Emergence of band-pass filtering through adaptive spiking in the owl's cochlear nucleus.
In the visual, auditory, and electrosensory modalities, stimuli are defined by first- and second-order attributes. The fast time-pressure signal of a sound, a first-order attribute, is important, for instance, in sound localization and pitch perception, while its slow amplitude-modulated envelope, a second-order attribute, can be used for sound recognition. Ascending the auditory pathway from ear to midbrain, neurons increasingly show a preference for the envelope and are most sensitive to particular envelope modulation frequencies, a tuning considered important for encoding sound identity. The level at which this tuning property emerges along the pathway varies across species, and the mechanism of how this occurs is a matter of debate. In this paper, we target the transition between auditory nerve fibers and the cochlear nucleus angularis (NA). While the owl's auditory nerve fibers simultaneously encode the fast and slow attributes of a sound, one synapse further, NA neurons encode the envelope more efficiently than the auditory nerve. Using in vivo and in vitro electrophysiology and computational analysis, we show that a single-cell mechanism inducing spike threshold adaptation can explain the difference in neural filtering between the two areas. We show that spike threshold adaptation can explain the increased selectivity to modulation frequency, as input level increases in NA. These results demonstrate that a spike generation nonlinearity can modulate the tuning to second-order stimulus features, without invoking network or synaptic mechanisms.
Dominick Purpura Department of Neuroscience, Albert Einstein College of Medicine, Bronx, New York; bertrand.fontaine@med.kuleuven.be.
Bertrand
B
Fontaine
Department of Biology, Neuroscience and Cognitive Science Program, University of Maryland, College Park, Maryland; and.
Katrina M
KM
MacLeod
Department of Biology, Neuroscience and Cognitive Science Program, University of Maryland, College Park, Maryland; and.
Susan T
ST
Lubejko
Dominick Purpura Department of Neuroscience, Albert Einstein College of Medicine, Bronx, New York;
Louisa J
LJ
Steinberg
Cluster of Excellence "Hearing4all" and Research Center Neurosensory Science and Department of Neuroscience School of Medicine and Health Science, Carl von Ossietzky University, Oldenburg, Germany.
Christine
C
Köppl
Dominick Purpura Department of Neuroscience, Albert Einstein College of Medicine, Bronx, New York;
Jose L
JL
Peña
D000200:Action Potentials; D000222:Adaptation, Physiological; D000818:Animals; D001307:Auditory Perception; D017626:Cochlear Nucleus / Q000166:cytology / Q000502:physiology*; D009474:Neurons / Q000502:physiology; D013016:Sound; D020305:Strigiformes
band-pass filtering; cochlear nucleus; envelope encoding; threshold adaptation