AQA Psychology for A Level Year 2 - Student Bk

F R O N T A L L O B E T E M P O R A L L O B E P A R I E T A L L O B E OCCIPITAL LOBE Concepts: The curious case of Phineas Gage Whilst working on the railroad in 1848, 25-year-old Phineas Gage was preparing to blast a section of rock with explosives to create a new railway line. During the process, Gage dropped his tamping iron onto the rock causing the explosive to ignite. The explosion hurled the metre- length pole through Gage’s left cheek, passing behind his left eye, and exiting his skull from the top of his head taking a portion of his brain with it – most of his left frontal lobe. Incredibly, Gage survived but the damage to his brain had left a mark on his personality – by all accounts he had turned from someone who was calm and reserved to someone who was quick-tempered, rude and ‘no longer Gage’. Gage is seen as a landmark case in science as the change in his temperament following the accident suggests that the frontal lobe may be responsible for regulating mood. Questions 1. Does the case of Phineas Gage support localisation theory or holistic theory? Why? 2. Why is it difficult to draw general conclusions from the case of Gage? @ookx hs Concepts: Label the brain Use the information on the facing page to help you label the areas of the brain. @ookx hs @ookx hs Evaluation Brain scan evidence of localisation There is a wealth of evidence providing support for the idea that many neurological functions are localised, particularly in relation to language and memory. For instance, Petersen et al . (1988) used brain scans to demonstrate how Wernicke’s area was active during a listening task and Broca’s area was active during a reading task, suggesting that these areas of the brain have different functions. Similarly, a study of long-term memory by Tulving et al. (1994) revealed that semantic and episodic memories reside in different parts of the prefrontal cortex. There now exists a number of highly sophisticated and objective methods for measuring activity in the brain (see page 44) which provide sound scientific evidence of localisation of brain function. Neurosurgical evidence The practice of surgically removing or destroying areas of the brain to control aspects of behaviour developed in the 1950s. Early attempts, such as those pioneered by Walter Freeman who developed the lobotomy , were brutal and imprecise and typically involved severing connections in the frontal lobe in an attempt to control aggressive behaviour. Controversially, neurosurgery is still used today, albeit sparingly, in extreme cases of obsessive-compulsive disorder and depression . For example, Dougherty et al . (2002) reported on 44 OCD patients who had undergone a cingulotomy – a neurosurgical procedure that involves lesioning of the cingulate gyrus. At post-surgical follow-up after 32 weeks, a third had met the criteria for successful response to the surgery and 14 percent for partial response. The success of procedures like this strongly suggests that symptoms and behaviours associated with serious mental disorders are localised. Case study evidence Unique cases of neurological damage support localisation theory such as the case of Phineas Gage (see right). Lashley’s research The work of Karl Lashley (1950) suggests that higher cognitive functions, such as the processes involved in learning, are not localised but distributed in a more holistic way in the brain. Lashley removed areas of the cortex (between 10 and 50%) in rats that were learning a maze. No area was proven to be more important than any other area in terms of the rats’ ability to learn the maze. The process of learning appeared to require every part of the cortex, rather than being confined to a particular area. This seems to suggest that learning is too complex to be localised and requires the involvement of the whole of the brain. Consider: Lashley’s work was conducted using animals (rats). Explain why this means we should be cautious in drawing conclusions related to human learning. Plasticity A further and compelling argument against localisation of function is the notion of cortical remapping or plasticity (see next spread). When the brain has become damaged, say through illness or accident, and a particular function has been compromised or lost, the rest of the brain appears able to reorganise itself in an attempt to recover the lost function. Lashley described this as the law of equipotentiality whereby surviving brain circuits ‘chip in’ so the same neurological action can be achieved. Although this does not happen every time, there are several documented cases of stroke victims being able to recover those abilities that were seemingly lost as a result of the illness. Consider: Explain how the apparent plasticity of the brain lends support to holistic, rather than localisation, theory. Evaluation e X tra 1. Using an example, explain what is meant localisation of function . [3 marks] 2. Describe one study in which localisation of brain function was investigated. Include details of what the psychologists did and what was found. [3 marks] 3. State the location in the brain of each of the following: (i) The motor area (ii) The visual area (iii) The auditory area. [3 marks] 4. Discuss the extent to which brain functions are localised. Refer to evidence in your answer. [16 marks] Check It Labels: Auditory area Broca’s area Motor area Somatosensory area Visual area Wernicke’s area Localisation of function in the brain 39 •