Cognitive Neuroscience, Lecture 1

Question 1

What are some methods for looking at the brain?

Answer 1

• Electroencephalography (EEG)
• Magnetoencephalography (MEG)
• Positron Emission Tomography (PET)
• Magnetic Resonance Imaging (MRI)
• Functional MRI (fMRI)
• Diffusion Tensor Imaging (DTI)
• Functional Near-Infrared Spectroscopy (fNIRS)
• Intracranial electroencephalography (iEEG)

Question 2

What is single-cell recording?

Answer 2

Involves the implantation of a very small electrode into an axon (intracellular) or outside an axon membrane (extracellular). This records the neural activity from a population of neurons.

Question 3

How are recordings of brain cell activities made?

Answer 3

Measuring the electrical potential of nearby neurons that are in close proximity to the electrode.

Question 4

What is electroencephalography?

Answer 4

EEG is the measurement of the electrical activity of the brain by recording from electrodes placed on the scalp.

Question 5

What do EEG signals represent?

Answer 5

The change in the potential difference between two electrodes placed on the scalp in time. The EEG obtained on several trials can be averaged together time-locked to the stimulus to form an event-related potential (ERP).

Question 6

What are ERPs?

Answer 6

Event-related potentials are voltage fluctuations that are associated in time with a particular event (visual, auditory, olfactory stimuli).

Question 7

How can ERPs be extracted?

Answer 7

From the ongoing EEG by means of filtering and averaging.

Question 8

Which ERP peaks are associated with which aspects of face processing?

Answer 8

• N170 is relatively specialised for faces, recording from right PSTS
• P300 - famous and familiar faces
• N250 - face recognition, identity processing
• P400 - P600 - person recognition, faces and names

Question 9

What is a MEG?

Answer 9

Magnetoencephalography is an imaging technique used to measure the magnetic fields produced by electrical activity in the brain via SQUIDS. It has excellent temporal and spatial resolution

Question 10

When are MEG measurements used?

Answer 10

Commonly in research and clinical settings

Question 11

What are SQUID sensors?

Answer 11

306 independent measurement channgels, which are organised in channel-triplets on 102 silicon chips

Question 12

What is MRI?

Answer 12

Magnetic Resonance Imaging uses differential magnetic properties of types of tissues and blood to produce images of the brain

Question 13

What is structual imaging?

Answer 13

Different types of tissue (skull, gray matter, white matter, CSF fluid) have different physical properties - used to create STATIC maps (CT and structural MRI)

Question 14

What is functional imaging?

Answer 14

Temporary changes in physiology associated with cognitive processing (PET & fMRI)

Question 15

What is a PET scan?

Answer 15

Positron Emission Tomography measures local blood flow (rCBF). A radioactive tracer is injected into the blood stream which takes 30 seconds to peak. When the material undergoes radioactive decay, a positron is emitted, which can be picked up by the detector. Areas of high radioactivity are associated with brain activity, based on blood volume.

Question 16

What is an fMRI?

Answer 16

It is a functional MRI that measures the concentration of deoxyhemoglobin in the blood. We can study the correlation between brain activity and stimulus timings and can be used to produce activation maps showing which parts of the brain are involved in particular mental processes.

Question 17

What is the BOLD response?

Answer 17

Blood Oxygen Level Dependent contract, the concentration of deoxyhaemoglobin in the blood.

Question 18

What is the hemodynamic response function?

Answer 18

The change in BOLD response over time, and peaks in 6-8 seconds. LIMITS TEMPORAL RESOLUTION OF FMRI.

Question 19

Actions embedded in cotexts and intentions, compared with two other conditions, yielded what result?

Answer 19

A significant BOLD signal increase in the posterior part of the inferior frontal gyrus IFG and the ventral premotor cortex where hand actions are represented. Premotor mirror neuron areas are also involved in understanding the intention of others.

Question 20

How do we infer functional specialization?

Answer 20

Need to compare relative differences in brain activity between two or more conditions. -> involves selecting a baseline or comparison condition

Question 21

When is a region “active”?

Answer 21

If it shows a greater response in one condition relative to another.

Question 22

What brain region is associated with recognising written words?

Answer 22

Occipital-temporal junction [word-cross]. To test this, ppts must have a passive viewing of written words. PASSIVE VIEWING OF FIXATION CROSS

Question 23

What are the brain regions involved in saying the words?

