neuromethods Flashcards
what is temporal resolution?
gathers information on changes in neuronal activity that occur over time
brain state changes on a millisecond basis
what is good about temporal resolution in brain scans?
give accurate representation of changes in the brain
why is it important to chose a region of interest?
the strucutre of a certain area of the brain may underlie the function interested in
help design method and task for study
if not chosen, have to use a more conservative statistical test to prevent false positives - more likely that changes are due to chance
what scans determine location?
CAT
MRI
TMS
Leison studies
what scans determine function?
PET
FMRI
NIRS
What scans look at nerve cells?
single cell recording
EEG
ERP
MEG
what does CAT stand for
computerised axial tomography
how does a CAT scan work?
Produces 3D image of brain by rotating high energy electromagnetic beam
absorbed by brain tissue
denser tissue absorb less x rays and produce a lighter image ie CFS darker
detectors measure amount of absorbtion
what are the advantages of CAT scans
used on almost all individuals
Describe winter mark et al 2004 CAT
wintermark et al (2004)
- found highest regional cerebral blood flow (rCBF) at age two in grey matter - how childs brain develops
what are the disadvantages of CAT scans
x rays
low spacial res
no info about temporal changes
hardly used now - more improved techniques
what does MRI stand for
magnetic resonance imaging
how does an MRI scan work?
Apply mag field (static field)
- orients position of nuclei in brain ie protons in hydrogen
Apply pulse sequence and disturb mag field -
Cause to orient 90 away from field and produce mag moment - emit signal detected by radio antennae
Locate signal using gradient field
- subtly change strength of mag field over diff areas
- subtle diff received produces image
define static field
magnetic field of high strength
atoms orient in same direction
imagers classified by strength
define pulse sequence
mag field applied then removed consistently
Op
define gradient field
mag field varying in intensity over an area of the brain
localises points from which the signals are emanating
what are the types of MRI
T1 weighted
T2 weighted
Diffusion tensor imaging
Fractional anisotropy
what is T1 weighted image mri used for
show progress of demyelinating diseases such as multiple scelrosis
fat bright and water/csf dark
images brain tissue
what is T2 weighted image mri used for
gives density map of the brain
water/csf bright and fat dark
images lesions filled with csf
what is diffusion tensor imaging used for
determines the direction that fluid can travel - structural anisotropy of fluid
flow through axons
what is the difference between isotropy and anisotropy
isotropy - no preffered direction for diffusion ie balloon, anisotropy - preffered set direction for diffusion
what is fractional anisotropy
describes the degree of anisotropy of a diffusion process
myelin increases flow across an axon
an indicator of myelination and axonal thickness
what are the advantages of the mri scan
precise imaging with high spacial res
can map different substances
non invasive
less dangerous than CT
what are the disadvantages of MRI scans
poor temporal res
cant use if have metal in body ie pacemakers
can induce phobias
difficult in young - keep still
Describe Nagy, westberg and klingberg 2004
DTI to determine FA in 8-18y
FA indicate axonal thickness and mylination
FA pos correlate with wm in x2 areas in left temp lobe
Reading only corr with left temp in region associated with reading disabilities in adults (lower FA)
- white matter maturation assoc with cog Dev in late childhood
- FA not sig when effect of age removed - behaviour and FA assoc dependent on age
what does PET scan
positron emission tomography
how do PET scans work
looks at brain function and amount of diff substances in the brain
inject pp with radioactive glucose tracer ie flurodeoxyglucose
glucose used in metabolic activity - level in brain indicates level of activity/blood flow
make pp perform cog task linked to specific function
radioactive tracer releases positrons which travel away from site a 180
determine site of activation by detecting protons arriving at diametrically opotsite detectors
advantages of PET scan
better spacial than EEG/ERP
better temp - changes relate to specific performed behaviours
assess many aspects of functions
disadvantages of PET scan
not good enough spacial to identify individual neurons
temp limited - detect regions of activation
radiation
temp time changes relatively large - not fast enough
require onsite aylotron to create radioisotroped - costly
What studies use PET scans
female monkeys who become dominant showed a significant increase in dopamine (DA) D2-like receptor availability compared to subordinate animals who showed significant decreases in DA transporter (DAT) availability. in males, higher D2-like availability was associated with greater vulnerability to cocaine reinforcement (Nader et al. 2012)
Happé
Look at attribution of mental states ‘theory of mind’ in patients with Aspergers
No task activity relating to ToM task in left medial prefrontal cortex
Crucial for understanding own and others beliefs
how does an fMRI scan work
high powered rapidly oscillating mag field gradient detects small changes in brain metabolism - changes in oxygen
haemoglobin in blood is magnetically charged and mri detects the changes of this
what studies have used fMRIs?
