Chapter 5 The Research Methods of Biopsychology Understanding what biopsychologists do 1 Methods of visualizing and stimulating the living human brain a X rays are useless for studying the brain only categorize internal structures the differ substantially from surroundings in terms of density b Contrast x ray techniques involves injecting one compartment of the body with a substance that absorbs x rays less more than the surrounding tissue i Cerebral angiography uses infusion of radiopaque dye into cerebral artery to visualize the cerebral circulatory system during x ray photography 1 useful for localizing vascular damage or finding displacement of blood vessels from their normal position to indicate the location of the tumor c Computed tomography CT is a computer assisted x ray procedure that can visualize the brain internal structures of the living body taking individual x ray photographs to produce horizontal scan sections of the brain i Scans of eight or nine horizontal brain sections are typically obtained and when combined provide a three dimensional representation of the brain d Magnetic resonance imaging MRI is A procedure in which high resolution images are constructed from the measurement of waves that hydrogen atoms emit when activated by radiofrequency waves in a magnetic field i Gives clearer images of the brain than does a CT scan ii In addition to providing high spatial resolution ability to detect and their presents differences and spatial location MRI can produce images in three dimensions e Positron emission tomography PET scans provider images of brain activity Functional brain images rather than images of brain structure structural great images i Common version has the radioactive 2 deoxy glucose injected into patient s carotid artery And because it is similar to glucose this chemical is a rapidly taken up by axis energy consuming cells but since it cannot be metabolized it accumulates in active neurons or associated astrocyte ii Allows indication of the areas of the brain that are active when the patient is doing something iii Not really image of brain but collard map of the amount of radio activity in each of the tiny cubic voxels pixels that compose the scam iv Most recently PET scans used to identify distribution in brain of molecules of interest but injecting volunteers with radioactively labeled ligands ions molecules that binds to other molecules under mastication f Functional MRI fMRI produces images representing the increase and oxygen flow in the bloods to active areas of the brain which take up more oxygenated blood as a need in their energy expenditure oxygen in blood accumulates in active areas of the brain i Oxygenated blood has magnetic properties that influence the radiofrequency waves amended by hydrogen atoms in the MRI Signal recorded is BOLD signal blood oxygen level dependent signal and not actually neural activity ii Has four advantages 1 Nothing has to be injected into the volunteer 2 Provides both structural and functional information in the same image 3 Spatial resolution is better 4 Can be used to produce three dimensional images of activity over the entire brain iii Disadvantage of having poor temporal resolution poor at specifying timing of neural events as takes 2 to 3 seconds to create image while many neural responses occur in milliseconds g Diffusion tensor imaging is a method of identifying those pathways along which water molecules rapidly diffuse because tracts bundles of axons are the major routes of rapid water to fusion in the brain i Helps understand connections among the structures of the brain h Transcranial magnetic stimulation TMS is a way of turning off areas of the cortex by creating and magnetic field under a coil positioned next to the skull allowing the effects of the disruption on cognition and behavior to be assessed 2 Recording human psychophysiological activity methods of recording physiological activity from the surface of the human body a Scalp electroencephalography EEG is the measure of the gross electrical activity of the brain Recorded through large electrodes by device with electrode taped to the scalp i EEG signal reflects the sum of electrical event struck the head Including action potentials of postsynaptic potential s as well as electrical signals from the skin muscles blood and eyes ii Some forms of EEG waves are associated with particular states of consciousness so often used in sleep studies or studies about epilepsy 1 Alpha waves are regular H2 12 per second high amplitude waves associated with relaxed wakefulness iii Events related potential ERPs are EEG waves that accompany certain psychological events such as the sensory evoked potential the change in the cortical EEG signal elicited by the momentary presentation of the sensory stimulus 1 Recorded EEG has two components as the response to stimulus and ongoing background EEG activity so signal averaging is used to reduce the noise of the background in order to better pick out the stimulus 2 P300 wave Is a positive way that occurs about 300 ms after a momentary stimulus that has meaning for the subject is shown a Portions of invoked potential record in the first few milliseconds after a stimulus are not influenced by the meaning of the stimulus and are called far field potentials because they originate far away in the sensory nuclei of the brainstem b Magneto encephalography MEG measures changes and midnight fields on the surface of the scalp produced by underlying patterns neural activity c Muscle tension can be recorded as at any given time as a few fibers in each muscle are maintaining overall tone tension and electromyography can be used to measure overall muscle tension as an indicator of psychological arousal i Resulting record is called electromyogram EMG and usually recorded between two electrodes taped to the surface of the skin over the muscle interest d Eye movement is recorded by electro oculography EOG and is based on the fact that study potential difference exists between the front positive and back negative portions of the eyeball i When eye moves changes and electrical potential between two electrodes placed on the eye can be recorded e Skin conductance level SCL and skin conductance response SCR are two ways to measure electrodermal activity from the cases when sweat glands become active in emotional situations f Cardiovascular activity can be measured in three different ways i heart rate by an electrocardiogram ECG EKG