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<p style="text-align: center; "><img src="@@PLUGINFILE@@/cortex2.png" alt="cortex" width="477" height="348" class="img-responsive atto_image_button_middle"><br></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.&nbsp;</p>
<p>This layer of the brain is responsible for all conscious thought, learning, and self-awareness. 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. It is this third layer of the
    cortex that allows for self-conscious awareness, among other qualities.</p>
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<p style="text-align: center;"><img src="@@PLUGINFILE@@/cortex.jpg" alt="cortex" width="500" height="307" class="atto_image_button_middle" style="font-size: 1rem;"></p>
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<p style="text-align: center; "><img src="@@PLUGINFILE@@/evolution.png" alt="evolution" width="663" height="391" class="img-responsive atto_image_button_middle"><br></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.<br></p><p></p><p>The cerebral cortex is the most complex structure of the human brain. It has a wide spectrum of functions, including planning and initiation of motor activity, perception and awareness of sensory information, learning, memory, conceptual thinking, awareness of emotions and many other.</p><p>In order to be able to perform all the above functions, the cerebral cortex has a unique, multilayered arrangement of the neurons. In the next paragraphs, we will analyze this arrangement as well as the different types of neurons that we find in the cerebral cortex.</p><p></p><h3>Cortical Cells in the Brain</h3><p>There are two primary types of brain cells: neurons and glia. Neurons are the nerve cells of the brain, and glia are the cells that surround the neurons. Glia were once thought to be merely the scaffolding that supported the neurons, but in recent times the variety of their functionality has been unovered. Glia are responsible for a whole host of things, including hemodynamics, the production of cerebral spinal fluid, inhibition and excitation, the removal of debris and dead cells, the metabolism of neurotransmitters, and many other functions.&nbsp;</p><p></p><p>Neurons are organized in layers, or laminas, parallel to the surface of the brain, and layers are differentiated between each other by the size and shape of the neuronal bodies.<br>&nbsp;<br><b>There are six layers of cerebral cortex:</b></p><ol><li>Molecular (plexiform) layer</li><li>External granular layer</li><li>External pyramidal layer</li><li>Internal granular layer</li><li>Internal pyramidal layer</li><li>Multiform (fusiform) layer</li></ol><p></p>
<p style="text-align: center; "><img src="http://neurones.co.uk/Neurosciences/Images/1/layers-of-cortex%20Kandel%20and%20pyramdal.jpg" alt="Neurones.co.uk"><br></p>

<p><img src="@@PLUGINFILE@@/Pyramidal%203.jpg" alt="" width="600" height="913" role="presentation" class="img-responsive atto_image_button_left"><br></p>
<p>Different staining techniques reveal different cellular structures and different layers of cells.&nbsp;<br></p><p>The cerebral cortex consists of the hundreds of billions of neurons, and all of them are different variations of only three morphological shapes:&nbsp;<strong>pyramidal</strong>&nbsp;<strong>cells</strong>,&nbsp;<strong>fusiform cells</strong>&nbsp;and&nbsp;<strong>stellate (granular cells)</strong>. Other types of cells seen in the cortex are a modification&nbsp;one of those three. The other cells are&nbsp;<strong>horizontal</strong>&nbsp;<strong>cells</strong>&nbsp;<strong>of Cajal-Retzius</strong>&nbsp;and&nbsp;<strong>cells of Martinotti</strong>.<br></p><p><u>The first laye</u>r is the&nbsp;<strong>most superficial layer</strong>, laying directly under the pia mater.&nbsp;This layer is very poor with cellular component, which is represented by only a few&nbsp;<strong>horizontal cells of Cajal-Retzius</strong>. The major portion of this layer is actually the&nbsp;<strong>processes of the neurons</strong>&nbsp;lying within the deeper layers and their synapses</p><p><span><u>The second layer</u> is composed of mostly stellate cells.&nbsp;</span><strong>Stellate (granular) cells</strong>&nbsp;are usually small, and since their processes projects in all planes, they resemble a star. They are located all over the cortex, except for the most superficial layer. Their processes are very short and project locally in the cortex, with the role to modulate the activity of</p><p></p><p>The existence of these small cells in this layer gives that “granular” appearance to this layer, hence its name.&nbsp;</p><p>Cells of this second layer send their dendrites to various layers of the cortex, especially the molecular layer, whereas their axons travel deeper to the cortex, synapsing locally. Besides that intracortical synapsing, axons of this layer can be long enough to form the&nbsp;<strong>association</strong>&nbsp;<strong>fibers</strong>&nbsp;that travel through the white matter to finally end in the different structures of the CNS.