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Dorsal, Ventral and Intermediate Prefrontal Cortex – Scientific Facts

Brain hemispheres sliced into upper, middle and lower thirds result in the following:

  1. Upper / dorsal prefrontal cortex, primarily processing “where”, is also associated with so called “cold cognition”, perceptions, executive memories and plans.
  2. Lower or ventral prefrontal cortex, processing “what”, is mainly made up by orbital cortex and ventromedial PFC, and
  3. Middle or intermediate PFC, mainly processing “when” is also involved with language and mirror neuron system.

People with autism lack theory of mind but not empathy, while people with psychopathy lack empathy but not theory of mind. Without empathy one can still have sympathy, though.

Brain circuits mature during different stages of development, therefore some are completely integrated only when one is in the sixties, which appears to be typical peak time of human insight, understanding the realms of life, and cognition.

Psychopath’s brain scans show decreased activity in the orbital cortex – involved in inhibition, social behaviour, ethics, and morality.

In psychopaths, there seems to be a loss of activity from the orbital cortex into the ventromedial prefrontal cortex and into the anterior cingulate.

“A psychopath has a poorly functioning ventral system, usually used for hot cognition, but he can have a normal or even a supernormal dorsal system, so that without the bother of conscience and empathy, the cold planning and execution of predatory behaviours becomes finely tuned, convincing, highly manipulative, and formidable. Because psychopath’s dorsal systems work so well, they can learn how to appear that they care, thus making them even more dangerous.”*

Some facts about genetics:

Human genome contains about twenty thousand genes located in forty-six chromosomes (twenty-three pairs), one pair set from each parent, in the nucleus of most body cells. The germ cells in the testes and ovaries are the only cells that don’t contain all forty-six chromosomes, but only twenty-three chromosomes each.

Chromosomes are composed of DNA – the master blueprint of a cell – coded on a sequence of four chemicals (bases). “The bases sit in pairs with T (thymine) coupled with A (adenine) and G (guanine) coupled with C (cytosine). The forty-six chromosome (diploid) genome contains over six billion base pairs. Sequence of base pairs, called genes, code for any produce gene products such as proteins. If just one of the base pairs is altered by mutation, say from ultraviolet damage, a virus, or cigarette smoke, the resulting protein will be aberrant, and usually faulty.”*

Single nucleotide polymorphisms (SNPs – about twenty million found in humans) are mutations that are not fatal thus they are kept by the cells, accounting for many differences in the appearance and behaviour of humans, from hair colour to drug addiction.

On the other hand, alterations in the genetic code involve genes that regulate the gene’s ability to make products, such as promoters and inhibitors that act like the gas and brake pedals of a gene, controlling the delivery of neurotransmitters (like serotonin and dopamine) in the brain.

Serotonin is implicated in depression, bipolar disorder, sleep and eating disorders, schizophrenia, hallucinations and panic attacks, as well as psychopathy; the breakdown enzyme is MAO-A. The version of the MAOA gene with the short promoter, the “warrior gene”, has been associated with aggressive behaviour.

Drugs that enhance dopamine transmission can alleviate symptoms of depression, while drugs that decrease dopamine transmission, can alleviate schizophrenia.

Dopamine is mostly produced in the midbrain.

GABA (gamma amino butyric acid) – an inhibitory amino acid, together with glutamate – an excitatory, make the two most important neurotransmitters.

Serotonin, dopamine, and norepinephrine are the neurotransmitters most implicated in psychiatric disorders from schizophrenia to depression, and bipolar disorder. Antidepressants used (Prozac, Zoloft, etc) are SSRIs – selective serotonin reuptake inhibitors.

Serotonin is released early on, during foetal brain development, as it is one of the earliest neurotransmitter system to be developed.

Dopamine appears to have a role in psychopathy, in addition to serotonin.

 

*“The Psychopath Inside: A Neuroscientist’s Personal Journey into the Dark Side of the Brain.” – James Fallon

**Exercise Physiology – Understanding the Athlete Within – The University of Melbourne

***Synapses, Neurons and Brains – Hebrew University of Jerusalem

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