Limits...
The functional asymmetry of auditory cortex is reflected in the organization of local cortical circuits.

Oviedo HV, Bureau I, Svoboda K, Zador AM - Nat. Neurosci. (2010)

Bottom Line: By contrast, we found that local connections along the tonotopic axis differed from those along the isofrequency axis: some input pathways to L3 (but not L2) arose predominantly out-of-column.In vivo cell-attached recordings revealed differences between the sound-responsiveness of neurons in L2 and L3.Our results are consistent with the hypothesis that auditory cortical microcircuitry is specialized to the one-dimensional representation of frequency in the auditory cortex.

View Article: PubMed Central - PubMed

Affiliation: Cold Spring Harbor Laboratory, Cold Spring Harbor, New York, USA.

ABSTRACT
The primary auditory cortex (A1) is organized tonotopically, with neurons sensitive to high and low frequencies arranged in a rostro-caudal gradient. We used laser scanning photostimulation in acute slices to study the organization of local excitatory connections onto layers 2 and 3 (L2/3) of the mouse A1. Consistent with the organization of other cortical regions, synaptic inputs along the isofrequency axis (orthogonal to the tonotopic axis) arose predominantly within a column. By contrast, we found that local connections along the tonotopic axis differed from those along the isofrequency axis: some input pathways to L3 (but not L2) arose predominantly out-of-column. In vivo cell-attached recordings revealed differences between the sound-responsiveness of neurons in L2 and L3. Our results are consistent with the hypothesis that auditory cortical microcircuitry is specialized to the one-dimensional representation of frequency in the auditory cortex.

Show MeSH
Auditory cortex LSPS experimental preparation(a) Coronal brain slice (cut along the lateral (L) medial (M) axis) containing the primary auditory cortex and underlying subcortical area used for studying the organization along the isofrequency axis. The white box outlines the stimulus grid, and the dashed lines represent the landmarks used to align the grid from animal to animal. For each cell we measured the distance of the soma from the L1/2 border and the middle of the grid. (The ventral and dorsal divisions of the lateral geniculate nucleus (VLG and DLG, respectively) are labeled as landmarks). (b) (left) Stimulus grid showing the 16×16 points of uncaging. (right) Picture of a patched cell filled with Alexa and magnification of a dendritic branch (scale bar is 15 µm). (c) (left) Examples of direct responses, i.e. those evoked by the direct activation of receptors by uncaged glutamate in the neuron under study. (right) Examples of synaptic responses, i.e. EPSCs elicited by triggering action potentials in neurons presynaptic to the neuron under study. The vertical lines through the traces mark the time window to detect direct responses (first 2 vertical lines) and synaptic events (second and third vertical lines).
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC3140463&req=5

Figure 1: Auditory cortex LSPS experimental preparation(a) Coronal brain slice (cut along the lateral (L) medial (M) axis) containing the primary auditory cortex and underlying subcortical area used for studying the organization along the isofrequency axis. The white box outlines the stimulus grid, and the dashed lines represent the landmarks used to align the grid from animal to animal. For each cell we measured the distance of the soma from the L1/2 border and the middle of the grid. (The ventral and dorsal divisions of the lateral geniculate nucleus (VLG and DLG, respectively) are labeled as landmarks). (b) (left) Stimulus grid showing the 16×16 points of uncaging. (right) Picture of a patched cell filled with Alexa and magnification of a dendritic branch (scale bar is 15 µm). (c) (left) Examples of direct responses, i.e. those evoked by the direct activation of receptors by uncaged glutamate in the neuron under study. (right) Examples of synaptic responses, i.e. EPSCs elicited by triggering action potentials in neurons presynaptic to the neuron under study. The vertical lines through the traces mark the time window to detect direct responses (first 2 vertical lines) and synaptic events (second and third vertical lines).

Mentions: We began by studying the input to neurons in L2/3 in a coronal slice that preserves isofrequency bands (Fig. 1a, top), i.e. in a slice containing neurons which respond to similar frequencies 9. The organization of the primary auditory cortex along this axis has recently been characterized in the rat 8, but to assess any species-specific differences in input pattern (as has been shown in the barrel cortex 6 for example), and to provide a baseline for the studies presented here, we repeated these experiments in the mouse.


