In the previous article we talked about empathy, as the capacity to put ourselves in someone else’s shoes and understand them. We discussed about the structures involved, in a quite simplistic manner, but as it turns out things are not that simple. What makes the brain so fascinating (and hard to study as well) is the fact that each and every process, from the basic to the more advanced ones (like reasoning, planning, decision-making) require the integration of many different structures and other processes, that in turn depend on other processes and so on. A bit confusing, isn’t it? Don’t worry! If you feel lost, then you’re actually on the right track.  

Mirror neurons represent one of the basic keys behind empathy (as presented in the previous article), but they don’t explain the whole picture, though. In order for us to be able to relate to a complete stranger’s situation and feel what he’s feeling, we first need to be able to relate to ourselves. More specifically, our brain should be capable of retrieving something from our own past that is similar or triggers similar emotions to what the stranger is experiencing. (This is, of course, involuntarily and subconsciously.)

That’s where memories come in. Memory is a very common term and almost all the people know what it is about. Or do they? In fact, “memory” is quite ambiguous and imprecise; neuroscientists discuss about “types of memory”. Indeed, there are several categories in which memories are classified (visual-spatial memory, auditory memory, emotional memories, long-term memory, short-term memory – if we focus on duration – and so on). 

To spare us of too much confusion, scientists decided to divide memory into two broad categories: declarative (explicit) and non-declarative (implicit) memory. The first one refers to memories for facts and events and is the conscious component, whereas the second one includes the types of memory that don’t have a conscious component, such as memories for skills and habits, priming, classical conditioning, simple forms of associative learning, as well as simple forms of non-associative learning (habituation and sensitization).

A lot of information to take in, I know. But if you’ve manage to get this far, I promise you won’t be disappointed! The big question that has given scientists a hard time for years was: “Where exactly is memory stored?” Initially it was thought that memory is somehow spread throughout the whole brain. Well…it’s not! And we now know this thanks to one of the most famous patients in the history of Neuroscience, Henri Molaison or H.M., as he is referred to in literature.

H.M. had been suffering from epilepsy his entire life and in 1953 he underwent lobotomy to treat his seizures. Thus, he had a part of the brain removed, which included both his left and right temporal lobes. After the surgery, the epilepsy was gone, but instead something else appeared to have taken its place… H.M. was no longer able to form new memories (anterograde amnesia). To him, every day was like a new beginning: everything he did or learnt, all the people he met the day before, were completely new the day after. At least, he never got bored (which allowed neuroscientists to study this patient his entire life, as he couldn’t recall any of the tests he participated in). 

Interestingly, his old memories (from childhood, for instance) were unaffected and he was even able to learn new things, although he had no recollection o them. Thus, scientists concluded that the temporal lobes and especially the hippocampus were responsible for the formation of long-term declarative memories, but instead this type of memory was stored somewhere else (in the frontal cortex). Also, a different region of the brain is involved with memories for skills and habits (the striatum). Hence, there are specific cortical areas where memories are encoded.

This article is just to give you a bit of an understanding of how the brain deals with basically sorting our entire lives into distinct, separate “folders”, but it’s not even close to covering this whole vast subject. At some point, you might come across another article about a special type of memory that was recently discovered. 

Did memory manage to arouse your curiosity? If so, I’m looking forward to comments.  

P.S. I would like to give very special thanks to Sorin Hornoiu and Isuru Pryiaranga, who created the images for the first article and this one, respectively. I try as much as possible to use original pictures (not downloaded from the internet) and their creative skills really come in handy.