Fig. 2.

Stimulation-evoked astrocyte Ca²⁺ signals can be split into high- and low-frequency components. (A) Representative example of Ca²⁺ activity recorded in an astrocytic soma; see red arrow in Fig. 1A, in percentage of baseline Ca²⁺ activity (ΔF/F₀). The yellow area marks whisker-pad stimulation at 2 Hz for a period of 15 s. (B) The astrocyte Ca²⁺ signal (A) separated by wavelet transformation to a high-frequency (Upper) and a low-frequency component (Lower). The red triangle indicates the start of the slow Ca²⁺ response, as defined by the max slope before the main peak. (C) The high-frequency response interpolated as a single fast Ca²⁺ signal by superimposing data from the 15-s train of stimulation; see Movie S2. Red dots represent data points collected at different times after repeated stimuli; the black line represents the interpolated signal. The gray line marks the time of the single stimulation. (D) The fast Ca²⁺ signal fitted so that the decay time of the signal (tau) can be estimated. (E) Latency of astrocyte cell body response times for the evoked fast and induced slow components expressed as a percentage of all astrocytes. The histogram shows great variation in latency time to onset of slow responses but also that a subset of astrocytes responded within the first 5 s of stimulation (154 astrocytes, 33 mice, 2 Hz stimulation frequency).