07 under urethane The mean duration of the spindles in both cond

07 under urethane. The mean duration of the spindles in both conditions agreed with previous reports (Azumi and find more Shirakawa, 1982, Gaillard and Blois, 1981 and Silverstein and Levy, 1976) (10.7 ± 6.0 cycles/spindle in natural sleep, 9.5 ± 5.3 cycles/spindle under urethane). The number of short spindles (five to six cycles) was somewhat higher in natural sleep than under urethane

(Figure 1C). The mean frequency of spindles was also similar in the two conditions (natural sleep 12.65 ± 1.89 Hz, urethane 12.91 ± 1.63 Hz). Both in natural sleep and under anesthesia, spindles showed an initially accelerating pattern, irrespective of their length (Figure 1D), as shown by Gardner et al. (2013). Spindles under natural sleep showed a deceleration toward the end, which was not present under urethane anesthesia. Thus, we conclude that under our recording conditions sleep spindles can be reliable detected in the thalamus with comparable parameters (duration, frequency) to earlier results. The basic features of spindles under urethane and in freely sleeping conditions were largely similar, with the most prominent difference being that under anesthesia spindles were more spatially restricted. After spike sorting (see Experimental Procedures Rapamycin ic50 and Figure S1B), a single octrode yielded on average 12.9 well-separated single units (554 units all together from all animals). The action potential widths of single units clustered from

VB showed a marked bimodality (Figures 2A and 2B), with the narrow-spike mode centered at 100 μs and a wide spike mode centered at 275 μs. The values of narrow spikes were actually briefer than the extracellular waveforms of

cortical fast-spiking interneurons (Barthó et al., 2004). Units corresponding to both modes were usually recorded on a single shank. Wide-spike units (>150 μs) displayed burst firing typical of TC cells (Domich et al., 1986) (3.19 ± 1.52 spikes/burst, 149.0 ± 177.7 Hz for natural sleep, n = 102 units; 2.82 ± 1.11 spikes/burst, 287.0 ± 196 Hz under urethane, n = 320 units). Narrow-spike units (<150 μs) unless produced longer and slower bursts (5.17 ± 2.63 spikes/burst, 48.8 ± 81.5 Hz for natural sleep, n = 17 units, 3.57 ± 1.81 spikes/burst, 90.8 ± 119 Hz under urethane, n = 115 units) and were usually modulated in the spindle frequency range (Figure 2C). Cross-correlation analysis revealed that most narrow spike units fired on average 15–20 ms after wide spike units (Figure S1B4) both in natural sleep and under urethane anesthesia. These data suggested that beside TC cells (wide spikes) our electrodes sampled another neuronal population (narrow spikes). However, the origin of narrow spikes remained unclear because the rodent VB thalamus contains only one type of neuron, the TC cell (Barbaresi et al., 1986). The narrow spikes picked up by our electrodes in VB resembled axonal spikes that have been described in several neural systems (Goldberg and Fee, 2012, Khaliq and Raman, 2005 and Meeks et al., 2005).

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