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.
