The brain is called the cerebrum, it is about 3.3 pounds in weight and 75% of the weight is water. the mass of the brain tissue consists of about 50% fat. This
The brain is covered in a wrapping of grey matter called the cerebral cortex. Grey matter is the nerve cells that do not have an insulation on them called myelin. The myelin insulation helps the nerve information travel more directly, the grey matter or unmyelinated neurons can send, connect and hold information. White matter covered nerves can send impulses at 150 meters per second, while grey matter cells tend to send information at about 5-10 meters per second.
This grey matter covering, if flattened out is about 2.5 mm thick and about Or about 1935 square centimeters that is around 300- square inches, so think of a square 17" by 17"... That, according to my findings is about the size of an average adult male, of course that is totally different for children and people that are either smaller or larter. The brain though sits in the skull, technically called the cranium. The cerebrum (brain) sits in a bath of fluid inside that case, but it is not 17 inches square. The cerebrum has all sorts of folds and bumps and grooves. The bumps and grooves on the surface of the brain were once thought to be pretty similar with everyone. That is, most people seemed to have the same gyri (those are the bumps) and sulci (the grooves). However, since we have been studying much more about the brain and the similarities and differences among people we have found a few new things. These convolutions (as they are also called) are more pronounced and the sulci are deeper and the gyri are bigger or closer together depending on how much activity occurs in that part of the brain. For example, when Albert Einstein died many scientists were interested in his brain. Figuring they could find out which parts of the brain he used to be so smart they dissected it after he died (of course). Curiously, they did indeed find an area of his brain that was more 'wrinkly' than other parts or other brains from similar aged men. That area was on the right side about where the corresponding nerves that control the hand are located. This was confusing at first, but when they finally realized that Mr. Einstein would practice the violin in order to relax and think about the problems, it all seemed to make sense. They never did find an area in his brain that seemed to correspond with 'physics' or math, but with more advances in functional MRIs and the like we are getting closer. Currently, brain scans have been done on criminals and those that are diagnosed as psychopathic. These scans do show differences than the average brains in the prefrontal cortex. It has long been assumed that there would be structural changes in the brains of those that have aggressive tendencies. If you remember the film Young Frankenstein, the brain that Igor brought back was from 'Abby Normal' which turned out to actually be 'Abnormal'. Which although was a gag for the film, was rather true to what we find in science today.
Gyri can be wide or narrow, they can be rounded or flattened. Now rounded or flattened have not been studied and we cannot at this time know what that means, nor do we know if them being wider has any difference in thinking, abilities or other factors related to personality traits.
In general we have an ok idea of what areas of the brain do what, but there is still much to learn. The general idea is that the front areas (called the prefrontal cortex) is responsible for planning and 'higher thinking' this is where it is also thought that personality lies. Other basic areas are the top sides of the brain (called the parietal cortex) is where we sense pain, touch and temperature. The back of the brain, called the occipital cortex is where vision is perceived, and the sides (temporal cortex) is where hearing and language is produced. That is the most general aspect of the brain topography (surface). Other functions are in smaller areas and since there are two halves of the brain there are more subtle actions on either side. Right now we will just concentrate on the basics of the four lobes; frontal, parietal, temporal and occipital. There are also other parts of the brain we can touch on later, the cerebellum, midbrain, diencephalon, corpus callosum and the insula.
When you fold and scrunch up that 300 square inch cortex it can be folded into the small space that is our cranium. Turns out though that some people can have over 400 square inches and it can be over 3 mm thick! That is a lot of brain tissue to stuff into that small brain case (the cranium)!
MEDITATION: So what does this have to do with meditation? Well, we find that those that meditate can have a great variation in not only the topography of the brain but also the size of areas inside the brain as well. We now know that places in the brain like the amygdala, which is linked with fear and aggression do decrease in size as we practice more meditation and that in people that are aggressive, like the psychopaths I mentioned, have larger amygdalas.
Meditation has shown to increase the thickness of the cortex especially in the prefrontal cortex. but how? When you use more neurons and use them more frequently those established connections become stronger and take up more cell space. That would account for the thickness. As more and more of the brain tissue is used it begins to grow, and since it cannot grow to the sides it has to fold over, bigger gyri and sucli result. One common idea is that 'neurons that fire together wire together' a phrase coined by Psychologist Donald O. Hebb, now it is called 'Hebbs Law'. Although more current research does better explain the physiology and neuronal growth, pairing down and reconnections made as we age, learn and grow, it is still considered a useful 'law' of psychological brain theory.
We do know these areas which I will cover in more detail later.
