4Behavioral and Neuroscience Methods

Introduction

Behavioral and Neuroscientific Methods are used to get a better understanding of how our brain influences the way we think, feel,, and act. There are many different methods which help us to analyze the' brain and as well to give us an overview of the relationship between brain and behaviour. Well-known technique are the EEG (Electroencephalography) which records the brain’s electrical activity and the fMRI (functional magnetic resonance imaging) method whichLobes of the brain tells us more about brain functions. Other methods, such as the lesion method, are not as well-known but still very influential in today's neuroscientific research.

Methods can be summmed up in the following categories: There are techniques for assessing brain anatomy and others for assessing physiological functions. Furthermore there are techniques for modulating brain activity, analyzing behaviour or for modeling brain- behaviour relationships. In some cases, as in the lesion method, patients with brain damage are examined to determine which brain structures were damaged and to what extent this influences the patient's behaviour.

Studies on humans with brain damages

Lesion method

The brain is a complicated structure, composed of many structures. It seems obvious that any task a person performs needs the successful work of the brain's components. A long-standing method of the neurophysiologist has been to study how behaviour is altered by selectively removing one or more of these parts. If a neural structure contributes to a task, then rendering structure dysfunctional should impair the performance of that task. A lesion is an area of the brain that is damaged in both structure and function. If this damage of the brain region leads to an inability of performig a particular mental function, then this function and brain region must be correlated with each other. This means that the function depended on the brain region, and is called lesion method. Lesions can occur accidentally in the course of life events, or can be caused deliberately, in a laboratory. The lesion method relates the area of a lesion, to loss in behaviour. Put simply: If structure X is damaged, and changes in behavior Y occur, we can infer that structure X caused, or at least had to do with, behaviour Y.

Example: Paul Broca examined the brain of a patient who lost almost all his language ability. Broca found a lesion in the left frontal lobe. Based on several examples of this, he concluded that the ability to speak is at least partially controlled by this area, now referred to as Broca's area.

Because of the nature of non-laboratory settings, lesions such as these cannot be considered experimentally valid. So experimental lesioning occurs mainly with animals. Various animals are used for chemically inducing lesions in their brains, thereafter they are compared to various control groups in order to determine specifically where, and to what degree, a structure controls a behaviour.

Areas where it is used

The lesion method can be used as experimental probes to investigate hypotheses about the relationship between the brain and cognitive processes.In this field research is done a lot with animals, where lesions are created in a particular brain region, and then the effects on the behaviour of this lesion are observed. Humans obviously cannot be subjected to brain lesions to investigate their nervous sytem’s function. Human neuropsychology requires patients with naturally occurring lesions, generally accidentally under particular circumstances. Because of this fact the researchers have no control over the location or extent of the lesion, and because of this research on humans is only rarely possible.

According to the goal of the researcher, he can choose between two approaches concerning the lesion method. One of the approach serves for investigation of neural systems, whereby the other approach accentuates cognitive processes. The approach of neural systems deals with the task to find out what functions are correlated with a specific brain region. Due to the fact that it is possible that a specific function is not only supported by one brain region, but can also be supported by other brain
regions, it is important to do experiments with groups of patients who had damage in a brain region and because of this a loss of a specific function, but also to do experiments with groups of patients, who had damage in an other brain region. This allows the researchers to find out if a function is correlated with one specific brain region or also with other brain regions. This research enables inestimable information about the relationship between brain areas and cognitive functions, which in turn is useful for other medically related professionals, like neurosurgeons, clinical neuropsychologists etc.

The approach which distinguishes the cognitive processes fiddles with behavioral signs, where primarily the region of the brain damage plays little role. It is important that the group of patienst have the same behavioral deficit, so the researchers have the possibility to examine each patients damaged brain region. If the researchers determine that there is similarity in the location of the damages brain region, they can allege hypotheses, that a specific brain region supports a cognitive function. Research in this field allows to affect the location of the brain damage more closely, when patients show the same behavioral signs. This facilitates to say more about the particular neural structure of the damaged brain area and which loss of function results.

