Electrical Signals
This electrical signal, produced when neurons communicate, is the main source of the EEG signal.
What is the postsynaptic potential?
This fast EEG rhythm (roughly >30 Hz) is associated with higher-level cognitive processing.
What is the gamma frequency band?
This quantity measures the ratio between the intensity of the light at a source and a detector.
What is optical density?
This form of hemoglobin carries oxygen to active brain tissue and usually increases during neural activation.
What is oxygenated hemoglobin (HbO)?
This unwanted signal comes from something other than brain activity, such as blinking or head movement.
What is an artifact?
These neurons have long, similarly oriented dendrites that produce most of the EEG signal.
What are pyramidal neurons?
This standardized method places EEG electrodes based on percentages of head measurements.
What is the 10–20 system?
This equation describes how the amount of light absorbed depends on the concentration of a substance and the distance the light travels.
What is the Beer-Lambert Law?
This describes how strongly activity in different brain regions fluctuates together over time.
What is functional connectivity?
This statistical model estimates how strongly brain activity is related to an experimental design, and is the foundation of most fMRI and task-based NIRS analyses.
What is a GLM (General Linear Model)
This electrical signal travels down an axon but is too brief and too small for EEG to measure directly.
What is the action potential?
This ERP component peaks about 170 ms after a face is seen and is larger for faces than many other objects.
What is the N170?
This occurs when light energy is taken up by a material instead of passing through it.
What is absorption?
This imaging plane divides the brain into superior (top) and inferior (bottom) portions.
What is the axial direction?
This process aligns brain images to a common coordinate system or anatomical template.
What is registration?
This is the brain's average electrical response to a repeated event or stimulus.
What is an event-related potential (ERP)?
All EEG voltages are measured relative to this electrode.
What is the reference electrode?
This correction estimates how much farther light travels through tissue because scattering makes its path longer than a straight line.
What is the differential pathlength factor (DPF)?
This is the three-dimensional equivalent of a pixel and is the basic unit of an MRI image.
What is a voxel?
This statistical technique reduces false positives when testing thousands of hypotheses, such as many locations in the brain.
What is multiple comparisons correction?
This is the difference in electrical potential between two locations.
What is voltage?
This processing step subtracts pre-stimulus activity so responses are measured relative to a common starting point.
What is baseline correction?
This process links neural activity to changes in local blood flow and oxygen delivery.
What is neurovascular coupling?
In MRI, this pulse temporarily tips hydrogen atoms out of alignment with the magnetic field.
What is a radiofrequency pulse?
This filter removes high-frequency signals while preserving slower ones.
What is a low-pass filter?