Browsing by Author "Marshall, Timothy R."

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    A comparison of techniques for identifying recurrent patterns of behavioral state in neonates
    Marshall, Timothy R. (Virginia Polytechnic Institute and State University, 1985)
    While a variety of researchers have identified periodic recurrences in infant behavioral state with various time-series techniques, the appropriateness of techniques which identify periodic recurrences in all infants at all ages have been questioned. The purpose of this study was to compare the utility of four time-series techniques used in the analysis of periodic recurrences in the behavioral state of 21 newborns during a 2 hour observation period. For quiet sleep, active sleep and awake states the period length of the major rhythm was estimated by 1) binary spectrum analysis, 2) binary autocorrelation, 3) renewal time analysis, and 4) kappa analysis. Repeated measures analysis of variance showed that the period lengths identified by renewal time analysis were significantly shorter than those identified by the other three techniques for quiet and active sleep. Further, the kappa analysis and binary autocorrelation showed that awake states were significantly shorter than both active sleep and quiet sleep. Pearson product-moment correlations showed that the relation between the periods for a given state identified by each analysis ranged from .01 to .83. The results indicate that 1) renewal time analysis is more sensitive to state interruptions than the other techniques, 2) awake states may have a different period length than either quiet sleep or active sleep, and 3) although the four techniques identified state recurrences in almost all of the neonates, only a smaller subgroup of neonates displayed a pattern of technique agreement that would indicate a clearly rhythmic pattern of states.
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    Holding and rocking the full-term neonate: the immediate and residual effects on behavioral state and heart rate
    Marshall, Timothy R. (Virginia Polytechnic Institute and State University, 1989)
    This study explored infants' immediate and residual responses to holding and rocking, and how these responses relate to previously proposed mechanisms to explain long term benefits found when infants are repeatedly exposed to tactile and vestibular stimulation. This form of stimulation has been proposed to increase infants' ability to control and organize l) their behavioral state, 2) their arousal and autonomic functioning, or 3) that there is no clear relationship between immediate responses and long term benefits. Behavioral state and heart rate were collected on 40 infants who were randomly assigned to either a control group where infants were briefly repositioned twice but otherwise lay undisturbed for 90 minutes or an experimental group where infants were held and rocked for 30 minutes during the middle of a 90-minute observation. Results of analyses showed that, when infants were held and rocked they 1) displayed a lower Heart Rate Mean and Standard Deviation, 2) displayed a lower Mean Heart Rate During Active Sleep, 3) spent less time in a FussCry State, 3) were less likely to cry continuously, and 4) displayed nominally Smoother State Transitions and greater Stability Within States. Following the cessation of the rocking stimulus infants in the Experimental Group l) displayed a lower Mean Heart Rate, 2) displayed a lower Mean Heart Rate while in a Quiet Alert State, 3) were more likely to spend some time in a Quiet Sleep State, and 4) were less likely to cry continuously. In addition, all infants displayed Smoother State Transitions and greater Stability Within States during the first 30 minutes than during the final 30 minutes of the observation. Finally, across the 90-minute observation, the infants who were not rocked spent progressively more time in a Quiet Alert State, whereas infants who were rocked spent less time in a Quiet Alert State. The results were the most consistent with the hypothesis that the mechanism leading to both the immediate and residual effects of the stimulation was an increase in control and organization of infants’ arousal and autonomic functioning.