Problems which can occur

Even though the lesion method is an important method and so to say the cornerstone of cognitive neuroscience, because it enables to make hypotheses about the relationship between brain and behaviour, it has limitations. These limitations depend on the variableness of the properties of the brain damage, as well as on the variability of the attributes of the patients. For example the location and extent of the damage could be variable in the different cases of patients. And also the different characteristics of the patients make it difficult to give definitive conclusions about the correlation between a specific brain region and a particular cognitive function.

Comparative Brain Size

Experimental lesions done with animals, resemble in the accomplishment. Generally the animals for the experiments are raised in the same environment, have the same lesion at the same age, so their characteristics are near the same. Because of this resemblance in general the same behavioral deficits are observable after the lesion. Contrary to the lesions with animals, individuals with brain damages are absolutely different. They are not raised in the same environment, have different ages at time of the lesion and other differences. This fact makes it difficult to give definite statements about the correlation between specefic brain regions and cognitive fuctions. These difficulties can also result in improper conclusions. Moreover the lesions created in animals are more specific, because the researcher creates the lesion in a certain manner, and because of this has more control over the lesion, whereby lesions by humans are much less specific. The lesions vary in location, extent and origin, this complicates to make definite inferences about neural strucures and their influence on cognitive functions. Another limitation of the lesion mehtod reflects in the fact, that it is hardly possible to determine which function is supported by the damaged brain region. It is only possible to watch how the rest of the brain works without the damaged brain region. First of all, only the brain regions which are crucial for a specific function can be determined, but not the rest of the brain regions which may be as well important for that function. Furthermore it is not definitively find out, if a brain region is really crucial for a specific function, or if this brain region connects only other brain regions, which are important for the performance of this specific function. All in all one can say that the lesion method has two major limitations, which occur, because of the complex structure of the brain, and because it is never possible to determine definitively if the damaged brain region is the real reason for the loss of a cognitive function. These perceived limitations of the lesion method provided a strong incentive for the parallel development of functional imaging, which offered a new means of studying the dynamic neural correlates of cognitive processes in normal humans. Two key techniques were developed: positron-emission tomography (PET) and functional magnetic resonance imaging (fMRI).

single case studies

Perhaps the most famous single case study involving lesions occurred in the 19th century. A young man named Phineas Gage was working on railroad construction in 1848. One day, a 3ft, 7in (1.0922m) tamping iron (a long metal pole), 1.25in (0.381m) in diameter, was propelled through Gage's skull, through the left frontal lobe of his brain and out the other side of his head. Miraculously, Gage survived, but he was not the same. Phineas had previously been the foreman of the construction crew. He was well regarded as stable, well mannered, good handeling money. After his left frontal lobe was destroyed, his personality changed. He began to cuss inappropriately, gamble, drink. In other words, he exhibited personality changes dealing with self control.

Because his left frontal lobe was damaged in the accident, it can be inferred that that is the area of the brain that deals with personality traits and self control. Unfortunately, because this is a case study, and not a controlled experiment, any inferences can't be truly accepted, but this idea of connecting brain damage to behavioral changes is the core idea behind lesion experiments.

Techniques for Assessing Brain Anatomy

Are the art of creating images of the inside of an organism without (necessarily) killing it. There's a lot of complexity on the inside of something that you can't guess from the outside, to explore or create images of the inside of an organism e.g. brain without killing it or cutting it in slices CAT as well as MRI are imaging technique which use changes in electrically charged molecules when they are placed in a magnetic field to assess differences in cerebral activity in different regions of the brain. Both technologies are more precise than ordinary X-ray and help us “map” the brain regions associated with different behaviours, often by studying people with specific brain injuries. MRI images are clearer than CAT scans and don't use radiation; they show brain atrophy and increased cerebrospinal fluid

CAT

CAT scanning was invented in 1972 by the British engineer Godfey N. Hounsfield (later Sir Godfrey) and the South African (later American) physicist Alan Cromack.