</p><p></p><p>Based on whether or not the dendrites of stellate cells have dendritic spines (small cytoplasmic protrusions), they are referred to as spiny cells or aspiny cells.&nbsp;Dendrites of&nbsp;<strong>spiny</strong>&nbsp;<strong>cells</strong>&nbsp;do have spines and they are mostly placed within the layer IV where they release glutamate, which is an excitatory neurotransmitter, so they are functionally&nbsp;<strong>excitatory</strong>&nbsp;interneurons.&nbsp;<strong>Aspiny</strong>&nbsp;<strong>cells</strong>&nbsp;release gamma-aminobutyric acid (GABA) which is the most potent inhibitory neurotransmitter of the CNS, so they function as&nbsp;<strong>inhibitory</strong>&nbsp;interneurons.</p><p></p><p><u>The third layer </u>(the external pyramidal layer) consists predominantly of the&nbsp;<strong>pyramidal</strong>&nbsp;<strong>cells</strong>. The superficial cells of this layer are smaller than the deeper layer, that is very large.&nbsp;<span style="font-size: 1rem;">The apical dendrites of these cells extend superficially and reach the molecular layer, whereas the basal processes join the subcortical white matter and then project again to the cortex, so they serve as both&nbsp;</span><strong style="font-size: 1rem;">association</strong><span style="font-size: 1rem;">&nbsp;and&nbsp;</span><strong style="font-size: 1rem;">commissural</strong><span style="font-size: 1rem;">&nbsp;corticocortical fibers.</span></p><p></p><p><strong>Pyramidal cells</strong>&nbsp;make up to 75% of the cellular component of the cortex and they are the main output neurons of the cerebral cortex. They vary in size, going from small to gigantic.&nbsp;&nbsp;Usually, they have one long axon that leaves the cortex and enters the subcortical white matter.&nbsp;<br></p><p><u>Layer four&nbsp;</u>is the&nbsp;<strong>main input</strong>&nbsp;cortical station (meaning that most of the stimuli from the periphery, arrive here), and for that reason, it is specially developed within the sensory areas.&nbsp;<span style="font-size: 1rem;">It consists mostly of the&nbsp;</span><strong style="font-size: 1rem;">stellate</strong><span style="font-size: 1rem;">&nbsp;</span><strong style="font-size: 1rem;">cells</strong><span style="font-size: 1rem;">&nbsp;and a smaller portion of the&nbsp;</span><strong style="font-size: 1rem;">pyramidal</strong><span style="font-size: 1rem;">&nbsp;</span><strong style="font-size: 1rem;">cells</strong><span style="font-size: 1rem;">. The axons of the stellate cells remain in the cortex and synapse locally, whereas the axons of the pyramidal cells synapse deeper within the cortex, or they leave the cortex and join the white matter fibers.</span></p><p>Stellate cells, as the dominant cellular component, contribute to the formation of specific sensory cortical areas. Those areas receive fibers mostly from the thalamus in the following order:</p><ul><li>Stellate cells of the&nbsp;<strong>primary sensory cortex</strong>&nbsp;receive fibers from the&nbsp;<strong>ventral posterolateral (VPL)</strong>&nbsp;and&nbsp;<strong>ventral posteromedial (VPM) nuclei</strong>&nbsp;of the thalamus</li><li><strong>Primary visual cortex</strong>&nbsp;receives fibers from the&nbsp;<strong>lateral geniculate nucleus</strong></li><li><strong>Stellate</strong>&nbsp;<strong>cells</strong>&nbsp;from primary auditory cortex receive projections from the&nbsp;<strong>medial geniculate nucleus</strong></li></ul><p>When these sensory fibers “penetrate” the cortex, they turn horizontally so they can spread and diffusely synapse with the cells of the&nbsp;<strong>internal</strong>&nbsp;<strong>granular</strong>&nbsp;<strong>layer</strong>. Since these fibers are&nbsp;<a href="https://www.kenhub.com/en/library/anatomy/the-myelin-sheath-and-myelination">myelinated</a>&nbsp;and therefore white, they are clearly seen in the environment of the gray matter. This stripe of the white matter is called the&nbsp;<strong>outer</strong>&nbsp;<strong>stripe</strong>&nbsp;<strong>of</strong>&nbsp;<strong>Baillarger</strong>. Since the stripe is grossly prominent in the primary visual cortex, it is referred to as the&nbsp;<strong>stripe of Gennari</strong>&nbsp;to make it distinctive.</p><p></p><p></p><section id="section13"><p><u>The fifth layer</u> consists predominantly of the medium-sized and large&nbsp;<strong>pyramidal</strong>&nbsp;<strong>cells</strong>. It is the source of the&nbsp;<strong>output</strong>&nbsp;or corticofugal fibers. For that reason, it is most prominent within the motor cortex from which it sends fibers that mediate motor activity. The primary motor cortex contains a specific form of these cells, called the&nbsp;<strong>cells of Betz</strong>.<br></p><p>This layer also contains a horizontally oriented stripe of the white matter which is called the&nbsp;<strong>outer stripe of Baillarger</strong>. It is formed by the axons of the internal pyramidal layer that synapse locally within the layer, and also with the cells of the layers II and III.