scholarly journals Interaction of excitation and inhibition in processing of pure tone and amplitude-modulated stimuli in the medial superior olive of the mustached bat

1994 ◽  
Vol 71 (2) ◽  
pp. 706-721 ◽  
Author(s):  
B. Grothe
Keyword(s):  
Discharge Rate ◽  
Stimulus Frequency ◽  
Spontaneous Discharge ◽  
Band Pass Filter ◽  
Response Patterns ◽  
Medial Superior Olive ◽  
Pass Filter ◽  
Superior Olive ◽  
Mustached Bat ◽  
Discharge Patterns

1. In mammals with good low-frequency hearing, the medial superior olive (MSO) processes interaural time or phase differences that are important cues for sound localization. Its cells receive excitatory projections from both cochlear nuclei and are thought to function as coincidence detectors. The response patterns of MSO neurons in most mammals are predominantly sustained. In contrast, the MSO in the mustached bat is a monaural nucleus containing neurons with phasic discharge patterns. These neurons receive projections from the contralateral anteroventral cochlear nucleus (AVCN) and the ipsilateral medial nucleus of the trapezoid body (MNTB). 2. To further investigate the role of the MSO in the bat, the responses of 252 single units in the MSO to pure tones and sinusoidal amplitude-modulated (SAM) stimuli were recorded. The results confirmed that the MSO in the mustached bat is tonotopically organized, with low frequencies in the dorsal part and high frequencies in the ventral part. The 61-kHz region is overrepresented. Most neurons tested (88%) were monaural and discharged only in response to contralateral stimuli. Their response could not be influenced by stimulation of the ipsilateral ear. 3. Only 11% of all MSO neurons were spontaneously active. In these neurons the spontaneous discharge rate was suppressed during the stimulus presentation. 4. The majority of cells (85%) responded with a phasic discharge pattern. About one-half (51%) responded with a level-independent phasic ON response. Other phasic response patterns included phasic OFF or phasic ON-OFF, depending on the stimulus frequency. Neurons with ON-OFF discharge patterns were most common in the 61-kHz region and absent in the high-frequency region. 5. Double tone experiments showed that at short intertone intervals the ON response to the second stimulus or the OFF response to the first stimulus was inhibited. 6. In neuropharmacological experiments, glycine applied to MSO neurons (n = 71) inhibited any tone-evoked response. In the presence of the glycine antagonist strychnine the response patterns changed from phasic to sustained (n = 35) and the neurons responded to both tones presented in double tone experiments independent of the intertone interval (n = 5). The effects of strychnine were reversible. 7. Twenty of 21 neurons tested with sinusoidally amplitude-modulated (SAM) signals exhibited low-pass or band-pass filter characteristics. Tests with SAM signals also revealed a weak temporal summation of inhibition in 13 of the 21 cells tested.(ABSTRACT TRUNCATED AT 400 WORDS)

Medial Superior Olive in the Free-Tailed Bat: Response to Pure Tones and Amplitude-Modulated Tones

1997 ◽  
Vol 77 (3) ◽  
pp. 1553-1565 ◽  
Author(s):  
Benedikt Grothe ◽  
Thomas J. Park ◽  
Gerd Schuller
Keyword(s):  
Temporal Structure ◽  
Indirect Evidence ◽  
Medial Superior Olive ◽  
Pass Filter ◽  
Low Pass Filter ◽  
Superior Olive ◽  
Rate Level ◽  
Binaural Stimulation ◽  
Low Pass ◽  
Pure Tones

