Welcome to the Edwards Lab!

Neuroscience Institute
   Georgia State University

850 Petit Science Center
   Atlanta, GA 30303
   Tel: (404) 413-5394 (office)
   Tel: (404) 413-5357 (Lab)

FAX: (404) 413-5446
   email: dedwards@gsu.edu

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People

Photo Gallery

Current Research
Neuro-Robotics
Reverse-Engineering an Animal

AnimatLab

Past Research

Dominance Hierarchy Formation
Synapses, Serotonin and Social Status
News Accounts
"Science Bits"
References
Coincidence Detection
Growth and Neuronal Integration

Publications
List of papers
Abstracts of recent papers

Programs and Research Centers
Neuroscience at GSU

Teaching
Neur 8010
Bio 3840

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People

Donald H. Edwards (Regents' Professor)

David W. Cofer (Postdoc)

Giselle Linan-Velez (Ph.D. Student)

Eric Randall (Ph.D. Student)

Bryce Chung (Ph.D. Student)

Maryanne Dos Santos (M.S. Student)

Uzma Tahir (Undergraduate)

Lab Alumni

Undergraduates

Marjorie Sen (Emory University)

Fadi Issa (Georgia State University)

Daniel Adamson (Paidea School, Atlanta)

Eric James (St. Johns University, NY)

Katie McAlister (Swarthmore College)

Aaron Miller (Oberlin College)

Catherine McCurdy (Georgia State University)

M.S.

Sharon Phillips (Beall), M.S. 1986 Currently: MD Pediatrics, Augusta, GA

Rodney Hillis, M.S. 1988

Jiangyan Shi, M.S., 1999

Lisa Blumke, M.S., 2008 Currently: Instructor Biology, Georgia Highlands College

Ph.D.

Dr. Ted W. Simon, Ph.D. 1988 Currently: US EPA

Dr. Shih-Rung Yeh, Ph.D., 1996; Postdoc: 1996-1998 Currently Assoc. Prof. Biology National Tsing-Hua University, Taiwan

Dr. Steven Versteeg Ph.D. student, Univ. Melbourne, 2004; Dissertation under my direction, Currently: Research Staff, CA Labs, Melbourne, Australia

Dr. Cha-Kyong Song Ph.D., 2006) Currently postdoc, Ewha Women’s University, Seoul, Korea

Dr. Nadja Spitzer, Ph.D. 2006. Postdoc, 2007-2007; Currently, Postdoc, Dept. Biology, Marshall Univ., Huntington, W.Va.

Dr. Barbara E. Musolf, Ph.D. 2007 Currently: Assoc. Professor of Biology, Clayton State University, Georgia.

Dr. Fadi A. Issa, Ph.D. 2008. Currently postdoc, Department of Physiology, UCLA School of Medicine.

Dr. David Wayne Cofer, Ph.D. 2009 Currently postdoc in this lab.

Postdoctoral Associates:

Dr. Esther M. Leise, Postdoc: 1989-1990 Currently: Prof. of Biology, UNC Greensoboro

Dr. Peri Nagappan, Postdoc: 1990-1994 Currently with the Morehouse School of Medicine

Dr. Marc Weissburg, Postdoc: 1994 Currently: Prof. of Biology, Georgia Institute of Technology

Dr. Clifford Opdyke, Postdoc: 1994-1995 Currently: Georgia Environmental Protection Division

Dr. Linda Anderson, Postdoc: 1995-1996

Dr. Shih-Rung Yeh, 1996-1998 Currently Assoc. Prof. Biology National Tsing-Hua University, Taiwan

Dr. Joanne Drummond, Postdoc: 1996-1998 Currently with GlaxoSmithKline Australia

Dr. Jens Herberholz, Postdoc: 1999-2005 Currently: Assist. Prof. Psychology, Univ. Maryland, College Park

Dr. Brian Antonsen, Postdoc: 1999-2007 Currently: Assist. Prof. Biology, Marshall Univ., Huntington, W.Va.

Dr. Jeffrey Triblehorn Postdoc: 2003-2006 currently: Assist Prof. College of Charleston, Charleston, SC

Dr. Nadja Spitzer, Postdoc: 2007-2007; Currently: Postdoc, Dept. Biology, Marshall Univ., Huntington, W.Va.

Dr. Fadi A. Issa, Postdoc, 2008 Currently postdoc, Department of Physiology, UCLA School of Medicine.

