Core Faculty Profile

Mitra Hartmann

Associate Professor, Joint appointment with Mechanical Engineering
PhD, Integrative Neurobiology, California Institute of Technology

Northwestern University
2145 Sheridan Road, E310
Evanston, Illinois 60208-3107

Phone:  (847) 467-4633
Fax:  (847) 491-4928
E-mail: m-hartmann@northwestern.edu

Website(s):  http://www.mech.northwestern.edu/hartmann

Research Interests

• How animal biomechanics enables efficient movement and active sensing
• How animals represent 3-dimensional spatial information using spatiotemporal variations in activity across 2-dimensional receptor sheets
• how the construction of hardware and computer models of animal movement and sensing can provide insights into the underlying organization of the nervous system.

Current research in the laboratory concentrates specifically on the sensory modulation of behaviors involving rhythmic movement, because rhythmic movement, and perturbations to it, is relatively easy to observe, measure, and quantify. We work with two model systems that use sensory feedback to modulate fundamentally periodic activity: rat whisking behavior, and bipedal locomotion. By studying how sensory feedback affects periodic motion, we hope to gain insight into the continuous, recursive interplay between sensory and motor signals during active behaviors. Here we describe some aspects of"; the first model system: rat whisking behavior.

Rats, as nocturnal, burrowing animals, use rhythmic movements of their whiskers (vibrissae) to tactually explore their environment and nearby objects. Using their whiskers, rats can extract information about the spatial properties of objects, including size, shape, and texture. Our laboratory uses the rat whisker system as a model to study sensory acquisition and the sensory modulation of rhythmic movement. The long-term goal is to gain insight into the algorithms by which the nervous system encodes sensory information to efficiently construct spatial representations of objects.

Current projects in the laboratory include:

1. Experimental and theoretical characterization of the flexural (bending) properties of rat whiskers under both static and dynamic conditions. The goal is to develop a quantitative description of how whiskers interact with objects, and thus what sensory information may be transduced back to receptors at the base of the whisker.
2. Characterization of the relationship between head and whisker movements. We are using high speed videography to determine how head and whisker movements might be coordinated to enhance the ability of the rat to extract consistent spatial information.
3. Construction of an artificial rat "head and whiskers" in hardware, in part to test hypotheses generated in projects (1) and (2). The goal is to develop an active tactile sensing system that can accurately extract information about an object's spatial properties, for example, curvature.
4. Investigation of how the cancellation of expected sensory feedback can aid in sensory acquisition and discrimination.

Selected Publications

1. Solomon JH and Hartmann MJ (2006) Nature 443:525.
   
   
2. Towal, RB and Hartmann MJ (2006) Right-left asymmetries in the whisking behavior of rats anticipate head movements, Journal of Neuroscience.
   
   
3. Reed K, Peshkin MA, Hartmann MJ, Grabowecky M, Patton J, and Vishton PM, Haptically linked dyads: Are two motor control systems better than one? (2006) Psychological Science. 17:365-367.
   
   
4. Lu H, Hartmann MJ, and Bower JM (2005) Correlation between Purkinje cell unit activity and granule cell layer field potentials: an in vivo extracellular study. Journal of Neurophysiology. 94:1849-1860.
   
   
5. Hartmann MJ, Johnson NJ, Towal RB, and Assad C (2003) Mechanical characteristics of rat vibrissae: Resonant frequencies and damping in isolated whiskers and in the awake behaving animal. Journal of Neuroscience, 23:6510-6519.
   
   
6. Lewis MA, Etienne-Cummings R, Hartmann MJ, Xu ZR, and Cohen AH (2003)An in silico central pattern generator: silicon oscillator, coupling, entrainment, and physical computation. Biological Cybernetics 88:137:151.
   
   
7. Hartmann MJ (2001) Active sensing capabilities of the rat whisker system. Autonomous Robots, 11:249-254.
   
   
8. Hartmann MJ and Bower JM (2001) Tactile responses in the granule cell layer of cerebellar folium crus IIa of freely-behaving rats. Journal of Neuroscience, 21: 3549-3563.
   
   
9. Hartmann MJ and Bower JM (1998) Oscillatory activity in the cerebellar hemispheres of unrestrained rats. Journal of Neurophysiology. 80: 1598-1604.