Organising our Memories
Memories are integral to human interaction, scents, tastes and touch can all invoke us to remember particular events. How do you remember that you ordered a coffee before paying for it? Or picking up the TV remote before changing the channel? Dr. Leila Reddy undertook a study to look at the occurrence of events and how we know the ordering of these events and memories. Reddy talks about how “In this study we were interested in what we call episodic memory. The memory of events or episodes, for example the what, the where and the when of an event.”
The electrical activity has previously shown us the “what” and “where” of events. Reddy mentions that “Several years ago we had revealed evidence for what we called the Jennifer Aniston neuron, which is just a neuron in the human hippocampus that represented very specifically this particular actress.” This study incorporated a patient who loved the show F.R.I.E.N.D.S., and whenever Jennifer Aniston came on T.V this particular neuron lit up in the brain. Reddy and her colleagues designed a study to understand how we know “when” events, like this, occur.
The study consisted of epileptic patients who had recent surgeries, to have electrodes implanted in their brain. Over a period of two weeks they were shown 5-7 pictures several times in a predictable pattern whilst monitoring electrical activities from neurons in their brain. One set of experiments consisted of a 0.5 second pause between images and the other set a 10 second pause with a black screen shown. The patients were then asked to name the next image.
The results showed that the neurons were firing electrical activity both during seeing an image and during a blank period or black screen.The presence of these time cells is not only limited to periods of activity but also of inactivity. This is a building block towards understanding how the brain encodes information and records memories.