<p><p>The cortex is
the neomammalian brain, which is the grey matter. The cortex is the bark of the
brain, “cortex” literally translating to bark in Latin. This part of the brain
continues to develop and mature into the third decade of life, creating our
learned social-emotional behaviors, and emotions. Higher-level primates
(including humans) oscillate at faster frequencies here. This layer of the
brain is responsible for all conscious thought, learning, and self-awareness
(MacLean, 1990). Approximately 40,000 years ago, with the Cro-Magnon man, both
hemispheres of the brain underwent a major functional reorganization. It was at
this time that the frontal lobes increased in size, bonding processes (sexual
and social) became more complex, and the ability to communicate and express
ideas began to emerge, notably in drawings, etchings, carvings, and sculpture
(Joseph, 1992, p. 25). It is this third layer of the cortex that allows for
self-conscious awareness, among other qualities (Professor H. LaFace, personal
communication, January 25, 2013).</p>

<p>In a cortical
organization, neurons are arranged in layers and the neurons in each layer are
functionally alike and different from those in other layers. The crinkled sheet
of nerve cells (grey matter) that is the cortex is 1/5” thick.&nbsp; This is the house of the highest level of
neural processing (e.g. language, memory, cognitive functioning). The cerebral
cortex can be divided into areas concerned with particular functions. What lies
underneath the cortex is considered white matter.</p>

<p>Cortical
interneurons make up 1/5 of the cortical neuronal population (65) and release
the inhibitory neurotransmitter GABA (gamma-aminobutyric acid). Although they
are outnumbered, interneurons innervate principle neurons at strategic places
and with synaptic terminals, which allows for Inhibitory Post Synaptic
Potentials (IPSPs)&nbsp; to approximately
match the effects of excitatory postsynaptic potentials (EPSPs). It is through
this dance that the balance of cortical activity is established.</p>

<p>Brain systems
with “simple” computational demands evolved only a few neuron types. The
thalamus, basal ganglia, and cerebellum possess a low degree of variability in
their neuron types. In contrast, cortical structures have evolved not only five
principle-cell types, but also numerous classes of GABAergic inhibitory neurons
(Buszaki, 2006).</p><img src="@@PLUGINFILE@@/evolution.png" alt="Evolution" width="663" height="391" class="img-responsive atto_image_button_text-bottom"><br></p>