BME 6938 Neurodynamics Instructor Dr Sachin S Talathi

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 macrobrain 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 semester. Graded 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 1/4 th of the course) • Dynamical Systems in Neuroscience; Eugene Izhikevich (Later 2/4 th of the course) • Special Topics (Last 1/4 th 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 1. 2. 3. 4. 5. 6. 7. 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 (V 1)=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 • • 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 • • Basket cells (dense plexus of terminals around soma of target cells) Purkinje cells (huge neurons in the cerebellum) – Direction • • • 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 • • Excitatory Inhibitory – Electrophysiological properties (related to dynamical properties) • • Tonic spiking Phasic or bursting – Neurotransmitter production • • • 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 Ca 2+ channels • Ca 2+ 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