Periglomerular cell function in odour discrimination probed in AMPA-type glutamate receptor-interacting protein CKAMP44 knockout mice

Abstract

Olfaction is the one of the primary modalities for the sensory representation of the external environment for rodents. Although the structure of the olfactory bulb is well described and studied, the role of individual elements of the bulb is still a working topic of research. Periglomerular cells are inhibitory interneurons which inhibit the mitral cells in the olfactory bulb and can modulate its activity output as a whole. This can influence the perception of an odour for the mice. In this study, we try to quantify the role periglomerular cells play in the discrimination of two odours. CKAMP44 is an AMPA-receptor interacting protein present in the periglomerular cells. It has been shown that the deletion of this protein significantly decreases periglomerular cell activity, and thereby increases mitral cell activity, which are the projection neurons to the cortex. With the help of a series of behavioural experiments performed in wild-type and CKAMP44 knockout mice differences in the odour discrimination accuracies of the two groups of mice were found. These differences arise when the odours are presented at low concentrations of 10-5 v/v. Moreover, a gamma oscillatory model of the olfactory bulb was adapted, and mitral cell firing pattern data from the simulations was analysed using a neural network and K-means algorithm. These computations show that mitral cell activity patterns for different odours remain segregated for the CKAMP44 knockout mice, but become un-segregable for wildtype mice at lower input strengths. Hence, such a mechanism could be envisioned and further tested experimentally as a mechanistic basis of the enhanced odour discrimination at low concentrations found in CKAMP44 knockout mice.