RT Journal Article
SR Electronic
T1 Evidence for time division multiplexing of multiple simultaneous items in a sensory coding bottleneck
JF bioRxiv
FD Cold Spring Harbor Laboratory
SP 107185
DO 10.1101/107185
A1 V. C. Caruso
A1 J. T. Mohl
A1 C. Glynn
A1 J. Lee
A1 S. Willett
A1 A. Zaman
A1 R. Estrada
A1 S. Tokdar
A1 J. M. Groh
YR 2017
UL http://biorxiv.org/content/early/2017/04/06/107185.abstract
AB How the brain preserves information about multiple simultaneous items is poorly understood. Here we provide evidence that the brain may accomplish this using time division multiplexing, or interleaving of different signals across time, to represent multiple items in a single neural channel. We evaluated single unit activity in an auditory coding “bottleneck”, the inferior colliculus, while monkeys reported the location(s) of one or two simultaneous sounds. Using novel statistical methods to evaluate spiking activity on a variety of time scales, we found that on dual-sound trials, neurons sometimes alternated between firing rates similar to those observed for each single sound. These fluctuations could occur either across or within trials and appeared coordinated across pairs of simultaneously recorded neurons. Fluctuations could be predicted by the state of local field potentials prior to sound onset, and, in one monkey, predicted which sound the monkey would ultimately saccade to first. Alternation between activity patterns corresponding to each of multiple items may be a general strategy employed by the brain to enhance its processing capacity, suggesting a potential connection between such disparate phenomena as variable neural firing, neural oscillations, and limits in attentional or memory capacity.SIGNIFICANCE STATEMENT In natural scenes, many things happen at once. Given that the neural populations activated by each stimulus overlap considerably, how does the brain preserve information about each item? We investigated whether the brain solves this problem using time division multiplexing,a telecommunications strategy for combining signals in a single channel. When two sounds were presented, we observed fluctuations in activity in the inferior colliculus at a variety of time scales. These fluctuations were not random but suggested that neurons switch back and forth between encoding different items. Such switching behavior provides a novel account for variability in neural firing, and suggests an explanation for limits in perception,attention, and working memory.