Scientists at the University of Arizona in Tucson are trying to determine what goes on inside the brain when it sees a face. How, for instance, does the brain recognize faces and retrieve the names to go with them? Also, how does the brain determine whether the information that it has retrieved is accurate?
"In other words, how do we know when we come up with a possible memory that it's the right one, as opposed to something we dreamt or imagined," said Alfred Kaszniak, one of the authors of the study.
The lead author of the study, "Feeling of Knowing for Faces: An fMRI Study," Jasmeet Pannu, is a graduate student at the University of Arizona in Tucson. Steven Rapcsak, a UA associate professor of neurology and a behavioral neurologist at the Veterans Medical Center in Tucson, and Kaszniak, a professor and head of the psychology department at the UA, are the other authors. Their latest research is being presented at the annual Society for Neuroscience meeting in San Diego.
Kaszniak said the current study evolved from his ongoing research on Alzheimer's disease. It also may offer other avenues to study memory, first in healthy individuals to see how memory works and changes with age in a normal brain, and then as a way to understand what comes apart in Alzheimer's disease.
"One of the observations we made and have published quite a bit, had to do with persons with Alzheimer's eventually not appreciating that they have a memory impairment. Many individuals as their illness progresses will say 'No, I don't have any trouble with memory,' or will at least not sufficiently appreciate how severe their memory impairment is," Kaszniak said.
He and the others became interested in using faces as a tool because it is a common, real-world issue for people, and "the sort of thing people often complain about having some difficulty with," Kaszniak said.
The specific study used functional magnetic resonance imaging (fMRI) to examine a dozen people, ages 22 to 32, with healthy, developed brains, to measure brain activity. The researchers used the Cognition and Neuroimaging Laboratories at the UA. The subjects viewed 300 famous and not-so-famous faces and reported whether they knew, didn't know, or felt they knew but couldn't immediately identify each face.
Jasmeet Pannu said the results of the study suggest that "while some areas in the brain overlap in activation when one is in a 'feeling-of-knowing' (FOK) state, and when one has successfully retrieved a name, there are also differences."
Specifically the medial prefrontal cortex showed activity during the FOK state that was not active when the subjects either knew or did not know a face. One possible explanation is that activity in the medial prefrontal cortex reflects a state in which subjects were evaluating the correctness of retrieved information related to the famous face shown in the task.
"This process may be especially important during the feeling-of-knowing, in which the target word is actively being sought while alternative information may come to mind, such as syllables of the person's name, profession, other movies or events the person has participated in," Pannu said.
The group also found that the anterior cingulate area of the brain became activated both in the FOK state and when subjects successfully retrieved a name, but with some effort. The anterior singulate area is associated with cognitive conflict processes which allow a person to detect errors in automatic behavior responses.
"It is very sensitive to mismatches between, say, a template, a stored set of facts about people and faces, versus the individual face that you can't quite come up with a name for. It detects that kind of discordance. It's these middle frontal potions, though that are uniquely involved in when an individual thinks they know a name, but cannot immediately retrieve it," Kaszniak said.
Most memory research in the past focused on either successful retrieval or not knowing, and ignored any stored knowledge not available for retrieval, Pannu said. This study is an attempt to understand what the brain is doing during the FOK state, and the results suggest that the brain may be enlisting additional processes to aid in recalling accurate memories.
Pannu said that although "there are a few other neuroimaging studies investigating FOK, our exact findings have not been reported before."
It is one of the first step in being able to uncover changes in the memory retrieval process that occur when people age.
Early diagnosis is one of the central target areas for researchers at the UA and the statewide Alzheimer's Research Center.
Kaszniak said the next step will be a study among older adults of something called the "tip-of-the-tongue" phenomenon, or the increasing inability to retrieve a name as people age.
"We would like to know what it is in peoples' brains that accounts for that. We think that on the basis of this (current) study we know where to look in the middle frontal area, but we need to find out whether in fact that is the case, or if it is going to show differences between younger and older adults," Kaszniak said.
Alfred W. Kaszniak
UA psychology dept.