neuroscience - imaging Flashcards
describe the clinical or neuropsychological assessment for studying the brain
- non invasive
- correlates impairment of function with damaged area of the brain
- diagnosis, understanding nature of brain injury, measuring change over time
describe stimulation methods for studying the brain
- invasive
- electrical current briefly applied to part of brain to study effect
- patients describe subjective experience
- roles of speech and language areas have been identified
describe brain imaging to study the brain
- imaging techniques show relationship between brain structures and their functions
describe the process of electroencephalography
- electrodes on scalp detect voltage fluctuations in the brain
- signals recorded by machine and observed by doctor
- allows monitoring of the depth of anaesthesia during surgery
- provides information about normal electrical activity
what are the advantages of using an EEG scan
- non invasive
- cheap
- fast
what are the disadvantages of using an EEG scan
- not exact as it is hard to figure out where the electrical activity is coming from in the brain
describe the process of a computerised tomography scan
- many x-ray images taken from different angles and combined
- x-rays from beams detected after passing though the body and their strength measured
- less dense tissue produces strongest beams
- can detect tumours, brain injuries and blood clots…
what are the advantages of using CT scans
- more detailed information
- more readily available in the UK than MRI scans
- whole. body scan can be done in seconds
what are the disadvantages of using CT scans
- involves doses of radiation
- very expensive
- requires cooperation or sedated patients
describe the process of a magnetic resonance imaging scan
- uses strong magnetic fields to align protons in water molecules
- monitored as they move through following a pulse of radio waves
- produces detailed images of soft tissues and organs
what are the advantages of using MRI scans
- no ionising radiation involved
- no known side effects
- non invasive
- better soft tissue contrast that CT
- 3D data
what are the disadvantages of using MRI scans
- very expensive
- cannot scan patients with metallic implants
- unsuitable for claustrophobic or obese patients
describe how an MRI scan may be used to assess brain damage.
- patients head placed in magnetic field
- computer measures differences in strength of magnetic fields
- computer produces images of internal structure of brain
- images show slices of the brain
- areas of brain respiring
- little respiration in areas that are damaged
what are the advantages of fMRI scans
- no ionising radiation
- no know side effects
- non invasive
- better soft tissue contrast that CT scan
- 3D data
what is the process of a positron emission tomography scan
- injection of small amount of radioactive isotope
- shows use of radioactive glucose in 3D map of brain
- active areas release more radioactive glucose so show as yellow and red
- can detect biochemical changes in the brain before anatomical changes occur
what are the advantages of using a PET scan
- usually painless
- helps diagnose, treat or predict outcomes for a range of conditions
- shows how different parts of the body work and can detect problems early
what are the disadvantages of using a PET scan
- exposure to gamma rays
- radioactive materials can cause reactions in some people
- scanners can cause people to feel claustrophobic
define neuroplasticity
brains ability to change and adapt over time by forming new connections between neurones
define developmental plasticity
neurones in the young brain rapidly sprout branches and form synapses
why is the critical period important
- brain must receive certain sensory inputs in order to develop properly
- when this period has ended it becomes hard to learn new noises
what is synaptic pruning
- large drop in number of connections after critical period ends
- ones that remain are the ones used the most
- occurs during adolescence
what is epigenetics
study of chemical reactions that can turn genes on or off and the factors that influence them
what is cortisol
hormone released from the adrenal glands in response to stress
outline the stages of cortisol production
- production controlled by hippocampus
- when stressed, the hippocampus sends impulses to the hypothalamus, which releases corticotrophin-releasing hormone and arginine vasopressin
- these hormones stimulate the pituitary gland which then releases adrenocorticotrophic hormone into the blood
- cells of adrenal glands release cortisol when they take up this hormone
what is the process of cortisol production an example of and why
- negative feedback
- as cortisol circulates in the bloodstream it binds to glucocorticoid receptors in the hippocampus, which responds by sending impulses to the hypothalamus, inhibiting it
- this stops us from being constantly overstressed
what does it mean about the feedback loop when adults who have had a traumatic childhood and are consequently stresses produce too much cortisol
the negative feedback loop is not working and they could have fewer receptors or release more hormone leading to higher cortisol production
