Biological Approach

Topics & Studies

Localization of Function

the theory that specific parts of the brain are responsible for specific behaviors or cognitive processes

Neuroplasticity

refers to the brain’s ability to alter its own structure following changes within the body or in the external environment

Neurotransmitters

the body’s natural chemical messengers that transmit information from one neuron to another; crosses synapse, fits into receptor sites on the post-synaptic membrane

Horomones

chemical substances produced in the body that regulate various physiological processes and behaviors; released directly into the bloodstream and take longer to produce changes in behavior than neurotransmitters

Pheromones

chemical substance produced and released into the environment by an animal affecting the behavior or physiology of others of its own species

Gene & Behavior

deals with understanding how both genetics and the environment contribute to individual variations in human behavior

Evolution

theory that as genes mutate, those that are advantageous are passed down through a process of natural selection

Kinship Studies

measure the frequency of a behavior across/within generations, often longitudinal, use case-control studies.

Milner (1966)

LOCALIZATION OF FUNCTION

Aim: to better understand the effects that the surgery had had on patient HM

Method: longitudinal case study

Procedure: Milner used many different strategies

• psychometric testing: IQ testing

• direct observation of his behavior

• interviews with both HM and his family members

• cognitive testing: memory recall tests and learning tasks (reverse mirror drawing)

• MRI to determine extent of damage to the brain
  

Results: HM could not acquire new episodic knowledge (memory of events) and he could not acquire new semantic knowledge (general knowledge about the world). HM had a capacity for working memory since he was able to carry out a normal conversation. Memories in the form of motor skills (procedural memory) were well maintained.

Conclusion: Suggests that the brain structures that were removed from his brain are important for long-term explicit memory.

Maguire (2000)

LOCALIZATION OF FUNCTION & NEUROPLASTICITY

Aim: to see whether the brains of London taxi drivers would be somehow different as a result of their knowledge of the city and the many hours that they spend behind the wheel navigating the streets of London.

Method: quasi-experiment

Procedure: Structural MRI scans were obtained. 16 right-handed male London taxi drivers participated; all had been driving for more than 1.5 years. Scans of 50 healthy right-handed males who did not drive taxis were included for comparison. The mean age did not differ between the two groups.

Results:

1. Increased grey matter was found in the brains of taxi drivers compared with controls in two brain regions, the right and left hippocampi. The increased volume was found in the posterior (rear) hippocampus.

2. Changes with navigation experience – A correlation was found between the amount of time spent as a taxi driver and volume in the right posterior hippocampus.
   

Conclusion: The results provide evidence for structural differences between the hippocampi of London taxi drivers and control participants, therefore suggesting that extensive practice with spatial navigation affects the hippocampus.

Draganski et al. (2004)

NEUROPLASTICITY

Aim: to see whether learning a new skill would change the structure of the brains of participants.

Method: experiment, independent measures design

Procedure: All participants had an initial MRI scan to establish a baseline of grey matter and brain structure. They were then divided into two groups: jugglers and non-jugglers. Jugglers learned and practiced a three-ball cascade routine, notifying researchers once mastered, then underwent a second MRI. They stopped juggling afterward, and a third scan was done three months later. Non-jugglers served as a control group and had scans on the same schedule. Voxel-based morphometry (VBM) was used to analyze differences in grey matter between the groups.

Results: Initially, there were no structural brain differences. After three months, jugglers showed increased grey matter in the mid-temporal cortex—linked to movement coordination and visual memory. This suggests dendritic growth from learning. After six months, grey matter density had declined but remained above baseline, indicating neural pruning. Grey matter reduced when juggling stopped, showing a loss of stimulation-related connections.

Conclusion: Learning can increase grey matter, and lack of use can decrease it. This supports a cause-and-effect link between learning and brain structure.

Rogers & Kesner (2003)

NEUROTRANSMITTERS

Aim: to determine the role of acetylcholine in the formation of spatial memory

Method: controlled experiment with a placebo condition

Procedure: Rats were trained to learn a simple maze, but before the memories could be learned well-enough to be transferred from short-term memory to long-term memory, the rats were divided into groups and injected with drugs:

• Group 1 was injected with scopolamine (known to block the reception of acetylcholine by the post-synaptic neurons). This means that acetylcholine, a neurotransmitter expected to help form memories, cannot travel from one neuron to another. This was the no acetylcholine condition.

