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Brain and behavior, Caspi et al 2003 (Correlation study), Genetics and…

- - - - The study used a pre-test/post-test design to show differences in neural density over time.
      - The study was experimental, thus helping to argue for a cause-and-effect relationship.
      - There was a group that didn't juggle and served as a control.
      - The sample size was very small - so it is possible that by using averages of neural growth, the data may not be reliable.
      - The study was a field experiment - that is, the IV was manipulated under natural conditions; therefore, the study has potential problems with internal validity as the participants were in their home environments for a good part of the study.
- - - - The researchers used a sample of twenty healthy male adults, with a mean age of 28 years old. 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 70 - 90 minutes before taking part in the experimental task.
      - The participants were then put into an fMRI where they were scanned while playing the "Arena task." This is a rather complex virtual reality game in which the researchers are observing how well the participants can create spatial memories. The goal is for the participants to navigate around an "arena" to reach 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 to the pole in the arena. When the arena reappeared, the participant was now at a new starting point in the arena. The participants would have to use their spatial memory to determine how to get to the location of the pole.
      - The participants were first trained in the game to make sure that they were comfortable with the use of the joystick and that they understood the rules of the game. After they were trained, they then took part in the experiment. The participants' brain activity was measured for six trials.
      - The participants returned between 3 - 4 weeks later and redid the test - receiving the opposite treatment to the original study. In other words, the study was a repeated measures design.
      - 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. It appears that acetylcholine could play a key role in the encoding of spatial memories in humans, as well as in rats.
    - - Although there was a higher rate of error in the scopolamine group, it was not a significant difference. The difference in the activity in the hippocampus, however, is significant. This means that the task as designed may not have been the best for showing performance differences; without the use of the fMRI, there would be no way to know that at the biological level, there were significant differences in the two conditions.
      - The study was a repeated measures design - eliminating the effect of participant variability. In addition, the study was counter-balanced - that is, some of the participants did the scopolamine condition first, and others did the placebo condition first. This controlled for practice effect.
      - The study was carried out blindly; this controls for researcher bias.
      - During the debriefing, several of the participants expressed that they had felt stressed, either as a result of the injection of an unfamiliar drug or being in the fMRI enclosure. This could affect the working of the hippocampus as we know that stress may interfere with memory encoding.
      - The sample size was small. The results would need to be replicated to decide whether the results are reliable.
  - - - Prevot et al. (2019) hypothesized that using an agonist (an imidazobenzodiazepine) that activates the α5-GABA receptor sites in the hippocampus would increase the inhibition of neural activity, which would then lead to improved memory function. The researchers used a sample of mice that suffered from memory impairment as a result of chronic stress and older mice that demonstrated memory impairment.
      - Mice were placed alone in a Y-shaped maze, a task used to test spatial working memory. Mice with healthy working memory can alternate between the two arms of the "Y" when continually placed back at the start of the maze. Mice with impaired working memory are more likely to explore the same arm of the "Y" that they just explored, and they tend to wander aimlessly in the maze.
