Midterm 1

Wednesday next week!

Synthesize the Big Picture

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

• endothelin-1• good model of human stroke• severe damage• not pinpoint accuracy

Lesion Studies

• Animal Lesion Techniques– Reversible Lesions

• 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

Performance(e.g. accuracy, speed, etc.)

Task (e.g. memory task, perception task, etc.)A

Lesion X

HealthyThis difference indicates deficit

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.)

Task (e.g. memory task, perception task, etc.)A

Lesion X

Healthy

BUT maybe this is just a general deficit or a consequence of having a ANY brain damage

Lesion Studies

• Designing Lesion Studies– “design tasks that diagnose the function of

specific operations”– Consider another lesion group

Performance(e.g. accuracy, speed, etc.)

Task (e.g. memory task, perception task, etc.)A

Lesion X

Healthy

Lesion Y

Lesion Studies

• Designing Lesion Studies– “design tasks that diagnose the function of

specific operations”– X marks the double dissociation

Performance(e.g. accuracy, speed, etc.)

Task (e.g. memory task, perception task, etc.)A

Lesion X

Healthy

Lesion Y

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 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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