Olfactory bulb

Olfactory bulb is a neural structure involved in olfaction, the sense of smell. It sends olfactory information to be further processed in the amygdala, the orbitofrontal cortex (OFC) and the hippocampus where it plays a role in emotion, memory and learning.

The bulb is divided into two distinct structures: the main olfactory bulb and the accessory olfactory bulb.

The main olfactory bulb connects to the amygdala via the piriform cortex of the primary olfactory cortex and directly projects from the main olfactory bulb to specific amygdala areas.

The olfactory bulb sends olfactory information to be further processed in the amygdala, the orbitofrontal cortex (OFC) and the hippocampus where it plays a role in emotion, memory and learning.

The main olfactory bulb connects to the amygdala via the piriform cortex of the primary olfactory cortex and directly projects from the main olfactory bulb to specific amygdala areas. The amygdala passes olfactory information on to the hippocampus.

©WIKIPEDIA

The orbitofrontal cortex, amygdala, hippocampus, thalamus, and olfactory bulb have many interconnections directly and indirectly through the cortices of the primary olfactory cortex.

The accessory olfactory bulb resides on the dorsal-posterior region of the main olfactory bulb and forms a parallel pathway. Destruction of the olfactory bulb results in ipsilateral anosmia, while irritative lesions of the uncus can result in olfactory and gustatory hallucinations.

Olfactory bulb removal in rats effectively causes structural changes in the amygdala and hippocampus and behavioral changes similar to that of a person with depression. Researchers use rats with olfactory bulbectomies to research antidepressants.

Research has shown that removal of the olfactory bulb in rats leads to dendrite reorganization, disrupted cell growth in the hippocampus, and decreased neuroplasticity in the hippocampus.

These hippocampal changes due to olfactory bulb removal are associated with behavioral changes characteristic of depression, demonstrating the correlation between the olfactory bulb and emotion.

The olfactory bulb is, along with both the subventricular zone and the subgranular zone of the dentate gyrus of the hippocampus, one of only three structures in the brain observed to undergo continuing neurogenesis in adult mammals.

In most mammals, new neurons are born from neural stem cells in the sub-ventricular zone and migrate rostrally towards the main  and accessory olfactory bulbs.

Within the olfactory bulb these immature neuroblasts develop into fully functional granule cell interneurons and periglomerular cell interneurons that reside in the granule cell layer and glomerular layers, respectively.

©WIKIPEDIA

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