The Event-Related Potential (ERP) Embedded in the EEG signal is the small electrical response due to specific events such as stimulus or task onsets, motor actions, etc.

The Event-Related Potential (ERP) Embedded in the EEG signal is the small electrical response due to specific events such as stimulus or task onsets, motor actions, etc. Averaging all such events together isolates this event-related potential

Basic Elements of ERP Design EEG, therefore ERP, doesn’t provide interpretable absolute voltage The voltage is always relative to something else That something else may be: – The pre-stimulus baseline – A control condition

Basic Elements of ERP Design Thus a fundamental aspect of ERP design is not to plan to report voltages but rather a difference in voltage between two or more conditions What are some examples of conditions you might want to compare?

First Demo Contralaterality in Visual System – Hemifields project to contralateral cortex – Unrelated to which eye is stimulated! Occular Albinism – Eyes project contralterally, irrespective of hemifield

Basic Elements of ERP Design The theory is that human visual cortex is organized contralaterally The prediction is that right hemifield stimuli will drive electrical activity in the left visual cortex and left hemifield stimuli will drive electrical activity in right visual cortex How do we test that prediction?

Basic Elements of ERP Design Experimental approach: Choices: – 1. you could compare ipsi to contra ERP waveforms with a trial E.g. O3 with O4 What’s the problem? O3 O4

Basic Elements of ERP Design Experimental approach: Choices: – 1. you could compare ipsi to contra ERP waveforms with a trial E.g. O3 with O4 What’s the problem? You would be comparing ERPs from different parts of the brain! How could you improve on that design?

Basic Elements of ERP Design Experimental approach: Choices: – 2. you could compare electrodes ipsi to stimulus on one side with electrodes contra to stimulus on the other side Notice those are the same electrode! Measure contralateral ERP magnitude O3

Basic Elements of ERP Design Experimental approach: Choices: – 2. you could compare electrodes ipsi to stimulus on one side with electrodes contra to stimulus on the other side Notice those are the same electrode! Measure ipsilateral ERP magnitude O3

Basic Elements of ERP Design Hands on agenda today: – Review recording and saving EEG data – Exporting EEG.ses to.raw – File management and backing up data – Intro to BESA and constructing an ERP wavform