CAT (computed axial tomography) is a painless test that uses multiple x-ray images, taken from different angles, to create three-dimensional images of body structures. Increasingly, CAT scans use digital x-rays to produce their images on a computer screen. The tomograms ``cuts`` for the CAT scan are usually made 5 or 10 mm apart. The CAT machine rotates 180 degrees around the patient's body; hence, the term "axial." The machine sends out a thin X-ray beam at 160 different points. Crystals positioned at the opposite points of the beam pick up and record the absorption rates of the varying thicknesses of tissue and bone. The data are then relayed to a computer that turns the information into a 2-dimensional cross-sectional image. Risks

CT scan risks are similar to those of conventional X-rays. During the CT scan, you're briefly exposed to radiation. But scientists believe that CT scans provide enough valuable information to outweigh the associated risks. But if the subject or the patient: Pregnant it may be recommended to do another type of exam to reduce the possible risk of exposing his fetus to radiation. Have asthma or allergies. And the CT scan requires a contrast medium, there's a slight risk of an allergic reaction to the contrast medium. Have certain medical conditions. Diabetes, asthma, heart disease, kidney problems or thyroid conditions also increase the risk of a reaction to contrast medium.

MRI

Although CAT scanning was a breakthrough, in manyl cases it was substituted by Magnetic resonance imaging (also known as MRI) since magnetic resonance imaging is a method of looking inside the body without using x-rays, harmful dyes or surgery. Instead, radio waves and a strong magnetic field are used in order to provide remarkably] clear and detailed pictures of internal organs and tissues.

History and Development of MRI

A full size MRI-Scanner. (GFDL - Kasuga Huang)

MRI is based on a physics phenomenon, called nuclear magnetic resonance (NMR), which was discovered in1930s byl Felix Bloch (working at Stanford University) and Edwardl Purcell(from Harvard University). In this resonance, magnetic! fields and radio waves cause atoms to give off tiny radio! signals. In the year 1970, Raymond Damadian, a medical! doctor and research scientist, discovered the basis for using! magnetic resonance imaging as a tool for medical diagnosis] Four years later a patent was granted, which was the worlds . first patent issued in the field of MRI. In 1977, Dr. Damadianl completed the construction of the first “whole-body” MRI scanner, which he called the ”Indomitable”. The medical use of magnetic resonance imaging has developed rapidly. The first MRI equipment in health were available at the beginning of the

1980s. In 2002, approximately 22000 MRI scanners were in MRI_________- ____ ... ..

use worldwide, and more than 60 million MRI examinations head side (GFDL - ™n) were performed.

Common Uses of the MRI Procedure

Because of its detailed and clear pictures, MRI is widely used to diagnose sports-related injuries,
especially those affecting the knee, elbow, shoulder, hip and wrist. Furthermore, MRI of the heart, aorta and blood vessels is a fast, non-invasive tool for diagnosing artery desease and heart problems. The doctors can even examine the size of the heart-chambers and determine the extent of damage, cause by a heart desease or a heart attack. Organs like lungs, liver or spleen can also be examined in high detail with MRI. Because no radiation exposure is involved, MRI is often the preferred diagnostic tool for examination of the male and female reproductive systems, pelvis and hips and the bladder.

Risks

An undetected metal implant may be affected by the strong magnetic field. MRI is generally avoided in the first 12 weeks of pregnancy. Scientists usually use other methods of imaging, such as ultrasound, on pregnant women unless there is a strong medical reason to use MRI.

Techniques for Assessing Physiological Function

PET

Positron emission tomography, also called PE imaging or a PET scan, is a diagnostic examination! that involves the acquisition of physiologic images based on the detection of radiation from the emission of positrons. It is currently the most effective way to check for cancer recurrences. Positrons are tiny particles emitted from a| radioactive substance administered to the patient. This radiopharmaceutical is injected to the patient and its emissions are measured by a PET scanner.

A PET scanner consists of an array of detectors that surround the patient. Using the gamma rayPET signals given off by the injected radionuclide, PET measures the amount of metabolic activity at a site in the body and a computer reassembles the signals into images. PET's ability to measure metabolism is very useful in diagnosing Altsheimer's desease, Parkinson's desease, epilepsy and other neurological conditions, because it can precisely illustrate areas where brain activity differs from the norm. It is also one of the most accurate methods available to localize areas of the brain causing epileptic seizures and to determine if surgery is a treatment option. PET is often used in conjunction with an MRI or CT scan through "fusion" to give a full three-dimensional view of an organ.