Grothe, Benedikt, Thomas J. Park, and Gerd Schuller. Medial superior olive in the free-tailed bat: response to pure tones and amplitude-modulated tones. J. Neurophysiol. 77: 1553–1565, 1997. In mammals with good low-frequency hearing and a moderate to large interear distance, neurons in the medial superior olive (MSO) are sensitive to interaural time differences (ITDs). Most small mammals, however, do not hear low frequencies and do not experience significant ITDs, suggesting that their MSOs participate in functions other than ITD coding. In one bat species, the mustached bat, the MSO is a functionally monaural nucleus, acting as a low-pass filter for the rate of sinusoidally amplitude-modulated (SAM) stimuli. We investigated whether the more typical binaural MSO of the Mexican free-tailed bat also acts as an SAM filter. We recorded from 60 MSO neurons with their best frequencies covering the entire audiogram of this bat. The majority revealed bilateral excitation and indirect evidence for inhibition (EI/EI; 55%). The remaining neurons exhibited reduced inputs, mostly lacking ipsilateral inputs (28% I/EI; 12% O/EI; 5% EI/O). Most neurons (64%) responded with a phasic discharge to pure tones; the remaining neurons exhibited an additional sustained component. For stimulation with pure tones, two thirds of the cells exhibited monotonic rate-level functions for ipsilateral, contralateral, or binaural stimulation. In contrast, nearly all neurons exhibited nonmonotonic rate-level functions when tested with SAM stimuli. Eighty-eight percent of the neurons responded with a phase-locked discharge to SAM stimuli at low modulation rates and exhibited low-pass filter characteristics in the modulation transfer function (MTF) for ipsilateral, contralateral, and binaural stimulation. The MTF for ipsilateral stimulation usually did not match that for contralateral stimulation. Introducing interaural intensity differences (IIDs) changed the MTF in unpredictable ways. We also found that responses to SAMs depended on the carrier frequency. In some neurons we measured the time course of the ipsilaterally and contralaterally evoked inhibition by presenting brief frequency-modulated sweeps at different ITDs. The duration and timing of inhibition could be related to the SAM cutoff for binaural stimulation. We conclude that the response of the MSO in the free-tailed bat is created by a complex interaction of inhibition and excitation. The different time constants of inputs create a low-pass filter for SAM stimuli. However, the MSO output is an integrated response to the temporal structure of a stimulus as well as its azimuthal position, i.e., IIDs. There are no in vivo results concerning filter characteristics in a “classical” MSO, but our data confirm an earlier speculation about this interdependence based on data accessed from a gerbil brain slice preparation.

Afferent renal inputs to paraventricular nucleus vasopressin and oxytocin neurosecretory neurons

1998 ◽  
Vol 275 (6) ◽  
pp. R1745-R1754 ◽  
Author(s):  
John Ciriello
Keyword(s):  
Electrical Stimulation ◽  
Paraventricular Nucleus ◽  
Discharge Rate ◽  
Sensory Information ◽  
Renal Nerves ◽  
Spontaneous Discharge ◽  
Unit Recording ◽  
Neurosecretory Neurons ◽  
Discharge Patterns ◽  
Stimulation Of

Extracellular single-unit recording experiments were done in pentobarbital sodium-anesthetized rats to investigate the effects of electrical stimulation of afferent renal nerves (ARN) and renal vein (RVO) or artery (RAO) occlusion on the discharge rate of putative arginine vasopressin (AVP) and oxytocin (Oxy) neurons in the paraventricular nucleus of the hypothalamus (PVH). PVH neurons antidromically activated by electrical stimulation of the neurohypophysis were classified as either AVP or Oxy secreting on the basis of their spontaneous discharge patterns and response to activation of arterial baroreceptors. Ninety-eight putative neurosecretory neurons in the PVH were tested for their response to electrical stimulation of ARN: 44 were classified as putative AVP and 54 as putative Oxy neurons. Of the 44 AVP neurons, 52% were excited, 7% were inhibited, and 41% were nonresponsive to ARN stimulation. Of the 54 Oxy neurons, 43% were excited, 6% inhibited, and 51% were not affected by ARN. An additional 45 neurosecretory neurons (29 AVP and 16 Oxy neurons) were tested for their responses to RVO and/or RAO. RVO inhibited 42% of the putative AVP neurons and 13% of the putative Oxy neurons. On the other hand, RAO excited 33% of the AVP and 9% of the Oxy neurons. No AVP or Oxy neurons were found to be excited by RVO or inhibited by RAO. These data indicate that sensory information originating in renal receptors alters the activity of AVP and Oxy neurons in the PVH and suggest that these renal receptors contribute to the hypothalamic control of AVP and Oxy release into the circulation.

