Effect of time constant of acoustic stimulus on unit activity of inferior colliculus

1970 ◽  
Vol 4 (4) ◽  
pp. 63-73 ◽  
Author(s):  
I. A. Vartanyan ◽  
V. I. Snetkov
Keyword(s):  
Inferior Colliculus ◽  
Time Constant ◽  
Unit Activity ◽  
Acoustic Stimulus

Temporal coding of envelopes and their interaural delays in the inferior colliculus of the unanesthetized rabbit

1989 ◽  
Vol 61 (2) ◽  
pp. 257-268 ◽  
Author(s):  
R. Batra ◽  
S. Kuwada ◽  
T. R. Stanford
Keyword(s):  
Inferior Colliculus ◽  
Phase Locking ◽  
Acoustic Stimulus ◽  
Low Frequency ◽  
Auditory Pathway ◽  
Temporal Coding ◽  
Time Of Arrival ◽  
Unanesthetized Rabbit ◽  
The Difference ◽  
Ipsilateral Stimulation

1. The difference in the time of arrival of a sound at the two ears can be used to locate its source along the azimuth. Traditionally, it has been thought that only the on-going interaural temporal disparities (ITDs) produced by sounds of lower frequency (approximately less than 2 kHz) could be used for this purpose. However, ongoing ITDs of low frequency are also produced by envelopes of amplitude-modulated (AM) tones. These ITDs can be detected and used to lateralize complex high-frequency sounds (1, 8, 12, 15, 22, 24, 26). Auditory neurons synchronize to the modulation envelope, but do so at progressively lower modulation frequencies at higher levels of the auditory pathway. Some neurons of the cochlear nucleus synchronize best to frequencies as high as 700 Hz, but those of the inferior colliculus (IC) exhibit their best synchrony below 200 Hz. Even though synchrony to higher modulation frequencies is reduced at higher levels of the auditory pathway, is information about ITDs retained? 2. We answered this question by extracellularly recording the responses of neurons in the IC of the unanesthetized rabbit. We used an unanesthetized preparation because anesthesia alters the responses of neurons in the IC to both monaurally presented tones and ITDs. The unanesthetized rabbit is ideal for auditory research. Recordings can be maintained for long periods, and the acoustic stimulus to each ear can be independently controlled. 3. We studied the responses of 89 units to sinusoidally AM tones presented to the contralateral ear. For each unit, we recorded the response at several modulation frequencies. The degree of phase locking to the envelope at each frequency was measured using the synchronization coefficient. Two measures were used to assess the range of modulation frequencies over which phase locking occurred. The "best AM frequency" was the frequency at which we observed the greatest phase locking. The "highest AM frequency" was the highest frequency at which significant phase locking (0.001 level) was observed. We could not assess synchrony to ipsilateral AM tones directly, because most units did not respond to ipsilateral stimulation. 4. We studied the sensitivity of 63 units to ITDs produced by the envelopes of AM tones. Sensitivity to ITDs was tested by presenting AM tones to the two ears that had the same carrier frequency, but modulation frequencies that differed by 1 Hz. Units that were sensitive to ITDs responded to this stimulus by varying their response rate cyclically at the difference frequency, i.e., 1 Hz.(ABSTRACT TRUNCATED AT 400 WORDS)

Spike-Frequency Adaptation in the Inferior Colliculus

2004 ◽  
Vol 91 (2) ◽  
pp. 632-645 ◽  
Author(s):  
Neil J. Ingham ◽  
David McAlpine
Keyword(s):  
Inferior Colliculus ◽  
Time Constant ◽  
Recovery Period ◽  
Variable Interval ◽  
Stimulus Onset ◽  
Spike Frequency ◽  
Spike Frequency Adaptation ◽  
Time Constants ◽  
Adaptation Time ◽  
Frequency Adaptation

We investigated spike-frequency adaptation of neurons sensitive to interaural phase disparities (IPDs) in the inferior colliculus (IC) of urethane-anesthetized guinea pigs using a stimulus paradigm designed to exclude the influence of adaptation below the level of binaural integration. The IPD-step stimulus consists of a binaural 3,000-ms tone, in which the first 1,000 ms is held at a neuron's least favorable (“worst”) IPD, adapting out monaural components, before being stepped rapidly to a neuron's most favorable (“best”) IPD for 300 ms. After some variable interval (1–1,000 ms), IPD is again stepped to the best IPD for 300 ms, before being returned to a neuron's worst IPD for the remainder of the stimulus. Exponential decay functions fitted to the response to best-IPD steps revealed an average adaptation time constant of 52.9 ± 26.4 ms. Recovery from adaptation to best IPD steps showed an average time constant of 225.5 ± 210.2 ms. Recovery time constants were not correlated with adaptation time constants. During the recovery period, adaptation to a 2nd best-IPD step followed similar kinetics to adaptation during the 1st best-IPD step. The mean adaptation time constant at stimulus onset (at worst IPD) was 34.8 ± 19.7 ms, similar to the 38.4 ± 22.1 ms recorded to contralateral stimulation alone. Individual time constants after stimulus onset were correlated with each other but not with time constants during the best-IPD step. We conclude that such binaurally derived measures of adaptation reflect processes that occur above the level of exclusively monaural pathways, and subsequent to the site of primary binaural interaction.

