THE BRAIN AND BEHAVIOUR NON-INVASIVE TECHNIQUES

In this article I will complete the topic of the brain and behaviour in simple information.

 NON-INVASIVE TECHNIQUES

Electroencephalogram (EEG) takes electrical recordings from the scalp.  Small changes in electrical activity in the brain are picked up by electrodes.  The changes are shown on a computer screen.  The changes in patters are often known as brain waves.  EEGS are useful – they have found that we have five stages of sleep, can help to detect epilepsy, damaged brain tissue and tumours. EEGs also helped to identify the functions of the two hemispheres of the brain.  However, EEGs have largely been replaced by brain scans.

Brain Scans can study cortical functioning.  They include –

CAT scans (computerised axial tomography) – An x-ray beam goes through an individual’s head and a level of radioactivity is detected.  The level is lower when the X-ray passes through dense material.  CAT scans are useful for detecting tumours, brain abnormalities and clots.  They do not show precise locations of brain damage or show the actual functioning of the brain. They are also very expensive.

MRI scans (magnetic resonance imaging) – Produce clearer and more detailed pictures than CAT scans.  Radio waves are used to excite the atoms in the brain. These produce magnetic changes that are detected by a magnet surrounding the patient.  The changes are interpreted by a computer.  They can be used to detect very small tumours.  They can still only tell us about the structure of the brain rather than its functioning.

  Functional MRI This produces images of the brain with areas of high

   activity indicated, so we can get a picture of the brain whilst

  functioning.  This provides more spatial information than PET scans

  and shows changes over shorter periods of time.

PET scans (positron emission tomography) Shows the brain in action and also what part of the brain is active in certain tasks.  It only shows activity over a 60 second period.

Squid magnetometry (superconducting quantum interference devices) – This measures the magnetic field produced by neuron activity in the brain.  Irrelevant magnetism may interfere with results and the machine has to be kept at extremely low temperatures.

LOCALIZATION OF FUNCTION

As already mentioned, studies from split brain patients have shown that language processing occurs in the left hemisphere and emotional and spatial functioning in the right.

 Language is thought to be localised and lateralised.  Studies of split brain patients show that in normal individuals, most have language centres in the left hemisphere, but linguistic capacity appears to be in the right hemisphere.  Right-handedness is found to be due to the dominance of the right hemisphere, whilst left-handedness is thought to be partially innate.

 Boys tend to be better at right hemisphere tasks, such as visuospatial tasks, whilst girls tend to be better at languages (left hemisphere advantage).  Boys and left-handers are more likely to experience disorders such as dyslexia and autism.  Testosterone may affect left hemisphere development and impair the functioning of the immune system, which may explain why males are righter hemisphere dominant.

Emotion tends to be more dependent on the right hemisphere. Patients with damage to the right hemisphere tend to be unemotional, indifferent and less able to perceive a person’s mood or tell if they are lying. Positive emotions are thought to have more left hemisphere involvement and negative emotions right hemisphere involvement.