TOPICS

Neuroplasticity

• Neuroplasticity

  • Synaptic Plasticity/Dendritic Branching

  • Synaptic/Neural Pruning

    • “Use It or Lose It”

• Evidence of Neuroplasticity as seen in the Draganski (2004) study

5. Hormones

• Differences between Endocrine (hormonal) messages from Neural messages

• Hormone: Adrenaline

  • Effect of Adrenaline on emotional memory as seen in the Cahill & McGaugh (1995) study 

6. Pheromones

• Characteristics of pheromones

• Steps to identify the existence of a pheromone

• Reasons why the existence of a human pheromone is still being debated

• If a human pheromone exists, where/how would it be secreted by the body to communicate its message?

• “Pheromone”: Hexadecanal

  • Effect of Hexadecanal on aggression in men and women as seen in the Mishor et al. (2021) studies

Neuroplasticity

Vocab

• Neuroplasticity: The ability of the brain to change its natural structures to adapt to change. there are two types of neuroplasticity, dendritic branching and neutral pruning.

  • Dendritic branching (synaptic plasticity): When neurons connect to create new traces in the brain which is caused by learning something new and constantly repeating the task. (growth of connections)

  • Neutral pruning (synaptic): When the repetition of a task is discontinued causing the extra neurons and synaptic connections to be lost. Though most are lost not all of them are lost which means you’ll still be able to perform the task just not as easily as before as the exsis neurons that were taking space were eliminated. (loss of connections)

  • “Use it or Lose it”: If you don’t use and practice your skill continuously you will lose it.

    • The brain is most “plastic” at the age of 2 and the second is at the age of 12 and the teenage years.

Evidence of Neuroplasticity as seen in the Draganski (2004) study

• Procedural details:

  • Aim: The aim of the study was to see whether learning a new skill - in this case, juggling - would have an effect on the brains of participants.

  • Who? 24 volunteers between the ages of 20 -24. There were 21 females and 3 males. All of the volunteers were non-jugglers at the start of the study.

  • Where? The study was done at the houses of the participants. The participants were told to notify the researchers when they had mastered the juggling sequence they were taught. (field study)

  • What? They split the 24 volunteers into two groups, a control group (non-jugglers), and a juggler group. The participants that were in the juggler group were taught a 3-ball juggling routine which they had to master at their homes by themselves and then notify the researchers. The researchers took 3 separate MRIs of the participants, pre-, peri, and post. they took the pre-MRI scan before the participants learned to juggle, the peri-MRI scan after they had mastered the juggling routine, and the post-MRI scan 3 months after the peri-MRI scan where they were told to stop juggling.

  • Findings? The study found no initial grey matter differences between the jugglers and non-jugglers groups in the pre-MRI scan. However, after learning to juggle, the juggler’s group showed a significant increase in grey matter in the mid-temporal area of both hemispheres, which is a region associated with visual memory (peri-MRI scans). Three months after the jugglers group were told to stop juggling, and as their skills declined, the increase of grey matter diminished. the non-jugglers on the other hand showed no changes in grey matter throughout the study. These findings suggest that juggling relies more on visual memory rather than procedural memory, which would typically involve the cerebellum or basal ganglia.

• Connection to study: The Draganski (2004) study provides evidence of neuroplasticity, which is the ability of the brain to change its natural structures to adapt to change. There are two types of neuroplasticity, dendritic branching which is the growth of connections, and neutral pruning which is the loss of the extra connections made when learning a new skill. In this study, there were 24 volunteers made up of 21 females and 3 males around the ages of 20-24. They were split IP into two groups, a control group and a juggling group. The juggling group, whose participants learned a juggling routine, showed an increase in grey matter in the mid-temporal areas of the brain, a region associated with visual memory, in the second MRI scan the researcher took. This increase in grey matter shows that the brain can adapt structurally to acquire new skills. Moreover, when the participants were told to stop juggling for 3 months after the second MRI, their skills diminished and the amount of grey matter in the mid-temporal area decreased after the post-MRI scan. This shows the brain’s ability to remodel itself based on its use and disuse.

Hormones

Vocab

• Hormones: Are another form of chemical messengers that are secreted (released) from glands of the endocrine system.

  • Endocrine system: The body’s second communication system after the nervous system.

• Endocrine messages: They are slow messages that can take several seconds or more before the bloodstream carries a hormone from an endocrine gland to its target tissue.

  • Endocrine gland: The glands of this system secrete (release) another form of chemical messengers called hormones.

  • Differences between endocrine and neural messages: Endocrine messages are slower and travel through the bloodstream, causing long-lasting effects throughout the body. Neural messages, on the other hand, are fast and travel through nerve cells, causing quick, short-term responses.

• Adrenaline: Or Epinephrine is secreted by adrenal glands and is responsible for arousal and the “fight or flight response”. It plays a role in emotional memory formation.

Effect of Adrenaline on emotional memory as seen in the Cahill & McGaugh (1995) study

• Procedural details:

  • Aim: The aim of the study was to investigate the role of adrenaline and the amygdala on emotional memory.

  • Who? There were two groups of participants (amount not specified) who listened to two different types of stories paired with 12 visual slides.

  • Where? The study was conducted in an artificial setting so it lacks ecological validity as it’s a lab experiment.

