Biological Approach

Localization and plasticity

Localization

Case of Eugene Pauly Aim: investigate localization Background: EP had a viral infection in the brain, causing his amygdala and hippocampus to be completely destroyed Observations: Could not draw a map of his home, but could remember how to go to the bathroom (due to the latter being an associative task and the former being cognitive in nature) EP’s basal ganglia was undamaged Evaluation: (L) case study and so not replicable

Plasticity

Maguire et al. Aim: investigate whether brains of London taxi drivers would be different as a result of their knowledge of the city Procedure: conducted MRI scans of right-handed London taxi drivers who had their license for at least 1.5 years and control right-handed participants Results: taxi drivers had significantly larger posterior hippocampi, with volume correlating with amount of time spent as taxi driver (hippocampus changed according to environmental demands) Evaluation: (L) no cause-effect relationship established; (S) idea that people with larger hippocampi were more spatially talented and so chose to be taxi drivers disproven by correlation of size with time driving

Neurotransmission

Neurotrans-mitters and memory

Rogers and Kesner Aim: determine the role of acetylcholine in memory formation Procedure: Rats put into a maze with food until they found the food Half the rats injected with scopolamine (acetylcholine antagonist), other half injected with placebo Rats put back into the same maze Results: scopolamine group took longer to locate the food and made more mistakes Evaluation: (L) reductionist approach to memory; (L) low generalizability to humans

Hormones and memory

McGaugh and Cahill Aim: investigate the role of adrenaline and the amygdala on memory formation Procedure: half of participants heard a boring story while other half heard a very emotionally-arousing story, then asked to come back after two weeks to answer questions about the story Follow-up: half of participants hearing emotionally-arousing story were injected with propranolol (beta-blocker, preventing the release of adrenaline) Results: better recall for emotionally-arousing story but equal with boring story if injected with propranolol Evaluation: (S) has been applied with good results to PTSD patients

Pheromones and behavior

Pheromones and mating behavior

Zhou et al. Aim: investigate if AND and EST influence human mating behavior Procedure: participants were asked to watch stick figures walking on a screen and to determine their gender while being exposed to the smell of cloves with EST, AND, or control Results: Smelling AND biased heterosexual females and gay males (but not others) toward perceiving the stick figures as more masculine Smelling EST biased heterosexual males and lesbian females (but not others) toward perceiving the stick figures as more feminine Evaluation: (L) failed replication means that it may not be reliable; (L) doses of AND and EST were significantly higher than what humans usually secrete

Pheromones and aggression

Mishor et al. Aim: to investigate hexadecanal’s role in human aggression Procedure: participants sticked a pad on their upper lip with hexadecanal or control while playing a computer game with an algorithm designed to provoke aggression, then allowed to blast the opponent with a loud noise (operationalized as aggression) Results: women exposed to hexadecanal were more likely to punish the partner with severe blasts than control women, while there was no difference for men (shows that hexadecanal plays a role in maternal protective tendencies) Evaluation: (L) humans do not have the vomeronasal organ so does not explain mechanism of action; (L) highly artificial and does not directly study mother-child relationship

Kinship studies

Depression

Weissman et al. Aim: investigate the potential genetic nature of MDD Procedure: [longitudinal] selected MDD participants from outpatient clinic and control participants from the same community, three generations of families interviewed and given diagnoses Results: depression in grandparents (and not parents) was an indicator that a person has depression Evaluation: (S) longitudinal and so more reliable; (L) amount of time child spends with grandparent is a confounding variable; (L) genotype not actually studied

Anxiety

Wang et al. Aim: investigate whether math anxiety is due to classrooms or genetically-linked Procedure: fraternal (DZ) and identical (MZ) twins completed assessments on math anxiety and general anxiety Results: genetic factors account for 40% of math anxiety (60% due to environment); due to genetic risk factors for anxiety leading to poor math performance and then more anxiety (spiraling causality) Evaluation: (L) correlational (no cause-effect); (L) low population validity as twins don’t represent general population

