The auditory cortex of the bat : Localization and organization of basic response properties-1

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.<p><b>Copyright information:</b></p><p>Taken from "The auditory cortex of the bat : Localization and organization of basic response properties"</p><p>http://www.biomedcentral.com/1471-2202/9/65</p><p>BMC Neuroscience 2008;9():65-65.</p><p>Published online 14 Jul 2008</p><p>PMCID:PMC2483289.</p><p></p

The auditory cortex of the bat : Localization and organization of basic response properties-3

Superimposed black outlines are neuroanatomically determined borders. Solid black lines represent reliable borders, whereas stippled black lines represent more variable borders. Rostro-caudal positions of frontal sections shown in Fig. 2 are indicated by the white vertical lines. Colored lines represent equal medio-lateral distances from the midline in 1000 μm steps as shown in the flattened cortical surface projection in 1B. B) Projection of recording sites (black crosses) and neuroanatomical borders (black lines) on an unrolled and flattened cortical surface. Lateral distances on the cortical surface are indicated in 1000 μm steps by corresponding colors as in the side view (1A). The origin used for the flattening process was fixed at 2000 μm lateral from the midline of the brain (upper dark blue line). C) Schematic of the auditory cortical subfields: anterior dorsal field (ADF), posterior dorsal field (PDF), anterior ventral field (AVF) and posterior ventral field (PVF) with dorsal (PVFd), ventral (PVFv) parts and a border zone (bz) reconstructed on the flattened cortical surface. The neuroanatomically determined borders are indicated by black lines.<p><b>Copyright information:</b></p><p>Taken from "The auditory cortex of the bat : Localization and organization of basic response properties"</p><p>http://www.biomedcentral.com/1471-2202/9/65</p><p>BMC Neuroscience 2008;9():65-65.</p><p>Published online 14 Jul 2008</p><p>PMCID:PMC2483289.</p><p></p

The auditory cortex of the bat : Localization and organization of basic response properties-2

Hs to the right. Indications of layers in the Nissl-stained sections apply to the neighboring left (zinc-stained) and right (myelin-stained) sections, respectively. White arrowheads in the zinc-stained sections indicate the borders of layer IV. Stars in the cut-out of the zinc-stained section of ADF highlight the two components of layer V. The scale bar of 250 μm applies to all cutouts. Abbreviations as in Fig. 1C.<p><b>Copyright information:</b></p><p>Taken from "The auditory cortex of the bat : Localization and organization of basic response properties"</p><p>http://www.biomedcentral.com/1471-2202/9/65</p><p>BMC Neuroscience 2008;9():65-65.</p><p>Published online 14 Jul 2008</p><p>PMCID:PMC2483289.</p><p></p

The auditory cortex of the bat : Localization and organization of basic response properties-0

Superimposed black outlines are neuroanatomically determined borders. Solid black lines represent reliable borders, whereas stippled black lines represent more variable borders. Rostro-caudal positions of frontal sections shown in Fig. 2 are indicated by the white vertical lines. Colored lines represent equal medio-lateral distances from the midline in 1000 μm steps as shown in the flattened cortical surface projection in 1B. B) Projection of recording sites (black crosses) and neuroanatomical borders (black lines) on an unrolled and flattened cortical surface. Lateral distances on the cortical surface are indicated in 1000 μm steps by corresponding colors as in the side view (1A). The origin used for the flattening process was fixed at 2000 μm lateral from the midline of the brain (upper dark blue line). C) Schematic of the auditory cortical subfields: anterior dorsal field (ADF), posterior dorsal field (PDF), anterior ventral field (AVF) and posterior ventral field (PVF) with dorsal (PVFd), ventral (PVFv) parts and a border zone (bz) reconstructed on the flattened cortical surface. The neuroanatomically determined borders are indicated by black lines.<p><b>Copyright information:</b></p><p>Taken from "The auditory cortex of the bat : Localization and organization of basic response properties"</p><p>http://www.biomedcentral.com/1471-2202/9/65</p><p>BMC Neuroscience 2008;9():65-65.</p><p>Published online 14 Jul 2008</p><p>PMCID:PMC2483289.</p><p></p