Hasler et al 2008 - failure to obtain pleasure from activities can act as a biomarket for illness - onset of depression - ahedonia
McCabe et al 2012 - 15 recovered depressed and matched controls given chock and milk or mouldy fruit and water - recovered have reduced response to choc compared to controls and increased response to aversive fruit
risk factors of depression
previous history or family history
childhood adversity
neg life events
lack of social support
advantages of fMRI
higher spacial and temporal than PET
map different substances
non invasive
disadvantages of fMRI
cant use if have metal in body
induce phobia
difficult with children
temp poorer than EEG/ERP
what does NIRS stand for
near infra red spectroscopy
how do NIRS scans work
detects the activity of neurons
pulses of near infrared light penetrates the skull and tissue immediately beneath
optical sensor detects protons reflected back through the skull
spcial res limited to 3cm
what types of NIRS is there
slow signal - detects changes in blood flow to diff areas in the brain in the time course of seconds
fast signal - detects physiological changes associated with activity
advantages of NIRS
good spacial and temp res
non invasive
portable
disadvantages of NIRS
pooerer spacial than fMRI
only records brains surface
studies using NIRS
negaro et al
nirs used to examine the prefrontal cortex in 6-13 year olds with adhd
adhd show decrease in oxyhaemoglobin and increase for control in inferior lateral pfc
advantages of NIRS
non invasive
cheap
portable
good temp res
disadvantages of NIRS
spacial resolutoin only 3cm
only detects the brains surface
what does EEG stand for
electroencephalogram
how do EEGs work
electrodes on the scalp are used to pick up sponateous electrical activity
records many located simultaneously
measures activity of a population of neurons firing together creating a change in electrical polarisation
wha are the frequency bands detected by EEGs
Gamma - 30 Hz, long range, neurally synchronised
Beta - 15-30 Hz, involved in motor acitivty, concentration and alertness
Alpha - 7-14 Hz, involved in relaxation, tiredness and attentional lapses
Theta - 4-7 Hz, drowsyness
Delta -
what are the differences in brian acitivity during sleep compared to when awake
sleep - less active, many neurons active together, large amplitudes and slow changes in activity
awake/relaxed - more active, small amplitudes and fast changes in activity
what are the stages of sleep
relaxed wakefulness theta sleep spindles and k-complexs delta REM/deep - EEG look at sleep disorders and study consolidation of learning during sleep
studies using EEG
mormann et al 2000
eeg diagnose and monitor epilepsy and range of clinical disorders ie
migrnes, parkinsons, psychiatric and brain death/comas
advantages of EEGs
provides info on the general state of an individual
temporal changes at high res
non invasive
disadvantages of EEGs
poor spacial - pass through tissues before can measure, and diff parts have diff conductivity, nearby neurons strongly correlate
doesnt show specific responses to stimuli
why is it beneficial to study human leisions
allow us to study how different parts of the brain impact our behaviours
show up white or black dependent on where and the density and what it is filled with - csf or blood etc
describe the case study of patient HM and how he has influenced our understanding
had hippocampus removed to remove epilepsy
leision in bilateral temporal lobe
caused severe anterograde amnesia - cant form new memories, affect stm - forgot daily events, new peoples names etc
help to understand and form fundamental principles of memroy ie stm and ltm
identify memory as a distinct and seperate function
describe the case study of patient HD and how he has influenced our understanding
mestry et al 2014
no N170 which causes electrophysiological response
had difficulties recognised faces BUT can identify queen/obama
use other features to identify
leision in temporal lobe
what types of stroke are there
ischemic
starvation of oxygen ie blood clot
haemorragic
