Avis H. Cohen

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Eric Lenneberg and Motor ControlAvis H. Cohen1. PreambleI began my graduate career in 1970. I was somewhat familiar with Eric Lenneberg,having met him during an event for faculty in Psychology and Neuroscience—thefields in which I was interested at the time. He had just arrived at Cornell, as hadI, and he didn’t have many other graduate students at that time. I chose him as mygraduate faculty advisor. He directed me toward the study of the development ofmotor control, one of his fields of interest (cf. Lenneberg’s classic, Biological Foun-dations of Language, 1967). His other students were urged to study the developmentof language, in which he was most well known. These students went with Eric toNew York to study patients with aphasia, while I stayed behind at Cornell in Ithaca,with my young children. That ended up suiting me well!When I began graduate school, I was unsure of the direction or level I wished toattain. This was the 1960s and women were not particularly accustomed to gradu-ate school or aiming high, especially if already married with children, which I was.My husband was a faculty member in the Cornell Mathematics Department, andour children were quite young: one was six and one was four. Eric Lenneberg, whohad just begun his time as a faculty member at Cornell University, had participatedin a forum I organized for theoreticians of science, and was the only faculty memberof neuroscience I knew at all well, since he had participated in the forum.My thesis, when finally completed also included results of a project done afterEric’s death with Professors Carl Gans, University of Michigan, and Farish Jenkins,Harvard University, on rat muscle activity during running. Both sets of results wereintegrated into my dissertation on rat locomotion, unfortunately, with ProfessorGans as my advisor and without Eric on my committee.As a post-doctoral fellow, I remained at Cornell for a few years with fundingfrom a National Institutes of Helath (NIH) grant, which fortunately, I was able toobtain independently. At that point I also became interested in mathematical mod-eling of the phenomena on which I was working, another area that Eric had urgedme toward and about which he was enthusiastic. This resulted in my most citedpublication: Cohen, Holmes & Rand (1982). It has been perhaps my most impor-tant publication and the fact that it was and still is being widely cited is a testamentto its importance in establishing theoretical neuroscience.After this work, which was completed early with two mathematical colleagues,Philip Holmes and Richard Rand, both professors at Cornell at that time, I contin-ued doing research in my own laboratory, also at Cornell. I chose the detailed studyISSN 1450–3417Biolinguistics xx: 481–485, 2017http://www.biolinguistics.eu482 Biolinguistics F Forum Fof the production of spinal waves of neural activity as seen in fish swimming as mytopic, employing electrophysiological techniques I had learned from Sten Grillnerin Sweden while doing post-doctoral work there immediately after completing mythesis. The experimental model I kept relying on I had chosen as a post-doctoralstudent in Grillner’s laboratory prior to returning to Cornell, namely the lampreyspinal cord (Cohen & Wallén 1980). I continued modeling with Philip Holmes andanother former Cornell former graduate student, Tim Kiemel. It is this field inwhich I worked happily and productively until my retirement in August 2013.You might wonder what the link was between the development of languageand motor control—and fish swimming? In fact, the link is very complex, but clear.Speech production is a motor process, albeit difficult to study in precise detail, butinteresting nonetheless. For example, apraxia of speech and some forms of aphasiaare conditions which rob you of the ability to communicate, to speak, or even uselanguage. They can affect your ability to speak, write, and understand language,both verbally and/or in its written form. This can occur either following a strokeor head injury, as well as following other injuries that impact the parts of the brainthat are involved in speech production and language processing. Aphasia is fieldof study that has a long history, almost as long as the field of speech production ifnot longer. Not being an expert, myself, I leave that to others to elaborate. My taskhere is to elaborate a bit on the field of motor control, how Eric led me to it, to whatpurpose and to what effect.2. How did Eric lead me to motor control?Eric suggested that the area of motor control was often neglected, but was ex-tremely important, as it was foundational of all activities, such as speech produc-tion and any other type of movement. He would be unable to assist me very much,but would do all he could. I also found that others in the department could behelpful. So I was off and running on motor control! Unfortunately, it was shortlyafter this decision, that Eric died, so he did not accompany me on this part of thejourney.Shortly after starting graduate school, and after Eric’s death, I went with myhusband to University of Michigan for the semester, where I found Dr. Carl Gans.He helped me move ahead on