Week 1-Research Methods in Cognitive Neuroscience Flashcards
The Electrophysiological brain: What is the function of the frontal lobe?
Executive functions such as Planning and Problem solving
The Electrophysiological brain: What is the function of the temporal lobe?
Auditory functions such as Language and language perception, Memory and Emotions
The Electrophysiological brain: What is the function of the Occipital lobe?
Visual perception such as Object representation (extracting features)
The Electrophysiological brain: What is the function of the parietal lobe?
Attention, Sensation and Body position
The Electrophysiological brain: What is the function of the basal ganglia?
Movement coordination e.g., riding a bike
The Electrophysiological brain: What is the function of the brain stem?
Physiological functions (e.g., digestion, breathing)
The Electrophysiological brain: What is the function of the cerebellum?
Balance, Coordination, Voluntary movements.
The Electrophysiological brain: What is Korbinian Brodmann’s (1868-1918) key discovery?
-The discovery of 52 Brodmann areas
-Creating greater detail of the brain anatomy based on function
The Electrophysiological brain: What is the Spatio-Temporal Trade off? (Churchland & Sejnowski, 1988)
Some techniques are effective with spatial resolution allowing the neurons to be investigated BUT has a poor temporal resolution (1s) and vice versa with other techniques.
The Electrophysiological brain: How do neurons communicate?
Neurons between each other communicate via electro-chemical signals (at the basic communication level)
The Electrophysiological brain: What is the membrane potential?
-Stable electrochemical gradient (environment) at rest (no communication or stimulus).
-Difference of positive (Na+) and negative (K-) charges between inside and outside environments
-Membrane potential: Vm = Vin – Vout = -70 µV
Vin=voltage in
Vout=voltage out
µV=microvolts
The Electrophysiological brain: How is an action potential generated?
- When the neuron receives a strong signal, the flow of Na+ increases into the neuron, and the flow of K- outside the neuron (becomes a more positive environment internally).
- This affects the general gradient and membrane permeability, enabling depolarisation (i.e., becomes more positive).
- It reaches a threshold (-55mV), causing a rapid upward spike in voltage.
- The positive spike propagates along the axon and is called the “Action potential” (the electrical aspect of brain communication)
The Electrophysiological brain: How do neurons behave as electric dipoles?
-Electric dipoles=battery like
-This creates an electric field along the dipole, which allows conducting the current.
-This in turn creates a magnetic field around the dipole (internal and external cell).
-Every neuron acts as a positive and negative dipole (inside and outside of the neuron)
-This is the electrical properties we use with EEG
The Electrophysiological brain: Who created Electroencephalography? (EEG)
-In 1924 a German psychiatrist Hans Berger developed the electroencephalograph (EEG machine) to record the human brain waves.
-Brainwaves are the total dipole result in brain activity
The Electrophysiological brain: What are modern EEG systems like now?
-Modern systems using soft caps
-EEG measures the summation of electr(ochem)ical activity on the scalp over time by means of recording-electrodes attached to the surface of the scalp.
-EEG provides a useful overview of the electrical activity of the brain.
-Diagnostically EEG is often used in the clinical diagnosis of brain damage and neurological disorders, e.g. epilepsy
The Electrophysiological brain: What activity are Gamma waves associated with?
Hyper brain activity (learning)
The Electrophysiological brain: What activity are Beta waves associated with?
High brain activity (conversation)
The Electrophysiological brain: What activity are Alpha waves associated with?
Initial brain relaxation
The Electrophysiological brain: What activity are Theta waves associated with?
Drifting down into sleeping
The Electrophysiological brain: What activity are Delta waves associated with?
Deep non-dreaming sleep
The Electrophysiological brain: What are some characteristics of Alpha waves?
-Regular - Synchronous
-8 -12 Hz
-High amplitude
The Electrophysiological brain: What does the synchronisation of alpha activity indicate?
It indicates relaxed wakefulness
The Electrophysiological brain: What does the EEG and its electrode measure?
-EEG measures the post-synaptic activity (postsynaptic potentials, PSPS) around the dendrites of pyramidal neurons in the cerebral cortex
-An EEG electrode sums the electrical potentials occurring from many thousands of brain cells.
