Philip Jen | University of Missouri Columbia (original) (raw)

Papers by Philip Jen

The Journal of Experimental Biology, Sep 1, 1995

In acoustically guided behavior, most mammals move their pinnae conjunctively or disjunctively du... more In acoustically guided behavior, most mammals move their pinnae conjunctively or disjunctively during sound localization. While the head of an animal is a major source of reflections and diffractions in the sound field, the two pinnae are the most distinctive parts of that three-dimensional geometry (Roth et al. 1980). The deflections and reflections of sound by the pinna surface have been shown to affect both interaural time and pressure differences, which are the two main cues for sound localization along the horizontal plane, and to produce interaural spectral differences to localize sound in the elevational plane (van Bergeijk, 1962; Neti et al. 1992). Because of this, the directionality of sound pressure transformation at the pinna of an animal contributes importantly to the directional sensitivity of auditory neurons, which provide the neural basis for sound localization.

Hearing Research, Jul 1, 1988

The directionality of sound pressure transformation at the pinna of three species of bats was stu... more The directionality of sound pressure transformation at the pinna of three species of bats was studied by measuring the sound pressure level of a tone (25 45 65 and 85 kHz) at the tympanic membrane as a function of azimuth and elevation of the sound source under free-field conditions. The tympanic sound pressure level varied with location of the sound source. The directionality of sound pressure transformation pattern of the pinna of each bat was studied by plotting isopressure contours. The area within each isopressure contour decreased with increasing tonal frequency. For each tonal frequency, the point of maximal sound pressure was always located in the frontal ipsilateral sound field. This point shifted medially with increasing tonal frequency along the horizontal plane in all species tested, but it shifted in a species-specific manner along the vertical plane. Removal or distortion of the pinna and tragus resulted in either uncircumscribed or irregular isopressure contours for all tonal frequencies tested. Acoustic pressure gain of the external ear reached 16-23 dB for frequencies at 15-18 kHz. The importance of the external ear to the directionality of the bat&amp;#39;s echolocation system is discussed.

Frontiers in Public Health, Sep 16, 2022

Background: Hearing loss a ects over. billion individuals worldwide. Their disability and limited... more Background: Hearing loss a ects over. billion individuals worldwide. Their disability and limited access to the coronavirus (COVID-) pandemic information make them su er a greater degree than ordinary people. However, the quantitative studies on the implementation of behavior compliance with preventive health measures for vulnerable groups such as people with hearing disability were limited. The purpose of this study was to explore the compliance with pandemic-related protective health measures among people with hearing disability.

Hearing Research, Dec 1, 2002

This study examined the effect of monaural middle ear destruction on auditory responses to sound ... more This study examined the effect of monaural middle ear destruction on auditory responses to sound direction in the inferior colliculus (IC) of the laboratory mice, Mus musculus. Monaural middle ear destruction was performed on juvenile and adult mice (the experimental mice). Auditory response properties of neurons to ipsilateral and contralateral sounds (I-40 degrees and C-40 degrees ) were examined in the IC ipsilateral to the intact ear 4 weeks later. IC neurons of control mice had higher minimum thresholds (MTs), larger Q(n) (Q(10), Q(30)) values but smaller dynamic ranges at I-40 degrees than at C-40 degrees. These direction-dependent response properties were not observed for IC neurons of experimental juvenile and adult mice. However, Q(n) values of IC neurons were significantly smaller in experimental juvenile than in control and experimental adult mice. Normal tonotopic organization in terms of positive correlation between recording depth and best frequency (BF) was observed in the IC of control and experimental adult mice at both sound directions but not in the IC of experimental juvenile mice. A positive correlation of increasing MT with BF was only observed for IC neurons in control mice but not in both experimental mice. Possible mechanisms for these different response properties are discussed.

Brain Research, Aug 1, 1996

By combining HRP histochemistry with Fos immunocytochemistry, we demonstrate in this study that e... more By combining HRP histochemistry with Fos immunocytochemistry, we demonstrate in this study that electrophysiologically characterized auditory neurons can be double-labeled with HRP and Fos after iontophoretic injection of HRP into the recording site. Neurons which projected fibers to the recording site were labeled with HRP and were Fos-like immunoreactive. This double-labeling technique in combination with electrophysiological recording offers the possibility to determine the fiber projections between soundactivated neurons which are identified either electrophysiologically and/or immunocytochemically.

