Transcript Neurophysiology - Memorial University of Newfoundland

Neurophysiology
Recording electrical activity in the
brain
http://play.psych.mun.ca/~smilway/
Types of Recording
Acute or chronic
Spontaneous or Evoked
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Sensory (touch, light, sound)
Chemical (injection, pipette, microdialysis)
Electrical (Electode)
Intracellular, extracellular, juxtacellular
In Vivo, In Vitro
Simplest Preparation
Record Spontaneous Electrical Activity
using a single electrode.
Recording Electrodes
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Micropipette(intra-, extra- or juxtacellular)
Fine wire (extracellular)
Carbon fibre (extracellular)
Ground or Reference
Recording Electrodes
http://www.psych.umn.edu/courses/fall05/burkhar
dtd/psy3031/images/microelectrode.jpg
Stimulating Electrodes
The not so simple setup
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)
Amplifier
The Amplifier amplifies and filters the signal.
Amplifier output goes to:
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Oscilloscope
A to D Converter
Oscilloscope
X-axis: Time
Y-axis: Voltage
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.
A to D conversion
Sampling Rate
Temporal Resolution
Digitization Range
Voltage Resolution
Ato D Sampling Rate & Temporal
Resolution
A to D Digital Range & Voltage
Resolution
4096 points
4 settings:
•-10V to +10V
•-5V to +5V
•-2.5V to +2.5V
•-1.25V to +1.25V
Resolution: 4.88mV
Resolution: 2.44mV
Resolution:1.22mV
Resolution: 0.61mV
20V
Maximize use of the range, but avoid clipping.
20V
Here the signals
from the rat are
seen in the
oscilloscope (top)
and on the
computer monitor
after being
digitized by the
AtoD Converter.
Add Electrical Stimulation
Many experiments examine connectivity
by looking at response evoked by
electrical stimulation to input.
Electrical Stimulation
Monopolar
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Anodal
Cathodal (electrons flow cathode  anode)
Bipolar
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Twisted wire
Concentric
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.
Heater
Under anaethesia animal will not regulate
temperature very well.
A heater can be added to maintain the
animals temperature at a constant level
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.
The Circuit
The Preparation
•Recording Electrode in Granule Cell
Layer of Dentate Gyrus
•Stimulating Electrode in Perforant
Path
•Cannula in Locus Coeruleus
The Evoked Response