Samenvatting
Summary Introduction to Human Neuroimaging, ISBN: 9781316850565 Cognitive Neuropsychology (540033-B-6)
- Instelling
- Tilburg University (UVT)
Summary of the course 'Cognitive Neuropsychology'.
[Meer zien]Voorbeeld 4 van de 58 pagina's
Voorbeeld 4 van de 58 pagina's
In winkelwagengesponsord bericht van onze partner
Gekoppeld boek
Titel boek:
Auteur(s):
- Uitgave:
- ISBN:
- Druk:
Voorbeeld van de inhoud
Summary slides - Cognitive Neuropsychology:Lecture 1: Introduction
Cognitive Neuropsychology – definition:
- The study of the relation between structure and function of the brain and specific cognitive functions
(e.g. language, memory, attention, …)
o by investigating these cognitive processes in normal healthy people
o by investigating the breakdown of these processes in brain-damaged individuals (as a result
of acquired brain damage or as a result of a developmental disorder)
Brain enthusiasm:
- Brain scans as evidence in court of law
- Brain scans might be overinterpreted by laypersons
- Good progress for several neurological syndromes, but less progress for psychiatric and mental
syndromes.
o Differences found for psychiatric and mental syndromes on a group level but difficult on an
induvial level.
Basis of neural signals:
- Neurons, with cell bodies in grey matter of cerebral
cortex and subcortical structures; white matter contains
axons.
- Without input (at rest), cell membrane of a neuron has
an electrical potential difference between in- and
outside of -70 mV
- Post-synaptic potential is determined by integrating
input of many synapses at the dendrites. It can hyper-
and depolarize.
- Neural communication:
o Input neurons (through neurotransmitters): action potentials over time
→ Membrane potential of post-synaptic neuron depolarizes or hyperpolarizes
o Over time, membrane potential of post-synaptic neuron changes in function of input it
receives = signal
Signal description:
- Simplest signal = sinusoidal oscillation
- Frequency: rate of change of signal, e.g. in the time dimension
o 1 Hz = completing a full cycle (going up & down) in one
second
o Biological signals never contain just one frequency
- Complex signals can be decomposed into frequency components
o Each has a particular frequency (e.g., 1 Hz, 2 Hz, 3 Hz, …)
o Amplitude: how much it goes up and down
o Phase: when it goes up and down
- Frequency spectrum: measured range of frequencies
o Highest frequency
▪ Limited by sampling frequency
▪ ½ * sampling frequency (Nyquist sampling theorem)
o Lowest frequency
1
, ▪ Limited by how long the signal is measured
▪ 1 / number of seconds measured
- Filtering: attenuating or excluding certain part of measured frequency spectrum (low-pass, high-pass
or band-pass)
- Spectrogram: strength of each signal component at each moment in time
Molecular and hemodynamic signals:
- Electrophysiological changes are connected to other kind of changes...
o At a smaller scale: movement of chemical substances and molecules
▪ E.g. depolarization: influx of Na+, repolarization: outward current of K+
▪ E.g. calcium concentration high in electrically active neurons → two-photon calcium
imaging
o At a larger scale: hemodynamics
▪ Blood supply is adjusted to current energy needs
- Energy consumption
o Electrophysiological events require energy
o Amplitude of potential changes not necessarily best predictor of energy consumption
▪ Action potential = passive chain of events that does not consume much energy
o Restoring resting potential requires energy → energy consumption of neuron could correlate
with number of action potentials
o Pre- and post-synaptic factors (e.g., neurotransmitter release) also require energy
o Exact energy distribution to different processes can vary (species, neuron type)
Maps in the brain:
- Clustering
o Noninvasive methods cannot achieve single neuron resolution
▪ Methods with highest spatial resolution still average signal from many neurons
- Neurons of similar functional properties are clustered together
o The more clustering, the more the averaged signal from many neurons corresponds to the
signal of the individual neurons → sensitivity of a noninvasive imaging technique depends
upon amount of clustering present
o Clustering on different spatial scales
▪ Topographic areas: for example the somatosensory homunculus but also for auditory
or occipital information
Overview of methods: three dimensions
- Temporal resolution: the smallest unit of time that can be differentiated by a method
- Spatial resolution: the smallest unit of space which can be resolved
2
, - Invasiveness: majority of methods are either fully invasive (skull needs to be penetrated) or not
invasive at all
o Invasive methods: used mostly in animal studies
o Non-invasive methods: also used for humans
Focus on less invasive techniques!
