Structure of the Cortex

1. 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.

2. 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.

3. 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.

4. 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.

5. 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.

6. Splitting the Brain • Fig. 6.11 (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. 6.12 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.

7. 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.