Structure of the Cortex Newer neural networks within the cerebrum form specialized areas that enable us to perceive, think, and speak. Some of these areas are only 50,000 years old; that is practically brand new in terms of evolution. This brain area requires a lot of fuel (glucose, or blood- sugar), and myeline sheathing. This is supplied by the glial cells. They support, nourish, and protect neurons, and play a role in learning and thinking. For example, glial cell death has been linked to clinical depression. They also guide neural connections, and mop up excess ions. The more complex the brain, the more glial cells.

The Cerebral Cortex Fig. 6.1(mp70, c2.23p70): the cortex and its basic subdivisions. Fig. 6.2(mp71,c2.24p71) The amount of cortex devoted to a body part is not proportional to the part's size. Rather, the brain devotes more tissue to sensitive areas and to areas required precise control. Input comes through and from the sensory cortex; output through and from the motor cortex. Gibbs (1996) (mp70,cp70) was able to predict a monkey's arm motion a tenth of a second before it moved--by repeatedly measuring motor cortex activity preceding specific arm movements. This has lead to brain-controlled computers.

Brain-Computer Interaction Fig. 6.4 (mp72,c2.26p72): A patient with a severed spinal cord has electrodes planted in a parietal lobe region involved with the planning to reach one's arm. The resulting signal can enable the patient to move a robotic limb, stimulate muscles that activate a paralyzed limb, navigate a wheelchair, and use the internet. This is only the beginning! Fig. 6.6 (mp73,c2.28p73): visual & auditory cortex. Visual cortex = Occipital lobe. Most neuroscience breakthroughs began with vision research.

Association Areas Three quarters of the cortex is devoted to association areas. Electrical probing won't yield an observable response. That has led to the misguided claim that we ordinarily used only 10% of our brains (Beeson, 2014, 'Lucy'). Surgically lesioned animals and brain-damaged humans bear witness that association areas are not dormant. Fig. 6.8 (mp74,c2.30p74): The Strange Case of Phineas Gage Parietal association areas enable mathematical and spatial reasoning. The underside of the right temporal lobe enables us to recognize faces, and subtle facial expressions.

Plasticity Our brains are sculpted not only by our genes, but by our experiences. Severed neurons usually do not regenerate. Some brain functions seem preassigned to specific areas. One newborn who suffered damage to temporal lobe facial recognition areas later remained unable to recognize faces. Some neural tissue can reorganize in response to damage. Constraint-induced therapy aims to rewire brains and improved the dexterity of a brain-damaged child. Damaged brain functions can migrate to other regions.

Splitting the Brain Fig (mp77, c2.33p77) Look out! There is a left and right visual field in each eye. Sperry and Gazzaniga (1967) worked with patients who had a severed corpus callosum, the massive network of nerve fibres that link the two hemispheres (significantly thicking in females). The trick with Fig mp78, c2.34p78) is to remember that the stimulus is flashed to the subject. This means a duration of no more than 1/2 second. The left hemisphere did the talking, becoming increasingly bewildered by what the non-verbal right hemisphere knew.

Right-Left Intact Brain Language is language; spoken or signed. Deaf people use the left hemisphere to process sign language. LH = quick, literal interpretations. RH excels in making inferences. RH helps to modulate speech to increase clarity of meaning. RH helps to orchestrate our sense of self. Remember this 'sense of self' for Web Article Two.