Interaural time and intensity coding in superior olivary complex and inferior colliculus of the echolocating bat Molossus ater

1985 ◽  
Vol 53 (1) ◽  
pp. 89-109 ◽  
Author(s):  
G. Harnischfeger ◽  
G. Neuweiler ◽  
P. Schlegel
Keyword(s):  
Inferior Colliculus ◽  
Stimulus Frequency ◽  
Stimulus Onset ◽  
Time Difference ◽  
Superior Olivary Complex ◽  
Inhibitory Input ◽  
Medial Superior Olive ◽  
Transient Time ◽  
Interaural Time Differences ◽  
Superior Olive

Single-unit responses to tonal stimulation with interaural disparities were recorded in the nuclei of the superior olivary complex (SOC) and the central nucleus of the inferior colliculus (ICC) of the echolocating bat, Molossus ater. Seventy-six units were recorded from the ICC and 74 from the SOC; of the SOC units, 31 were histologically verified in the medial superior olive (MSO), 10 in the lateral superior olive (LSO), and 33 in unidentified areas of the SOC. Best frequencies (BFs) of the units ranged from 10.3 to 89.6 kHz, and Q10 dB values ranged from 2 to 70 dB. Most ICC neurons responded phasically to stimulus onset and were either inhibitory/excitatory [I/E; (53)] or excitatory/excitatory [E/E; (21)] units. In the MSO, 23 units responded tonically and 7 phasically on, 18 were E/E or E/OF (facilitatory for other input) units, and 11 were I/E neurons. All LSO neurons responded in a "chopper" fashion, and the binaural neurons were E/I units. In E/E units the excitatory response to binaural stimulation was frequently larger than the sum of the monaurally evoked responses. Many neurons with E/I or I/E inputs had very steep binaural impulse-count functions and were sensitive to small interaural intensity differences. Twenty-eight units (24%) responded with a change in firing rate of at least 20% to interaural time differences of +/- 500 microseconds. Within this sample, 11 units (8 from ICC, 2 from MSO, and 1 from SOC) were sensitive to interaural time differences of only +/- 50 microseconds. Of these 11 units, 10 were I/E units responding phasically only to stimulus onset and were also sensitive to intensity differences (delta I), being suppressed completely by the inhibitory input over a delta I range of 20 dB or less. Of 117 units tested in the ICC and SOC nuclei, 86 units (76%) were not sensitive to interaural time disparities within +/- 500 microseconds. Because the BFs of these units sensitive to interaural transient time differences (delta t) ranged between 18 and 90 kHz, responses were elicited by pure tones, and responses did not change periodically with the period equal to that of the stimulus frequency, we conclude that the neurons reacted to interaural differences of stimulus-onset time (transient time difference) but not to phase differences (ongoing time difference). Sensitivity to interaural time differences was also correlated with interaural intensity differences.(ABSTRACT TRUNCATED AT 400 WORDS)

Functional organization of lateral cell groups of cat superior olivary complex

1977 ◽  
Vol 40 (2) ◽  
pp. 296-318 ◽  
Author(s):  
C. Tsuchitani
Keyword(s):  
Superior Olivary Complex ◽  
Maximum Output ◽  
Medial Superior Olive ◽  
Superior Olive ◽  
Response Characteristics ◽  
Cell Groups ◽  
Discharge Patterns ◽  
Intensity Functions ◽  
Contralateral Stimulus ◽  
Stimulation Of

