Chapter 5 slides

Copyright © 2006 by Allyn and Bacon

Methods of Visualizing the Living Human 

Brain ‐ Structure 

• Contrast X‐Rays –Abeam of x‐rays is passed through body onto a 

photographic plate. A contrast medium absorbs X‐rays less or more 

than surrounding tissue and can be injected into an area of interest. 

• Eg E.g., cerebral angiography 

• X‐Ray Computed Tomography (CT) 

• 2‐D images combined to create a 3‐D one 

*X‐rays can be used for visualizing vasculature, and hence for 

assessing stroke location and extensiveness, but are not useful for 

examining brain tissue.* 

• Magnetic Resonance Imaging (MRI) 

• Measures waves emitted by hydrogen atoms when they are activated 

by radio waves while in a magnetic field. The waves the atoms give 

off differ in frequency depending on the material of which they are 

a part (e.g., fat vs. water). 

• Produces 3‐D images with high spatial resolution 


Cerebral Angiography

3‐D movie of Cerebral Angiography 

• http://www.med.harvard.edu/AANLIB/cases/case17/ 

mra.mpg

CT Scan

MRI Scan

Methods of Visualizing the Living Human 

Brain ‐ Functional 

• Positron Emission Tomography (PET) 

• Inject radioactive 2‐DG. This form of glucose is taken up by active 

cells and accumulates. Radioactivity is mapped to reveal activity. 

• Functional MRI (fMRI) 

• MRI technology that focuses on oxygen flow in the brain. Can 

provide info on both activity and structure. 

• Magnetoencephalography (MEG) 

• Measures changes in magnetic fields on scalp produced by 

underlying brain activity. It can record fast changes in activity over 

time (temporal resolution). 


PET Scans 

20 yr old brain 80 yr old brain

Functional MRI (fMRI)

Magnetoencephalography (MEG)

fMRI Vs PET 

• Nothing injected. 

• Provides both structural and functional 

information in one image 

• Spatial resolution is better than with PET (Note 

that MEG has better temporal resolution) 

• Can create 3‐D images of activity over the 

entire brain 


Recording Human Psychophysiological 

Activity 

• Recording physiological activity from the body 

surface 

• Electroencephalogram (EEG) 

• Muscle tension and eye movement 

• Skin conductance and cardiovascular activity 


EEG –measuring “brain waves” 

• A measure of the average electrical activity of the 

brain. 

• Some EEG wave forms associated with: 

• Specific states of consciousness 

• Cerebral pathology gy( (such as epilepsy) 

p • Event‐related potentials may also be of interest 

• EEG measured while the person engages in a 

particular activity (event) 

• For an example of how these are used, go to Ch 

.5 on the textbook cd and select “Visit to a 

cognitive neuroscience lab” 




Measures of Somatic Nervous System 

Activity 

• Electromyography – muscle tension 

• Resulting electromyogram (EMG) can be used as a 

measure of psychological arousal 

• Electrooculography – eye movement 

• Electrooculogram (EOG) 



• Figure 5.13 


Measures of Autonomic Nervous System 

Activity 

• Electrodermal – appears to reflect activity of 

sweat glands 

• Skin conductance level (SCL) ‐ background 

• Skin conductance response (SCR) –measures 

transient t changes 

• Cardiovascular – blood vessels and heart 

• Heart rate 

• Blood pressure 

• Blood volume 


Measures of Autonomic Nervous System 

Activity ‐ Cardiovascular 

• Heart rate 

• Electrocardiogram (ECG, EKG) records electrical 

signals associated with heartbeats 

• Blood pressure 

• Measured with a sphygmomanometer 

• Blood volume 

• Plethysmography refers to techniques for measuring 

changes in blood volume in a particular body part 


Polygraph Device: 

Heart rate, blood pressure, respiration, 

galvanic skin response

Invasive Physiological Research Methods 

• Animal research 

• Lesioning 

• Electrical stimulation 

• Invasive recording methods 

• Manipulating or measuring within the brain 


Stereotaxic Surgery 

• Used to position experimental devices within 

the brain 

• Stereotaxic atlas –provides coordinates for 

locating structures within the brain 

• Bregma – a point on the top of the skull often 

used as a reference point 

• Sterotaxic instrument –used to hold head 

steady and guide the device to be inserted 



Lesion Methods 

• Remove, damage, or destroy a part of the brain 

to observe impact on behavior 

• Aspiration lesions –suction ‐ cortex 

• Radio‐frequency lesions – heat destroys tissue 

• Knife cuts – may damage surrounding area 

• Cryogenic blockade – “reversible lesion” 




Electrical Stimulation 

• Lesioning can be used to remove, damage, or 

inactivate a structure. 

• Electrical ca stimulation may be used to “activate” a 

structure. 

• Stimulation of a structure may have an effect opposite 

to that seen when the structure is lesioned. 


Invasive Electrophysiological Recording 

Methods 

• Intracellular unit recording 

• Membrane epotential t of a neuron 

• Extracellular unit recording 

• Firing of a neuron 

• Multiple‐unit recording 

• Firing of many neurons 

• Invasive EEG recording – electrodes are implanted in 

skull or tissue. 



