Ways of Studying the Brain

• A post mortem is an examination of the brain after death
• 1. They study the persons behaviour whilst they are alive, strange behaviour could suggest that there is damage in the brain causing them.
• 2. When the person dies, researches examine the brain to look for abnormalities and lesions in the brain - compare it to a normal brain
• 3. Analysis of the bran allows the researcher to form a correlation between the abnormal behaviour of the person and the damage to the brain
• Post mortem allow for a deeper even of detail gathered from the brain
• A limitation for post mortem is the inability to find cause and effect
• A further limitation for post mortem is the ethical issue of informed consent
• FMRI measures blood flow whilst peforiming a task
• During a FMRI, if an area of the brain becomes more active, those neurons in the brain use the most energy an require more oxygen
• Oxygen is released for use by these active neurons at which point the haemoglobin (carries the oxygen in the blood) become deoxygenated - which has a different magnetic quality to oxygenated haemoglobin
• FMRI temporal resolution is low at 1-4 seconds
• FMRI has high spatial resolution at approximately 1-2mm
• EEGs are the measurement of the electrical activity of the brain over time
• EEGs measure electric activity of brain cells & neurons through electrodes attached to the scalp. Information is processed in the brain as electrical activity in the form of action potentials
• The EEG detects the size or intensity of electrical activity as well as the frequency or rate of electrical activity
• Electrical signals from the different electrodes are plotted on a Ralph in the form of waves - phase, beta, delta and theta
• ERPs use electrodes to measure very small voltage changes within the brain when patients are presented with a stimulus such as a picture or sound which requires cognitive processing
• Sensory ERP - waves that occur within the first 100 milliseconds after presentation of the stimulus
• Cognitve ERP are waves that occur after the first 100 miliseconds - they demonstrate some level of thinking and evaluatio
• ERPs study the brain by measuring very small voltage changes within the brain that are triggered by specific events or stimuli
• To establish a specific response to a specific event or stimulus requires many presentations of the stimulus and these responses are then averaged together
• Using a statistical averaging technique, all background brain activity from the original EEG recording is filtered out so that the response to the specific event is left
• EEG strength - good tool for diagnosing sleep disposers epilepsy and Alzheimer’s
• EEG and ERP strength - cheaper than using FMRI meaning more accessible and larger sample sizes an be used in studies
• EEGs have high temporal resolution as they take readings every millisecond
• ERPs and EEGs limitation - low spatial resolution as only detect general activity of the cerebral cortex