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BIOLOGICAL LEVEL OF ANALYSIS: PHYSIOLOGY AND BEHAVIOR
Warmup: INTRO TO BIOLOGICAL LEVEL OF ANALYSIS1. A small amount of brain tissue from a person cannot be distinguished from that of a monkey.2. The human brain produces its own natural opiates that elevate mood and ease pain.3. The brain accounts for a larger percentage of body weight in humans than in any other species.4. Electrically stimulating a cats brain at a certain point can cause the animal to cower in terror in the presence of a small mouse.5. Both animals and humans seem to have reward centers located in the brain.6. We ordinarily use only 10 percent of our brains.7. Some people can write but are unable to read.8. If a blind person uses one finger to read Braille, the brain area dedicated to that finger expands.9. Adult humans cannot generate new brain cells.10. Some people have had the hemispheres of their brains split with no apparent ill effect.
What does biological perspective argue?Behavior is caused by physiology. Humans should bestudied as biological systems.We should also consider environment and cognition –they interact with our biology .This relationship is BIDIRECTIONAL, i.e. biology can affectcognition and cognition can affect biology.
Physiological FactorsMany physiological factors can play a role in behaviour:• Brain processes• Neurotransmitters• Hormones• Genes These interact with the environment: stress, a good looking person walking by, brain damage from an accident, etc.
Nature vs Nurture debate• Researchers debated whether human behavior is the result of biological or environmental factors (remember Money?)• INTERACTIONIST approach – today’s view is a holistic picture. They both interact.
Biological principles1. Behavior can be innate because it is genetically based – Evolution may play a key role in behavior2. Animal research can provide insight into human behavior3. There are biological correlates of behavior – There should be a link between a specific biological factor (e.g. hormone) and a specific behavior
Reductionist approach• Biological researchers often adopt this approach in study of human behavior – breaks down human behavior into its smallest parts (genes, neurotran- smitters, proteins) – reductionist approach• Sometimes criticized as overly simplistic• But we need a detailed understanding of how factors interact to cause certain behaviors.
Neurotransmission – the way how messages are sent between neurons• Neurons (nerve cells) – building block of behavior• 10-100 billion neurons in nervous system• Make 13 trillion connections w/ each other• Send electrochemical messages to brain so people can respond to stimuli (from environment or internal changes in body)
Important to know:How do each of these effect neurotransmission? • Axon • Neurotransmitters • Synapse • Terminal buttons • reuptake
Neurotransmitters and their effects on human behavior
How Neurotransmitters Can Affect Behavior• Mood, memory, sexual arousal and mental illness are effected by neurotransmitters• Study: Kasamatsu and Hirai (Buddhist monks) 1999 – Aim – determine how sensory deprivation affects the brain Method – studied Buddhist monks on a 72 hour pilgrimage to a holy mountain. Took blood samples before and after monks reported hallucinations Result – found increase in serotonin levels had activated the hypothalamus and frontal cortex
Look at page 41 –research in psychology Martinez and Kesner’s experiment• What was the aim?• How the procedure look like?• What are the strenghts and limitation of Martinez and Kesner’s experiment?
Activity• As a team you will develop a skit to explain: – Neural communication – How Neurons Communicate (synaptic transmission) – How neurotransmitters influence us• Create a skit, interview, or other interactive presentation.• Create a Title Board and vocabulary list.• Make sure each of your “actors” is labeled.
The Brain and Behavior• Early method to study the brain was to study a case of brain-damaged patients over a long period of time (longitudinally)• Most Famous is the case of Phineas Gage
Localization of brain function • Paul Broca (1861) found that people suffering from damage in the left frontal lobe of the brain (Broca’s area) were unable to understand and make grammatically complex sentences. His patients had trouble producing speech, but were able to understand it. • It’s called aphasia • Most famous case study a young man named Tan (only word he could say) • Autopsy revealed source of brain damage – his disability was the result of a specific brain trauma.
Localization of brain function • Carl Wernicke (1874) – first to describe area crucial for language comprehension – left posterior superior temporal gyrus • His patients could produce speech, but could not understand it. Called Wernicke’s aphasia • Now we more understand language processing.
Localization of brain function• By carrying out post-mortem studies of people with strokes, Brocka and Wernicke concluded that language processing is localized. It is possible to trace origin of behavior to a specific part of the brain.• This led to studies in localization to map out the brain’s functions.• Doesn’t explain all human behavior – but is a great step forward.
Localization of brain function and ethics in research• Robert Heath (1950s) - experiments electrical stimulation of specific parts of brains of depressed patients - they experienced pleasure.• the participants press the button themselves• during a three-hour session, the subject (B-19), electrically self- stimulated himself 1500 times.• “During these sessions, B-19 stimulated himself to a point that he was experiencing an almost overwhelming euphoria and elation, and had to be disconnected, despite his vigorous protests.”
