Scott L. Hooper, Ph.D.

     Rhythmic activity is widespread in nervous systems, and plays a central role in motor pattern production and sensory processing. These rhythms are generated endogenously by central neural networks, and are thus an example of the nervous system's ability to spontaneously create patterns. Network rhythmicity has been extensively studied, and we have a general understanding of the mechanisms underlying it. However, we understand much less about its dynamic regulation (how pattern period and phasing are controlled), and how these networks interact with their peripheral effectors to continually generate behaviorally appropriate motor outputs.

     We study these issues in the pyloric neuromuscular system of the lobster, Panulirus interruptus. The pyloric network produces a 3 phase rhythmic neural output, and is composed of ~14 neurons divided into 6 types. The lab has two main projects. In the first, we have shown that the network maintains phase (neuron burst durations and inter-neuronal delays proportionally change as period changes) when cycle period is varied 3 to 5 fold; we are now studying the cellular and network mechanisms underlying this ability.

     Our second major interest is determining the effect changing neural output has on muscle activity. We have shown that pyloric muscles have very non-linear responses to changing neural input (including transforming rhythmic input into tonic contraction), and that each muscle responds differently to changes in neural input. We are now investigating the cellular basis of these non-linear responses, and describing their consequences on pyloric motor output.

Selected References:

• SL Hooper (2000) Central pattern generators. Current Biology 10(5):R176-R177.

• LG Morris, JB Thuma, and SL Hooper (2000) Preferential low frequency extraction from broad-band neuronal input allows mucles to express motor patterns of networks that do not innervate them. Nature Neuroscience 3(3):245-250.

• SL Hooper, V Brezina, EC Cropper, and KR Weiss (1999) Flexibility of Muscle Control by Modulation of Muscle Properties. In: Beyond Neurotransmission: The Roles of Neuromodulation in Information Flow and Neuronal Circuit Flexibility. Katz, P.S., ed. Oxford University Press, 241-274.

• SL Hooper (1998) Transduction of temporal patterns by single neurons. Nature Neuroscience 1(8):720-726.

• LG Morris and SL Hooper (1998) Muscle response to changing neuronal input in the lobster (Panulirus interruptus) stomatogastric system: Slow muscle properties can transform rhythmic input into tonic output. J Neurosci, 18(9):3433-3442.

• LG Morris and SL Hooper (1997) Muscle response to changing neuronal input in the lobster (Panulirus interruptus) stomatogastric system: Spike number vs. spike frequency dependent domains. J Neurosci 17:5956-5971.