Biological Approach Case Studies

Maguire et al (2000)

Maguire et al (2000)

AIM: To examine whether structural changes could be detected in the brain of people with extensive experience of spatial navigation.

METHOD: Structural MRI scans were obtained. 16 right-handed male London taxi drivers participated; all had been driving for more than 1.5 years. Scans of 50 healthy right-handed males who did not drive taxis were included for comparison. The mean age did not differ between the two groups.

RESULTS:

1) Increased grey matter was found in the brains of taxi drivers compared with controls in two brain regions, the right and left hippocampi. The increased volume was found in the posterior (rear) hippocampus.

2) Changes with navigation experience – A correlation was found between the amount of time spent as a taxi driver and volume in the right posterior hippocampus.

CONCLUSION: The results provide evidence for structural differences between the hippocampi of London taxi drivers and control participants, therefore suggesting that extensive practice with spatial navigation affects the hippocampus.

Evaluation (Maguire et al 2000)

Strengths:

• Many extraneous variables are controlled:

  • The mean age was the same

  • The handedness and gender of the two groups were the same

  • The same MRI scanner was used

• However, the results only show a correlation: It is possible that people with larger than normal posterior hippocampus are attracted to careers that use their spatial abilities, including taxi driving.

  • But the fact that there was a positive correlation between the number of years spent as a taxi driver and the volume in the right posterior hippocampus would tend to counteract this argument. The researchers wee also careful to only choose brain scans from healthy non-taxi drivers as a control group.

Limitations: The MRI scans of these non-taxi drivers were obtained from a London hospital which raises ethical issues regarding informed consent and use of data. This is, as mentioned above, just a correlation, and no cause and effect relationship can be determined.

Critical Thinking (Maguire et al 2000)

Why did the posterior hippocampus change more on the right-hand side with these right-handed drivers?

This is strange, considering that the left brain hemisphere generally controls the right side of the body, so we might have expected the left hippocampus to show the most change. A follow-up comparison with left-handed drivers, with female drivers and with a larger group, is called for, as 16 people is not many on which to base a theory of localization of brain function.

Fisher, Aron and Brown (2005)

AIM: To investigate neural mechanisms associated with the attraction system.

METHOD: 10 women and 7 men between 18 and 26 years of age who reported being in love (average of 7.5 months). To determine the duration, intensity and nature of the participants’ romantic love, the researchers interviewed each participant using a semi-structured interview and the participants also completed a questionnaire - “Passionate Love Scalse (PLS)”.

• Then, they were placed in fMRI scanner where they looked at a photgraph of their beloved. After that, they were asked to countbackwards and then to take a look at photo of a neutral acquiantance. This was repeated 6 times.

RESULTS: The fMRI results showed that distinctly different parts of the brain were activated when the participants viewed photos of their beloveds versus acquiantances. When vieweing photos of their beloved, an area of the brain known as the right ventral tegmental area (VTA) was activated. This is a dopamine rich area of the brain and is part of the brain’s reward system. Clearly, there was increased activity in the dopamine rich brain areas associated with reward, motivation and goal oritentation.

CONCLUSION: The results indicate the possibility of brain circuits dedicated to attraction which happened to be the samecircuits which are associated with addiction. Dopamine increases with the anticipation of reward, perhaps we anticipate the rewards of romantic love from a partner and so our brains are wired to drive us towards attaining said rewards. It seems that the anticipation of rewards can motivate us to procreate. This is one of the evolutionary explanations of human behaviour; if we do not procreate, our genes won’t be passed on.

Evaluation (Fisher, Aron and Brown 2005)

Strengths

• The findings support previous research into the role of dopamine in substance addiction so it is interesting to see how romantic love may fall under the same framework of craving and withdrawal

  • The use of fMRI clearly shows a link between dopaminergic areas of the brain only when the photograph of the romantic partner was shown which increases the internal validity of the study i.e. Fisher really was measuring the effect of romantic love on the brain 

   Limitations

• It could be argued that a sample with a mean age of 20 years are more likely to be socially active and involved in pleasure-focused activities than an older sample which would mean that the ‘pleasure centre’ of their brains would be more receptive to dopamine

  • There could be other explanations for the activation of the dopamine-rich areas of the brain being active during the fMRI e.g. excitement at taking part in a study; curiosity as to the outcome of the study, so Fisher cannot claim cause-and-effect from her findings

Critical Thinking (Fisher, Aron and Brown 2005)

• The results of the fMRI studies are correlational and cannot establish cause and effect relationship. In this particular study, it is unclear if the dopamine affects attractions or attraction affects the production of dopamine, in other words, if the cognition influences biological response or biological factors cause the effect on cognitive processes;

• It is not clear why dopamine levels increase when we see someone we are attracted to, evolutionary explanation is not enough for a holistic explanation.

• fMRI studies focus on localization of functions and onyl examine bood flow and cannot analyze the activity of individual nerve cells, which is vital to an advanced understanding of cognitive processes such as attraction.

• Biological factors such as hormones influence our reactions to others at a much less conscious level than we are aware and according to Marazziti (2005) we are only just beginning to understand the importance of biological factors in attraction.

Luby et al (2013)

AIM: To investigate whether poverty experienced in early childhood impacts brain development at school age and to explore the mediators of this effect.

METHOD: A total of 145 right-handed children were recruited from a larger sample enrolled in a 10-year longitudinal Preschool Depression Study, to investigate the effects of poverty on brain development. Children were cognitively and socially assessed annually for three to six years before they underwent two MRI scans, one of the whole brain and one of the amygdala and hippocampal areas. The MRI scans measured the brain volumes of white matter and cortical grey matter, as well as volumes of the hippocampus and amygdala.

