Comparison of Identified Mitral and Tufted Cells in Freely Breathing Rats: II. Odor-Evoked Responses

Griff, Edwin R.; Mafhouz, Mariam; Chaput, Michel

doi:10.1093/chemse/bjn040

Cited by 28 publications

(37 citation statements)

References 23 publications

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“…The linkages appear to be somewhat tighter in tufted-tufted pairs, which had smaller mean width and lag of narrow peaks in cross-correlograms, significantly correlated firing or bursting patterns, and perhaps stronger mean electrical coupling. In contrast to previous studies of evoked responses of mitral and tufted cells in vivo (Nagayama et al, 2004; Griff et al, 2008), we did not detect significant differences between basal spontaneous firing rates of mitral and tufted cells in slices. Thus, the two cell types may express divergent spike activity only when relaying signals that encode odorant stimuli.…”

Section: Discussioncontrasting

confidence: 99%

“…3 and Table I. Previous studies showed that tufted cells responded more robustly to odorant stimuli in vivo, and they may be under weaker inhibitory control (Griff et al, 2008; Nagayama et al, 2004). We expected to see this reflected in the spike activity in slices.…”

Section: Resultsmentioning

confidence: 89%

“…They also differ in their cortical projections: mitral cells innervate the rostrocaudal extent of olfactory cortex, while tufted cells project to more rostromedial areas (Haberly and Price, 1977; Schoenfeld and Macrides, 1984; Ekstrand et al, 2001; Schneider and Scott, 1983; Scott, 1981). Mitral and tufted cells show differing spike responses to electrical stimulation (Ezeh et al, 1993; Schneider and Scott, 1983) and odorants (Nagayama et al, 2004; Griff et al, 2008). A recent survey of odorant responses of mitral/tufted cells receiving input from the I7 olfactory receptor revealed variation in tuning at higher stimulus concentrations (Tan et al, 2010).…”

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confidence: 99%

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Correlated firing in tufted cells of mouse olfactory bulb

Lowe

2010

Neuroscience

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Temporally correlated spike discharges are proposed to be important for the coding of olfactory stimuli. In the olfactory bulb, correlated spiking is known in two classes of output neurons, the mitral cells and external tufted cells. We studied a third major class of bulb output neurons, the middle tufted cells, analyzing their bursting and spike timing correlations, and their relation to mitral cells. Using patch-clamp and fluorescent tracing, we recorded spontaneous spiking from tufted-tufted or mitral-tufted cell pairs with visualized dendritic projections in mouse olfactory bulb slices. We found peaks in spike cross-correlograms indicating correlated activity on both fast (peak width 1 ms – 50 ms) and slow (peak width > 50 ms) time scales, only in pairs with convergent glomerular projections. Coupling appeared tighter in tufted-tufted pairs, which showed correlated firing patterns and smaller mean width and lag of narrow peaks. Some narrow peaks resolved into 2–3 sub-peaks (width 1–12 ms), indicating multiple modes of fast correlation. Slow correlations were related to bursting activity, while fast correlations were independent of slow correlations, occurring in both bursting and non-bursting cells. The AMPA receptor antagonist NBQX (20 μM) failed to abolish broad or narrow peaks in either tufted-tufted or mitral-tufted pairs, and changes of peak height and width in NBQX were not significantly different from spontaneous drift. Thus, AMPA-receptors are not required for fast and slow spike correlations. Electrical coupling was observed in all convergent tufted-tufted and mitral-tufted pairs tested, suggesting a potential role for gap junctions in concerted firing. Glomerulus-specific correlation of spiking offers a useful mechanism for binding the output signals of diverse neurons processing and transmitting different sensory information encoded by common olfactory receptors.

