INP_Pre Slides 15.04.2024.pdf

Introduction to neural signal analysis Brandenburg University of Technology Summer semester 2024 1 References: 2 Goals of the course To understand o Basic knowledge of neural signals and specifically EEG...

Introduction to neural signal analysis Brandenburg University of Technology Summer semester 2024 1 References: 2 Goals of the course To understand o Basic knowledge of neural signals and specifically EEG signal, their origin and generation o What problems and needs are related to the acquisition and processing of EEG o What kind of methods are available and get an idea of they are applied and which kind of problem To get to know how we can analysis the EEG signals appropriately to get reliable results. 3  Neuron Cells of the Cell body (soma): spherical central part of the nervous system neuron (diameter : 20 μm), contains nucleus, cytoplasm (organelles, cytosol,..). Glial dendrites: receive signals from neighboring Neuron cells neurons (like a radio antenna). support the signaling functions of axon: transmit signals over a distance (like nerve cells. repairing nervous system electrical signaling over telephone wires) long distances Damage. Acting as stem cells in some axon terminal: transmit signals to other neuron brain areas. In other regions, they prevent dendrites or tissues (like a radio transmitter) regeneration where uncontrolled regrowth might do more FIGURE 2. 4, Neuroscience, exploring the brain, Fourth edition ,Edited by M.F Bear 4 The axon and axon collaterals. The axon functions like a telegraph wire to send electrical impulses to distant sites in the nervous system. The arrows indicate the direction of information flow. The process by which the information encoded by action The axon terminal and the synapse. Axon terminals form synapses with the dendrites or potentials is passed on at somata of other neurons. When a nerve impulse arrives in the presynaptic axon terminal, synaptic contacts to a target neurotransmitter molecules are released from synaptic vesicles into the synaptic cleft. cell is called synaptic Neurotransmitter then binds to specific receptor proteins, causing the generation of transmission. electrical or chemical signals in the postsynaptic cell. 5 FIGURE 2.15 and 2.16 , Neuroscience, exploring the brain, Fourth edition ,Edited by M.F Bear Some of the diverse nerve cell morphologies The variation in the size and branching of dendrites is cause to different information-processing capacity of individual neurons. The number of inputs to a single neuron reflects the degree of convergence, while the number of targets innervated by any one neuron represents its divergence. Asterisks indicate that the axon runs on much farther than shown. Note, however, that some cells, such as the retinal bipolar cell, have very short axons, while others, such as the retinal amacrine cell, have no axon at all. The drawings are not all at the same scale. 6 Fig1.2, Neuroscience, six edition ,Edited by Dale Purves  Distribution of ions across the membrane Basic rules for Ion movements: Na+ K+ + + + ++++ +  From Higher to Lower concentration. + + + + - -- - - + + Cl- + + + -- + K+ - Ca2+  Away from like charge and toward to opposite charges. ATP OA- Na+ - + Cl- + + Ca2+  Membrane permeability (ion channels). Cell membrane Membrane potentials : Electrical charge difference difference across the cell membrane 7  EXAMPLE : If the membrane is equally permeable to both ions - - - + + - + - + - - + + + + - - + + - + + + + - - - + + + - + + - - - + - - - + + + + + - - - + - + - + - + - Na+ Cl- Na+ Cl- Na+ Cl- Na+ Cl- Concentration Membrane 10 10 2 2 6 6 6 6 potential = 0 Electric charges 0 0 0 0  If the membrane is only permeable to Na ions - - - + + + + - + - - - + - - + + - + Diffusion - + - + + + - + + - - + + + + Electrostatic + + - - - - - - + - - + - + + + 𝐸𝑁𝑎 = 6 + No net current for Na + - + - + - + - Na+ Cl- Na+ Cl- Na+ Cl- Na+ Cl- Concentration 10 10 2 2 7 10 5 2 Electric charges 0 0 -3 +3  Equilibrium