Motor and Cardiac Response during Habituation Testing: Demonstration of Exaggerated Cardiac Reactivity in a Subgroup of Normal Human Fetuses

Abstract

In this study we wanted to determine: (1) whether or not a relationship existed between the rate of habituation of the fetal motor response and changes in the fetal heart rate (FHR), and (2) if this relationship could be used to identify a subgroup of fetuses who exhibited exaggerated cardiac reactivity during habituation testing. Thirty-nine normal human fetuses between 34 and 40 weeks of gestation were evaluated. Habituation testing consisted of a 1 second vibroacoustic stimulus with a 10 second interstimulus interval for eight trials. The motor response was observed using real-time sonography, and a score of 0 to 10 was assigned for each trial based on subjective assessment of the fetal response. Motor habituation was evaluated in terms of the rate of response decrement in movement over trials (Re). Subjects were initially divided into slow and fast motor habituators based on the median of Re, and it was found that fetuses whose motor response habituated slowly displayed a significantly greater increase in heart rate compared with fetuses who habituated more rapidly (F1,37 = 8.61; P = 0.0057). Cardiac reactivity was then defined as "the average increase in FHR above the mean prestimulus value during the last half of the testing period." When the data were divided into quadrants based on medians, we identified seven (18%) fetuses who habituated rapidly but who also displayed high cardiac reactivity. We conclude that there is a significant relationship between the magnitude of the increase in FHR above baseline and the rate of motor habituation in normal human fetuses.

State Control in the Substance‐Exposed: Fetus I. The Fetal Neurobehavioral Profile: An Assessment of Fetal State, Arousal, and Regulation Competency

“…Simultaneous recording of physiological and behavioral data allows for the interrogation of possible linkages in behavior and physiology as well as possible “dissociations.” Recent data suggest that the dissociation of two or more variables that normally occurs together will provide a more sensitive index of pathological conditions and, therefore, provide a more sensitive marker of CNS integrity. 23,53 (3) Real‐time and off‐line analyses can be used effectively for research as both behavioral and physiological data are simultaneously recorded. Off‐line assessment can be used to investigate subtleties not able to be interrogated during real‐time recording.…”

Fetal habituation performance: Gestational age and sex effects

“…Previous studies have varied in every aspect of stimulus characteristics and response assessment. While many authors have used VAS to habituate the fetus (Doherty & Hepper, 2000; Groome et al , 1994; Kuhlman et al , 1988; Madison et al , 1986b; van Heteren et al , 2001), there are other studies where pure tones have been used as the habituating stimulus (Hepper & Shahidullah, 1992; Kisilevsky & Muir, 1991). Vibroacoustic stimulation (VAS) does appear to have some advantages over other forms of fetal stimulation: intense stimuli may overcome any effect of behavioural state on fetal responsiveness (Shalev et al , 1990) and VAS has also been reported to produce more reliable responding (Leader, 1995).…”

“…The criterion for habituation has included ‘non‐response to two consecutive stimuli’ (Kuhlman et al , 1988), ‘non‐response to four consecutive stimuli’ (van Heteren et al , 2001) and ‘non‐response to five consecutive stimuli’ (Doherty & Hepper, 2000; Hepper & Shahidullah, 1992; Leader et al , 1982a; Madison et al , 1986b). Others have employed a ‘rate of change score’ (Groome, Swiber, Bentz, Holland, & Atterbury, 1995), a score on a scale (Groome et al , 1993, 1994) or a ‘movement score’ (Kisilevsky & Muir, 1991). Methods used to evaluate FHR habituation have been even more diverse.…”

“…Maturation of the fetal CNS as gestation progresses is reflected in: increased tone; increasingly sophisticated and integrated movements (James et al , 1995); the development of rest–activity cycles around mid‐gestation (deVries, Visser, & Prechtl, 1982); the linking of these cycles to specific parameters of the fetal heart rate pattern and eye movements (Visser, Mulder, & Prechtl, 1992); and in the appearance of stable behavioural states from 36 weeks (Nijhuis, Prechtl, Martin, & Bots, 1982). Maturation is also reflected by the onset of the fetal movement and fetal heart rate responses to vibroacoustic stimulation (Gagnon, Hunse, Carmichael, Fellows, & Patrick, 1987; Leader et al , 1982b) and by observations of fetal learning reported in late gestation, including studies of classical conditioning (Feijoo, 1981) and of fetal heart rate and motor habituation (Doherty & Hepper, 2000; Groome et al , 1994; Leader et al , 1984; Sandman et al , 1999; Smith et al , 1991). If the habituation response is reflective of CNS functioning, then habituation performance might be expected to reflect this advancing development throughout gestation.…”

“…Habituation can be defined as the response decrement to repetitive stimulation (Harris, 1943) and is considered to be the simplest form of learning (Thompson & Glanzman, 1976; Thorpe, 1956), playing an important role in the general adaptation of an organism to its environment (Glaser, 1966; Glass & Singer, 1972). Habituation has been studied at many levels of functioning and in many different subject populations, including the human infant (Bornstein, 1989b; Jeffrey & Cohen, 1971; McCall & Carriger, 1993; Slater & Morison, 1985) and the human fetus (Doherty & Hepper, 2000; Goldkrand & Litvak, 1991; Groome, Mooney, & Dykman, 1994; Kisilevsky & Muir, 1991; Kuhlman, Burns, Depp, & Sabbagha, 1988; Leader, Baillie, Martin, & Molteno, 1984; Sandman, Wadhwa, Chicz‐DeMet, Porto, & Garite, 1999; Smith, Davis, Rayburn, & Nelson, 1991; van Heteren, Boekkooi, Schiphorst, Henk, & Nijhuis, 2001). Habituation performance is thought to reflect central nervous system (CNS) functioning, both within the infant literature (Bornstein & Sigman, 1986; McCall, 1981; McCall & Carriger, 1993; Siegel, 1989) and within the fetal literature (Groome et al , 1994; Hepper, 1990; James, Pillai, & Smoleniec, 1995; Krasnegor et al , 1998; Leader, Baillie, Martin, & Vermeulen, 1982b; Madison et al , 1986a; Smith et al , 1991).…”