PET scan images

fMRI

fMRI (Functional Magnetic Resonance Imaging) is a technique for determining which parts of the brain are activated by different types of physical sensation or stimuli such as sight, sound or the movement of a subject's fingers. The brain mapping is done by setting up an MRI scanner in a special way so that the increased blood flow to the activated areas of the brain shows up on Functional MRI scans. Compared to MRI, fMRI does not depend on contrast agents although contrast agents enable far greater detection sensitivity than BOLD (Blood Oxygenation Level Dependent) signal. Higher BOLD signal intensities arise from decreases in the concentration of deoxygenated hemoglobin.

An fMRI experiment usually lasts 1-2 hours. The subject will lie in the magnet and a particular form of stimulation will be set up and MRI images of the subject's brain are taken. In the first step a high resolution single scan is taken. This is used later as a background for highlighting the brain areas which were activated by the stimulus. In the next step a series of low resolution scans are taken over time, for example, 150 scans, one every 5 seconds. For some of these scans, the stimulus will be presented, and for some of the scans, the stimulus will be absent. The low resolution brain images in the two cases can be compared, to see which parts of the brain were activated by the stimulus.

The rest of the analysis is done using a series of tools which correct distortions in the images, remove the effect of the subject moving their head during the experiment, and compare the low resolution images taken when the stimulus was off with those taken when it was on. The final statistical image shows up bright in those parts of the brain which were activated by this experiment. These activated areas are then shown as coloured blobs on top of the original high resolution scan. This image can also be rendered in 3D.

fMRI has moderately good spatial resolution. However, the temporal response of the blood supply, which is the basis of fMRI, is poor relative to the electrical signals that define neuronal communication. Therefore, some research groups are working around this issue by combining fMRI with data collection techniques such as electroencephalography (EEG) or magnetoencephalography (MEG), which have much higher temporal resolution but rather poorer spatial resolution.

Electromagnetic Recording Methods

The methods we have mentioned up to now examine the metabolic activity of the brain. But there are also other cases in which one wants to measure electrical activity of the brain or the magnetic fields produced by the electrical activity. The methods we discussed so far do a great job of identifying where activity is occurring in the brain. A disadvantage of these methods is that they do not measure brain activity on a millisecond-by-millisecond basis. This measuring can be done for example by methods as the single-cell recording or the Electronencephalography (EEG). These methods can measure brain activity really fast and so they can give a best available temporal resolution.

fMRI picture

Single cell

When using the single-cell method an electrode is placed into a region of the brain in which we focus our attention. Now, it is possible for the experimenter to record the electrical output of the cells that are contacted by the exposed electrode tip. The researchers’ goal is to determine for example if the cells respond to information from only specific places in the sensory world or from broad regions of space. Next they want to determine whether the cells are sensitive to input in only one sensory modality or are multimodal in sensitivity. Furthermore they want to find out if the animal’s attention directed to a stimulus influence in a cell’s respond.

Single cell studies are not sufficient for studying the human brain, since it is too invasive to be a common method. Hence, this method is most often used in animals. There are just a few cases in which the single-cell recording is also applied in humans. People with epilepsy sometimes get removed the epileptic tissue. A week before surgery electrodes are implanted into the brain or get placed on the surface of the brain during the surgery to better isolate the source of seizure activity. So using this method one can decrease the possibility that useful tissues will be removed. Next one can find out which properties of a stimulus make cells in those regions fire. Due to the limitations of this method in humans there are other methods which measure electrical activity. Those we are going to discuss next.

EEG

One of the most famous techniques to study brain activity is probably the Electroencephalograhpy (EEG). Most people might know it as a technique which is used clinically to detect abberant activity such as that which accompanies epilepsy and disorders.

