Anne Bekoff, Ph.D. - US grants

The long-term goal of the proposed research is to gain further understanding of the neural mechanisms underlying the ontogeny of coordinated behaviors. Specifically, the present study is designed to extend our understanding of the development of the neural circuitry that generates walking. This study will examine the hypothesis that the neural circuitry that is used to produce leg movements during early embryonic motility is subsequently used during hatching at the end of embryonic development and then in walking and other locomotory behaviors in the post-hatching chick. Chicks will be used for these studies because, in contrast to mammals, the embryonic stages are readily accessible to experimental manipulation and yet the relevant aspects of neural development appear to proceed similarly in chicks and mammals. In order to determine whether or not the same pattern generating circuitry is used to produce embryonic motility, hatching and walking, the leg motor output patterns typical of each behavior will first be characterized using quantitative analysis of electromyogram recordings in order to identify the similarities and differences. Then the roles of descending control, sensory input and intrinsic properties of the circuitry in accounting for the differences between the motor output patterns will be analyzed. Thus the proposed study will address the issues of 1) the role of multi-use pattern generators during development, 2) the role of sensory and descending input in modulating pattern generator output and 3) the subunit structure of pattern generating circuits. The data generated will provide insight into the neural mechanisms involved in the development of walking and will significantly enhance our understanding of the development of coordinated behaviors in general.

The long term goal of this research is to gain a better understanding of the mechanisms involved in the development of coordinated motor behaviors. Specifically, this project addresses the transitions in behavior seen during the perinatal period. The studies are designed to explore the role that sensory signals play In shaping the behaviors that occur during this period and in initiating the transitions among them. In addition,-the relationship among these behaviors will be examined. For example, how does altering a behavior at one stage affect the development of other behaviors at later stages? The answers to these questions have Important implications for our understanding of behavioral development in both normal and compromised human infants. This proposal focuses on the perinatal period in chicks, which encompasses the last 20% of the embryonic period (days E17 to E21), hatching (day E21/PO), and the early postnatal period (days PO to P2). Specifically, the transition (1) from Type I embryonic motility, the most common type of embryonic behavior, which appears jerky and uncoordinated, to hatching, a highly stereotyped behavior used to gain release from the egg and (2) from hatching to walking will examined. The chick is an ideal model system for dealing with these questions because the embryo is easily accessible to both observation and experimental manipulation throughout the perinatal period. As in human fetuses, the perinatal period involves a transition from an aquatic to a terrestrial existence, from a confined to a more open environment, and major changes in the kinds of sensory information available. To characterize the perinatal motor behaviors, detailed analyses of kinematic recordings will be used to quantify movements and electromyographic (EMG) recordings will be used to quantify the motor output of the nervous system during late embryonic (Specific Aim 1) and early postnatal (Specific Aim 4) stages. Experimental manipulations of sensory input will be carried out to determine the role of sensory context in the expression of the embryonic behaviors (Specific Aim 2). Because there is evidence that hormonal or other pharmacological signals may play an important role in the initiation of birth and hatching, this will be explored further (Specific Aim 3). Finally, the effects of manipulations of behavior at one stage of development on later development of normal, adaptive behaviors will be examined (Specific Aim 5).