Ways Of Studying The Brain

What are techniques for investigating the brain often used for?

For medical purposes in the diagnosis of illness. The purpose of scanning in psychological research is often to determine which parts of the brain do what.

What are the four ways of studying the brain?

• Functional magnetic resonance imaging (fMRI).

• Electroencephalogram (EEG).

• Event-related potentials.

• Post-mortem examinations.

What is a fMRI used to do?

Measure brain activity while a person is performing a task.

How does a fMRI work?

By detecting the changes in both blood oxygenation and flow that occur as a result of neural activity in specific parts of the brain.

When a brain area is more active, what happens?

It consumes more oxygen and to meet this increased demand, blood flow is directed to the active are (the haemodynamic response).

What does an fMRI produce?

3D images (activation maps) showing which parts of the brain are involved in a particular mental process and this has important implications in understanding localisation of function.

What is an EEG?

A record of the tiny electrical impulses produced by the brain’s activity.

How does an EEG work?

IT measures electrical activity within the brain via electrodes that are fixed to an individual’s scalp using a skull cap. The scan recording represents the brainwave patterns that are generated by the action of thousands of neurons, providing an overall account of brain activity.

Who are EEGs often used by?

Clinicians as a diagnostic tool as arrhythmic patterns of activity may indicate neurological abnormalities.

Although EEG has many scientific and clinical applications, in its raw form, what is it?

A crude and overly general measure of brain activity. However, within EEG data are contained all the neural responses associated with specific sensory, cognitive and motor events that may be of interest to cognitive neuroscientists. As such, researchers have developed a way of teasing out and isolating these responses.

Using a statistical averaging technique, what are researchers able to do?

All extraneous brain activity from the original EEG recording is filtered out leaving only those responses that relate to the presentation of a specific stimulus or performance of a specific task.

What remains after extraneous brain activity from an EEG is filtered out?

Event related potentials, types of brainwave that are triggered by particular events.

What is a post-mortem examination?

A technique involving the analysis of a person’s brain following their death.

In psychology, who are the individuals whose brains are subject to a post-mortem study?

It is likely to be those who have a rare disorder and have experienced unusual deficits in cognitive processes or behaviour during their time.

What are areas of damage within the brain examined after death as a means of?

Establishing the likely cause of the affliction the person experienced. This may also involve comparison with a neurotypical brain in order to ascertain the extent of the difference.

What is one key strength of fMRI?

Unlike other scanning techniques, it does not rely on the use of radiation. If administered correctly, it is virtually risk-free, non-invasive and straightforward to use. It also produces images that have very high spacial resolution, depicting detail by the millimetre, and providing a clear picture of how brain activity is localised.

What does fMRI being radiation free, non-invasive and detailed mean?

That fMRI can safely provide a clear picture of brain activity.

What is the limitation of fMRIs?

IT is expensive compared to other neuroimaging techniques. It has poor temporal resolution because there is around a 5-secind time lag behind the image on the screen and the initial firing of neuronal activity.

What does the cost and temporal resolution of fMRIs mean?

That they might not truly represent moment-to-moment brain activity.

What are the strengths of EEG’s?

EEG has been useful in studying the stages of sleep and in the diagnosis of conditions such as epilepsy. Unlike fMRI, EEG technology has extremely high temporal resolution. Today’s EEG technology can accurately detect brain activity at a resolution of a single millisecond, and even less in some cases.

What does the application and temporal resolution of EEGs show?

The real-world usefulness of the technique.

What are the limitations of EEG’s?

The main drawback of EEG lies in the generalised nature of the information received (that of many thousands of neurons). The EEG signal is also not useful for pinpointing the exact source of neural activity.

What does the generalised nature of EEG’s mean for the technique?

That it does not allow researchers to distinguish between activities originating in different but adjacent locations.

What are the strengths of event-related potentials?

The limitations of EEG are partly addressed through the use of ERPs. These bring much more specificity to the measurement of neural processes than could ever be achieved using EEG data. As ERPs are derived from EEG measurements, they have excellent temporal resolution, especially. when compared to fMRI.

What does the specificity of Event related potentials mean?

That they are frequently used to measure cognitive functions and deficits such as the maintenance of working memory.

What are the limitations of event-related potentials?

Critics have pointed to a lack of standardisation in ERP methodology between different research studies which makes if difficult to confirm findings. A further issue is that, in order to establish pure data in ERP studies, background ‘‘noise' and extraneous material must be completely eliminated. This is a problem because it is not always easy to achieve.

What are the strengths of post-mortem examinations?

Post-mortem evidence was vital in providing a foundation for early understanding of key processes in the brain. Broca and Karl Wernicke both relied on post-mortem studies in establishing links between language, brain and behaviour decades before neuroimaging ever became a possibility. Post-mortem studies were also used to study HM's brain to identify the areas of damage, which could then be associated with his memory deficits.

What do the strengths of post-mortem examinations mean?

This means post-mortems continue to provide useful information.

What are the limitations of post-mortem examinations?

Causation is an issue within these studies, however. Observed damage to the brain may not be linked to the deficits under review but to some other unrelated trauma or decay. A further problem is that postmortem studies raise ethical issues of consent from the individual before death. Participants may not be able to provide informed consent, for example in the case of HM who lost his ability to form memories and was not able to provide such consent - nevertheless post-mortem research has been conducted on his brain.

What do the limitations of post-mortem examinations challenge?

The usefulness of post-mortem studies in psychological research.