Frontiers in Biology, Apr 1, 2010

For survival, bats of the suborder Microchiropetra emit intense ultrasonic pulses and analyze the... more For survival, bats of the suborder Microchiropetra emit intense ultrasonic pulses and analyze the weak returning echoes to extract the direction, distance, velocity, size, and shape of the prey. Although these bats and other mammals share the common layout of the auditory pathway and sound coding mechanism, they have highly developed auditory systems to process biologically relevant pulses at the expense of a reduced visual system. During this active biosonar behavior, they progressively shorten the pulse duration, decrease the amplitude and pulse-echo gap as they search, approach and finally intercept the prey. Presumably, these changes in multiple pulse parameters throughout the entire course of hunting enable them to extract maximal information about localized prey from the returning echoes. To hunt successfully, the auditory system of these bats must be less sensitive to intense emitted pulses but highly sensitive to weak returning echoes. They also need to recognize and differentiate the echoes of their emitted pulses from echoes of pulses emitted by other conspecifics. Past studies have shown the following mechanical and neural adaptive mechanisms underlying the successful bat biosonar behavior: (1) Forward orienting and highly mobile pinnae for effective scanning, signal reception, sound pressure transformation and mobile auditory sensitivity; (2) Avoiding and detecting moving targets more successfully than stationary ones; (3) Coordinated activity of highly developed laryngeal and middle ear muscles during pulse emission and reception; (4) Mechanical and neural attenuation of intense emitted pulses to prepare for better reception of weak returning echoes; (5) Increasing pulse repetition rate to improve multiple-parametric selectivity to echoes; (6) Dynamic variation of duration selectivity and recovery cycle of auditory neurons with hunting phase for better echo analysis; (7) Maximal multiple-parametric selectivity to expected echoes returning within a time window after pulse emission; (8) Pulse-echo delaysensitive neurons in higher auditory centers for echo ranging; (9) Corticofugal modulation to improve ongoing multiple-parametric signal processing and reorganize signal representation, and (10) A large area of the superior colliculus, pontine nuclei and cerebellum that is sensitive to sound for sensori-motor integration. All these adaptive mechanisms facilitate the bat to effectively extract prey features for successful hunting.

Brain Research, Dec 1, 1982

Single units (125) which faithfully discharged action potentials to acoustic stimuli (35 ms in du... more Single units (125) which faithfully discharged action potentials to acoustic stimuli (35 ms in duration with 0.5 ms rise and decay times) were recorded in the cerebellar vermis and hemispheres of the CF-FM bat, Pteronotus parnellii. These units had response latencies between 1.5 and 27 ms and minimum thresholds between 2 and 83.5 dB SPL. Best frequencies (BFs) of these units ranged from 30.32 to 79.28 kHz, but more than half (64 units, 51.2%) were between 59.73 and 63.32 kHz. While most tuning curves of these units were either broad or irregular, those curves with BFs tuned at around 61 kHz which is the frequency of the predominant CF component of the bat&amp;#39;s echolocation signals were extremely narrow with Q10-dB values as high as 153. Those units (29) with BFs tuned near the 61 kHz also showed off-responses. These data indicate that auditory specialization for processing of species-specific orientation signals also exists in the cerebellum of this bat.

Brain Research, Sep 1, 1983

Using conventional electrophysiological techniques, we demonstrate that neurons in the superior c... more Using conventional electrophysiological techniques, we demonstrate that neurons in the superior colliculus of the big brown bat (Eptesicusfuscus) respond to ultrasonic signals. Most response properties of these neurons are very similar to neurons of the inferior colliculus in the same bat.

Neuroscience, Apr 1, 2013

; IC ES , electrically stimulated IC; IC Mdu , modulated IC; IPI, inter-pulse interval; MT, minim... more ; IC ES , electrically stimulated IC; IC Mdu , modulated IC; IPI, inter-pulse interval; MT, minimum threshold; PST, peri-stimulus-time; Q 10 , ratio between bandwidth of FTC in 10 dB above MT and BF.

