AQA Psychology for A Level Year 2 - Student Bk

1. Outline one difference between EEGs and ERPs as ways of investigating the brain. [2 marks] 2. Briefly evaluate post-mortem examinations as a way of investigating the brain. [4 marks] 3. Describe and evaluate scanning techniques as a way of investigating the brain. [16 marks] Check It Methods: Memory lane A researcher used an fMRI scan to investigate whether different types of long-term memories are located in different parts of the brain. Participants were asked to think about family holidays they had been on as a child and their brain activity was recorded. The same participants were then asked to mentally ‘list’ European capital cities and their brain activity was again recorded to see if there was a difference. Question The investigation described above could be considered to be a lab experiment . Briefly discuss strengths and limitations of lab experiments with reference to the investigation above. ( 6 marks ) @ookx hs @ookx hs Evaluation Functional magnetic resonance imaging Strengths – One key strength of fMRI is, unlike other scanning techniques such as PET , 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 spatial resolution, depicting detail by the millimetre, and providing a clear picture of how brain activity is localised. Weaknesses – fMRI is expensive compared to other neuroimaging techniques and can only capture a clear image if the person stays perfectly still. It has poor temporal resolution because there is around a 5-second time-lag behind the image on screen and the initial firing of neuronal activity. Finally, fMRI can only measure blood flow in the brain, it cannot home in on the activity of individual neurons and so it can be difficult to tell exactly what kind of brain activity is being represented on screen. Electroencephalogram Strengths – EEG has proved invaluable in the diagnosis of conditions such as epilepsy, a disorder characterised by random bursts of activity in the brain that can easily be detected on screen. Similarly, it has contributed much to our understanding of the stages involved in sleep (see research into ultradian rhythms – page 48). 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). Weakness – The main drawback of EEG lies in the generalised nature of the information received (that of many thousands of neurons). The EEG signal is not useful for pinpointing the exact source of neural activity, and it does not allow researchers to distinguish between activities originating in different but adjacent locations. Event-related potentials Strengths – 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 raw EEG data. As ERPs are derived from EEG measurements, they have excellent temporal resolution, especially when compared to neuroimaging techniques such as fMRI, and this has led to their widespread use in the measurement of cognitive functions and deficits. Researchers have been able to identify many different types of ERP and describe the precise role of these in cognitive functioning; for instance, the P300 component is thought to be involved in the allocation of attentional resources and the maintenance of working memory . Weaknesses – Critics have pointed to a lack of standardisation in ERP methodology between different research studies which makes it 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, and this may not always be easy to achieve. Post-mortems Strengths – Post-mortem evidence was vital in providing a foundation for early understanding of key processes in the brain. Paul Broca and Karl Wernicke (see page 38) both relied on post-mortem studies in establishing links between language, brain and behaviour decades before neuroimaging ever became a possibility. Post-mortem studies improve medical knowledge and help generate hypotheses for further study. Weaknesses – Causation is an issue within these investigations, 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 post-mortem studies raise ethical issues of consent from the patient before death. Patients 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. Concepts: FMRI and lie detection One innovative and recently emerging application of fMRI has been in the field of lie detection. Many have claimed that fMRI is an ideal tool for detecting truthfulness (or more pertinently, the lack of it) due to its ability to effectively see inside the brain. Supporters of its use argue that the analysis of neural blood flow is preferable to tracking peripheral measures of anxiety — such as changes in pulse, skin temperature or respiration – that would be recorded by more traditional lie detectors or polygraphs (such as those employed by police detectives or on daytime talk shows). Traditional lie detectors are widely acknowledged as ‘beatable’, but neural activity is much more difficult to fake! Two US companies, Cephos (in Pepperell, Massachusetts) and the catchily-named No Lie MRI (in Tarzana, California), claim to predict with over 90 percent accuracy whether its clients are ‘spinning a line’. No Lie MRI suggests that the technique may even be used for ‘risk reduction in dating’. Many neuroscientists and legal scholars doubt such claims – and some even question whether brain scans for lie detection will ever move beyond the research lab into the real world. Question What are the strengths and limitations of using fMRI as a method of lie detection? @ookx hs Will neuroimaging techniques such as fMRI ever replace the traditional polygraph on entertainment programmes such as the Jeremy Kyle Show? Ways of investigating the brain 45 •