# Cognitive Psychology and Cognitive Neuroscience/Behavioural and Neuroscience Methods


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## Introduction

!Ct-Scan !human brain
lobes
Behavioural and
Neuroscientific methods are used to gain
insight into how the brain influences the way
individuals think, feel, and act. There are an array of methods, which
can be used to analyze the brain and its relationship to behavior.
Well-known techniques include EEG (electroencephalography) which records
the brain's electrical activity and fMRI (functional magnetic resonance
imaging) which produces detailed images of brain structure and/or
activity. Other methods, such as the lesion
method, are lesser known, but still influential in today\'s neuroscience
research.

Methods can be organized into the following categories: anatomical,
physiological, and functional. Other techniques include modulating brain
activity, analyzing behavior or computational modeling.

## Lesion method

In the lesion method, patients with brain damage are examined to
determine which brain structures are damaged and how this influences the
patient\'s behavior. Researchers attempt to correlate a specific brain
area to an observed behavior by using reported experiences and research
observations. Researchers may conclude that the loss of functionality in
a brain region causes behavioral changes or deficits in task
performance. For example, a patient with a lesion in the
parietal-temporal-occipital association area will exhibit
agraphia, a condition in which he/she is not
able to write, despite having no deficits in motor ability. If damage to
a particular brain region (structure X) is shown to correlate with a
specific change in behavior (behavior Y), researchers may deduce that
structure X has a relation to behavior Y.

In humans, lesions are most often caused by tumors or strokes. Through
current brain imaging technologies, it is possible to determine which
area was damaged during a stroke. Loss of function in the stroke victim
may then be correlated with that damaged brain area. While lesion
studies in humans have provided key insights into brain organization and
function, lesions studies in animals offer many advantages.

First, animals used in research are reared in controlled environmental
conditions that limit variability between subjects. Secondly,
researchers are able to measure task performance in the same animal,
before and after a lesion. This allows for within-subject comparison.
And third the control groups can be watched who either did not undergo
surgery or who did have surgery in another brain area. These benefits
also increase the accuracy of the hypothesis being tested which is more
difficult in human research because the before-after comparison and
control experiments drop out.

!Visualization of iron rod passing through brain of Phineas
Gage.gif "Visualization of iron rod passing through brain of Phineas Gage"){width="220"}
To strengthen conclusions regarding a brain area and task performance,
researchers may perform double
dissociation. The goal of this method
is to prove that two dissociations are independent. Through comparison
of two patients with differing brain damage and contradictory disease
patterns, researchers may localize different behaviors to each brain
area. Broca\'s area is a region of the brain
is responsible for language processing, comprehension and speech
production. Patients with a lesion in Broca\'s area will exhibit
Broca\'s aphasia or non-fluent aphasia.
These patients are unable to speak fluently; a sentence produced by a
patient with damage to the Broca\'s area may sound like: \"I \... er
\... wanted \... ah \... well \... I \... wanted to \... er \... go
surfing \... and ..er \... well\...\". On the other hand, Wernicke\'s
area is responsible for speech
comprehension. A patient with a lesion in this area has Wernicke\'s
aphasia. They may be able to produce
language, but lack the ability to produce meaningful sentences. Patients
may produce \'word salad\': \" I then did this chingo for some hours
after my dazi went through meek and been sharko\". Patients with
Wernicke\'s aphasia are often unaware of speech deficits and may believe
that they are speaking properly.

Certainly one of the famous \"lesion\" cases was that of Phineas
Gage. On 13 September 1848 Gage, a railroad
construction foreman, was using an iron rod to tamp an explosive charge
into a body of rock when premature explosion of the charge blew the rod
through his left jaw and out the top of his head. Miraculously, Gage
survived, but reportedly underwent a dramatic personality change as a
result of destruction of one or both of his frontal
lobes. The uniqueness of Gage case (and the
ethical impossibility of repeating the treatment in other patients)
makes it difficult to draw generalizations from it, but it does
illustrate the core idea behind the lesion method. Further problems stem
from the persistent distortions in published accounts of Gage---see the
Wikipedia article Phineas Gage.

