Signal and noise: Spike correlations in the olfactory system
by John Hewitt
Excerpt: “The olfactory system is not so much a hard-wired telephone network where channels can be instantaneously specified and connected by number codes, and then used to transmit further codes. There is significant overgrowth and back-pruning in olfactory networks during development, and some ongoing cell replacement, but once etched, many of its larger features remain stable.”
My comment: This comparison is meaningful: “…any message can not stand out like the clear dots and dashes of Morse code above noise, but must surf in the ocean where every wave is considered potentially meaningful.”
See for example Nurse (2008): “A metaphor here would be the use of the Morse code and the telegraph to communicate messages. Pulses of information sent along the telegraph generate a code for letters and as a consequence sentences can be communicated. This converts the same signalling pathway from a simple on/off switch to a device that can transfer, for example, the works of Shakespeare. It is likely that dynamics has been exploited more generally in the evolution of biological systems for signalling purposes, allowing the communication of more complex information.”
In mammals, breathing transmits chemical to electrical pulses (not waves) of information that allows olfactory/pheromonal input to epigenetically effect the hypothalamic secretion of gonadotropin releasing hormone (GnRH). Pulses of GnRH integrate sensory input associated with food odors and social odors called pheromones during what we were just told in the news article is a self-organized network that spontaneously emerges during prenatal and postnatal development of other sensory abilities. A self-organized network that spontaneously emerges incorporates the magic of mutation-initiated natural selection. Biological facts incorporate olfactory/pheromonal input and their epigenetic effects on RNA-directed DNA methylation and RNA-mediated amino acid substitutions that link nutrient-dependent changes in the microRNA/messenger RNA balance to the GnRH pulse and its downstream effects on other hormones that affect behavior.
The innate ability of the olfactory system to organize itself and emerge during development as the key integrator of all other sensory input (visual, tactile, auditory) results from nutrient-dependent pheromone-controlled adaptive changes in the brain and behavior of invertebrates and vertebrates.
