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Chapter 5 PSYC2410 Fall - Choleris

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University of Guelph
PSYC 2410
Elena Choleris

PSYC 2410 – Chapter 5 Research Methods of Biopsychology 5.1 Methods of Visualizing and Stimulating the Living Human Brain Looking at Structure:  Conventional X-rays: based on the fact that different structures absorb X-rays differently which shows up on film. It works when there is a high contract between the tissues being examined (ex: bones vs soft tissue). It’s not good for brain scans because the different tissues of the brain have similar X-ray absorption.  Contrast X-rays: A contrast dye is injected and is ‘photographed’, shows blood vessels usually. Eg. Angiography.  X-ray Computed Tomography (CT): A rotating X-ray tube takes multiple 2D images which are combined to create 3D images.  Magnetic Resonance Imaging (MRI): Radio frequency waves align hydrogen in water molecules which then emit a measurable magnetic signal; creates both 2D and 3D images and is clearer than CT. Looking at Function:  Positron Emission Tomography (PET): a radioactive compound is injected (2-deoxyglucose or 2-DG) which accumulates in active cells and degrades slowly. The radioactive signal of active cells is greater than that of non-active cells. PET scans can measure activation of brain areas. Can use certain radioactive tracers for specific systems.  Functional MRI (fMRI): Oxygen accumulates in active tissue, and oxygenated blood has magnetic properties. fMRI’s measure the BOLD (blood-oxygen-level-dependent) signal, essentially increases in oxygen flow to active areas.  Advantages of fMRI over PET: nothing is injected, structural and functional information is in one image, better spatial resolution, can create 3D images of activity over the entire brain.  Disadvantages: slow, takes time.  Magnetoencephalography (MEG): Measures changes in brain activity (changes in electric signal, in tiny magnetic fields in the scalp). When many (~50 000) neurons are active they generate measurable magnetic fields. This gives a higher temporal resolution than fMRI: MEG can record faster changes in neural activity; however, MEG has a lower spatial resolution than fMRI.  Transcranial Magnetic Stimulation (TMS): Use electrode to create magnetic fields to stimulate small cortical regions. It has observable behavioural effects. a single pulse causes a small effect, a repeated pulse (stimulation) creates lasting effects and can be used therapeutically. 5.2 Recording Human Psychophysiological Activity  Electroencephalography (EEG): Measures the average electrical activity of the head. Some EEG waves forms are associated with specific states of consciousness (sleep, wake, coma) and cerebral pathology (ex: epilepsy).  Most psychophysiologists are interested in event-related Potentials (ERPs): EEG waves that accompany certain psychological events. Ex: o Sensory Evoked Potential – change in EEG signal elicited by the momentary presentation of a sensory stimulus.  Signal Averaging: used to get rid of background ‘noise’  Distribution of EEG signals can be used to assess certain psychological conditions (ADD) Measures of Somatic Nervous System Activity  Electromyography (EMG): a measure of muscle tension as psychological arousal between two electrodes taped to the surface of the skin over the muscle of interest.  Electrooculography (EOG): measures changes in potential caused by eye movements. Based on the fact that there is a steady potential different between the front (positive) and back (negative) of the eyeball. Usually a measure of change in potential between one electrode on the right of the eye and one of the left, and between one above the eye and one below. Measure of Autonomic Nervous System Activity  Electrodermal Activity: sweat glands are involved in changes in conductance PSYC 2410 – Chapter 5  Skin Conductance Level (SCL): a measure of the background level of skin conductance associated with a particular situation  Skin Conductance Response (SCR): measure of the transient changes in skin conductance that are associated with discrete experiences.  Cardiovascular Activity:  Electrocardiography (ECG, EKG): measures electrical signal associated with each heartbeat and is recorded through electrodes placed on the chest, normal is ~70 beats/minute  Arterial Blood Pressure: ~130/70 mmHG, measures systolic (contraction) over diastolic (relaxation). Uses sphygmomanometer.  