During short spindles animals, nRT activity was highest in the first cycle (3.5 spikes/cycle) then decreased monotonically, dropping ∼50% by the end of the spindle (1.55 spikes/cycle); by contrast, TC cell activity was lowest in the first cycle and increased steadily. For long spindles, nRT activity displayed a different, nonmonotonic pattern, first increasing from a moderate value (2.1 spikes/cycle) to reach a peak of 3.15 spikes/cycle by cycle 3 and then decreasing strongly Venetoclax in vivo to ∼30% of the peak value (0.83 spikes/cycle) by spindle termination. During long spindles, TC activity again displayed a slow recruitment, in most cases with a slight
decrease one to two cycles before the spindle ended. Examining similar plots for spindles of all lengths (Figure S6A) indicated that in all cases Sirolimus research buy nRT activity started to decrease several cycles before spindle termination, but this was not observed in case of TC cells in either natural sleep or urethane anesthesia. Based on these data, we conclude that nRT, but not TC activity starts to decay several cycles before the termination of all spindles. The analysis above indicated that nRT cells may display spindle duration specific activity.
To demonstrate this, we analyzed cycle-by-cycle TC and nRT activity for all spindle length. During spindles thalamic neurons fire exclusively in low-threshold Ca2+ bursts. Each neuron can produce one burst per spindle cycle but neither nRT nor TC cells fire at every cycle. As a consequence, changes in the number of spikes during consecutive cycles (as analyzed above) could reflect either a change in the number of spikes fired per burst, and/or a change in the probability the cell will fire a burst in the cycle (participation
probability). It should be noted that participation probability is equivalent to the percentage of cells participating in a given spindle cycle, which indicates the level of recruitment within the TC or nRT population. To examine the cycle-by-cycle alterations Oxymatrine in these measures, we calculated spike/burst and participation probability separately for all TC and nRT cells for all spindle length (five to 14 cycles) during natural sleep (Figure 6). For nRT cells, the number of spikes per burst started at a uniformly high level (approximately five) for all spindle lengths and showed a monotonic decrease to approximately three to four spikes per burst by the end of the spindle. TC cells, on the other hand did not display significant alteration in burst size during the spindles (Figure 6A). For participation probability, nRT cells displayed pronounced differences between short and long spindles (Figure 6B). The shortest spindles were characterized by high initial nRT participation probability (60%), which dropped throughout the spindle to a moderate level (46%–49%) by termination.