Multiplexed Spike Coding and Adaptation in the Thalamus

• Published in: Cell reports (Cambridge) 2017-05, Vol.19 (6), p.1130-1140
• Main Authors: Mease, Rebecca A., Kuner, Thomas, Fairhall, Adrienne L., Groh, Alexander
• Format: Article
• Language: English
• Subjects: Action Potentials; adaptation; Adaptation, Physiological; Animals; bursting; Calcium - metabolism; Calcium Channels, T-Type - metabolism; excitability; Female; linear-nonlinear model; Male; Mice; multiplexing; neural coding; Neurons - metabolism; Neurons - physiology; Rats; Rats, Wistar; Sodium - metabolism; Synaptic Potentials; T-type calcium channel; thalamocortical system; Thalamus - cytology; Thalamus - physiology
• ISSN: 2211-1247; 2211-1247
• DOI: 10.1016/j.celrep.2017.04.050

High-frequency “burst” clusters of spikes are a generic output pattern of many neurons. While bursting is a ubiquitous computational feature of different nervous systems across animal species, the encoding of synaptic inputs by bursts is not well understood. We find that bursting neurons in the rodent thalamus employ “multiplexing” to differentially encode low- and high-frequency stimulus features associated with either T-type calcium “low-threshold” or fast sodium spiking events, respectively, and these events adapt differently. Thus, thalamic bursts encode disparate information in three channels: (1) burst size, (2) burst onset time, and (3) precise spike timing within bursts. Strikingly, this latter “intraburst” encoding channel shows millisecond-level feature selectivity and adapts across statistical contexts to maintain stable information encoded per spike. Consequently, calcium events both encode low-frequency stimuli and, in parallel, gate a transient window for high-frequency, adaptive stimulus encoding by sodium spike timing, allowing bursts to efficiently convey fine-scale temporal information. [Display omitted] •Thalamic neurons simultaneously encode high- and low-frequency information•Precise spike timing within bursts efficiently conveys stimulus details•Adaptation within bursts makes information transmission robust to contextual change Packets of high-frequency spikes termed “bursts” are a ubiquitous yet enigmatic feature of neural spike trains. Mease et al. investigate computational properties of bursts in the mammalian thalamus, finding that bursts can efficiently encode high- and low-frequency information in parallel. Thus, the cortex may receive more information than previously believed.