Fp1

Fp2

F4

T3

T5

C3

P3

Fz

Cz

Pz

C4

FB

T4

P4

01

In an experimental way this technique is used to show the brain activity in certain psychological states, such as alertness or drowsiness. To measure the brain activity

mental electrodes are placed on the scalp. EachThe right placement of the electrodes. (GFDL - Thekla

electrode, also known as lead, acts as its ownHelmstedt) recording site. Next, a reference is needed which provides a baseline against which the activity at each of the other electrodes can compared.This electrode must not cover muscles, because its contractions are induced by electrical

T6

signals Usually this electrode is placed at the mastiod bone -^^^^^^whv^^f which is located behind the ear.

During the EEG electrodes are places like this. Over the right hemisphere electrodes are labeled with even numbers.Odd numbers are used for those on the left hemisphere. Those on the midline are labeled with a z. Th capital letters stands for the location of the electrode(C=central, F=frontal, Fp= frontal pole, O= occipital, P= parietal and T= temporal).(see picture) EEG Stage

After placing each electrode at the right position the electrical potential can be measured. This electrical potential has a particular voltage and furthermore a particular frequency. Accordingly, to a person’s state the frequency and form of the EEG signal can differ. If a person is awake beta activity can be recognized, which means that the frequency is relatively fast. Just before someone falls asleep one can observe alpha activity, which have a slower frequency. The slowest frequencies are called delta activity, which occur during sleep.

Patients who suffer epilepsy show an increase of the amplitude of firing that can be observed on the EEG record. In addition EEG can also be used to help answering experimental questions. In the case of emotion for example, one can see that there is a greater alpha suppression over the right frontal areas than over the left ones, in the case of depression. One can conclude from this, that depression is accompanied by greater activation of right frontal regions than of left frontal regions.

ERP

Whereas EEG recordings provide a continuous measure of brain activity, event-related potentials (ERPs) are recordings which are linked to the occurrence of an event. A presentation of a stimulus would be such an event. When a stimulus is presented, the electrodes, which are placed on a person’s scalp, record changes in the brain generated by the thousands of neurons under the electrodes.

By measuring the brain's response to an event we can learn how different types of information are processed. Representing the word eat or bake for example causes a positive potential at about 200msec. From this one can conclude, that our brain processes these words 200msec after presenting it. This positive potential is followed by a negative one at about 400msec. This one is also called N400 (whereas N stands for negative and 400 for the time). So in general one can say that there is a letter P or N to denote whether the deflection of the electical signal is positive or negative. And a number, which represent, on average, how many hundreds of milliseconds after stimulus presentation the component appears.

The event-related- potential shows special interest for researchers, because different components of the response indicate different aspects of cognitive processing. For example, presenting the sentences “The cats won’t eat” and “The cat won’t bake”, the N400 response for the word eat is smaller than for the word bake. From this one can draw the conclusion that our brain needs 400msec to register information about a word’s meaning. Furthermore, one can figure out where this activity occurs in the brain, namely if one looks at the position on the scalp of the electrodes that pick up the largest response.

MEG

Magnetoencephalography (MEG) is a related method to the EEG. But instead recording electrical potentials, it uses magnetic potentials at the scalp to index brain activity. To locate a dipole, the magnetic field can be used, because the dipole extreme high points of intensity of the magnetic field. By using devices called SQUIDs (superconducting quantum interference device) MEG can record these magnetic fields.

MEG is mainly used to localize the source of epileptic activity and to locate primary sensory cortices. This is helpful because by locating them they can be avoided during neurological intervention.

Furthermore, MEG can be used to understand more about the neurophysiology underlying psychiatric disorders such as schizophrenia. In addition, MEG can also be used to examine a variety of cognitive processes, such as language, object recognition and spatial processing among others, in people who were neurologically intact.

MEG has some advantage, because as well known, electrical currents conduct through different media to different degrees. The electrical current is also carried in different degrees through brain tissues, cerebral spinal fluid, the skull and the scalp. Magnetic fields instead are not so influenced by these variations. Another advantage is that the strength of the magnetic field which is recorded can also tell us information about how deep within the brain the source is located.