## Techniques for Assessing Brain Anatomy / Physiological Function

### CAT

!X-ray picture.{width="200"}
CAT scanning was invented in 1972 by the British engineer Godfrey N.
Hounsfield and the South African (later American) physicist Alan
Cromack.

CAT (Computed Axial Tomography) is an x-ray procedure which combines
many x-ray images with the aid of a computer to generate cross-sectional
views, and when needed 3D images of the internal organs and structures
of the human body. A large donut-shaped x-ray machine takes x-ray images
at many different angles around the body. Those images are processed by
a computer to produce cross-sectional picture of the body. In each of
these pictures the body is seen as an x-ray 'slice' of the body, which
is recorded on a film. This recorded image is called a
tomogram.

CAT scans are performed to analyze, for example, the head, where
traumatic injuries (such as blood clots or skull fractures), tumors, and
infections can be identified. In the spine the bony structure of the
vertebrae can be accurately defined, as can the anatomy of the spinal
cord. CAT scans are also extremely helpful in defining body organ
anatomy, including visualizing the liver, gallbladder, pancreas, spleen,
aorta, kidneys, uterus, and ovaries. The amount of radiation a person
receives during a CAT scan is minimal. In men and non-pregnant women it
has not been shown to produce any adverse effects. However, doing a CAT
test hides some risks. If the subject or the patient is pregnant it
maybe recommended to do another type of exam to reduce the possible risk
of exposing her fetus to radiation. Also in cases of
asthma or allergies it
is recommended to avoid this type of scanning. Since the CAT scan
requires a contrast medium, there\'s a slight risk of an allergic
reaction to the contrast medium. Having certain medical conditions;
Diabetes, asthma, heart disease, kidney
problems or thyroid conditions also increases the risk of a reaction to
contrast medium.

### MRI

Although CAT scanning was a breakthrough, in many cases it was
substituted by magnetic resonance imaging (MRI), 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. !MRI head
side{width="200"} **History and
Development of MRI**

MRI is based on a physics phenomenon called nuclear magnetic resonance
(NMR), which was discovered in the 1930s by Felix Bloch (working at
Stanford University) and Edward Purcell (from Harvard University). In
this resonance, magnetic field 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 world\'s first patent issued in the
field of MRI. In 1977, Dr. Damadian 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 healthcare was available at the beginning of the
1980s. In 2002, approximately 22,000 MRI scanners were in use worldwide,
and more than 60 million MRI examinations were performed.

!A full size
MRI-Scanner.{width="250"}
**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 disease
and heart problems. The doctors can even examine the size of the
heart-chambers and determine the extent of damage caused by a heart
disease 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.

### PPT MRIII

!Reconstruction of nerve
fibers{width="220"}
There has been some further development of the MRI: The DT-MRI
(diffusion tensor magnetic resonance imaging) enables the measurement of
the restricted diffusion of water in tissue
and gives a 3-dimensional image of it. History: The principle of using a
magnetic field to measure diffusion was already described in 1965 by the
chemist Edward O. Stejskal and John E. Tanner. After the development of
the MRI, Michael Moseley introduced the principle into MR Imaging in
1984 and further fundamental work was done by Dennis LeBihan in 1985. In
1994 the engineer Peter J. Basser published optimized mathematical
models of an older diffusion-tensor model.[^1] This model is commonly
used today and supported by all new MRI-devices.

The DT-MRI technique takes advantage of the fact that the mobility of
water molecules in brain tissue is restricted by obstacles like cell
membranes. In nerve fibers mobility is only possible alongside the
axons. So measuring the diffusion gives rise to the course of the main
nerve fibers. All the data of one diffusion-tensor are too much to
process in a single image, so there are different techniques for
visualization of different aspects of this data: - Cross section
images - tractography (reconstruction of main nerve fibers) - tensor
glyphs (complete illustration of diffusion-tensor information)

The diffusion manner changes by patients with specific diseases of the
central nervous system in a characteristic way, so they can be discerned
by the diffusion-tensor technique. Diagnosis of apoplectic strokes and
medical research of diseases involving changes of the white matter, like
Alzheimer\'s disease or Multiple sclerosis are the main applications.
Disadvantages of DT-MRI are that it is far more time consuming than
ordinary MRI and produces large amounts of data, which first have to be
visualized by the different methods to be interpreted.