</p><p><u>The sixth layer</u> is the deepest layer of the cortex that directly overlies the subcortical white matter. It contains mostly&nbsp;<strong>fusiform</strong>&nbsp;<strong>cells</strong>&nbsp;with less dominant pyramidal cells and interneurons</p></section><section id="section14"><h3><br></h3></section><br><p></p><p><img src="@@PLUGINFILE@@/Pyramidal%201.jpg" alt="Pyramidal 1" width="900" height="1148" class="img-responsive atto_image_button_text-bottom"><br></p><p><img src="@@PLUGINFILE@@/Artistic%20Rendering%20of%20PN.png" alt="Pyramidal Neurons" width="752" height="423" class="img-responsive atto_image_button_left"></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, also called cortical interneurons (Buszaki, 2006). One type is the aspiny cells, noted above.<br></p><p><b>Cortical interneurons</b> make up 1/5 of the cortical neuronal population 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<b> Inhibitory Post Synaptic Potentials (IPSPs)&nbsp;</b> to approximately match the effects of <b>excitatory postsynaptic potentials (EPSPs).</b> It is through this dance that the balance of cortical activity is established.</p><p></p><p>A single neuron, when
active, produces an intracellular electric field (that must be measured inside the neuron) and
an extracellular field. The extracellular field of neighboring neurons sum up to what is called
<b>local field potential (LFP)</b></p><h3>Dipoles</h3><p>EEG fields result from the superposition of many synchronously firing and
parallel-oriented neurons. Such bundles of active neurons can be approximated by a
dipole. A dipole is defined by&nbsp;<span>its location (the dipole position)</span>&nbsp;and a vector that represents the strength and orientation of the flow of electric current (the dipole orientation). EEG and MEG field result from the superposition of many synchronously firing and
parallel-oriented neurons (see image below). Such bundles of active neurons can be approximated by a
dipole.<img src="@@PLUGINFILE@@/Dipole%20Image.png" alt="Dipole Image" width="700" height="526" class="img-responsive atto_image_button_left"></p><p>The image below is of a dipole in the brain located in the dorsal anterior cingulate cortex, imaged in WinEEG. A dipole is most readily seen using a form of neuroimaging called "independent Component Analysis," an advanced technique used by individuals in the neuroscience community to help them locate the position of the spectrally-independent component, or pattern, of EEG activity. This modality is most useful for determining the location of a pattern.</p><p></p><p>When many clusters of neurons point in the same direction (as is the case with dipoles), we can see synchronous activity in the EEG.&nbsp;<b>Synchrony</b>&nbsp;is the simultaneous appearance of rhythmic or morphologically distinct patterns over different regions of the head, either on the same side (unilateral) or both sides (bilateral). Synchrony in the EEG allows one to see patterns and rhythms in the data.&nbsp;</p><p>A brain with poor synchrony is a low voltage EEG; there are many reasons why someone may have a low voltage EEG, including a thick skull and excess GABA A receptor sites. We often see low voltage EEGs in alcoholics.</p><br><p></p><p><img src="@@PLUGINFILE@@/Dipole%20in%20WinEEG%20%281%29.png" alt="Dipole" width="600" height="277" class="atto_image_button_text-bottom"><br></p><p><b>Low Voltage EEG</b></p><p><b><img src="@@PLUGINFILE@@/Low%20Voltage%20EEG.png" alt="Low Voltage EEG" width="500" height="1297" class="img-responsive atto_image_button_left"></b></p><h3>Resonances</h3><p></p><p>Brain waves resonate back and forth in resonant loops. Lubar (1997) divided this activity into three categories of local, regional, and global resonant loops (Lubar, 1997).</p><p><b>Local resonant loops&nbsp;</b>take place between local cell columns, known as macro columns.&nbsp;</p><p>&nbsp;The resonances between these local cell columns usually occur at frequencies above 30 Hz (high beta and gamma frequencies). Gamma is an emergent property of the brain and does not have a generator, unlike the other rhythms of delta, theta, alpha, or beta.&nbsp;</p><p>Resonances that develop between cortical cell columns that are several centimeters apart are called<b>&nbsp;regional resonances.</b>&nbsp;The exchange of communication between cortico-cortico sites would also dominate this range as well as corticothalamic sites. These resonances result in alpha and low beta activity. These involve the idling and engagement of cell columns as they process information incoming as a result of attentional activities and conscious articulation.</p>Global resonances develop as a result of activity between distant sites of the cortex and fall into the theta and delta range. Many of the sites involved in this frequency range are believed to include subcortical functions. Hippocampal-septal activity in the limbic system is known to generate a significant amount of theta activity. Kirk and McKay (2003) have identified two separate theta ranges.<p></p><p></p><p><span style="font-size: 1.715rem; color: rgb(55, 71, 79); font-family: &quot;Open Sans&quot;;"><br></span></p><p><span style="font-size: 1.715rem; color: rgb(55, 71, 79); font-family: &quot;Open Sans&quot;;">Major Gyri and Sulci of the Brain</span><br></p>
<p>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).
