Mammalian olfactory cues play an important role in the coordination of the mother infant bond, and the following normal development of the offspring.
[1] In mammals, each olfactory receptor protein has one type of molecule that it responds to, known as the one-olfactory-one-neuron rule, and approximately one thousand kinds of which have been identified.
[1] Neuromodulation exists in the olfactory system and is responsible for neural plasticity and behavioural change in both mammals and insects.
[5] The importance of cholinergic systems has been demonstrated in studies of rats and the effects of scopolamine, with acetylcholine being involved in initial learning stages and more specifically in the reduction of interference between stored memories.
[8] Evidence of the formation of implicit memory is found in tests of habituation, sensitization, perceptual learning and classical conditioning.
[4] Acetylcholine is also regarded as an important neurotransmitter involved in the habituation of olfactory stimulus, though the exact means through which it operates are not yet clear.
[4] Attention focused on odors aids in the functioning of everyday life as well as the engagement of proper responses to experienced events.
[8] A potential problem with this measure involves the generation of verbal labels that may enhance memory for olfactory stimuli.
[11] Neural plasticity is also an important part of olfaction, as different experiences may result in alterations of both cortical and subcortical circuitry in the brain.
[4] The amygdala is a complex set of nuclei situated in the anterior temporal lobe and lies beneath the primary olfactory cortex.
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.
[19] A significant change takes place in the regulation of olfaction just after birth so that odors related with the offspring are no longer aversive, allowing the female to positively respond to her babies.
The main olfactory bulb is one of the neural structures that experiences profound change when exposed to offspring odors at the time of childbirth.
[19] Human neuroimaging studies suggest that activation of the medial prefrontal cortex (mPFC) occurs during tests of olfactory memory.
[19] Mammalian olfactory cues play an important role in the coordination of the mother infant bond, and the following normal development of the offspring.
[19] The offspring of several different mammals are attracted to the odor of amniotic fluid, which helps to calm and adapt the infant to the novel environment outside of the womb.
[21] After the birth of the offspring, there is a shift in the value of the infant's odors to the mother, which causes change in neural structures such as the olfactory bulb.
[22] Newborn infants respond positively to the smell of their own amniotic fluid, which may serve as evidence for intrauterine olfactory learning.
This is shown by rat pups, who avoid odors that they experienced in association with a noxious stimulus prior to birth.
[22] Intrauterine olfactory learning may be demonstrated by behavioral evidence that newborn infants respond positively to the smell of their own amniotic fluid.
[20] Olfactory cues are widespread within parental care to assist in the dynamic of the mother-infant relationship, and later development of the offspring.
[19] In support of fetal olfactory learning, newborn infants display behavioral attraction to the odor of amniotic fluid.
Although exposure to amniotic fluid is eliminated after birth, breast fed babies have continued contact with cues from the mother's nipple and areola area.
[20] As demonstrated by animals in the wild (the great apes, for example), the offspring is held by the mother immediately after birth without cleaning and is continually exposed to the familiar odor of the amniotic fluid (making the transition from the intrauterine to extrauterine environment less overwhelming).
[20] As a result, it seems natural selection should favor the development of a means to help in maintain and establish effective breast feeding.
[20] The mother's olfactory signature is experienced with reinforcing stimuli such as food, warmth and tactile stimulation; enhancing further learning of that cue.
[22] Neural structures such as the olfactory bulb undergo extensive changes when exposed to infantile odors; providing a starting point for individual recognition by the mother.
[19] Studies of the mammalian brain have discovered that the excess of cerebral neurons is a phenomenon of mainly animals which had to seek and capture food.
These neurons have become a large part of the olfactory system throughout evolution to allow higher mammals such as primates to have a better chance for survival through more advanced methods of hunting and finding food.
Their performance was compared with those of a control group injected with a saline solution"[43] and the results were that significant olfactory deficits were found during the three-week period of testing.