### fMRI

The fMRI (Functional Magnetic Resonance) Imaging is based on the Nuclear
magnetic resonance (NMR). The way this method works is the following:
All atomic nuclei with an odd number of protons have a nuclear
spin. A strong magnetic field is put around
the tested object which aligns all spins parallel or antiparallel to it.
There is a resonance to an oscillating magnetic field at a specific
frequency, which can be computed in dependence on the atom type (the
nuclei's usual spin is disturbed, which induces a voltage s (t),
afterwards they return to the equilibrium state). At this level
different tissues can be identified, but there is no information about
their location. Consequently the magnetic field's strength is gradually
changed, thereby there is a correspondence between frequency and
location and with the help of Fourier analysis we can get
one-dimensional location information. Combining several such methods as
the Fourier analysis it is possible to
get a 3D image. !fMRI
picture{width="270"}
The central idea for fMRI is to look at the areas with increased blood
flow. Hemoglobin disturbs the magnetic
imaging, so areas with an increased blood oxygen level dependant (BOLD)
can be identified. Higher BOLD signal intensities arise from decreases
in the concentration of deoxygenated haemoglobin. 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 and bad temporal resolution
since one fMRI frame is about 2 seconds long. 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 magneto encephalography (MEG), which has
much higher temporal resolution but rather poorer spatial resolution.

### PET

Positron emission tomography, also called PET 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 ray 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 disease, Parkinson\'s disease,
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.

## 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 by
electromagnetic recording methods, for example by single-cell recording
or the Electroencephalography (EEG). These methods measure the brain
activity really fast and over a longer period of time so that they can
give a really good temporal resolution.

### Single cell

When using the single-cell method an electrode is placed into a cell of
the brain on which we want to focus our attention. Now, it is possible
for the experimenter to record the electrical output of the cell that is
contacted by the exposed electrode tip. That is useful for studying the
underlying ion currents which are responsible for the cell's resting
potential. The researchers' goal is
then to determine for example, if the cell responds to sensory
information from only specific details of the world or from many
stimuli. So we could determine whether the cell is sensitive to input in
only one sensory modality or is multimodal in sensitivity. One can also
find out which properties of a stimulus make cells in those regions
fire. Furthermore we can find out if the animal's attention towards a
certain stimulus influences in the cell's respond.

Single cell studies are not very helpful 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. 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

!Placement of
electrodes{width="400"}
!EEG record during
sleep{width="250"}

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

Electroencephalogram (Electroencephalography, EEG) is obtained by
electro-electron electroencephalography, which collects weak creatures
produced by the human brain from the scalp and enlarges notes. Measuring
electroencephalogram, and EEG measures, voltage fluctuations generated
by the flow of ionic neurons in the brain. EEG is a diagnosis of a
brain-related disease, but because it is susceptible to interference, it
is usually used in combination with other methods.

EEG is most commonly used to diagnose epilepsy because epilepsy can
cause abnormal EEG readings. It is also used to diagnose sleep
disorders, coma, cerebrovascular disease, etc., and brain death. Brain
waves have been used in first-line methods to diagnose tumors, strokes,
and other focal brain diseases, but this has been reduced with the
advent of high-resolution anatomical imaging techniques, such as nuclear
magnetic resonance (MRI). And computed tomography (CT). Unlike CT and
MRI, EEGs have a higher temporal resolution. Therefore, although spatial
resolution of EEG is limited, it is still a valuable tool for research
and diagnostics, especially when determining studies that require time
resolution in the millisecond range