      - The researchers carried out a double-blind experiment with a pre-test/post-test design. The mice were allocated to either the placebo condition (the control condition) or the drug condition. The results for both the chronic stress and aged mouse samples are below.
      - This graph shows that the drug treatment group performed almost as well as the mice that had not been chronically stressed.
      - As you can see in the previous graph, older mice treated with the drug performed significantly better on the task than those that received the placebo. In both cases, there was an improvement in spatial working memory in the mice that were given the GABA agonist. After the study, the mice were sacrificed. The researchers found that the mice with the drug treatment showed new hippocampal cell growth, reversing the effects of stress and aging.
    - - The researchers used an experimental design with both a healthy control and a placebo group to establish a cause-and-effect relationship. The experiment was done blindly to control for researcher bias.
      - Although the study is very recent, it is based on established theory—that is, a body of research that has similar results and is based on assumptions about the role of GABA in memory. For example, this study confirms some of the findings of Koh et al. (2017). It also may confirm the role of GABA in dementia, as seen in the study by Porges (2017).
      - The study uses an animal model. Despite the similarities in the role of GABA in memory in humans, we can only cautiously generalize to humans. The drug will have to undergo human testing to determine if the findings are generalizable to a human sample.
      - Ethical considerations are essential in this study as mice are sacrificed as part of the study.
  - - - The aim of the study was to determine the role of acetylcholine in the formation of spatial memory.
      - Rogers & Kesner wanted to determine the role of acetylcholine in memory formation and retrieval. They had 30 rats acclimate to a Hebb-Williams maze by placing food in one of the corners. Once the rats were familiar with the maze - and no longer were afraid of the environment - the experiment could begin.
      - The rats were randomly allocated to one of two conditions. The rats were either injected with scopolamine or with a saline solution ten minutes before running the maze. Scopolamine blocks the acetylcholine receptor sites and thus inhibits any response. The saline solution was a placebo injection. This was done to make sure that the fact of getting an injection alone was not responsible for a change in memory. An injection could result in an increase in adrenaline which would be a confounding variable. The injections were made directly into the hippocampus.
      - Encoding of memory was assessed by the average number of errors made on the first five trials of Day 1 compared to the last five trials of Day 1, whereas the average number of errors made on the first five trials of Day 2 compared to the last five trials of Day 1 was used to assess retrieval.
      - The findings were that the scopolamine group took longer and made more mistakes in the learning of the maze - that is, there was a higher average number of mistakes made on the last five trials on Day 1. However, it did not appear to affect the retrieval of memories that had already been created. It appears that acetylcholine may play an important role in the consolidation of spatial memories.
    - - The researchers used a rigorously controlled experiment with a placebo condition to avoid the effect of confounding (extraneous) variables.
      - The study can establish a cause-and-effect relationship; however, it is a reductionist approach to understanding memory. There are several different types of memory and the process of memory consolidation is very complex.
      - The research could one day lead to the development of treatments for people suffering from dementia or Alzheimer's disease.
      - Biologists believe that animals can serve as models for human physiology and behavior; however, there are questions about the extent to which findings can be generalized to humans.
  - - - Aim: To investigate the effect of serotonin levels on activation of PFC and amygdala
      - Type of Experiment:
        True Experiment
      - Participants: Healthy volunteers (Volunteer Sampling)
      - Experimental Design: Repeated Measures
      - Conditions
        
