Speculations on the Role of Frequency in Sound Localization

Fuzessery, Zoltan M.

doi:10.1159/000118695

Cited by 21 publications

(16 citation statements)

References 30 publications

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“…DSCFd neurons are mostly I-E neurons (23) and are tuned to strong sounds (19,20) originating from Ϸ30°on the contralateral side (30), whereas DSCFv neurons are mostly E-E neurons (23) and are tuned to weak sounds (19,20) originating from Ϸ0°in front (23). When a weak sound at 61.00 kHz is repetitively delivered to the animal, right DSCFv neurons are mainly excited via the left ear and, presumably, show centrifugal BF shifts.…”

Section: Discussionmentioning

confidence: 99%

Asymmetry in corticofugal modulation of frequency-tuning in mustached bat auditory system

Xiao

Suga

2005

Proc. Natl. Acad. Sci. U.S.A.

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Focal electric stimulation of the auditory cortex is well suited for exploration of the function of the corticofugal (descending) system and the neural mechanism of plasticity in the central auditory system, because it evokes changes in frequency-tuning, called best frequency (BF) shifts, as does auditory fear conditioning. The Doppler-shifted constant frequency (DSCF) area of the primary auditory cortex of the mustached bat is highly specialized for fine frequency analysis. Focal electric stimulation of the DSCF area evokes the BF shifts of ipsilateral cortical and collicular neurons away from the BF of stimulated neurons, whereas the stimulation evokes the BF shifts of contralateral cortical and collicular neurons either toward or away from the stimulated BF. The direction of contralateral BF shifts shows a flip-flop, depending on the spatial relationship between the stimulated and recorded neurons. This asymmetry in corticofugal modulation is mostly, if not totally, created by two subdivisions of the stimulated DSCF area that transmit signals to the contralateral DSCF area, presumably through the corpus callosum. This intriguing asymmetry in corticofugal modulation presumably functions for equalization of the reorganization of the frequency maps of the DSCF areas and subcortical auditory nuclei on both sides. auditory cortex ͉ cochlea ͉ inferior colliculus ͉ inhibition ͉ plasticity A long train of repetitive acoustic stimuli (1-4), repetitive electric stimulation of the primary auditory cortex (AC) (3-6), and auditory fear conditioning (7-9) each evoke plastic changes in frequency-tuning in both the AC and the central nucleus of the inferior colliculus (IC). The shift of a frequency-tuning curve is always accompanied by a best frequency (BF) shift. The collicular BF shift is the same for the conditioning and for cortical electric stimulation (3-4) and does not develop when the AC is inactivated during the conditioning (2, 8). Therefore, the collicular BF shift elicited by the conditioning is due to the corticofugal feedback. Atropine applied to the AC blocks the development of the cortical BF shift elicited by the conditioning but not the collicular BF shift. Therefore, the collicular BF shift does not depend on the cortical BF shift but on corticofugal feedback (9).The cortical and collicular BF shifts evoked by cortical electric stimulation are very similar to those elicited by auditory fear conditioning. A noticeable difference between them is that the cortical BF shift is long-term for the conditioning, but short-term for the electric stimulation (2,8,9). However, the cortical BF shift evoked by the electric stimulation changes from short-term to long-term when acetylcholine is applied to the AC (10). These observations indicate that focal cortical electric stimulation is an appropriate means for the exploration of the cortical and corticofugal function of the plasticity of the central auditory system in the normal adult animal.There are two types of BF shifts: centripetal and centrifugal. Centripetal BF ...

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Section: Discussionmentioning

confidence: 99%

Asymmetry in corticofugal modulation of frequency-tuning in mustached bat auditory system

Xiao

Suga

2005

Proc. Natl. Acad. Sci. U.S.A.

