quian Quiroga, Itzhak Fried Neuron, Vol. 87, Issue 1, p220–230 DOI: http://dx.doi.org/10.1016/j.neuron.2015.06.016
Image: Jef Safi/Flickr