How does an animal's nervous system select and generate an appropriate behavior for each circumstance the animal faces? Our research addresses this general question through neurophysiological, neuroanatomical, and pharmacological experiments on an especially suitable model system: the turtle spinal cord. The turtle spinal cord can produce three distinct types of rhythmic scratching movements of a hindlimb, each targeted to a different region of the body, as well as two types of rhythmic swimming movements of the hindlimbs and limb withdrawal (flexion reflex). The programs for generating these movements and for "choosing" among them reside in the spinal cord: the animal can produce these movements appropriately even when all input from the brain is removed. This means that we can focus attention on a relatively small subset of the central nervous system and study the electrical activity and the morphology of individual spinal cord neurons that are involved in selecting and generating each type of movement. We can then reveal the kinds of neural circuitry that allow the spinal cord to select and generate appropriate movements. We have found that most spinal cord neurons are multifunctional–they are activated during both swimming and scratching–but there are also some behaviorally specialized neurons. Scratch-specialized neurons are activated during scratching but not swimming, while flexion reflex-selective neurons are activated during flexion reflex, but not swimming or scratching. We are currently exploring how multifunctional and behaviorally specialized neurons work together to generate the right motor output at the right time.
Bannatyne, B. A., Hao, Z. Z., Dyer, G. M. C., Watanabe, M., Maxwell, D. J., and Berkowitz, A. (2020) Neurotransmitters and motoneuron contacts of multifunctional and behaviorally specialized turtle spinal cord interneurons.
J. Neurosci. 40: 2680-2694 (Featured Research), doi: https://doi.org/10.1523/JNEUROSCI.2200-19.2020.
Hao, Z.-Z. and Berkowitz, A. (2017) Shared components of rhythm generation for locomotion and scratching exist prior to motoneurons. Frontiers in Neural Circuits, 11: 54, doi: 10.3389/fncir.2017.00054 (recommended by F1000).
Elson, M. S. and Berkowitz, A. (2016) Flexion reflex can interrupt and reset the swimming rhythm. J. Neurosci. 36: 2819 –2826; doi: 10.1523/JNEUROSCI.3587-15.2016
Berkowitz, Ari (2016) Governing Behavior: How Nerve Cell Dictatorships and Democracies Control Everything We Do. Harvard University Press, Cambridge, MA.
Hao, Z.-Z., Spardy, L.E., Nguyen, E.B.L., Rubin, J.E., and Berkowitz, A. (2011) Strong interactions between spinal cord networks for locomotion and scratching. J. Neurophysiol. 106: 1766-1781, doi: 10.1152/jn.00460.2011
