cse 599e lecture 3: recording/stimulation techniques · r. rao, 599e: lecture 3 7 from spikes to...

1 R. Rao, 599E: Lecture 3

CSE 599E

Lecture 3:

Recording/Stimulation Techniques

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What’s on the menu?

F Recording and Stimulation Techniques Invasive

Semi-Invasive

Non-Invasive

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Components of Brain-Computer Interfacing

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Invasive Recording

Intracellular Recording

at the Soma

Extracellular Recording

near the Soma soma (cell body)

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Intracellular Recording using Patch Clamp

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Array of silicon electrodes with platinum-plated tips

Extracellular recording of neural spikes

Array is implanted in an area of the cerebral cortex

(Work of Andersen & colleagues, Caltech)

Extracellular Recording using Multielectrode Arrays

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From Spikes to Firing Rate

Extracellular spike train

Rectangular Window (100 ms)

Sliding Window (100 ms)

Gaussian Window ( = 100 ms)

Causal Window (1/ = 100 ms)

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From Firing Rates to Tuning Curves: Tuning Curve of a Neuron in Primary Motor Cortex (M1)

Spike trains as a function of hand reaching direction

Cosine Tuning Curve

Preferred direction

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Movement Direction can be Predicted from a

Population of M1 Neurons’ Firing Rates

Population vector = sum of

preferred directions weighted

by their firing rates

Population vectors

(decoded movement

direction)

Actual arm movement

direction

Actual arm movement

direction

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Somatotopic

Organization of

M1 (a.k.a. the

“homunculus”)

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Semi-Invasive Recording

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Electrocorticography

(photo courtesy Seattle Times)

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Optical Imaging

Transgenic mouse

expressing green

fluorescent protein

(GFP) in a

subpopulation of

neurons

Oregon Green

calcium

sensitive dye

stained

neurons

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Non-Invasive Recording

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Electroencephalography (EEG)

10-20 System for Electrode Locations

Measures electrical fluctuations caused by post-synaptic

potentials from thousands of neurons oriented radially to scalp Tens of microvolts range

Poor spatial resolution (cm2)

Good temporal resolution (ms)

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Example of EEG Oscillatory Potentials

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Magnetoencephalography (MEG)

Measures magnetic fields produced by activity of thousands of

cortical neurons oriented perpendicular to the cortical surface Magnetic fields not distorted by skull and scalp

Better spatial resolution than EEG

Expensive and bulky

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Functional Magnetic Resonance Imaging (fMRI)

F Measures changes in blood

flow due to increased

activation of neurons in an

area

F Relies on paramagnetic

properties of oxygenated

and deoxygenated

hemoglobin in the blood

F Produces images showing

blood-oxygenation-level-

dependent signal changes

(BOLD)

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Example fMRI Images (word reading task)

http://www.med.nyu.edu/thesenlab/group/fmri.html

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Functional Near-Infrared Spectroscopy (fNIR)

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Stimulation

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Extracellular Microelectrodes

F Examples: Cochear implant, DBS

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Microstimulation can alter decision making

(Hanks et al., 2006)

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Transcranial Magnetic Stimulation (TMS)

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Next Class:

Signal Processing and

Machine Learning for BCI