Microsecond ITD precision arises from phase-delay matching, not absolute latency

Evidence

Both extracellular neurophonic recordings and intracellular NM axonal recordings in NL revealed maps of ITD, created by precisely regulated conduction delays from intrinsically noisy elements. The microsecond precision needed to construct these maps of ITD appears to be achieved through precisely regulated phase delays, rather than by regulation of absolute latency. — Dijk, Pim van, Physiology, Psychoacoustics and…, 2848

Intracellular recordings from NM axons were used to measure delay-line latencies in NL. Systematic shifts in conduction delay within NL accounted for the maps of ITD, but recorded latencies of individual inputs at nearby locations could vary by 2π or 4π. Therefore microsecond precision is achieved through sensitivity to phase delays, rather than absolute latencies. — Dijk, Pim van, Physiology, Psychoacoustics and…, 2839

A key feature of ITD sensitivity is how the observed microsecond delays may be created by neural elements that are both noisy and slow. There are two possibilities, illustrated by the example of a coincidence detector neuron that responds to a pure sine tone, presented to both ears at an ITD of 0 μs, or sound in front of the animal. One strategy requires equal conduction latencies from each ear to the coincidence detector, such that the inputs would arrive with equal latency and equal phase. The second strategy relies on relative delays and would simply require that inputs arrive at the same phase. Due to the periodicity of the sine wave, both scenarios would produce the same output. — Dijk, Pim van, Physiology, Psychoacoustics and…, 2842

Categorization

• QUESTION: This result seems counterintuitive: how do coincidence detectors distinguish phase-equivalent latencies (differing by full cycles) when a given frequency produces identical ongoing phase? Worth chasing the computational logic.
• DEFINE: Clarifies the two coding strategies — equal absolute latency vs. phase-matched (modulo 2π) delays — that distinguish how coincidence detectors achieve timing.
• corroborated: 6 independent passages support this claim — Dijk, Pim van, Physiology, Psychoacoustics and…, 2848; Dijk, Pim van, Physiology, Psychoacoustics and…, 2839; Dijk, Pim van, Physiology, Psychoacoustics and…, 2842
• XREF: connects to: ITD sensitivity depends on phase differences, not absolute conduction latencies — Dijk, Pim van, Physiology, Psychoacoustics and…, 2842; Coincidence detection needs microsecond-matched delays built via development and fine-tuned regulation; Click stimuli achieve neural timing precision of about twenty microseconds (+1 more)

Broader Connections

• ITD sensitivity depends on phase differences, not absolute conduction latencies #corroborates (0.95) — Dijk, Pim van, Physiology, Psychoacoustics and…, 2842
• Click stimuli achieve neural timing precision of about twenty microseconds #expands (0.75)
• Coincidence detection needs microsecond-matched delays built via development and fine-tuned regulation #expands (0.72)
• Auditory nerve damage degrades sound localization by corrupting ILD and ITD cues #complicates (0.72)