+----------------------+----------------------+----------------------+
| Name                 | Frequency (Hz)       | About                |
+======================+======================+======================+
| -   Delta（δ）       | -   0.1\~3 Hz        | -   Deep sleep and   |
| -   Theta（θ）       | -   4\~7Hz           |     no dreams        |
| -   Alpha（α）       | -   8\~12Hz          | -   When adults are  |
| -   Beta（β）Low     | -   12.5 \~ 16 Hz    |     under stress,    |
|     Range            | -   16.5 \~ 20 Hz    |     especially       |
| -   Beta（β) Middle  | -   20.5 \~ 28 Hz    |     disappointment   |
|     Range            | -   25 \~ 100        |     or frustration   |
| -   Beta（β) High    |     Hz（normally     | -   Relax, calm,     |
|     Range            |     40Hz）           |     close your eyes, |
| -   Gamma（γ）       | -   according to the |     but when you are |
| -   Lambda（λ）      |     power generated  |     awake            |
| -   P300             | -   according to the | -   Relax but        |
|                      |     power generated  |     concentrate      |
|                      |                      | -   Thinking,        |
|                      |                      |     dealing with     |
|                      |                      |     receiving        |
|                      |                      |     external         |
|                      |                      |     messages         |
|                      |                      |     (hearing or      |
|                      |                      |     thinking)        |
|                      |                      | -   Excitement,      |
|                      |                      |     anxiety          |
|                      |                      | -   Raise awareness, |
|                      |                      |     happiness,       |
|                      |                      |     stress           |
|                      |                      |     reduction,       |
|                      |                      |     meditation       |
|                      |                      | -   Induced by 100ms |
|                      |                      |     after the eye is |
|                      |                      |     stimulated by    |
|                      |                      |     light (also      |
|                      |                      |     known as P100)   |
|                      |                      | -   Induced after    |
|                      |                      |     seeing or        |
|                      |                      |     hearing          |
|                      |                      |     something        |
|                      |                      |     imagined in the  |
|                      |                      |     brain 300ms      |
|                      |                      |     later            |
+----------------------+----------------------+----------------------+

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.
Each electrode, also known as lead, makes a recording of its own. Next,
a reference is needed which provides a baseline, to compare this value
with each of the recording electrodes. This electrode must not cover
muscles because its contractions are induced by electrical signals.
Usually it is placed at the "mastoid bone" which is located behind the
ear.

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

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
has 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.

The disadvantage of EEG is that the electric
conductivity, and therefore the
measured electrical potentials vary widely from person to person and,
also during time. This is because all tissues (brain matter, blood,
bones etc.) have other conductivities for electrical signals. That is
why it is sometimes not clear from which exact brain-region the
electrical signal comes from.

### 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 for example 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 eats or bake for example causes a
positive potential at about 200msec. From this one can conclude, that
our brain processes these words 200 ms after presenting it. This
positive potential is followed by a negative one at about 400ms. 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 electrical 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 400 ms 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 related to electroencephalography (EEG).
However, instead of recording electrical potentials on the scalp, it
uses magnetic potentials near the scalp to index brain activity. To
locate a dipole, the magnetic field can be used, because the dipole
shows excellently the intensity of the magnetic field. By using devices
called SQUIDs (superconducting quantum interference device) one 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 are neurologically intact.

MEG has some advantages over EEG. First, magnetic fields are less
influenced than electrical currents by conduction through brain tissues,
cerebral spinal fluid, the skull and scalp. Second, the strength of the
magnetic field can 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 about 100 million times smaller than that
of the earth. Due to this, shielded rooms, made out of aluminum, are
required. This makes MEG more expensive. 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

### TMS

**History:** Transcranial magnetic stimulation (TMS) is an important
technique for modulating brain activity. 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 then with many
researchers using TMS in order to study a variety of brain functions.
Today, researchers also try to develop clinical applications of TMS,
because there are long lasting effects on the brain activity it has been
considered as a possible alternative to antidepressant medication.