my dissertation work with some experiments on rats(Cohen & Gans 1975), plus he really enabled me to dig deeply into motor control,since that was his area of specialization. Around that time, I also took a short tripto Harvard to allow me to incorporate into my thesis work, X-ray cinematographywith Professor Farish Jenkins. For this I put white rats into a specially redesignedrunning wheel with a plastic side wall to allow the X-ray beams to reach the run-ning rats. The contraption worked well, and we made some great images of run-ning rat skeletons (Cohen 1979).As a post-doctoral fellow at Cornell I had one other diversion. This one took metoward mathematical description of my work, or theoretical neuroscience, anotherarea that had been important to Eric and to which he would have been happy Iembarked upon. Fortunately, I had close ties to the Department of Mathematics, asmy husband is a mathematician (Marshall Cohen, a topologist at Cornell in thoseyears). A couple of his colleagues, Philip Holmes and Richard Rand worked withBiolinguistics F Forum F 483me to perform a theoretical dynamical systems analysis of rhythmic movementssuch as locomotion or swimming. This resulted in perhaps my most important,and certainly my most cited paper, already mentioned above, co-authored withPhilip Holmes and Richard Rand who were in Theoretical and Applied Mechanicsat Cornell at that time (Cohen, Holmes, & Rand 1982). The paper also helped oneto understand the movement that I was beginning to study: swimming of a veryprimitive fish-like vertebrate, the lamprey, which is the animal at the base of thevertebrate tree. It lacks bones and cartilage, the latter only appears later in sharks.3. What is motor control and why is it important?Motor control has been defined in many ways. My definition: motor control is themeans by which organisms coordinate and activate their muscles to perform anymovement . This requires the integration of sensory information from the body ofthe organism as well as with its environment. The organism must determine theappropriate set of muscle forces to generate the desired movement or action. To dothis, there must be cooperative interaction between the central nervous system andthe musculoskeletal system. Thus, sensory input must be available to provide thecurrent status of the organism in its environment; it must also be able to provide theimpact of any action that is performed. The motor system must be able to utilizethis information, and respond appropriately.4. Where it all led me and how it linked back to the theory of motor controlMy thesis from Cornell was a variation on a project begun by Roger Sperry in 1942(Sperry 1945a, b). He cross innervated muscles to determine if they maintain theirfunctional identity if connected to a new functional destination. That is, if the nerveto a flexor is connected to an extensor, will it continue to activate the muscle at thesame time as it did originally. Sperry did it after removing all the other neighboringmuscles and their nerves, thereby removing the possibility of their being feedbackregarding how their activity is stretching and contracting as compared to the nor-mal activity. I did the same thing, but left all other innervation intact, includingthe sensory nerves to muscle. This had the disadvantage that if I wanted to knowwhen the muscle was activated, I was required to record its activity. This I did withelectromyography of the relevant muscles, and I found that, indeed, the nerve con-tinued to be activated as it usually did, even though it now was attached to a newmuscle. However, it was impossible to determine what the nerve was functionallyachieving. This I was able to do in normal animals by using X-ray cinematographyof the rats moving in running wheels with a plastic side replacing the wire parti-tions normally present (Cohen & Gans 1975). However, in animals with crossedinnervation, it was not possible. So, the result described in my thesis remainedlargely indeterminate. I ended up calling this resulting paper, colloquially as: ‘Mylife as short communication . . . ” (Cohen 1978).Eric had sent me on the road to neuroscience, since he had a joint appointmentin the Departments of Biology and Psychology, and I was in Biology (which, at thattime, was actually still called Zoology). He gave very little guidance, which suited484 Biolinguistics F Forum Fme fine. Helen Neville, another student of Eric’s, and I became good friends, andshe helped me navigate the field.As a consequence, I moved on in related but less complicated directions. In par-ticular, I was determined to keep things simple and determinant. My next prepa-ration was the spinal cord of a primitive vertebrate, the lamprey, an animal at thebase of the vertebrate tree. The spinal cord is clear, fully formed and easily removedfrom skin and muscle for monitoring and manipulating in vitro. What more couldI ask? This work was begun with Dr. Sten Grillner at the Karolinska Institute onan NIH post-doctoral fellowship, and continued with Dr. Carl Rovainen and hisstudent Jim Buchanan (Buchanan & Cohen 1982) in St. Louis at Washington Uni-versity.After this short stint as a post-doctoral fellow with Dr. Rovainen I returnedto Cornell, where my husband