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<p style="text-align: center; "><img src="@@PLUGINFILE@@/Gyrus.png" alt="Gyrus" width="477" height="302" class="img-responsive atto_image_button_text-bottom"><br></p>
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<p style="text-align: center; "><img src="@@PLUGINFILE@@/sulcus.png" alt="sucus" width="499" height="183" class="img-responsive atto_image_button_middle"><br></p>
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<h3>&nbsp;See here a map of all the major gyri and sulci in the brain.</h3>
<p style="text-align: center; "><img src="@@PLUGINFILE@@/cortex.png" alt="cortex" width="700" height="488" class="img-responsive atto_image_button_middle"><br></p>
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<p>The Longitudinal fissure is the long sulcus that divides the left and right hemispheres of the brain. </p>

<h3><a name="_Toc28940397">Right hemisphere and Left
Hemisphere</a></h3>

<p>There are differences between the functionality of the right and the left hemispheres of the brain.&nbsp; The right hemisphere of the brain is unique in that it is <b><i>not</i></b> temporally associated (unlike the left hemisphere, which uses the precedent
    of the past to project into the future in anticipation). Whereas the left hemisphere is the side of our brain that speaks, read, writes, calculates, and takes care of numbers and facts (and some more specific responsibilities, such as making metaphors,
    lexical ability, self-reflection, self-appraisal, and inferences during reading), the right-hand side plays the role of assimilating all of this information. The right-hand side of the brain does not distinguish where I end and you begin, nay, it
    is an associational hemisphere that is more concerned with making meaning of all the component parts. It is the part of the brain that creates and draw similarity. It is the part of the brain that recognizes the connectivity of things, events, and
    people. allows for us to connect with others, to understand the connectivity of things, to comprehend situations and data in a sensory way, even in a psi-phenomenological way.</p>
<p>The Sulci that divides the hemispheres of the brain is called the Longitudinal Fissure</p>
<h3>Longitudinal Fissure that Divides the Hemispheres
</h3>
<p><img src="@@PLUGINFILE@@/Longitudinal%20Fissure.png" alt="Longitudinal Fissure" width="448" height="488" class="img-responsive atto_image_button_left"></p><p>The central sulcus (aka Rolandic Fissure) is the transverse sulci that separates the frontal lobes from the parietal lobes, as well as the sensory-motor strip into the motor cortex and the somatosensory cortex. </p>
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<h4><a name="_Toc28940399"><span>Central
Sulcus, aka Rolandic Fissure</span></a></h4>
<p></p><img src="@@PLUGINFILE@@/Rolandic%20Sulcus.png" alt="Rolandic Sulcus 1" width="199" height="127" class="img-responsive atto_image_button_text-bottom"><br>
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<p><img src="@@PLUGINFILE@@/rolandic%203.png" alt="rolandic 3" width="319" height="318" class="img-responsive atto_image_button_text-bottom"><br></p>
<h3>The Sylvian Fissure</h3>
<p style="text-align: center; "><img src="@@PLUGINFILE@@/Sylvian%20Fissure.png" alt="Sylvian Fissure" width="600" height="436" class="img-responsive atto_image_button_text-bottom"><br></p>
<p style="text-align: center; ">The sylvian fissure is the meeting of the temporal nd the frontal lobes of the brain, which opens up into a pocket of cortical tissue called the insula.</p><br>
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