This implies that GCs represent MC inputs in the

inhibitory current returned to the MCs. As a result, MCs transmit to the cortex errors of GC representations. The responses of GCs in our model are highly nonlinear, with most of them remaining silent. Because MCs play the role of error neurons, their sustained responses are sparse, which is a form of orthogonalization that is alternative to Wick et al., 2010. Overlap reduction in the olfactory bulb network was previously proposed theoretically on the basis of a periglomerular network implementing surround inhibition (Linster and Hasselmo, 1997). This hypothesis was supported by enhanced generalization between chemically similar odorants by rats with strengthened periglomerular inhibition (Linster et al., 2001). We suggest a mechanism for redundancy reduction by GC inhibition that is organized selleckchem functionally rather than spatially in a task-dependent manner. This Ribociclib mw proposal is consistent with nonlocal interglomerular connectivity (Fantana et al., 2008). The sparseness of the MC responses depends on the nonlinearity of the GCs and, specifically, on the GC activation threshold θ. In this study, we assumed that all GCs have similar activation thresholds that are small enough for GCs to be easily activated by low levels of activity in MCs. If the thresholds for activation of individual GCs are different, it is possible to envision

a mechanism by which the olfactory code carried by both MCs and GCs can be controlled to adapt to a particular task. Thus, if the threshold for activation is raised for a subset of GCs, these cells will be no longer active; therefore, their activity will not be extracted from the firing of MCs. If, for example, the threshold for all of the GCs is increased, thus making them unresponsive, then the olfactory code carried by the MCs replicates their inputs from receptor neurons. If the activation threshold is lowered for a subset of GCs, these cells will

efficiently extract their activity from the MCs’ responses. Thus, a particular redundancy among similar odorants can be excluded in a task-dependent manner. Therefore, Rebamipide the thresholds for GC activation may regulate both an overall sparseness of MC responses and the fine structure of the bulbar olfactory code. GC excitability depends on cellular properties but can also be effectively modulated by additional input into these cells. The GCs in the mammalian olfactory bulb are recipients of the efferent projections from the cortex and other brain areas (Davis and Macrides, 1981 and Luskin and Price, 1983). These signals to GCs can change their effective threshold values. If a GC receives excitatory inputs from the cortex, then the MC signal is closer to the threshold value, and the GC is more readily excited by the odorant-related inputs.