The functional asymmetry of auditory cortex is reflected in the organization of local cortical circuits.

Oviedo HV, Bureau I, Svoboda K, Zador AM - Nat. Neurosci. (2010)

Auditory cortex LSPS experimental preparation(a) Coronal brain slice (cut along the lateral (L) medial (M) axis) containing the primary auditory cortex and underlying subcortical area used for studying the organization along the isofrequency axis. The white box outlines the stimulus grid, and the dashed lines represent the landmarks used to align the grid from animal to animal. For each cell we measured the distance of the soma from the L1/2 border and the middle of the grid. (The ventral and dorsal divisions of the lateral geniculate nucleus (VLG and DLG, respectively) are labeled as landmarks). (b) (left) Stimulus grid showing the 16×16 points of uncaging. (right) Picture of a patched cell filled with Alexa and magnification of a dendritic branch (scale bar is 15 µm). (c) (left) Examples of direct responses, i.e. those evoked by the direct activation of receptors by uncaged glutamate in the neuron under study. (right) Examples of synaptic responses, i.e. EPSCs elicited by triggering action potentials in neurons presynaptic to the neuron under study. The vertical lines through the traces mark the time window to detect direct responses (first 2 vertical lines) and synaptic events (second and third vertical lines).
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3140463&req=5

Figure 1: Auditory cortex LSPS experimental preparation(a) Coronal brain slice (cut along the lateral (L) medial (M) axis) containing the primary auditory cortex and underlying subcortical area used for studying the organization along the isofrequency axis. The white box outlines the stimulus grid, and the dashed lines represent the landmarks used to align the grid from animal to animal. For each cell we measured the distance of the soma from the L1/2 border and the middle of the grid. (The ventral and dorsal divisions of the lateral geniculate nucleus (VLG and DLG, respectively) are labeled as landmarks). (b) (left) Stimulus grid showing the 16×16 points of uncaging. (right) Picture of a patched cell filled with Alexa and magnification of a dendritic branch (scale bar is 15 µm). (c) (left) Examples of direct responses, i.e. those evoked by the direct activation of receptors by uncaged glutamate in the neuron under study. (right) Examples of synaptic responses, i.e. EPSCs elicited by triggering action potentials in neurons presynaptic to the neuron under study. The vertical lines through the traces mark the time window to detect direct responses (first 2 vertical lines) and synaptic events (second and third vertical lines).
Mentions: We began by studying the input to neurons in L2/3 in a coronal slice that preserves isofrequency bands (Fig. 1a, top), i.e. in a slice containing neurons which respond to similar frequencies 9. The organization of the primary auditory cortex along this axis has recently been characterized in the rat 8, but to assess any species-specific differences in input pattern (as has been shown in the barrel cortex 6 for example), and to provide a baseline for the studies presented here, we repeated these experiments in the mouse.

Bottom Line: By contrast, we found that local connections along the tonotopic axis differed from those along the isofrequency axis: some input pathways to L3 (but not L2) arose predominantly out-of-column.In vivo cell-attached recordings revealed differences between the sound-responsiveness of neurons in L2 and L3.Our results are consistent with the hypothesis that auditory cortical microcircuitry is specialized to the one-dimensional representation of frequency in the auditory cortex.

View Article: PubMed Central - PubMed

Affiliation: Cold Spring Harbor Laboratory, Cold Spring Harbor, New York, USA.

ABSTRACT
The primary auditory cortex (A1) is organized tonotopically, with neurons sensitive to high and low frequencies arranged in a rostro-caudal gradient. We used laser scanning photostimulation in acute slices to study the organization of local excitatory connections onto layers 2 and 3 (L2/3) of the mouse A1. Consistent with the organization of other cortical regions, synaptic inputs along the isofrequency axis (orthogonal to the tonotopic axis) arose predominantly within a column. By contrast, we found that local connections along the tonotopic axis differed from those along the isofrequency axis: some input pathways to L3 (but not L2) arose predominantly out-of-column. In vivo cell-attached recordings revealed differences between the sound-responsiveness of neurons in L2 and L3. Our results are consistent with the hypothesis that auditory cortical microcircuitry is specialized to the one-dimensional representation of frequency in the auditory cortex.

Show MeSH