Dr. David W. Cofer, Postdoc: 2009-2011.

Technicians

Mr. Christopher Mims (Tech. 2001-04) Currently: Editor, Scientific American.com

Ms. Elizabeth DeGoursac (Tech. 2002-03): Currently: Emory Univ. Neuroscience Grad. Prog.

Ms. Laurel Johnstone (Tech. 2000-06)

Photo Gallery

Current Research: Neuro-Robotics

Reverse-Engineering an Animal

We use a "reversed-engineering" approach to discover how animals work. We first study the behavior, anatomy, and physiology of an animal to determine how its parts fit together and interact. We then build computer models of these parts, including some or all of the body and the nervous system, that capture their key properties that allow them to function. We then put the models together in an overall model of the animal, place it in a virtual Newtonian world, and then test it to see whether the model's behavior resembles that of the animal, and how the its different parts contribute to the behavior.

AnimatLab AnimatLab is a Windows-based neur-robotic simulator developed collaboratively by David Cofer, Donald Edwards and our colleagues at GSU and St. Andrews University, Scotland. We have used it to study human arm flexion, locust jumping, and crayfish escape, posture, and walking. AnimatLab has three interactive components: a graphical user interface (GUI) that enables model building and data graphing, solvers for the neural circuit and biomechanics simulations, and a 3-D interactive graphical display of the behavior of the model in the virtual Newtonian world.

B

AnimatLab is open-source and freely available at http://www.animatlab.com, together with 50 video tutorials and a software developer kit.

Arm Flexion Sensory feedback from muscle spindles and other receptors mediates reflexes that stabilize the body against outside perturbations. During voluntary limb movement, the reflex circuitry has to be prevented from interfering with the movement while also assisting the limb to reach the new position, stabilized against additional perturbation. We studied this using an AnimatLab model of human arm flexion (Fig. 1, Movie 1), and described it in Cofer et al., 2010a.

Locust Jump The neural circuitry and biomechanics of kicking in locusts have been studied to understand their roles in the control of both kicking and jumping. It had been hypothesized that the same neural circuit and biomechanics governed both behaviors, but this hypothesis was not testable with current technology. We built a neuromechanical model according to current knowledge of the leg biomechanics and the anatomy and physiology of the neural circuit that produced kicking (Fig. 2). When excited appropriately, the circuit produced model jumping and kicking behaviors (see Fig. 3, Movie) that we compared to published results of real kicks and jumps and to the kicking and jumping behavior of 5 live locusts. We found that the model replicated the live data for both kicks and jumps in all particulars. This confirmed that the kick neural circuitry can produce the jump behavior. This is described in Cofer et al., 2010b and Cofer et al., 2010c.

Crayfish We are interested in how the nervous system controls the behavior of animals. To this end, we have focused on the crayfish, a small invertebrate that has been extensively studied for the past 100 years (see www2.biology.ualberta.ca/palmer/thh/crayfish.htm for Thomas Huxley's classic description), and has a large behavioral repertoire and a relatively small nervous system. crayfish live primarily underwater, in streams, rivers, ponds and swamps, but they also venture out on land when it's wet, sometimes migrating considerable distances overland between watersheds. They dig multichambered burrows in mud banks for homes, and live and have their babies in them. They often live in communities of other crayfish, and compete with them for food, shelter, and mates. They have hierarchical social relationships based on their social interactions with each other and on their size and personality. They forage for food on land and underwater, eating plants and preying on other animals. Our research in the past has concerned the escape behavior of crayfish, the circuits that produce escape, and how they and the behavior is modulated by serotonin and by changes in the animal's social status. Descriptions of this research are found below.

Crayfish Posture and Walking We have been studying the control of posture and locomotion in crayfish, with particular attention to the role of sensory feedback from proprioceptors like the coxa-basipodite chordotonal organ (CBCO), which measures the angle and rate of change of the angle of the depression-levation joint of the legs. When crayfish walk, each leg elevates and promotes during the swing phase, and then depresses and remotes during the stance phase. Depressor motorneuron bursts alternate with anterior levator motorneuron bursts; the posterior levator overlaps both, beginning during the depression phase (Fig. 4). A movie of the animal walking, the motor nerves firing, and plots of the joint angles of the 5th left leg can be seen here: Crayfish Walking.

