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The Event-Related Potential (ERP)

The Event-Related Potential (ERP). We have an ERP waveform for every electrode. The Event-Related Potential (ERP). We have an ERP waveform for every electrode Sometimes that isn’t very useful. The Event-Related Potential (ERP). We have an ERP waveform for every electrode

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The Event-Related Potential (ERP)

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  1. The Event-Related Potential (ERP) • We have an ERP waveform for every electrode

  2. The Event-Related Potential (ERP) • We have an ERP waveform for every electrode • Sometimes that isn’t very useful

  3. The Event-Related Potential (ERP) • We have an ERP waveform for every electrode • Sometimes that isn’t very useful • Sometimes we want to know the overall pattern of potentials across the head surface • isopotential map

  4. The Event-Related Potential (ERP) • We have an ERP waveform for every electrode • Sometimes that isn’t very useful • Sometimes we want to know the overall pattern of potentials across the head surface • isopotential map Sometimes that isn’t very useful - we want to know the generator source in 3D

  5. Brain Electrical Source Analysis • Given this pattern on the scalp, can you guess where the current generator was?

  6. Brain Electrical Source Analysis • Given this pattern on the scalp, can you guess where the current generator was? Duracell

  7. Brain Electrical Source Analysis • Source Analysis models neural activity as one or more equivalent current dipoles inside a head-shaped volume with some set of electrical characteristics

  8. Brain Electrical Source Analysis Project “Forward Solution” This is most likely location of dipole Compare to actual data

  9. Brain Electrical Source Analysis • EEG data can now be coregistered with high-resolution MRI image

  10. Intracranial and “single” Unit • Single or multiple electrodes are inserted into the brain • “chronic” implant may be left in place for long periods

  11. Intracranial and “single” Unit • Single electrodes may pick up action potentials from a single cell • An electrode may pick up thecombined activity from several nearby cells • spike-sorting attempts to isolate individual cells

  12. Intracranial and “single” Unit • Simultaneous recording from many electrodes allows recording of multiple cells

  13. Intracranial and “single” Unit • Output of unit recordings is often depicted as a “spike train” and measured in spikes/second Stimulus on Spikes

  14. Intracranial and “single” Unit • Output of unit recordings is often depicted as a “spike train” and measured in spikes/second • Spike rate is almost never zero, even without sensory input • in visual cortex this gives rise to “cortical grey” Stimulus on Spikes

  15. Intracranial and “single” Unit • By carefully associating changes in spike rate with sensory stimuli or cognitive task, one can map the functional circuitry of one or more brain regions • What are the advantages and limitations of this approach?

  16. Your Research Proposal Project • A research proposal attempts to persuade the reader that: • The underlying question is highly important • The proposed methodology and experimental design is the best available approach • That you have the knowledge and talent to do the proposed research • That you have a research program worth funding L

  17. Your Research Proposal Project • A research proposal is therefore similar to many other situations in which you will try to persuade someone of something • The skill is portable L

  18. Your Research Proposal Project • As in other situations, your reader should be assumed to be unconvinced and thus unwilling to spend much time and energy entertaining your argument! • You must make your argument easy and fast • The key to that is organization L

  19. Research Proposals Should be “Theory Driven” • Most proposals are organized around a specific theory • What is the difference between a theory and a question? L

  20. The Parts of a Research Proposal • Background • Statement of the theory • Prediction(s) that follow from the theory • Experimental Method and Design • Timeline • Budget • References L

  21. The Parts of a Research Proposal • Background • Statement of the theory • Prediction(s) that follow from the theory • Experimental Method and Design • Timeline • Budget • References These aren’t necessary for your project L

  22. Assignment • Rules: • Must be human Cognitive Neuroscience • Experimental approach may involve animal research only if this is the best way to test your theory • Studying humans is preferable to studying animals when you have a specific theory about human cognition • One moves to animal research because it tells you something that human research cannot • If this applies to your theory, you will make this constraint explicit in your proposal L

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