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Neurological Basis of Behavior (PSY - 610)

Lesson15

RESEARCH METHODS AND TECHNIQUES OF ASSESSMENT OF BRAIN FUNCTION

Objectives:

To familiarize the students with

· The various techniques used to study the brain and its function and structures.

· Invasive vs. Non- Invasive methods, Stereotaxic surgery.

· Stereotaxic Atlas used for brain surgery and manipulation,

· Histological and cytological methods for Cell staining, Radio labelling, Flourescence,

autoradiography, Lesioning and electrical stimulation, single cell recordings, push-pull

cannulae.

· The advanced techniques such as MRI, fMRI, CAT, PET, CT, EEG, EOG, EMG, X Ray etc

Histological, electrical chemical and pharmacological processes and techniques why so many?

· Advanced technologies and methodologies

· Electrophysiological methods: these are methods which measure changes of the electrical

potential and charge in the brain

Single microelectrode recording: A single thin neuron about 5-10 UM (micromolar), or a

microelectrode (1-3 UM) glass tubings or steel pens are used to record electrical potential. This is

how the all-or none axonal activity was measured and identified. This is also how responses to a

single stimulus single resulting in neuronal firing were first measured by Hubel and Weisel using the

visual systems of the kittens (intracellular/ extracellular recordings are possible with this technique.

Macro electrodes: These involve inserting large electrodes in large neurons. The large tips help

measure evoked potentials (EP's) of these areas, (response to a stimulus or stimulation. There are

many neurons firing in an area, and these are then magnified to a point one can hear the loud firing of

the neurons in a typical EP average evoked potential.

Surface/Scalp electrode in a region: Electroencephalography recordings are done for the human brain

and recording can show variation (during sleep) and other behaviors.

Advanced Technology:

Earlier investigations in the neurosciences were limited by the techniques available to the researcher.

Since the 1970's with the advancement of technology and the development of sophisticated equipment, it

became possible to carry out intricate experiments and measurements. These technologies which could

scan the body and brain opened up new areas of research. These are now used for research in brain

sciences and in combination with other techniques; the canvas for researchers becomes larger.

· Contrast rays: The contrast X rays involves injecting part of the brain with a dye or some

substance which would block X rays. This is then contrasted with its surrounds or the lateral part

which is not injected so, basically the contrast is compared with the non injected X-Rays. This

does provide some basic information such as the location and size of a tumor in the brain or

cerebral circulatory system.

· X-Ray Computed Axial Tomography: CAT scan was initiated in early 70's. This is a

procedure involves taking multiple X ray's from different points while the patient is lying in a

chamber and information fed to computers attached . The rotating X ray tube and detectors thus

provide the basis for the 3 dimensional images developed by computers. This method is better

than a black and white X ray which only gives very simple information; however, this cannot

measure on going changes as this is a static method.

· Magnetic Resonance Imaging (MRI). (Resonance means echoing).The patient is placed in a

chamber of which is a highly charged magnetic field. The MRI's are high resolution images

reconstructed on the basis of waves, emitted by the hydrogen atoms after these atoms are

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Neurological Basis of Behavior (PSY - 610)

activated by radio frequency waves in the magnetic field chamber. It is possible to get 2 or 3

dimensional images with MRI. Due to the high spatial resolution, MRI gives clear differences

between different loci, and tissues as is done in structural MRI. The functional MRI is used when

the brain is functioning to get images which are a clear indication of the areas where most

activity is taking place or most oxygen being used, such as testing a patient and asking him to

remember a list of words. This way we can see how different brain parts are used during

learning.

Positron Emission Tomography PET Brain images of ongoing brain activity rather than just

the brain structure (earlier techniques did just that). The technique of injecting radio labelled

substances such as 2-DG glucose works in combination with this technique. 2-DG glucose is

injected into the carotid artery which is taken up by the brain and, shows up in brain areas of

high activity (where glucose is normally needed). High usage would show up red (highest levels

of radioactive glucose), yellow orange, blue (least levels of glucose, therefore least activity). The

PET scan can also use blood flow, using nitricoxide (vasodilator). This shows activity and blood

usage, as wherever there is activity, there is greater blood flow. PET scans are also effective in

assessing ongoing activity

fMRI vs. PET

a) no injection needed in fMRI whereas in PET we inject radiolabeeld substances

b) fMRI's are both structural and functional, whereas the PET is only functional ( of varied kind

blood, glucose usage)

c)fMRI has clearer resolution of various parts Both techniques cannot collate

information over time ( to see how changes taking place before and after comparison)

Assays: These are procedure undertaken using various chemicals using blood urine,

extraction, and tissue of the brain (taken postmortem). There are many procedures.

Assays a) whole brain various metabolites are assayed post mortem. This can be done taking

the whole brain or specific brain areas to measure amount of chemicals in the areas the brain is

homogenized in the homogenizer and the chemicals and their levels measured.

Assays b) other assays can be carried out on the blood or urine or the Cerebrospinal fluid

(CSF). The findings that Schizophrenics urine has high levels of MHPG, a metabolite of

neurotransmitter catecholamines, indicating that they are involved in the disorder.

Neurophysiological measures There are many procedures which measure electrical activity of the

brain and other tissues to give us an assessment of the working of these areas.

EEG: Electroencephalography: This gives us an idea of the ongoing electrical activity in the

brain. Scalp electrodes are placed at various locations (temporal, frontal, occipital, and

parietal) to get a recording of the electrical charge and electrical activity of the different parts at

the same time. These electrodes pick the electrical signals and then these are sent to a magnifier

where they can be seen on the oscilloscope. Though this does not give us a clear idea of how

each neuron is working, but the general patterns are consistent and have been shown across

species. For example, the sleep state recording would show us when a person or animal enters

deep sleep the recording show Low frequency, high amplitude waves (1-3 cycles per second).

EOG Electro-oculograph: These measure the electrical activity of eye muscles to monitor the

eye movement using electrodes placed on the eyes. This is most effective in sleep studies

where Rapid Eye Movement ( REM) sleep stage can be seen through changes in EOG activity.

This works well with the EEG recordings to study sleep.

EMG: Electromyograph: Measuring electrical activity of the muscle. In this procedure

electrodes are placed on the muscle that we are measuring. The muscular tension/ tone of the

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Neurological Basis of Behavior (PSY - 610)

neck muscles is also measured in sleep and is a very good indicator of the changes form Non

REM to REM sleep.

Polygraphic recording For measuring electrical skin conductance along with other measures

such as Blood pressure, Pulse rate, and breathing is measured as an orchestrated response,

Reference

1. Kalat J.W (1998) Biological Psychology Brooks/ Cole Publishing

2. Carlson N.R. (2005) Foundations of Physiological Psychology Allyn and Bacon, Boston

3. Pinel, John P.J. (2003) Biopsychology (5th edition) Allyn and Bacon Singapore

4 Bloom F, Nelson and Lazerson (2001), Behavioral Neuroscience: Brain, Mind and Behaviors (3rd

edition) Worth Publishers New York

5. Bridgeman,B (1988)The Biology of Behaviour and Mind. John Wiley and Sons New York

6. Seigel,G.J. ( Ed. in chief) Agranoff, B.W, Albers W.R. and Molinoff, P.B. (Eds) Basic

Neurochemistry: Molecular, Cellular and Medical Aspects.

7. Brown,T.S. And Wallace. (1980) P.M Physiological Psychology

Academic Press New York

Note: References #2, 3, and 4 are followed most closely, as they have been used in teaching as well;

further individual references/pages are also given on the power points of each lesson.