• During this pre-MRI period of time, they were evaluated on psychosocial, behavioural and other developmental dimensions. The support or hostility of their caregivers was also noted during this testing period. The existence of stressful life events experienced was another variable that was measured.

RESULTS: Poverty was associated with less white and grey brain matter and with smaller hippocampus and amygdala volumes. However, whether the caregiver was supportive, or hostile mediated the effects of poverty on both hippocampi, while stressful life events affected the volume of the left hippocampus only.

CONCLUSIONS: The finding that exposure to poverty in early childhood impact brain development at school age draws attention to the effects of poverty on child development. Finding that these effects on the hippocampus are mediated by caregiving and stressful life events suggest that attempts to enhance early caregiving should be focused on.

Evaluation (Luby et al)

Strength: This study extends earlier animal studies into the role of nurturing in hippocampal development and earlier child studies showing that this effect is independent of income. It gives us a complex picture of the mediating effects of stress and nurturing that needs to be investigated further. Changing economic and social status can be difficult. However, interventions at the level of caregiver support will, according to the results of this research, have a beneficial effect and may be easier to manage.

Limitations: The study sample, because of the larger sample from which it was taken, contained many pre-schoolers with symptoms of depression, limiting generalizability. The relationships in the mediation model may be bidirectional, meaning that it could be the active response of the child to the caregiver that is showing in the brain changes. This reduces the internal validity of the study.

Critical Thinking (Luby et al)

• The application of these findings is obvious in social policy, and the results of this study can be used to counteract now outdated arguments that intelligence is determined by genetic inheritance, and also to counteract arguments that state a simplistic, unidirectional and unmediated effect of poverty on the brain in childhood.

• However, what is missing is any consideration of both why some caregivers are more supportive than others and any observation of the child’s response to the type of nurturing they received. The role of supportive caregiving in preventing the negative effects on the brain of stressful life events is another variable that needs further research.

Crockett et al (2010)

BACKGROUND: Serotonin is an inhibitory neurotransmitter that is involved in sustaining stable mood and regulating sleep cycles. Effects of a neurotransmitter on mood or fatigue are believable because these are rooted in biological processes but how can a prosocial behaviour which seems to be a person’s own free will be affected by a neurotransmitter? Prosocial behaviour is a behaviour that benefits another person or has positive social consequences.

AIM: To investigate the effect of serotonin on prosocial behaviour.

METHOD: A sample of 30 healthy volunteers (mean age 26) was recruited for the study. The experimenter followed repeated measures design with two conditions.

• In the first condition the participants were given a dose of citalopram which is a highly selective serotonin reuptake inhibitor (SSRI). It blocks the reuptake of serotonin from the synapse, in this way boosting its concentration and prolonging its effects. In the second condition, which was a control group, the participants were given a placebo.

• The design was a counter-balanced and this was a double-blind study.

• After taking the drug, participants were given a series of dilemmas that involved choosing between a utilitarian outcome and aversive harmful actions. There were two scenarios of aversive harmful actions, personal and impersonal. Personal scenario included pushing a man off a bridge to stop a train and prevent it from hitting five people and impersonal include pressing a lever to divert a train off a track where it will hit five people to a track where it will hit one.

RESULTS: The response of the participants in the impersonal version were unaffected by citalopram. However, after receiving a dose of citalopram participants were less likely to push the man off the bridge in the personal scenario than the participants in the placebo condition. This implied that after receiving a dose of citalopram the participants were even more strongly opposed to the idea of pushing the man off the bridge to save five other people.

CONCLUSION: The researchers concluded that serotonin reduces acceptability of personal harm and in this way promotes prosocial behaviour. It modulates reactions of the brain to emotionally salient situations so that inflicting harm on other people is judged less credible.

Evaluation (Crockett et al 2010)

 Strengths

• The use of a double-blind procedure increases the internal validity of the findings

  • Screening the participants for psychiatric and neurological disorders before the study also increases the validity of the findings as it helps to factor out any possible confounding variables linked to mental illness 

   Limitations

• A sample of 24 participants is very small and reduces both the reliability (due to a lack of statistical power) and generalisability (again, due to the sample size) of the findings

  • The study used an independent measures design so the differences in prosocial behaviour could simply be due to participant variables e.g. participants in the SSRI group may simply all have been naturally more prosocial than those in the other two groups

Antonova et al (2011)

BACKGROUND: Scopolamine is an antagonist which blocks acetylcholine receptor sites. This decreases the availability of acetylcholine which assists in encoding of memories and learning.

AIM: To determine how blocking the acetylcholine receptors with scopolamine affects spatial memory.

METHOD: A sample of 20 healthy male adults, with a mean age of 28 years was used. The study used a double-blind procedure and participants were randomly allocated to one of two conditions. They were injected with either scopolamine or a placebo.

The participants were then put into an fMRI scanner where they were scanned while playing an “Arena task.” The goal is for the participants to navigate around an “arena” with the goal of reaching a pole. After they have learned where the pole is located, the screen would go blank for 30 seconds. During this time, the participants were told to actively rehearse how to get o the pole. When the a arena appeared, the participants would have to use their spatial memory to determine how to get to the location of the pole from the starting point. The participants’ brain activity was measured for 6 trials.

The participants returned between 3-4 weeks later and redid the test - receiving the opposite treatment to the original study.

RESULTS: The researchers found that when participants were injected with scopolamine, they demonstrated a significant reduction in the activation of the hippocampus compared to when they received a placebo. This suggests that scopolamine impairs memorization of new information by decreasing spoking activity within the hippocampus.

CONCLUSION: It appears that acetylcholine could play a key role in the encoding of spatial memories in humans and that the antagonist, scopolamine impairs memorization of new information by decreasing spiking activity within the hippocampus.

Devis et al (1978)

BACKGROUND: In humans the anticholinergic agent scopalamine