Biomedical Engineering Reference
In-Depth Information
FIgURE 7.11:
Two hundred fifty microseconds of extracellular recordings with two spikes.
samples in the noise floor. The samples used in the calculation were extracted by looking for periods
of data where no spikes appeared.
To provide a baseline for quantifying the noise attributed by the system, the inputs to the
probes were tied to the reference and the corresponding trace is given in Figure
7.13
. These results
suggest that the source of the dc offset is inherent in the system, which supports the need to care-
fully adjust the bias of the amplifiers. When these data are normalized, the RMS voltage of the
noise using the same process described earlier yields 0.66 µV, which is much lower when compared
to the 8.24 µV in the actual test.
FIgURE 7.12:
Average waveform spikes of two different neurons.
