Health Neuroscience & Confounds Flashcards
HEALTH DEFINITION
- absence of physical/mental illness & disease/pain/discomfort
- absence of risk factors ie:
1. PHYSIOLOGICAL (ie. insulin resistance)
2. SOCIAL (ie. loneliness)
3. COGNITIVE (ie. slow processing speed)
4. EMOTIONAL (ie. anxiety)
HEALTH NEUROSCIENCE
- focuses on understanding how brain affects our physical health & vice versa
- brain = target (bottom-up pathways) & mediator (top-down pathways)
CONTEXTUAL INFLUENCES - social; cultural; environmental
- interventional; health policy
INDIVIDUAL-LVL INFLUENCES - genetic; epigenetic; life history
- well-being scale = resilience; clinical illness scale = risk
BRAIN HEALTH (WHO)
- state of brain functioning across cognitive/sensory/socio-emotional/beh/motor domains
- allows person to realise full potential over life course irrespective of presence/absence of disorders
- structural/functional integrity of brain regions underlying cognitive processes implicated in adherence to health behs
BRAIN BASICS
- BRAINSTEM & CEREBELLUM
- LIMBIC SYSTEM & SUBCORTICAL REGIONS
- WHITE MATTER TRACTS
- CEREBRAL CORTEX
BRAIN ROTATIONS
- (right) front -> back = anterior -> posterior
- (left) front -> back = rostral -> caudal
- width = lateral -> lateral (medial)
- top -> bottom = dorsal -> ventral
- diagonal -> rostral -> caudal
BRAIN APPROACHES
BRAIN PERTURBATION APPROACH
- manipulation
- alteration -> measure (task performance)
NEUROMONITORING APPROACH
- measurement
- manipulate cognition -> measure (neural activity)
EXECUTIVE FUNCTIONS
- predict physical/mental health across lifespan
- higher order cognitive functions implicated in “top-down” control of human beh/thought/action
- aka: executive processes/control; controlled attention; central executive system; supervisory attentional system
EXECUTIVE FUNCTIONING SKILLS
EMOTIONAL CONTROL
- ability to manage feelings
TIME MANAGEMENT
- ability to manage time to complete tasks
FLEXIBILITY
- ability to modify/adapt to changing situations
ORGANISATION
- ability to develop systems to manage
TASK INITIATION
- ability to start/stop tasks
WORKING MEMORY
- ability to use memory to complete tasks
HOW TO DEFINE EXECUTIVE FUNCTIONS
- conscious control of what we think/do
- enables self-regulation of one’s own social actions/display emotions
- coordinates goal-setting w/planning required to accomplish goal/task (ie. organising/sequence/self-monitoring/evaluating)
- control of attention/focus skills
- ability to think/act in flexible manner w/tolerance for frustration
EMOTIONAL ASPECTS OF EXECUTIVE FUNCTIONS: SELF-REGULATION
- impulse control
- use of social filter
- self-monitoring social behs
- tolerance
- delay of immediate gratification
- establishing/filtering attention
- engaging in health protective behs
COGNITIVE ASPECTS OF EXECUTIVE FUNCTIONS: META-COGNITION
- organising time/materials/projects
- prioritising
- attention shifting
- risk-assessment
- informed decision making
- verbal/non-verbal WM
STRUCTURE OF EXECUTIVE FUNCTIONS IN ADULTS
updating (specific) ->
shifting (specific) ->
inhibition ->
common executive function
EXECUTIVE FUNCTIONS & COGNITIVE MECHANISMS
- executive function & self-regulation skills depend on 3 cognitive mechanisms:
1. WORKING MEMORY - governs our ability to retain/manipulate distinct info over short periods of time
2. COGNITIVE FLEXIBILITY - helps us to sustain/shift attention in response to dif demands & apply dif rules in dif settings
3. INHIBITORY CONTROL - enables us to resist impulsive actions/responses
WORKING MEMORY
ADULT
- remember multiple tasks/rules/strategies that may vary by situation
