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

Disadvantagesnimh.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 Sulcal

Implantation• 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.