Pre-start
Announcements
- Homework 1 "due" Tuesday around midnight
- GHK derivation SHOULD NOT end up complicated. Think about what things mean. Intuition sets up the math and math is just high school algebra (mostly...maybe some precal outside of taking one integral)
- I have the question written for APs & Synapses will upload today after class
- Happy to help! Just ask!
Neural Signal Processing & Machine Learning
ELEC/BIOE 548 | ELEC 483
Fall 2022
Episode 7: Final cellular anatomy things! & Electrical signals from the brain!
1
Introduction. Class & brains
2
Fundamental neurobiology. How do neurons fire? How/what do we record?
3
Modeling spike trains. First bit of analysis work and understanding firing properties of neurons.
5
Classification. Making machines learn. Which direction is a monkey trying to reach? Bayesian decoding.
4
Point processes. Continued modeling work of neurons.
6
Clustering/Mixture models. Making machines learn some more. Spike sorting.
Bi-weekly Schedule
7
Continuous decoding. Kalman filters. Machines continue to learn.
8
Spectral analysis? LFP interpretation in spectral domain. But also kinda in clustering.
Neuroscience!
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Introduction to Neuroscience
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Ch 1: The brain and behavior
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Ch 2: Nerve cells and behavior
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How are neural signals generated?
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Ch 7: Membrane potential
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Ch 9: Propagated Signaling: the action potential
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How do neurons communicate with each other? - Finish!
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Ch 10: Overview of synaptic transmission
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Ch12: Synaptic integration
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Brain Signals!
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How can we measure neural activity? -- Today!
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What info do neurons encode in trains of action potentials (“spike trains”)?
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How can we model “statically” encoded information?
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Estimation/”decoding”
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How can we model/decode “dynamic” information? (filtering, Kalman, HMM)
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Signal conditioning – “spike sorting” (PCA, Expectation-Maximization)
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Beyond spike trains (LFP, EEG, imaging)
Brain Signals!
EPHYS
Spikes
(Neuron) Base unit of measurement. Single cell activity.
Spikes can be "decoded" from other ephys modalities!
Spikes
Intra- vs Extra-cellular
Intra-cellular recording at soma (APs and subthreshold potentials
Extra-cellular recording near soma (APs, no sub threshold potentials
Intra-cellular recording in axon (APs, no subthreshold potentials)
Spikes
Hubel & Weisal CAT!!
LFP
Decoding LFP
Spike Sorting
ECoG/EEG
ECoG/EEG
ECoG/EEG
Brain Signals
Alternatives to Ephys
- Noninvasive
- fMRI (Functional magnetic resonance imaging)
- MEG (Magnetoencephalography)
- fNIRS (Functional near-infrared spectroscopy)
- Invasive
- Calcium Imaging
APs
- -50 to -55 mV threshold was more accurate!
- Propagates down axon!
- Why doesn't it propagate the other way? HW question!
APs
- -50 to -55 mV threshold was more accurate!
- Propagates down axon!
- Why doesn't it propagate the other way? HW question!
- Myelin sheath wraps large axons
- made from glial cells
- Schwan cells in PNS
- Ogliodendrocyte in CNS
- Increases spread of AP prop
- Nodes of Ranvier (APs regenerated)
- made from glial cells
Synapses!
Synapses!
Synapses!
Synapses!
Excitatory: Glutamate, ACh,…
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Inhibitory: GABA, Glycine,…
Synapses!
Drugs!
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SSRIs/SNRIs
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It takes several weeks before SSRIs have effect but serotonin levels rise immediately after (within an hour)! This may not be what directly influences depression levels!
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SNRIs also supposedly work for chronic pain, anxiety.
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Synapses!
Drugs!
- Benzodiazepines
- Severe anxiety, PTSD, sleep disorders, etc.
- PTSD exposure therapy however may be inhibited ineffectiveness with this drug at play
- Gabapentin
- Chronic pain & seizure med. Reduces the release of several monoamine neurotransmitters. inhibits voltage-activated Na+ channels, but other results contradict these findings
ELEC548 Lec7
By Shayok Dutta