To start, have constructed a 4-legged AnimatLab model of the crayfish based on published descriptions of the animal's anatomy, the origins, insertions, and properties of the walking leg muscles, and the physiology of its sensory and motor neurons (Fig. 5). (A 4-legged model is significantly less complex than an 8-legged model). The rhythmic movements of the legs during walking are governed by a set of central pattern generators (CPGs). Because the precise circuitry that produces the relative phasing of each of the joints in a leg has not been described, we have made up circuitry that does that. We are using the model to study the role of the CBCO in mediating resistance and assistance reflexes during standing and locomotion. As can be seen here (Crayfish Walking Model), the model captures many of the features of crayfish walking.

Past Research

Our primary focus has been on one of the best-understood circuits in any nervous system, the tail flip escape circuit in crayfish.   We have used this circuit and behavior to study a variety of issues, including changes in the brain during social hierarchy formation (Yeh, et al., 1996; Yeh, et al., 1997) (Issa et al., 1999), coincidence detection (Edwards, et al., 1998), and the neural bases for behavioral choice (Edwards, 1991;  see the web-based simulation of our model by Steven Versteeg at the University of Melbourne (http://www.cs.mu.oz.au/~scv/sim/simcray.html).   Many of these results are summarized in a review in Trends in Neurosciences.  We are also interested in understanding the neural bases for behavioral choice (Edwards, 1991;  see the web-based simulation of our model by Steven Versteeg at the University of Melbourne (http://www.cs.mu.oz.au/~scv/sim/simcray.html).  This work was supported by the NSF and by the NIH.

Dominance Hierarchy Formation  Social animals form hierarchies so as to divide resources without unnecessary conflict.  Conflict may occur at the outset, however, when two unfamiliar animals meet, and they are of about equal size and strength.  Then agonistic interactions may escalate to full fighting. Usually these fights are brief, and end when one animal suddenly withdraws.  The new dominant may pursue briefly, so as to 'pound in' the lesson of who won and who lost.  The sudden change in behavior, from fighting to retreat, is indicative of a corresponding change in the brain about which we know very little.  We have found that in crayfish, this change in behavior is reflected in the frequency with which several agonistic behaviors (approach, attack, and offensive tailflip) and several defensive behaviors (retreat, three forms of escape tailflip) are displayed (Herberholz

et al., 2001).  Before the decision to withdraw by one animal, both animals displayed similar patterns of attack and offensive tailflip, accompanied by very few defensive behaviors.  Suddenly one animal would break contact and initiate a rapid series of tailflips that would carry it away from the dominant.  The tailflips were activated by two different neural circuits, the 'medial giant' and 'non-giant' circuits, that trigger rearward escapes in response to frontal attacks.  The sudden release of these tailflips indicates that the stimulus threshold for activating the circuits must have changed from very high before the decision to withdraw to very low thereafter.  We don't yet know the mechanism for this transition, except to say that both circuits  are under strong inhibitory control; it is likely that one consequence of the decision to withdraw is removal of that inhibition.  Interestingly, the lateral giant circuit (see below), which triggers an upward tailflip escape in response to an attack from the rear, was activated only once during fights between 8 pairs of animals, suggesting that it is inhibited throughout such contests.

