Research lead by Dr. Clea Warburton and Dr. Gareth Barker at the University of Bristol has identified the reasons behind why, in some occasions, we are unable to link a face to a name. When we meet a person for the first time, we do not only pay attention to the person we're speaking to, we pay attention to the setting and the point in time all at once. This higher level function has been found to require three particular regions of the brain to work together for recognition: the Perirhinal Cortex for the ability to recognize whether an object is novel or familiar, the Hippocampus for recognizing setting and navigation, and the Medial Prefrontal Cortex for higher cognitive functions like remembering the conversation that took place (Science Daily). These three regions of the brain work together by forming a circuit for complete recognition, the answer to why we may not remember is because of the lack of or little strength in the particular stimulus' connection between the regions.Dr. Anthony J. Ryals in his presentation on "The Continuum of Awareness in Recognition Memory" describes this experience as the "Butcher on the Bus" phenomenon. Let's say you recognize the person on the opposite side of the bus from you but you can't quite put together where you know the individual from. Why? Probably because he isn't across the Deli counter slicing your ham at your go-to grocery store. However, as soon as he gets off the bus to get to work and you see his destination, it all of a sudden clicks. You know exactly who this person is. Your perirhinal cortex recognized him as familiar but your hippocampus was missing the context of where you know the familiar face from. Once you recognized the setting your full circuit is stimulated and the higher levels of your brain, such as the medial prefrontal cortex, reminds you of the conversation and small talk you've had while choosing between the honey roasted or smoked ham.
In Ryals research, he describes Recognition Memory to be made up of two types: Implicit and Explicit memory. He describes implicit memory to be found in the Perirhinal Cortex as non-declarative memory that is formed without an individual's awareness such as skills, habits, and non associative learning. Opposite to implicit, he describes explicit memory as declarative factual knowledge formed in the hippocampus which makes memories that we are aware of and are able to freely recall (Ryals). In the Science Daily article "Have we met before? Scientists show why the brain has the answer" Dr. Warburton believes that the discovery of the connection between these regions teach us how memory formation is processed within and can teach us a further understanding of how our 'internal library' system works.Significant evidence of this circuit has been found studying the case of patient H.M. who experienced profound memory loss after the removal of his hippocampus and surrounding structures of the medial temporal lobe. The disconnection of these regions prevented his ability to form new memories, however, he has no problem learning new games and improving in them. His explicit/declarative memory was lost in the removal of the hippocampus losing his ability to make new memories and learning new declarative factual knowledge such as the names of places, and episodic memories. Despite this issue, since parts of his implicit memory had stayed in tact, patient H.M. was still able to perform implicit indirect tasks that mostly relied on Perirhinal and Medial prefrontal cortex such as the learning new board games and improving his skill, even though he would not be able to explain how he did so.
New memories in recognition cannot be formed or explicitly declared if the communication between the hippocampus, the perirhinal cortex and the medial prefrontal cortex is broken (Science Daily). The ability to remember requires all of these regions to act together as a unit with some topics more reliant on one area then another. Determining these regional connections has made important implications for understanding memory and could lead to effective treatments for individuals that suffer with memory disorders such as Alzheimer's and Amnesia.
References
University of Bristol. "Have we met before? Scientists show why the brain has the answer." ScienceDaily. ScienceDaily, 4 August 2011. Ryals J. Anthony, Voss L. Joel. The Outer Limits of Implicit Memory. 2015
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Picture 2: https://www.cg.tuwien.ac.at/research/publications/2013/sorger-2013-neuromap/sorger-2013-neuromap-teaser.jpg
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