1. Single-unit discharges to auditory stimuli were recorded extracellularly from superior olivary complex (SOC) units located lateral to the medial superior olive. Stimuli consisted of monaurally or binaurally presented tone bursts. The response measures obtained were effective ear, nature of effect, stimulus-frequency representation, maximum output, latency of response, and temporal pattern of tone burst-elicited discharges. Electrolytic marks were made at the unit studied or at the end of the electrode tract and in the medial superior olive. Following each experiment the locations of the units studied were determined histologically. An atlas of the laterally located SOC cell groups was developed to permit classification of units on the basis of localization within cell groups. Units were also classified according to the effects of stimulating the two ears. 2. All SOC units located lateral to the medial superior olive were excited by stimulation of the ipsilateral ear. Stimulation of the contralateral ear either excited, inhibited, had no effect, or had a potentiating effect on the discharges elicited by stimulating the ipsilateral ear. 3. Most lateral superior olivary (LSO) units were inhibited by contralateral stimulation, were narrowly tuned, produced low to high levels of maximum output, had short latencies, and produced regular discharge patterns characterized by chopper PST histograms with narrow initial peaks. 4. Most units within the caudal margins of the LSO (pLSO) were not affected or were inhibited by a contralateral stimulus; many were broadly tuned and exhibited intensity functions with large dynamic range and low slope. These units also had long latencies and produced chopper PST histograms with wide initial peaks. 5. Most units located dorsal to the LSO (DPO and DLPO) were not affected by the contralateral stimulus, were narrowly tuned, produced moderate levels of maximum discharge, had long latencies, and produced chopper PST histograms with wide initial peaks. 6. Units located ventral to the LSO appeared to have response characteristics related to unit location. Most units below the ventral hilum of the LSO (VLPO) were inhibited by the contralateral stimulus and many were broadly tuned VLPO units produced wide or poorly defined narrow-chopper discharge patterns and intensity functions with high maximum output. Most units located ventral to the lateral loop of the LSO (LNTB) were not affected by the contralateral stimulus and had response characteristics that may be related to the rostrocaudal location of the unit. 7. The cell groups located dorsal and ventral to the LSO were tonotopically organized with low-frequency-sensitive units located laterally and high-frequency-sensitive units located medially. The units located along the caudal margins of the LSO had a tonotopic organization similar to that of the LSO.

Low-frequency neurons in the lateral superior olive exhibit phase-sensitive binaural inhibition

1991 ◽  
Vol 65 (3) ◽  
pp. 598-605 ◽  
Author(s):  
P. G. Finlayson ◽  
D. M. Caspary
Keyword(s):  
Discharge Rate ◽  
Low Frequency ◽  
Lateral Superior Olive ◽  
Superior Olive ◽  
Total Inhibition ◽  
Interaural Phase ◽  
Phase Sensitive ◽  
Evoked Activity ◽  
Discharge Patterns ◽  
Contralateral Stimulus

1. Responses of low characteristic frequency (CF) neurons in the lateral limb of the lateral superior olive (LSO) of chinchilla and rat to binaural stimuli at various interaural phase and intensity differences were examined and compared to responses from previous studies of high CF neurons. 2. Ninety-six LSO neurons from chinchillas and 10 LSO neurons from rats with CFs less than 1,200 Hz were characterized. The majority of these neurons displayed phase-locked tone-evoked temporal discharge patterns to ipsilateral CF stimuli. 3. Similar to high-CF LSO neurons, low-CF LSO neurons were excited by ipsilateral stimuli and inhibited by contralateral stimuli, with discharge rate sensitive to interaural intensity differences (IID). Discharge rate increased as ipsilateral intensity was increased and decreased as contralateral stimulus intensity was increased. 4. Binaural inhibition, inhibition of ipsilaterally evoked activity by contralateral stimuli, was dependent on interaural phase differences (IPD) in the majority of low-CF LSO neurons. Responses of phase-sensitive neurons to binaural stimuli often varied with 90 or 180 degrees changes in IPD from total inhibition to a facilitated response when compared to responses to control ipsilateral stimuli alone. 5. In summary, like high-CF LSO neurons, LSO neurons with low CFs (less than 1,200 Hz) were ipsilaterally excited and contralaterally inhibited (EI) and were sensitive to IID. Unlike most high-CF EI LSO neurons, which are not responsive when the azimuth of the stimulus is directly in front of or directly behind the animal, many low-CF LSO neurons are responsive to these stimuli.(ABSTRACT TRUNCATED AT 400 WORDS)

Binaural properties of single units in the superior olivary complex of the mustached bat

1991 ◽  
Vol 66 (3) ◽  
pp. 1080-1094 ◽  
Author(s):  
E. Covey ◽  
M. Vater ◽  
J. H. Casseday
Keyword(s):  
Frequency Tuning ◽  
Stimulus Frequency ◽  
Frequency Component ◽  
Sound Level ◽  
Single Units ◽  
Superior Olivary Complex ◽  
Medial Superior Olive ◽  
Superior Olive ◽  
Response Characteristics ◽  
Contralateral Ear