Single Unit Activity in the Inferior Colliculus of the Rat Elicited by Electrical Stimulation of the Cochlea

1997 ◽  
Vol 36 (4) ◽  
pp. 202-227 ◽  
Author(s):  
M. W. Vischer ◽  
V. M. Bajo ◽  
J. S. Zhang ◽  
E. Calciati ◽  
C. A. Haenggeli ◽  
...  
Keyword(s):  
Electrical Stimulation ◽  
Inferior Colliculus ◽  
Unit Activity ◽  
Single Unit ◽  
Single Unit Activity ◽  
Stimulation Of

scholarly journals Modulation of Cochlear Afferent Response by the Lateral Olivocochlear System: Activation Via Electrical Stimulation of the Inferior Colliculus

2003 ◽  
Vol 90 (5) ◽  
pp. 3178-3200 ◽  
Author(s):  
J. Alan Groff ◽  
M. Charles Liberman
Keyword(s):  
Inferior Colliculus ◽  
Hair Cells ◽  
Otoacoustic Emissions ◽  
Round Window ◽  
Acoustic Stimulus ◽  
Outer Hair Cells ◽  
Olivocochlear System ◽  
Compound Action Potentials ◽  
The Face ◽  
Afferent Response

The olivocochlear (OC) efferent innervation of the mammalian inner ear consists of two subdivisions, medial (MOC) and lateral (LOC), with different peripheral terminations on outer hair cells and cochlear afferent terminals, respectively. The cochlear effects of electrically activating MOC efferents are well known, i.e., response suppression effected by reducing outer hair cells' contribution to cochlear amplification. LOC peripheral effects are unknown, because their unmyelinated axons are difficult to electrically stimulate. Here, stimulating electrodes are placed in the inferior colliculus (IC) to indirectly activate the LOC system, while recording cochlear responses bilaterally from anesthetized guinea pigs. Shocks at some IC sites produced novel cochlear effects attributable to activation of the LOC system: long-lasting (5–20 min) enhancement or suppression of cochlear neural responses (compound action potentials and round window noise), without changes in cochlear responses dominated by outer hair cells (otoacoustic emissions and cochlear microphonics). These novel effects also differed from classic MOC effects in their lack of dependence on the level and frequency of the acoustic stimulus. These effects disappeared on sectioning the entire OC bundle, but not after selective lesioning of the MOC tracts or the cochlea's autonomic innervation. We conclude that the LOC pathway comprises two functional subdivisions, capable of inducing slow increases or decreases in response magnitudes in the auditory nerve. Such a system may be useful in maintaining accurate binaural comparisons necessary for sound localization in the face of slow changes in interaural sensitivity.

Effect of early exposure to patterned sound on unit activity in rat inferior colliculus

1976 ◽  
Vol 39 (5) ◽  
pp. 1081-1089 ◽  
Author(s):  
B. M. Clopton ◽  
J. A. Winfield
Keyword(s):  
Inferior Colliculus ◽  
Unit Activity ◽  
Pattern Discrimination ◽  
Noise Burst ◽  
The Other ◽  
Early Exposure ◽  
Exposure Effect ◽  
Young Rats ◽  
Inhibitory Mechanisms ◽  
Pattern Noise

1. Young rats were exposed to one of two patterns of sounds for 5 h daily during the first 4 mo of life. The up pattern consisted of a tone swept from 6 to 9 kHz in 1 s alternated with a 1-s noise burst. The down pattern differed in that the sweeps were from 9 to 6 kHz. 2. A pattern evoked more spikes, on the average, from units in the inferior colliculus of rats exposed to that pattern than from units in animals exposed to the other pattern. 3. The exposure effect was most pronounced in the unit responses to the noise-burst segment within a pattern suggesting a long-lasting, malleable influence of the tone sweep which defined the pattern. Responses to pattern noise components were less for both exposed groups than for the unexposed controls, suggesting that inhibitory mechanisms were responsible for the pattern discrimination evident in the responses of the exposed unit population. 4. Unit responses in unexposed rats were somewhat more selective for the down pattern so that the resulting shift in response selectivity was relatively more apparent for exposure to the up pattern. 5. While control and down-exposed units generally responded more to both the tone sweep and noise burst in one pattern, a large proportion of the up-exposed unit population continued to favor the down over the up-swept tone, but responded more to the up-pattern noise bursts. This suggests that the unit responses to the noise bursts did not simply reflect prolonged responses to the tone sweeps. 6. No similar effects were seen for units from mothers similarly exposed to the same patterns.

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