Duration of Purkinje cell complex spikes increases with their firing frequency.
Climbing fiber (CF) triggered complex spikes (CS) are massive depolarization bursts in the cerebellar Purkinje cell (PC), showing several high frequency spikelet components (±600 Hz). Since its early observations, the CS is known to vary in shape. In this study we describe CS waveforms, extracellularly recorded in awake primates (Macaca mulatta) performing saccades. Every PC analyzed showed a range of CS shapes with profoundly different duration and number of spikelets. The initial part of the CS was rather constant but the later part differed greatly, with a pronounced jitter of the last spikelets causing a large variation in total CS duration. Waveforms did not effect the following pause duration in the simple spike (SS) train, nor were SS firing rates predictive of the waveform shapes or vice versa. The waveforms did not differ between experimental conditions nor was there a preferred sequential order of CS shapes throughout the recordings. Instead, part of their variability, the timing jitter of the CS's last spikelets, strongly correlated with interval length to the preceding CS: shorter CS intervals resulted in later appearance of the last spikelets in the CS burst, and vice versa. A similar phenomenon was observed in rat PCs recorded in vitro upon repeated extracellular stimulation of CFs at different frequencies in slice experiments. All together these results strongly suggest that the variability in the timing of the last spikelet is due to CS frequency dependent changes in PC excitability.
Theoretical Neurobiology and Neuroengineering Lab, Department of Biomedical Sciences, University of Antwerp Wilrijk, Belgium ; Department of Neuroscience, Erasmus MC Rotterdam, Netherlands.
Pascal
P
Warnaar
Theoretical Neurobiology and Neuroengineering Lab, Department of Biomedical Sciences, University of Antwerp Wilrijk, Belgium.
Joao
J
Couto
Department of Neuroscience, Erasmus MC Rotterdam, Netherlands ; Computational Neuroscience Unit, Okinawa Institute of Science and Technology, Onna-Son Okinawa, Japan.
Mario
M
Negrello
Department of Cognitive Neurology, Hertie Institute for Clinical Brain Research, University of Tübingen Tübingen, Germany.
Marc
M
Junker
Department of Cognitive Neurology, Hertie Institute for Clinical Brain Research, University of Tübingen Tübingen, Germany.
Aleksandra
A
Smilgin
Physiology of Active Vision, Werner Reichardt Centre for Integrative Neuroscience, University of Tübingen Tübingen, Germany.
Alla
A
Ignashchenkova
Theoretical Neurobiology and Neuroengineering Lab, Department of Biomedical Sciences, University of Antwerp Wilrijk, Belgium ; Department of Computer Science, University of Sheffield Sheffield, UK ; Brain Mind Institute, Swiss Federal Institute of Technology Lausanne Lausanne, Switzerland.
Michele
M
Giugliano
Department of Cognitive Neurology, Hertie Institute for Clinical Brain Research, University of Tübingen Tübingen, Germany.
Peter
P
Thier
Theoretical Neurobiology and Neuroengineering Lab, Department of Biomedical Sciences, University of Antwerp Wilrijk, Belgium ; Computational Neuroscience Unit, Okinawa Institute of Science and Technology, Onna-Son Okinawa, Japan.
Erik
E
De Schutter
Purkinje neuron; complex spike; monkey; saccades; waveform