5-16Y
- ability to search varying locations; remember where something was found; explore other locations
4-5Y
- appearance = NOT always reality
3Y
- hold in mind 2 rules & act on their basis
9-10M
- execute simple tasks/plans
7-9M
- ability to remember unseen objects
INHIBITORY CONTROL
ADULT
- consistent self-control; situationally appropriate responses
10-18Y
- self-control (ie. flexibility switching between central focus) & peripheral stimuli
7Y
- learning to ignore irrelevant peripheral stimuli & focus on central
4-5Y
- reductions in perservation; delay eating treat; begin to hold/follow arbitrary rule
9-11M
- inhibit reaching for immediate reward
8-10M
- maintain focus despite distractions
6M
- rudimentary response inhibition
COGNITIVE FLEXIBILITY
ADULT
- revise actions/plans in response to changing circumstances
13-18Y
- accuracy when switching focus & adapting to changing rules
10-12Y
- adapts to changing rules even among multiple dimensions
2-5Y
- shifts actions according to changing rules
9-11M
- seek alternative methods to retrieve objects beyond directly reaching
EF x FOOD INTAKE
- executive functions = associated w/calorie dense food intake in young adults
- n = 5648; 11-12y
- individuals w/higher executive functions:
1. consume less calories in lab taste tests
2. have lower body mass indexes (BMI)
3. consume more fruit/vegetables & less calorie-dense foods - sugar sweetened beverage consumption
- snack food consumption
EFFORTFUL CONTROL OVER DIETARY BEHS & CRAVINGS
- high calorie > low calorie; n = 7
- ultra-processed calorie dense foods = rewarding
- requires effortful control over reward processes to manage intake in “obesogenic” environments
PREFRONTAL CORTEX
- primary motor cortex (BA4)
- premotor cortex (BA6)
- anterior premotor cortex (BA8)
- dorsolateral prefrontal cortex (BA9/46)
- lateral frontopolar cortex (BA10)
- ventolateral prefrontal cortex (BA47/45/44)
- ventral anterior premotor cortex (BA44/6)
EXECUTIVE FUNCTION: SUMMARY
- executive functions = cognitive processes that can be used as proxy of brain health
- important for regulating beh; play key role in adherence to health beh
IMAGING TECHNIQUES
ANATOMICAL
FUNCTIONAL
ANATOMICAL STUDIES
- structure evaluated w/dif groups/diagnoses (aka. keep other variables as similar as possible) or same group over time
- measure structure
FUNCTIONAL STUDIES
- task needed w/recordings taken during task
- usually compared to baseline task
- measure function (aka. needs to have task)
STRUCTURAL METRICS
GREY MATTER
- neuronal cell bodies (neurons)
WHITE MATTER
- myelinated axons
NEURON ANATOMY
- dendrite
- nucleus
- cell body (soma)
- Scwann cell
- axon
- myelin
- axon terminal
IMAGING TECHNIQUES: ANATOMICAL & STRUCTURE
- X-Ray
- X-Ray computed tomography (CT)
- ultrasound
- magnetic resonance imaging (MRI)
IMAGING TECHNIQUES: FUNCTIONAL
- nuclear medicine (SPECT/PET/PET-CT)
- MEG/EEG
- functional near-infrared spectoscopy (fNIRS)
- magnetic resonance imaging (MRI)
SEJNOWSKI (2014): SPATIOTEMPORAL DOMAIN OF NEUROSCIENCE METHODS
- EEG/MEG = brain (milliseconds)
- PET imaging = brain (hours)
- fMRI imaging = brain (minutes)
- TMS = brain (seconds)
- VSD imaging = brain (milliseconds)
- brain lesions = nucleus (days)
- 2-DG imaging = nucleus (hours)
- microstimulation = nucleus (seconds)
- light microscopy = layer (minutes)
- optogenetics = layer (seconds)
- field potentials = layer (milliseconds)
- single units = neuron (milliseconds)
- electron microscopy = synapse (minutes)
- calcium imaging = synapse (seconds)
- patch clamp = synapse (milliseconds)
FMRI: WHAT ARE WE MEASURING?
