Event Abstract

Computational models of millisecond level neuronal timing mechanisms

Discrimination of stimulus duration on the order of milliseconds has been observed in behavioural and neurophysiological studies across a variety of species and taxa. Mammalian studies have found neurons in the auditory midbrain (inferior colliculus) selective for signal duration that are referred to as duration tuned neurons (DTNs). This study formulates three computational models that amalgamate conceptual models with physiological responses in the bat auditory midbrain to evaluate the biological plausibility of the proposed neural mechanisms. The computational models employ the adaptive exponential integrate-and-fire neuron model [1] and Poisson spiking processes to reproduce several responses observed in vivo including DTN response classes, spike counts, first-spike latencies, level tolerance, best duration tuning, and neuropharmacological effects of inhibitory neurotransmitter antagonists applied to DTNs in vivo.

Coincidence Detection Model
First proposed by [2], this model produces shortpass or bandpass DTNs via an onset-evoked excitatory post-synaptic potential (EPSP) and an offset-evoked EPSP that each evoke sub-threshold depolarization in the DTN. Delaying the arrival of the onset-evoked EPSP results in both EPSPs coinciding for stimulus durations within a specific duration window to evoke action potentials in the DTN. For example, if the onset-evoked EPSP is delayed for 6 ms from stimulus onset and the offset-evoked EPSP occurs 4 ms from stimulus offset, then both EPSPs will coincide after a 2 ms stimulus.

Anti-coincidence Model
Suggested by [3], this model produces shortpass DTNs. The anti-coincidence model has a delayed onset-evoked EPSP that produces supra-threshold depolarization in the DTN. An onset-evoked IPSP lasting the duration of the stimulus is also present. For short stimulus durations, the IPSP arriving at the DTN ends before the arrival of the delayed, onset-evoked EPSP (i.e. the two events do not coincide), thus allowing the DTN to produce action potentials. For longer durations, the IPSP and the EPSP overlap to suppress action potentials in the DTN.

Longpass Model
Suggested by [4], this model produces DTNs that respond only to stimuli that are longer than a specific duration. The model incorporates a supra-threshold EPSP at the DTN lasting for the duration of the stimulus and an adapting IPSP that suppresses activity in the DTN for only the first several milliseconds to prevent action potentials in the DTN for short duration stimuli. Our computational model also replicates the increased first-spike latency shift that occurs at higher stimulus amplitudes (i.e. a paradoxical latency shift) seen in vivo by hypothesizing that the IPSP input activity has a steeper rate-level function than the EPSP input activity.

Each model is supported by neurophysiological data and is specific to a particular class of DTNs. This study provides biological grounding to previously only conceptual models to further our understanding of millisecond level neuronal timing mechanisms.

References

1. Brette Gerstner (2005) J. Neurophysiology 94:3637-3642.

2. Narins Capranica (1980) Brain, Behavior and Evolution 17(1):48-66

3. Fuzessery Hall (1999) Hearing Research 137:137-154

4. Faure, et al. (2003) J. Neuroscience 23(7):3052-3065

Conference: Computational and systems neuroscience 2009, Salt Lake City, UT, United States, 26 Feb - 3 Mar, 2009.

Presentation Type: Poster Presentation

Topic: Poster Presentations

Citation: (2009). Computational models of millisecond level neuronal timing mechanisms. Front. Syst. Neurosci. Conference Abstract: Computational and systems neuroscience 2009. doi: 10.3389/conf.neuro.06.2009.03.244

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Received: 03 Feb 2009; Published Online: 03 Feb 2009.