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Fig. 1 | Fluids and Barriers of the CNS

Fig. 1

From: Variations in the cerebrospinal fluid dynamics of the American alligator (Alligator mississippiensis)

Fig. 1

a 60 s data record of Alligator mississippiensis in apnea. The raw CSF and EKG tracings were recorded simultaneously, and show a temporal coupling between the cardiac cycle and CSF pulsations. The filtered (lower) CSF trace shows the relative stability of the pulsation amplitude (AMP), temporal pattern, and general shape. b Power spectrum analysis of the CSF trace shown in (a) reveals a fundamental spike (c) at the frequency of the heart rate (16 bpm), as well as two harmonics (C*); as expected during apnea, no ventilatory component was found in the power spectral analysis. c Composite Power Spectral analyses of CSF pressure waves recorded from two different alligators, both in a horizontal posture. For each alligator three (raw, unfiltered) CSF pressure traces were analyzed; at a resting level of 10 breaths per minute (red waves); during apnea or 0 breaths per minute (blue waves); and at a ventilatory rate of 3 × resting or approx. 30 breaths per minute (green wave). Both the spectral frequency and the overlap of the frequency spikes permit identification of the ventilatory (V) and cardiac (C) fundamental contributions, as well any harmonics (*)

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