potential Na+ K+ + ++++ + --- - - + + Cl- FIGURE 3.14, Neuroscience, exploring the brain, Fourth edition ,Edited by M.F Bear -- + K+ - Ca2+ The electrical potential difference that exactly balances an ionic concentration gradient is called an ionic equilibrium potential (𝐸𝑖𝑜𝑛 ( ATP OA- Na+ 𝑖𝑜𝑛 0𝑢𝑡 𝐸𝑖𝑜𝑛 = 2,0303 RTൗzF log 𝑖𝑜𝑛 𝑖𝑛𝑠𝑖𝑑𝑒 Cl- Ca2+ Eion = ionic equillibrium potential R =gas constant T= absolute temperature Cell membrane Z=charge of the ion F= Faradays constant [ion]out = ionic concentration outside the cell 10 [ion]inside = ionic concentration inside the cell Equilibrium potential 𝐾+ 0 𝐸𝐾 = 61.54 mV log 𝐾+ 𝑖 𝑁𝑎+ 0 𝐸𝑁𝑎 = 61.54 mV log 𝑁𝑎+ 𝑖 𝐶𝑙− 0 𝐸𝐶𝑙 = 61.54 mV log 𝐶𝑙− 𝑖 𝐶𝑎2+ 0 𝐸𝐶𝑎 = 30.77 mV log 𝐶𝑎2+ 𝑖 𝑖𝑜𝑛 0𝑢𝑡 𝐸𝑖𝑜𝑛 = 2,0303 RTൗzF log 𝑖𝑜𝑛 𝑖𝑛𝑠𝑖𝑑𝑒 𝐾+ 0 1 If = 20 𝐓𝐡𝐞𝐧 𝐸𝐾 = −80 mV 𝐾+ 𝑖 𝑁𝑎+ 0 If = 10 𝐓𝐡𝐞𝐧 𝐸𝑵𝒂 = 61.54 mV 𝑁𝑎+ 𝑖 11  Resting membrane potential If the membrane of a real neuron were permeable only to K, the resting membrane potential would equal EK, about 80 mV. But it does not; the measured Na+ K+ resting membrane potential of a typical neuron is about 65 mV. This discrepancy is explained because real neurons at rest are not exclusively permeable to K; there is also some Na permeability. Stated another way, the Cl- relative permeability of the resting neuronal membrane is quite high to K and low to Na. K+ Ca2+ The resting membrane ion permeability to K is 40 times greater than it is to Na ATP OA- Na+ Goldman Equation Cl- Ca2+ 𝑃𝑘 𝐾 + 𝑜 + 𝑃𝑁𝑎 𝑁𝑎+ 𝑜 𝑉𝑚 = 61.54 𝑚𝑉 𝑙𝑜𝑔 𝑃𝑘 𝐾 + 𝑖 + 𝑃𝑁𝑎 𝑁𝑎+ 𝑖 Cell membrane Vm : membrane potential relative Pk: permeability to K PNa: permeability to Na 12  Membrane channels Leak Channels Sodium-potassium pump Voltage gated channels This ion pump is a membrane-associated The voltage gated channel gated by a change in The leak channels are normally opened but protein that transports ions across the voltage across the membrane. Thus, the entire they have different permeability for different membrane against their concentration segment can be forced to move by changing the ions. gradients at the expense of metabolic membrane potential. energy. FIGURE 4.5, FIGURE 4.8 and FIGURE 4.8, Neuroscience, exploring the brain, Fourth edition ,Edited by M.F Bear 13 Action potential (AP) 2 At this stage, Na+ ions flood down their concentration gradient into the cell. Then, the membrane potential rapidly moves towards the equilibrium potential for Na+ (~ +60 mV). However, the membrane potential does become positive, it does not attain the Na+ equilibrium potential because the sodium channels quickly close. 3 some sodium channels open, followed by many other channels when the depolarization attains threshold for triggering the action potential. 1 There are two separate mechanisms controlling the gating The initial resting potential is of the sodium channel: approximately –65 mV, at which time 1. ‘Activation’ gate, which opens in response to a depolarizing both the voltage-gated sodium and stimulus. potassium channels are closed. 2. Inactivation gate, which gate closed approximately 1 ms after the activation gate opens 14 Allan Fletcher, Action potential: generation and propagation, Anaesthesia & Intensive Care Medicine,Volume 12, Issue 6,2011,  Action potential … 4 Approximately 1 ms after opening, the voltage-gated sodium channels close. At this time, the voltage-gated potassium channels open, allowing K+ ions to ‘flood’ out of the cell to rapidly repolarize the membrane. 5 The voltage-gated potassium channels actually remain open long enough for the membrane potential to ‘undershoot’ the resting value transiently. (the relative refractory period), the sodium channels are again responsive but a larger depolarizing stimulus is required to trigger an action potential. The all-or-none law is a principle that states that the strength of a AP is not dependent upon the strength of the stimulus. 15 Allan Fletcher, Action potential: generation and propagation, Anaesthesia & Intensive Care Medicine,Volume 12, Issue 6,2011,