The Memory Circuit

      In 1997, a doctor named Itzhak Friend experimented on a number of his epilepsy patients.  He placed tiny brain activity monitors, or electrodes, in various regions of the patients' brains, and he then flashed various images of Marilyn Monroe at different rates to them.  He had found that the same neurons, in a given patient's brain, were stimulated by different, yet similar images of Marilyn Monroe, as long as those neurons had been first exposed to a picture of her for the duration of a minimum time frame (less than a sixth of a second).  Those neurons were also stimulated when the individual saw Monroe's name.  Fried concluded that sets of neurons such as the ones stimulated by Marilyn Monroe are capable of retaining the "idea" of something (a place, an individual, etc.), for a brief period of time, and will be excited by stimuli which are similar to that idea.  I stipulate this ability to be what I will refer to as short-term plasticity, or the ability of neurons to briefly alter their synaptic connections when posed with same or similar yet repeating stimuli in a small period of time (Plasticity, or neuroplasticity, is an ability of neurons I describe in my post "Habits, neuroplasticity, and the origin of emotion).  Furthermore, this process is, essentially, the beginnings of a newly forming memory, and can be converted to one via long-term potentiation: the ability of neurons to alter their synaptic connections, in accordance with incoming stimulus, and to maintain that alteration for longer periods of time.  But how and why does this conversion occur?
     Memories tend to be more intense, and can be recalled more easily, if there is emotion associated with them.  An example of this would be what is called, commonly, emotional scarring.  This entails a situation which is so traumatic, or negative, in relation to a given individual, that the events of this occurrence are "burned" into the individual's mind ad infinitum.  I would further convict that not only emotion, but the more mental processes, or faculties, involved in the memory, the more easily it can be recalled.  For instance, learning is found to be easier if the subject interests the learner.  Learning, as I had described in my post "The Genius Gene," is the process of the brain synthesising a new conclusion from multiple previously held memories that it deems axiomatic.  Moreover, the brain is able to focus more of itself on certain processes or activities that it deems interesting via more widespread releases of a chemical called norepinephrine.  Norepinephrine is involved in enhancing the vigilance, or attention to stimuli, of a given individual, and widespread releases of it will act on multiple regions of the brain, causing these regions to focus, more so, on the interesting process or activity.  Therefore, the memory of the aforementioned new conclusion will be more easily remembered by the learner, if the subject at hand is one they find interesting.  Another example of multiple mental faculties allowing easier recall of a given memory, as well as the associated memory or sensory information, would be cognitive association.  The reason you are "reminded" of a particular memory in relation to an incoming stimulus is because one of the three lobes of the cerebrum responsible for cognitive association (the temporal, parietal, and occipital lobes) have associated that stimulus with the memory.  And, the more stimulus associated with a memory, the greater the probability of, as well as ease in, the brain's recollection, because multiple different regions of the cerebrum would be involved in that remembrance (the brain is able to process more quickly depending on the amount of white matter involved in making the relevant connections, ergo the more regions of the brain involved, the faster the recollection).  This concept correlates directly with multiphasic cognitive relay, a process I describe in my post "Subjective Perception."  I suppose that just as multiple cognitions create the illusion of the individual being aware of that cognition, and just as multiple cognitions or mental faculties involved in the recall of a memory speeds up the process, the individual will be aware of that recall so long as multiple different cognitive associations are made by the cerebrum.  In other words, the individual will become aware of the recollection of a memory if the brain had processed and stored multiple different stimuli regarding that memory, and if that information is being associated with other multiphasic cognition, be it present perception, past perception, or the frontal lobe formulating a strategy or behaviour.  The remaining question, though, is how are these memories converted from short-term plasticity to long-term potentiation, and then stored?
     A set of proteins, known as protein kinase, are responsible for a number of different regulatory functions.  A recently discovered class of protein kinase, known as PKM-Zeta, is the single protein which is responsible for the maintaining of long-term potentiation between neurons.  This protein acts as a sort of "glue" which keeps intact the altered synaptic connections, connections originally altered by the preceding short-term plasticity.  Moreover, as I had stated in the previous paragraph, that the more mental faculties involved in a memory, the more easily it can be recalled, I stipulate that this is due to the nature of memory storage in the brain, a nature which I will describe as a memory circuit.  A memory circuit is an interconnecting set of neurons, held together in the long-term by PKM-Zeta, that processes, or "loops," through the different regions of the brain that had been active in regards to the memory at the time of said memory.  These regions are then stimulated in the same or similar manner as they had been, and this similar stimulation causes the individual to be "reminded" of the previous instances when it had occurred.  As discussed in my post "Habits, Neuroplasticity, and the Origin of Emotion," neurons can undergo neuroplasticity and alter their synaptic connections in such a way that matches repeated stimuli, and I further stipulate that this neuroplasticity is the foundation on which a memory circuit is formed by the brain.  As my final point, I convict that short-term plasticity is converted to long-term potentiation so long as the repeating stimuli which caused the short-term plasticity is repeated for a longer period of time.  This time frame can vary depending on the intelligence, or speed at which an individual's brain makes connections, of the given individual. 
    I have been receiving a number of requests to create entries in regards to a number of different concepts, such as drugs and positive association.  I will, in due time, write these, however for now I must start with one of the principal bases of brain function: the memory circuit.