fMRI Identifies New Patterns of Brain Activation Used in Formation of Long-Term Memories

Investigators have identified patterns of brain activation associated with the formation of long-term memories. The study also revealed an innovative and more comprehensive method for evaluating memories.

Investigators asked study participants to recall the content of a television situation comedy, which more effectively simulated real-life experiences because it required retrieving material that occurs in more complex settings than typically exist in a laboratory environment.

Making sense of and recalling the complicated, multi-sensory information seen in daily life--such as reading a newspaper while listening for a boarding announcement at the airport--is an essential task that the brain easily accomplishes. What is less obvious is which regions of the brain are utilized to encode these experiences. Earlier studies had examined neurologic activity critical for effective memory encoding, but the research had not simulated the real-world settings in which long-term memories are typically formed. Instead, they frequently rely on recollection of single images or simple words.

By contrast, the researchers, from New York University (New York, NY, USA) and the Weizmann Institute of Science (Rehovot, Israel), tried to replicate the every-day environment in which memories are typically created to provide a more realistic assessment of the relevant neurologic activity. They did so by having the participants view an episode of a TV sitcom in its entirety.

As the subjects watched the episode, the researchers used functional magnetic resonance imaging (fMRI) to examine their brain function. Three weeks after the video was viewed, the participants returned to answer a series of questions about its content. The investigators then used the memory performance of the volunteers to analyze their brain activity during movie viewing. Using a novel intersubject correlation analysis (ISC), the study revealed brain regions for which this correlation is greater during successful, or accurate, as compared to unsuccessful memory formation.

This method allowed the researchers to identify brain networks whose activation waxes and wanes in a similar way across participants during memory formation as well as other regions where activation was important for memory formation but which showed individual variability. These different patterns may clarify why it is that after experiencing something together, we can share facets of memory for that event, but those memories also have an individual flavor or personal tone.

Traditional experiments, which relied on simple words or still images, have consistently revealed that the brain's medial temporal lobes (MTL) and inferior frontal gyrus (IFG) are active during memory formation and retrieval. These regions were also active in the NYU-Weizmann study. However, the researchers also found activity in new areas: the brain's temporal pole, superior temporal gyrus (STG), medial prefrontal cortex (mPFC), and temporal parietal junction (TPJ).

These brain areas have all been implicated in various aspects of social cognition: understanding the intentions of others, simulating experiences, language comprehension, and even person perception.

The study was published in the February 7, 2008, issue of the journal Neuron.


Related Links:
New York University
Weizmann Institute of Science