, Volume 44, Issue 5, pp 383-389

First online:

Multifunctional interneurons in behavioral circuits of the medicinal leech

  • W. B. KristanJrAffiliated withDepartment of Biology, B-022, University of California
  • , G. WittenbergAffiliated withDepartment of Biology, B-022, University of California
  • , M. P. NusbaumAffiliated withDepartment of Biology, Brandeis University
  • , W. Stern-TomlinsonAffiliated withDepartment of Biology, B-022, University of California

Rent the article at a discount

Rent now

* Final gross prices may vary according to local VAT.

Get Access


We are using the medicinal leech to study the neuronal basis of behavioral choice. In particular, we are recording from neurons, both extracellularly and intracellularly, in preparations that can express three different behaviors: the shortening reflex, crawling and swimming. We have found that particular mechanosensory neurons can elicit any of the behaviors, and that the movements are produced by just four sets of muscles, each controlled by a small number of motor neurons. Hence, there must be three different pattern-generating neuronal circuits, each of which can be activated by the same set of sensory neurons. We are studying how the choice is made among the three behaviors by recording, while one behavior is being performed, from neurons known to be involved in the initiation of the other two. We have found that an interneuron, cell 204, which is known to initiate and maintain swimming, is also active during shortening and crawling. The activity level in this interneuron can influence whether a mechanosensory stimulus produces shortening or swimming. The neuronal mechanisms by which this choice is normally effected awaits further elucidation of the circuits that elicit and generate shortening and crawling.

Key words

Behavioral state command neuron gating neuron leech mechanosensory neuron motor neuron pattern-generating neuron rhythmic motor pattern shortening reflex trigger neuron