- BOLD contrast; increase in local MR signal
- increase coherent spin in H nuclei of diffusing H2O ->
- displacement of deoxyhaemoglobin (glucose/blood flow/oxygen) ->
- ATP consumption by neurons/astrocytes ->
- integration/signalling in neuron groups ->
- sensory/motor/cognitive processes
BODY = TINY MAGNETS (WATER!)
- hydrogen atoms = tiny magnets
- put them in strong magnetic field; shift to align w/said field
HEMODYNAMIC RESPONSE
- neurons require energy to function
- cellular respiration requires oxygen/glucose
- local increasing blood flow
NEUROVASCULAR COUPLING
- electrical activity in neurons
- astrocyte/interneuron response
- dilation of arterioles
- increase in blood flow (CBF) & volume (CBV)
PHYSIOLOGY: BOLD CONTRAST
- blood-oxygenation-lvl-dependent contrast
SPATIAL RESOLUTION: VOXELS
- voxel = small rectangular prism; basic sampling unit of fMRI
- typical anatomical voxel = 1.5mm^3
- typical functional voxel = 4mm^3
ACTIVE BRAIN REGION = WHAT?
- brain has constant supply of blood/oxygen; we’d die without it
- aka. we cannot literally read thoughts via scanners as whole brain = active
- SO we need a contrast (ie. active compared to… what?)
FMRI: SUMMARY
- maps whole-brain; non-invasive
- validation against electrocortical stimulation/Wada performed for motor mapping/lateraisation of language
- active = NOT always essential!
- fmri = statistical; evaluating relative activation; requires intact neurovascular coupling
- pathology can abolish BOLD activation; tumours reduce/remove BOLD signal
FMRI SCANDALS
- dead salmon
- cluster failure
- voodoo
- analysis pipelines
- reproducibility
FMRI SCANDALS: DEAD SALMON
BENNETT ET AL.
- neural correlates of interspecies perspective taking in post-mortem Atlantic salmon; argument for multiple comparisons correction
FMRI SCANDALS: CLUSTER FAILURE
EKLUND, NICHOLS & KNUTSSON
- why fMRI inferences for spatial extent have inflated false-positive rates
- rsfMRI from 396 controls w/task design split into smaller groups
- random group analysis to evaluate false positives
- SPM/FSL/AFNI & nonparametric permutation
- FWI rate 5%; parametric stats conservative for voxelwise inference & invalid for clusterwise inference
- up to 70% false positives
- nonparametric more robust
FNIRS
- functional near-infrared spectroscopy
- haemodynamic approach (like fMRI)
- uses properties of light
- dif haemoglobin species can be detected due to difs in optical absorption
- light travels through skull; refracts back to detectors; used to calculate temporal changes in cerebral blood flow
PET: WHAT CAN WE MEASURE?