Blood Volume measured by Plethysmography: measures changes in blood volume in specific parts of the body. Methods include tying a strain gauge around a body part, shining light through tissue to measure the amount of light that is absorbed; the more blood, the more light absorbed. 5.3 Invasive Physiological Research Methods brains don’t have pain sensors  Stereotaxic Surgery: used to position experimental devices within the brain using a Stereotaxic Atlas with coordinates of different structures/parts of brains.  Bregma is a commonly used reference point for stereotaxic surgery on the skull.  Stereotaxic instruments are used to guide the device to be inserted and hold the head steady; it operates in three directions: Anterior-Posterior, Dorsal-Ventral, Medial-Lateral.  Can be used to: o Implant electrodes for Lesions, Recording, Stimulation o Inject Chemicals for Lesions, Pharmacological Effects, Tracing o Implant Cannulae for later Treatment delivery, Sample collection o Implant Capsules/Minipumps for continuous treatment delivery o Implant Optic Fibers for light stimulation (Optogenetics) Mainly limited to Animal Research:  Lesion Methods: used to remove, damage, or destroy a part of the brain (unilateral or bilateral).  Chemical lesions: o Neurotoxins (kainic acid, ibotenic acid) o Neurotransmitter-Specific Inhibitors (dopamine) o Anesthetics (lidocaine) which are temporary o Radio-Frequency/Electrical Lesions: Heat o Knife Cuts: cutting of tracts o Cryogenic blockade: reversible/temporary (freeze region/area with probe).  Electrophysiological Methods: Uses bipolar electrodes for lesions (strong electrical currents), recording (brain activity in relation to behaviour), stimulation (weak electrical currents activate brain areas, leads to behaviour?  In Vitro (isolated artificial) ex: measuring action potentials of squid axons in the lab with oscilloscope; Patch Clamping by placing a glass micropipette against cell to record action potentials, o Cell-attached recording sometimes only one ion channel o Whole-cell recording by rupturing the membrane patch when using a small cell. o Outside-out patch by collapse a cytoplasmic bridge and having some cell membrane come with. o Inside-out patch by breaking cytoplasmic bridge and exposing the outside membrane to air which breaks the cell patch.  In Vivo (direct links to behaviour) o Intracellular Unit Recording: measuring the membrane potential of a neuron o Extracellular Unit Recording: measuring the firing of a neuron o Multiple-Unit Recording: measuring the firing of many neurons PSYC 2410 – Chapter 5 o Invasive EEG Recording: in lab animals, EEG signals recorded through large implanted electrodes rather than through scalp electrodes. Cortical EEG signals are recorded through stainless steel skull screws, subcortical EEG signals recorded through stereotaxically implanted wire electrodes. 5.4 Pharmacological Methods  Routes of Drug Administration  Routes of Systemic or Localized Drug Administration o Oral (through oral cavity, drink, eat) o Intragastric (tube into the stomach) o Transdermic: patches on the skin o Injections/Cannulae (thin hollow tube)/Capsules/Minipumps: delivery of drugs through cannula that has been stereotaxically implanted in the brain.  Intraperitoneal: injected hypodermically into the peritoneal cavity of the abdomen  Intramuscular: into a large muscle  Subcutaneous : into the fatty tissue beneath the skin  Intravenous: into a large surface vein  Intracerebral: intraventricular, intraparenchymal  Selective Chemical Lesions:  Neurotoxins are more precise in creating lesions, inject neurotoxin that has an affinity for certain components of the NS. Ex: 6-OHDA, only taken up by neurons that release norepinephrine or dopamine  Measuring chemical Activity in the Brain:  2-Deoxyglucose (2DG): inject the radioactive 2DG, then place the animal in a test situation where it engages in the behaviour of interest. Then, the subject is killed, and the brain sliced and subjected to autoradiography (developed like film). Areas of high absorption appear black.  Cerebral Dialysis/Microdialysis: method of measuring the extracellular concentration of specific neurochemicals in behaving animals. A fine tube is implanted in the brain with a short semipermeable section positioned in the brain structure of interest so that extracellular chemicals diffuse into the tube.  