Neural readout of a latency code in the active electrosensory system

The latency of spikes relative to a stimulus conveys sensory information across modalities. However, in most cases, it remains unclear whether and how such latency codes are utilized by postsynaptic neurons. In the active electrosensory system of mormyrid fish, a latency code for stimulus amplitude in electroreceptor afferent nerve fibers (EAs) is hypothesized to be read out by a central reference provided by motor corollary discharge (CD). Here, we demonstrate that CD enhances sensory responses in postsynaptic granular cells of the electrosensory lobe but is not required for reading out EA input. Instead, diverse latency and spike count tuning across the EA population give rise to graded information about stimulus amplitude that can be read out by standard integration of converging excitatory synaptic inputs. Inhibitory control over the temporal window of integration renders two granular cell subclasses differentially sensitive to information derived from relative spike latency versus spike count. [Display omitted] •Spike latency is transformed into graded changes in postsynaptic response amplitude•Motor corollary discharge signals are not required for decoding spike latency•Diverse receptor tuning and rapid inhibition play key roles in decoding spike latency In many systems, information is conveyed by the precise latency of spikes relative to a sensory stimulus. Perks and Satwell use intracellular recordings and modeling to reveal how such a latency code is read out by neurons in the active electrosensory system of fish.