**Method:** UMTS utilizes the principle of electromagnetic induction to
an isolated brain region. A wire-coil electromagnet is held upon the
fixed head of the subject. When inducing small, localized, and
reversible changes in the living brain tissue, especially the directly
under laying parts of the motor cortex can be effected. By altering the
firing-patterns of the neurons, the influenced brain area is disabled.
The repetitive TMS (rTMS) describes, as the name reveals, the
application of many short electrical stimulations with a high frequency
and is more common than TMS. The effects of this procedure last up to
weeks and the method is in most cases used in combination with measuring
methods, for example: to study the effects in detail.

**Application:** The TMS-method gives more evidence about the
functionality of certain brain areas than measuring methods on their
own. It was a very helpful method in mapping the motor cortex. For
example: While rTMS is applied to the prefrontal cortex, the patient is
not able to build up short term memory. That determines the prefrontal
cortex, to be directly involved in the process of short term memory. By
contrast measuring methods on their own, can only investigate a
correlation between the processes. Since even earlier researches were
aware that TMS could cause suppression of visual perception, speech
arrest, and paraesthesias, 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. Yet long time effects of TMS on the brain have
not been investigated properly, Therefore experiments are not yet made
in deeper brain regions like the hypothalamus or the hippocampus on
humans. 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. Here again, the methods
effects are not clear enough to use it in clinical treatments today.
Although it is too early at this point to tell whether TMS has long
lasting therapeutic effects, this tool has clearly opened up new hopes
for clinical exploration and treatment of various psychiatric
conditions. Further work in 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 behavioral
neuropsychology of various psychiatric syndromes, but also some of the
pathophysiologic circuits in the brain.

### tDCS

**transcranial Direct Current Stimulation:** The principle of tDCS is
similar to the technique of TMS. Like TMS this is a non-invasive and
painless method of stimulation. The excitability of brain regions is
modulated by the application of a weak electrical current.

**History and development:** It was first observed that electrical
current applied to the skull lead to an alleviation of pain. Scribonius
Largus, the court physician to the Roman emperor Claudius, found that
the current released by the electric ray has positive effects on
headaches. In the Middle Ages the same property of another fish, the
electrical catfish, was used to treat epilepsy. Around 1800, the
so-called galvanism (it was concerned with effects of today's
electrophysiology) came up. Scientists like Giovanni Aldini experimented
with electrical effects on the brain. A medical application of his
findings was the treatment of melancholy. During the twentieth century
among neurologists and psychiatrists electrical stimulation was a
controversial but nevertheless wide spread method for the treatment of
several kinds of mental disorders (e.g. Electroconvulsive therapy by Ugo
Cerletti).

**Mechanism:** The tDCS works by fixation of two electrodes on the
skull. About 50 percent of the direct current applied to the skull
reaches the brain. The current applied by a direct current battery
usually is around 1 to 2 mA. The modulation of activity of the brain
regions is dependent on the value of current, on the duration of
stimulation and on the direction of current flow. While the former two
mainly have an effect on the strength of modulation and its permanence
beyond the actual stimulation, the latter differentiates the modulation
itself. The direction of the current (anodic or cathodic) is defined by
the polarity and position of the electrodes. Within tDCS two distinct
ways of stimulation exist. With the anodal stimulation the anode is put
near the brain region to be stimulated and analogue for the cathodal
stimulation the cathode is placed near the target region. The effect of
the anodal stimulation is that the positive charge leads to
depolarization in the membrane potential of the applied brain regions,
whereas hyperpolarisation occurs in the case of cathodal stimulation due
to the negative charge applied. The brain activity thereby is modulated.
Anodal stimulation leads to a generally higher activity in the
stimulated brain region. This result can also be verified with MRI
scans, where an increased blood flow in the target region indicates a
successful anodal stimulation.

**Applications:** From the description of the TMS method it is should be
obvious that there are various fields of appliances. They reach from
identifying and pulling together brain regions with cognitive functions
to the treatment of mental disorders. Compared to TMS it is an advantage
of tDCS to not only is able to modulate brain activity by decreasing it
but also to have the possibility to increase the activity of a target
brain region. Therefore the method could provide an even better suitable
treatment of mental disorders such as depression. The tDCS method has
also already proven helpful for apoplectic stroke patients by advancing
the motor skills.

