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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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Spatial representation of FRA types and binaural response types and distribution in different cortical subfields. Spatial representation A) and distribution in cortical subfields C) of the different FRA types. V/D mon: monotonically V-shaped/double-tuned; V/D nonmon: non-monotonically V-shaped/double-tuned; circ: circumscribed; comp: complex. Spatial representation B) and distribution in cortical subfields D) of the different binaural response types. EI: Excitatory/inhibitory; EE: Excitatory/excitatory; E0: Excitatory/non-responsive. Abbreviation of field names as in Fig. 1C.
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Figure 7: Spatial representation of FRA types and binaural response types and distribution in different cortical subfields. Spatial representation A) and distribution in cortical subfields C) of the different FRA types. V/D mon: monotonically V-shaped/double-tuned; V/D nonmon: non-monotonically V-shaped/double-tuned; circ: circumscribed; comp: complex. Spatial representation B) and distribution in cortical subfields D) of the different binaural response types. EI: Excitatory/inhibitory; EE: Excitatory/excitatory; E0: Excitatory/non-responsive. Abbreviation of field names as in Fig. 1C.

Mentions: The representation of the different FRA-types showed slight differences between anterior and posterior cortical fields (Fig. 7A). Most units of anterior fields had monotonic V-shaped or monotonic double tuned FRAs (ADF: 54 %; AVF: 52 %), whereas non-monotonic V-shaped and non-monotonic double tuned FRAs were mainly found in posterior fields (PDF: 45 %; PVF: 40 %, Fig. 7C). The cortical representation of double tuned FRAs with harmonically related components did not show a specific clustering within certain subfields.


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)

Spatial representation of FRA types and binaural response types and distribution in different cortical subfields. Spatial representation A) and distribution in cortical subfields C) of the different FRA types. V/D mon: monotonically V-shaped/double-tuned; V/D nonmon: non-monotonically V-shaped/double-tuned; circ: circumscribed; comp: complex. Spatial representation B) and distribution in cortical subfields D) of the different binaural response types. EI: Excitatory/inhibitory; EE: Excitatory/excitatory; E0: Excitatory/non-responsive. Abbreviation of field names as in Fig. 1C.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 7: Spatial representation of FRA types and binaural response types and distribution in different cortical subfields. Spatial representation A) and distribution in cortical subfields C) of the different FRA types. V/D mon: monotonically V-shaped/double-tuned; V/D nonmon: non-monotonically V-shaped/double-tuned; circ: circumscribed; comp: complex. Spatial representation B) and distribution in cortical subfields D) of the different binaural response types. EI: Excitatory/inhibitory; EE: Excitatory/excitatory; E0: Excitatory/non-responsive. Abbreviation of field names as in Fig. 1C.
Mentions: The representation of the different FRA-types showed slight differences between anterior and posterior cortical fields (Fig. 7A). Most units of anterior fields had monotonic V-shaped or monotonic double tuned FRAs (ADF: 54 %; AVF: 52 %), whereas non-monotonic V-shaped and non-monotonic double tuned FRAs were mainly found in posterior fields (PDF: 45 %; PVF: 40 %, Fig. 7C). The cortical representation of double tuned FRAs with harmonically related components did not show a specific clustering within certain subfields.

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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