        Day 1: Drink that lacked tryptophan
        
        Day 2: Placebo
      - Technique Used: fMRI
      - Procedure
        
        In fMRI while looking at faces:
        
        1) Happy
        
        2) Angry
        
        3) Neutral
      - Results
        
        Low tryptophan + angry faces
        
        1) Reduced activity in PFC
        
        2) Reduced communication between amygdala and PFC
      - Conclusion: In ability to regulate impulsive decisions and the flight-fight responses.
    - - Strengths
        
        Double-blind procedure: researchers and the participants did not know who got the altered drink or the placebo.
        
        Reduces research bias
      - Limitations
        
        1) Ecological validity
        
        2) Operationalized definition
- - - - The study is correlational and does not establish a cause-and-effect relationship.
      - The environment of the fMRI and the task that the participants are asked to do is highly artificial - and thus low in ecological validity. However, because of the nature of the task, demand characteristics are not possible.
      - Although the study demonstrates the role of the amygdala as a result of proximity to the event, it does not explain why some people have vivid memories after seeing the events on television or the Internet.
      - The sample size is small and culturally biased. Research indicates that individualistic cultures are more likely to have flashbulb memories than collectivistic cultures. This makes the findings difficult to generalize.
  - - - Psychometric testing: IQ testing was given to HM. His results were slightly above average with an IQ of 104 before the operation and a slightly improved IQ of 112 after the operation due to the reduction in seizures.
      - Direct observation of his behavior;
      - Interviews with both HM and his family members.
      - Cognitive testing: memory recall tests as well as learning tasks - such as reverse mirror drawing.
      - Corkin (1997) later did an MRI to determine the extent of the damage done to HM's brain.
- - - - Zhou et al (2014) carried out a study to see if AND or EST influences human mating behavior. The sample was made up of 96 participants – 24 heterosexual men, 24 heterosexual women, 24 gay men, and 24 lesbian women.
      - In the experiment, participants were asked to watch stick figures walking on a screen and to determine their gender. While carrying out the task, the participants were exposed to the smell of cloves. In the first condition, the cloves were mixed with androstadienone; in the second condition, the cloves were mixed with estratetraenol; and in the control condition, only cloves were used.
      - The findings showed that smelling androstadienone biased heterosexual females and gay males, but not heterosexual males or lesbian women, toward perceiving the walkers as more masculine. By contrast, smelling estratetraenol systematically biases heterosexual males and, to some extent, lesbian women toward perceiving the walkers as more feminine. The researchers concluded that pheromones influence the communication of gender information in a sex-specific manner.
      - Although the study showed a significant difference in behavior, there are some concerns with the study. First, the participants were exposed to very high levels of pheromones; it is unclear if this response would happen in a naturalistic setting. Secondly, although they identified the figure as masculine or feminine, this is not a clear study of sexual attraction but rather of whether participants perceived a person's walk as feminine or masculine. It can be debated whether this is a reliable measure of sexual behavior. Finally, the study is done on a relatively small sample. The study would need to be replicated on a much larger sample in order to determine whether the results are reliable.
- - - - In their first experiment, researchers used a volunteer sample of 67 men and 60 women (age range 21 - 34). The researchers used a double-blind independent samples design. Each participant wore a sticky pad pasted to their upper lip - one group was exposed to hexadecanal, and the other group to a placebo. The participants played computer games with a mysterious partner. The participants were not aware that this “partner” was actually a computer algorithm designed to provoke them.
      - In each round of the game, both players were allocated money that they could keep if they agreed on how to divide it between themselves. The "mysterious partner," however, never agreed if the participant would receive the greater sum. After five rounds, it was clear that the participant was being discriminated against in the game.
      - The participants then began the second half of the experiment. The participants were again deceived by believing that they were playing a computer game with the same "mysterious partner." They competed to identify a change in the shape of a target. The first person to react was then allowed to "blast" his/her opponent with a loud noise blast. The volume of the "blast" was how the researchers chose to operationalize aggression. The game was set up so that the participant "won" 16 out of 27 trials. They were then able to set the volume before blasting the mysterious partner.
      - Mishor et al. (2021) carried out two experiments to test the effect of hexadecanal on both male and female behavior.
    - - Mishor et al (2021) carried out a second experiment with a sample of 25 men and 24 women. The goal was to determine how hexadecanal interacts with the brain to potentially cause aggression. In this study, the participants would play a computer game while in an fMRI where their computer opponent occasionally stole money from them. When this happened, they could choose to punish the mysterious partner by docking money from his/her account, without gaining any money themselves. The design was a repeated measures design with either hexadecanal, a placebo, or simply clean air being infused through the fMRI. The order of the conditions was counterbalanced.
        Women showed more "punishment" activity than men when exposed to hexadecanal. In addition, the researchers observed a difference in activity in the left angular gyrus - a part of the brain responsible for interpreting social cues. Whereas men who were exposed to hexadecanal showed activity in the left angular gyrus synced with activity in brain areas involved in processing social information and aggression (such as the amygdala), women showed a decrease in activity.
    - - The researchers used controls to increase the internal validity of the research and potentially identify a causal relationship. These included double-blind controls and counterbalancing.
      - Although the researchers attempt to make the link between the scent emitted from an infant and the protective behavior of mothers, the experiments are highly artificial and do not reflect an infant/mother relationship.
      - It is not clear yet under what circumstances adults release hexadecanal or how humans would actually process the odorant.
      - The sample sizes of both studies are small. The results of the study would have to be replicated with larger samples in order to determine the reliability of the findings.
      - Although the fMRI shows some brain activity, it was not able to demonstrate how this activity would lead to aggressive behavior.