However, MEG also has some disadvantages. The magnetic field in the brain is 100 millionth the size of the earths’ magnetic field. Due to this, shielded rooms, made out of aluminium, are required. Another disadvantage is that MEG cannot detect activity of cells with certain orientations within the brain. For example magnetic fields created by cells with long axes radial to the surface will be invisible.

Techniques for Modulating Brain Activity

Transcranical magnetic stimulation (TMS)

History and procedure

One important technique for modulating brain activity is the so called transcranical magnetic stimulation, better known as TMS. It is a relatively new technique for inducing small, localized, and reversible changes in living brain tissue. By using an electromagnet to produce a rapidly fluctuating magnetic field in the brain, TMS changes the electrical potential in brain tissue, which causes neuronal discharge.

Actually, the first modern TMS device was developed by Antony Baker in the year 1985 in Sheffield after 8 years of research. The field has developed rapidly since than with many researchers using TMS in order to study a variety of brain functions. It has been used, e.g., to block the perception of visual stimuli, in order to cause speech arrest, and to delay the onset of voluntary movements. The clinical effects of TMS have also been investigated in certain neuropsychiatric conditions.+40 Several investigators have suggested the possible efficacy of TMS as a treatment for depression in human trials and animal § ° models. Because of findings such as these, TMS has been I considered as a possible alternative to antidepressant| medication. (1, 2) tit , ., bi^'.-.fiS

Mechanisms

2 3 4

Time (ms)

Although TMS is able to influence many brain functions, Action potential (GFDL - Chris 73)
including movement, visual perception, memory, attention, speech and mood, full knowledge of the neurobiological cascade of events remains unclear still. But studies combining TMS with other neurophysiological and neuroimaging techniques like EEG, PET and fMRI, are helping to explain how TMS achieves its effects.

TMS utilizes the principle of electromagnetic induction. It involves the discharge of very large current from a bank of capacitors, which rapidly flows through a simple LCR circuit and then though a copper-wire coil. A rapid time-varying magnetic field is induced at the level of the coil. When the coil is held to the head of subject, the magnetic field pulse penetrates the scalp and induces a small current in the brain, parallel to the plane of the coil. When the induced current is sufficient, depolarization of neuronal membranes occurs, and thus generation of action potentials are produced. (1)

Basic applications

One of the popular initial uses of TMS was the mapping of the motor cortex, because the effects of the stimulation could be easily measured by EMG of the motor evoked potential in peripheral muscles. Since even earlier researches were aware that TMS could cause suppression of visual perception, speech arrest, and parasthesias, TMS has been used to map specific brain functions in areas other than motor cortex. Several groups have applied TMS to the study of visual information processing, language production, memory, attention, reaction time and even more subtle brain functions such as mood and emotion.

Clinical applications

Although the potential utility of TMS as a treatment tool in various neuropsychiatric disorders is rapidly increasing, its use in depression is the most extensively studied clinical applications to date. For instance in the year 1994, George and Wassermann hypothesized that intermittent stimulation of important prefrontal cortical brain regions might also cause downstream changes in neuronal function that would result in an antidepressant response. In an initial open study it was reported that left prefrontal rTMS(repetitive transcranical magnetic stimulation) might be effective in the treatment of depression as well.

Moreover the transcranical magnetic stimulation shell decrease the frequency of the epileptic attacks. Targau & co could even achieve a decrease of attacks up to 80% in individual cases.

Future of TMS

Although it is too early at this point to tell whether TMS has long lasting therapeutic effects, this tool has clearly opened up new possibilities for clinical exploration and treatment of various psychiatric conditions. Further work understanding normal mental phenomena and how TMS affects these areas appears to be crucial for advancement. A critically important area that will ultimately guide clinical parameters is to combine TMS with functional imaging to directly monitor TMS effects on the brain. Since it appears that TMS at different frequencies has divergent effects on brain activity, TMS with functional brain imaging will be helpful to better delineate not only the behavioural neuropsychology of various psychiatric syndromes, but also some of the pathophysiologic circuits in the brain.