Localization of brain function and ethics in research • James Olds - researches on rats • Aim: what could happen if rats’ pleasure centers were stimulated • The rat would receive electrical stimulation of the nucleus accumbens by pressing a lever • the rats were willing to walk across electrified grids in order to get to the “pleasure lever” • they preferred the stimulation to eating and drinking
Localization of brain function and ethics in research• Animal studies show that all drugs increse the production of dopamine (desire) and reduce the production of serotonine (satiety)• Both neurotransmitters play a central role in the feelings produced by such drugs as cocaine and nicotine• Frequent consumption of drugs increases amount of dopamine in nucleus accumbens
Localization of brain function and ethics in research• In order to carry out researches on the nucleus accumbens (to gain insight into the nature of addiction) animals suffered and were killed.• Is it ethical to use animal reserach for betterment of human beings?
Electroencephalogram (EEG)• EEG printout is often thought as a „brainwaves”• When neurons transport information through the brain they have an electrical charge• EEG register patterns of voltage change in the brain• Understanding of: sleep, emotions, epilepsy• Limited information – we can not reveal in deeper brain regions
PET positron emission topography• Scan monitors glucose metabolism in the brain• The patient is injected with a harmless dose of radioactive glucose• The radioactive particles emitted by the glucose are detected by PET scanner• Scan products coloured maps of brain activity• Diagnose: abnormalities like tumours, changes in Alzhaimer’s, compare brain differences in normal individuals and those with psychological disorders (schizophrenia),• PET (compared to MRI) can record ongoing activity in the brain, such as thinking
fMRI - functional magnetic resonance imaging• Provides three dimensional pictures of the brain structures• using magnetic fields and radio waves• shows actual brain activity and indicates which areas of the brain are active when engaged in a behaviour• easy to carry out• very often used
How the enviroment affects the brain• BRAIN PLASTICITY – refers to brain’s ability to rearange the connections between its neurons – the changes that occur in the structure of the brain as a result of learing or experience.• Every time we learn something new, the neurons connect to create a new trace in the brain. This is called DENDRITIC BRANCHING because the dendrites of the neurons grow in numbers and connect with the other neurons.
Rozenweig & Bennet (1972)• Aim: to measure the effect of either enrichment or deprivation on the development of neurons in the cerebral cortex• Two settings: enriched, stimulating environment with lot of toys and depriveted environment• Rats spend 30 or 60 days in their cages and then they were sacrificed
Rozenweig & Bennet (1972)• Post- mortem studies of rats’ brains showed that rats from stimulating environment had an increased thickness in the cortex• The frontal lobe (associated with thinking, planning and decision making) was heavier• Further studies demonstrated cortical thickness increases when rats were placed with other rats
COMPANY + INTERSETING TOYS= devlopment of CEREBRAL THICKNESS Can these findings be generalized to humans?
London Taxi driver study – Eleanor Macguire (2000)• Dr Eleanor Maguire scanned the brains of 16 London black-cab drivers, who had spent an average of two years learning the Knowledge – street names and routes in London.• The taxi drivers had a larger right hippocampus than control subjects, and the longer they had been on the job, the larger their hippocampus size.• These findings seem to indicate that the right hippocampus plays an important role in storing spatial memories
Read the study and answer the following questions• Why were london taxi drivers chosen as subjects in the study?• Which part of the brain were they investigating and why?• What variables were controlled in this study?• Who were the control group and what is the purpose of having a control group?• What two research methods were used?• How does the first method differ from a lab experiment?• Outline the results of the study• What other variable could explain the differences found?• What are demand characteristics?• State one criticism of the study
London Taxi driver study – Eleanor Macguire (2000)• Significantly greater volume of gray matter was found in only one brain area in the taxi drivers: the left and right hippocampi.• The posterior hippocampus had more gray matter bilaterally (both sides) in taxi drivers than in controls.• The anterior hippocampus had more gray matter bilaterally in the controls than in the taxi drivers.
• Read the study on page 47: Richard Davidson (2004)• Could meditation change the brain activity?
How the enviroment affects the brain • Mirror neurons are neurons that fire when an animal performs an action or when the animal observes somebody else perform the same action. • Gallese research (1996) with monkeys and peanuts • Iacoboni reserch (2004) with human faces • Mirror neurons - empathy for others
Functions of Hormones in Human Behavior• Hormones – chemicals that affect behaviour• They are produced by the glands that make up the endocrine sysytem• hormones enter directly into bloodstream
The endocrine system HORMONE GLANDS FUNCTION Flight or fight response, Adrenaline Adrenals arousal Arousal, stress hormone, Cortisol Adrenals memory Melatonin Pineal Regulation of sleep Pituitary and Oxytocin Mother-child attachment hypothalamusTestosterone and Gonads Development, emotion oestrogen
Oxytocine• Produced by hypothalamus after being stimulated by the pituarity gland• Plays a role in inducing labour contractions and lactation• It is released with touches and hugs• Associated with bonding between: – mother and child – lovers• „love hormone”
Melatonin• Production of melatonin by pineal gland is stimulated by darkness and inhibitted by light• Melatonin level in bloodstream peak in the middle of the night, and gradually decrease towards morning• When winter approaches – we become tired earlier• Melatonin release correlates with the circadian rhythm – biological clock
Seasonal affective disorder• Rosenthal (1987) found that higher levels of melatonin contribute to seasonal affective disorder (SAD) – a subcategory of depression that is characterized by sleepiness and lethargy – as well as craving for carbohydrates.• Reduced levels of sunlight in fall and winter are believed to disrupt circadian rhythms in certain people leading to this form of depression.