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“…10). Thus, as in subcortical regions Wise and Irvine, 1985;McAlpine et al, 2001, Brand et al, 2002Tollin et al, 2008), the binaural function slope provides the basis for a systematic azimuth-dependent distribution of population firing rates across cortex.…”

Section: A Bicoordinate Localization Code In the Nsrmentioning

confidence: 99%

Mechanisms of Sound Localization in Two Functionally Distinct Regions of the Auditory Cortex

2015

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The auditory cortex is necessary for sound localization. The mechanisms that shape bicoordinate spatial representation in the auditory cortex remain unclear. Here, we addressed this issue by quantifying spatial receptive fields (SRFs) in two functionally distinct cortical regions in the pallid bat. The pallid bat uses echolocation for obstacle avoidance and listens to prey-generated noise to localize prey. Its cortex contains two segregated regions of response selectivity that serve echolocation and localization of prey-generated noise. The main aim of this study was to compare 2D SRFs between neurons in the noise-selective region (NSR) and the echolocation region [frequencymodulated sweep-selective region (FMSR)]. The data reveal the following major differences between these two regions: (1) compared with NSR neurons, SRF properties of FMSR neurons were more strongly dependent on sound level; (2) as a population, NSR neurons represent a broad region of contralateral space, while FMSR selectivity was focused near the midline at sound levels near threshold and expanded considerably with increasing sound levels; and (3) the SRF size and centroid elevation were correlated with the characteristic frequency in the NSR, but not the FMSR. These data suggest different mechanisms of sound localization for two different behaviors. Previously, we reported that azimuth is represented by predictable changes in the extent of activated cortex. The present data indicate how elevation constrains this activity pattern. These data suggest a novel model for bicoordinate spatial representation that is based on the extent of activated cortex resulting from the overlap of binaural and tonotopic maps.

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“…Most bats are specialized for using echolocation, and it is plausible that this specialization may benefit passive localization because the cues used to resolve the location of sound sources are thought to be the same for both reflected and emitted sounds (Fuzessery, 1986;Neuweiler et al, 1980;Pollak et al, 1995;Razak et al, 1999). The auditory nervous systems of echolocating bats are highly derived (although varying greatly among species, e.g., Moss and Sinha, 2003;Casseday et al, 1988;Baron et al, 1996) with specialized mechanisms for capturing insects in flight, obstacle avoidance down to 1 mm or less, and even for detecting fish based on the disturbances on the water's surface (Griffin and Novick, 1955;Grinnell and Griffin, 1958;Schnitzler et al, 1994).…”

Section: Introductionmentioning

confidence: 99%

Sound localization acuity and its relation to vision in large and small fruit-eating bats: II. Non-echolocating species, Eidolon helvum and Cynopterus brachyotis

2008

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Passive sound-localization acuity for 100-msec noise bursts was determined behaviorally for two species of non-echolocating bats: the Straw-colored fruit bat, Eidolon helvum, a large frugivore, and the Dog-faced fruit bat, Cynopterus brachyotis, a small frugivore. The mean minimum audible angle for two E. helvum was 11.7 degrees, and for two C. brachyotis was 10.5 degrees. This places their passive sound-localization acuity near the middle of the range for echolocating bats as well as the middle of the range for other mammals. Sound-localization acuity varies widely among mammals, and the best predictor of this auditory function remains the width of the field of best vision (r=.89, p<.0001). Among echolocating and non-echolocating bats, as well as among other mammals, the use of hearing to direct the eyes to the source of a sound still appears to serve as an important selective factor for sound localization. Absolute visual acuity and the magnitude of the binaural locus cues available to a species remain unreliable predictors of sound-localization acuity.

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Speculations on the Role of Frequency in Sound Localization

Cited by 21 publications

References 30 publications

Asymmetry in corticofugal modulation of frequency-tuning in mustached bat auditory system

Asymmetry in corticofugal modulation of frequency-tuning in mustached bat auditory system

Mechanisms of Sound Localization in Two Functionally Distinct Regions of the Auditory Cortex

Sound localization acuity and its relation to vision in large and small fruit-eating bats: II. Non-echolocating species, Eidolon helvum and Cynopterus brachyotis

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