-One electrode will not capture one dipole but rather is sensitive to the neurons around that one electrode
The Electrophysiological brain: What are the 3 characteristics of Pre-Synaptic Potentials? (PESP)
- Action potential
- Excitatory only
- Fast (advantage)
The Electrophysiological brain: What are the 4 characteristics of Post-Synaptic Potentials? (POSP)
- Excitatory (Depolarising) or Inhibitory (Hyperpolarising), depending on the neurotransmitter received from Neuron A.
- Slow and long-lasting (advantage).
- Enabled if sufficient inputs towards Neuron B.
- EEG captures ONLY POSP, not PESP.
The Electrophysiological brain: What are Post-Synaptic Potentials? (POSP)
Axons from neighbouring neurons synapse with the pyramidal neurons, triggering local depolarisation: POSTSYNAPTIC POTENTIALS (PSPs)
The Electrophysiological brain: How are the layers in the human brain cortex distributed including pyramidal cells and dendrites?
-Pyramidal cells are distributed and spatially aligned in the most superficial layers of the human brain cortex.
-Pyramidal cells in layers 3, 4, 5 and 6 are the generators of EEG signals
-Layers 1 and 2 contain the dendrites of the pyramid cells (the dendritic region) - the EEG sources are the slow post-synaptic signals generated in these layers
-Their activity is synchronous; this produces a large signal that can be detected from the scalp
The Electrophysiological brain: What are the 2 Main Keys for a good EEG signal?
- Timing: enough neurons acting in a moment to create sufficient voltage
- Orientation: depending on the orientation the signal can cancel out or potentialise (depending on both the Tangential and Radial Dipoles)
The Electrophysiological brain: How are electrodes on the EEG cap positioned?
-They’re positioned in very specific locations
-This is achieved using the internationally standardised 10-20 system: 10-20 relates to the space between the electrodes when placed on the cap
The Electrophysiological brain: True or False: EEG signals are always a relative measure (Teplan, 2002)
TRUE (a difference in potential between one electrode and another electrode is always used as a reference)
-We measure the ratio of the voltage of the electrode and neutral electrodes (meaning they’re turned off)
The Electrophysiological brain: What are EEG recordings translated into?
Translated into line tracings i.e., brain waves
The Electrophysiological brain: What are Event-Related Potentials? (ERPs) (Luck, 2014; Woodman, 2010)
-It measures the response to a specific event (e.g. sensory cognitive or motor stimulus/ task).
- A fundamental element for a clean and reliable ERP response is averaging signals from many trials and many participants.
-The reason to average is that EEG is sensitive to noise and movement
-The many trials can be boring for participants
The Electrophysiological brain: What are the advantages of ERPs?
- ERPs provide excellent temporal resolution (1ms)
- Great tool to study fast cortical processes (e.g. vision, attention)
The Electrophysiological brain: What are the critical elements of ERP components?
-Components=things that are always found in response to a task or stimulus
- Amplitude (and difference amplitude between conditions)
- Latency (and difference latency between conditions)
- Scalp distribution (Means you can localise the regions based on their intensity and/or areas of focus)
The Electrophysiological brain: What is Electromyography? (EMG)
Detects the electrical potential of the muscle cell (membrane potential is ~-90mV)
-EMG will be placed near a muscle NOT on the brain
The Electrophysiological brain: What is Electrooculography? (EOG)?
Electrodes are placed near the eyes and record the membrane potential of the retina.
The Electrophysiological brain: What is the skin conductance response? (SCR)
Change in the electrical properties of the skin, associated mainly with sweat gland activity.
-Elicited by stimuli that cause (emotional) arousal.
The Electrophysiological brain: What is Electrocardiography? (ECG)
Measure of heartbeat. Average heart rate of healthy adult is 70 beats per minute.
The Electrophysiological brain: What is Magnetoencephalography? (MEG) (Singh, 2014)
-Detects the electromagnetic field generated by the neurons’ electrical activity
-Superconducting quantum interference devices (SQUID sensors) allow recording of the small neuromagnetic signals generated in the brain
-We can see almost all of the cortex, fissural activity emphasized with the MEG
-Positive and negative dipole creates an electromagnetic field which cannot be detected by an EEG BUT can be detected by MEG
-MEG is very expensive and requires a specific environment to function (hence why less popular than EEGs)
The Electrophysiological brain: What are 5 advantages of Magnetoencephalography? (MEG)
- Signal unaffected by skull, meninges…
- Detects only tangential dipoles - fissural activity emphasized
- High temporal resolution (ms)
- Good spatial resolution (combined with MRI)
- Very expensive and limited availability
The electrophysiological brain: How do the EEG and MEG differ in terms of signal?
