4 - Investigating the Brain Flashcards
describe structural brain imaging
knowing the physical components in the brain, where they are to describe structure in detail
disadvantage of structural imaging
may not know what the component is for
what does structural imaging help to localise
changes in white (myelinated axons) matter and grey (neurons)
describe functional brain imaging
knowing the roles of brain regions and how areas work together
define direct measurement
directly measuring electrical activity or consequences of the activity in the brain
examples of electrical activity measured
post synaptic potentials
action potentials
how does the cap in EEG collect electrical activity data
macroelectrodes detect minute electrical changes across scalp’s surface then eephalogram created
what do EEGs show about electrical activity
frequency (divided into EEG correlates) and location
what does alpha data represent
visual and mental effort
what does beta data represent
motor control changes, alertness, wakefulness, anxious thinking
what does gamma data represent
cognitions, neurons linking cognition and motor function
what does delta data represent
sleep
what does theta data represent
alertness
mental activity
advantages of EEGs
relatively cheaper
good temporal resolution as neurons firing detected instantly
non-invasive, comfortable for children to use
portable
disadvantages of EEGs
can’t measure deep-brain electrical activity
poor spatial resolution so can’t pinpoint areas
describe magnetoencephalography
SQUID sensor detects weak magnetic field of current produced by APs in axons of cortical surface of the brain to map active regions
direct methods
EEG
MEG
indirect methods
fMRI
PET
DTI
advantages of MEG
good temporal resolution
good spatial resolution for sperficial brain parts i.e. cortex
what are the general disadvantages of MEG
poor spatial resolution for deep brain
not portable
v expensive
have to put head in machine so uncomfortable
specific disadvantage for MEG
if sensor and magnetic field aligned incorrectly then info can be missed
define indirect methods
picking up signals indirectly related to action potentials
how do fMRIs work
go into a tunnel to measure changes in local blood flow, volume, O2 consumption
describe the haemodynamic response
o2 flooding to area where neurons fired to support it and levels dropping below baseline when neuronal firing stops
how do fMRI magnets work
magnet picks up differences in magnetic properties of de/oxyg blood
what does BOLD stand for
Blood Oxygen Level Dependent signal
what graph do fMRIs create
brain diagram w voxels
fMRI advantages
more powerful magnet so better spatial resolution
better spat res for deep/superficial regions
general disadvantages of fMRI
uncomfortable due to tunnel
poor temporal res as O2 flows 7 seconds after firing and drops 15 secs after firing stops
fMRI disadvantages related to the magnet
safety issues, e.g. pacemaker
more powerful means more expensive
noisy magnet movement so unpleasant and can’t do auditory research
fMRI disadvantage related to BOLD signal
not fully understood or its relation to neural activity
describe PET
radioactive tracer taken and goes to active parts of brain as tracer in blood
what happens after the PET tracer breaks down
positron released and moves into immediate env and collides w electron to produce a gamma ray which sensor picks up
PET advantages
better spatial res than direct
tracers specific to nts can be taken to allow specific nt system activity to be mapped
disadvantages of PET
invasive poor spatial res as gamma ray picked up not nt expensive biohazard can't use w kids, pregnant women
why does PET have a poor temporal resolution
relies on blood changes
describe diffusion tensor imaging
water molecules within axons diffuse in parallel direction to axon so can work out axon orientation and locations
what types of diffusion are there and what matter do they correspond to
free diffusion = grey
restricted diffusion = white
- of DTI
noisy
poor temporal res compared to direct
expensive
+ of DTI
better temp res than fMRI and PET
can measure brain/white matter maturation
only method to see pathway communication and which area active first
why is DTI more sensitive than MRI
decreased blood flow can be detected before neuronal death
how may animals feel in unfamilar environments and what can be done about this
nervous/stressed
acclimatise and have regular contact w experimenter
what can be difficult for animals being in an artificial environment
not around others and don’t live in a perfectly controlled environment, neither do humans
how may animals be incentivised
food but don’t incentivise humans w basic needs for tasjs
what’s not good about training animals lots
spontaneous things in humans may be over-trained in animals
what’s difficult about rat species
interspecific variation so not equally able/inclined to do tasjs
what is face validity with animals
are they exhibiting the right behaviours like humans would in that condition?
