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Neurophysiology

Neurophysiology. Recording electrical activity in the brain. http://play.psych.mun.ca/~smilway/. Types of Recording. Acute or chronic Spontaneous or Evoked Sensory (touch, light, sound) Chemical (injection, pipette, microdialysis) Electrical (Electode)

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Neurophysiology

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  1. Neurophysiology Recording electrical activity in the brain http://play.psych.mun.ca/~smilway/

  2. Types of Recording • Acute or chronic • Spontaneous or Evoked • Sensory (touch, light, sound) • Chemical (injection, pipette, microdialysis) • Electrical (Electode) • Intracellular, extracellular, juxtacellular • In Vivo, In Vitro

  3. Simplest Preparation • Record Spontaneous Electrical Activity using a single electrode. • Recording Electrodes • Micropipette(intra-, extra- or juxtacellular) • Fine wire (extracellular) • Carbon fibre (extracellular) • Ground or Reference

  4. http://www.psych.umn.edu/courses/fall05/burkhardtd/psy3031/images/microelectrode.jpghttp://www.psych.umn.edu/courses/fall05/burkhardtd/psy3031/images/microelectrode.jpg Stimulating Electrodes Recording Electrodes

  5. The not so simple setup

  6. Recording • The recording electrode or the micropipette’s silver wire is connected to the G1 pole of the amplifier input. • The ground (screw) is connnected to the G2 pole. The signal on G2 (background) is subtracted from G1. (Differential amplification)

  7. Amplifier • The Amplifier amplifies and filters the signal. • Amplifier output goes to: • Oscilloscope • A to D Converter

  8. Oscilloscope X-axis: Time Y-axis: Voltage

  9. A to D Converter • Analog toDigital • Voltages -10V to +10V are assigned a digital value 0  4095 • Digital value can be stored on computer.

  10. A to D conversion • Sampling Rate • Temporal Resolution • Digitization Range • Voltage Resolution

  11. Ato D Sampling Rate & Temporal Resolution

  12. A to D Digital Range & Voltage Resolution • 4096 points • 4 settings: • -10V to +10V Resolution: 4.88mV • -5V to +5V Resolution: 2.44mV • -2.5V to +2.5V Resolution:1.22mV • -1.25V to +1.25V Resolution: 0.61mV • Maximize use of the range, but avoid clipping. 20V 20V

  13. Here the signals from the rat are seen in the oscilloscope (top) and on the computer monitor after being digitized by the AtoD Converter.

  14. Add Electrical Stimulation Many experiments examine connectivity by looking at response evoked by electrical stimulation to input.

  15. Electrical Stimulation • Monopolar • Anodal • Cathodal (electrons flow cathode  anode) • Bipolar • Twisted wire • Concentric

  16. D to A Conveter • This particular stimulator is gating a pulse from a computer to administer the stimulation. • The D to A converter converts a digital input to a voltage.

  17. Heater • Under anaethesia animal will not regulate temperature very well. • A heater can be added to maintain the animals temperature at a constant level

  18. Computer • A computer is usually used to control the experiment and collect and analyze the data. • Specialized software packages for neurophysiology are available. We use Expeimenter Workbench by DataWave.

  19. The Circuit

  20. The Preparation • Recording Electrode in Granule Cell Layer of Dentate Gyrus • Stimulating Electrode in Perforant Path • Cannula in Locus Coeruleus

  21. The Evoked Response

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