hbp cause burst of bloodvessel where blood builds up then leaks
decribe the case study of patient HJA
riddoch and humphreys 19987
bilateral lesions in inferior temporal lobe by stroke causing inability to recognise visually presented objects
can describe from memory but not recognise when shown
use logic to resolve
ie said bird was cat, own was a pattern and bug was a rhino due to hard shell
describe the case of patient SM
freinstein et al 2013
bilateral amgydala lesions due to urbach luiethe disease
minimal fear response
advantages of human lesions
evidence for functional dissociations
disadvantages of human lesions
lesions affect more than one neuronal network so cant link to specific area
cant compare to before leision
difficult to draw conclusions from case studies
cant pick who gets leison
connections modified after incident due to plasticity and replace old function
why is it beneficial to use anumal lesion studies
can deliberately create a lesion in the brain
use precise positioning using sterotaxic equiptment and coordinates of the brain
how can you create lesions in animals?
aspiration/ablation - remove surface of cortex
radio freq - electrode inserted into specific location and tip heated to destroy nearby cells
neurotoxins - ie ibotenic acid, inject into specific region, destroy cell bodys but maintaining fibres
what studies have used animal lesions
kluver-bucy 1939
radiofreq lesion in rats cause reduced freezing behaiour to cats and to conditioned threat stimuli
- amyg involved in hyperemotionality, fear and anger
advantages of animal lesions
evidence of functional dissociations
can do what cant in humans
precise
large samples
disadvantages of animal lesions
generalise to human functions
can damage other areas- interlinking paths
brain plasticity and modification
what does TMS stand for
trancranial magnetic stimulation
how does TMS work
electric current flows through coil inside and produces a magnetic field
mag field depolarises corticle neurons lying perpendicular to the coil
inhibits activity and produces a temporary lesion
allow to identify brocca area for speech production
studies using TMS
pitcher et al 2007
applying tms to optical face area does not disrupt house related stimuli
o’reardon et al 2007
5x a week at 3000 pulses for 4-6 weeks on DLPFC shows reduction in depression symptoms
slotema et al 2012
reduce hallucinations in schizophrenia
advantages in tms
good spacial temp increase precision using equiptment - tracker and pointer evidence for functional dissociations reversible eliminate subject confounds big sample
disadvantages of TMS
limited to cortical regions
possible side effects
how do single cell recordings work
glass or metal electrodes inserted into area of interest using stereotaxic methods until neuron is located
measure inside or extracellular fluid outside neuron
take baseline recording then present stimuli and record the activity - excitatory or inhibitory
can show the receptive field of a neuron - responds to appropriate stimuli and partially determines function of cells ie on-off retinal ganglion cells respond to light if centre of receptive field but inhibitory if peripheral
studies using single cell recordings
quiroga et al 2005
response pattern to faces and buildings in humans undergoing epileptic surgery
some neurons respond exlusively to certain people
advantages of single cell neuron
temp change at high res
exact stimulus and response
disadvantages of single cell
animals and limited human
bias selection of neurons
no info on networks
no long term
describe optogenetics
photosensory molecules convert light to electricity
use gene therapy to put photosensory molecules onto specific neurons
shine light to turn on/off neuron in those cells
blue light -excitatory yello light - inhibitory
how does blue light influence optogenetic cells
channelrhodopsin receptor opens when exposed to blue light
sodium enters channel and cause depolarisaion
how does yellow light influence optogenetic cells
halorhodopsin receptor pumps chloride into neuron when exposed to yellow light causing an inhibitory resonse