1. Previous studies of the superior olive of echolocating bats suggest that the lateral superior olive (LSO) retains the same structure and function as in other mammals but that the medial superior olive (MSO) is different in structure and possibly also in function. The present study is an examination of this idea in Pteronotus parnellii, a bat that has a large and well-defined MSO. 2. Using pure tones presented via earphones, we obtained data on frequency tuning for 60 single units and 96 multiunits in LSO and 94 single units and 154 multiunits in MSO. Of these we also obtained binaural response characteristics from 55 single units in LSO and 72 single units in MSO. 3. LSO and MSO each have a complete tonotopic representation, arranged in a sequence similar to that of other mammals studied. However, in both LSO and MSO there is an expanded representation of the frequencies around 60 kHz, the main frequency component of the bat's echolocation call; there is another expanded representation of the range around 90 kHz, the third harmonic of the call. The expansion of these frequency ranges suggests that the functions of LSO and MSO in Pteronotus are related to echolocation behavior. 4. The binaural characteristics of cells in LSO were essentially the same as those seen in other mammals. Most LSO units (93%) were excited by the ipsilateral ear and inhibited by the contralateral ear. The responses of nearly all LSO units were completely suppressed when the sound level at the two ears was equal. 5. The binaural characteristics of cells in MSO were different from those in nonecholocating mammals. Most MSO units (72%) were excited by the contralateral ear but were neither excited nor inhibited by the ipsilateral ear. Of the remaining units, 21% were excited by the contralateral ear and inhibited by the ipsilateral ear, and only 6% were excited by both ears. 6. The temporal discharge patterns of units in MSO differed from the tonic response pattern seen in LSO. Most MSO units had phasic response patterns, with a few spikes at the onset or offset of the stimulus; the response often changed from ON to OFF depending on stimulus frequency. 7. The results support the idea that in evolution LSO has remained unchanged, whereas MSO has undergone adaptation. The function of LSO in Pteronotus seems to be identical to that in other mammals, i.e., analysis of interaural sound level differences to derive azimuthal location. The function of MSO in Pteronotus must be different from that in nonecholocating mammals.(ABSTRACT TRUNCATED AT 400 WORDS)

scholarly journals Discharge patterns in the lateral superior olive of decerebrate cats

2012 ◽  
Vol 108 (7) ◽  
pp. 1942-1953 ◽  
Author(s):  
Nathaniel T. Greene ◽  
Kevin A. Davis
Keyword(s):  
Discharge Rate ◽  
Full Range ◽  
Stimulus Onset ◽  
Lateral Superior Olive ◽  
Superior Olive ◽  
Shape Adaptation ◽  
Discharge Patterns ◽  
Decerebrate Cats ◽  
Sustained Discharge ◽  
Initial Peak

Anatomical and pharmacological studies have shown that the lateral superior olive (LSO) receives inputs from a number of sources and that LSO cells can alter the balance of their own excitatory and inhibitory drive. It is thus likely that the ongoing sound-evoked responses of LSO cells reflect a complex interplay of excitatory and inhibitory events, which may be affected by anesthesia. The goal of this study was to characterize the temporal discharge patterns of single units in the LSO of unanesthetized, decerebrate cats in response to long-duration ipsilateral best-frequency tone bursts. A decision tree is presented to partition LSO units on the basis of poststimulus time histogram shape, adaptation of instantaneous firing rate as a function of time, and sustained discharge rate. The results suggest that LSO discharge patterns form a continuum with four archetypes: sustained choppers that show two or more peaks of activity at stimulus onset and little adaptation of rate throughout the response, transient choppers that undergo a decrease in rate that eventually stabilizes with time, primary-like units that display an initial peak of activity followed by a monotonic decline in rate to a steady-state value, and onset-sustained units that exhibit an initial peak of activity at stimulus onset followed by a low sustained activity. Compared with the chopper units, the nonchopper units tend to show longer first-spike latencies, lower peak firing rates, and more irregular sustained discharge patterns. Modeling studies show that the full range of LSO response types can be obtained from an underlying sustained chopper by varying the strength and latency of a sound-driven ipsilateral inhibition relative to that of excitation. Together, these results suggest that inhibition plays a major role in shaping the temporal discharge patterns of units in unanesthetized preparations.

scholarly journals Medial Superior Olive of the Big Brown Bat: Neuronal Responses to Pure Tones, Amplitude Modulations, and Pulse Trains

