Recovery from short‐term adaptation in auditory nerve fibers of the leopard frog

1979 ◽  
Vol 65 (S1) ◽  
pp. S82-S82
Author(s):  
A. L. Megela ◽  
R. R. Capranica
Keyword(s):  
Auditory Nerve ◽  
Nerve Fibers ◽  
Leopard Frog ◽  
Short Term ◽  
Short Term Adaptation ◽  
Auditory Nerve Fibers

Response Adaptation of Medial Olivocochlear Neurons Is Minimal

2001 ◽  
Vol 86 (5) ◽  
pp. 2381-2392 ◽  
Author(s):  
M. C. Brown
Keyword(s):  
Firing Rate ◽  
Auditory Nerve ◽  
General Characteristic ◽  
Nerve Fibers ◽  
Short Term ◽  
Percentage Decrease ◽  
Short Term Adaptation ◽  
Auditory Nerve Fibers ◽  
Medial Olivocochlear

Response adaptation is a general characteristic of neurons. A number of studies have investigated the adaptation characteristics of auditory-nerve fibers, which send information to the brain about sound stimuli. However, there have been no previous adaptation studies of olivocochlear neurons, which provide efferent fibers to hair cells and auditory nerve dendrites in the auditory periphery. To study adaptation in efferent fibers, responses of single olivocochlear neurons were recorded to characteristic-frequency tones and noise, using anesthetized guinea pigs. To measure short-term adaptation, stimuli of 500 ms duration were presented, and the responses were displayed as peristimulus time histograms. These histograms showed regular peaks, indicating a “chopping” pattern of response. The rate during each chopping period as well as the general trend of the histogram could be well fit by an equation that expresses the firing rate as a sum of 1) a short-term adaptive rate that decays exponentially with time and 2) a constant steady-state rate. For the adaptation in medial olivocochlear (MOC) neurons, the average exponential time constant was 47 ms, which is roughly similar to that for short-term adaptation in auditory-nerve fibers. The amount of adaptation (expressed as a percentage decrease of onset firing rate), however, was substantially less in MOC neurons (average 31%) than in auditory-nerve fibers (average 63%). To test for adaptation over longer periods, we used noise and tones of 10 s duration. After the short-term adaptation, the responses of MOC neurons were almost completely sustained (average long-term adaptation 3%). However, in the same preparations, significant long-term adaptation was present in auditory-nerve fibers. These results indicate that the MOC response adaptation is minimal compared with that of auditory-nerve fibers. Such sustained responses may enable the MOC system to produce sustained effects in the periphery, supporting a role for this efferent system during ongoing stimuli of long duration.

Classification of the temporal discharge patterns of single auditory neurons in the dorsal medullary nucleus of the northern leopard frog

1990 ◽  
Vol 64 (5) ◽  
pp. 1460-1473 ◽  
Author(s):  
J. C. Hall ◽  
A. S. Feng
Keyword(s):  
Auditory Nerve ◽  
Functional Organization ◽  
Neuronal Response ◽  
Nerve Fibers ◽  
Leopard Frog ◽  
Central Auditory Processing ◽  
Acoustic Information ◽  
Auditory Nerve Fibers ◽  
Dorsal Medullary Nucleus ◽  
Discharge Patterns

1. The dorsal medullary nucleus (DMN) of frogs is the presumed homolog of the mammalian cochlear nucleus (CN). Like the CN, the DMN is the sole target of centrally projecting primary auditory-nerve fibers and the first central auditory-processing center. To study the transformation of acoustic information in the DMN, we have utilized relatively simple stimuli--tone bursts--to detail the temporal discharge patterns of DMN neurons that can be compared with those shown by auditory-nerve fibers. 2. Based on the shape of poststimulus time (PSTH) and interspike interval (ISIH) histograms, we observed six distinctive discharge patterns to tone bursts presented at the best excitatory frequency (BEF), 10 dB above threshold. Four of these (primary-like type 1-4) resembled discharge patterns seen at the level of the auditory nerve, whereas two (phasic and phasic burst) were only observed in the DMN. 3. At stimulus levels of 20-30 dB above BEF threshold several phasic neurons became tonic responders, whereas several primary-like type-2 cells gave "pauser" discharges. The response patterns of the remaining cells were intensity independent. 4. We further showed that many of the single-unit discharge patterns were related to other neuronal response properties; specifically, spontaneous firing rate, intensity-rate functions, threshold, latency, BEF, and sharpness of tuning (Q10). 5. The implications of our findings are discussed with respect to 1) the transformation of acoustic information as it is passed from the auditory nerve to the DMN, and 2) the functional organization of the DMN.

scholarly journals Short-Term Synaptic Depression and Recovery at the Mature Mammalian Endbulb of Held Synapse in Mice

2008 ◽  
Vol 100 (3) ◽  
pp. 1255-1264 ◽  
Author(s):  
Yong Wang ◽  
Paul B. Manis
Keyword(s):  
Synaptic Transmission ◽  
Auditory Nerve ◽  
Synaptic Depression ◽  
Nerve Fibers ◽  
Short Term ◽  
Endbulb Of Held ◽  
Intracellular Ca ◽  
Auditory Nerve Fibers ◽  
Spontaneous Firing Rate

The endbulb of Held synapses between the auditory nerve fibers (ANF) and cochlear nucleus bushy neurons convey fine temporal information embedded in the incoming acoustic signal. The dynamics of synaptic depression and recovery is a key in regulating synaptic transmission at the endbulb synapse. We studied short-term synaptic depression and recovery in mature (P22-38) CBA mice with stimulation rates that were comparable to sound-driven activities recorded in vivo. Synaptic depression in mature mice is less severe (∼40% at 100 Hz) than reported for immature animals and the depression is predominately due to depletion of releasable vesicles. Recovery from depression depends on the rate of activity and accumulation of intracellular Ca2+ at the presynaptic terminal. With a regular stimulus train at 100 Hz in 2 mM external [Ca2+], the recovery from depletion was slow (τslow, ∼2 s). In contrast, a fast (τfast, ∼25 ms), Ca2+-dependent recovery followed by a slower recovery (τslow, ∼2 s) was seen when stimulus rates or external [Ca2+] increased. In normal [Ca2+], recovery from a 100-Hz Poisson-like train is rapid, suggesting that Poisson-like trains produce a higher internal [Ca2+] than regular trains. Moreover, the fast recovery was slowed by approximately twofold in the presence of calmidazolium, a Ca2+/calmodulin inhibitor. Our results suggest that endbulb synapses from high spontaneous firing rate auditory nerve fibers normally operate in a depressed state. The accelerated synaptic recovery during high rates of activity is likely to ensure that reliable synaptic transmission can be achieved at the endbulb synapse.

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