EEG signals are affected by skull, meninges etc., WHEREAS MEG signals are unaffected by skull, meninges etc.,
The electrophysiological brain: How do the EEG and MEG differ in terms of dipole detection?
EEG detects both tangential dipoles (at sulci) and radial dipoles (at gyri) WHEREAS MEG detects only tangential dipoles (both positive and negative polarities).
The electrophysiological brain: How do the EEG and MEG differ in terms of temporal resolution?
They both have a high temporal resolution (ms)
The electrophysiological brain: How do the EEG and MEG differ in terms of spatial resolution?
EEG has poor spatial resolution WHEREAS MEG has good spatial resolution (combined with MRI).
The electrophysiological brain: How do the EEG and MEG differ in terms of availability and price?
EEGs are “cheap” and widely available WHEREAS MEGs are very expensive with limited availability.
The imaged brain: What is Structural imaging?
-Explores physical brain structure and changes in it (e.g. Contrast X-ray, Computed Tomography, Magnetic Resonance)
-Images different types of tissues (skull, grey matter, white matter, cerebrospinal fluid) with different physical properties
-These physical properties are exploited to create static maps of the physical structure of the brain
The imaged brain: What is Functional imaging?
-Explores brain cognitive (dis-)functioning (e.g. functional Magnetic Resonance, Positron Emission Tomography)
-Neural activity produces physiological changes on site, which are used to create dynamic maps of the moment-to-moment activity of the brain.
Structural neuroimaging: What tissues’ properties are exploited using X-ray computed Tomography? (CT)
-The amount of X-ray that the tissue can absorb.
-Bones (skull) absorb most x-rays (= appears white)
-The cerebrospinal fluid absorbs the least (= black)
-Gray/white matter is intermediate absorption ( = gray)
Structural neuroimaging: How does X-ray computed Tomography work? (CT)
-Multiple x-ray tubes shoot X-rays from many angles which are reached by detectors on the opposite site. These rotate around the head on the same horizontal plane (like a vertical wheel). A computer combines the readings to create an image of a horizontal slice of the brain.
-Then both tubes and detectors move rostrally (towards the head-end of the body) along the vertical axis of the body. The cycle repeats until the whole brain has been imaged.
Structural neuroimaging: What tissues’ properties are exploited using Magnetic Resonance Imaging (MRI)?
The amount of water (H2O <-> H+ OH-) in each tissue.
Structural neuroimaging: How does Magnetic Resonance Imaging (MRI) work?
-Different tissues contain different amounts of water. The single protons (H+) in the water have magnetic fields, which are randomly oriented.
-When a strong magnetic field is applied from the scan (constantly), the magnetic fields of protons align with it.
-At this point, a brief radio-wave pulse is applied, and the orientation of the protons is knocked by 90 degrees.
-As the protons spin (precess) in the new state, they produce the detectable signal.
-The protons are eventually pulled back to the original state of alignment with the magnetic field (relaxation)
Structural neuroimaging: How do the protons align in Magnetic Resonance Imaging (MRI)?
- H+ protons in tissues’ water with randomly oriented magnetic fields
- External magnetic field is applied
- H+ magnetic fields align
- Radio Frequency coil generates brief radio wave pulse. H+ orientation is knocked by 90º (Precession)
- Protons are pulled back to alignment = Relaxation (time of decay of signal)
T1 relaxation: time taken for protons to move back to alignment
T2 relaxation: quantifies the rate of decay of the signal
Structural neuroimaging: How can you detect and differ between T1 and T2 relaxation using MRI?
T1:
-Fluids (high in water): Black
-Tissues rich in fat: White
-Good for generic anatomical structure
T2:
-Fluids (high in water): White
-Tissues rich in fat: black
-Good for identification of lesions (normally rich in water)
Structural neuroimaging: How do CT and MRI differ in terms of invasiveness?
CT: Invasive: Radiation Exposure (~ same as background radiation an average person receives in 3 to 5 years)
MRI: NOT Invasive: no emission of ionizing radiation. Completely safe!
Structural neuroimaging: How do CT and MRI differ in terms of price?
CT is expensive and MRI is more expensive?
Structural neuroimaging: How do CT and MRI differ in terms of scanning time?
CT: Short time to complete a scan (~5 minute). Low sensitivity to patient movements. Seldom creates claustrophobia.
