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The auditory cortex of the bat Phyllostomus discolor: Localization and organization of basic response properties.

Hoffmann S, Firzlaff U, Radtke-Schuller S, Schwellnus B, Schuller G - BMC Neurosci (2008)

Bottom Line: The auditory cortex of P. discolor resembles the auditory cortex of other phyllostomid bats in size and basic functional organization.The tonotopically organized posterior ventral field might represent the primary auditory cortex and the tonotopically organized anterior ventral field seems to be similar to the anterior auditory field of other mammals.As most energy of the echolocation pulse of P. discolor is contained in the high-frequency range, the non-tonotopically organized high-frequency dorsal region seems to be particularly important for echolocation.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department Biology II, Ludwig-Maximilians-University Munich, Grosshaderner Strasse 2, 82152 Planegg-Martinsried, Germany. hoffmann@zi.biologie.uni-muenchen.de

ABSTRACT

Background: The mammalian auditory cortex can be subdivided into various fields characterized by neurophysiological and neuroarchitectural properties and by connections with different nuclei of the thalamus. Besides the primary auditory cortex, echolocating bats have cortical fields for the processing of temporal and spectral features of the echolocation pulses. This paper reports on location, neuroarchitecture and basic functional organization of the auditory cortex of the microchiropteran bat Phyllostomus discolor (family: Phyllostomidae).

Results: The auditory cortical area of P. discolor is located at parieto-temporal portions of the neocortex. It covers a rostro-caudal range of about 4800 mum and a medio-lateral distance of about 7000 mum on the flattened cortical surface. The auditory cortices of ten adult P. discolor were electrophysiologically mapped in detail. Responses of 849 units (single neurons and neuronal clusters up to three neurons) to pure tone stimulation were recorded extracellularly. Cortical units were characterized and classified depending on their response properties such as best frequency, auditory threshold, first spike latency, response duration, width and shape of the frequency response area and binaural interactions. Based on neurophysiological and neuroanatomical criteria, the auditory cortex of P. discolor could be subdivided into anterior and posterior ventral fields and anterior and posterior dorsal fields. The representation of response properties within the different auditory cortical fields was analyzed in detail. The two ventral fields were distinguished by their tonotopic organization with opposing frequency gradients. The dorsal cortical fields were not tonotopically organized but contained neurons that were responsive to high frequencies only.

Conclusion: The auditory cortex of P. discolor resembles the auditory cortex of other phyllostomid bats in size and basic functional organization. The tonotopically organized posterior ventral field might represent the primary auditory cortex and the tonotopically organized anterior ventral field seems to be similar to the anterior auditory field of other mammals. As most energy of the echolocation pulse of P. discolor is contained in the high-frequency range, the non-tonotopically organized high-frequency dorsal region seems to be particularly important for echolocation.

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Distribution of response properties of cortical units and examples of PSTHs for different response types. The frequency distribution of neuronal response properties evoked by pure tone stimulation is shown for: A) Best frequency, B) Response threshold, D) First spike latency, E) Response duration and G) Q10dB values. Peri-stimulus time histograms (PSTHs) show examples of cortical units with different response types: C) phasic response, F) phasic response with a sustained component and I) tonic response. The binwidth of the histograms is 1 ms. The grey bar represents the acoustic stimulus (20 ms pure tone). Panel H) shows the Q10dB values as a function of best frequency. The regression line is shown in red.
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Figure 4: Distribution of response properties of cortical units and examples of PSTHs for different response types. The frequency distribution of neuronal response properties evoked by pure tone stimulation is shown for: A) Best frequency, B) Response threshold, D) First spike latency, E) Response duration and G) Q10dB values. Peri-stimulus time histograms (PSTHs) show examples of cortical units with different response types: C) phasic response, F) phasic response with a sustained component and I) tonic response. The binwidth of the histograms is 1 ms. The grey bar represents the acoustic stimulus (20 ms pure tone). Panel H) shows the Q10dB values as a function of best frequency. The regression line is shown in red.

Mentions: As shown in Fig. 4A, BFs of units ranged from five to 107 kHz (n = 849; median: 60 kHz; interquartile range: 44 to 67 kHz). Seventy nine percent of the units (674 of 849) had BFs above 40 kHz, i.e. in the range of the dominant harmonics of the echolocation pulse of P. discolor.


