Data from: Value-related learning in the olfactory bulb occurs through pathway-dependent peri-somatic inhibition of mitral cells

Associating values to environmental cues is a critical aspect of learning
from experiences, allowing animals to predict and maximise future rewards.
Value-related signals in the brain were once considered a property of
higher sensory regions, but their wide distribution across many brain
regions is increasingly recognised. Here, we investigate how
reward-related signals begin to be incorporated, mechanistically, at the
earliest stage of olfactory processing, namely, in the olfactory bulb. In
head-fixed mice performing Go/No-Go discrimination of closely related
olfactory mixtures, rewarded odours evoke widespread inhibition in one
class of output neurons, that is, in mitral cells but not tufted cells.
The temporal characteristics of this reward-related inhibition suggest it
is odour-driven, but it is also context-dependent since it is absent
during pseudo-conditioning and pharmacological silencing of the piriform
cortex. Further, the reward-related modulation is present in the somata
but not in the apical dendritic tuft of mitral cells, suggesting an
involvement of circuit component located deep in the olfactory bulb.
Depth-resolved imaging from granule cell dendritic gemmules suggests that
granule cells that target mitral cells receive a reward-related extrinsic
drive. Thus, our study supports the notion that value-related modulation
of olfactory signals is a characteristic of olfactory processing in the
primary olfactory area and narrows down the possible underlying mechanisms
to deeper circuit components that contact mitral cells peri-somatically.