Brian Mulloney, Ph.D.

 Brian  Mulloney, Ph.D.

Position

  • Professor
  • Center for Neuroscience

Research Summary

I am interested in how an animal's nervous system produces the overt behaviors that we observe. My research concentrates on how the central nervous system of arthropods, particularly crayfish, works. The behaviors of these animals are complex, but their nervous systems have a structural elegance that makes the challenge of understanding these behaviors in cellular terms achievable. In answering questions about the neural basis of behaviors in these animals, we also provide probable explanations of complex behaviors in other animals, including vertebrates.

Some time ago, we began to analyze the central mechanisms that cause the swimmerets of crayfish to produce coordinated cycles of power-strokes and return-strokes whenever the animal swims forward. We demonstrated that each limb has its own module of neurons that can operate independently. This means that the normal coordination of movements of different limbs is imposed on these modules by a separate circuit of coordinating interneurons, and that we can study the organization of a module and of the coordinating circuit as separate problems.

My strategy is to combine electrophysiological experiments with computational analysis of the hypotheses these experiments generate. We have identified a small set of nonspiking local interneurons that are key components of each module. We have developed a minimal cellular model of the organization of a module, and are starting to test it experimentally. We have also described three types of intersegmental coordinating interneurons that are necessary and sufficient for normal intersegmental coordination, and described how these interneurons respond to changes in excitation of the system. We have developed a cellular model of the circuit formed by these interneurons. This model has dynamics similar to the dynamics of the real system, and that predicts the connections these interneurons make within their target modules.

Select Publications

Mulloney, B. and C. Smarandache (2010) Fifty years of CPGs: two neuroethological papers that shaped the course of neuroscience. Fron. Behav. Neurosci.  4 (45): 1-8.

Smarandache, C., W.M. Hall, and B. Mulloney (2009) Coordination of rhythmic motor activity by gradients of synaptic strength in a neural circuit that couples modular neural oscillators.  J. Neurosci. 29:9351-9360.  

Tschuluun, N. W.M. Hall, and B. Mulloney (2009) State-changes in the swimmeret system: a neural circuit that drives locomotion. J. Exp. Biol. 212:3605-3611.

Mulloney B, Hall WM (2007) Local and intersegmental interactions of coordinating neurons and local circuits in the swimmeret system. J Neurophysiol. 98: 405-413.

Hedrick, AV, M Hisada, and B Mulloney (2007) Tama-kugel: Hardware and software for measuring direction, distance, and velocity of locomotion by insects. J. Neurosci. Methods 164: 86-92.

Brian Mulloney and Wendy M Hall (2007) Not by spikes alone: Responses of coordinating neurons and the swimmeret system to local differences in excitation. J Neurophysiol 97:436-450.

Mulloney B, Harness PI, Hall WM (2006) Bursts of information: coordinating interneurons encode multiple parameters of a periodic motor pattern. J Neurophysiol 95:850-861.

Mulloney B (2005) A method to measure the strength of multi-unit bursts of action-potentials. J Neurosci Meth 146:98-105.

Mulloney B (2003) During fictive locomotion, graded synaptic currents drive bursts of impulses in swimmeret motor neurons. J. Neurosci. 23:5953-5962.

Mulloney B and WM Hall (2003) Local commissural interneurons integrate information from intersegmental coordinating interneurons. J. Comp. Neurol. 466: 366-376.

Jones SR, B Mulloney, TJ Kapper, and N Kopell (2003) Coordination of cellular pattern-generating circuits that control limb movements: The sources of stable differences in intersegmental phase. J. Neurosci. 23: 3457-3468.

Mulloney B, N Tschuluun, and WM Hall (2003) Architectonics of crayfish ganglia. Microscopy Res. and Tech. 60: 253-265.

Tschuluun N, WM Hall, and B Mulloney (2001) Limb movements during locomotion: Tests of a model of an intersegmental coordinating circuit. J Neurosci 21: 7859-7869

Nakagawa H, and B Mulloney (2001) Local specifications of relative strengths of synapses between different abdominal stretch-receptor axons and their common target neurons. J. Neurosci. 21:1645-1655

Mulloney, B and WM Hall (2000) Functional organization of crayfish abdominal ganglia: III. Swimmeret motor neurons. J. Comp. Neurol. 419: 233-243

Namba, H. and B. Mulloney (1999) Coordination of limb movements: Three types of intersegmental interneurons in the swimmeret system, and their responses to changes in excitation. J Neurophysiol. 81:2437-2450

Skinner FK and B Mulloney (1998) Intersegmental coordination of limb movements during locomotion: mathematical models predict circuits that drive swimmeret beating. J Neurosci. 18:3831-3842

Affiliations

Neurobiology Physiology and Behavior

Center for Neuroscience

Animal Behavior

Neuroscience