Pinel 4e Lecture 5a
METHODS OF STUDYING THE NERVOUS SYSTEM

Outline
1.     Methods of Visualizing the Living Human Brain
     a     .Contrast X-rays
     b.     Computerized Axial Tomography
     c.     Magnetic Resonance Imaging
     d.     Positron Emission Tomography
     e.     Functional MRI
2.     Recording Psychophysiological Signals
     a.     Scalp Electroencephalography
     b.     Measures of Somatic Nervous System Activity
     c.     Autonomic Nervous System Activity
3.     Invasive Physiological and Pharmacological Methods
     a.     Stereotaxic Surgery
     b.     Lesion Methods
     c.     Electrical Stimulation
     d.     Electrical Recording Methods
     e.     Psychopharmacological Methods
4.     Genetic Engineering
     a.     Knockouts
     b.     Gene replacement

Lecture Notes

1.     Methods of Visualizing the Living Human Brain

- methods in this section explain how the nervous systems of living humans and animals      can be studied

a.     Contrast X-rays:

-     to take an X-ray photograph of an object, a beam of X-rays is passed through it onto a photographic plate; any part of the object that absorbs X-rays differently than does the surrounding medium will be distinguishable

-     standard X-rays are of no use for studying the brain because the brain is composed of many overlapping structures that all absorb X-rays to about the same degree

-     the contrast X-ray is a method of solving this problem that can be used in some cases;
     a radioopaque material is introduced into the structure of interest to make it stand out from the others on an X-ray photograph;
     for example, in pneumoencephalography air is worked into the ventricles after its injection into the spinal cerebrospinal fluid (it reveals enlarged or displaced ventricles),
     and in angiography radio-opaque dye is injected into the carotid artery (it reveals displacement or enlargement of blood vessels)

b.     Computerized Tomography (CT)

-     provides a 3-dimensional view of a structure;
     brain CT scans are usually composed of 8 or 9 horizontal sections

-     the X-ray gun and the X-ray detector rotate in apposition around the brain at one level taking a series of measurements from which an image of one section is constructed; this is repeated at 8 or 9 different levels

-     the CT-scan image of the brain is not sharp and is used to visualize large tumors.

c.  Magnetic Resonance Imaging (MRI)

-     it has higher powers of resolution than CT because X-rays aren't used

               the images are created from measurements of the waves emitted by hydrogen atoms when they are placed in a magnetic field;

     its clarity stems from the fact that neural structures differ considerably in their density of hydrogen atoms

d.     Positron Emission Tomography (PET)

-     PET is a method of highlighting brain areas that are active, rather than equally showing all brain structures
the patient is injected with radio-active 2-deoxyglucose;
          because 2-DG is structurally similar to glucose, it is taken up by neurons as if it were glucose;
          more active neurons need more energy and take up more 2-DG;
          but unlike glucose, 2-DG cannot be metabolized by neurons and it accumulates in them

-     after injection with radio-active 2-DG the subject engages in the activity under study (e.g., reading) while a PET scan of the brain is being taken;
     the PET scan reveals on a series of images of horizontal sections where radio activity has accumulated, and thus it indicates what areas were particularly active during the test


e.     Functional MRI
          allows brain activity to be measured via images of the increase in oxygen (blood) flow to the areas that are active
-     it has four advantages over PET which include
                    (1) nothing must be injected into the subject,
                    (2) one image provides both structural and functional ion formation,
                    (3) the spatial resolution is better, and
                    (4) changes can be measured in real time

2.  Recording Psychophysiological Signals
     (Recall that psycholphysiological measures are taken from the surface of the body)

Scalp Electroencephalogaphy (EEG): (use Digital Image Archive Figure CH05F07.BMP)


A human EEG signal is the difference in the electrical potential between two large scalp electrodes as a function of time;

in laboratory species, EEG activity is usually recorded through electrodes implanted in cortical or subcortical tissue (inside the cranium)

EEG waves reflect the sum total of all of the electrical events in the head
     (APs, EPSPs, IPSPs, eye movements, blood flow, etc.);

thus the EEG reveals little about the nature of the underlying neural activity

its value lies in the fact that particular EEG wave forms are associated with particular states of consciousness;
     generally low-amplitude, fast EEG activity is associated with an alert aroused state;      
    high-amplitude, slow EEG activity (alpha waves) is associated with a relaxed but awake state
     EEG can be used to study brain activity in real time, in response to specific events.      These are called evoked potentials

          (use Digital Image Archive Figure CH05F09.BMP).

