X-Message-Number: 10919 Date: Sat, 12 Dec 1998 19:59:49 -0500 From: Jan Coetzee <> Subject: memories Memories Are Made Of This, But Are They Plastic Spines? by Laura Spinney Researchers are unraveling the role played by the spinal cord in locomotion by looking at the interactions at the cellular level. At the first ever international conference on spinal cord plasticity in Los Angeles yesterday [7 Nov], Sten Grillner of the Nobel Institute for Neurophysiology at the Karolinska Institute in Stockholm described how he and his colleagues have traced the neuronal circuit by which sensory input leads to locomotion in a lower vertebrate. They studied the central nervous system--the brain stem and spinal cord--of the lamprey. The lamprey shares the basic features of the mammalian nervous system, but having fewer and larger neurons, it is easier to work with. According to Grillner, the cellular pathway that lights up when a lamprey spies a tasty morsel involves several sets of sensory information. The afferent neurons from the olfactory bulb and the optic nerve trigger neurons in the ventral thalamus, which act as a filter for information entering the brain. Those neurons in turn trigger reticulospinal neurons to fire, which then activate the circuitry in the spinal cord responsible for generating coordinated swimming patterns. Grillner has also studied the role of neurotransmitters in the spinal cord, and his latest findings relate to the neuropeptide Substance P, which in humans is found in some of the tiny C fibers that carry signals about painful stimuli to the brain. A ten-minute application of Substance P to the isolated CNS of a lamprey resulted in changes in the neurons that lasted for up to 36 hours. Grillner says this is the first time such long-lasting plasticity effects have been found. But while they resemble the mechanisms by which the human brain lays down memories, he is reluctant to describe what's going on in the lamprey's spinal cord as learning. What he will say, is that "the spinal cord is very important for coordinating movement." And, he adds, the findings have implications for humans. In a couple of years, the plasticity of the spinal cord that researchers are only now beginning to describe, as well as its responsiveness to neuropeptides, could be exploited for the rehabilitation of spinal cord-damaged patients. Rate This Message: http://www.cryonet.org/cgi-bin/rate.cgi?msg=10919