MRI: Variable scanning time, ranging from ~15 minutes up to 2 hours. High sensitivity to movements. Very high risk of claustrophobic symptoms (anxiety).
Structural neuroimaging: How do CT and MRI differ in terms of spatial resolution?
CT: Poor spatial resolution (brain matter appears all gray)
MRI: Better spatial resolution. It distinguishes between gray and white matter and discerns between the folds of individual gyri.
Structural neuroimaging: How do CT and MRI differ in terms of imaging?
CT: Able to image bone, soft tissue and blood vessels all at the same time.
MRI: More detailed and can detect very small alterations in soft tissue
Structural neuroimaging: How do CT and MRI differ in terms of what they’re best for?
CT: Used when speed is important (i.e. trauma and stroke).
MRI: Best for cancer, causes of dementia or neurological diseases.
Functional neuroimaging: How does functional imaging reflects energy metabolism?
-Neural Activity requires a lot of energy, which needs to be metabolised.
-Focuses on the change in metabolism
-Energy metabolism: Rate at which neurons produce and consume ATP (Adenosine triphosphate)
-ATP production in neurons requires GLUCOSE (PET) and OXYGEN (fMRI) uptake from the blood.
Functional neuroimaging: What functional property is exploited in Positron Emission Tomography (PET)?
High uptake of biologic molecules (glucose) by metabolically active neuronal cells.
Functional neuroimaging: How does Positron Emission Tomography (PET) work?
-A carrier molecule (e.g. deoxyglucose) is combined with a radioisotope (e.g. 18-Fluoro[F]), which is an unstable radionuclide
-This tracer is injected into the blood stream and can be absorbed by tissues (≠ molecules: ≠ tissues).
-You will see Radionuclides in the neuron using PET which is why its combined to a glucose carrier molecules
-Once the tracer is inside the cell, it undergoes radioactive decays (releases positrons).
-Each positron interacts with an electron in the surrounding cell milieu. This interaction (= collision) causes annihilation of both particles, releasing two photons that speed off in opposite directions.
-Produces gamma rays detectable by the PET machine.
Functional neuroimaging: What are unstable radionuclides in Positron Emission Tomography (PET)?
-It is a radioactive atom, also called RADIO- ISOTOPE.
-Unstable ratio neutron/proton in the nucleus (too many neutrons or too many protons).
-RADIOACTIVE DECAY: spontaneously going back to stable state by throwing particles in the space = releases positrons
Functional neuroimaging: What functional property is exploited in functional MRI (fMRI)?
Oxygen consumption during high metabolic activity
Functional neuroimaging: How does functional MRI (fMRI) work?
-When neurons are very active, there is an increase in oxygenated blood supply.
-The active areas take up more oxygenated haemoglobin that they need for their energy requirements.
-There is thus a greater proportion of oxygenated haemoglobin to deoxygenated haemoglobin in active areas.
-fMRI detects differences in magnetic properties between oxygenated and deoxygenated blood, which alters the relaxation time of H+ protons.
-Deoxyhemoglobin normally creates magnetic inhomogeneity (this alters the relaxation time of nearby H+ protons).
-In active areas, there is more oxygenated haemoglobin which restores a more homogenous magnetic field. This results in a longer T2 relaxation time and a brighter signal in active areas.
Functional neuroimaging: How do PET and fMRI differ in terms of invasiveness?
PET: Invasive-involves radioactive tracers (although radiation passes quickly out of the body)
fMRI: NOT Invasive - Completely safe!
Functional neuroimaging: How do PET and fMRI differ in terms of price?
They’re both expensive
Functional neuroimaging: How do PET and fMRI differ in terms of temporal resolution?
PET: Very low temporal resolution = 30 sec.
fMRI: Better temporal resolution = 1-2 sec (still very low compared to EEG 1ms/EMG)
Functional neuroimaging: How do PET and fMRI differ in terms of spatial resolution?
PET: Good spatial resolution = 10mm
fMRI: Better spatial resolution = 1mm
Functional neuroimaging: How do PET and fMRI differ in terms of design?
PET: Only block design (cognitive subtraction: experimental vs baseline conditions, subtraction of activated areas)
fMRI: Both block design and event-related design
Functional neuroimaging: How do PET and fMRI differ in terms of sensitivity and imaging?
PET: Sensitive to whole brain
fMRI: Some brain regions are hard to image due to different magnetic properties (e.g. near sinuses, oral cavity)
Functional neuroimaging: How do PET and fMRI differ in terms of sensitivity to movements?