Usually, many evoked potentials are used to generate an averaged evoked potential in order to reduce the noise of the background EEG activity
          (use Digital Image Archive Figure CHO5FJO.BMP)

-     EEG recording is a valuable diagnostic tool; for example, the presence of high-amplitude spikes in the EEG (i.e., epileptic spikes) is the primary criterion for diagnosing epilepsy

b.     Measures of Somatic Nervous System Activity

1.     Electromyography (EMG)

-     an EMG signal is the changing difference in the voltage between two large electrodes placed on the skin over a large muscle;

     the amplitude of EMG signals indicates the combined level of tension in the underlying muscle;
     the raw signals are usually integrated; the graph of the integrated activity is easier to interpret; the height of the curve of integrated EMG activity indicates the number of spikes in the EMG signal per unit of time
 (use Digital Image Archive Figure CHO5F14.BMP)


2.  Electrooculography (EOG)

     in EOG, eye movements are recorded by placing four electrodes around the eye; the signal results from the fact that the front of eye is more positively charged than the back

-     the direction of eye movement can be inferred from the relation between the activity recorded on two channels: (1) above vs. below and (2) left vs. right

c.     Autonomic Nervous System Activity

-     heart rate; electrocardiogram (ECG)
-     blood pressure is expressed as peak pressure during systoles over minimum pressure during diastoles;   130/70 mm/Hg is normal; greater than 150/90 is hypertension; the device commonly used to measure blood pressure is a sphygmomanometer
-     plethysmography is the measurement of the volume of blood in a body structure (e.g., penis); this is done either with a strain gauge or by measuring the amount of light absorbed by the structure
-     skin conductance; skin conductance level (SCL) is the general level of skin conductance associated with a particular situation; a skin conductance response (SCR) is a rapid change in skin conductance in response to a particular event; one application is the lie detector test

3.     Invasive Physiological and Pharmacological Methods

-     in most cases, laboratory animals serve as the subjects when invasive procedures are required to directly manipulate or measure the brain

a.     Stereotaxic Surgery

          (use Digital Image Archive Figure CHOSF14.BMP)


-  the first step in many invasive biopsychology experiments is stereotaxic surgery-     the method employs a stereotaxic atlas and a stereotaxic instrument (head holder; electrode holder);

the reference point is often bregma -  (the point where two main plates of the rat skull naturally fuse together)

b.     Lesion Methods

     the aspiration method is often used to remove cortical tissue

the radio-frequencv (high-frequency) electrolytic lesion is the most common subcortical lesion;   the tissue is destroyed by the heat of the current
small knife cuts are often used for severing tracts

          (use Digital Image Archive Figure CH05F15.BMP)

cryogenic blockade is like a reversible lesion; the tissue is temporarily cooled to the point that all neural activity in the vicinity of the probe stops





     (use Digital Image Archive Figure CH05F16.BMP)


c.     Electrical Stimulation

-     the effects of electrical stimulation are often opposite to those of a lesion to the same brain site

-     electrical stimulation research is done prior to any lesioning


d.     Electrical Recording Methods
          (use Digital Image Archive Figure CH05F17.BMP)


     1.     intracellular unit recording

-     is a measure of changes in the membrane potential of a neuron over time; it requires that a microelectrode be positioned inside a neuron;
          all of the recording that was discussed in Chapter 4 is of this type

     it is next to impossible to record intracellularly in a freely moving animal because it is difficult to keep the microelectrode inside the neuron

     2.     extracellular unit recording

a microelectrode is positioned near a neuron; the signal is a series of spikes;
     each spike indicates an action potential from a nearby neuron;
     spikes of the same amplitude are assumed to come from the same neuron

     3.     multiple unit recording

multiple-unit recording provides an indication of the rate of firing in the vicinity of the electrode tip;
an electrode larger than a microelectrode picks up the action potentials from many nearby neurons

the signal is integrated so that the height of the curve indicates the number of action potentials in the vicinity per unit of time