Locating Neurotransmitters and Receptors:  Dye or Radioactive Labels (ex: autoradiograph): green-fluorescent protein, brainbow mice (p.119)  Immunocytochemistry: based on the binding of labeled protein-specific antibodies. Antibodies = Immune Response – they bind antigens (foreign proteins) for removal/disruption.  In Situ Hybridization: uses labeled RNA to locate neurons with complementary mRNA 5.5 Genetic Engineering  Gene Knockout Techniques: used to create organisms that lack a particular gene under investigation.  Gene Replacement Techniques: genes from one species can be inserted into another. Ex: inject mice with pathological genes from human cells (transgenic mice). In another technique, bases can be attached to certain genes which allow them to be turned on and off using certain chemicals, so that researchers can control its expression.  Fantastic Fluorescence and the Brainbow: GFP gene is activated in particular cells so that they can readily be visualized. Either by inserted GFP only in target cells or by introducing the GFP gene in all cells but expressing the gene in only the target cells. Mutated genes for cyan, yellow and blue fluorescent proteins were also introduced into the genomes of developing mice. Each neuron produced different amounts of the three proteins, giving it a distinctive color. Thus the pathways of neural axons could be traced to their destinations through the cellular morass, “Brainbow”. 5.6 Behavioural Research Methods Neuropsychological Testing:  time-consuming (only conducted on a small portion of those with brain damage) PSYC 2410 – Chapter 5  assists in diagnosing neural disorders, especially in cases where brain imaging, EEG and neurological testing have proved ambiguous.  serves as a basis for counseling/caring  provides information on effectiveness and side effects of treatment Approaches to Neuropsychological Testing:  Single-Test (50s): goal of these tests was to discriminate between structural (brain damage) vs. functional (psychological) causes. However they proved unsuccessful because no single test could be developed that would be sensitive to all the varied and complex psychological symptoms that could potentially occur in a brain-damaged patient.  Standardized-test-battery (60s): goal still to identify brain-damaged patients vs. normal patients. Good to discriminate between neurological and healthy patients but not between neurological patients and psychiatric patients.  Halstead-Reitan Neuropsychological test battery: set of tests that tend to be performed poorly by brain-damaged patients  Customized-test-battery (60s): predominates in both research laboratory and the neurological ward.  common test battery  personalized tests. Characterizes nature of psychological deficits, not just indication of brain-damage. Given standard tests, then based on those results, neuropsychologist selects a series of tests customized to each patient in an effort to characterize in more detail the general symptoms revealed by the common battery tests.  Differ from previous tests… 1. Specifically designed to measure aspects of psychological function spotlighted by modern theories and data. 2. Interpretation of the results often doesn’t rest entirely on how well the patient does. Often require the neuropsychologist to assess the cognitive strategy used in the tests. Brain-damage often changes the strategy, without lowering the overall score. 3. The customized-test-battery requires more skill and knowledge on the part of the neuropsychologist to select just the right battery of tests to expose a patient’s deficits and to identify qualitative differences in cognitive strategy. Initial Common Test Battery  Wechsler Adult Intelligence Scale (WAIS) – IQ: verbal and performance, knowing someone’s IQ can help a neuropsychologist interpret the results of other tests Wechsler Adult Intelligence Scale (WAIS I) 6 Verbal Subjects Information: Read to the subject are 29 questions of general information. Digit Span: 3 digits are read to the subject at 1-sec intervals; Subject is asked to repeat them in the same order. Two trials are given at three digits, four digits, five digits, and so on until the subject fails both trials at one level. Vocabulary: the subject is asked to define a list of 35 words that range in difficulty. Arithmetic: the subject is presented with 14 arithmetic questions and must answer them without the benefit of pencil and paper Comprehension: the subject is asked 16 questions that test the ability to understand general principles (why should peopl
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