Biological Studies

Background of Caspi et al

• there is a tendency for depression to run in families - The 5-HTT gene = serotonin transporter gene, involved in reuptake of serotonin and influences the level of serotonin----- comes in two different versions, alleles, a long one and a short one - Every human individual inherits two 5-HTT (Two long, two short, or one of each)

Aim of Caspi et al

to investigate whether the short allele in combination with stressful events increases the risk of depression

Participants of Caspi et al

847 Caucasian non-Maori children from New Zealand - opportunity sampling — (originally taking part in a longitudinal study on health and development)

Procedure of Caspi et al

Gene mapping was used - 17% had two short 5-HTT alleles - 51% had one short allele - 32% had two long alleles - After 21st birthday and before 26 years: they were interviewed about 14 different kinds of stressful life events that had occurred since(included employment, financial, housing, health, and relationship stressors) - 30% had no experience of a stressful life event - 25% had experienced one - 20% had experienced two - 11% had experienced three - 15% had experienced four or more - There was no significant difference between the three genotype groups - ALSO AT 21-26: interviewed about symptoms of MDD over the last year - 17% met criteria for a major depressive episode (42% male and 58% female)

Results of Caspi et al

1) The likelihood of a depressive episode during the last year was the same for both genotypes in case there had been no stressful event during the last five years 2) The number of negative life events did not affect carriers of two LONG ALLELES 3) There was a clear correlation between numbers of stressful events and likelihood of depressive episodes among carriers of SHORT ALLELES----- these also were more likely to have thought about committing suicide or to have attempted suicide

Conclusion of Caspi et al

• there is no direct relation between short alleles on the 5HTT gene and depression----- there is a relationship between these and incidences of stress and subsequent depression- the long alleles seem to protect against suffering depression as a result of stress- the effects of the gene adaptation are dependent on environmental exposure to stress

Aim of kendler

To determine the role of genetics in major depressive disorder.

Procedure of kendler

• 15,493 twins from the Swedish national twin registry. (zygosity verified) - Telephone interviews for major depression by DSM-5. - Asked about shared environments

Results of kendler

• Correlation of lifetime majors depression and zygosity. Concordance rates. - f-f mz: 0.44 - f-f dz: 0.16 - m-m mz: 0.31 - m-m dz: 0.11 - f-m dz: 0.11 - indicate that the heritability of major depression was significantly higher in women, mz had a higher correlation.- no correlation between the number of years lived together and depression.- no differences were seen in the roles of genetic and environmental factors in major depression.- Some genetic risk factors are sex-specific.- Stong European twin studies. - Not a single gene is responsible, many play a key role and the environment too.

Wedekind Et Al AIM

To see whether human body odors and female preferences for them are dependent on a persons MHC - genes.

Wedekind Et Al PROCEDURE

49 female participants and 44 male participants were tested to identify their MHC genes. - They were then all asked to wear a shirt that was 100% cotton. - They had to wear them for 2 days straight and then the females were asked to smell the shirts on the 3rd day and rate them from 1-10 on how pleasant they were.

Wedekind Et Al RESULTS

Women preferred men with dissimilar immune systems or MHC - genes to their own.

Wedekind Et Al EVOLUTIONARY ARGUMENTS

The smell of the MHC - genes appeals to us because they are different to the ones that we have ourselves. It means that the offspring created will have a strong immune system, and thus a greater chance of survival.

Wedekind Et Al CONCLUSION

Our attraction to other people could be due to the smell of their genes and the more dissimilar the genes are to our own the more likely we are to be attracted to the scent.

Wedekind Et Al EVALUATION WEAKNESS

It was not very generalisable to a larger population size as only students were tested.

Wedekind Et Al EVALUATION STRENGTH

The experiment was well controlled, so we can be sure that it was the persons natural odor that was judged and not anything other than this.

aim of Cahill and mcgaugh

To investigate the role of adrenaline and the amygdala on emotional memory

procedure of Cahill and mcgaugh

· Participants were divided into two groups. · Each group saw 12 slides that were accompanied by a very different story.- In the first condition,- boring story - a woman and her son who paid a visit to the son's father in a hospital where they witnessed the staff in a disaster preparation drill of a simulated accident victim - In the second condition the- interesting story - the boy was involved in a car accident where his feet were severed. - He was brought to the hospital where the surgeons reattached the injured limbs.— Two weeks later, asked q based on memory (on specific details)- a recognition task - Second study- participants in the "traumatic story" condition were injected with a beta-blocker called propranolol. · Beta-blockers interfere with the release of adrenaline; in this study it was used to prevent activation of the amygdala to prevent the formation of an emotional memory.

findings of Cahill and mcgaugh

· Original experiment participants who heard the emotionally story demonstrated better recall of specific details of the story. o They could also recall more details from the slides. - In the follow-up study they found that those that had received the beta-blocker did no better than the group that had heard the "boring" story.

conclusion of Cahill and mcgaugh

· They therefore concluded that adrenaline and activation of the amygdala play a significant role in the creation of memories linked to emotional arousal.

Aim of Antanova

Investigate the effects of scolpolamine on spatial memory

Method of Antanova

Lab experiment > Double Blind and Counter Balance

Participants of Antanova

20 healthy adults > No history of psychiatric disorders

Procedure of Antanova

(1) Participants placed into either two conditions, where they were injected with * Scolpolamine * Placebo > 50 - 90 minutes before the test (2) The participants were then put under an fMRI as they play a vr game called arena tasK (3) VR Game Procedures: > The participants spawn within an area, and their task is to locate and reach a pole > Once the pole is found, the screen goes blank for 30 seconds. Where in this time, the participants will have to actively recall and memorize the location > When the 30 seconds is over, the participants spawn in a different starting point, where they have to use their spatial memory to reach to the pole (4) The participants return in another week to recieve the opposite conditions.

Results of Antanova

Participants who received the scolpolamine injection had difficulties remembering the poles location in comparison to the participants who were injected with the placebo.

Conclusion of Antanova

Scolpolamine, an antagonist for acetylcholine, impairs the role of the hippocampus in processing spatial memory

Aim of Draganski

Find out whether the human brain can change structure in response to environmental demands

Procedure of Draganski

Random sampling design, self-selected sample - Randomly allocated a sample of volunteers into 2 groups - One : jugglers - Two : non-jugglers - Made sure that both groups had no experience of juggling before the start of the experiment-First MRI performed-Participants in the juggler group subsequently spent three months learning a classic juggling routine with three balls-Second MRI performed-Participants in the juggler group spent three months where they were instructed not to practice juggling-Third MRI performed

Results of Draganski

Prior to the start of the experiment there was no difference in brain structure-Second scan the juggler had more gray matter in some areas of the cortex mostly the mid-temporal area-Third scan differences decreased but jugglers denser gray matter

Conclusion of Draganski

If we practice something then our brain will increase and when we stop practicing then it will decrease again, but often not to its original state