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Functional transformations of odor inputs in the mouse olfactory bulb.

Adam Y, Livneh Y, Miyamichi K, Groysman M, Luo L, Mizrahi A - Front Neural Circuits (2014)

Bottom Line: Mitral cells population activity was heterogeneous and only mildly correlated with the olfactory receptor neuron (ORN) inputs, supporting the view that discrete input maps undergo significant transformations at the output level of the OB.In contrast, both MCs and GL-INs showed diverse temporal response patterns, suggesting that GL-INs could contribute to the transformations MCs undergo at slow time scales.Our data suggest that sensory odor maps are transformed by TCs and MCs in different ways forming two distinct and parallel information streams.

View Article: PubMed Central - PubMed

Affiliation: Department of Neurobiology, Institute of Life Sciences, The Edmond and Lily Safra Center for Brain Sciences, The Hebrew University of Jerusalem Jerusalem, Israel.

ABSTRACT
Sensory inputs from the nasal epithelium to the olfactory bulb (OB) are organized as a discrete map in the glomerular layer (GL). This map is then modulated by distinct types of local neurons and transmitted to higher brain areas via mitral and tufted cells. Little is known about the functional organization of the circuits downstream of glomeruli. We used in vivo two-photon calcium imaging for large scale functional mapping of distinct neuronal populations in the mouse OB, at single cell resolution. Specifically, we imaged odor responses of mitral cells (MCs), tufted cells (TCs) and glomerular interneurons (GL-INs). Mitral cells population activity was heterogeneous and only mildly correlated with the olfactory receptor neuron (ORN) inputs, supporting the view that discrete input maps undergo significant transformations at the output level of the OB. In contrast, population activity profiles of TCs were dense, and highly correlated with the odor inputs in both space and time. Glomerular interneurons were also highly correlated with the ORN inputs, but showed higher activation thresholds suggesting that these neurons are driven by strongly activated glomeruli. Temporally, upon persistent odor exposure, TCs quickly adapted. In contrast, both MCs and GL-INs showed diverse temporal response patterns, suggesting that GL-INs could contribute to the transformations MCs undergo at slow time scales. Our data suggest that sensory odor maps are transformed by TCs and MCs in different ways forming two distinct and parallel information streams.

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Neurons from the dorsal surface are not activated by distant glomeruli. (A) Intrinsic signal imaging maps showing activation by the panel of odorants used in this study. The borders of a standard chronic imaging window are denoted by the dashed line. Beneath each map we show the dynamics of the intrinsic signal before and during a 4 s stimulus. Signal is the sum intrinsic signal within the dashed line. (B) Same as in (A) but for five “external” odors. Curves in the bottom shows the dynamics of the intrinsic signal within the window (black) and outside the window (dashed). (C) Calcium responses of all responsive neurons that were tested with both “local” and “external” odor sets. Color-code—Peak ΔF/F. Cells in each population are sorted according to the number of activating odorants. Only the responsive cells in each group are presented (total numbers are outlined in the title of each panel). (D) Cumulative graphs of the number of activating odors in each population (responsive cells only). Diamonds—local odors from this dataset, dashed line—local odors in the main dataset (same as Figure 3E), solid line—external odors.
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Figure 5: Neurons from the dorsal surface are not activated by distant glomeruli. (A) Intrinsic signal imaging maps showing activation by the panel of odorants used in this study. The borders of a standard chronic imaging window are denoted by the dashed line. Beneath each map we show the dynamics of the intrinsic signal before and during a 4 s stimulus. Signal is the sum intrinsic signal within the dashed line. (B) Same as in (A) but for five “external” odors. Curves in the bottom shows the dynamics of the intrinsic signal within the window (black) and outside the window (dashed). (C) Calcium responses of all responsive neurons that were tested with both “local” and “external” odor sets. Color-code—Peak ΔF/F. Cells in each population are sorted according to the number of activating odorants. Only the responsive cells in each group are presented (total numbers are outlined in the title of each panel). (D) Cumulative graphs of the number of activating odors in each population (responsive cells only). Diamonds—local odors from this dataset, dashed line—local odors in the main dataset (same as Figure 3E), solid line—external odors.

Mentions: Imaging was performed under ketamine/medetomidine anesthesia (100 mg/kg and 0.83 mg/kg, i.p.). Imaging lasted up to 10 h per session. We assessed the depth of anesthesia by monitoring the pinch withdrawal reflex and added ketamine/medetomidine when needed. We continuously monitored the animal’s rectal temperature and maintained it at 37 ± 1°C. Each OB was imaged several times to collect as many neurons as possible for mapping, usually two consecutive imaging sessions. In some animals we mapped both OBs (i.e., four sessions per animal). To collect the “external” odors dataset (Figure 5), some animals underwent an additional imaging session. Animals were placed under the microscope in a custom-made stereotaxic device via the metal bar and kept in fixed angle relative to the objective.


