onu FY2018 Annual Report 4

Sub- and suprathreshold dendritic signaling in awake mice. (a) Dendritic voltage spatio-temporal maps show epochs of low and high frequency subthreshold ‘hotspot’ events in Purkinje neuron dendrites (scan position shown in Fig. 3j). White arrow heads indicate single hotspot events. (b) The corresponding calcium spatio-temporal map does not show any correlated calcium transients except following suprathreshold complex spikes and dendritic spikes indicated in (a) by filled and open triangles, respectively. (c) By thresholding and additional spatio-temporal selection criteria, a spatio-temporal hotspot map can be generated. (d) Hotspot activity correlates with the simple spike (SS) activity at the soma. (e) Spatially averaged dendritic voltage (red) and calcium (green) recorded at 2kHz, reveal rapid (1-2 ms) and variable suprathreshold dendritic spikelets during complex spikes (filled triangle). Extracellular somatic recordings (black) were used to identify the somatic output signals; simple spikes (SS: black binary trace) and complex spikes (CS: red binary trace). Non-climbing fiber evoked suprathreshold dendritic calcium spikes (open triangles) were detected in the awake mouse which enhance local calcium influx and showed no coincident sodium influx (simple spike) at the soma. (Roome & Kuhn 2018)