title: [Adaptation of differential sensitivity of auditory neurons to amplitude modulation after a sharp change of signal intensity].
abstract: In the common frog Rana temporaria, the neuronal firing evoked by long amplitude-modulated tones was recorded in auditory regions of medulla (dorsal nucleus) and of midbrain (torus semicircularis). We recorded firing rate, synchronization with modulation, and phase of response every 2 or 4 s. After adaptation of neuronal response to the acting stimulus (30-60 s after its onset) the mean level of signal sharply changed (by 20-40 dB), whereas frequency and modulation depth remained constant. Changes of firing density and of degree of its synchronization with modulation period were recorded, as well as the phase of maximum of reaction at the period of modulation. At low modulation depths at the initial site, we observed an adaptation decrease of impulsation density accompanied by an improvement of the response synchronization. A sharp increase (by 20-40 dB) in the mean level led to a rise in the implication density, which could be accompanied either by a continued increase of synchronicity (the more typical effect for the dorsal nucleus) or by a sharp fall of synchronicity with its subsequent slow recovery (the more typical effect for the torus semicircularis). The character of changes in reaction after replacement of intensity could also depend on the signal parameters (the initial level, the jump value, the frequency and depth of modulation). The connection of the revealed physiological effects with psychophysics of perception of small amplitude modulations is discussed.
authors: N G
authors: NG
authors: Bibikov
mesh_terms: D000161:Acoustic Stimulation; D000222:Adaptation, Physiological; D000818:Animals; D001307:Auditory Perception / Q000502:physiology*; D003056:Cochlear Nerve / Q000166:cytology / Q000378:metabolism; D005260:Female; D006801:Humans; D008297:Male; D008526:Medulla Oblongata / Q000502:physiology; D008636:Mesencephalon / Q000166:cytology / Q000502:physiology; D009474:Neurons / Q000166:cytology / Q000502:physiology; D011896:Rana temporaria / Q000502:physiology*