Ways of Studying the Brain (ERP and Post-mortem)

Event-related potential

• ERPs are small voltage changes in the brain that are triggered by specific events or stimuli. e.g. cognitive processing of a specific stimulus • ERPs are difficult to pick out from other electrical activity being generated within the brain at a given time

• Stimulus is usually presented hundreds of times as it’s difficult to isolate the activity • Any extraneous neural activity that isn’t related to the stimulus will not occur consistently, but the activity linked to the stimulus will, making the specific response to the stimulus clearer.

• Waves occurring within 100ms after presentation of stimulus are termed ‘sensory’ ERPs as they show an initial response to physical characteristics of stimulus. • ERPs generated after 100ms reflect how the subject evaluates the stimulus and termed ‘cognitive’ ERPs as they show information processing

Interval between presentation of stimulus and response

• Can monitor the processing of stimuli without a behavioural response. ERPs recordings can monitor ‘covertly’ the processing of a particular stimulus without requiring the person to respond to them • As ERPs provide a continuous measure of processing in response to a particular stimulus, it determines how processing is affected by a specific experimental manipulation, e.g. during presentation of different visual stimuli • Shows activity every millisecond, recording in nearly real time (great temporal resolution)

• Studies using ERPs have been critcised for a lack of standardisation in method • As ERPs are so small, it’s difficult to pick up other electrical activity in the brain. It requires a large number of trials to gain meaningful data. This limits the types of questions that ERP readings can answer • Only strong voltage change is recordable. Important electrical activities deep in the brain aren’t recorded, meaning the generation of ERPs tends to be restricted to the neocortex

• To establish the underlying biology of a particular behaviour • e.g. researchers may study a person who displays a certain behaviour while they’re alive that suggests possible brain damage

When a person dies, researchers can study the physical brain to look for abnormalities that might explain behaviour.

Broca’s patient (Tan) had a speech problem and was found to have a lesion in the posterior left frontal lobe in a post-mortem examination

• Iverson found higher levels of dopamine in deceased schizophrenics brains compared to non-schizophrenic • These allow detailed study of neurochemical and neuroanatomical aspects of the brain

• Allows for a detailed examination as it enables researchers to examine deeper regions of the brain like the hypothalamus and hippocampus. • Harrison claims post-mortem has played a central part in understanding the origins of schizophrenia. He suggests that due to post-mortem, researchers have discovered structural abnormalities of the brain

• There are confounding variables. People die in various ways, at various stages of disease. Similarly, the length of time between death and post-mortem, drug treatments and age at death can influence the post-mortem brain • It’s limited as it’s retrospective because the person is already dead. As a result, the researcher can’t follow up on anything that rises from the post-mortem concerning a relationship between brain abnormalities and cognitive functioning