Synapses, Serotonin and Social Status.   It has been known for some time that serotonin, a psychoactive neurochemical implicated in the control of mood, aggression, blood flow, and digestion, also affects the response of the lateral giant (LG) neuron (picture at right) in crayfish to its normal sensory inputs (Glanzman and Krasne, 1983).  The LG neuron is excited by a tap on the tail that might occur when the animal is attacked, and it triggers a tail flip escape response that moves the animal quickly away from the stimulus (see picture above).  Recently we found that the effect of serotonin on LG's response depends on the social status of the crayfish (Yeh, et al., 1996; Yeh, et al., 1997).  Serotonin increases the responsiveness of the LG neuron in crayfish that have been isolated for a month or more ("isolates"), and this increase persists for several hours after the serotonin is removed.  In social subordinates, however, serotonin inhibits LG's response, whereas in social dominants, LG's response is increased again.  In these last two, the effects of serotonin persist only as long as the drug is present.
          Social hierarchies form when unfamiliar animals get together (Issa et al., 1999).  The larger animal will usually become the dominant member of the pair, with first choice of all the available resources (e.g., food, shelter), whereas the smaller will become subordinate.  Although the social status of the two animals is decided within the first hour of pairing, usually after a few brief bouts of fighting,  the differences in the effect of serotonin on LG's response take nearly two weeks to develop fully.   Other aspects of the animals' behavior changes gradually during this period as they settle into their new social roles.
        Should the subordinate be reisolated, or should it be re-paired with another subordinate and become dominant to that new animal, the inhibitory effect of serotonin will change to the facilitatory effect characteristic of isolate or dominant animals.   Should a dominant animal be paired with and become subordinate to another dominant animal, the effect of serotonin does not change to that typical of the other subordinates.  Rather it retains its facilitatory character, even after more than a month of subordinate status.  These results suggest that if dominant status is the preferred social state, then  the facilitatory effect of serotonin is a preferred physiological state.
         Many different drugs activate different classes of receptor molecules for serotonin in vertebrates.  When two of these were substituted for serotonin in the crayfish experiments, one had inhibitory effects on LG's response in both dominant and subordinate animals, and the other had facilitatory effects in both animals.  These and other data suggest that the changes in the effect of serotonin following a change in social status resulted from changes in the receptors for  serotonin in the LG neuron.
        This work is significant because it is the first report that a change in an animal's social status can change the population of  molecular receptors for, and the effect of, a neurochemical like serotonin in the nervous system.   In view of this result, it appears likely that the obvious difference in the behavior of dominant and subordinate animals occurs in part because their nervous systems are different, so that serotonin now has different effects in the two animals.  This suggestion is supported by recent behavioral experiments which showed that LG-evoked tail flips become much more difficult to evoke in subordinate crayfish than in dominant crayfish during a fight, when serotonin may be naturally released in the nervous system (Krasne et al., 1997).

News Accounts of this Work. Several press accounts of this work are available.  These include:

• "Status goes to the brain", Science Bits cartoon by Donna Okino, The Boston Globe, March 11, 1996 (on the right).
• "Social Status Sculpts Activity in Crayfish Neurons" by Marcia Barinaga, Science 271: 290-291, (1996).
• "Serotonin and Crabby Behavior" by Christine Folz, Journal Watch for Psychiatry 2(3): 21-22 (1996).
• "Animal Watch:  Chemistry and Status", by Rachel Preiser, Discover, July 1996, p. 34
• "Losers Get an Attack of Nerves", by Alison Motley, New Scientist, 1 February, 1997, p. 15.
• "Crawdad War and Peace: The Nature Cafe Closes Shop"  by Eddie Nickens, in "The Nature Cafe: Discovery Channel Online"
• "Macht geht auf die Nerven", in Focus, 8/1996, p. 130.
• "Social Rank Makes Brain Act Fish", by Ron Haybron, in The Cleveland Plain Dealer, August 20, 1996, p. 7E
• "Time to get up off the couch?; Through the Eighties and Nineties, psychotherapy has reigned supreme.  Now, research suggests much mental illness may have physical origins.  Will the shrink soon be out of a job?  Jerome Burne reports" by Jerome Burne, The Independent (U.K.) April 27, 1997, p. 4.
• "Crayfish fights trigger link to body changes" by Rachel Preiser, Discover Magazine, in The San Diego Union-Tribune, August 7, 1996, p. E-1.
• "Lobster's tale is a salty saga of serotonin and social status" by Tom Siegfried, The Dallas Morning News, 7D, Feb. 16, 1998.

References

· Glanzman, D.L. and Krasne, F.B. Serotonin and octopamine have opposite modulatory effects on the crayfish's lateral giant escape reaction. J Neurosci 3:2263-2269, 1983.

· Krasne, F.B., Shamasian, A., and Kulkarni, R. Altered excitability of the crayfish lateral giant escape reflex during agonistic encounters. J.Neurosci. 17(2):692-699, 1997.
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Coincidence Detection. Coincidence detection is important for functions as diverse as Hebbian learning, binaural localization, and visual attention.  We have found that extremely precise coincidence detection is a natural consequence of the normal function of rectifying electrical synapses (Edwards et al., 1998).  Such synapses open to bidirectional current flow when presynaptic cells depolarize relative to their postsynaptic targets, and remain open until well after completion of presynaptic spikes.  When multiple input neurons fire simultaneously, the synaptic currents sum effectively and produce a large EPSP.  However, when some inputs are delayed relative to the rest, their contributions are reduced by the early EPSP and by postsynaptic current shunts through junctions already opened by the earlier inputs. These mechanisms account for the ability of the lateral giant neurons of crayfish to sum synchronous inputs, but not inputs separated by only 100 msec.  This coincidence detection enables crayfish to produce reflex escape responses only to very abrupt mechanical stimuli.  In light of recent evidence that electrical synapses are common in the mammalian CNS, the mechanisms of coincidence detection described here may be widely used in many systems. (Return to Contents)