Brain Research, Mar 1, 1992

Using free-field acoustic stimulation conditions, we studied the response properties and spatial ... more Using free-field acoustic stimulation conditions, we studied the response properties and spatial sensitivity of 146 pontine neurons of the big brown bat, Eptesicus fuscus. The best frequency (BF) and minimum threshold (MT) of a pontine neuron were first determined with a sound broadcast from a loudspeaker placed ahead of the bat. A BF sound was delivered from the loudspeaker as it moved across the frontal auditory space in order to locate the response center at which the neuron had its lowest MT. Then the basic response properties of the neuron to a sound delivered from the response center were studied. As in inferior collicular and auditory cortical neurons, pontine neurons can be characterized as phasic responders, phasic bursters and tonic responders. They have both monotonic and non-monotonic intensityrate functions. However, most of them are broadly tuned as are cerebellar neurons. Auditory spatial sensitivity was studied for 144 pontine neurons. In 9 neurons, variation of MT with a BF sound delivered from several azimuthal and elevational angles along the horizontal and vertical planes crossing the neuron's response center was measured. In addition, variation in the number of impulses with several stimulus intensities at 10 dB increments above a neuron's MT delivered from each angle was also studied. The auditory spatial sensitivity of other pontine neurons was studied by measuring the response area of each neuron with stimulus intensities at 3, 5, 10, 15 or 40 dB above its lowest MT. The response areas of pontine neurons expanded asymmetrically with stimulus intensity, but the size of the response area was not correlated with either MT or BE In half of the pontine neurons studied, the response area expanded greatly and eventually covered almost the entire frontal auditory space. The response areas of the other half of the pontine neurons only expanded to a restricted area of frontal auditory space. Two possible neural mechanisms underlying these two types of response areas are hypothesized. The response centers of all 144 neurons were located within a small area of the frontal auditory space. The locations of response centers of these neurons are not correlated with their BFs. The distribution pattern of these response centers is comparable to that of superior collicular and cerebellar neurons but is different from that of inferior collicular and auditory cortical neurons. The results of our study suggest that auditory information is integrated in the pontine nuclei before being further sent into the cerebellum.

Hearing Research, Jun 1, 2002

This study examined auditory responses of two simultaneously recorded neurons in the central nucl... more This study examined auditory responses of two simultaneously recorded neurons in the central nucleus of bat inferior colliculus (IC) under two-tone stimulation conditions. We specifically examined how a sound within the excitatory frequency tuning curve (FTC) of one IC neuron might affect responses of the other IC neuron in amplitude and frequency domains. Under this specific two-tone stimulation condition, responses of 82% neurons were suppressed and their excitatory FTCs sharpened. Responses of the other 18% neurons were facilitated and their excitatory FTCs broadened. Two-tone suppression was greater at low than at high stimulus amplitudes. Two-tone suppression also decreased with increasing recording depth and best frequency (BF) difference between each pair of neurons. The suppressive or facilitatory FTC of a neuron plotted under two-tone stimulation conditions was always within the excitatory FTC of the other neuron. Two-tone suppression or two-tone facilitation was weak near the BF but became increasingly strong with frequencies away from the BF. Biological significance of these findings is discussed.

Neuroscience, Oct 1, 2008

During hunting, insectivorous bats such as Eptesicus fuscus progressively vary the repetition rat... more During hunting, insectivorous bats such as Eptesicus fuscus progressively vary the repetition rate, duration, frequency and amplitude of emitted pulses such that analysis of an echo parameter by bats would be inevitably affected by other co-varying echo parameters. The present study is to determine the variation of echo frequency selectivity of duration-tuned inferior collicular neurons during different phases of hunting using pulse-echo (P-E) pairs as stimuli. All collicular neurons discharge maximally to a tone at a particular frequency which is defined as the best frequency (BF). Most collicular neurons also discharge maximally to a BF pulse at a particular duration which is defined as the best duration (BD). A family of echo iso-level frequency tuning curves (iso-level FTC) of these duration-tuned collicular neurons is measured with the number of impulses in response to the echo pulse at selected frequencies when the P-E pairs are presented at varied P-E duration and gap. Our data show that these duration-tuned collicular neurons have narrower echo iso-level FTC when measured with BD than with non-BD echo pulses. Also, IC neurons with low BF and short BD have narrower echo iso-level FTC than IC neurons with high BF and long BD have. The bandwidth of echo iso-level FTC significantly decreases with shortening of P-E duration and P-E gap. These data suggest that duration-tuned collicular neurons not only can facilitate bat's echo recognition but also can enhance echo frequency selectivity for prey feature analysis throughout a target approaching sequence during hunting. These data also support previous behavior studies showing that bats prepare their auditory system to analyze expected returning echoes within a time window to extract target features after pulse emission.