• Group 2 was injected with physostigmine (a drug that blocks cholinesterase) which is what cleans up the acetylcholine from receptor proteins on the post-synaptic neurons, returning the neurons to their resting potential, where no nerve impulse is being sent. Therefore the acetylcholine continued to act. This was the high acetylcholine condition.

• Group 3 was the placebo group, and was injected with an inert saline solution that had no effect on acetylcholine.

Rats were then placed back in the maze and ran multiple trials over two days. Their learning and memory was measured by comparing the number of mistakes they made while completing the maze. The difference between the first five and the last five trials on day one was taken as a measurement of encoding, while the difference between the last five trials on day one and the first five trials on day two was used to measure retrieval.

Results: The no acetylcholine condition showed a deficit in encoding (but not retrieval), making relatively more mistakes during the last five trials on the first day. The high acetylcholine condition made relatively fewer mistakes during the last five trials on the first day and showed no deficit in encoding. However, the high acetylcholine condition did show a deficit in retrieval.

Conclusion: Suggests that acetylcholine plays an important role in memory encoding, because the rats with low acetylcholine levels wandered around the maze as though lost, even though they had learned it previously. At the same time, while acetylcholine may be necessary for memory encoding, the physostigmine condition suggests that too much acetylcholine may interfere with memory encoding and retrieval.

Antonova (2011)

NEUROTRANSMITTERS

Aim: to determine how blocking the acetylcholine receptors with scopolamine affects spatial memory.

Method: lab experiment, double-blind experiment

Procedure: 20 healthy male adults with 2 conditions. Injected with either scopolamine or a placebo 70-90 min before the experimental task. Participants were put into fMRI scan while play a virtual reality arena task. Participants were first trained in game so they knew the rules. After training, the participants' brain activity were measured for 6 trials. Participants returned 3-4 weeks later and redid the test with opposite treatment to original study.

The arena task - was a complex virtual reality game, goal is to navigate around an "arena" with goal of reaching a role. After learning where the pole is, screen goes black for 30 seconds. Participants were asked to rehearse how to get to the pole in the arena during this time. When the arena reappeared, the participant was at a new starting point. They had to use spatial memory to determine how to get to the location of the pole.

Results: When the participants were injected with scopolamine, they demonstrated a significant reduction in the activation of the hippocampus compared to when they received a placebo. This suggests that scopolamine impairs memorization of new information by decreasing spiking activity within the hippocampus.

Conclusion: It appears that acetylcholine could play a key role in the encoding of spatial memories in humans.

McGaugh & Cahill (1995)

HOROMONES

Aim: to study the role of emotion in the creation of memories.

Method: experiment

Procedure: Participants were split into two groups and shown 12 slides, each paired with a different story. One group heard a neutral story about a hospital visit during a disaster drill. The other group heard an emotional story about a boy whose feet were severed in a car accident and later reattached in surgery. Afterward, participants rated the emotional intensity (1–10). Two weeks later, they returned for a memory test using a recognition task with multiple-choice questions about the slides.

Results: In the first test, the boring story group did not perform too well in terms of recollection. The interesting story group remembered more details. With the beta blocker they performed just as bad as the first group.

Conclusion: The amygdala plays a significant role in the creation of memories linked to emotional arousal

Newcomer (1999)

HOROMONES

Aim: to investigate whether high levels of the stress hormone cortisol interfere with verbal declarative memory.

Method: double blind, lab experiment

Procedure: 3 groups - high-cortisol, low-cortisol, and placebo. All participants were asked to listen to and recall a prose paragraph (made up sentences with no structure). Each day, they were given a different piece of prose with the same level of difficulty. Participants were tested three times:

1. Without taking any cortisol

2. One day after taking the pill

3. Four days after taking the pill

4. Six days after taking the pill to make sure that there were no long-term effects of the treatment
   

Results: Indicated that high cortisol levels impaired performance in the memory task since the participants who received the highest level of cortisol also showed the worst performance in verbal declarative memory. The performance of participants in the high cortisol condition also returned to normal after they stopped taking the hormone tablet.

Conclusion: It appears that high levels of cortisol interfered with the recall of the prose passage, whereas moderate levels of cortisol may have actually assisted in the recall of the passage. This makes sense as there are cortisol receptor sites on the hippocampus, which is responsible for the transfer of information from STM to LTM and vice versa.

