Lecture 3 - Methods in Cognitive Neuroscience

Vocabulary based on cognitive neuroscience experimental methods, imaging techniques, and neural manipulation tools.

Reaction times

A behavioral method used to measure the time-course of information processing.

Posner (1986)

Demonstrated that participants process the physical identity of words, then phonetic identity, and finally category information.

Double dissociation

Very strong evidence from brain damage studies (e.g., Broca’s vs Wernicke’s areas) where one lesion impairs function A but not B, and another lesion impairs B but not A.

Computerized Tomography (CT Scan)

A neuroscientific method that uses x-ray technology to compress a 3D object into a 2D image.

Magnetic Resonance Imaging (MRI)

Uses a powerful magnetic field between $0.5T-3.0T$ to construct brain images based on the position of magnetically charged protons of hydrogen atoms in oxygenated blood.

Diffusion Tenor Imaging (DTI)

A variation of MRI used to study the anatomic structure of white matter axons by measuring the density and flow of water molecules.

Temporal Resolution

The accuracy with which one can measure when an event is occurring in the brain; ranges from millisecond resolution (EEG/MEG) to minutes (PET).

Spatial Resolution

The accuracy with which one can measure where an event is occurring in the brain; can range from the millimeter level to individual neurons.

Invasiveness

Refers to whether the equipment is located inside or outside the body; for example, PET is invasive due to radio-labeled isotope injections.

Deep Brain Stimulation

A surgical procedure where electrodes are implanted to stimulate the subcortex, often used for medication-resistant Parkinson’s by targeting the subthalamic nucleus of the basal ganglia.

Knockout procedure

A genetic manipulation typically done in low-lifespan animals where they are bred so that a specific gene does or does not express itself.

Optogenetics

An invasive technique using a virus to create light-sensitive ion channels on neurons to manipulate neural firing with specific wavelengths of light.

Transcranial Magnetic Stimulation (TMS)

Known as a "virtual lesion technique," it uses an external coil to deliver targeted pulses that temporarily excite or inhibit a focal group of neurons of approximately $1\text{cm}^2$.

Transcranial Direct Current Stimulation (tDCS)

A non-invasive method using an anode and cathode to pass a weak electric current between two scalp electrodes to influence cortical excitability.

Single-cell Recordings

A highly invasive microelectrode system that measures the electro-physiological responses of a single neuron with very precise spatial and temporal resolution.

Electrocorticography (ECoG)

A method where electrodes are surgically implanted directly onto the surface of the brain, usually in patients undergoing surgery for epilepsy.

Electroencephalography (EEG)

A non-invasive, inexpensive method that measures scalp-recorded electrical activity reflecting the summation of electrical activity from postsynaptic cells.

Event Related Potentials (ERPs)

Consistent patterns of EEG triggered by a stimulus, defined by polarity, latency, scalp location, and sensitivity to experimental manipulations.

Magnetoencephalography (MEG)

Measures electrical activity via magnetic fields; requires a magnetically shielded room and sensors kept under $-269\text{ }^\text{o}\text{C}$.

Positron Emission Tomography (PET)

An invasive measure of blood flow and oxygen use using radio-labelled oxygen or glucose, with a spatial resolution of approximately $1\text{ cm}$.

Blood Oxygen Level Dependent (BOLD)

The signal measured by fMRI based on the ratio of oxygenated to deoxygenated hemoglobin; deoxyhemoglobin is paramagnetic and suppresses the signal.

Multi-Voxel Pattern Analysis (MVPA)

A technique that looks at activation patterns across many voxels to identify if specific populations within a region drive different cognitive functions.

Converging Methods

The practice of using multiple techniques together (e.g., EEG and fMRI) to compensate for the individual weaknesses of each method.

Connectivity

The concept that most cognitive functions result from the simultaneous activity of multiple brain regions, revealed by correlated patterns of activity.