     4.     invasive EEG recording

implanted electrodes are used to record EEG in laboratory animals because scalp electrodes do not allow as clear or finite position recording

e.     Psychopharmacological Methods

1.  Drug Administration:
peripheral routes of drug administration include:
 Intra Gastric,
 Intra Peritoneal,
 Intra Venous,
 Sub Cutaneous,
 Intra Muscular

The problem with these routes of drug administration is that many drugs cannot pass the blood-brain barrier;
this problem can be overcome by administering drugs via intraventricular cannula or by microinjection of drugs directly into brain tissue

2.  Selective Chemical Lesions:

-     6-hydroxydopamine (6-OHDA) is a neurotoxin that selectively destroys dopaminergic and noradrenergic neurons in the vicinity of the injection site

-     kainic acid or ibotenic acid destroy neurons with cell bodies at the site of injection, but they leave axons passing through the area undamaged

3.  Measuring the Chemical Activity of the Brain in Behavioral Experiments:

2-deoxyglucose autoradiography
First, radioactive 2-DG is injected;
then the animal performs the test activity of interest

     the animal is immediately killed, its brain is removed and sliced, the slices are coated with a photographic emulsion, and finally after a few days in the dark, the areas of the brain that were particularly active during the test activity show up as dark spots of radioactivity; this procedure is called autoradiography

In Vivo Cerebral Microdialysis

     This technique is used to measure neurotransmitters and chemicals secreted by the neuron during synaptic transmission in behaving animals
     a fine U-shaped tube is inserted into the brain of an animal;
     a solution circulates through the tube
     at the tip, the tube is semipermeable so that chemicals are continuously drawn from the brain into the solution in the tube, where they are carried away for analysis

In Vivo Voltammetry

     changes in the concentrations of certain neurochemicals can be inferred from changes in flow of current across a carbon-based electrode as the voltage is gradually increased; these changes can be measured as the subject is engaged in various behaviors

Locating Neurotransmitters and Receptors in the Brain:

     Immunocytochemistry:

-     involves injecting antigens (foreign proteins) into an animal such that the animal will create and bind antibodies to the antigen to remove or destroy it

-     antibodies for most of the brain's peptide neurotransmitters and receptors have been created, thus specific neuroproteins can be located by radio-active labeling the antibodies and allowing antibodies to attach to the neuroproteins;
     brain tissue is then removed and sliced to reveal locations where labels have accumulated on neuroproteins

     In Situ Hybridization:

     allows peptides and proteins in the brain to be located by obtaining hybrid RNA strands with a base sequence complementary to the mRNA for synthesizing the target neuroprotein;
      labeling the hybrid RNA which then binds to complementary mRNA strands allows the target neuroprotein's location to be marked


4.     Genetic Engineering

     a.     Gene Knockout Techniques:

involve the creation of organisms that lack a specific gene; any measurable neural or behavioral anomalies are then noted

PROBLEMS with this approach:

1) Most behaviors are polymorphic traits (brought about by the action of more than one gene;
2) Eliminating one gene usually alters the expression of other genes;
3) gene expression is often dependent upon experience, which may be altered by the absence of the missing gene; and
4) control subjects and knockout subjects have different DNA, due to the procedure used to create the knockout organism.

b.     Gene Replacement Techniques:
-     involves the replacement of one gene with another; useful implications for the treatment of genetically related diseases.
-     sometimes, genetic information from a different species is implanted, creating a transgenic subject.


Lecture 5b  BEHAVIORAL RESEARCH METHODS OF BIOPSYCHOLOGY

Outline
1.  Neuropsychological Testing
     a.     General Intelligence
     b.     Lateralization
     c.     Memory
     d.     Language
     e.     Perceptual-Motor Function
2.  Behavioral Methods of Cognitive Neuroscience
     a.     Constituent Cognitive Processes Assumption
     b.     Paired Image Subtraction Technique
3.  Paradigms of Animal Behavior
     a.     Analysis of Species-Common Behaviors
     b.     Traditional Conditioning Paradigms
     c.     Seminatural Animal Learning Paradigms
4.  Conclusion: Converging Operations

