5 Steps to a 5 AP Psychology, 2010-2011 Edition - Laura Lincoln Maitland [38]
Direct electrical stimulation of different cortical areas of the brain during surgery enabled scientists to observe the results. Stimulating the back of the frontal cortex at particular sites caused body movement for different body parts enabling mapping of the motor cortex.
In recent years, neuroscientists have been able to look inside the brain without surgery. Computerized axial tomography (CAT or CT) creates a computerized image using x-rays passed through various angles of the brain showing two-dimensional “slices” that can be arranged to show the extent of a lesion. In magnetic resonance imaging (MRI), a magnetic field and pulses of radio waves cause emission of faint radio frequency signals that depend upon the density of the tissue. The computer constructs images based on varying signals that are more detailed than CT scans. Both CT scans and MRIs show the structure of the brain, but don’t show the brain functioning.
Measuring Brain Function
Scientists have developed a number of tools to measure the brain functions of people. An EEG (electroencephalogram) is an amplified tracing of brain activity produced when electrodes positioned over the scalp transmit signals about the brain’s electrical activity (“brain waves”) to an electroencephalograph machine. The amplified tracings are called evoked potentials when the recorded change in voltage results from a response to a specific stimulus presented to the subject. EEGs have been used to study the brain during states of arousal such as sleeping and dreaming, to detect abnormalities (such as deafness and visual disorders in infants), and to study cognition. Another technology, positron emission tomography (PET) produces color computer graphics that depend on the amount of metabolic activity in the imaged brain region. When neurons are active, an automatic increase in blood flow to the active region of the brain brings more oxygen and glucose necessary for respiration. Blood flow changes are used to create brain images when tracers (such as radioactively tagged glucose) injected into the blood of the subject emit particles called positrons, which are converted into signals detected by the PET scanner. Functional MRI (fMRI) shows the brain at work at higher resolution than the PET scanner. Changes in oxygen in the blood of an active brain area alters its magnetic qualities, which is recorded by the fMRI scanner. After further computer processing, a detailed picture of that local brain activity emerges. With new brain imaging technology, psychologists can explore far more about our abilities than ever before, from well-known systems like perception to less understood systems like motivation and emotion.
Organization of Your Nervous System
Your patterns of behavior generally involve masses of neural tissue rather than a few neurons. All of the neurons in your body are organized into your nervous system. Your nervous system has subdivisions based on location and function. The two major subdivisions are your central nervous system and your peripheral nervous system. Your central nervous system consists of your brain and your spinal cord. Your peripheral nervous system includes two major subdivisions: your somatic nervous system and your autonomic nervous system. Your peripheral nervous system lies outside the midline portion of your nervous system carrying sensory information to and motor information away from your central nervous system via spinal and cranial nerves. Your