Growth and Neuronal Integration.  Neurons must work both when they are small in young animals and when they are larger in adult animals.  The increase in size that neurons experience, however, changes the way in which electrical current flows through them, and so changes they way in which they respond to synaptic inputs.   We have found that two sets of giant neurons, one in cricket and one in crayfish, exemplify two different patterns of neuronal growth that have different effects on neuronal integration.  The medial giant interneurons (MGI) in cricket maintains its response properties as it grows.  It grows approximately uniformly, but such that the diameters of its processes increase as the square of their increase in length (Hill et al., 1994).  The lateral giant (LG) neuron in crayfish becomes more of a low-pass filter as it grows, which causes it to switch input circuits and become susceptible to response habituation.  It grows approximately isometrically (Edwards et al., 1994a, b) .   A cable analysis of these different patterns of uniform growth indicates that, regardless of the initial shape or distribution of active and passive membrane properties, a cell that grows uniformly and with neurite diameters increasing as the square of their increase in length will not change the way voltage is distributed through the cell (Olsen et al., 1996). This "isoelectrotonic" pattern of growth will enable a synaptic potential created at corresponding positions in the small and large cells to evoke identical responses at all other corresponding points in the two cells. Conversely, uniform isometric growth causes the cell to become electrically larger, and to become a low-pass filter.  These analytical results account for the different effects of growth on the two cells, in which MGI grows isoelectrotonically, and LG grows isometrically. (Return to Contents)

Review of this Work.
Marder, Eve   Electrical Synapses: Beyond Speed and Synchrony to Computation.  Current Biology.  (in press)

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Lab Publications (since 1991) (for reprints, contact dedwards@gsu.edu)
Papers (PI, Postdocs, Grad Students, Undergrads, High School Students, and PostGrads are indicated by color highlights)

· Cofer, D., Cymbalyuk, G., Heitler, W.J., and Edwards, D.H. (2010) Neuromechanical simulation of the locust jump. J. Exp. Biol. 213: 160-168.

· Cofer, D., Cymbalyuk, G., Reid, J. Zhu, Y., Heitler, W.J., and Edwards, D.H. (2010) AnimatLab: A 3-D graphics environment for neuromechanical simulations. Journal of Neuroscience Methods. 187(2): 280-288.

· Cofer, D., Heitler, W.J., and Edwards, D.H. (2010) The control of tumbling during the locust jump. J. Exp. Biol. 213: 3378-3387.

· Cattaert D, Delbecque JP, Edwards DH, Issa FA (2010) Social interactions determine postural network sensitivity to 5-HT. J Neurosci 30:5603-5616.

· Edwards, D.H. (2010) Neuromechanical simulation. Frontiers in Behavioral Neuroscience 4. pii: 40.

· Edwards, D.H. (2008) Critical thinking in Biology, in Critical Thinking in College, 2^nd Edition, George W. Rainbolt and Sandra L. Dwyer, eds., pp. 372-375, Thomson Custom Solutions, Mason, OH

· Musolf,B.E., Antonsen, B.L., Spitzer, N., and Edwards, D.H. (2009). Serotonergic modulation of crayfish hindgut Biol. Bulletin. 217(1):50-64

· Edwards, D.H. (2009) Excitation and habituation of crayfish escape. J. Exp. Biol. 212: 749-751.

· Song, C.-K., Johnstone, L.M., Edwards, D.H., Derby, C.D., and Schmidt, M. (2009) Cellular basis of neurogenesis in the brain of crayfish, Procambarus clarkii: Neurogenic complex in the olfactory midbrain from hatchlings to adults. Arthropod Struct. and Dev. 38: 339-360.

· Spitzer, N., Cymbalyuk, G., Zhang, H., Edwards, D.H., and Baro, D.J. (2008) Serotonin transduction cascades mediating variable changes in pyloric network cycle frequency in response to the same modulatory challenge. J Neurophysiol., 99(6): 2844-2863

· Spitzer, N., Edwards, D.H., and Baro, D.J. (2008) Conservation of structure, signaling and pharmacology between two serotonin receptor subtypes from decapod crustaceans, Panulirus interruptus and Procambarus clarkii. J Exp Biol 211:92-105.

