1. Project: Frog Cryoplane

Motor primitives in spinal cord may form a significant substrate for therapies based on neuroengineering, brain machine interfaces and directed transplantation or neural bridging.

How such modularity depends on or is emergent from the biomechanical and sensory structure is an important open question. Of particular concern is the role of sensory feedback. Strong assumptions about spindle gamma drive must be made in mammals, because gamma fusimotor drive uncouples the control of feedback from the motor outflow. These control issues, posed in mammalian motor control, do not arise in frogs by nature of their simpler purely beta-fusimotor neural organization. In frogs, proprioception therefore can be fully modeled. Significant physiological and theoretical advances may be made by ‘leveraging’ such simplicity.

To understand motor primitives better, we are building a detailed model of the frog limb and jaw control. We use these to examine how beta spindle proprioception may be optimally integrated to control motion, and also how it may contribute to selection and organization of motor primitives.

We use cryoplane microscopy to develop high resolution reconstructions of a body part. Select structures may be outfilled. For example, to obtain spindle distributions in the legs the lumbar dorsal roots are outfilled with Lucifer yellow. We are also exploring obtaining sarcomere measures from the frozen tissue with laser interferometry. The data are used in a range of models. These vary from simpler Visual Nastran based and SIMM models, to a Cosserat strand utilizing muscle model being built in collaboration with colleagues at UBC in Canada to predict population spindle data in compound stranded muscles with realistic wrapping interactions.

Supported by DUCOM Neuroengineering initiative, and DU Major Research Initiative, NSF DBI 0352421 to JN and NIH NS40412 to SFG

1.1 Collaborators:

CRYOTOME IMAGING-FLUORESCENT AND BRIGHT FIELD IMAGING: Jonathan Nissanov’s Lab

Jonathan Nissanov: Associate Professor, Dept. of Neurobiology and Anatomy, Drexel University, PA

Louise Bertrand: Research Specialist, Histologist

Song Liu: Technician

PREY STRIKE- HEAD AND NECK EMG: Kiisa Nishikawa’s Lab

Kiisa C. Nishikawa: Regents' Professor, Dept. of Biological Sciences, Northern Arizona University, AZ

Jenna Monroy: Research Postdoc

Theodore A. Uyeno : Research Postdoc

BIOMECHANICAL MODELLING- MUSCLE STRAND MODEL: Dinesh K. Pai’s lab

Dinesh K. Pai: Professor and Tier 1 Canada Research Chair, Department of Computer Science, University of British Columbia, Canada

Shinjiro Sueda: Doctoral Student

1.2 Poster 1: Introduction to the project

1.3 Image Gallery