Hearing Research, 1987

Using free-field acoustic stimulus conditions, we studied the auditory space representation in th... more Using free-field acoustic stimulus conditions, we studied the auditory space representation in the inferior colliculus (IC) of the big brown bat, Eptesicus fuscus, under different pinna positions. Stimuli were delivered from a loudspeaker placed 14 cm in front of the bat to determine the best frequency (BF) of an isolated neuron. A BF stimulus was then delivered as the loudspeaker was moved across the frontal auditory space of the bat to locate the response center of the neuron. At the response center, the neuron has its lowest minimum threshold (MT). The stimulus was then raised 5-dB above the lowest MT to measure the spatial response area. Both response center and spatial response area of each neuron were measured under different pinna positions. Variations in the response center and MT of each neuron under different pinna positions was determined and a possible reason for this variation was discussed. The variation in auditory space representation in the IC due to variation in pinna position is presented. We suggest that during echolocation a bat could make changes in its pinna position to create additional binaural disparity for accurate target localization.

Brain Research, May 1, 1984

The auditory response areas of 192 inferior collicular neurons (IC) of Eptesicusfuscus were studi... more The auditory response areas of 192 inferior collicular neurons (IC) of Eptesicusfuscus were studied under free field acoustic stimulation. The boundary of the auditory response area of a neuron expands with stimulus intensity (Fig. 1). However, there is a response center within each neuron's response area at which the neuron has the maximal sensitivity. All response centers of the 192 neurons are located within a limited space of the bat's contralateral auditory space. The position of the response center of a neuron changes with different pinna orientations (Figs. 2 and 3) providing a bat with versatility in maximizing the sensitivity of its echolocation system.

Journal of Comparative Physiology A-neuroethology Sensory Neural and Behavioral Physiology, Nov 15, 1999

This study examines the eect of temporally patterned pulse trains on duration tuning characterist... more This study examines the eect of temporally patterned pulse trains on duration tuning characteristics of inferior collicular neurons of the big brown bat, Eptesicus fuscus, under free-®eld stimulation conditions. Using a 50% dierence between maximal and minimal responses as a criterion, the duration tuning characteristics of inferior collicular neurons determined with pulse trains of dierent pulse durations are described as bandpass, long-pass, short-pass, and all-pass. Each band-pass neuron discharged maximally to a speci®c pulse duration that was at least 50% larger than the neuron's responses to a long-and a short-duration pulse. In contrast, each long-or short-pass neuron discharged maximally to a range of long-or short-duration pulses that were at least 50% larger than the minimal responses. The number of impulses of an all-pass neuron never diered by more than 50%. When pulse trains were delivered at dierent pulse repetition rates, the number of short-pass and band-pass neurons progressively increased with increasing pulse repetition rates. The slope of the duration tuning curves also became sharper when determined with pulse trains at high pulse repetition rates. Possible mechanisms underlying these ®ndings are discussed. Key words Bat á Inferior colliculus á Pulse duration tuning á Pulse gap á Pulse repetition rate Abbreviations BF best frequency á CD critical duration á IC inferior colliculus á MT minimum threshold á PRR pulse repetition rate