Answer 23

Motor areas [reading aloud - passive]. To test this, ppts must read aloud a written word [phonology/articulation].

Question 24

What are the brain regions involved in retrieving the meaning of words?

Answer 24

Left interior frontal gyrus [verb generation - reading]. To test this, ppts must generate an action.

Question 25

What is Diffusion Tensor Imaging?

Answer 25

An imaging method that uses a modified MRI scanner to reveal bundles of axons in the living brain. It measures white matter organisation based on limited diffusion of water molecules in axons - we can visualise connections in the brain

Question 26

What is Functional Near-Infrared Spectroscopy?

Answer 26

Measures the same BOLD response as fMRI - ‘light’ in the infrared range passes through the skull and scalp but is scattered differently by oxy-v. deoxyhemoglobin. It is portable and more tolerant of head movement - can’t image deep structures

Question 27

What is intracranial electroencephalography?

Answer 27

The only method that gives high resolution in both time and place - when we record directly from inside the human brain, when people are undergoing neurosurgery. They are placed to locate the seizure and map function. Recording straight from the cortical surface - approx 10s of thousands of neurons

Question 28

What did Mukamel et al., 2010 study about intracranial recordings in humans?

Answer 28

Recorded extracellular activity from 1177 cells in human medial frontal and temporal cortices while patients executed or observed hand grasping actions and facial emotional expressions.

–> Neurons in supplementary motor area SMA, and hippocampus responded to both observation and execution of actions.

Question 29

What is TMS?

Answer 29

A means of disrupting normal brain activity by introducing neural noise - ‘virtual lesion’.

Question 30

What is Faraday’s cell?

Answer 30

Principle of electromagnetic induction

Question 31

What does TMS do?

Answer 31

Applying TMS pulse at any cortical node of the network, it will interfere with the relevant neural signal - efficacy of the neural signal will degrade [observe change in behaviour]

Question 32

What are the advantages of TMS?

Answer 32

• Interference / virtual lesion technique
• Transient and reversible
• Control location of stimulation
• Establishes a causal link of different brain areas and a behavioural task

Question 33

What are functional imaging studies a graded continuum of?

Answer 33

Language lateralization

Question 34

What is transcranial doppler sonography?

Answer 34

Functional lateralisation

Question 35

What did Knecht et al., study find concerning language?

Answer 35

Participants were either left or right language dominant. Tasked with word verification - off line TMS (600 pulses, 10 min, 110% MT). Results documented that language disruption correlated with degree and side of lateralisation

Question 36

What is transcranial electric stimulation (TES)?

Answer 36

TES uses low-level (1 –2 mA) currents applied via scalp electrodes to specific brain regions.

Question 37

What are the protocols for TES?

Answer 37

Transcranial direct current stimulation (tDCS), Transcranial alternating current stimulation (tACS) and Transcranial random noise stimulation (tRNS)

Question 38

What is tDCS?

Answer 38

Anodal facilitation effects [stimulation inhibits GABA]; facilitation effects; Cathodal [stimulation inhibits glutamate]: inhibition effects; Sham (CONTROL) 30sec stimulation

Question 39

What is tACS?

Answer 39

Uses low-level (0.5 - 2 mA) alternating currents applied via scalp electrodes to specific brain regions. The rationale behind tACS is the entrainment (synchronization) of internal brain rhythms with externally applied oscillating electric fields. The oscillatory fields cause the phase-locking of a large pool of neurons, leading to increases in neural synchronization at the corresponding frequency.

Question 40

What is the current generator?

Answer 40

Battery delivers constant current up to 2mA, with 2 sponge electrodes in saline solution (20-35cm^2). The stimulation is less focal, and very safe.

Question 41

When applied in sessions of repeated stimulation, what can tDCS lead to?

Answer 41

To changes in the neuronal excitability that outlast the stimulation itself. Such aftereffects are at the heart of tDCS protocols for clinical application (Nitsche et al., 2011).

Question 42

What is a lucid dream?

Answer 42

A lucid dream can be thought of as an overlap between two states of consciousness – the one that exists in normal dreaming, and the one during wakefulness, which involves higher levels of awareness and control. In lucid dreaming, we transfer elements of waking consciousness into the dream.

Question 43

How is lucid dreaming reflected in brain waves?

Answer 43

When people have lucid dreams, they show gamma waves in the frontal cortex, an activity pattern that is linked to consciousness but is nearly absent during sleep and normal dreaming