Neuroscientists from New York University (USA) have identified the parts of the brain that we use toremember the succession of events within an episode of our life, like a party or a wedding. The study, which appears in the latest issue of the journalScience, improves our understanding of how memories are processed.
Previous research showed thatmiddle temporal lobe of the brain (MTL)plays an important role indeclarative memory, that is, the memory of facts or events, and that damage to this area causes memory impairment. More specifically, declarative memory is impaired in Alzheimer’s patients. However, little is known about how individual structures within the MTL remember information about how a specific event unfolded, such as the order of toasts at a wedding.
To find out, Yuji Naya and her colleagues performed an experiment in which a group of animals performed a time-order memory task in which a sequence of two visual objects was presented and the subjects had to retrieve the same sequence after a period of time. In order to perform the task correctly, the animals needed to remember both the individual visual elements (“what”) and the temporal order (“when”). During the experiment, the researchers monitored the activity of individual brain cells in the MTL.
The results showed that two main areas of the MTL are involved in the integration of “what” and “when”: andl hippocampus and perirhinal cortex. The hippocampus, known to play an important role in a variety of memory tasks, provides a timing signal between key events, providing information about the passage of time from the last event, as well as the estimated time to the next. The perirrinal cortex integrates information about “what” and “when,” that is, what happened first or second in a series.
The new finding provides a deeper understanding of brain activity patterns, allowing us toremember both the key events that mark our lives (weddings, graduations, births …) and the specific order in which they occurred, the scientists conclude.