Location of Recording Sites in the Auditory Cortex of P. discolor

<p>The limits of the two scatter plots (B and C) are superimposed on the photograph of the P. discolor brain (A) (box). The scatter plots show the recording sites for units tested with objects 1 (B) and 2 (C). Units selective for scaled versions of an object (shown as filled red circles) were absent in the most anterior region of auditory cortex.</p

Stimuli Used for the Psychophysical and Electrophysiological Experiments

<p>(A) Impulse responses, (B) waveforms of the echo after convolution of an echolocation call with the IR, and (C) magnitude spectra of the echoes of object 1 and object 2 (left and right column, respectively). In the psychophysical experiments, the bats were trained to discriminate echoes of the standard objects shown the third row of A (scaling factor [Scf] 1). Once the bats had learned this task, presentations of scaled objects (scaling factors 0.67, 0.8, 1.25, and 1.5) were interspersed, and the spontaneous classification of these scaled objects was assessed. For the electrophysiological experiments, the IRs of the standard objects were scaled in terms of the delay and amplitude of the reflections with the same scaling factors and convolved with an echolocation call. The resulting 5 × 5 stimulus matrix is shown in (D). In this matrix the object-surface area and object depth vary along the vertical and the horizontal dimension, respectively. The red squares mark the properly scaled versions of the objects which are shown in (A–C). The physical parameters that changed in the vertical and horizontal dimension were amplitude and echo duration. Note, that all stimuli had very similar magnitude spectra. (E) Spectrogram of the echolocation call of P. discolor used for convolution with the IRs.</p

Influence of Overall Presentation Level on Responses of Cortical Units

<div><p>(A) The unit shown in the figure responded best to properly scaled versions of object 2 (diagonal axis) only at an adequate range of presentation levels.</p> <p>(B) A 10-dB change in the overall presentation level pushed the stimuli out of the range the unit was sensitive to. The overall presentation level is indicated above each panel. Abscissa: normalized object depth. Ordinate: normalized surface area.</p> <p>maxSp, maximum number of spikes.</p></div

Putative Performance of Single Units in the Psychophysical Paradigm

<div><p>(A and B) show the rate responses of a unit to all versions of both standard objects. This unit responded best to scaled versions of object 2. Responses to object 1 were assigned to the “depth” category.</p> <p>(C and D) show the results of a simulation of both the behavioral discrimination and classification based on the rate responses of this cortical unit. The unit was not only able to respond best selectively to scaled versions of object 2, but also to discriminate the two objects and assign most responses to scaled versions of both objects to the correct standard.</p></div

Responses of Cortical Units to Virtual Echo-Acoustic Objects

<div><p>(A and B) Normalized responses of units that responded best to a particular object depth (“depth” category). These units were largely insensitive to changes of object surface area.</p> <p>(C and D) Responses of units which encoded object surface area (“surface”-category). These units were largely insensitive to changes of object depth.</p> <p>The plots are arranged in the same way as the 5 × 5 stimulus matrix shown in <a href="http://www.plosbiology.org/article/info:doi/10.1371/journal.pbio.0050100#pbio-0050100-g001" target="_blank">Figure 1</a>D. Abscissa: normalized object depth. Ordinate: normalized object surface area. MaxSp, maximum number of spikes; this number was taken as the divisor for the normalization of the responses.</p></div

Psychophysical Classification Performance and Simulation Results

<p>Spontaneous classification of scaled virtual objects by three bats (A–C) and a simulation (D) based on a spectrotemporal pattern recognizer. Significantly correct classification of scaled objects is marked by a single star (<i>p</i> < 0.05) or two stars (<i>p</i> < 0.01). The number of test trials for each condition is superimposed on each bar. Although the spectrotemporal pattern recognizer cannot classify the scaled objects correctly, the bats' performance is in the majority of test conditions significantly better.</p