What do we do

Behaviors result from integrated systems of neural circuits, muscles and body structures. These systems, working together and interacting with the physical environment, generate movement. Movement and the morphology that underlies it change strikingly over developmental and evolutionary time while maintaining critical roles for the organism. Our research examines how such systems function, how they change through the life history of an organism and how they diversify over longer timescales across the landscape of animal evolution.

At the foundation of our work is the study of how groups of neurons are organized into circuits.  We are addressing how circuits in the brain and spinal cord control and coordinate movement, examining both output to motor systems as well as how sensation of mechanical signals from the environment modulate that output.

Our primary research species is the zebrafish, a genetic and developmental model that provides exceptional in vivo accessibility to neural circuits of the brain and spinal cord and that shares a wide range of nervous system features with other vertebrates.

For broader work on behavior and biomechanics, we also study fishes comparatively, taking advantage of exceptional taxonomic diversity as well as enormous morphological and behavioral richness in the group.

In both model system and comparative contexts we aim to develop greater understanding of neuromechanical systems for movement in vertebrates and general principles of how such systems develop and evolve.

 

Neural Circuit Structure and Function

We examine how simple neural circuits that drive movement of the limbs and axis are organized. Focal systems in the lab include the hindbrain and spinal cord circuit that drives startle behavior and the circuit that controls rhythmic movement of the pectoral fins (homologous to our forelimbs). We aim to map how neurons in these circuits are connected and their roles in movement. Most of our research in these systems has been performed in zebrafish, because the brain and spinal cord of the larvae are accessible for morphological and physiological studies; however, work in other species has also been important. It has helped us to identify behaviors, such as the S-start startle behavior, that are difficult to observe in larval zebrafish and allowed us to study behaviors that are not part of the zebrafish repertoire.

Related references: Green and Hale, 2013; Liu and Hale, 2014; Bierman et al., 2009; McLean et al., 2007; Hale et al., 2005; Hale et al., 2001. See full publication list and reference information on publications page.

 

Mechanosensation and proprioception

Over the past few years we have begun to examine how limb mechanosensation may be used to modulate fin movements. In humans and other mammals, it was well known that proprioception, the sense of movement and position of the limbs in space, was critical for normal limb function. Little comparable work had been performed in fishes, and none in typical fin-based propulsion. Through a combination of morphology, physiology and behavioral experiments, we’ve found that the pectoral fins are mechanosensors and that this sensation modulates movement. We continue these experiments in a number of directions, including examining the relationship between fin bimechanics and mechanosensation.

Related references: Williams et al., 2013; Phelan et al., 2010. See full publication list and reference information on publications page.

 

Evolution and Development of Neural Systems and Behavior

A fundamental line of experiments in the lab investigates how movement systems change through time – both the short time frame of development and the longer time frame of evolution.  We are  interested in how systems change and how such changes, which often involve multiple body systems and functional demands are coordinated. In addition, by exploring movements systems across a range of species and locomotor behaviors we gain insight into structural and functional diversity in aquatic systems. Such breadth of study informs our work on evolutionary neuroscience, comparative biomechanics and collaborations with engineers on bio-inspired design.

 Related references: Hale, 1999; Thorsen et al., 2004; Thorsen and Hale, 2005; Hale et al., 2006; Thorsen and Hale, 2007; Bierman et al., 2009; Phelan et al., 2010; King et al., 2011; Hale, 2014.