Biological Case Studies AMRCs

Aim: To investigate the role of acetylcholine in spatial memory formation.
Method: 20 male participants played a virtual reality (VR) maze task twice, once after receiving scopolamine (which blocks acetylcholine) and once after receiving a placebo. Their brain activity was measured using fMRI.
Results: Participants who received scopolamine had reduced activity in the hippocampus and performed worse in navigation tasks.
Conclusion: Acetylcholine plays a crucial role in spatial memory and learning, supporting the idea that neurotransmitters influence cognition.

Aim: To examine whether the 5-HTT gene (serotonin transporter gene) affects vulnerability to depression following stressful life events.
Method: Longitudinal study of 847 participants divided into groups based on the length of their 5-HTT alleles (short/short, short/long, long/long). Participants self-reported stressful life events and symptoms of depression.
Results: Individuals with at least one short allele were more likely to develop depression after stressful events than those with two long alleles.
Conclusion: The 5-HTT gene moderates the influence of stress on depression risk, demonstrating a gene-environment interaction.

Aim: To investigate whether extensive spatial navigation experience affects hippocampal structure in London taxi drivers.
Method: MRI scans of 16 taxi drivers were compared to those of 50 control participants. The hippocampal volume was measured.
Results: Taxi drivers had significantly larger posterior hippocampi but smaller anterior hippocampi compared to controls.
Conclusion: The study supports neuroplasticity, showing that the hippocampus changes in response to extensive spatial navigation experience.

Aim: To examine whether learning a new skill (juggling) induces structural changes in the brain.
Method: Participants had MRI scans before learning to juggle, after three months of practice, and three months after stopping practice.
Results: Increased gray matter was found in the mid-temporal area after learning but decreased once they stopped practicing.
Conclusion: Learning new skills can cause temporary structural changes in the brain, supporting neuroplasticity.

Aim: To understand the role of the hippocampus in memory formation by studying patient HM, who had it removed to treat epilepsy.
Method: Milner conducted memory tests, cognitive tasks, and MRI scans on HM.
Results: HM could not form new explicit memories (anterograde amnesia) but retained procedural memory (e.g., improving at tasks without remembering learning them).
Conclusion: The hippocampus is essential for forming new explicit (declarative) memories but not for procedural memory.

Aim: To investigate the effects of cortisol (a stress hormone) on verbal memory.
Method: Participants were divided into high cortisol, low cortisol, and placebo groups. They were asked to recall a prose passage over several days.
Results: The high cortisol group performed the worst in verbal memory recall.
Conclusion: Chronic stress and elevated cortisol levels negatively affect memory function.

Aim: To examine the relationship between testosterone levels and aggression in male prisoners.
Method: Measured testosterone levels in saliva samples of 692 male inmates and compared them to their criminal records.
Results: Higher testosterone levels were associated with violent crimes and aggressive behavior.
Conclusion: Testosterone is linked to aggression, supporting a biological explanation of aggressive behavior.

Aim: To investigate the effects of androstadienone (a putative human pheromone) on mood and attraction in women.
Method: Female participants were exposed to androstadienone in the presence of either a male or female experimenter. Their mood and attraction levels were recorded.
Results: Women reported feeling more positive in the presence of a male experimenter but not a female.
Conclusion: Androstadienone may influence mood and social perception, supporting the idea of human pheromones affecting behavior.

Aim: To investigate whether androstadienone and estratetraenol (putative pheromones) influence mate perception.
Method: Participants were exposed to these chemicals and then completed facial attractiveness and gender perception tasks.
Results: No significant effect on attraction or gender perception was found.
Conclusion: The study does not support the idea that these chemicals function as human pheromones affecting attraction.

Aim: To examine if pregnancy-related nausea (morning sickness) is an adaptive mechanism for avoiding harmful foods.
Method: Surveyed 496 pregnant women about their disgust sensitivity toward various stimuli.
Results: Women in their first trimester showed the highest disgust sensitivity, particularly toward food-related images.
Conclusion: Disgust in early pregnancy likely evolved as a protective mechanism to prevent consumption of harmful substances.

Aim: To test whether disgust is an evolved response to disease threats.
Method: An online survey asked participants to rate disgust levels for 20 images (some showing disease threats, others not).
Results: Disease-related images were rated as more disgusting, with women showing stronger disgust responses.
Conclusion: Disgust evolved as a survival mechanism to prevent exposure to pathogens.

Aim: To determine the heritability of depression using twin studies.
Method: Studied 42,000 twins from the Swedish Twin Registry and compared depression rates in monozygotic (MZ) and dizygotic (DZ) twins.
Results: MZ twins had a higher concordance rate for depression (44%) than DZ twins (17%).
Conclusion: Depression has a strong genetic component but is also influenced by environmental factors.

Aim: To investigate the genetic transmission of depression across three generations.
Method: Longitudinal study of families with a history of major depressive disorder. The mental health of children, parents, and grandparents was assessed.
Results: Grandchildren with depressed grandparents had higher rates of psychiatric disorders, even if their parents were not depressed.
Conclusion: Depression can be transmitted genetically across generations, supporting a hereditary component.

Aim: To examine the interaction between the MAOA gene and childhood maltreatment in predicting aggressive behavior.
Method: Followed a cohort of males from childhood to adulthood, assessing childhood maltreatment, MAOA gene variations, and aggressive behavior.
Results: Males with the low-activity MAOA gene and childhood maltreatment were more likely to exhibit aggressive behavior.
Conclusion: The MAOA gene interacts with environmental factors to influence aggression, demonstrating gene-environment interaction.