Loss of Function Techniques

Or

“Why electrophysiology needs a buddy.”

Questions You’ll Have Answered By The End of Lab…

• What’s wrong with just doing electrophysiology/functional imaging?

• How have psychedelic mushrooms contributed to our understanding of the brain?

• What in the world does Adam do when he’s not teaching?

Inferring the function of an area

Murata et al., 1996

The Problem with Electrophysiology/Functional Imaging

• Correlative

• Still valuable information

• Can point you in the right direction

• Not the whole story

Xkcd.com

Necessity and Sufficiency

• Necessity • Sufficiency

locallocksmiths.com atomictoasters.com

Outline

• Permanent Manipulations– Existing Lesions– Aspirated/Electrolytic Lesions– Ibotenic Acid– Focal Ischemia

• Reversible Manipulations– tDCS– TMS– Cortical Electrical Stimulation– Pharmacological Agents– Transient Cooling – Optogenetics

Existing Lesions

• Cortical Injury

– Stroke

– Head Trauma

• Confirm with Functional Imaging

• Phineas Gage

– PFC

• Advantages and Disadvantages Boston.com and Science Photo Library

Aspiration/Electrolytic Lesions

• Aspiration– Literally remove with small

suction device– Surface Areas

• Electrolytic– Destroy with electrical

current– Areas at Depth

• Classic Technique• What vs. Where• Advantages and

Disadvantages

Padberg et al., 2010

Ibotenic Acid

• Derived from Amanita muscaria mushroom.

• Non-psychoactive component

• Neurotoxin

– Excitotoxic Cell Death

• Destroys only cell bodies

• Advantages and Disadvantages Wikipedia.com

Focal Ischemic Infarct

• Cut off blood supply

• Blood Vessel Ligation

• Electrocoagulation

• Similar to actual ischemic events– Stroke

– Compressed blood vessels

– Sickle Cell Anemia

– Etc.

• Advantages and Disadvantages

Nudo et al., 1996

The Problem with Lesions

Reversible Methods

Non-Invasive Methods

Transcranial Direct Current Stimulation (tDCS)

• Apply continuous DC energy through skin/scalp into cortex

• Anode Cathode

– Current Flow

– Excitation/Inhibition• Exceptions

• Mechanism of Action

– Not completely understood

• Advantages and Disadvantages

George and Aston-Jones, 2010

Transcranial Magnetic Stimulation (TMS)

• Magnetic Induction

– Apply coil

– Pulse magnetic wave

– Current induced

– Single Pulse• Depolarize

– rTMS

• Advantages and Disadvantages

George and Aston-Jones, 2010

Invasive Methods

Cortical Electrical Stimulation

• Lower Electrode into Brain

• Low intensity, brief current

– Activation/priming

• Continuous Pulses

– Deactivation

– Constantly Refractory

• Deep Brain Stimulation

• Advantages and Disadvantages

nimh.nih.gov

Pharmacological Agents

• Muscimol– Amanita muscaria

– Main psychoactive compound

– GABA agonist

• Systemic Administration

• Central Administration

• Advantages and Disadvantages

Wikipedia.com

Gallese et al., 1994

Transient Cooling

• Cool neural tissue to 20 degrees Celsius

– Disrupt or abolish activity

• Brain desires homeostasis

• Gyral and SulcalImplantation

• Advantages and Disadvantages

• This is what Adam does all day.

Coomber et al, 2011

Padberg, Recanzone, Engle, Cooke, Goldring, and Krubitzer, 2010.

Reversible Deactivation of Area 5L

Optogenetics: The Future

• Microbially-derived Opsins

– Control of ion channels via light

• Light sensitivity

– Bred in mice

– Delivered in viral vector

• Advantages and Disadvantages

Web.mit.edu

Your Scenario

• You are a brand new association professor who has just started up their own lab.– Congratulations!

• You want to asses the function of your specific brain area of interest, but wish to go beyond electrophysiology/functional imaging.

• Your university has funds set aside for you to setup your lab, but has no one with whom you can collaborate to perform optogenetics (sad panda).

• Your job: Find a study which recorded from a brain area that you’re interested in and propose a loss of function experiment to test the hypotheses established by the study you read.

What Should be Included?• Length

– No more than 1 page, single spaced, AT THE MOST!

• Summary of recording study– Where did they record from/how did they record– What did they find– What was their model organism

• Methods– Loss of function method appropriate for your organism/question– Use the same stimuli/behavioral task as the recording study. If purely

perceptual, add a simple component that would assess perception of a stimulus (i.e. a button press or some such thing)

• Specific Predictions– Hypotheses based on electrophysiology/functional imaging

• Limitations and Potential Complications– How would you address these?

Details

• Due Date:– Monday, 3/2/15

– BEGINNING OF CLASS (AKA 10:00 a.m. SHARP!)• Even 1 minute late will incur a penalty

– Email or Hard Copy• All technology-related excuses will be thoroughly scrutinized

for bovine excrement.– If you don’t get an confirmation email from me, I didn’t receive it!

• 1 page, at the most!– Could easily complete this assignment in less if all

elements are included

OMG!!! A RESEARCH ASSIGNMENT!?!? WHERE DO I BEGIN???

• Web of Science

– Meet your new best friend

• Lib.ucdavis.edu

– Electronic Databases A-Z

• Go to “W”

• Select “Web of Science” vpn

• Demo to follow

• You may ask me any questions and I will be totally willing to help both in lab today and via email.