what is construct validity
does the animal have the same underlying pathology and nervous system changes as humans when better understanding a condition?
what does it mean when using prediction with animal models
thinking about if their improvements will be seen in humans using the same treatments
what is an open field test
put animal in a chamber, see what it does, where it is, movement speed, where it’s looking, usually by computers
disadvantages of open field trests
footage takes hours to analyse
data can be flawed and include repeated movement
what’s a morris water maze
underwater maze testing spatial learning/memory, e.g. Alzheimer’s treatment, seeing if they understand platform’s position relative to surrounding environment
what is impulsivity testing
after training, seeing if rat chooses to go left to get rewards immed or right, wait longer, get more rewards
what is an operant chamber
training a rat to concentrate, look for a light to come on and put nose in right box for reward - impulsivity test
what is a rat invasive procedure
make incision in skull to insert electrode and get measurements from desired area after putting under anaesthetic
define experimental ablation
destroying part of animal’s brain to observe subsequent behaviour
define lesion studies
creating a lesion and inferring the destroyed brain part’s function based on functions the animal can’t do anymore
difference between non-selective and selective lesions
n-s destroys all types of neurons, fibre, tissue in an area, but selective destroys neurons with specific neurotransmitters
what is a radio frequency/electrical lesion
using RF/elec to destroy tissue around electrode tip irreversibly but must create sham lesions
define sham lesions
carrying out a procedure without turning on the electrode to make a more valid comparison
define excitotoxic lesions
irreversibly removing cell bodies only by using kainic acid to excite cells to death by binding to glut receptors
excitotoxic lesion advantage
spares axons passing by and so preserves fibres
describe aspiration
irreversibly sucking out brain tissue from cortical regions
describe local anaesthetic
blocking all Na+ channels to prevent APs so activity in an area is suppressed irrreversibly
limitation of local anaesthetic
judging extent of suppression is hard as there’s no marker of how far it’s diffused
how do selective toxins work
soma taking up toxins so they’re transferred to axon terminals leading to cell death irreversibly
what is acute electrophysiology
taking recordings for a short amount of time
what is chronic electrophysiology
permanent implants needing amplifies due to the small signal which may be used for treatment introduction, learning tasks, etc.
what is intracellular electrophysiology
sharp instrument piercing a cell to record electrical activity inside
what is patch clamping
using an electrode to suck onto the side of the cell
what is extracellullar electrophysiology
recording electrical activity outside cell but may end up getting info from more than one cell
single and multi unit difference
single neuron activity vs multi neuron activity
describe microdialysis
tiny canula inserted into brain region to extract fluid for analysis where moleculres diffuse into dialysis fluid
what does microdialysis analysis involve
detecting neurotransmitters and their products
what is voltammetry
electrical markers of chemicals where release of chemicals causes a certain type of signal
evaluation of voltammetry
- expensive
+ can be sure amino acid excites only soma not axons as only soma affected
what is studied in post-mortems
glia:neuron and gross measures for different conditions calculated
visualise neurons by using stains
describe immunohistochemistry
selective labelling where a stain binds to a secondary antibody which is bound to a primary AB which is bound to a cell to see what cells/chemicals there are
toxins do what in immunohistochemistry
bind to antibodies which bind to specific proteins and so kill specific cells
describe tract tracing
anterograde tracers are taken up by dendrites then released at synapses or retrograde tracers are taken up by axon terminal and travel to soma
in tract tracing, what method of identification is used
using fluroescent tagging
describe transneuronal tracing
infecting cells w a virus then releasing it to infect other cells which infected cells has formed synaptic connections with to see pathways
limitations of tract tracing
need to determine if observation is an action potential or post-synaptic potential
retro/anterograde tracers identify single neuronal chain only