Epigenetics and depression

5-HTT Gene

Caspi et al. Aim: examine the role of 5-HTT gene (plays a role in serotonin pathways) in depression Procedure: participants divided into groups based on genotype (5HTT gene has a short and long allele), given a ‘stressful life events’ questionnaire, and assessed for depression Results: participants who had one or more short alleles demonstrated more symptoms of depression in response to stressful life events (strongest for three or more events) Evaluation: (L) assumes that serotonin causes depression (reductionist)

Evolutionary psychology

Social Competition Hypothesis

Raleigh et al. Aim: investigate the relationship between social status and serotonin (linked to depression) in monkeys Procedure: [observation] groups of monkeys observed and serotonin levels measured throughout Results: There were naturally arising changes in the hierarchy (dominant monkeys became submissive and vice versa) Serotonin levels increased in monkeys that become dominant and decreased in monkeys that became submissive Evaluation: (L) assumes that serotonin causes depression (reductionist); (L) social lives of humans are much more complex than those of monkeys, so not very generalizable

Pathogen Host Defense Hypothesis

Raison et al. Aim: test PHDH Procedure: gave infliximab (anti-inflammatory drug) to depressed patients Results: depressed patients who showed high levels of inflammation had reduced depressive symptoms after the drug but no improvement was shown by patients without inflammation (meaning there may be different types of depression) Evaluation: (L) theory can only explain depression in patients with inflammation (too simplistic)

Localization

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

Parts of the brain

Brain stem: responsible for regulating life functions (e.g., breathing, heart rate, and blood pressure); oldest part of the brain. Cerebellum: plays a role in balance, motor function, and learning (specifically in classically conditioned responses). Cerebral cortex: largest part of the brain associated with higher brain functions; newest part of the brain. Frontal lobe: associated with executive functions (planning, decision-making, speech). Occipital lobe: associated with visual processing. Parietal love: associated with perception of stimuli. Temporal lobe: associated with auditory processing and memory. Limbic system: associated with emotions. Amygdala: plays a role in the formation of emotional memory and fear responses. Basal ganglia: plays a role in habit-forming and procedural memory. Hippocampus: responsible for the transfer of STM to LTM. Hypothalamus: involved in homeostasis, emotion, thirst, and hunger. Nucleus accumbens: plays a role in addiction and motivation.

Dendritic branching

When dendrites of the neurons grow in numbers and connect with other neurons; occurs when we learn something new.

Synaptic plasticity

Synapses become stronger through repeated use, but when a synapse is not used or is under-stimulated, it may undergo synaptic pruning (removal of the synapse).

Neurotransmission

The process by which messages are sent across neurons.

Neurotransmitters

Molecules that are released by one neuron to attach to receptor sites at another neuron across the synapse. Examples: Acetylcholine: plays a role in the consolidation for memory in the hippocampus. Dopamine: Controls the brain’s reward and pleasure centers and plays a key role in motivation. Norepinephrine: arousal and alertness. Serotonin: sleep, arousal levels, and emotion.

Exogenous agonists

Drugs that bind to the receptor site and activate it similarly to neurotransmitters.

Exogenous antagonists

Drugs that block the receptor site and do not allow the neurotransmitter to do its job.

Pheromones

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

Andostadienone (AND)

A potential human pheromone found in male semen and sweat.

Estratetraenol (EST)

A potential human pheromone found in female urine.

Vomeronasal organ

A structure that detects pheromones; found in many animals but not in humans (a limitation for the theory that pheromones affect human behavior).

Kinship studies

Used to determine whether a behavior or physiological disorder is due to genetic or environmental factors.

Epigenetics

Argues that for a behavior to occur, genes must be expressed in response to environmental or physiological changes.

Evolutionary psychology

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

Social competition hypothesis

Argues that depressive behaviors are part of an involuntary subordinate strategy that provides a mechanism for yielding in competitive situations. In the past, these behaviors would have allowed for the conservation of energy and minimization of injury, but today are seen as maladaptive.

Resource holding potential

An animal’s awareness of its own fighting capacity (ability to know that it cannot win in certain situations). A precursor to self-esteem.

Pathogen host defense hypothesis

Argues that the genes that increase one’s risk for depression also increase one’s immune response to infections. Therefore, the depression symptoms of social withdrawal, lack of energy and loss of interest may have played a key role in protecting our ancestors from infectious diseases.