Sweet, sweet: Memorable image

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  • Published: Sep 1, 2011
  • Author: David Bradley
  • Channels: MRI Spectroscopy
thumbnail image: Sweet, sweet: Memorable image

More effective brains

A new functional magnetic resonance imaging (fMRI) study in the US shows that our memories seem to work more effectively when our brains are prepared to absorb new information.

John Gabrieli of the McGovern Institute for Brain Research at Massachusetts Institute of Technology (MIT) and colleagues investigated the parahippocampal cortex (PHC) and found that based on activity could predict how well people will remember a visual scene. Writing in the journal NeuroImage, the team used fMRI to show levels of activity in the PHC before people were shown an image and to then correlate this activity with how likely the volunteers were to remember the image later.

The PHC encompasses the parts of the brain known as the posterior parahippocampal gyrus and the medial portion of the fusiform gyrus. The former is a "grey" matter cortical region of the brain surrounding the hippocampus (known to be critical to memory formation) and is thought to play an important role in memory encoding and retrieval. The fusiform gyrus is part of the temporal lobe in Brodmann Area 37 and although there is some dispute as to its actual function it is thought to be involved in the processing of colour information, face and body recognition, and possibly even word and number recognition.

The team examined a specific part of the parahippocampal gyrus, a posterior part that includes a region that responds maximally to scenes or locations and therefore described as the "parahippocampal place area".

Voluntary response

The team showed volunteers 250 colour photographs of indoor and outdoor scenes as they lay in an fMRI scanner. They were later shown 500 scenes, among which were the original 250, to test how well they could recall the first batch of images. The exact area of activity associated with lower recall of the images was slightly different for each volunteer, but was always located within the PHC.

"When that area [the PHC] is busy, for some reason or another, it's less ready to learn something new," explains Gabrieli. This study is the first to investigate how PHC activity before a scene was presented would affect how well the scene was remembered, according to lead author of the NeuroImage paper Julie Yoo, a postdoctoral researcher at the McGovern Institute.

The team also carried out a second experiment in which they used real-time fMRI to monitor the volunteers moment to moment. They discovered that when the brain was in a "ready" state, the volunteers could better recall the images that had seen previously, compared with those in a "not ready" state. The finding hints at why we can sometimes remember certain things better than others. It was previously thought that memory is simply based on the inherent memorability of specific events, with strongly emotional events most likely to be remembered more vividly. However, there were hints from cognitive neuroscience that the brain's ability to consolidate, store and retrieve information is also important to recall. This work suggests that how well memories are made does not depend solely on memorability but on brain activity at the time.

Educational impact

There are implications from these findings for education. In theory, it might be possible to determine when a student is best prepared to learn new material, or to monitor workers who need to stay alert. "That's what we would like to think -- that we are able to measure states of receptivity for learning, or preparedness for learning," Gabrieli says. "In terms of how that would be translated to real life, there are still a few steps to go." The biggest stumbling block is that we do not yet have portable and inexpensive fMRI scanners that might be used in schools and colleges or the workplace! However, with the known involvement of the PHC in memory formation and recall it might be possible to use the much more portable electroencephalography (EEG) as a proxy for fMRI. Indeed, the team is currently working on finding a way to correlate EEG measurements with the known fMRI activity so that it might be used as a surrogate for the more sophisticated scanning technique.

 


The views represented in this article are solely those of the author and do not necessarily represent those of John Wiley and Sons, Ltd.

 A new functional magnetic resonance imaging (fMRI) study in the US shows that our memories seem to work more effectively when our brains are prepared to absorb new information.
 

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