Left Precentral Gyrus: Called by some the Motor Strip or the primary motor cortex. On the lateral surface of each frontal lobe, anterior to the central sulcus and runs parallel to the central sulcus. This is part of the body-motor or somatomotor cortex. It controls voluntary movements of the opposite side of the body, generally the face and head. If damaged it can cause paralysis of the part of the body it serves. If we do body scans it can get more action and therefore it stands to reason that it would become thicker.
Right Fusiform Gyrus, on the inferior (bottom side) of the temporal and occipital lobes. This is basically just deep to your ear and a little behind it.. It helps us recognize faces and has a special area, the 'Fusiform Face Area' that helps us recognize facial expressions. This area is also implicated in 'Autism Spectrum Disorders' as if there may be damage to those neurons. Oxytocin, a neurotransmitter called also the 'love hormone' is at work here as with an abundance of it we recognize faces easily, and with a depletion of the neurotransmitter we find faces to be unfamiliar and this could be a link for anxiety, fear, paranoia as well as the ASD patients.
Right Anterior Dorsal Insula, (gets more defined with more years of meditation). Remember when we were discussing the four lobes of the brain? The frontal, temporal, parietal and occipital? Well there is one more. It is the insula. (that means basically it is insulated or covered on the outer layers by the frontal, parietal and temporal lobes. It has to do with the sense of interoception, that is the homeostatic emotions of thirst, pain, fatigue. Subjective perceived dyspnea (shortness or difficulty of breath as in a panic attack seems to be registered here). This part, being on the right, dorsal (towards the top or back of the head, and anterior (towards the front) is very close to the amygdala and is a very emotionally related part of the brain. fear, disgust, anxiety and happiness are related to the activity of this area. Oddly if this area is damaged loss of libido, a sense of apathy and the inability to tell fresh from rotten food occurs. This seems to be where the mind and body are integrated... This is the seat of empathy.
Left Anterior Dorsal Insula-See above, although, this area is associated with affective-perceptual and cognitive-evaluative forms of empathy. Cognitive perception is the ability to infer another's thoughts or beliefs. Affective perceptual basically means emotions, amd being able to make inferences about others emotions and feelings. THis is the basis of empathy.
Another very interesting area of the brain, well, a few areas of the brain that do work together is the Default Mode Network. This is the day dreamer part of the brain, active when we are not thinking about something directly. These areas of the brain are also thought to be the 'center of the self'. Our memories and emotional descriptions of ourselves, it seems to not be very analytical, but is reactionary. It is like the brain that keeps track of the brain. Now very linked to things like depression, anxiety and reactionary issues.
A lot of this is in the realm of cognitive science and psychology, but now the science of meditation is showing it has a stake at the table too. Now that we are getting an idea of the functions of the different parts of the brain as well as the combination of those functions and the emotional association areas we can start to ask;
"So how do we enhance or work with that within the meditative arena of techniques? "
Well, that is my question indeed .
White matter changes: https://www.healio.com/news/psychiatry/20120620/mindfulness-meditation-associated-with-changes-in-brain-white-matter?utm_source=TrendMD&utm_medium=cpc&utm_campaign=Healio__TrendMD_1
CNS and ANS changes: https://www.pnas.org/content/pnas/106/22/8865.full.pdf?__cf_chl_jschl_tk__=pmd_DzINzwJG1bVAkltNU8aWhvHM5psU2JU96t56d8r4oO8-1631679209-0-gqNtZGzNAfujcnBszQd9
Neural oscillations related to meditation: https://www.frontiersin.org/articles/10.3389/fnins.2018.00178/full
Posterior Cingulate Cortex and meditation: http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.737.2700&rep=rep1&type=pdf
Anxiety and mindfulness: https://pubmed.ncbi.nlm.nih.gov/20350028/
Default mode increase: https://www.sciencedirect.com/science/article/abs/pii/S0304394010014096
Right Fusiform Gyrus, ASD? https://www.sciencedirect.com/topics/neuroscience/fusiform-gyrus
The RIght Ant Dorsal Insula and empathy. https://www.sciencedaily.com/releases/2012/10/121024175240.htm
Perspective taking and empathy. https://www.frontiersin.org/articles/10.3389/fneur.2018.00491/full
Mammal empathy; https://www.semanticscholar.org/paper/Mammalian-empathy%3A-behavioural-manifestations-and-Waal-Preston/246eafeed9825257764d4c37cbad21558227afca/figure/4
https://www.med.wisc.edu/news-and-events/2011/november/psychopaths-brains-differences-structure-function/
https://www.historyofinformation.com/detail.php?id=3902
https://www.gatewaypsychiatric.com/default-mode-network-and-depression/