PET: Not affected by movements (good for producing over speech)
fMRI: Very sensitive to movements
Functional neuroimaging: How do EEG and fMRI differ in terms of invasiveness?
They’re both not invasive
Functional neuroimaging: How do EEG and fMRI differ in terms of price?
EEG: “Cheap” – widely used
fMRI: Expensive
Functional neuroimaging: How do EEG and fMRI differ in terms of resolution?
EEG: High temporal resolution (ms) + Low Spatial Resolution (only surface of brain)
fMRI: Low temporal resolution = 1-2s + High spatial resolution = 1mm
Functional neuroimaging: How do EEG and fMRI differ in terms of signal?
EEG: Signal affected by skull, meninges etc.,
fMRI: Some brain regions are hard to image due to different magnetic properties (e.g. near sinuses, oral cavity)
Functional neuroimaging: How do EEG and fMRI differ in terms of design?
EEG: Event-related design, continuous recording, frequency measure
fMRI: Both block design and event-related design
Functional neuroimaging: How do EEG and fMRI differ in terms of sensitivity to movements?
They are both very sensitive to movements
What is the issue of causality?
-Neuroimaging (and Neurophysiology) tells you what areas are involved in a process (correlation), NOT what areas are necessary for that process (causation).
-Correlation is NOT Causation
-Lesion studies or Transcranic Magnetic Resonance (TMS) can be more appropriate to test for causation.
Define Causation
2 variables x and y are causally related if a manipulation of the independent variable x (e.g., brain activity) causes a change in the dependent variable y (e.g., behaviour).
Virtual Lesions: How does Transcranical Magnetic Stimulation (TMS) work? (Sliwinska et al., 2014)
-TMS disrupts activity in a brain area by creating a magnetic field under a coil, placed over the targeted area.
-A large electrical field is passed through the coil and generates a magnetic pulse that passes through the skull.
-Magnetic fields induce electrical activity in the target area and affect its normal function.
-TMS simulates a short-lasting “visual lesion” in a target region to investigate its role in a particular mechanism
Virtual Lesions: What was Sliwinska, Vitello, & Devlin’s (2014) method in using TMS?
-Tests whether TMS stimulation affects task performance
-TMS applied on supramarginal gyrus (SMG)
3 tasks:
1. Phonological (Do these 2 words sound the same?)
2. Semantic (Do these 2 words mean the same thing?)
3. Control (are this consonant letter strings the same e.g., wsrft-wsfrt)
-Applied TMS during stimulus presentation i.e., brain actively engaged in the processing
-Measures RT (reaction time) depending on TMS stimulation and task
Virtual Lesions: What was Sliwinska, Vitello, & Devlin’s (2014) findings using TMS?
2 things inferred from this study:
1. The effect of TMS stimulation is reflected in behavioural measures (e.g. RTs).
2. Indicative of the causality of the stimulated brain region in task performance.
-RT increased when the TMS was applied to the supramarginal gyrus (SMG) during the phonological task only.
-Indicative of the causality of the stimulated brain region in phonological processing: if “SMG virtually lesioned, the mechanism is broken”.
Virtual Lesions: What are the advantages of TMS over Lesions?
-In the real damaged brain, reorganization and compensatory strategies may have developed (Lesion is highly controlled in TMS)
-No problem with too difficult tasks for patients
-It recruits the general population (often the number of patients with a similar lesion is low) (less heterogeneity)
Virtual Lesions: What are the advantages of TMS over Neuromaging?
-Does not investigate mere correlations, but causal relations.
-Allows investigation on timing of cognitive functions.
-Allows investigation on the necessity of a brain area.
-Allows investigation of dynamic connectivity between areas.
Invasive methods on humans: What are Invasive EEG in humans (Intracranial EEG) used for?
-Used for localization of the region of the brain from which the epilepsy is arising (recording during seizures)
-Used on patients with drug-resistant intractable epilepsy during pre-surgical evaluation
-Some patients also agree to participate in research
-Get monitored over at least 2 weeks in hospital using EEGs with electrodes deep in the brain
Invasive methods on humans: How does Invasive EEG in humans (Intracranial EEG) work?
-iEEG recordings in the hippocampus: Implanted epileptic patients
-Unique action potentials for every neuron
-Similar to classic EEG except its just focal meaning you can’t look at the entire brain
