Elsevier

Physiology & Behavior

Volume 77, Issues 4–5, December 2002, Pages 607-612
Physiology & Behavior

Lateral inhibition in the olfactory bulb and in olfaction

https://doi.org/10.1016/S0031-9384(02)00895-8Get rights and content

Abstract

Lateral inhibition in the olfactory bulb is mediated by circuits that involve reciprocal dendrodendritic connections between mitral and granule cells. Because of the properties of these connections and also because odor stimuli are not represented in an obviously topographic fashion, questions have been raised about whether the function of local inhibition in the olfactory bulb can be compared to the function of inhibition in other brain areas. Here, I propose an analysis of local inhibition in the olfactory bulb based on the simplification that olfactory bulb circuitry can be thought of as implementing a simple linear two-dimensional filter. This analysis highlights some important characteristics of the circuitry of the olfactory bulb and suggests that the function of lateral inhibition in the olfactory bulb may be to compensate for generalized, spatially distributed activation that otherwise may obscure the specific, discrete patterns of glomerular activation seen across the olfactory bulb.

Section snippets

Lateral inhibition in the olfactory bulb

The known anatomy and physiology of the olfactory bulb (and similarly the antenna lobe of insects) suggest that activity of a cluster of nearby mitral cells (the principal neurons of the olfactory bulb) will result in inhibition of other mitral cells located at some distance from the active cells. The synaptic circuitry mediating this inhibition consists of reciprocal dendrodendritic synapses made between excitatory mitral cells and inhibitory granule cells. Active mitral cells release

Filters and lateral inhibition

Before detailing the properties of lateral inhibition in the olfactory bulb, I consider what properties a circuit must have in order to mediate lateral inhibition at the functional level; that is, to cause the sharpening of receptive fields and the enhancing of contrast that are the functional hallmarks of lateral inhibition. To help understand what properties are required, one can begin with the simplification of viewing lateral inhibition as a simple linear filter. Such filters are used in

Physiological implementation of filters

To make use of this analogy between filtering of images and lateral inhibition, one must be able to determine (or at least approximate) the kernel function of the filtering that is performed by a given brain network. To estimate the kernel function, one can take advantage of the fact that if a filter is applied to an image that consists of a single pixel (with all other pixels of amplitude zero), then the resulting filtered image is just the kernel function itself, scaled by the amplitude of

The spatial properties of lateral inhibition in the olfactory bulb

In image filtering, the spatial requirement for filter design is clear: signals such as edges are enhanced best when their spatial frequency is similar to the spatial frequency of the filter. In this case, nearby activated pixels cause mutual enhancement and distant activated pixels cause mutual inhibition. On this analogy, for lateral inhibition to cause sharpening of spatial signals in the bulb, activation of one cell or a small population of cells with similar receptive fields must result in

The functional roles of local inhibition in olfaction

In the mammalian olfactory bulb, a general blockade of inhibition clearly results in an overall increase in spontaneous and odor-evoked mitral cell firing [4], [21] that may result in a broadening of the tuning curves of mitral cells that are activated by straight chain aldehydes of differing lengths [4]. A simple prediction for the effects of lateral inhibition on olfactory behavior would be that impairment of lateral inhibition should impair performance on olfactory discrimination tasks, and

References (31)

  • M.T. Shipley et al.

    Functional organization of olfactory system

    J. Neurobiol.

    (1996)
  • M.T. Shipley et al.

    Olfactory bulb

  • M. Yokoi et al.

    Refinement of odor molecule tuning by dendrodendritic synaptic inhibition in the olfactory bulb

    Proc. Natl. Acad. Sci. U. S. A.

    (1995)
  • S.W. Kuffler

    The single-cell approach in the visual system and the study of receptive fields

    Invest. Ophthalmol.

    (1973)
  • H.K. Hartline

    Inhibition of activity of visual receptors by illuminating nearby retinal areas in the Limulus eye

    Fed. Proc.

    (1949)
  • Cited by (0)

    View full text