was teaching. The university provided me with alab after I obtained an NIH grant to further study the lamprey spinal cord. Aftersome time on my own at Cornell, I obtained a faculty position at the University ofMaryland, College Park. Once there, it was relatively smooth sailing!Using the simple lamprey spinal cord, activated either chemically (the work be-gun with Carl Rovainen) or neurally from attached brain activation (much later,done on my own), I was able to specify the impact of the various forms of activa-tion on the lamprey spinal cord (Cohen et al. 1996). Thus, I was able to demonstratethe output of the “central pattern generator” for locomotion in basal vertebrates.Importantly, it was very straightforward. The spinal cord when activated chemi-cally produces a beautiful traveling wave of motor bursts that by themselves canproduce the pattern of traveling waves of the fish as it moves through the wa-ter. Impressively, the traveling wave under even this condition has the proper de-lays between adjacent segments, and the strict alternation between the two sides(Buchanan & Cohen 1982). This simple pattern, we showed much later with activa-tion of a theoretical model or robotic animals (Leftwich et al. 2012), produced theproper movement seen in lampreys as they swim naturally. Yes, the brain stimula-tion could alter the pattern in very complex ways (Cohen et al. 1996), as presumablyneeded, but when swimming steadily, the lamprey could swim perfectly with sim-ple spinal cord activation, and the simple lamprey spinal cord alone produced thebasics all by itself.In 2005, the Japanese invited me to help them develop motor control, what theycalled “mobiligence” or smart movement by intelligent design. Their goal was thedevelopment of smart robots. So, I spent a month in Japan traveling between re-searchers giving lectures on motor control. After my departure, they did, indeed,do some beautiful work on mobile robots, some inspired by my visit (Kimura,Fukuoka & Cohen 2006) and a great deal from their own invention.5. ConclusionIn a nutshell, that is my output during my experimental years in the lab. I also con-tributed to the literature with Neural Control of Rhythmic Movements in Vertebrates,a collection of articles by distinguished scholars in the field (Cohen, Rossignol &Grillner 1988). Lastly, I would like to say that Eric’s sensitivity and insights helpedto guide me through my intellectual journey, and I remain eternally grateful to him.Biolinguistics F Forum F 4856. ReferencesBuchanan, James T. & Avis H. Cohen. 1982. Activity of identified interneurons, mo-toneurons, and muscle fibers during fictive swimming in the lamprey and theeffects of reticulospinal and dorsal cell stimulation. Journal of Neurophysiology47, 948–960.Cohen, Avis H. 1978. Functional recovery following cross-innervation of antago-nistic forelimb muscles in rats. Acta Physiologica Scandinavica 103(3), 331–333.Cohen, Avis H. 1979. Relationship between forelimb coordination and movementasymmetries during fast gaits, canter and gallop. Brain Research 164, 325–356.Cohen, Avis H. & Carl Gans. 1975. Muscle activity in rat locomotion: Movementanalysis and electromyography of the flexors and extensors of the elbow.Journal of Morphology 146, 177–196.Cohen, Avis H . & Peter Wallén. 1980. The neuronal correlate to locomotion in fish:“Fictive swimming” induced in an in vitro preparation of the lamprey spinalcord. Experimental Brain Research 41, 11–18.Cohen, Avis H., Philip J. Holmes & Richard H. Rand. 1982. The nature of thecoupling between segmental oscillators of the lamprey spinal generator forlocomotion: A mathematical model. Journal of Mathematical Biology 13, 345–369.Cohen, Avis H., Serge Rossignol & Sten Grillner (Eds.). 1988. Neural control ofrhythmic movements in vertebrates. New York, NY: Wiley.Cohen, Avis H. , Lan Guan, J. Harris, Ranu Jung. & Tim Kiemel. 1996. Interactionbetween the caudal brainstem and the lamprey central pattern generator forlocomotion. Neuroscience 74(4), 1161–1173.Kimura, Hiroshi, Yasuhiro Fukuoka & Avis H. Cohen. 2006. Adaptive dynamicwalking of a quadruped robot on natural ground based on biological con-cepts. The International Journal of Robotics Research 26, 475–490.Leftwich, Megan C., Eric D. Tytell, Avis H. Cohen & Alexander J. Smits. 2012. Wakestructure behind a swimming robotic lamprey with a passively flexible tail.Journal of Experimental Biology 215, 416–425.Lenneberg, Eric H. 1967. Biological Foundation of Language. New York, NY: Wiley.Mobiligence: Symposium on learning through motor action. Sapporo, Japan, De-cember, 2005Sperry, Roger W. 1945a. The problem of central nervous reorganization after nerveregeneration and muscle transposition. The Quarterly Review of Biology 20,311–369.Sperry Roger W. 1945b. Restoration of vision after crossing of optic nerves and aftercontralateral transplantation of eye. Journal of Neurophysiology 8, 15–28.Avis H. CohenUniversity of MarylandDepartment of Biology andInstitute for Systems ResearchCollege Park, MD 20742United States of Americaavis@umd.edu

Eric Lenneberg and Motor Control

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Eric Lenneberg and Motor Control

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