2001 ◽  
Vol 86 (5) ◽  
pp. 2219-2230 ◽  
Author(s):  
Benedikt Grothe ◽  
Ellen Covey ◽  
John H. Casseday
Keyword(s):  
Interstimulus Interval ◽  
Modulation Frequency ◽  
Medial Superior Olive ◽  
Echolocation Call ◽  
Pass Filter ◽  
Low Pass Filter ◽  
Mustached Bat ◽  
Big Brown Bat ◽  
Low Pass ◽  
Contralateral Ear

The structure and function of the medial superior olive (MSO) is highly variable among mammals. In species with large heads and low-frequency hearing, MSO is adapted for processing interaural time differences. In some species with small heads and high-frequency hearing, the MSO is greatly reduced in size; in others, including those echolocating bats that have been examined, the MSO is large. Moreover, the MSO of bats appears to have undergone different functional specializations depending on the type of echolocation call used. The echolocation call of the mustached bat contains a prominent CF component, and its MSO is predominantly monaural; the free-tailed bat uses pure frequency-modulated calls, and its MSO is predominantly binaural. To further explore the relation of call structure to MSO properties, we recorded extracellularly from 97 single neurons in the MSO of the big brown bat, Eptesicus fuscus, a species whose echolocation call is intermediate between that of the mustached bat and the free-tailed bat. The best frequencies of MSO neurons in the big brown bat ranged from 11 to 79 kHz, spanning most of the audible range. Half of the neurons were monaural, excited by sound at the contralateral ear, while the other half showed evidence of binaural interactions, supporting the idea that the binaural characteristics of MSO neurons in the big brown bat are midway between those of the mustached bat and the free-tailed bat. Within the population of binaural neurons, the majority were excited by sound at the contralateral ear and inhibited by sound at the ipsilateral ear; only 21% were excited by sound at either ear. Discharge patterns were characterized as transient on (37%), primary-like (33%), or transient off (23%). When presented with sinusoidally amplitude modulated tones, most neurons had low-pass filter characteristics with cutoffs between 100 and 300 Hz modulation frequency. For comparison with the sinusoidally modulated sounds, we presented trains of tone pips in which the pulse duration and interstimulus interval were varied. The results of these experiments indicated that it is not the modulation frequency but rather the interstimulus interval that determines the low-pass filter characteristics of MSO neurons.

Characteristics of period doubling in the human cone flicker electroretinogram

2005 ◽  
Vol 22 (6) ◽  
pp. 817-824 ◽  
Author(s):  
KENNETH R. ALEXANDER ◽  
MICHAEL W. LEVINE ◽  
BOAZ J. SUPER
Keyword(s):  
Harmonic Component ◽  
Stimulus Frequency ◽  
Period Doubling ◽  
Feedback Signal ◽  
Band Pass Filter ◽  
Nonlinear Feedback ◽  
Higher Harmonics ◽  
Pass Filter ◽  
Cone System ◽  
Harmonic Components

Electroretinogram (ERG) responses of the cone system to a flickering stimulus can exhibit a cyclic variation in amplitude. This phenomenon of synchronous period doubling has been attributed to a nonlinear feedback mechanism within the retina that alters response gain. The aim of the present study was to investigate intersubject variability in period doubling in the ERG of the human cone system, and to assess the implications of this variability for signal processing within the retina. Period doubling was examined in a group of 12 visually normal subjects, using sinusoidal full-field flicker and harmonic analysis of the ERG waveforms. For all subjects, the ERG responses to 32-Hz flicker (a frequency commonly used clinically) were characterized by a harmonic component at the stimulus frequency and at higher harmonics that were integral multiples of the stimulus frequency, as expected. In addition, six of the subjects showed period doubling at 32 Hz, characterized by harmonic components at integer multiples of a frequency that was half the stimulus frequency (the subharmonic). However, the subharmonic itself did not exceed the noise level. These findings suggest that the subharmonic is generated prior to or at the site that produces the nonlinear higher harmonics of the ERG response, and that a subsequent band-pass filter attenuates this subharmonic. Examination of harmonic components of the subjects' ERG waveforms at other stimulus frequencies, as well as a cycle-by-cycle analysis of the ERG waveforms, suggested that individual differences in period doubling may be due to intersubject variation in the strength of the hypothesized feedback signal and/or the time constant of its decay.

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