Biological studies Flashcards
Maguire et al. (2000)
Aim: Investigate whether structural changes could be detected in the brains of people with extensive experience in spatial navigation—specifically, London taxi drivers.
Method:
- Design: Quasi-experimental, correlational study using MRI scans.
- Participants: 16 right-handed male London taxi drivers (average experience of 14.3 years) and 50 right-handed male non-taxi driver controls.
- Procedures:
MRI scans were conducted on all participants.
Results:
- Taxi drivers had increased grey matter volume in the posterior hippocampus.
- Non-taxi drivers had increased grey matter in the anterior hippocampus.
- A positive correlation between years of taxi driving experience and hippocampal volume.
Conclusion: 1. The posterior hippocampus is involved in spatial navigation. 2. Demonstrates neuroplasticity: the brain can change structurally in response to environmental demands. 3. Supports localization of function within the hippocampus.
Draganski et al. (2004)
Aim: Determine whether structural changes occur in the brain in response to learning a new motor skill—juggling.
Method:
- Design: Experimental study with repeated measures.
- Participants: 24 volunteers (21 females, 3 males), randomly assigned to juggling or non-juggling group.
- Procedures: 1. MRI scans before learning, after mastering juggling, and three months after stopping practice. 2. Juggling group learned a three-ball cascade juggling routine.
Results:
- Increased grey matter in the mid-temporal area (visual and motor areas) after learning to juggle.
- Decrease in grey matter after cessation of practice (neural pruning).
Conclusion: 1. Learning new skills induces neuroplasticity through the formation of new neural connections. 2. Lack of practice leads to neural pruning—reduction of unused neural networks.
Antonova et al. (2011)
Aim: Investigate the role of acetylcholine in the encoding of spatial memory in humans.
Method:
- Design: Double-blind, repeated measures experimental design.
- Participants: 20 healthy male adults (mean age ~28).
- Procedures: 1. Participants randomly received either scopolamine (acetylcholine antagonist) or a placebo. 2. Engaged in a virtual reality “Arena task” to test spatial memory while undergoing fMRI scans.
Results:
- Participants injected with scopolamine showed reduced activation in the hippocampus.
- Performed worse on the spatial memory task compared to placebo group.
Conclusion: 1. Acetylcholine plays a significant role in the encoding of spatial memories in the hippocampus. 2. Blocking acetylcholine receptors impairs spatial memory formation.
POTENTIAL HARM
Martinez and Kesner (1991)
Aim: Investigate the role of acetylcholine in memory formation in rats.
Method:
- Design: Laboratory experiment with independent measures.
- Participants: Rats trained to navigate a maze.
- Procedures: 1. Divided rats into three groups: Scopolamine group (acetylcholine antagonist), Physostigmine group (acetylcholine agonist) or Control group (saline solution). 2. Measured time and errors in maze navigation.
Results:
- Scopolamine group took longer and made more errors.
- Physostigmine group learned faster and made fewer errors than control.
Control group performed at an average rate.
Conclusion: 1. Acetylcholine enhances memory formation. 2. Agonists (physostigmine) improve memory; antagonists (scopolamine) impair it.
Newcomer et al. (1999)
Aim: Examine how levels of the stress hormone cortisol affect verbal declarative memory.
Method:
- Design: Double-blind, randomized, controlled experiment.
- Participants: 51 healthy adults aged 18-30.
- Procedures: 1.Assigned to one of three groups: High cortisol dose (160 mg/day), Low cortisol dose (40 mg/day) or Placebo group. 2. Tested on verbal declarative memory over four days.
Results:
- High-dose group showed significant memory impairment.
- Low-dose group had slight but not significant impairment.
Placebo group showed no memory decline.
Conclusion: 1. Elevated cortisol levels impair verbal declarative memory. 2. Suggests stress hormones negatively impact cognitive functions.
POTENTIAL HARM
Wedekind et al. (1995)
Aim: Determine whether women prefer the body odors of men with dissimilar Major Histocompatibility Complex (MHC) genes, suggesting a role for pheromones in mate selection.
Method:
- Design: Double-blind experiment.
- Participants: 49 female and 44 male university students.
- Procedures: Men wore a plain T-shirt for two nights.
Women, during their second week after menstruation, rated the odors of six T-shirts.
Results:
- Women preferred the scent of men with dissimilar MHC genes.
- Preference reversed if women were on oral contraceptives.
Conclusion: 1. Suggests that pheromones influence human mate selection. 2. Preference for genetic diversity may enhance offspring’s immune system.
Caspi et al. (2003)
Aim: Investigate the role of the 5-HTT gene in depression following stressful life events.
Method:
- Design: Longitudinal study over 25 years.
- Participants: 847 New Zealanders.
- Procedures: 1. Genotyped participants for the 5-HTT gene (short and long alleles). 2. Assessed for depression and stressful life events.
Results:
- Individuals with one or two short alleles of the 5-HTT gene exhibited more depressive symptoms in response to stress.
- Long allele carriers less affected by stressful events.
Conclusion: 1. The 5-HTT gene moderates the influence of stressful life events on depression. 2. Demonstrates a gene-environment interaction.
Bailey and Pillard (1990)
Aim: To investigate the role of genetics in sexual orientation by comparing concordance rates of homosexuality among monozygotic (MZ) twins, dizygotic (DZ) twins, and adoptive brothers.
Method:
- Design: Correlational study.
- Participants: Male twins and adoptive brothers recruited through voluntary sampling.
- Procedure: 1. Sexual orientation was assessed through self-reports. 2. Childhood Gender Nonconformity (CGN) was also examined. 3. Participants were asked if they had relatives who were homosexual.
Results:
1. 52% of MZ twins were both self-identified as homosexual.
2. 22% of DZ twins were both homosexual.
3. 11% of adoptive brothers were both homosexual.
Conclusion:
1. The more closely genetically related a pair is, the higher the concordance rate for homosexuality, suggesting a genetic component to sexual orientation.
2. Childhood Gender Nonconformity (CGN) did not correlate with later sexual orientation, indicating it is not a predictor of homosexuality.
Fessler et al. (2005)
Aim: Investigate whether elevated levels of disgust sensitivity in the first trimester of pregnancy are an evolutionary adaptation.
Method:
- Design: Survey-based correlational study.
- Participants: 496 pregnant women aged 18-50.
- Procedure: Participants completed an online questionnaire rating their disgust sensitivity in various scenarios.
Results:
- Women in the first trimester reported higher disgust sensitivity, especially toward food-related items.
- Disgust sensitivity decreased in the second and third trimesters.
Conclusion: 1. Increased disgust during early pregnancy may protect the fetus from harmful pathogens. 2. Supports an evolutionary explanation for nausea and vomiting in pregnancy.
Bouchard et al. (1990)
Aim: To investigate the role of genetics and environment in intelligence by studying twins raised together and apart.
Method:
- Design: Correlational study.
- Participants: Monozygotic (MZ) and dizygotic (DZ) twins from around the world, including twins raised apart and together.
- Procedure: 1. Participants underwent 50 hours of psychological and physiological testing, including IQ tests. 2. Concordance rates for intelligence (IQ) were compared between groups.
Results:
1. Concordance rate for IQ in MZ twins raised together: 86%.
2. Concordance rate for IQ in MZ twins raised apart: 76%.
3. Concordance rate for IQ in DZ twins raised together: 55%.
4. Concordance rate for siblings raised together: 47%.
Conclusion:
1. Intelligence is influenced by genetic factors, as seen from the high concordance rates among MZ twins.
2. Environmental factors also play a role, as shown by the lower concordance rates in twins raised apart.
