Apple Motion 1.0.1 Manual do Utilizador descarregar pdf (Página 10)

D. MonitoringDecisionStatisticHistogramofSelectedChannel(Histogram

Tab)

The histogram of decisions statistics can be viewed in the panel under the Histogram tab. An

example is shown in Fig. 8. The blue vertical line superimposed on the histogram is the current

decision threshold. After 24 hours a clear bimodal distribution should appear as a result of

mapping sleep signal dynamics into positive values and wake signal dynamics into negative

values. If the histogram is not bimodal, it could be the result of noise or weak signals, for which

there are a number of causes:

 an electrically or mechanically noisy environment

 poor mouse contact with the piezoelectric sensor on the floor of the cage (sometimes

cause by too much bedding)

 faulty amplifier or sensor

 unusual mouse behavior not observed in the training phase of the classifier (i.e. mouse is

ill, dead, escaped, or has a very unusual respiratory pattern during sleep)

The bimodal pattern in the histogram below is exploited by adaptive thresholding, used in later

analysis programs, which seeks a minimum point between the clusters (modes) of decision

statistics. Real-time analysis is limited in that it uses the same threshold over all channels and

can vary by as much as 8% from the later analysis using an adaptive threshold. The primary

purpose of real-time monitoring in the acquisition program is to alert those monitoring the

experiment. If problems arise, they can be verified (by direct observation of the mouse) or

corrected during the experiment. More accurate sleep and wake parameters are generated with

the sleepstats() program in the MouseRecDataTools toolbox.

(a) (b)

Figure 8. Histogram of sleep-wake statistics. (a) Several days with mouse in typical sleep and wake

cycles. (b) Empty channel, noise-only.

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Apple Motion 1.0.1 Manual do Utilizador Página 10