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




• Sometimes we want to know the overall pattern of potentials across the head surface– isopotential map




• 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

Brain Electrical Source Analysis

• Given this pattern on the scalp, can you guess where the current generator was?


• Given this pattern on the scalp, can you guess where the current generator was?


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


This is most likely location of dipole

Project “Forward Solution”

Compare to actual data


• EEG data can now be coregistered with high-resolution MRI image

Intracranial and “single” Unit

• Single or multiple electrodes are inserted into the brain

• “chronic” implant may be left in place for long periods


• Single electrodes may pick up action potentials from a single cell

• An electrode may pick up the combined activity from several nearby cells– spike-sorting attempts to

isolate individual cells


• Simultaneous recording from many electrodes allows recording of multiple cells


• Output of unit recordings is often depicted as a “spike train” and measured in spikes/second

Stimulus on

Spikes


• 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


• 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?

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

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• A research proposal is therefore similar to many other situations in which you will try to persuade someone of something– The skill is portable

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• 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 organizationL

Research Proposals Should be “Theory Driven”

• Most proposals are organized around a specific theory

• What is the difference between a theory and a question?

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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

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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

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These aren’t necessary for your project

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

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

Documents

electrode slide

useful slide

d slide

single unit single electrodes

actual data slide

erp waveform

research proposal project

single cell