Biopsychology Evaluations Flashcards
Localisation of Function: Evidence from Neurosurgery
A strength of localisation theory is that damage to areas of the brain have been linked to mental disorders. Neurosurgery has been used for treating mental disorders by targeting specific areas of the brain.For example, Dougherty et al reported on 44 people with OCD who had undergone a cingulotomy. At post-surgical follow-up after 32 weeks, about 30% had met the criteria for successful response and 14% for partial response. The success of these procedures suggests that behaviours associated with serious mental disorders may be localised.
Localisation of Function: Evidence from Brain Scans
A strength of localisation theory is evidence from brain scans which support the idea that many everyday brain functions are localised. For example, Petersen et al 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. Also, Tulving et al revealed that semantic and episodic memories reside in different parts of the prefrontal cortex. These studies confirm localised areas for everyday behaviours and due to the objective methods used, provide sound scientific evidence that many brain functions are localised.
Localisation of Function: Contradictory Research Evidence
A weakness of localisation theory is that not all research evidence supports its claims. For example, Lashley removed areas of the cortex (between 10% and 50%) in rats learning the route through a maze. No area was proven to be more important than any other area in terms of the rats’ ability to learn the route. The process of learning seemed to require every part of the cortex rather than being confined to a particular area. This suggests that higher cognitive processes, such as learning, are not localised but distributed in a more holistic way in the brain.
Localisation of Function:Language Localisation Questioned
A weakness of localisation theory is that language may not be localised just to Broca’s and Wernicke’s areas. Dick and Tremblay found that only 2% of modern researchers think that language in the brain is completely controlled by these areas. Advances in brain imaging techniques mean that neural processes in the brain can be studied with more clarity. Language function seems to be distributed far more holistically in the brain than first thought. This suggests that, rather than confined to a couple of key areas, language may be organised more holistically in the brain, contradicting localisation theory.
Hemispheric Lateralisation and Split-Brain Research: Lateralisation in the Normal Brain
A strength of lateralisation theory is research showing that even in normal brains the two hemispheres process information differently. For example, Fink et al used PET scans to identify which brain areas were active during a visual processing task in ‘normal’ participants.
When asked to attend to global elements of an image (such as looking at a picture of a whole forest) regions of the RH were much more active. When required to focus on the finer detail (such as individual trees) the specific areas of the LH tended to dominate. This suggests that, at least for visual processing, hemispheric lateralisation is a feature of a normal brain as well as the split-brain.
Hemispheric Lateralisation and Split-Brain Research: One Brain
A limitation is that some aspects of lateralisation theory may be oversimplified. There may be different functions in the RH and LH, but research suggests people do not have a dominant side of their brain which creates a different personality. Nielsen et al analysed brain scans from over 1000 people and found that people used certain hemispheres for certain tasks, but there was no evidence of a dominant side, i.e. not artist’s/mathematician’s brain. This suggests that the pop-psychology notion of right- or left-brained people is incorrect.
Hemispheric Lateralisation and Split-Brain Research: Generalisation Issues
A weakness of Sperry’s research is that causal relationships are difficult to establish. The behaviour of Sperry’s split-brain participants was compared to a neurotypical control group. An issue though is that none of the participants in the control group had epilepsy. This is a major confounding variable as any observed differences between the two groups may be a result of the epilepsy rather than the split brain. In addition to this, the sample size used by Sperry was very small. This is a weakness as these issues significantly affect both the internal and external validity of the findings.
Plasticity and Functional Recovery of the Brain: Age and Plasticity
One strength of plasticity is that it does not always decline sharply with age. Plasticity reduces with age, but Bezzola et al demonstrated how 40 hours of golf training produced changes in the neural representations of movement in participants aged 40-60. Using fMRI, the researchers observed increased motor cortex activity in the novice golfers compared to a control group, suggesting more efficient neural representations after training. This demonstrates that neural plasticity can continue throughout the lifespan.
Plasticity and Functional Recovery of the Brain: Negative Plasticity
A limitation of plasticity is that it may have negative behavioural consequences. Evidence has shown that the brain’s adaptation to prolonged drug use leads to poorer cognitive functioning in later life, as well as increased risk of dementia. Also, 60-80% of amputees have been known to develop phantom limb syndrome. These sensations are usually unpleasant, painful and likely due to cortical reorganisation in the somatosensory cortex. This suggests that the brain’s ability to adapt to damage is not always beneficial.
Plasticity and Functional Recovery of the Brain: Real-World Application
A strength of functional recovery research is its real-world application. Understanding the process involved in plasticity has contributed to the field of neurorehabilitation. Simply understanding that axonal growth is possible encourages new therapies to be tried. For example, constraint-induced movement therapy is used with stroke patients whereby they repeatedly practise using the affected part of their body while the unaffected arm is restrained. This shows that research into functional recovery is useful as it helps medical professionals know when interventions need to be made.
Plasticity and Functional Recovery of the Brain: Cognitive Reserve
A limitation of functional recovery is that level of education may influence recovery rates. Schneider et al revealed that the more time people with a brain injury had spent in education, the greater their changes of a disability-free recovery (DFR). 40% of those who achieved DFR had more than 16 years education compared to about 10% of those that had less than 12 years education. This would imply that people with brain damage who have insufficient cognitive reserve are less likely to achieve a full recovery.
Circadian Rhythms: Shift Work
One strength of research into circadian rhythms is that it provides an understanding of adverse consequences that occur when disrupted. For example, night workers engaged in shift work experience a period of reduced concentration around 6am meaning mistakes and accidents are more likely. Research has also shown a relationship between shift work and poor health - shift workers are 3 times more likely to develop heart disease. This shows that research into the s/w cycle may have real-world economic implications in terms of how best to manage worker productivity.
Circadian Rhythms: Medical Treatment
A strength of research into circadian rhythms is that it has been used to improve medical treatments. Circadian rhythms co-ordinate a number of the body’s basic processes, such as heart rate and hormone levels. These rise and fall throughout the day which has led to the field of chronotherapeutics. For example, aspirin as a treatment for heart attacks is most effective if taken last thing at night. Heart attacks are most likely to occur early in the morning, so the timing of taking aspirin matters. This shows that circadian rhythms can help increase the effectiveness of drug treatments.
Circadian Rhythms: Individual Differences
A limitation of research into circadian rhythms is that generalisations are difficult to make. Many of the studies are based on small sample sizes, e.g. Siffre. S/w cycles may vary widely from person to person, e.g. Czeisler et al found evidence of s/w cycles varying from 13 to 65 hours. In addition, Duffy et al revealed that some people have a natural preference for going to bed early and rising early (‘larks’) whereas others prefer the opposite (‘owls’). This means that it is difficult to use the research data to draw conclusions, limiting the external validity.
Infradian and Ultradian Rhythms: Evolutionary Basis
A strength of research into the menstrual cycle is that it may be explained by natural selection. Syncronisation of the menstrual cycle may have evolutionary value as it may have been advantageous for female ancestors to become pregnant at the same time. This would allow babies who had lost their mothers during childbirth to have access to breast milk, thereby improving their chances of survival. This is further supported by Penton-Voak et al who suggested that mate choice varies across the menstrual cycle. Women generally prefered feminised male faces (representing kindness) when picking a partner for a long-term relationship. However, during the ovulation phase women preferred more masculine faces (representing ‘good genes’ to be passed onto offspring). These findings indicate that sexual behaviour, influenced by infradian rhythms, is an adaptive strategy.