· Horner AJ, Schmidt M, Edwards DH, Derby CD (2008) Role of the olfactory pathway in agonistic behavior of crayfish, Procambarus clarkii. Invert. Neurosci. 8(1): 11-18.

· Antonsen, B.L. and Edwards, D.H. (2007) Mechanisms of serotonergic facilitation of a command neuron. J. Neurophysiol. 98:3494-3504.

· Steullet, P., Edwards, D.H. and Derby, C.D. (2007) An electric sense in crayfish? Biol. Bull. 213: 16-20.

· Herberholz, J., McCurdy, C., and Edwards, D.H. (2007) Direct benefits of social dominance in juvenile crayfish. Biol. Bull. 213: 21-27.

· Song, C.-K., Johnstone, L.M., Schmidt, M., Derby, C.D., Edwards, D.H. (2007) Social domination increases neuronal survival in the brain of juvenile crayfish Procambarus clarkii. J. Exp. Biol. 210: 311-324.

· Yong Li, Xiujuan Chen, Saeid Belkasim, Brian Antonsen, and Donald Edwards (2007) “Fuzzy Contour Matching for 3D Partial Retrieval in Neuron XML Image Database,” International Journal of Approximate Reasoning.

· Issa, F.A., and Edwards, D.H. (2006) Ritualized submission and the reduction of aggression in an invertebrate. Current Biology 16: 2217-2221.

· X. Hu, D. Edwards (2006) Context-Dependent Structure Control for Adaptive Behavior Selection, Proc. Workshop on Bio-inspired Cooperative and Adaptive Behaviours in Robots, in co-operation with The Ninth International Conference on the SIMULATION OF ADAPTIVE BEHAVIOR (SAB'06),

· X. Hu, D. H. Edwards (2005) BehaviorSim: A Simulation Environment To Study Animal Behavioral Choice Mechanisms, Proceedings of the 2005 DEVS Integrative M&S Symposium, Spring Simulation Multiconference, San Diego CA, April 2005

· Y. Li, S. Belkasim , Y. Pan , D. Edwards and B. Antonsen (2005) 3D reconstruction using image contour data structure". Conf. Proc. IEEE Eng. Med. Biol. Soc. 3: 3292-3295.

· Edwards, D.H. and Spitzer, N. (2006) Social dominance and serotonin receptor genes in crayfish. Current Topics in Developmental Biology, 74: 177-199.

· Edwards D.H., Herberholz, J. (2006) Crustacean Models of Aggression. In: Biology of Aggression (Nelson RJ, ed), pp 38-61. Oxford: Oxford University Press.

· Song, C.-K., Herberholz, J. and Edwards, D.H. (2006) The effects of social experience on the behavioural response to unexpected touch in crayfish. J. Exp. Biol. 209: 1355-1363

· Antonsen BL, Herberholz J, Edwards DH (2005) The retrograde spread of synaptic potentials and recruitment of presynaptic inputs. J. Neurosci. 25: 3086-3094.

· Spitzer N, Antonsen BL, Edwards DH (2005) Immunocytochemical mapping and quantification of expression of a putative type 1 serotonin receptor in the crayfish nervous system. J Comp Neurol 484: 261-282.

· Herberholz J, Mims CJ, Zhang X, Hu X, Edwards DH (2004) Anatomy of a live invertebrate revealed by manganese-enhanced Magnetic Resonance Imaging. J Exp Biol 207: 4543-4550.

· Sosa, M.A., Spitzer, N., Edwards, D.H., and Baro, D.J. (2004) A crustacean serotonin receptor: Cloning and distribution in the thoracic ganglia of crayfish and freshwater prawn. J. Comp. Neurol. 473 (4): 526-537.

· Herberholz, J., Sen, M.M. and Edwards, D.H. (2004) Escape behavior and escape circuit activation in juvenile crayfish during prey-predator interactions. J. Exp. Biol. 207 (11): 1855-1863.

· Antonsen, B. and Edwards, D.H. (2003) Differential dye-coupling reveals the lateral giant escape circuit in crayfish. J. Comp. Neurol. 466: 1-13.

· Herberholz, J., Sen, M.M., and Edwards, D.H. (2003) Parallel changes in agonistic and non-agonistic behaviors during dominance hierarchy formation in crayfish. J. Comp. Physiol. A. 189: 321-325.

