UNIT 4 BIOLOGICAL APPROACH Flashcards
Brain Imaging Techniques
Measuring brain activity
EEG
Structural Imagery
the CT scan
the MRI
uses water in our body, magnets, hydrogen protons
once the magnet flips, a signal is captured and an image is produced
Functional Imaging
PET scan Positron Electron Tomography
fMRI functional Magnetic Resonance Imaging
a series of MRI pictures taken less than a second apart
modeled by a computer
shows activity of brain over time
SPECT
view how blood flows through arteries and veins in the brain
reduced blood flow→ more sensitive to injury
radioactive drug and scanner used to make detailed images
study for brain imaging
maguire
maguire
Maguire
Aim:
to see whether the brains of London taxi drivers would be
different as a result of their training and use of spatial memory.
Purposive sampling
Procedure:
16 taxi driver MRIs compared to 50 non-taxi driver MRIs.
single-blind study, the researcher did not know whether they were looking at the scan of a taxi driver or a control.
pixel counting → area of hippocampus
VBM→ neural density around the area
Findings:
The posterior hippocampi of taxi drivers were significantly larger relative to those of control subjects and the anterior hippocampus were significantly smaller. that the volume of the right posterior hippocampus correlated with the
amount of time spent as a taxi driver. No differences were observed in other parts of
the brain
Application to theory:
The hippocampus, even in adults, can change and grow in density, in response to the environment. The taxi drivers had to learn the map of London and they had to use it every day. Therefore they create new neural pathways for memory but they also use them often, making them stronger as a result. It appears that the posterior
hippocampus plays a key role in spatial memory and navigation, whereas the
anterior hippocampal region may be more involved in perception and coping with
novelty.
Localization
Every behavior is associated with a specific brain region
Nervous system has three components
sensory: sensory input
integration: brain and spinal cord processing
motor output: reaction to the stimulus
Nervous system is made up of neurons
receive signals through branching dendrites and send it through axons
all or none process
Neurotransmitters: neuron produced chemicals that cross synapse to carry messages to other neurons or cells
brain injury can teach us about localization of function
each region of the brain is associated with one function, but it is not “one does it all”, sometimes multiple regions are involved but one is more dominant
memory in the brain
cortex: long term memories
hippocampus: critical to memory formation
cerebellum: learning motor skills (riding a bike)
amygdala: processing of emotional memories
temporal lobe: includes hippocampus parahippocampal, entorhinal cortex, amygdala
study for localization
maguire
neuroplasticity
the brain is not static, it is constantly changing
if there is damage other areas of the brain can do those lost functions
new neural connections are made as a result of new experiences or learning, manipulable
A habit is a strengthening of the neural pathways. what we practice becomes easier each time
neural networks develop by making and break synaptic connections between neurons (pathways that can be changed)
neural pruning: increasing efficiency: neurons and synaptic connections no longer used are eliminated (happens in childhood)
neural branching: strengthens brain and extends networks of synapses the same way that muscles are strengthened
plasticity: the brain’s ability to alter its own structure (changed in body or environment)
dendritic branching: dendrites of the neurons grow in numbers and connect with other neurons. more connections, we remember more, the more we learn
cortical remapping: the brain can change its neural map
factors:
genetic or developmental (pre-programmed)
environmental (other people, new experiences)
study for neuroplasticity
draganski
drangaski
Draganski
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.
Procedure:
The participants for this study were 24
volunteers between the ages of 20 and 24. There
were 21 females and 3 males. All participants
were non-jugglers at the start of the study. Each
participants had an MRI scan at the start of the study. Participants were allocated to one of two conditions - the jugglers and the non-
jugglers. Those that were in the juggling condition were taught a juggling routine. At that point the jugglers had a second MRI
scan. After the scan, they were told not to juggle anymore, and then a third and final
scan was carried out three months later. The non-juggling group served as a control
group for the duration of the study.
Findings:
However, the jugglers showed a significantly larger amount of grey matter in the mid-
temporal area in both hemispheres - an area associated with visual memory. Three months after the participants stopped juggling - and many were no longer able to
carry out the routine - the amount of grey matter in these parts of the brain
decreased.
Application to the theory:
Juggling relies more on visual memory than on procedural or motor
Memories. Learning new skills creates new pathways, and then when we don’t rehearse, the pathways get weaker → neural pruning
Neurotransmitters
electrochemical process
action potential builds up, neurotransmitters are released from terminal buttons, go down the axon to cross the synaptic gap where they fit into receptor sites on the postsynaptic membrane
stimulates the next cell to the same
agonists: excite a neuron
antagonist: inhibit a neuron from firing
acetylcholine: muscle contraction, and a role in the development in the hippocampus MEMORY. may lead to paralysis or convulsions. deteriorating levels linked to Alzheimer’s. lots of acetylcholine receptor sites in the hippocampus
dopamine: voluntary movement, learning, feelings of pleasure. undersupply can lead to tremors, restless leg syndrome, Parkinson’s disease, oversupply may lead to schizophrenia
noradrenaline: arousal, fight or flight, anxiety, undersupply can affect mood
serotonin: sleep, arousal levels and emotion, mood balance, undersupply linked to depression
GABA: major excitatory neurotransmitter linked to memory, undersupply linked to seizures, tremors, insomnia
inhibitory neurotransmitters: stop impulse from firing and prevent electrochemical impulse from crossing the synapse, calming
excitatory neurotransmitters: increase likelihood of a neuron firing, generate a signal in a neuron, stimulate effect
antagonists and agonists balance each other, chemical harmony. medication can be used to alter the balance
study for neurotransmitters
Antonova
antonova
Aim:
to see if scopolamine affected hippocampal activity in the creation of spatial memory.
