Olfactory Memory

Introduction

Olfactory Memory refers to the memory associated with odors and smells.If you just spare your 5 minutes in thinking that how our brain can memorise a smell which does not even seem to be a material thing then you'll get confused.Visual memory is associated with pictures, Echoic Memory is associated with sounds but both pictures and sounds can be stored as coded information but SMELL...! How memory of smell can be stored.To understand the structure of formation of olfactory memory we'll discuss each step through which the information is passed.

Importance

Studies have found various characteristics of common memories of odor memory including persistence and high resistance to interference. Explicit memory is typically the form focused on in the studies of olfactory memory, though implicit forms of memory certainly supply distinct contributions to the understanding of odors and memories of them. Research has demonstrated that the changes to the olfactory bulb and main olfactory system following birth are extremely important and influential for maternal behavior. Mammalian olfactory cues play an important role in the coordination of the mother infant bond, and the following normal development of the offspring. Maternal breast odors are individually distinctive, and provide a basis for recognition of the mother by her offspring. Olfactory memory was developed throughout evolution for various reasons. Among the most notable reasons are those related to the survival of the species and the development of early communication. Even in humans and animals today, these survival and communication aspects are still functioning. There is also evidence suggesting that there are deficits in olfactory memory in individuals with brain degenerative diseases such as Alzheimer's disease and dementia. These individuals lose the ability to distinguish smells as their disease worsens. There is also research showing that deficits in olfactory memory can act as a base in assessing certain types of mental disorders such as depression as each mental disorder has its own distinct pattern of olfactory deficits.

Process

Our sense of smell, though not as simple as our sense of taste, is very simple compared to the rest of the processes of our nervous system. Olfactory receptor proteins are able to recognize physiochemical molecules called odorants and relay information to the brain. Approximately one thousand of these proteins have been characterized. Each one is only able to recognize one odorant, yet we are able to experience and characterize many more than one thousand unique scents. Once an odorant binds to a receptor protein, the massage is sent via olfactory neurons in the olfactory epithelia to the olfactory cortex in the brain. These olfactory neurons only survive for approximately 60 days before they are replaced with new neurons. Olfactory neurons are also unmyelinated, making scent the slowest of the five senses and allowing the sensation of odor to persist for a relatively long period of time. It is perhaps the proximity of the olfactory bulb to the limbic system that gives scent such a strong influence over memory and emotion. The limbic system, specifically the amygdala and the hippocampus, are associated with processing emotion and memory.

Role of the Amygdala

The amygdala is a complex set of nuclei situated in the anterior temporal lobe and lies beneath the primary olfactory cortex. The amygdala is involved in the formation of memories of emotional experiences, particularly those associated with fear, flight, and defense. It is connected by various pathways to other parts of the brain, but most notably to the basal forebrain which contains magnocellular cells which provide extensive input into the neocortex and hippocampus. There are also direct projections to the hippocampus from the amygdala, which are involved in the integration of various sensations into memory. Neuropsychological research has suggested that this pathway is vital for the development of olfactory memories. The primary olfactory cortex and the hippocampus have extensive connections with the amydgala through both indirect and direct pathways. It is important for an animal to create memories of olfactory stimuli which threaten its survival. Without a properly functioning amygdala, olfactory memories would not be able to form which could put an animal at risk of dangerous stimuli in its environment due its lack of memory of such stimuli.

References
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