Binaural and frequency representation in the primary auditory cortex of the big brown bat, Eptesicus fuscus

1997 ◽  
Vol 181 (6) ◽  
pp. 591-597 ◽  
Author(s):  
J. X. Shen ◽  
Q. C. Chen ◽  
P. H.-S. Jen
Keyword(s):  
Auditory Cortex ◽  
Primary Auditory Cortex ◽  
Eptesicus Fuscus ◽  
Frequency Representation ◽  
Big Brown Bat

Frequency and amplitude representations in anterior primary auditory cortex of the mustached bat

1983 ◽  
Vol 50 (5) ◽  
pp. 1182-1196 ◽  
Author(s):  
A. Asanuma ◽  
D. Wong ◽  
N. Suga
Keyword(s):  
Auditory Cortex ◽  
Second Harmonic ◽  
Free Field ◽  
Primary Auditory Cortex ◽  
Frequency Component ◽  
Constant Frequency ◽  
Mustached Bat ◽  
Pteronotus Parnellii ◽  
Frequency Representation ◽  
Pure Tones

The orientation sound emitted by the Panamanian mustached bat, Pteronotus parnellii rubiginosus, consists of four harmonics. The third harmonic is 6-12 dB weaker than the predominant second harmonic and consists of a long constant-frequency component (CF3) at about 92 kHz and a short frequency-modulated component (FM3) sweeping from about 92 to 74 kHz. Our primary aim is to examine how CF3 and FM3 are represented in a region of the primary auditory cortex anterior to the Doppler-shifted constant-frequency (DSCF) area. Extracellular recordings of neuronal responses from the unanesthetized animal were obtained during free-field stimulation of the ears with pure tones. FM sounds, and signals simulating their orientation sounds and echoes. Response properties of neurons and tonotopic and amplitopic representations were examined in the primary and the anteroventral nonprimary auditory cortex. In the anterior primary auditory cortex, neurons responded strongly to single pure tones but showed no facilitative responses to paired stimuli. Neurons with best frequencies from 110 to 90 kHz were tonotopically organized rostrocaudally, with higher frequencies located more rostrally. Neurons tuned to 92-94 kHz were overpresented, whereas neurons tuned to sound between 64 and 91 kHz were rarely found. Consequently a striking discontinuity in frequency representation from 91 to 64 kHz was found across the anterior DSCF border. Most neurons exhibited monotonic impulse-count functions and responded maximally to sound pressure level (SPL). There were also neurons that responded best to weak sounds but unlike the DSCF area, amplitopic representation was not found. Thus, the DSCF area is quite unique not only in its extensive representation of frequencies in the second harmonic CF component but also in its amplitopic representation. The anteroventral nonprimary auditory cortex consisted of neurons broadly tuned to pure tones between 88 and 99 kHz. Neither tonotopic nor amplitopic representation was observed. Caudal to this area and near the anteroventral border of the DSCF area, a small cluster of FM-FM neurons sensitive to particular echo delays was identified. The responses of these neurons fluctuated significantly during repetitive stimulation.

Reorganization of the Frequency Map of the Auditory Cortex Evoked by Cortical Electrical Stimulation in the Big Brown Bat

2000 ◽  
Vol 83 (4) ◽  
pp. 1856-1863 ◽  
Author(s):  
Syed A. Chowdhury ◽  
Nobuo Suga
Keyword(s):  
Electrical Stimulation ◽  
Auditory Cortex ◽  
Cortical Neurons ◽  
Frequency Tuning ◽  
Acoustic Stimulus ◽  
Primary Auditory Cortex ◽  
Neural Representation ◽  
Tuning Curves ◽  
Big Brown Bat ◽  
Frequency Map

In a search phase of echolocation, big brown bats, Eptesicus fuscus, emit biosonar pulses at a rate of 10/s and listen to echoes. When a short acoustic stimulus was repetitively delivered at this rate, the reorganization of the frequency map of the primary auditory cortex took place at and around the neurons tuned to the frequency of the acoustic stimulus. Such reorganization became larger when the acoustic stimulus was paired with electrical stimulation of the cortical neurons tuned to the frequency of the acoustic stimulus. This reorganization was mainly due to the decrease in the best frequencies of the neurons that had best frequencies slightly higher than those of the electrically stimulated cortical neurons or the frequency of the acoustic stimulus. Neurons with best frequencies slightly lower than those of the acoustically and/or electrically stimulated neurons slightly increased their best frequencies. These changes resulted in the over-representation of repetitively delivered acoustic stimulus. Because the over-representation resulted in under-representation of other frequencies, the changes increased the contrast of the neural representation of the acoustic stimulus. Best frequency shifts for over-representation were associated with sharpening of frequency-tuning curves of 25% of the neurons studied. Because of the increases in both the contrast of neural representation and the sharpness of tuning, the over-representation of the acoustic stimulus is accompanied with an improvement of analysis of the acoustic stimulus.

Cytoarchitecture and Sound Activated Responses in the Auditory Cortex of the Big Brown Bat,Eptesicus fuscus

1997 ◽  
Vol 117 (sup532) ◽  
pp. 61-67 ◽  
Author(s):  
Philip H.S. Jen ◽  
Xinde Sun ◽  
Jun-Xian Shen ◽  
Qi-Cai Chen ◽  
Ying Qian
Keyword(s):  
Auditory Cortex ◽  
Eptesicus Fuscus ◽  
Big Brown Bat

Corticofugal Modulation of Multi-Parametric Auditory Selectivity in the Midbrain of the Big Brown Bat

2007 ◽  
Vol 98 (5) ◽  
pp. 2509-2516 ◽  
Author(s):  
Xiaoming Zhou ◽  
Philip H.-S. Jen
Keyword(s):  
Electrical Stimulation ◽  
Auditory Cortex ◽  
Inferior Colliculus ◽  
Cortical Neuron ◽  
Cortical Neurons ◽  
Eptesicus Fuscus ◽  
Big Brown Bat ◽  
Cortical Electrical Stimulation ◽  
The Difference ◽  
Corticofugal Modulation

Corticofugal modulation of sub-cortical auditory selectivity has been shown previously in mammals for frequency, amplitude, time, and direction domains in separate studies. As such, these studies do not show if multi-parametric corticofugal modulation can be mediated through the same sub-cortical neuron. Here we specifically studied corticofugal modulation of best frequency (BF), best amplitude (BA), and best azimuth (BAZ) at the same neuron in the inferior colliculus of the big brown bat, Eptesicus fuscus, using focal electrical stimulation in the auditory cortex. Among 53 corticofugally inhibited collicular neurons examined, cortical electrical stimulation produced a shift of all three measurements (i.e., BF, BA, and BAZ) toward the value of stimulated cortical neuron in 13 (24.5%) neurons, two measurements (i.e., BF and BAZ or BA and BAZ) in 19 (36%) neurons, and one measurement in 16 (30%) neurons. Cortical electrical stimulation did not shift any of these measurements in the remaining five (9.5%) neurons. Corticofugally induced collicular BF shift was symmetrical, whereas the shift in collicular BA or BAZ was asymmetrical. The amount of shift in each measurement was significantly correlated with each measurement difference between recorded collicular and stimulated cortical neurons. However, shifts of three measurements were not correlated with each other. Furthermore, average measurement difference between collicular and cortical neurons was larger for collicular neurons with measurement shifts than for those without shifts. These data indicate that multi-parametric corticofugal modulation can be mediated through the same subcortical neuron based on the difference in auditory selectivity between subcortical and cortical neurons.

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