Evoked potential

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Applicable to over 40 research fields
 Cardiovascular and
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Learning outcomes:
• Introduction to ERPs
• Theory and guidelines for recording ERPs
• How to record great ERPs data
• How to use the BIOPAC Stimulus Presentation
(BSP) utility (AcqKnowledge®) to create
stimulus delivery paradigms
• How to record ERP-fNIRS response to oddball
paradigm task (P300) in real and virtual world
• How to prepare data for analysis
• Workflow Automation Tools
Evoked Potentials Part 2:
Event-related or Endogenous Evoked Potentials (ERP)

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• Nyquist/ Sampling Theorem: Signal: 0 to fN; Minimum sampling frequency 2fN,
(fN/ Nyquist frequency); Sampling at a frequency lower than twice the Nyquist
frequency produces aliasing (distortion of the signal)
• ADC: Quantization and sampling (Interval/ frequency)
• Differential input amplifies the difference in potential presented at its two
inputs (active and reference), while rejecting any signal common to both
inputs
• Common mode rejection ratio (CMRR): An amplifier's ability to reject
common signals
• SNR for a random signals is √n, where n is the number of epochs averaged;
SNR of 20 requires averaging 400 epochs
ERP: Basic concepts
Spehlmann, 1985

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• P300 is generated when there is a match between bottom-up sensory inputs and top-down
expectancies
• Latency is about 300 ms in simple auditory tasks to more than 700 ms in complex visual tasks
• P300 not a unitary phenomenon
• Neural generators: Hippocampus, temporal, parietal and frontal lobes
• Higher level processing that involves selective attention, memory updating, semantic
comprehension etc.
• P300 reflects stimulus evaluation time rather than response selection
• Latencies of ERP components track the time course of processing activity in milliseconds,
whereas their amplitudes indicate the extent of allocation of neural resources
• P300 amplitude varies as a function of stimulus probability (both objective and subjective),
certainty of the subject about the response, the amount of information transmitted by a
stimulus, among others
Event related evoked potentials
IFCN Guidelines

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Audio demonstration
Auditory oddball paradigm
Oddball paradigm animation
Target Target

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Event related evoked potentials

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Analysis of ERPs
Auditory oddball paradigm