The auditory cortex of the bat Phyllostomus discolor: Localization and organization of basic response properties.

Hoffmann S, Firzlaff U, Radtke-Schuller S, Schwellnus B, Schuller G - BMC Neurosci (2008)

Distribution of response properties of cortical units and examples of PSTHs for different response types. The frequency distribution of neuronal response properties evoked by pure tone stimulation is shown for: A) Best frequency, B) Response threshold, D) First spike latency, E) Response duration and G) Q10dB values. Peri-stimulus time histograms (PSTHs) show examples of cortical units with different response types: C) phasic response, F) phasic response with a sustained component and I) tonic response. The binwidth of the histograms is 1 ms. The grey bar represents the acoustic stimulus (20 ms pure tone). Panel H) shows the Q10dB values as a function of best frequency. The regression line is shown in red.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2483289&req=5

Figure 4: Distribution of response properties of cortical units and examples of PSTHs for different response types. The frequency distribution of neuronal response properties evoked by pure tone stimulation is shown for: A) Best frequency, B) Response threshold, D) First spike latency, E) Response duration and G) Q10dB values. Peri-stimulus time histograms (PSTHs) show examples of cortical units with different response types: C) phasic response, F) phasic response with a sustained component and I) tonic response. The binwidth of the histograms is 1 ms. The grey bar represents the acoustic stimulus (20 ms pure tone). Panel H) shows the Q10dB values as a function of best frequency. The regression line is shown in red.
Mentions: As shown in Fig. 4A, BFs of units ranged from five to 107 kHz (n = 849; median: 60 kHz; interquartile range: 44 to 67 kHz). Seventy nine percent of the units (674 of 849) had BFs above 40 kHz, i.e. in the range of the dominant harmonics of the echolocation pulse of P. discolor.

Bottom Line: The auditory cortex of P. discolor resembles the auditory cortex of other phyllostomid bats in size and basic functional organization.The tonotopically organized posterior ventral field might represent the primary auditory cortex and the tonotopically organized anterior ventral field seems to be similar to the anterior auditory field of other mammals.As most energy of the echolocation pulse of P. discolor is contained in the high-frequency range, the non-tonotopically organized high-frequency dorsal region seems to be particularly important for echolocation.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department Biology II, Ludwig-Maximilians-University Munich, Grosshaderner Strasse 2, 82152 Planegg-Martinsried, Germany. hoffmann@zi.biologie.uni-muenchen.de

ABSTRACT

Background: The mammalian auditory cortex can be subdivided into various fields characterized by neurophysiological and neuroarchitectural properties and by connections with different nuclei of the thalamus. Besides the primary auditory cortex, echolocating bats have cortical fields for the processing of temporal and spectral features of the echolocation pulses. This paper reports on location, neuroarchitecture and basic functional organization of the auditory cortex of the microchiropteran bat Phyllostomus discolor (family: Phyllostomidae).

Results: The auditory cortical area of P. discolor is located at parieto-temporal portions of the neocortex. It covers a rostro-caudal range of about 4800 mum and a medio-lateral distance of about 7000 mum on the flattened cortical surface. The auditory cortices of ten adult P. discolor were electrophysiologically mapped in detail. Responses of 849 units (single neurons and neuronal clusters up to three neurons) to pure tone stimulation were recorded extracellularly. Cortical units were characterized and classified depending on their response properties such as best frequency, auditory threshold, first spike latency, response duration, width and shape of the frequency response area and binaural interactions. Based on neurophysiological and neuroanatomical criteria, the auditory cortex of P. discolor could be subdivided into anterior and posterior ventral fields and anterior and posterior dorsal fields. The representation of response properties within the different auditory cortical fields was analyzed in detail. The two ventral fields were distinguished by their tonotopic organization with opposing frequency gradients. The dorsal cortical fields were not tonotopically organized but contained neurons that were responsive to high frequencies only.

Conclusion: The auditory cortex of P. discolor resembles the auditory cortex of other phyllostomid bats in size and basic functional organization. The tonotopically organized posterior ventral field might represent the primary auditory cortex and the tonotopically organized anterior ventral field seems to be similar to the anterior auditory field of other mammals. As most energy of the echolocation pulse of P. discolor is contained in the high-frequency range, the non-tonotopically organized high-frequency dorsal region seems to be particularly important for echolocation.

Show MeSH
Related in: MedlinePlus