  • What? In the study, the participants were divided into two groups, each of which viewed 12 slides paired with a different story. one group heard a neutral story of a mother and son visiting the father at the hospital during a disaster drill, while the other group heard a traumatic story about a boy who was injured in a car accident and had his limbs surgically reattached. Two weeks later the participants returned to complete a memory test in the form of a recognition task, where they answered multiple-choice questions about specific story details. In a follow-up study the participants in the “traumatic story group” were given propranolol, a beta-blocker that inhibits adrenaline release and amygdala activation to study its effects on emotional memory formation.

  • Findings? The study found that participants who heard the more traumatic story had better recall of specific story details and could remember more details from the slides compared to those who heard the neutral story. In the follow-up study, the participants in the “traumatic story group” who received the beta-blocker propranolol (inhibits adrenaline release and amygdala activation) performed no better in memory recall than those who heard the neutral story. Due to these results, the researchers concluded that adrenaline and amygdala activation play an important role in emotional memory formation.

• Connection to study: The Cahill & McGaugh (1995) study provides possible evidence of adrenaline, which is a hormone secreted by adrenal glands and is responsible for both the “fight or flight response” and emotional memory formation on memory. In the study, the participants who heard the traumatic story, which would increase adrenaline levels, recalled more specific details compared to those who heard the neutral story. In the follow-up study, when the participants in the “traumatic story group” were given propranolol, a beta-blocker that inhibits adrenaline release and amygdala activation, their memory recall was no better than that of the participants who heard the neutral story. The findings suggest that adrenaline enhances emotional memory formation by activating the amygdala, which is a region in the brain associated with processing information, therefore linking adrenaline to stronger memory retention during emotionally charged events.

Pheromones

vocab

• Pheromones: They are chemical signals that help some species communicate. They prompt some kind of behavioral or psychological reaction. They are not smells, they are chemical molecules.

  • How to identify the existence of a pheromone:

    1. Identify a specific behavior

    2. Isolate the molecule

    3. synthesize (create a fake version of the molecule)

    4. Test synthetic version

       • Same effects = Pheromone

       • Not the same effects = No pheromone

  • Example: Male butterflies fluttering wings from female pheromones.

• Reasons why the existence of a human pheromone is still being debated: We don’t have any conclusive solid evidence to clearly show that humans have pheromones and there is no conclusive evidence stating that primates, which we have evolved from, have pheromones. Due to this the existence of a human pheromone is still being debated.

  • Scientists have not been able to provide evidence of a consistent and strong behavioral response to any human-produced chemical cue.

  • They have not been able to identify a single human pheromone definitively.

  • They have not been able to isolate a specific molecule to synthesize a fake pheromone.

• If a human pheromone exists, where/how would it be secreted by the body to communicate its message? The main order-producing organ would be the skin because it’s the largest organ in the body.

  • Specifically, the armpits would be the ideal location for dispersing pheromones.

    • They are among the warmest parts of the body and the first to sweat

    • They have lots of sweat glands

    • They are high on the torso and can easily send odor to other’s noses

    • They are protected from evaporation

    • They tend to have strong hair growth (which helps disperse order)

• Hexadecanal: A “pheromone” that appears to foster aggressive behavior in women but blunt it in men.

Effect of Hexadecanal on aggression in men and women as seen in the Mishor et al. (2021) study

• Procedural details: Study 2

  • Aim: The aim of the study was to determine how hexadecanal interacts with the brain to potentially cause aggression.

  • Who? The participants in the study were 25 men and 24 women, totaling 29 adults.

  • Where? The study took place in a research facility which is a controlled environment since the study involved fMRI scanning. (lacks ecological validity)

  • What? The participants in the study played a computer game while in an fMRI scanner. During the game a virtual opponent would occasionally steal money from them and the participants could choose to “punish the opponent” by deducting money from their accounts without personal gain. The study used a repeated measure design where participants were exposed to hexadecanal, a placebo, or clean air, in different sequences. Researchers would then examine the brain activity of the participants, focusing on differences in aggression-related behavior and activation in brain areas linked to social and aggression processing.

  • Findings? The study showed that women showed more “punishment” activity than men exposed to hexadecanal. Also, the researchers found differences in brain activity in the left angular gyrus, which involves interpreting social cues. In men exposed to hexadecanal, brain activity in the left angular gyrus was synchronized with areas of the brain associated with processing social information and aggression, such as the amygdala. In contrast, women exhibited a decrease in activity in the left angular gyrus when exposed to hexadecanal. Overall, the findings suggest that hexadecanal influences aggression differently in men and women, affecting their brain activity in different ways.

• Connection to the study: The Mishor et al. (2021) study suggests that hexadecanal, which is a “pheromone” that appears to foster aggressive behavior in women but blunt it in men, influences aggression differently in men and women. In the study, participants played a computer game where they could punish a virtual opponent who stole from them. Women exposed to hexadecanal showed more aggressive “punishment” behavior than men, and fMRI scans revealed gender-specific effects on the left angular gyrus, a region involved in interpreting social cues. Men showed synchronized activation between the left angular gyrus and areas linked to social and aggressive processing, like the amygdala, whereas women showed decreased activity in the left angular gyrus. These findings suggest that hexadecanal may increase aggression-related responses in women and alter social-cue processing linked to aggression in men.

If you get a study that was a GWAS study, you won’t always know it was a GWAS study, but you will be able to tell if it was a GWAS or linkage study if you see a gene (allele) like the 5HTTP gene or the RBFOX1 gene. They have strange names, and GWAS studies are huge while linkage studies are smaller. (A study looking at DNA)

Polymorphisms mean different genes. For example, you can have two long 5HTTP genes, one long and one short, or two short.