Olfactory Bulb Units: Activity Correlated with Inhalation Cycles and Odor Quality

Abstract

Single olfactory bulb units were studied in two macrosmatic species of rodents under conditions intended to preserve the cyclical stimulation which normally accompanies nasal breathing. Patterns of unit activity related to the inhalation cycle were observed in all animals, often in the absence of specific stimuli, and could not be explained in simple mechanical terms. Distinctive changes in these patterns occurred in response to certain odors, and were generally independent of changes in the overall firing frequency. These findings indicate that a change in the overall firing frequency of unit discharges is neither a necessary nor sufficient measure of responsiveness to odors in the rodent olfactory bulb, and that stimulus-specific temporal distributions of unit firing may be involved in olfacto-endocrine activities.

External Tufted Cells Drive the Output of Olfactory Bulb Glomeruli

“…In vivo, odors evoke slow rhythmic activity that is synchronized with respiration (Macrides and Chorover, 1972;Chaput et al, 1992;Charpak et al, 2001;Cang and Isaacson, 2003). This activity persists, although not as regular, in the absence of odorant input (Fontanini et al, 2003) and can be uncoupled from the breathing cycle in mice lacking mechanosensitive olfactory receptors (Grosmaitre et al, 2007).…”

“…The slow (2-8 Hz) oscillations correlate with the respiratory cycle (Macrides and Chorover, 1972;Buonviso et al, 1992;Charpak et al, 2001;Cang and Isaacson, 2003). Although the phasic nature of afferent inputs undoubtedly contributes to the slow patterning (Sobel and Tank, 1993), the intrinsic dynamics of the bulbar network could also be involved.…”

Respiratory cycle as time basis: An improved method for averaging olfactory neural events

“…Respiratory modulation of electro-encephalographic (EEG) and local field potential (LFP) signals has been extensively described in OB and OC (Boudreau & Freeman, 1963;Freeman, 1975;Freeman & Schneider, 1982;Freeman, 1983;Buonviso et al, 2003, Fontanini et al, 2003. Such a respiratory modulation has also been described in cell unitary activities in the OB mitral/tufted (Walsh, 1956;Macrides & Chorover, 1972;Chaput & Holley, 1980;Onoda & Mori, 1980;Mair, 1982;Pager, 1985;Chaput, 1986) and was recently described in the piriform cortex (PC) (Wilson, 1998;Litaudon et al, 2003). Rather than a variation in overall firing frequency, odor-evoked cell responses have often been reported as a temporal reorganization of their discharges into inhalation-related bursts of spikes.…”

Temporal coding of sensory information in the brain

“…However, phase-locking to air-intake (sniffing) cycles [69] and emergent synchronized oscillations may provide population-based reference times for latency-pattern [65,66] and latency-offset codes [70,71]. Artificial chemical recognition devices that analyze intrinsic temporal response patterns of optical chemosensors have been developed that outperform analyses based on averaged across- [83].…”

“…In olfaction, odorant-related time patterns of neural response have been observed in a wide variety of systems [63][64][65][66][67] Historically, efforts to find temporal pattern primitives for smell have been confounded by concentration-dependent changes in temporal response patterns [68] and complex history-dependencies. However, phase-locking to air-intake (sniffing) cycles [69] and emergent synchronized oscillations may provide population-based reference times for latency-pattern [65,66] and latency-offset codes [70,71].…”