Procedure:
scopolamine is an acetylcholine inhibitor
acetylcholine plays a key role in the encoding of spatial memory
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.
Injected with either scopolamine or a placebo 70-90 minutes before the experiment.
put into an fMRI where they were scanned while playing the “Arena task.”
complex virtual reality game in which the researchers are observing how well the participants are able to create spatial memories
Have to navigate an arena with the goal of reaching 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.
Findings:
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.
Application to theory:
Study was usually done on rats, this was a replication on humans.
Acetylcholine is an essential neurotransmitter that is involved in spatial memory formation. Neurotransmitters are significant chemicals for memory.
Hippocampus is involved in the creation of spatial memories.
hormones
endocrine system: set of glands that secrete hormones directly into the bloodstream, chemical messengers
hypothalamus: links nervous and endocrine system (in the brain)
pituitary: master gland, controls the others (in the brain)
thyroid: regulates metabolism (in the neck)
ovaries/testes: sex hormones (genitals)
hormones help control mood, growth and development, the way our organs work, metabolism and reproduction
too much or too little impacts the body
some hormones can act as neurotransmitters, when needed for survival (serotonin or adrenaline)
adrenaline (adrenals): responsible for arousal and fight or flight. role in emotional memory formation
cortisol (adrenals): controls blood sugar levels, regulates metabolism, reduce inflammation and assists with memory formation
testosterone and estrogen (gonads): facilitated role in aggressive behavior
melatonin (pineal): signals relaxation and lower body temperature that helps with a restful sleep
oxytocin (pituitary and hypothalamus): plays a role in mother child attachment, social bonding and trust between people
hormones and memory
adrenaline: activates sympathetic nervous system (flashbulb memories)
cortisol: produced in adrenal glands, increases amount of glucose/fats/protein/carbohydrates, provides energy for fight or flight. affects hippocampus→ too much stress can make you forget
moderate levels of cortisol help in consolidation and retrieval of memories
high levels impair memory retrieval and can even lead to hippocampal impairment
hormones and love: oxytocin, the love hormone
produced in hypothalamus, stimulated by the pituitary gland. touches and hugs, encourages connections between people, affects women during pregnancy to bond with child
study for hormones
meaney
meaney
Aim:
To determine the effect of glucocorticoids (stress hormones) on memory.
Procedure:
independent sample design. The rats were randomly allocated to one of two conditions.
Newborn rats were handled daily by the researchers for three weeks - from the day of their birth until the day of weaning. During this time they were taken away from their mothers for 15 minutes and placed in a plastic container lined with a paper towel. They were then brushed for an intense 15 minutes to simulate the grooming of the mother rat.
The rats in the control group were taken away from their mother but there was no handling by the researchers. This group served as the control condition.
two-year old rats were put into a pool of milky water. In the pool was a platform. Meaney and his team tracked the route of the rats as they sought out the platform based on the rats’ memories of previous attempts to escape the water.
Findings:
high levels of glucocorticoids - stress hormones - in the early life of a rat resulted in changes that affected the rats in old age. Increased exposure to adrenal glucocorticoids accelerated hippocampal neuron loss and cognitive impairments in aging.
the rats taken away from their mothers and not groomed at a young age took a much more complicated and longer route to get to the platform.
Application to theory:
It appears that the extra stroking that the rats received led to an activation of genes which are responsible for the reaction to the stress response. This is an example of epigenetics - the grooming process “turns on” the genes which help the young rat cope with stress - which then leads to a longer and healthier life.
When the rat is stressed, stress signals travel from the hypothalamus to the pituitary gland and then to the adrenal glands. The adrenal glands then release the hormone cortisol. Cortisol is released from the adrenal glands and travels to the hippocampus, where it binds to glucocorticoid receptor sites. When cells in the hippocampus detect cortisol, which binds to the receptor sites, a message is sent to the hypothalamus that shuts down the Fight or Flight response.
Long term exposure to cortisol causes neurons to admit more calcium through channels in their membrane. This leads to over-stimulation which then leads to hippocampal cell death. This is a problem when it comes to our ability to create memory as the hippocampus is the location of acetylcholine receptor sites. Loss of hippocampal cells correlates with lower levels of acetylcholine. Research shows that there is a correlation between high levels of glucocorticoids, low levels of acetylcholine and Alzheimer’s.
pheromones
pheromones are not smells
a chemical substance produced and released into the environment by an animal (mammals, insects) that affects the behavior or physiology of others of its species
“ectohormones” chemical communication among members of the same species
aggregation of signaling pheromones that lead to mating behaviors
androstadienone (AND): derivative of testosterone, one of the chemical components of sweat
estratetraenol (EST): female version of AND, likely synthesized in ovaries
women have a more acute sense of smell, scent gives away genetic makeup of our immune system, evolutionary component
MHC: major histocompatibility complex - series of molecules that help immune system identify pathogens and activate immune response, everyone has a different MHC footprint
women can determine the MHC better → looking for an MHC different than your own for stronger immune system, evolutionary explanations
birth control and ovulation can affect how women detect MHC