Brain Research, Apr 1, 2000

This study examined the role of GABAergic inhibition on direction-dependent sharpening of frequen... more This study examined the role of GABAergic inhibition on direction-dependent sharpening of frequency tuning curves (FTCs) in bat inferior collicular (IC) neurons under free field stimulation conditions. The minimum threshold (MT) at the neurons best frequency (BF) and the sharpness (Q , Q , Q) of FTCs of most IC neurons increased as the sound direction changed from contralateral azimuths to 10 20 30 ipsilateral azimuths. The application of GABA antagonist, bicuculline, lowered all MTs but the application did not abolish A direction-dependent variation in MT. MTs determined during bicuculline application at 40 ipsilateral were still significantly higher than those determined at 408 contralateral (two-tailed paired t-test, P,0.0001). In contrast, although application of bicuculline essentially had no effect on the BFs of IC neurons, it differentially broadened neurons FTCs at different azimuths abolishing the direction-dependent sharpening of frequency tuning (i.e. Q values, two-tailed paired t-test, P,0.01). These data indicate that GABAergic inhibition makes n an important contribution to the direction-dependent frequency tuning of most IC neurons.

The Journal of Experimental Biology, Aug 1, 1977

In the mustache bat (Pteronotus parnellii rubiginosus), the cochlear microphonic (CM) recorded fr... more In the mustache bat (Pteronotus parnellii rubiginosus), the cochlear microphonic (CM) recorded from the round window is sharply tuned at 61 kHz and shows a prominent transient response to a tone burst at about 61 kHz (i.e. its amplitude increases exponentially at the onset of the stimulus and decreases at its cessation). In terms of the time constant (I-I + 0-3 ms) and the resonance frequency (6I*I + 0-43 kHz) of this transient response, the Q of this system, assumed to correspond to a second-order filter, is 204 + 57. Peripheral neurones sensitive to 61 kHz have a very sharp excitatory area (or tuning curve). The Q of a tuning curve markedly increases with the rise in best frequency up to 61 kHz and decreases beyond 61 kHz. The Q value of a single neurone with best frequencies between 60-76 and 61-75 kHz is 210189. If the assumption that the CM is directly related to the mechanical motion of the basilar membrane is correct, the very sharp tuning curves of single neurones at about 61 kHz could be simply due to the mechanical tuning of the basilar membrane. Since this animal predominantly uses a 61 kHz sound for echolocation and peripheral auditory neurones show a low threshold and extremely sharp tuning at about 61 kHz, its peripheral auditory system is specialized for the reception and fine-frequency analysis of the principle component of orientation sounds and echoes. Sharply tuned neurones can code a frequency modulation as small as o-oi%, so that the wing beat of an insect would be easily coded by them. Unlike the CM, N x is tuned at 64 kHz. This difference in best frequency is simply due to the properties of a sharply tuned resonator and N lt and not due to a mechanism comparable to lateral inhibition.

Science, Oct 29, 1976

The extent of cortical representation of the peripheral sensory field depends on its importance f... more The extent of cortical representation of the peripheral sensory field depends on its importance for species behavior. The orientation sound of the mustache bat (Pteronotus parnellii rubiginosus) invariably consists of long constant-frequency and short frequency-modulated components and is indispensable for its survival. A disproportionately large part of the auditory cortex of this bat is occupied by neurons processing the predominant components in the orientation signal and Doppler-shifted echoes. This disproportionate cortical representation related to features of biologically significant signals is comparable to that in the somatosensory and visual systems in many mammals, but it has not previously been observed in the auditory system.

Chinese Science Bulletin, May 1, 2001

In order to explore the possible mechanism of corticofugal modulation of excitatory frequency tun... more In order to explore the possible mechanism of corticofugal modulation of excitatory frequency tuning curves (EFTCs) of midbrain neurons, we examined the change of sharpness, frequency-intensity response area, minimum threshold of both EFTCs and inhibitory frequency tuning curves (IFTCs) of inferior collicular neurons during corticofugal modulation using two-tone inhibition paradigm and micro-electrical stimulation technique. Our data showed that corticofugal inhibition increased sharpness, minimum threshold, and decreased the frequency-intensity response area of EFTCs, at the same time it decreased the sharpness, minimum threshold but increased the frequency-intensity response area of IFTCs. The opposite results were observed for EFTCs and IFTCs of corticofugally facilitated inferior collicular neurons. During corticofugal inhibition, the percent change of frequency-intensity response area of EFTCs had significant correlation with the percent change of that of IFTCs. These data suggest that cortical neurons are likely to improve frequency information processing of inferior collicular neurons by modulation of IFTCs.