1. Recording electrical activity in the brain
Neurophysiology
Recording electrical activity in the brain

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. 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 to Digital
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