Nevertheless, TMS can be associated with other measures of brain activity as already mentioned
above and such studies promise to further expand the application of TMS in the study of the pathophysiology of neuropsychiatric disorders. This new application of combining TMS and other neuroimaging techniques is already becoming popular in the field of cognitive neuroscience to investigate the brain-behavior relationship. (1)

Techniques for Analyzing Behaviour

Besides using methods to measure the brain’s physiology and anatomy, it is also important to have techniques for analyzing behavior in order to get a better insight on cognition. There are various methods of clinical assessment of behavior, which aim at determining the impacts of brain damages on behavior. The goal of a neuropsychological assessment is to examine in what terms damage to the central nervous system influences cognitive abilities.

Test batteries

A neuropsychological assessment can be achieved, for instance, through the test battery approach, which gives an overview on a person’s cognitive strengths and weaknesses by analyzing different cognitive abilities. A neuropsychological test battery is used by neuropsychologists to discover brain dysfunctions, arisen from neurological or psychiatric disorders. Such batteries do not only test various mental functions, but also the overall intelligence of a person.

The Halstead-Reitan battery is the most popular one, whereas the abilities tested range from basic sensory processing to tests that require complex reasoning. Furthermore, the Halstead-Reitan battery gives information concerning what caused the damage, the brain areas that were harmed, and it provides information about the stage the damage has reached. Such information is very helpful when it comes to propose a rehabilitation program. Another test battery, the Luria-Nebraska battery, is twice as fast to administer than the Halstead-Reitan, and the tests are ordered according to twelve content scales (e.g. motor functions, reading, memory etc.). This battery functions in accordance the view of the psychologist Alexander Luria about the brain, namely that there are three functional systems making up the brain (the brain-stem system, the anterior system and the posterior system), which all relate to one another. The purpose of these batteries is to find out if a person suffers from a brain damage or not, and they work well in discriminating persons with brain damage from neurologically impaired patients, but less well when it comes to discriminating them from persons with psychiatric disorders. In addition to that, test batteries do not only focus on the data results, which assesses the absolute level of performance, but beyond that, test batteries give attention to data on the qualitative manner of performance, and this is useful in gaining a better understanding of the cognitive impairment.

Customized neuropsychological assessment

The so called customized neuropsychological assessment is an alternative to the use test-batteries, in which an examiner develops, according to information from other tests (e.g. WAIS-III [Wechsler Adult Intelligence Scale]), a hypotheses about which cognitive abilities were influenced by brain damage. After the analysis of each hypothesis with a certain neuropsychological test, the hypothesis will either be kept on or it will be abandoned and a new hypothesis will be developed and the procedure will be repeated. In contrast to the test battery assessment, which is a standardized approach, the customized neuropsychological assessment requires a more experienced examiner.

Overall Intelligence tests

The most common used tests to estimate the intelligence of a person are the Wechsler family intelligence tests. These imply the WPPSI-R (Wechsler Preschool and Primary Scale of Intelligence) for children 3-7 years old, the WISC-III (Wechsler Intelligence Scale for Children) for children 6-16 years old, the WAIS-III (Wechsler Adult Intelligence Scale) and the WAIS-NI (Wechsler Adult Intelligence Scale as a Neuropsychological Instrument). Every test gives an estimation of the overall IQ (Full Scale IQ [FSIQ]) and provides two other subscale scores - a Verbal IO (VIQ) and a Performance IQ (PIQ). In the Verbal part of the test, for many subscales (e.g. Vocabulary) the relevant feature of the response is not the timing but that the answers are complete and correct. In the Performance part of the test, on the other hand, the points are given according to how long it takes to give an answer. The special feature of the WAIS-III test is that it gives a profile of certain abilities, in contrast to other tests that give just a single score, and its subtests are dived into four different index scores. Firstly, The Verbal Comprehension Index, which is assessed according to performance on vocabulary, similarities and information, secondly, the Perceptual Cortex Index analyzing non-verbal abilities (e.g. Visual-Motor Integration), thirdly, the Working Memory Index being evaluated according to a person’s digit span, arithmetical performance and object assembly subtests, at last there is the Processing Speed Index according to digit symbol coding and letter-number sequencing. The WAIS-NI test on the other hand has the advantage that it supplies the examiner with information regarding the way the patient approaches problem-solving tasks. For instance, information about how the patient manipulates blocks on the Block Design test can be very useful. Sometimes individuals get quickly tired and overstrained doing a whole WAIS test - in such cases, it is better to let people do only a subset of the WAIS-III tests, as e.g. on similarities or Block Design.

