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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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Frontal sections at two rostro-caudal levels. The frontal sections are shown for position indicated by the vertical lines in Fig. 1A. Top row: sections (40 μm thick) stained for cells (Nissl); middle row: neighboring sections stained for myelin; bottom row: sections stained for zinc at comparable rostro-caudal level from another series. Scalebar: 2000 μm. Abbreviations as in Fig. 1C.
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Figure 2: Frontal sections at two rostro-caudal levels. The frontal sections are shown for position indicated by the vertical lines in Fig. 1A. Top row: sections (40 μm thick) stained for cells (Nissl); middle row: neighboring sections stained for myelin; bottom row: sections stained for zinc at comparable rostro-caudal level from another series. Scalebar: 2000 μm. Abbreviations as in Fig. 1C.

Mentions: Frontal sections in Fig. 2 give showcase characteristics at two rostro-caudal levels (as indicated in Fig. 1A) to get a general idea of field differences. Total cortical thickness, relative thickness of the different layers, composition of cell types, cell density, content of myelinated fibers and zinc are considered as parameters for the distinction of the different fields. Cut-outs of frontal sections stained for cells (Nissl), myelinated fibers (Gallyas) and for zinc (sulphide/silver histochemical method) from the centers of the different cortical fields are mounted in Fig. 3 for detailed comparison.


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)

Frontal sections at two rostro-caudal levels. The frontal sections are shown for position indicated by the vertical lines in Fig. 1A. Top row: sections (40 μm thick) stained for cells (Nissl); middle row: neighboring sections stained for myelin; bottom row: sections stained for zinc at comparable rostro-caudal level from another series. Scalebar: 2000 μm. Abbreviations as in Fig. 1C.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 2: Frontal sections at two rostro-caudal levels. The frontal sections are shown for position indicated by the vertical lines in Fig. 1A. Top row: sections (40 μm thick) stained for cells (Nissl); middle row: neighboring sections stained for myelin; bottom row: sections stained for zinc at comparable rostro-caudal level from another series. Scalebar: 2000 μm. Abbreviations as in Fig. 1C.
Mentions: Frontal sections in Fig. 2 give showcase characteristics at two rostro-caudal levels (as indicated in Fig. 1A) to get a general idea of field differences. Total cortical thickness, relative thickness of the different layers, composition of cell types, cell density, content of myelinated fibers and zinc are considered as parameters for the distinction of the different fields. Cut-outs of frontal sections stained for cells (Nissl), myelinated fibers (Gallyas) and for zinc (sulphide/silver histochemical method) from the centers of the different cortical fields are mounted in Fig. 3 for detailed comparison.

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