Wedekind (1995)

PHEROMONES & EVOLUTION

Aim: to determine whether one's MHC would affect mate choice

Method: double-blind experiment

Procedure: Men wore a T-shirt for two nights, using scent-free products and avoiding activities that could alter body odor (e.g., smoking, spicy food, sex). Two days later, women—tested during their most odor-sensitive menstrual phase—smelled and rated 7 T-shirts (3 from MHC-similar men, 3 from MHC-dissimilar men, 1 unworn control) for intensity, pleasantness, and sexiness. They used nasal spray beforehand and read Perfume to heighten olfactory sensitivity.

Results: Women scored male body odors as more pleasant when they differed from their own MHC than when they were more similar. This difference in odor assessment was reversed when the women rating the odors were taking oral contraceptives.

Conclusion: This suggests that the MHC may influence human mate choice.

Zhou et al. (2014)

PHEROMONES

Aim: to see the effect of AND and EST on heterosexual and homosexual men and women

Method: experiment where the IV was manipulated

Procedure: 24 heterosexual males, 24 heterosexual females, 24 homosexual males, and 24 bisexual or homosexual females. Participants were presented with a point-light walker task (PLW), a set of dots that move in a way that represents the properties of human motion. The participants were asked to observe the stick figure in motion and to identify its sex.

They performed the task at around the same time of the day on three consecutive days while being continuously exposed to either androstadienone mixed with cloves, estratetraenol mixed with cloves, or a control solution, also mixed with cloves.  The participants only carried out the task while smelling one of the solutions each day.  The scents were counterbalanced to control for order effects.  

Results: When heterosexual females and gay males were exposed to AND, they had a higher rate of identifying the stick figure as “masculine” than the control group.  AND had no significant effect on heterosexual men or lesbian women. By contrast, smelling EST systematically biases heterosexual males toward perceiving the walkers as more feminine. The effect was not statistically significant in bisexual and lesbian women.

Conclusion: It appears that AND and EST may have some effect on human sexual behavior.

Kendler et al. (2006)

GENES & BEHAVIOR

Aim: to investigate three questions in their study:

1. Past studies suggest a 35 - 45% heritability of major depression. Would this be true in a large Swedish sample?

2. Are there significant gender differences in the heritability of major depression?

3. Is there evidence that genetic and environmental factors in major depression differ over time?
   

Method: correlational

Procedure: The study used 15,493 verified twin pairs from the Swedish Twin Registry. Trained interviewers conducted phone interviews (1998–2003) to assess lifetime major depression using modified DSM-IV criteria. 8,056 twins met the criteria, and 322 reported antidepressant use. Interviews also gathered data on shared childhood environments and individual-specific adult life events linked to depression risk.

Results: Indicates that the concordance rates for major depression were significantly higher in women than men. In addition, the correlations were significantly higher in monozygotic than in dizygotic twins. They also found no correlation between the number of years that the twins had lived together and lifetime major depression. The estimated heritability of major depression was 0.38, in line with previous research. There were also no significant differences seen in the roles of genetic and environmental factors in major depression in the three cohorts spanning birth years 1900-1958.

Conclusion: This study suggests both that the heritability of major depression is higher in women than in men and that some genetic risk factors for major depression are sex-specific. In addition, the study confirms the level of heritability of major depression found in other studies, strengthening the reliability of European twin studies.

Capsi et al. (2003)

GENES & BEHAVIOR

Aim: To investigate whether there is a gene-environment interaction (G x E) between the 5-HTT serotonin transporter gene and stressful life events in the development of depression.

Method: Longitudinal correlational study using genetic testing, self-reported questionnaires, and mental health assessments.

Procedure: Studied 847 New Zealanders, all 26 years old and part of a birth cohort assessed regularly for mental health up to age 21. Participants were divided into three groups based on their 5-HTT genotype:

Group 1: two short alleles

Group 2: one short, one long allele

Group 3: two long alleles

They completed a “Stressful Life Events” questionnaire covering 14 events (e.g., financial, employment, relationship stressors) experienced between ages 21–26. They were also assessed for symptoms of depression and suicidal thoughts.

Results: Found that individuals with one or two short 5-HTT alleles showed more depressive symptoms and suicidal ideation following stressful life events. Those with two long alleles were less affected. The gene alone didn’t predict depression—only its interaction with stress did.

Conclusion: The studies support the diathesis-stress model: a genetic predisposition (short 5-HTT allele) increases vulnerability to depression when combined with environmental stress. However, further research is needed to fully understand the gene-environment relationship in depression.