Functional transformations of odor inputs in the mouse olfactory bulb.

Adam Y, Livneh Y, Miyamichi K, Groysman M, Luo L, Mizrahi A - Front Neural Circuits (2014)

Neurons from the dorsal surface are not activated by distant glomeruli. (A) Intrinsic signal imaging maps showing activation by the panel of odorants used in this study. The borders of a standard chronic imaging window are denoted by the dashed line. Beneath each map we show the dynamics of the intrinsic signal before and during a 4 s stimulus. Signal is the sum intrinsic signal within the dashed line. (B) Same as in (A) but for five “external” odors. Curves in the bottom shows the dynamics of the intrinsic signal within the window (black) and outside the window (dashed). (C) Calcium responses of all responsive neurons that were tested with both “local” and “external” odor sets. Color-code—Peak ΔF/F. Cells in each population are sorted according to the number of activating odorants. Only the responsive cells in each group are presented (total numbers are outlined in the title of each panel). (D) Cumulative graphs of the number of activating odors in each population (responsive cells only). Diamonds—local odors from this dataset, dashed line—local odors in the main dataset (same as Figure 3E), solid line—external odors.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4219419&req=5

Figure 5: Neurons from the dorsal surface are not activated by distant glomeruli. (A) Intrinsic signal imaging maps showing activation by the panel of odorants used in this study. The borders of a standard chronic imaging window are denoted by the dashed line. Beneath each map we show the dynamics of the intrinsic signal before and during a 4 s stimulus. Signal is the sum intrinsic signal within the dashed line. (B) Same as in (A) but for five “external” odors. Curves in the bottom shows the dynamics of the intrinsic signal within the window (black) and outside the window (dashed). (C) Calcium responses of all responsive neurons that were tested with both “local” and “external” odor sets. Color-code—Peak ΔF/F. Cells in each population are sorted according to the number of activating odorants. Only the responsive cells in each group are presented (total numbers are outlined in the title of each panel). (D) Cumulative graphs of the number of activating odors in each population (responsive cells only). Diamonds—local odors from this dataset, dashed line—local odors in the main dataset (same as Figure 3E), solid line—external odors.
Mentions: Imaging was performed under ketamine/medetomidine anesthesia (100 mg/kg and 0.83 mg/kg, i.p.). Imaging lasted up to 10 h per session. We assessed the depth of anesthesia by monitoring the pinch withdrawal reflex and added ketamine/medetomidine when needed. We continuously monitored the animal’s rectal temperature and maintained it at 37 ± 1°C. Each OB was imaged several times to collect as many neurons as possible for mapping, usually two consecutive imaging sessions. In some animals we mapped both OBs (i.e., four sessions per animal). To collect the “external” odors dataset (Figure 5), some animals underwent an additional imaging session. Animals were placed under the microscope in a custom-made stereotaxic device via the metal bar and kept in fixed angle relative to the objective.

Bottom Line: Mitral cells population activity was heterogeneous and only mildly correlated with the olfactory receptor neuron (ORN) inputs, supporting the view that discrete input maps undergo significant transformations at the output level of the OB.In contrast, both MCs and GL-INs showed diverse temporal response patterns, suggesting that GL-INs could contribute to the transformations MCs undergo at slow time scales.Our data suggest that sensory odor maps are transformed by TCs and MCs in different ways forming two distinct and parallel information streams.

View Article: PubMed Central - PubMed

Affiliation: Department of Neurobiology, Institute of Life Sciences, The Edmond and Lily Safra Center for Brain Sciences, The Hebrew University of Jerusalem Jerusalem, Israel.

ABSTRACT
Sensory inputs from the nasal epithelium to the olfactory bulb (OB) are organized as a discrete map in the glomerular layer (GL). This map is then modulated by distinct types of local neurons and transmitted to higher brain areas via mitral and tufted cells. Little is known about the functional organization of the circuits downstream of glomeruli. We used in vivo two-photon calcium imaging for large scale functional mapping of distinct neuronal populations in the mouse OB, at single cell resolution. Specifically, we imaged odor responses of mitral cells (MCs), tufted cells (TCs) and glomerular interneurons (GL-INs). Mitral cells population activity was heterogeneous and only mildly correlated with the olfactory receptor neuron (ORN) inputs, supporting the view that discrete input maps undergo significant transformations at the output level of the OB. In contrast, population activity profiles of TCs were dense, and highly correlated with the odor inputs in both space and time. Glomerular interneurons were also highly correlated with the ORN inputs, but showed higher activation thresholds suggesting that these neurons are driven by strongly activated glomeruli. Temporally, upon persistent odor exposure, TCs quickly adapted. In contrast, both MCs and GL-INs showed diverse temporal response patterns, suggesting that GL-INs could contribute to the transformations MCs undergo at slow time scales. Our data suggest that sensory odor maps are transformed by TCs and MCs in different ways forming two distinct and parallel information streams.

Show MeSH
Related in: MedlinePlus