Quantitative Reevaluation of the Effects of Short- and Long-Term Removal of Descending Modulatory Inputs on the Pyloric Rhythm of the Crab, Cancer borealis

Long-term, continuous extracellular recordings of preparations of the STNS reveal stable behavior. Example 15 s lvn traces from two preparations, one in which with the stn left intact throughout the experiment (blue traces, left), and one in which the stn was transected shortly after the baseline recording (red traces, right).

Example long-term pyloric cycle frequency plots of intact (A−D) and decentralized (E−L) preparations of the STNS. Data are plotted after binning frequencies into 0.1 h bins. Intact preparations (blue) tend to maintain stable pyloric rhythms with frequencies in the normal range of controls. Decentralized preparations (red) display more varied and variable behavior. Decentralization was accomplished approximately 1 h following the beginning of these recordings.

Long-term population effects of decentralization on the pyloric rhythm. A, Population data for intact (n = 9) and decentralized (n = 19) preparations is shown for the first 6 d in culture. Data are plotted as box plots (see Materials and Methods) for each hour; data from intact preparations are shown in blue while decentralized preparations are shown in red. B−E, Cycle frequency correlations within preparations across time (dc, decentralized). Black diagonal line represents unity. Insets report R and p values of Pearson correlations. B, Following decentralization, all preparations exhibit a lower pyloric cycle frequency. C, All examined preparations also exhibit a lower frequency on the second day following decentralization (average frequency, 24−48 h). D, E, On subsequent days, preparations are more correlated, and show an equal tendency to increase or decrease frequency. F−K, Measures of frequency (F), across-preparation variability (coefficient of variation (C.V.), G), within-preparation variability (H), and pyloric phase relationships (I−K) are plotted for intact (blue) and decentralized (red) preparations. Box plots are created from population data consisting of the average value for each preparation in 24 h bins following decentralization.

Analysis of bouting. A, Example lvn recording featuring one detected bout, visible here in the noticeable increase in pyloric cycle frequency starting mid-trace. B, Frequency plot corresponding to the data in A. Arrow designates the point at which the bout was detected. C, Box plots show population data of the number of detected bouts by day for intact (blue) and decentralized (red) preparations.

Analysis of previously used measures of recovery. A. Two previously described definitions of recovery (time to first bout, and 5 h strong and steady rhythm) fail to correlate. B−F, Box plots show population data of intact (blue), 30 min decentralized (dc; red), and the fastest 5 h post-decentralization period of data from each decentralized preparation within the first 120 h. n.s., not significant; ***p < 0.001.