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Section: Discussioncontrasting

confidence: 99%

Section: Resultsmentioning

confidence: 89%

mentioning

confidence: 99%

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Correlated firing in tufted cells of mouse olfactory bulb

Lowe

2010

Neuroscience

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“…Tufted cells, a cell type that we did not target in the current study, are more abundant than MCs (Shepherd et al, 2004), and could carry information on odor identity. Middle tufted cells respond to odors and local processing of the odorant signal in the middle tufted cells differs from that in MCs (Griff et al, 2008; Nagayama et al, 2004). In addition, external tufted cells whose cell bodies lie adjacent to glomeruli could transmit information on odor identity (Wachowiak and Shipley, 2006), although whether these cells can carry information to higher order centers has not been fully explored (Schoenfeld and Macrides, 1984; Schoenfeld et al, 1985).…”

Section: Discussionmentioning

confidence: 98%

Associative Cortex Features in the First Olfactory Brain Relay Station

Doucette

Gire

Whitesell

et al. 2011

Neuron

152

174

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Summary Synchronized firing of mitral cells (MCs) in the olfactory bulb (OB) has been hypothesized to help bind information together in olfactory cortex (OC). In this first survey of synchronized firing by suspected MCs in awake-behaving vertebrates we find the surprising result that synchronized firing conveys information on odor value (is it rewarded?) rather than odor identity (what is the odor?). We observed that as mice learned to discriminate between odors synchronous firing responses to the rewarded and unrewarded odors became divergent. Further, adrenergic blockage decreases the magnitude of odor divergence of synchronous trains suggesting that MCs contribute to decision-making through adrenergic-modulated synchronized firing. Thus, in the olfactory system information on stimulus reward is found in MCs one synapse away from the sensory neuron.

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“…One explanation for this result may be that the AON receives input preferentially from OB tufted (as opposed to mitral) cells (Haberly and Price, 1977; Scott et al, 1980; Scott, 1981; Macrides and Schneider, 1982; Nagayama et al, 2010; Sosulski et al, 2011). Functionally, tufted cells are more excitable, have higher firing frequencies and display stronger respiratory locking compared to mitral cells (Schneider and Scott, 1983; Ezeh et al, 1993; Nagayama et al, 2004; Griff et al, 2008; Burton and Urban, 2014) and so may preserve the timing of odor sampling more faithfully across their population. Inhalation-coupled feedback from AON may play several roles in shaping how the OB processes incoming olfactory information.…”

Section: Discussionmentioning

confidence: 99%

Functional imaging of cortical feedback projections to the olfactory bulb

Rothermel

Wachowiak

2014

Front. Neural Circuits

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Processing of sensory information is substantially shaped by centrifugal, or feedback, projections from higher cortical areas, yet the functional properties of these projections are poorly characterized. Here, we used genetically-encoded calcium sensors (GCaMPs) to functionally image activation of centrifugal projections targeting the olfactory bulb (OB). The OB receives massive centrifugal input from cortical areas but there has been as yet no characterization of their activity in vivo. We focused on projections to the OB from the anterior olfactory nucleus (AON), a major source of cortical feedback to the OB. We expressed GCaMP selectively in AON projection neurons using a mouse line expressing Cre recombinase (Cre) in these neurons and Cre-dependent viral vectors injected into AON, allowing us to image GCaMP fluorescence signals from their axon terminals in the OB. Electrical stimulation of AON evoked large fluorescence signals that could be imaged from the dorsal OB surface in vivo. Surprisingly, odorants also evoked large signals that were transient and coupled to odorant inhalation both in the anesthetized and awake mouse, suggesting that feedback from AON to the OB is rapid and robust across different brain states. The strength of AON feedback signals increased during wakefulness, suggesting a state-dependent modulation of cortical feedback to the OB. Two-photon GCaMP imaging revealed that different odorants activated different subsets of centrifugal AON axons and could elicit both excitation and suppression in different axons, indicating a surprising richness in the representation of odor information by cortical feedback to the OB. Finally, we found that activating neuromodulatory centers such as basal forebrain drove AON inputs to the OB independent of odorant stimulation. Our results point to the AON as a multifunctional cortical area that provides ongoing feedback to the OB and also serves as a descending relay for other neuromodulatory systems.

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Comparison of Identified Mitral and Tufted Cells in Freely Breathing Rats: II. Odor-Evoked Responses

Cited by 28 publications

References 23 publications

Correlated firing in tufted cells of mouse olfactory bulb

Correlated firing in tufted cells of mouse olfactory bulb

Associative Cortex Features in the First Olfactory Brain Relay Station

Functional imaging of cortical feedback projections to the olfactory bulb

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