Measuring brain structure:
- Histology
o Cutting brain in pieces (e.g. slice of mouse brain)
o Process chemically for visualization of specific structure
▪ Makes us able to differentiate between the 6 brain layers, and between different
structures in the brain
- Structural magnetic resonance imaging (MRI)
o Investigation of anatomy in individuals
o Anatomical localization of functional findings
o Relate anatomical structure to differences between participants in e.g. behavior, disease
classification
Measuring hemodynamics:
- Changes in blood and tissue oxygenation, blood flow, and blood volume
- Temporal resolution of hemodynamic imaging is poorer compared to electrical imaging due to
slowness of hemodynamic events
o hemodynamic events take 16 sec to develop
- Spatial resolution varies strongly (but range smaller than for electrical signals):
o (invasive) optical imaging: columnar structure visible
o (non-invasive) fNIRS: several cm
Measuring electrophysiological activity:
- Spatial resolution, affected by
o Distance electrode and source of the signal
o Intermediate tissue (e.g. skull)
o Noninvasiveness: highest frequencies cannot be picked up
▪ Different frequency bands contain very different information!
- Quiroga et al. (2005): single unit recordings in epilepsy patients
o Theory that in every person there is only on neuron that responses to a picture of their
grandmother. For every different face a different neuron responds.
o Very exciting, but rare, ethical constraints, and difficult experimental control
→ less invasive techniques in humans
- Pitcher et al. (2011): EEG study
o Signal of EEG-electrodes on back of the head, averaged across many trials of viewing faces
(red) or chairs (blue)
3
, o Amplitude of N170 & P1 is stronger for faces versus chairs
o Due to low spatial resolution of EEG these components do not differentiate between
Aniston, Pitt, ..., and anatomical localization is poor
Peripheral measures:
- Always good to measure peripheral data, in addition to the variables you want to measure
- Skin conductance
o index of (sympathetic) arousal intensity in affective or cognitive processing
o highly variable, difference between subjects is huge
- Heart activity
o heart rate
o heart rate variability: measures influence of PNS on heart
o blood pressure: measure of stress
- Muscle activity
o Facial EMG (electromyography) as a tool for inferring affective states
- Eye measures
o Eye movements: good measure of visual attention
▪ Saccades (fast movements of the eyes): Very fast (20-40 ms), no new information is
acquired during saccades
▪ Fixations : Information acquisition occurs (mainly) during fixation
▪ Proudfoot et al. (2017) → Eye tracking in ALS patients
Trail making test A & B: connect the dots → 1-2--A-2-B-3-C etc.
o Pupil dilation
▪ indicative of intense emotional arousal toward both pleasant and unpleasant stimuli
and experiences
▪ Bradley et al. (2007): pupil dilation reflects SNS activity
Pupil diameter larger for pleasant & unpleasant conditions than for neutral
Lecture 2: EEG
Why use electroencephalogram (EEG)?
- Reaction time is the final outcome of sensory, decision and motor processes
- EEG can track the time course of these stages with millisecond precision
- EEG can inform us about cognitive processes when there is no behavioral response
Electrophysiological activity of the brain:
- Hans Berger reported the first non-invasive human EEG in 1929
What is measured by EEG?
- Post synaptic potentials at apical dendritic trees of pyramidal cells
o Action potentials can not be added up so not useful for EEG
o Post synaptic potentials can be added up so useful for
EEG.
- For brain electrical activity to be detectable through skull,
must be strong signal summed over many neurons
o All behaving similarly at same time
o All oriented in same way
▪ This way the potentials can be added up
without canceling each other out
4
Voordelen van het kopen van samenvattingen bij Stuvia op een rij:
Verzekerd van kwaliteit door reviews
Stuvia-klanten hebben meer dan 700.000 samenvattingen beoordeeld. Zo weet je zeker dat je de beste documenten koopt!
Snel en makkelijk kopen
Je betaalt supersnel en eenmalig met iDeal, creditcard of Stuvia-tegoed voor de samenvatting. Zonder lidmaatschap.
Focus op de essentie
Samenvattingen worden geschreven voor en door anderen. Daarom zijn de samenvattingen altijd betrouwbaar en actueel. Zo kom je snel tot de kern!
Veelgestelde vragen
Wat krijg ik als ik dit document koop?
Je krijgt een PDF, die direct beschikbaar is na je aankoop. Het gekochte document is altijd, overal en oneindig toegankelijk via je profiel.
Tevredenheidsgarantie: hoe werkt dat?
Onze tevredenheidsgarantie zorgt ervoor dat je altijd een studiedocument vindt dat goed bij je past. Je vult een formulier in en onze klantenservice regelt de rest.
Van wie koop ik deze samenvatting?
Stuvia is een marktplaats, je koop dit document dus niet van ons, maar van verkoper NinaPsychology. Stuvia faciliteert de betaling aan de verkoper.
Zit ik meteen vast aan een abonnement?
Nee, je koopt alleen deze samenvatting voor €5,49. Je zit daarna nergens aan vast.
Is Stuvia te vertrouwen?
4,6 sterren op Google & Trustpilot (+1000 reviews)
Afgelopen 30 dagen zijn er 83637 samenvattingen verkocht
Opgericht in 2010, al 14 jaar dé plek om samenvattingen te kopen
