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 cut off. This means we can focus attention on a relatively small subset of the central nervous system and study the electrical activity, morphology, and pharmacology of individual spinal cord neurons, to reveal the kinds of neural circuitry that allow the spinal cord to select and generate appropriate movements. We have found in recent years that the spinal cord selects and generates these distinct movements using a combination of multifunctional and specialized spinal cord interneurons.

My lab’s research currently focuses on the following questions:

1) What mechanisms do multifunctional interneurons use to contribute to multiple kinds of limb movements?

2) What mechanisms do scratch-specialized interneurons use to affect scratching but not swimming?

3) What mechanisms do flexion reflex-selective interneurons use to affect flexion reflex (limb withdrawal), but not swimming or scratching?

4) How are behaviorally specialized interneurons inhibited during competing behaviors?

5) How do the spinal cord circuits for swimming, scratching, and flexion reflex interact?

6) Do neuromodulators alter swimming, scratching, and flexion reflex in the same or different ways?

7) How does the spinal cord summate gentle foot stimuli that are seconds apart to trigger a strong flexion reflex? 

• 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.
• Nguyen, K. H., Scheurich, T. E., Gu, T., and Berkowitz, A. (2020) Spinal interneurons with dual axon projections to knee-extensor and hip-extensor motor pools. Frontiers in Neural Circuits 14: 7, doi: 10.3389/fncir.2020.00007.
• Berkowitz (2019) Expanding our horizons: central pattern generation in the context of complex activity sequences. J. Exp. Biol. 222: jeb192054. doi: 10.1080/01677063.2019.1706093.
• Berkowitz, A. (2018) You can observe a lot by watching: Hughlings Jackson’s underappreciated and prescient ideas about brain control of movement. The Neuroscientist 24: 448-455 (cover article). doi: 10.1177/1073858418781819.
• Johnson, K. P., Tran, S. M., Siegrist, E. A., Paidimarri, K. B., Elson, M. S., and Berkowitz, A. (2017) Turtle flexion reflex motor patterns show windup, mediated partly by L-type calcium channels. Frontiers in Neural Circuits 11: 83, doi: 10.3389/fncir.2017.00083.
• 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)
• Berkowitz, Ari (2016) Governing Behavior: How Nerve Cell Dictatorships and Democracies Control Everything We Do. Harvard University Press, Cambridge, MA.
• Elson, M. S. and Berkowitz, A. (2016) Flexion reflex can interrupt and reset the swimming rhythm. J. Neurosci. 36: 2819 –2826.
• Hao, Z.-Z., Meier, M. L., and Berkowitz, A. (2014) Rostral spinal cord segments are sufficient to generate a rhythm for both locomotion and scratching, but affect their hip extensor phases differently. J. Neurophysiol. 112: 147-155. doi: 10.1152/jn.00119.2014
• Hao, Z.-Z., Spardy, L.E., Nguyen, E., Rubin, J.E., and Berkowitz, A. (2011) Strong interactions between spinal cord networks for locomotion and scratching. J. Neurophysiol. 106:1766-1781.