Lecture Notes

1.  Neuropsychological Testing

Methods used to assess psychological deficits of human patients suspected of having brain damage.
a.     General Intelligence:
Most neuropsychological assessments begin with the Wechsler Adult Intelligence Scale (WAIS)
  It has 11 subtests;
     6 comprise the verbal scale (e.g., Digit Span, Information, Similarities);
     5 comprise the performance scale (e.g., block design, object assembly)

b.  Lateralization:

Evaluating the effects of damage to the right and left hemispheres
-     the following two tests are well known tests of language lateralization

-     sodium amytal test: sodium amytal is injected first into one carotid artery and then, many                minutes later, into the other;
     the patient is mute following an injection ipsilateral to the dominant hemisphere for language;      but the patient makes only a few minor speech errors after an injection contralateral to the                dominant hemisphere for language

-     dichotic listening test: it is a noninvasive test;
          three pairs of digits are presented to the subject through headphones;
          the two digits of each pair are presented simultaneously, one to each ear;
          the subjects are asked to report the six digits that they heard;
          they do slightly better through the ear contralateral to the hemisphere dominant for                     language
c.  Memory
-     the WAIS digit-span subtest is the most common test of verbal short-term memory
-     the WAIS information test (who is the president of the U.S.A.?) is a quick way of identiiying                gross deficits in long-term verbal memory; these can be adapted to an individual's culture
-     a thorough assessment of the various types of memory requires several tests

d.  Language

-     the token test is a good initial screening test for language-related deficits;
     (if the token test identifies deficits, it is followed up by a battery of tests of language ability)
     there are 20 tokens of 2 different shapes, 2 different sizes, and 2 different colors;
     the subject is asked to carry out various acts such as
          "touch the small blue circle and then the large green square
e.  Frontal Lobe Function
-      the Wisconsin Card Sorting Test is often used      (use Digilal Image Archive Figure CH05F22.BMP)


  -     each card in the deck has 1, 2, 3, or 4 triangles, circles, squares, or crosses that are all red, green, yellow, or blue
  -     the subject is told to sort the cards into four different piles but is not told on what basis the sorting is to be accomplished;
     they are told after each card is placed in a pile whether or not it was correctly placed
-     at first the patient must learn to sort by color, but once she or he has learned this sorting principle, the correct principle changes without warning to form or number
 -     patients with frontal-lobe lesions adapt poorly to rule changes;
     they perseverate (continue to respond in a previously correct fashion long after it has become     incorrect)

2.  Behavioral Methods of Cognitive Neuroscience

a.  The constituent cognitive process assumption refers to the premise that complex cognitive processes are the combined activity of simple cognitive processes;
  and that each constituent cognitive process is mediated by neural activity in a particular area of the brain

-     Cognitive psychologists, computer scientists, and neuroscientists combine efforts to model complex cognitive processes, for clinical as well as artificial intelligence applications

b.  Paired-image subtraction techniques

-     are key to coginitive neuroscience research by examining PET or functional MRI images on tasks that differ in only one constituent cognitive process;
     The difference between the two PET or fMRI images is thus viewed as specific to the one constituent cognitive process that was different between the two images

-     processes such as seeing, reading, thinking of, and speaking the same words are frequently used in this type of research

3.  Animal Behavior Paradigms

a.  Analysis of Species-Common Behaviors

-     these behaviors are displayed in the same form by virtually all members of a species, of the same sex (e.g., grooming, swimming, nest building, copulating)

-     the open-field test provides three measures of emotionality:
          (1) degree of inactivity,
          (2) thigmotaxis. and
          (3) defecation

-     Aggression and defense can be studied by recording encounters between a small male intruder and a colony's dominant (alpha) male;
     aggression involves a sideways approach, sideways pushing, piloerection, and biting directed at the back;
     defense involves boxing, rolling over onto the back (protecting it), biting the face, freezing, and fleeing

-     rat sexual behavior is another species-common behavior that is widely studied

-     two common measures of female rat sexual receptivity are:
     (1) lordosis quotient (proportion of mounts producing lordosis), and
     (2) degree of concavity of the back during lordosis

-     male rat behaviors measured include:
     (1) number of mounts to intromission.
     (2) number of intromissions to ejaculation,
     (3) and time to reinitiate mounting after ejaculation (called the postelaculatory interval)

b.  Traditional Conditioning Paradigms

-  Traditional conditioning paradigms play an important role in biopsychology for two reasons:
     (1) conditioning is a phenomenon of primary interest to psychologists; and
     (2) conditioning procedures are often used to train laboratory animals to perform as required in behavioral experiments

  There are two kinds of traditional conditioning paradigms:

     1)  Pavlovian conditioning:      in which a

     neutral stimulus called a conditioned stimulus (CS; e.g., tone) is paired with an
     unconditioned stimulus (US; e.g. meat powder) that elicits an      unconditioned response (UR; e.g. salivation).

