Figure 6. Auditory processing in REM sleep resembles wakefulness rather than NREM sleep.

A) Representative spectro-temporal receptive field (STRF) of an auditory cortex unit showing preserved tuning during the Vigilant and REM sleep conditions (left and right, respectively). B) Modulation of frequency tuning width (REM sleep vs. Vigilant conditions) for all units (n=122) and sessions (n=11). C) Signal correlations of frequency tuning across the entire dataset between different units in the same session (left bar), between Vigilant and REM-sleep conditions of the same individual units (middle bar) and between 1st and 2nd halves of trials in the same condition for the same individual units (right bar). Note that signal correlations are nearly as high across Vigilant and REM-sleep conditions as they are within the same condition. D) An example unit raster and peristimulus time histogram (PSTH) for 2 and 40 clicks/s click trains (left and right, respectively). Green shading represents the post-onset [30,80]ms period and yellow shading represents the [130,530]ms period with sustained locking to the 40 click/s train. Note that in both these intervals, neuronal activity was similar in Vigilant and REM sleep, unlike the attenuation observed in NREM sleep. E) Modulation of spontaneous FR, onset response FR, population synchrony, 40-Hz locking and post onset FR during REM sleep relative to the Vigilant condition for all units (n=327/198) and sessions (n=17/10). 2 click/s train were only presented in 11 sessions (‘auditory paradigm A’). Most auditory processing features were comparable or enhanced in REM sleep compared with the Vigilant condition. Dashed vertical line separates features minimally/not significantly affected by NREM sleep/Tired as in previous figures, for reference. F) same as E but comparing REM sleep to NREM sleep. G) Normalized locked responses in a representative unit (y-axis) as a function of click rate (x-axis) separately for Vigilant (cyan), NREM sleep (green), and REM sleep (pink). Circles represent the observed locked response to each click rate in each condition. Thick traces represent the best sigmoid fit. Cross represents the estimated ‘adapted click-rate’, i.e. the click rate for which the normalized response would be 25% of maximum. H) Left: scatter plot of the ‘adapted click-rate’ for all units (n=138) and sessions (n=10 in 6 animals), comparing REM sleep (y-axis) with Vigilant conditions (x-axis); Right: same when comparing REM sleep (y-axis) with recovery NREM sleep (x-axis). Yellow cross represents mean±SEM across all units. For Panels B, C, E, F and H: small gray markers represent individual units. Large dark gray markers represent mean of all units in an individual session. Each marker shape represents sessions from an individual animal. Markers with/without black edges represent ‘auditory paradigm A’ and ‘auditory paradigm B’ sessions, respectively. Red dots point to the representative unit presented in panels A and D.