- metabolism (ie. oxygen & glucose)
- blood flow
- neurotransmitter systems (ie. receptors, neurotransmitters & enzymes)
VS: FMRI
- blood oxygen concentration
- no radioactivity
- temporal resolution = 1-4sec
- spatial resolution = 1mm
- event-related/blocked design
- some regions = difficult to image (near sinuses)
- medium £
- 65-130dB
- no metal
- minimal movement
VS: PET
- blood volume
- radioactivity (radioactive tracer)
- temporal resolution = 30sec
- spatial resolution = 10mm
- blocked design
- whole brain
- pharmacological tracers
- high £
- little movement
VS: FNIRS
- no radioactivity
- temporal resolution = ms
- spatial resolution = mms (BUT ltd to cortex)
- low £
- can move; portable
EEG: EVENT RELATED POTENTIALS (ERP)
- waveform from EEG reflects across brain activity (aka. current task & more); low signal-to-noise ratio; need lots of trials
- amount of voltage change associated w/cognitive event
- ERP like RT; time = important
- important = timing/amplitude of peaks for cognition
EEG: FREQUENCY BANDS
DELTA
THETA
ALPHA
BETA
GAMMA
EEG: DELTA FREQUENCY BAND
FREQUENCY
- .5-4Hz
AMPLITUDE
- 100-200uV
LOCATION
- frontal
ACTIVITY
- deep sleep
EEG: THETA FREQUENCY BAND
FREQUENCY
- 4-8Hz
AMPLITUDE
- 5-10uV
LOCATION
- various
ACTIVITY
- drowsiness; light sleep
EEG: ALPHA FREQUENCY BAND
FREQUENCY
- 8-13Hz
AMPLITUDE
- 20-80uV
LOCATION
- posterior region of head
ACTIVITY
- relaxed
EEG: BETA FREQUENCY BAND
FREQUENCY
- 13-30Hz
AMPLITUDE
- 1-5uV
LOCATION
- left/right side; symmetrical distribution; more evident frontally
ACTIVITY
- active thinking; alert
EEG: GAMMA FREQUENCY BAND
FREQUENCY
- >30Hz
AMPLITUDE
- .5-2uV
LOCATION
- somatosensory cortex
ACTIVITY
- hyperactivity
PERTURBING NEURAL FUNCTION
- pharmacology
- genetics
- invasive stimulation (ie. deep brain stimulation; optogenetics)
- noninvasive stimulation (ie. trasncranial magnetic/direct & alternating current stimulation (TMS/tDCS/tACS)
- lesion studies
NEUROMODULATION METHODS
TRANSCRANIAL DIRECT CURRENT STIMULATION (tDCS)
- anodal (up)
- cathodal (down)
TRANSCRANIAL MAGNETIC STIMULATION (TMS)
- single pulse TMS (spTMS)
- repetitive TMS (rTMS) ->
- high/low frequency (rTMS)
- theta burst stimulation (TBS) ->
- intermittent TBS (up)
- continuous TBS (down)
TRANSCRANIAL MAGNETIC STIMULATION (TMS)
- wire coil connected to electrical capacitators; generate magnetic field in coil
- coil placed on surface of skull; magnetic field passes safely to brain
- induces electrical current in neurons to fire
WAGNER ET AL. (2009)
ELECTROMAGNETIC STIMULATION/INDUCTION
- time varying current in coil; coil = electromagnet driven by current
- generates time varying magnetic field; magnetic field function of driving current/coil
- induces electric field in material; electric field function of magnetic field/properties of material
- drives current in material; induced current function of electric field/properties of material ->
- TMS drives currents in brain stimulating neurons
THETA BURST STIMULATION (TBS)
- rTMS variant; increases (iTBS)/decreases (cTBS) cortical excitability for up to 1h post-stimulation
- after-effects attributable to early phase LTP/LTD like changes in cortical plasticity:
1. triggers post-synaptic glutamate release
2. NMDA receptors -> increases Ca^2+ lvls
3. rate/absolute lvls of Ca^2+ change determines inhibitory VS excitatory effects
NEUROMODULATION: PROS
- causality = immediate effects
- informative; cognitive processes’ timing/location
- no connection to body/need for scanner
NEUROMODULATION: CONS
- transient effect
- not good for long tasks
- not all areas of cortex can be stimulated
- rTMS seems more effective than tDCS
METHODS SUMMARY
- each method has pros/cons
- consider methods carefully
- combine techniques to optimise stengths
BRAIN PERSPECTIVES
BRAIN-AS-OUTCOME
- PA -> moderators -> brain
BRAIN-AS-MEDIATOR
- PA -> moderators + brain -> cognitive functioning (ie. inhibitory control)
BRAIN-AS-PREDICTOR
- brain -> cognitive/psychological characteristics (ie. executive functioning) + moderators -> PA behaviours (ie. adherence)
LOWE ET AL. (2018)
- using cTBS to test causal link between PFC activity/overeating
- within subject design in healthy young women
- completed inhibitory control measures
- measured changes in food-cravings
- completed bogus taste test for 5 dif snack foods