Pharmacological Research Methods 

• Routes of drug administration 

• Selective chemical lesions 

• Measuring chemical activity in the brain 

• Locating neurotransmitters and receptors 


Routes of Drug Administration 

• Fed to the stomach 

• Injected ‐ described by injection sight: 

• stomach (intragastric) 

• peritoneal cavity (intraperitoneal, i IP) 

• large muscle (intramuscular, IM) 

• tissue under the skin (subcutaneous, sc) 

• large surface vein (intravenous, IV) 

• Cannula – used to administer drug directly to brain 


Selective Chemical Lesions 

• Neural poisons (neurotoxins) selectively 

target specific nervous system components 

• Kainic or ibotenic acid – destroy cell bodies 

• 6‐hydroxydopamine (6‐OHDA) – destroys 

noradrenergic and dopaminergicneurons 

i 


Measuring Chemical Activity of the Brain 

• 2‐Deoxyglucose (2‐DG) technique 

• Inject animal with radioactive 2‐DG and allow it 

to engage in behavior of interest 

• Use autoradiography to see where radioactivity 

accumulates in brain slices 

• Cerebral dialysis – measures extracellular 

concentration of specific chemicals in live 

animals 


Locating Neurotransmitters and Receptors 

• Dye or radioactive labels used to visualize the 

protein of interest 

• Immunocytochemistry y–based on the binding of 

labeled protein‐specific antibodies 

• Immune response ‐ Antibodies created that bind and 

remove/destroy antigens (foreign proteins) 

• In situ hybridization –uses labeled RNA to locate 

neurons with complementary mRNA 


Genetic Engineering 

• Gene knockout techniques 

• Subjects missing a given gene can provide insight 

into what the gene controls 

• Difficult to interpret results – most behavior is 

controlled by many genes and removing one gene 

may alter the expression of others 

• Gene replacement techniques 

• Both are currently being intensely studied 


Neuropsychological Testing 

• Time‐consuming ‐ only conducted on a small 

portion of those with brain damage 

• Assists in diagnosing neural disorders. 

• Serves as a basis for counseling/caring 

• Provides information on baseline function 


Approaches to Neuropsychological Testing 

• Single‐test – Early approach 

• Used to differentiate brain damage from functional 

(psychological) causes 

• Standardized‐test‐battery 

test • Same goal as single‐test approach 

• Customized‐test‐battery 

• attempts to characterize (describe) the psychological deficits 

of a person, rather than just detect whether or not there is 

brain damage. 


Customized‐Test‐Battery Approach 

• Began to be used in the 1960’s 

• Goal is to characterize the nature of the deficits seen in 

the eba brain‐damaged aged patient 

t 

• Begin with a general test and then follow with tests 

designed to explore the nature of the observed 

problems 


Potential Components of the Initial 

Common Test Battery 

• Wechsler Adult Intelligence Scale 

• WAIS, an IQ test 

• Often fails to detect memory deficits 

• Token test 

• Can detect language‐related deficits 

• Language g lateralization –used to identify language‐ 

g 

dominant hemisphere 

• Sodium amytal – anesthetize one hemisphere 

• Dichotic listening –ear contralateral to dominant hemisphere 

shows s superior hearing ability 


Specific Neuropsychological Tests 

• Memory –exploring nature of deficits 

• Short‐term, long‐term, or both? 

• Anterograde or retrograde? 

• Semantic or episodic? 

• Explicit or implicit? 

• Language –problems of phonology, syntax, or 

semantics? 

• Frontal‐lobe function – often assessed with the 

Wisconsin Card Sorting Test 

• Can the subject alter strategy as needed? dd? 


WCST 

• Wisconsin 

• Card 

• Sorting 

• Task 


Cognitive neuroscience – assumptions 

• Each complex cognitive process results from the 

combined activity of simple cognitive processes 

(constituent cognitive processes) 

• Each complex cognitive process is mediated by neural 

activity in a particular area of the brain 


Cognitive Neuroscience 

• Goal is to identify the parts of the brain that mediate 

various constituent cognitive ii processes 

• Pi Paired‐image di subtraction technique –compare PET or 

fMRI images during several different cognitive tasks 


Behavioral Paradigms 

• Procedures developed for the investigation of a 

particular behavioral phenomenon 

• Assessment of species‐common common behaviors 

• Traditional conditioning paradigms 

• Seminatural animal learning paradigms 


Assessment of Species‐Common Behaviors 

• Assessment of behaviors displayed by all members 

of a species 

• Open‐field test – general activity 

• Colony‐intruder paradigm – aggression and 

defensive behavior 

• Elevated plus maze –anxiety 

• Tests of sexual behavior 


Open Field

Elevated Plus Maze

Traditional Conditioning Paradigms 

• Pavlovian conditioning 

• Pairing an unconditioned stimulus with a 

conditioned stimulus 

• Pavlov’s dogs 

• Operant conditioning 

• Reinforcement and punishment 

• Self‐stimulation 

• Animal works for electrical stimulation 


Seminatural Learning Paradigms 

Mimic situations that an animal might encounter in 

its natural environment 

• Conditioned taste aversion 

• Pairing something that makes an animal ill (emetic) with a 

taste 

• Challenged existing assumptions about conditioning 

• Animals appear prepared to associate tastes and illness 

• Radial arm maze –tests spatial abilities 


Radial Arm Maze

Seminatural Learning Paradigms 

• Morris water maze – tests spatial abilities 

• Rat must find hidden platform in an opaque pool 

• Conditioned defensive burying – following a 

single aversive stimulus delivered from an 

object, rats will spray bedding at the object 

• Antianxiety drugs decrease the amount of burying 

behavior 


Morris Water Maze

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