Sensory experience and adult neurogenesis

The same effect could readily be attributed to pheromones, as it is to food odors.

Sensory experience and rest control survival of newborn neurons in adults

When it comes to the circuits that make up the olfactory system, it seems that less is more. Much like the addition and elimination of extra synapses that helps fine-tune brain circuitry, the olfactory system continues to produce and remove neurons throughout life. Yet it is not entirely clear how and why some newborn neurons are preserved while others are eliminated. Now, new research published by Cell Press in the September 8 issue of the journal Neuron reveals that both olfactory experience during feeding and a subsequent period of rest contribute to both the likelihood that a new olfactory neuron will escape elimination and be incorporated into existing circuitry.

In mice, olfactory neurons called “granule cells” are generated and incorporated into the neuronal circuitry from birth through adulthood. About half of these neurons are integrated into existing circuitry, while the other half are eliminated through a process called apoptosis. The mechanisms that underlie the selection process are not well understood, though some clues have come from studies showing that synaptic elimination associated with memory and learning depends on the sleep-wake cycle.

A research group led by senior study author Dr. Masahiro Yamaguchi from the University of Tokyo examined whether distinct behavioral periods might also impact plasticity in the olfactory system. “We were interested in determining whether the selection of adult-born granule cells in the olfactory bulb occurs continuously throughout the day or whether it occurs in association with specific behavioral states,” explains Dr. Yamaguchi.

Using a combination of behavioral analysis and a staining technique that allowed detection of apoptotic cells, Dr. Yamaguchi and colleagues observed that extensive elimination of adult-born granule cells occurred during the period immediately after the mice had eaten, a time during which the mice engaged in typical post-meal behaviors such as rest, extended grooming, and sleep. Interestingly, when these behaviors were disrupted, apoptosis was prevented. The researchers also observed that the extent of apoptosis was regulated by prior olfactory sensory experience. Sensory deprivation (occlusion of one nostril) enhanced granule cell apoptosis specifically during the time period after feeding. The authors suggest that sensory experience thus serves to “tag” key synapses and prevent them from being eliminated during subsequent sleep.

“Our results suggest that extensive structural reorganization of the circuitry in the olfactory bulb occurs during the period after feeding and that this reorganization reflects sensory experience from the preceding waking period,” concludes Dr. Yamaguchi. “Complex mechanisms of experience-dependent reorganization in the olfactory bulb will likely be revealed in the framework of two sequential behavioral periods, the waking period with olfactory behavior and the rest/sleep period that follows olfactory behavior.”

About James V. Kohl 1307 Articles
James Vaughn Kohl was the first to accurately conceptualize human pheromones, and began presenting his findings to the scientific community in 1992. He continues to present to, and publish for, diverse scientific and lay audiences, while constantly monitoring the scientific presses for new information that is relevant to the development of his initial and ongoing conceptualization of human pheromones. Recently, Kohl integrated scientific evidence that pinpoints the evolved neurophysiological mechanism that links olfactory/pheromonal input to genes in hormone-secreting cells of tissue in a specific area of the brain that is primarily involved in the sensory integration of olfactory and visual input, and in the development of human sexual preferences. His award-winning 2007 article/book chapter on multisensory integration: The Mind’s Eyes: Human pheromones, neuroscience, and male sexual preferences followed an award winning 2001 publication: Human pheromones: integrating neuroendocrinology and ethology, which was coauthored by disinguished researchers from Vienna. Rarely do researchers win awards in multiple disciplines, but Kohl’s 2001 award was for neuroscience, and his 2007 “Reiss Theory” award was for social science. Kohl has worked as a medical laboratory scientist since 1974, and he has devoted more than twenty-five years to researching the relationship between the sense of smell and the development of human sexual preferences. Unlike many researchers who work with non-human subjects, medical laboratory scientists use the latest technology from many scientific disciplines to perform a variety of specialized diagnostic medical testing on people. James V. Kohl is certified with: * American Society for Clinical Pathology * American Medical Technologists James V. Kohl is a member of: * Society for Neuroscience * Society for Behavioral Neuroendocrinology * Association for Chemoreception Sciences * Society for the Scientific Study of Sexuality * International Society for Human Ethology * American Society for Clinical Laboratory Science * Mensa, the international high IQ society