Figure 5

The 24 h mean rhythm of CSF [Na⁺] for all six participants, plotted as a shift from the mean as described in the Methods. Data were fitted with a 4^th degree polynomial curve to identify the peaks and troughs: A: 09.50 h, B: 18.10 h, C: 03.20 h, and D: 08.00 h. The 12-hour rhythm is most clear.