Neurotransmitters are chemical messengers that your body can't function without. Their job is to
carry chemical signals (“messages”) from one neuron (nerve cell) to the next target cell.
Agonists - all neurotransmitters are agonists. This is because agonists are chemicals/drugs that bind
to receptors in the brain and cause a reaction. neurotransmitters are agonists that occur naturally in
the body, but there can also be synthetic agonists in the form of drugs
antagonists - it is a chemical/drug that will bind to a receptor and prevent a neurotransmitter from
causing an effect on the brain - it blocks the action of another neurotransmitter. so, scopolamine is an
antagonist for acetylcholine
inhibitory - it decreases the likelihood that a neuron will have an action potential. It differs from
antagonists because it does not decrease the action of another neurotransmitter, it itself reduces the
action potential of a neuron.
Antonova - blocking acetylcholine receptors can affect 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. They were injected with either Scopolamine or a placebo.
- The participants were then put into an fMRI where they were scanned while playing the
"Arena task.“
- This is a rather complex virtual reality game in which the researchers are observing how
well the participants are able to create spatial memories
- The goal is for the participants to navigate around an "arena" with goal of reaching a
pole. After they have learned where the pole is located,the screen would 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 researchers found that the scopolamine group took longer on average to find the
pole in the arena. In addition, they found that the scopolamine group demonstrated significant
reduction in the activation of the hippocampus compared to the placebo group. It appears that
acetylcholine plays a key role in the encoding of spatial memories in humans, as well as in rats.
Kasamatsu and Hirai - Serotonin and monks
- To see how sensory deprivation affects the brain
- Studied a group of Buddhist monks who went on a 72-hour pilgrimage to a holy mountain in
Japan.
- Monks did not consume water or food; did not speak and were also exposed to cold weather.
- Researchers took a blood sample before monks ascended into the mountain and immediately
after they reported having hallucinations
- After about 48 hours, monks began to have hallucinations, seeing ancient ancestors or feeling
their presence by their sides.
- They found that serotonin levels had increased in the monks' brains thus the higher levels of
serotonin activated the hypothalamus and frontal cortex resulting in hallucinations.
- Researchers concluded that sensory deprivation triggered the release of serotonin, which
altered the way that the monks experienced the world, a behavior expressed by humans.
Roger’s and Kesner - rat version of antonova
, - role of acetylcholine in spatial memory
- let rats familiarize themselves with maze, and then gave them either scopolamine or
placebo, and made to do maze again.
- found that rats with scopolamine took longer and made more mistakes
- it is reductionist, it does not take into account the complex processes and
consolidation of memory, and does not give good explanation for the exact
mechanism of the neurotransmitter.
- human generalizability
Porges - GABA Inhibitor
- looked at GABA concentrations in frontal lobe of old people without history of
dementia. the participants had to take a cognitive assessment task to test their
cognitive functioning.
- researchers found correlation between higher GABA conc. in frontal lobe and
superior cognitive performance
- GABA inhibits neural activity in hippocampus and frontal lobe. this inhibition of neural
activity allows us to increase cognitive load and helps us focus. more GABA, more
inhibition of activity, more attention. low GABA levels allow intrusive thoughts to
prevent proper, undivided attention
Lateralization
Lateralisation is the idea that the two halves of the brain are functionally different and that each
hemisphere has functional specialisations, e.g. the left is dominant for language, and the right excels
at visual motor tasks
Sperry - A SPLIT-BRAIN PATIENT
- cutting corpus callosum – 2 hemispheres become functionally separate
- in epilepsy – lots of nervous impulses spreading from one place in brain to rest of the brain
- word shown on left side is seen only by right hemisphere – it's easy to pick it from a pile of
things by left hand, but impossible to say what it is (no information to left H)
- words shown on both sides (HE+ART) – able to name the word ART, but left hand points word
HE on a card (from words he and art) – not able to put those words together HEART
- it's a proof that left hemisphere is responsible for language
Localization
We can define the localisation of function in the brain as the idea that different areas of the
brain are responsible for specific functions.
Maguire
- It appears that the posterior hippocampus is involved when previously learned spatial information is
used, whereas the anterior hippocampal region may be more involved during the encoding of new
environmental layouts.
- The aim of the study was to see whether the brains of London taxi drivers would be somehow
different as a result of their exceptional knowledge of the city
- The taxi drivers were compared with the MRI scans of people who did not drive taxis.
- There were two key findings of the study. First it was revealed that the posterior hippocampi of taxi
drivers were significantly larger relative to those of control subjects and the anterior hippocampi
were significantly smaller. The volume of the right posterior hippocampi correlated with the amount
of time spent as a taxi driver.
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