     As the CS becomes associated with the US, it begins to elicit a response on its own which is referred to as a conditional response (CR).
          The CR is usually similar to the UR, but this is not always the case.

     2)  Operant Conditioning (AKA Instrumental Conditioning) in which

     the rate of a particular response (pressing a bar) is
     increased by reinforcement or
     decreased by punishment.

c.  Seminatural Animal Learning Paradigms

-     ethoexperimental animal learning paradigms are controlled laboratory paradigms for studying forms of learning that are assumed to occur in the rat's natural environment;
     the following are four examples:

1)  Conditioned Taste Aversion:

     -     the most influential ethoexperimental learning paradigm;

  Rats and many other animals learn the relation between a new taste (or smell) and subsequent      gastrointestinal distress in one trial and subsequently avoid the novel taste

-     taste aversion conditioning experiments in the 1960s challenged three widely held views of learning that had grown out of the study of the traditional conditioning paradigms:

     (1) the view that learning is a gradual step-by-step process by showing that it could occur reliably in one trial,

     (2) the view that temporal contiguity is necessary for learning by showing that conditioning occurred even when the taste and distress were separated by several hours, and

     (3) the view that associations between any two stimuli are equally easy to learn (the principle of epuipotentiality) by showing that rats could learn the relation between gastrointestinal distress and a taste, but not a light for example.

2) Radial-Arm Maze:     (use Digital Image Archive Figure CH05F25.AMP)


-     This device is used to study foraging behavior in the laboratory
-     foraging in the wild is complex; the rat must learn where food is likely to be,
     and not to immediately revisit a stripped site where all the food has been consumed

     in the radial-arm maze rats learn to go directly to the arms that are baited with food each day, but they rarely visit the same arm twice on a given trial

3) Morris Water Maze:

-     is laboratory paradigm used to study rat spatial ability;
     the Morris water maze is a large tub of milky water; to get out of the water,
rats must learn to swim to a slightly submerged (invisible) goal platform
-     rats learn to do this very quickly, even when they are placed in the water at a different position on each trial; they use external room cues to guide them
-     it is interesting to look at their search strategies when the platform has been moved to a new location

4) Conditioned Defensive Burying:

-     based on observation that rats exposed to an inanimate object that has been the source of a single      aversive stimulus (e.g., a shock, a bad odor, an airblast, or a flash) will often bury it
-     they bury it by facing it and spraying bedding or sand at it with their head and forelegs
-     it has been used to study antianxiety drug effects which reduce conditioned defensive burying at low doses

4.  Conclusion: Converging Operations

-     you have now learned about many research methods used by biopsychologists; they all have strengths, but they all have weaknesses

-     the key to scientific progress lies in bringing several methods to bear on the same problem so that each compensates for the shortcomings of the others


Suggested Websites for Lecture 5b:

The Wechsler Intelligence Scales: http://www.richmond.edu/-capc/wechsler page.html
A page focusing on the Wechsler Intelligence scales, including a history of the WAI S, its subscales, and the WISC. See the Pros and Cons section for high (and low) points of these scales.

Virtual Operant Conditioning: http://www.thecroft.com/psy/op.rat.html
     Website for OpRat, software that allows students to study the operant behavior of a virtual rat. Downloadable software is available, although the full version of the software is only available commercially.

Why Study Animal Behavior?
http://www.animalbehavior.org/ABS/Education/valueofanimabehavior.html
     From Dr. Charles Snowdon, a past president of the Animal Behavior Society; thoughtful essay on the value of basic and applied animal research.

Experiments in Cognitive Psychology: http://www.psych.purdue.edu/~coglab/demos.html
     From Purdue University's Cognitive Psychology group, a collection of experiments useful for lab instruction or simply a better understanding of some basic phenomena in the area.