The Brain The cerebral cortex The cerebral cortex

The Brain The cerebral cortex

The cerebral cortex � The newer neural networks are located in the cerebrum. The cerebrum is the two large hemispheres of the brain and is covered by the cerebral cortex. � The cerebral cortex is a thin layer of neural cells that are interconnected. This cortex covers the hemispheres and is the body’s supreme thinking, control and information processing center.

The cortex � The cortex contains approximately 20 billion neural cells and about 300 trillion synaptic connections. These neural cells are supported by glial cells. About nine times as many glial cells as neural cells. The glial cells are responsible for providing nutrients, the process of myelination and they guide neural activity/connections. They also mop up ions and neurotransmitters.

The hemispheres � The two hemispheres are divided into lobes. There are two of each lobe because the brain is lateralized. The lobes are divided from each other by fissures and folds. � Fissures: Gyri (Gyrus: singular) are the grooves in the brain � Folds: Sulci (Sulcus: singular) are the humps between the grooves

The lobes The frontal lobes are located behind your forehead. � The parietal lobes are located at the top and to the rear. � The occipital lobes are located at the back of your head. � The temporal lobes are located above your ears. � The lobes each carry out several functions, and also interact to carry out certain functions. �

Functions of the Cortex Motor Cortex In 1870, the motor cortex was discovered by two researchers, while experimenting on a dog. By applying electrical stimulation to the dog’s cortex, they discovered that they could cause movement. � It only occurred in a small strip that runs from ear to ear at the back of the frontal lobe. They also discovered that stimulation to one side of the cortex caused movement on the opposite side of the body. � �

Motor cortex mapping The brain has no sensory receptors, allowing researchers to map the motor cortex in wide awake patients, using electrical stimulation. � Foerster and Penfield discovered that the body areas that require precise control (think fine motor skills) occupied the largest amount of cortical space. � In 1996, Gibbs discovered that we can predict a monkey’s arm motion a tenth of a second before he moves it. This has led scientists toward a new field of prosthetics. �

Neural Prosthetics � In 2002, researchers at Brown University implanted 100 recording electrodes in the brains of three monkeys. They had the monkeys complete a task for reward. They then matched the brain signals to the arm movements and programmed a computer to operate a joystick from the task without the monkey’s physical help. The monkey could then think about the move and the computer could complete the move.

� In 2004, researchers pinpointed the planning and intention area of the brain and recorded signals from this area also. They could now program a computer to fully follow the thought of the monkey. � In 2008, a follow up experiment was performed where the monkeys learned to operate a prosthetic arm to feed them a reward, through thought only.

Human use In 2004, the FDA approved clinical trials of neural prosthetics for humans. The first patient gained the ability to control a TV, play video games and draw on a computer screen from a small chip with 100 microelectrodes recording activity in his motor cortex. � Scientists are now researching the ability to use this same basic technology to address speech issues after a stroke, for example. �

Sensory Cortex The sensory cortex is the part of the brain receiving sensory messages from the skin senses and body movement. This area is located parallel to and behind the motor cortex, at the front of the parietal lobes. � Stimulation of the sensory cortex can cause people to report being touched, when there has been no actual touch. � The more sensitive the area, the larger the sensory cortex area devoted to it. �

Other senses � Visual sensations are received in the visual cortex which is located in the occipital lobes. � Auditory sensations are received in the auditory cortex located in your temporal lobes

Association areas � � � Neurons in the association areas integrate information. They link sensory inputs with stored memories. Association areas are hard to map because they do not trigger observable responses. They are found in all four lobes of the brain. In the frontal lobes they enable judgment, planning and processing of new memories. In the parietal lobes, they enable mathematical and spatial reasoning. In the right temporal lobe is an area that enables us to recognize faces. Once again, the brain is complex and interwoven, association areas do not singularly control these actions/processes by themselves.