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
• Sometimes that isn’t very
useful
• Sometimes we want to know
the overall pattern of potentials
across the head surface
– isopotential map
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
Brain Electrical Source Analysis
• Given this pattern on the scalp,
can you guess where the
current generator was?
Brain Electrical Source Analysis
• Given this pattern on the scalp,
can you guess where the
current generator was?
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
Brain Electrical Source Analysis
This is most likely
location of dipole
Project “Forward
Solution”
Compare to actual data
Brain Electrical Source Analysis
• EEG data can now be coregistered with highresolution 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
Intracranial and “single” Unit
• 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
Intracranial and “single” Unit
• Simultaneous recording from
many electrodes allows
recording of multiple cells
Intracranial and “single” Unit
• Output of unit recordings is
often depicted as a “spike
train” and measured in
spikes/second
Stimulus on
Spikes
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
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?
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
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
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
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
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
The Parts of a Research Proposal
•
•
•
•
•
•
•
Background
Statement of the theory
Prediction(s) that follow from the theory
Experimental Method and Design
Timeline These aren’t necessary for your project
Budget
References
L
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 thisLapplies to your theory, you will make this
constraint explicit in your proposal