Premorbid functioning

Test batteries and tests on the overall intelligence provide information on the functioning of cognitive abilities of a person. However, brain damage, of course, has an immense impact on the scores of such tests and it is quite difficult for a neurophysiologist to assess how well the functioning was before the brain damage occurred. In order to differentiate in such cases, psychologists try to come up with an estimate of premorbid functioning, which is a warrantable guess on the functioning of a person before the brain damage. Information about the person’s educational background can be taken as such a standard - but it is not the appropriate approach in all cases. The test that is usually used to make an estimation on the premorbid functioning is the Vocabulary subtest of the WAIS-III, because it analyses abilities that do not seem to be influenced by brain damage. If the scores of the estimated premorbid intelligence are significantly higher than the current test scores, it is reasonable to assume that the brain damage caused a decrease in the intellectual strengths of an individual.

Techniques for Modeling Brain-Behaviour Relationships

Another major method, which is used in cognitive neuroscience, is the use of neural networks (computer modelling techniques) in order to simulate the action of the brain and its processes. These models help researchers to test theories of neuropsychological functioning and to derive principles viewing brain-behaviour relationships.

In order to simulate mental functions in humans, a variety of computational models can be

used. The basic component of most such models is a “unit”, which one can imagine as showing neuronlike behaviour. These units receive input from other units, which are summed to produce a net input. The net input to a unit is then transformed into that unit’s output, mostly utilizing a sigmoid function. These units are connected together forming layers. Most models consist of an input layer, an output layer and

a “hidden” layer as you can see on the right side. A basic neural network. (GFDL - Anna Schroeder)

The input layer simulates the taking up of information from the outside world, the output layer simulates the response of the system and the “hidden” layer is responsible for the transformations, which are necessary to perform the computation under investigation. The units of different layers are connected via connection weights, which show the degree of influence that a unit in one level has on the unit in another one.

The most interesting and important about these models is that they are able to "learn" without being provided specific rules. This ability to “learn” can be compared to the human ability e.g. to learn the native language, because there is nobody who tells one “the rules” in order to be able to learn this one. The computational models learn by extracting the regularity of relationships with repeated exposure. This exposure occurs then via “training” in which input patterns are provided over and over again. The adjustment of “the connection weights between units” as already mentioned above is responsible for learning within the system. Learning occurs because of changes in the interrelationships between units, which occurrence is thought to be similar in the nervous system.

References

• Banich,Marie T. (2004). Cognitive Neurosciene and Neuropsychology. Housthon Mifflin Company. ISBN 0618122109

• Gazzangia, Michael S.(2000). Cognitive Neuroscience. Blackwell Publishers. ISBN 0631216596

• (1) 4 April 2001 / Accepted: 12 July 2002 / Published: 26 June 2003 Springer-Verlag 2003. Fumiko Maeda • Alvaro Pascual-Leone. Transcranial magnetic stimulation: studying motor neurophysiology of psychiatric disorders

• (2) a report by Drs Risto J Ilmoniemi and Jari Karhu Director, BioMag Laboratory, Helsinki University Central Hospital, and Managing Director, Nexstim Ltd

• (3) Repetitive Transcranial Magnetic Stimulation as Treatment of Poststroke Depression: A Preliminary Study Ricardo E. Jorge, Robert G. Robinson, Amane Tateno, Kenji Narushima, Laura Acion, David Moser, Stephan Arndt, and Eran Chemerinski

• Moates, Danny R. An Introduction to cognitive psychology. B:HRH 4229-724 0

• © 1995-2006, Healthwise, Incorporated, P.O. Box 1989, Boise, ID 83701. Author: Jan Nissl, RN, BS.

live version • discussion • edit lesson • comment • report an error