## Behavioural Methods

Besides using methods to measure the brain's physiology and anatomy, it
is also important to have techniques for analyzing behaviour in order to
get a better insight on cognition. Compared to the neuroscientific
methods, which concentrate on neuronal activity of the brain regions,
behavioural methods focus on overt behaviour of a test person. This can
be realized by well defined behavioural methods (e.g. eye-tracking),
test batteries (e.g. IQ-test) or measurements which are designed to
answer specific questions concerning the behaviour of humans.
Furthermore, behavioural methods are often used in combination with all
kinds of neuroscientific methods mentioned above. Whenever there is an
overt reaction on a stimulus (e.g. picture) these behavioural methods
can be useful. Another goal of a behavioural test is to examine in what
terms damage of the central nervous system influences cognitive
abilities.

### A Concept of a behavioural test

The tests are performed to give an answer to certain questions about
human behaviour. In order to find an answer to that question, a test
strategy has to be developed. First it has to be carefully considered,
how to design the test in the best way, so that the measurement results
provide an accurate answer to the initial question. How can the test be
conducted so that founding variables are minimal and the focus really is
on the problem? When an appropriate test arrangement is found, the
defining of test variables is the next part. The test is now conducted
and probably repeated until a sufficient amount of data is collected.
The next step is the evaluation of the resulting data, with the suitable
methods of statistics. If the test reveals a significant result, it
might be the case that further questions arise about neuronal activity
underlying the behaviour. Then neuroscientific methods are useful to
investigate correlating brain activities. Methods, which proved to
provide good evidence to a certain recurrent question about cognitive
abilities of subjects, can bring together in a test battery.

**Example:** Question: Does a noisy surrounding affect the ability to
solve a certain problem?

Possible test design: Expose half of the subject to a silent environment
while solving the same task as the other half in a noisy environment. In
this example founding variables might be different cognitive abilities
of the participants. Test variables could be the time needed to solve
the problem and the loudness of the noise etc. If statistical evaluation
shows significance: Probable further questions: How does noise affect
the brain activities on a neuronal level?

**Are you interested in doing a behavioural test on your own, visit:**
the socialpsychology.org website.[^2]

### Test batteries

A neuropsychological assessment utilizes test batteries that give an
overview on a person's cognitive strengths and weaknesses by analyzing
various cognitive abilities. A neuropsychological test battery is used
by a neuropsychologist to assess brain dysfunctions that can rise from
developmental, neurological or psychiatric issues. Such batteries can
appraise various mental functions and the overall intelligence of a
person.

Firstly, there are test batteries designed to assess whether a person
suffers from a brain damage or not. They generally work well in
discriminating those with brain damage from neurologically impaired
patients, but worse when it comes to discriminating them from those with
psychiatric disorders. The most popular test, **Halstead-Reitan
battery**, assesses abilities ranging from basic sensory processing to
complex reasoning. Furthermore, the Halstead-Reitan battery provides
information on the cause of the damage, the brain areas that were
harmed, and the stage the damage has reached. Such information is
valuable in developing a rehabilitation program. Another test battery,
the **Luria-Nebraska battery**, is twice as fast to administer as the
Halstead-Reitan. Its subtests are ordered according to twelve content
scales (e.g. motor functions, reading, memory etc.). These two test
batteries do not focus only on the absolute level of performance, but
look at the qualitative manner of performance as well. This allows for a
more comprehensive understanding of the cognitive impairment.

