<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><p><br></p><p style="text-align: center;"><img src="@@PLUGINFILE@@/the-cortex.jpg" alt="" width="663" height="391" role="presentation" class="img-responsive atto_image_button_text-bottom"><br></p><p style="text-align: left;">MacLean noted the unconscious reptilian and limbic brain regions influence the higher ordered neomammalian brain. The cortex consists of “bumps,” called gyri (“gyrus” is singular) and “grooves” called sulci (“sulcus” is singular). Some anatomists call the deepest sulci “fissures” (Catani &amp; Thiebaut de Schotten, 2012, p. 8).<br></p>