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

           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.

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