· Herberholz, J., Antonsen, B.L. and Edwards, D.H. (2002) A lateral excitatory network in the escape circuit of crayfish. J. Neurosci. 22: 9078-9085.

· Herberholz, J., Issa, F.A., and Edwards, D.H. (2001) Patterns of neural circuit activation during dominance hierarchy formation in freely behaving crayfish. J. Neurosci. 21: 2759-2767.

· Herberholz, J., Issa, F. A., Edwards, D. H. (2001). Patterns of Neural Circuit Activation and Behavior during Dominance Hierarchy Formation in Freely Behaving Crayfish. J. Neurosci. 21: 2759-2767

· Edwards, D.H., Heitler, W.J., and Krasne, F.B. (1999) Fifty years of a command neuron: The neurobiology of escape in crayfish. Trends In Neurosci. 22(4): 153-161.

· Heinrich, R., Cromarty, S.I., Hörner, M., Edwards, D.H., and Kravitz, E.A. (1999) Autoinhibition of serotonin cells: An intrinsic regulatory mechanism sensitive to the pattern of usage of the cells. Proc. Nat. Acad. Sci. U.S.A. 96: 2473-2478.

· Issa, F.A., Adamson, D.J., and Edwards, D.H. (1999)  Dominance hierarchy formation in juvenile crayfish, Procambarus clarkii.  J. Exp. Biol. 202: 3497-3506.

· Katz, P. S. and Edwards, D.H. 1999  Metamodulation: the control and modulation of neuromodulation. In: Beyond Neurotransmission: Neuromodulation and its importance for information processing, edited by P. S. Katz, Oxford: Oxford University Press, p. 349-381.

· Edwards, D.H. The effects of neuronal growth and social experience on the development of behavioral plasticity. In: The Biology of Early Influences, Ed. F. Johnson, Plenum Press, New York, (in press).

· Edwards DH, Yeh S-R, and Krasne FB. (1998)  Neuronal coincidence detection by voltage-sensitive electrical synapses. Proc. Nat. Acad. Sci. USA 95: 7145-7150.

· Heitler W.J. and Edwards, D.H. (1998) Effect of temperature on a voltage-sensitive electrical synapse in crayfish. J. Exp. Biol. 201: 503-13

· Edwards, D.H. and Kravitz, E.A. (1997) Serotonin, social status and aggression.  Curr. Opin. Neurobiol. 7: 811-819.

· Hörner M, Weiger WA, Edwards DH, Kravitz EA (1997) Excitation of identified serotonergic neurons by escape command neurons in lobsters.  J Exp Biol  200: 2017-33

· Yeh S-R, Musolf BE, Edwards DH (1997) Neuronal adaptations to changes in the social dominance status of crayfish. J Neurosci. 17:697-708.

· Olsen O, Nadim F, Hill AA, Edwards DH (1996) Uniform growth and neuronal integration. J Neurophysiol 76: 1850-7

· Yeh S-R, Fricke RA, Edwards DH (1996) The effect of social experience on serotonergic modulation of the escape circuit of crayfish. Science 271:366-369.

· Edwards DH, Fricke RA, Barnett LD, Yeh S, Leise EM (1994) The onset of response habituation during the growth of the lateral giant neuron of crayfish. J Neurophysiol 72:890-898.

· Edwards DH, Yeh S-R, Barnett LD, Nagappan PR (1994) Changes in synaptic integration during the growth of the lateral giant neuron of crayfish. J Neurophysiol 72:899-908.

· Hill AAV, Edwards DH, Murphey RK (1994) The effect of neuronal growth on synaptic integration. J Comput Neurosci 1:239-254.

· Edwards DH (1991) Mutual inhibition among neural command systems as a possible mechanism for behavioral choice in crayfish. J Neurosci 11:1210-1223.

· Edwards DH, Heitler WJ, Leise EM, Fricke RA (1991) Postsynaptic modulation of rectifying electrical synaptic inputs to the LG escape command neuron in crayfish. J Neurosci 11:2117-2129.

· Heitler WJ, Fraser K, Edwards DH (1991) Different types of rectification at electrical synapses made by a single crayfish neurone investigated experimentally and by computer simulation. Journal of Comparative Physiology A 169:707-718.
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GSU Neuroscience

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last modified: 4/24/06

Comments? contact: dedwards@gsu.edu