Transcript 3680Lecture9.pptx

Midterm 1
Wednesday next week!
Synthesize the Big Picture
Intracranial
• LFP/single-unit
Metabolic
Imaging
Lesion Studies
• fMRI/PET
Extracranial
electrophysiology
• EEG/MEG
Understanding
Brain-wide
neural circuits
Computational
Models
Lesion Studies
• Logic of Lesion Studies:
– damaged area plays a role in accomplishing
whatever task is deficient after the lesion
Lesion Studies
• Types of Lesions
– Animal
– Human
Lesion Studies
• Animal Lesion Techniques
– Aspiration Lesions
– Electrolytic Lesions
Lesion Studies
• Animal Lesion Techniques
– Aspiration Lesions
– Electrolytic Lesions
– Problems:
• These can damage surrounding tissue - especially white
matter tracts nearby (“fibers of passage”)
• Irreversible
• eventual degradation of connected areas
Lesion Studies
• Animal Lesion Techniques
– Vascular Lesions
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endothelin-1
good model of human stroke
severe damage
not pinpoint accuracy
Lesion Studies
• Animal Lesion Techniques
– Reversible Lesions
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cooling
Local anesthetic, other drugs
highly selective
can cool specific layers of cortex
can be reversed!
Lesion Studies
• Animal Lesion Techniques
– Selective Pharmacological lesions
• damage or destroy entire pathways that have a specific sensitivity
to a particular chemical
• e.g. MPTP (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine) model
of Parkinson’s Disease (frozen addicts)
• e.g. scapolomine - acetylcholine antagonist - temporary amnesia
• Can be selective for specific circuits but not for specific brain areas
• can be reversible in some cases (e.g. scopolamine, but not MPTP)
Lesion Studies
• Animal Lesion Techniques
– Gene Knock-Out/Knock-In (Transgenics)
• can selectively block/enhance expression
• Viral vectors, electroporation
• animal develops differently
• Can have temporal/regional/molecular specificity
Lesion Studies
• Human Lesions
– Ischemic Events
• Stroke and Hemorrhage:
– typically due to blood clot or hemorrhage
– size of lesion depends on where clot gets lodged
– amount of damage depends on how long clot remains lodged
Lesion Studies
• Human Lesions
– Trauma
• Frontal lobes are
particularly susceptible
• Some famous cases (e.g.
Phineas Gage)
Lesion Studies
• Human Lesions
– Surgery
• Often surgery done to treat epilepsy
• Occasionally corpus callosum is severed
• Problem: patient wasn’t “normal” before the surgery
Lesion Studies
• Human Lesions
– Transcranial Magnetic Stimulation
• Electromagnet Induces current in the brain
• very transient, very focal reversible “lesion”
• Believed to be safe
• sites that can be studied are limited by the geometry of
the head
Lesion Studies
• Making sense of Lesion studies
Lesion Studies
• Logic of Lesion Studies:
– damaged area plays a role in accomplishing whatever
task is deficient after the lesion
• Warning:
– This isn’t the same as saying the lesioned area “does”
the operation in question
– examples:
• normal behaviour may be altered to accommodate lesion
– e.g. sensory loss of one arm favors other arm
• lesion might cause “upstream problem” or general deficit
– e.g. attention problem “looks like” specific deficit if you only test
one specific demanding task
Lesion Studies
• Designing Lesion Studies
– “design tasks that diagnose the function of
specific operations”
– First, use a control group
Lesion X
Performance
(e.g. accuracy,
speed, etc.)
This difference
indicates deficit
A
Task (e.g. memory task, perception task, etc.)
Healthy
Lesion Studies
• Designing Lesion Studies
– “design tasks that diagnose the function of
specific operations”
– First, use a control group
Performance
(e.g. accuracy,
speed, etc.)
BUT maybe this is just
a general deficit or a
consequence of
having a ANY brain
damage
A
Task (e.g. memory task, perception task, etc.)
Lesion X
Healthy
Lesion Studies
• Designing Lesion Studies
– “design tasks that diagnose the function of
specific operations”
– Consider another lesion group
Lesion X
Lesion Y
Performance
(e.g. accuracy,
speed, etc.)
Healthy
A
Task (e.g. memory task, perception task, etc.)
Lesion Studies
• Designing Lesion Studies
– “design tasks that diagnose the function of
specific operations”
– X marks the double dissociation
Lesion X
Lesion Y
Performance
(e.g. accuracy,
speed, etc.)
Healthy
A
Task (e.g. memory task, perception task, etc.)
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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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
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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
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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
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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
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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
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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