Associative learning and recollection of olfactory memory during the respiratory cycle in mammals: how is the self cognized in consciousness?

When awake and relaxed, spontaneous activation of memory engrams brings various memory-scenes to mind, and the present self may long for them. Odorants are strong cues for remembering associated memories. Associative learning of odor signals and object cognition allows prediction of cognitive imagery of an environmental object. The neural network connecting olfactory cortices to higher cognitive areas dynamically switches processing from feedforward to top-down, correlated with the respiratory cycle. During inhalation, feedforward odor signals drive burst firings of specific pyramidal cells in the olfactory cortex; during late exhalation, top-down cognitive scene-signals reactivate the same cells, potentially inducing plastic changes that form associative-learning memory.

Study at a glance

Abstract

When we are awake and relaxed, various memory-scenes come up in our mind by spontaneous activation of memory engrams. We find ourselves in the memory-scene longing for it by the present self. The memory scene is also recollected by sensory inputs from the surrounding world for learned behavioral decisions. It is well experienced that odorants act as strong cues in remembering associated memory. Associative learning of odor signals and object cognition enables us to predict cognitive imagery of an environmental object. Here, we discuss the neural network connecting the olfactory cortices to the higher cognitive areas that dynamically switches the processing mode from feedforward to top-down. These processes are correlated with the respiratory cycle to form and recollect odor-object associative memory. We infer that during the inhalation phase, feedforward odor signals drive burst firings of a specific subset of pyramidal cells in the olfactory cortex. In contrast, during the subsequent late-exhalation phase, top-down cognitive scene-signals from the higher areas activate again the same pyramidal cells as those activated by the feedforward signals. Reactivation of pyramidal cells during the exhalation phase may induce plastic changes in the inter-areal synaptic connections in the neural network to form associative-learning memory. In this perspective article, we will discuss associative learning and cognition of self in the mammalian olfactory system.