what studies have used optogenetics
hsing-chen et al 2009
dopamine producing neurons give ride to reward and pleasure
mice spend more time to areas where recieved speicifc frequencies leading to specific bursts of dopamine acitivty
yellow light on amygdala cause reduced fear response and wonder into novel open spaces - run away when turned off
what possibilities does optogenetics hold
understand and treat brain disorders
help vision
advantages of optogenetics
manipulate neural responses
info on temp at high res
disadvantages of optogenetics
only animals
new science
invasive
what does ERP stand for
event related potential
how do ERPs work
uses EEG to record activity in brain related to a specific stimuli
requires groups of neurons to respond simultaneously
repeat stimulus many times and average out response recordings - maintains the signal
negative voltage plotted up and positive down
How does ERP work
Measures gross potentials evoked by discrete stimuli
Average EEG waveform to obtain reliable estimate
Random signals averaged out - if doesn’t occur simultaneously
What is unique about the ERP waveform
Neg spike UP
Pos spike DOWN
Define sensory components of ERP
Occur 0-100ms after stimulus
Occur in primary cortices
Associated with sensory processing
What is N1 and P2 in ERP
Occur 100-300ms after stimulus
Associated with selective attention
What is mismatch negativity ERP
Occur 200 - 300ms after stimulus
When stimulus deviates from what is expected
What is P3 ERP
Occurs 300-800ms after stimulus
Associated with memory update and info processing
What must be monitored in ERPs and what do you look for
Monitor differences between participants
Look for differences in amplitude (up or down) and latency ( time delay- wave move left to right)
What do ERPs investigate
Face processing is N170 wave and Po7 electrode Semantic processing Memory, learning Motor tasks Attention
Describe miltner et al 2000 ERP
Look at phobias
P3 increases when exposed to fearful stimuli in phobics - enhanced fear processing
Describe mathanon et al 2000 ERP
Look at schiz and ERP
Schiz have reduced P3 waveform
Acts as bio marker
May be due to reduced info processing
-change in waveform indicates psychotic disorders
Advantages of ERP
Gather info on activity in relation to specific stimulus/process
High temp
Non invasive
Disadvantages of ERP
Poor spacial
- can’t pinpoint area responsible for change that occurs
what does ERP stand for
Event related potential
What does MEG stand for
Magenetoencephalogram
What do MEGs measure
Measures mag fields generated when group of neuroma fire simultaneously
How do MEGs work
Mag shielded room
Place in helmet with 160 SQUIDs
Measure moment by moment changes in brain activity
Mag field changes dep on area and activity
What is a SQUID
super conducting quantum inference detectors
Advantages of MEGs
Link to specific stimulus
High temp res
Determine specific responses
Same oscillatory function as EEG
Non invasive
Disadvantages of MEG
Poor spacial
- mathematically map to source
More accurate than EEG
need simpler models for mapping
Describe cheng et al 2008 MEG
Recog fMRI not detect signal changes when observe pain of others - in primary somatosensory cortex
MEG whilst show painful/non painful images
- 10hz oscillations suppressed for both indicating use of primary somatosensory
- painful image = greater suppression
Perception of pain in others (empathy) modulates neural activity in primary somatosensory
fMRI cannot detect subtle diff in activity
Describe ushida et al (2001) CAT
- link between diabetes and brain atrophy in elderly
- temporal horns sig. larger than control
- insulin treated had widest temporal horns
Describe weinberger 1984 CAT
Proposed CAT used on patients when Show confusion/dementia First episode psychosis/personality/affective disorder Anorexia nervosa Prolonged Catalonia
What is theory of mind (happé PET)
Ability to attribute mental states to self and others
Ie beliefs intents and desires
Prev assoc with activity in left medial prefrontal cortex