Another type of test batteries, the so-called IQ tests, aims to measure
the overall cognitive performance of an individual. The most commonly
used tests for estimating intelligence are the **Wechsler family
intelligence tests**. Age-appropriate test versions exist for small
children from age 2 years and 6 months, school-aged children, and
adults. For example, the Wechsler Intelligence Scale for Children, fifth
edition (WISC-V) measures various cognitive abilities in children
between 6 and 16 years of age. The test consists of multiple subtests
that form five different main indexes of cognitive performance. These
main constructs are verbal reasoning skills, inductive reasoning skills,
visuo-spatial processing, processing speed and working memory.
Performance is analyzed both compared to a normative sample of similarly
aged peers and within the test subject, assessing personal strengths and
weaknesses.

### The Eye Tracking Procedure

Another important procedure for analyzing behavior and cognition is
Eye-tracking. This is a procedure of measuring either where we are
looking (the point of gaze) or the motion of an eye relative to the
head. There are different techniques for measuring the movement of the
eyes and the instrument that does the tracking is called the tracker.
The first non-intrusive tracker was invented by George Buswell.

The eye tracking is a study with a long history, starting back in the
1800s. In 1879 Louis Emile Javal noticed that reading does not involve
smooth sweeping of the eye along the text but rather series of short
stops which are called fixations. This observation is one of the first
attempts to examine the eye's directions of interest. The book of Alfred
L. Yarbus which he published in 1967 after an important eye tracking
research is one of the most quoted eye tracking publications ever. The
eye tracking procedure is not that complicated. Video based eye trackers
are frequently used. A camera focuses on one or both eyes and records
the movements while the viewer looks at some stimulus. The most modern
eye trackers use contrast to locate the center of the pupil and create
corneal reflections using infrared or near-infrared non-collimated
light.

There are also two general types of eye tracking techniques. The first
one -- the Bright Pupil is an effect close to the red eye effect and it
appears when the illuminator source is onset from the optical path while
when the source is offset from the optical path, the pupil appears to be
dark (Dark Pupil). The Bright Pupil creates great contrast between the
iris and the pupil which allows tracking in light conditions from dark
to very bright but it is not effective for outdoor tracking. There are
also different eye tracking setup techniques. Some are head mounted,
some require the head to be stable, and some automatically track the
head during motion. The sampling rate of the most of them is 30 Hz. But
when we have rapid eye movement, for example during reading, the tracker
must run at 240, 350 or even 1000-1250 Hz in order to capture the
details of the movement. Eye movements are divided to fixations and
saccades. When the eye movement pauses in a certain position there is a
fixation and saccade when it moves to another position. The resulting
series of fixations and saccades is called a scan path. Interestingly
most information from the eye is received during a fixation and not
during a saccade. Fixation lasts about 200 ms during reading a text and
about 350 ms during viewing of a scene and a saccade towards new goal
takes about 200 ms. Scan paths are used in analyzing cognitive intent,
interest and salience.

Eye tracking has a wide range of application -- it is used to study a
variety of cognitive processes, mostly visual perception and language
processing. It is also used in human-computer interactions. It is also
helpful for marketing and medical research. In recent years the eye
tracking has generated a great deal of interest in the commercial
sector. The commercial eye tracking studies present a target stimulus to
consumers while a tracker is used to record the movement of the eye.
Some of the latest applications are in the field of the automotive
design. Eye tracking can analyze a driver's level of attentiveness while
driving and prevent drowsiness from causing accidents.

## Modeling Brain-Behaviour

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. !A basic
neural
network.{width="500"}
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 neuron-like
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. 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

```{=html}
<references/>
```
-   Ward, Jamie (2006) The Student\'s Guide to Cognitive Neuroscience
    New York: Psychology Press
-   Banich,Marie T. (2004). Cognitive Neurosciene and Neuropsychology.
    Housthon Mifflin Company. 
-   Gazzangia, Michael S.(2000). Cognitive Neuroscience. Blackwell
    Publishers. 
-   27.06.07
    Sparknotes.com
-   \(1\) 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


[^1]: Filler, AG: The history, development, and impact of computed
    imaging in neurological diagnosis and neurosurgery: CT, MRI, DTI:
    Nature Precedings DOI:
    10.1038/npre.2009.3267.4.

[^2]: Socialpsychology.org
