Transcript Week 1

BME 6938
Neurodynamics
Instructor: Dr Sachin S. Talathi
Who am I
• Name: Sachin S. Talathi
• Assistant Professor: 2010-Present
– Primary Appointment: Dept of Pediatrics, Division of
Neurology
– Secondary Appointment: Dept of Neuroscience (Joint) and
Dept of Biomedical Engineering (Affiliate)
• Education:
– Postdoctoral fellow in Biomedical Engineering at Univ of
Florida; 2006-2008
– Ph.D. from University of California, San Diego in Physics
(specialization in Dynamical Systems in
Neuroscience)2001-2006
– Undergrad (Engineering Physics) from Indian Institute of
Technology, Bombay, India 1997-2001
Goal and target audience
• Learn basic biophysics of neurons,, introduction to
dynamical systems modeling and related computer tools
• Specific focus on the study of single cell neuron models, and
mean field models to simulate macro-brain signals
(EEG/MEG/LFP)
• Get experience working in an interdisciplinary environment
Who is the course for?
– The course is for advanced undergraduate and graduate
students in Engineering, Physics, Math and Biological
Sciences who are interested in the application of
mathematical modeling approach to explore the brain.
Who is the Class
10 registered students
•2 BME Major
•2 Physics Major
•6 Electrical Engineering Major
It is a interdisciplinary course as is evidenced from above. In the
past I have had some Medical Sciences students taking this
course as well..
Organization
• Work in groups (Interdisciplinary)
• Homework (60%)
• Final Project: Oral presentation at the end of semesterGraded by peers (40%)
Teaching Approach
• Descriptive biological material and (of course cool
graphics) will be presented via power-point slides
• Mathematical material will be presented on the
white/black-board
• Personal laptops (computers) will become indispensible in
the class as we explore XPPAUTO to simulate differential
equation models for neurons
• Class will be interactive
• From time to time I will post lecture notes and relevant
reading material online
Graphical Outline for the Course
Main Sources
• Foundation of Cellular Neurophysiology; Johnston and Wu
(First 1/4th of the course)
• Dynamical Systems in Neuroscience; Eugene Izhikevich (Later
2/4th of the course)
• Special Topics (Last 1/4th of the course): Source material will
be posted on the web;
• Reference Reading:
– Bard Ermentrout’s website www.pitt.edu/~phase(esp: XPPAUTO
stuff)
– Mathematical Foundations of Neuroscience: Ermentrout and
Terman
– Methods in Neuronal Modeling: C. Koch and I. Segev
– Introduction to Theoretical Neurobiology-Vol 1: Henry Tuckwell
(for more mathematically inclined)
Course Website
• I will use Sakai. Registered students should have access to the
course website using their UFL ID.
• All lecture material will be posted on Sakai a day prior to the
class.
• Hmwks, solutions, extra reading material and any course
related information will be uploaded on sakai as well.
QUESTIONS?
Introduction
Crash course on the anatomy of the
brain
Nervous system
• The central nervous system (CNS)
– Brain
– Spinal cord
• The peripheral nervous system (PNS)
– Somatic (responsible for voluntary movement and action)
– Visceral (also called the autonomic nervous system)
• Sympathetic division
• Parasympathatic division
• Enteric division
The brain: Anatomical Reference
Coronal section
Horizontal section
Mid-Sagittal section
Ventral view
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Facial nerve
Optic nerve
Acoustic nerve
Trigeminal nerve
Olfactory tract
Olfactory bulb
Trochlear nerve
Dorsal view
Macroscopic structure of the brain
Rostral
Forebrain
•Telencephalon (cerebrum)• Cerebral cortex
• Basal ganglia
• Olfactory bulb
•Diencephalon
• Thalamus
• Hypothalamus
Midbrain (upper portion brainstem)
•Tectum
•Tegmentum
Caudal
Embryonic vertebrate brain
Hindbrain (lower portion of brainstem)
•Medulla oblongata
•Pons
•Cerebellum
Cerebral-Cortex
• Is the surface of mammalian brain made up of six layers
(neocortex)
• Strongly folded in “higher” mammals
– Large surface area through folding (sulci)
– Region between adjacent folds is called the gyrus
– Efficient wiring between cortical areas via white
matter (myelinated axons)
• Location of (deep) sulci is consistent across mammalian
species
• Evolution mainly increased the surface of the cortex. Its
vertical organization is relatively constant across species
Cerebral hemisphere
• Two mirror symmetric regions (left brain/ right brain)
• Interconnected via the Corpus callosum (white matter)
• Hemisphere lateralization (preference for one hemisphere)
Cortical areas
• Subdivision according to
– Functional properties
– Histochemical features (cytoarchitecture; eg. Brodman areas)
– Coresspondence between the two subdivision schemes
Eg. Primary visual cortex (V1)=Brodman area 17
Microscopic structures: Brain cells
• Two main types of brain cells
– Glia
• Role in brain development
• Primary function as physical support for neurons by
helping to form myelin sheath around axons of neurons
• Do not take part in brain signaling (passive cells that do not generate
action potential events)
– Nerve cells (neurons)
Excitable cells in the brain: Neurons
Anatomy of a typical neuron
More Detailed View of neuron anatomy
Neuron types
• Classification according to
– Morphology
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Pyramidal cells (cell body has triangular profile, long apical dendrites extending towards cortex surface, basal
dendrites close to cell body)
Stellate cells (star shaped, dendrites extending in all directions)
– Location of cell body
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Basket cells (dense plexus of terminals around soma of target cells)
Purkinje cells (huge neurons in the cerebellum)
– Direction
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Afferent neurons (convey information from tissue to CNS)
Efferent neurons (transmit information from CNS to effector/motor cells)
Interneurons (connect neurons within specific regions of the CNS)
– Action on to other neurons
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Excitatory
Inhibitory
– Electrophysiological properties (related to dynamical properties)
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Tonic spiking
Phasic or bursting
– Neurotransmitter production
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Cholinergic neurons
GABAergic neurons
Glutamergic neurons
Dopaminergic neurons
Serotonergic neurons
The neuronal cell membrane
Excitability of neuron
Note:
The convention is that
membrane potential is
measured in reference to
the potential of extra
cellular medium
Conduction of nerve impulse
Unmyelinated axon
Animation of impulse propagation
Myelinated axon
Cortical connectivity: Synapses
• Communication between neurons happen through synapses
– Electrical synapses (gap junctions)
• Direct electrical contact between two cells through membrane proteins which span
both the connecting cells
• Typically found between coupled GABAergic interneurons
– Chemical synapses
• Signaling between pre- and post synaptic neurons via neurotransmitters which
diffuse across the synaptic cleft
Chemical synapse operation
Chemical synapses: Some facts
• Slower than electrical synapse in communication
• Suseptible to change (learning) through
– Changes in amount of neurotransmitter release
– Post synaptic ion channel density
• The post synaptic effect depends on the neurotransmitter
released, the receptor and the ion channel type
– Binding of Glutamate at NMDA receptors
• Opening of nonselective Ca2+ channels
• Ca2+ inflow
• Depolarization of postsynaptic membrane i.e. excitation
– Binding of GABA at GABA receptors
• Opening of Cl- channels
• Cl- influx
• Hyperpolarization i.e., inhibition
• The effect also depends on the postsynaptic membrane reversal
potentials; which in turn depend on ion concentrations