Variation in motor activity on different time scales and responsiveness to oral stimulation in the rat fetus

Abstract

The near-term rat fetus exhibits brief oral grasp responses to discrete presentations of an artificial nipple. In the present experiment, an artificial nipple was presented to individual fetal subjects 10 times. Five of the presentations were timed to occur when spontaneous fetal motor activity was low and five while activity was high, as determined by the baseline activity for the individual fetus. The likelihood of responding to the artificial nipple was increased when the fetus was relatively inactive at the moment of stimulus presentation. Furthermore, stimulus presentations that resulted in oral grasping of the artificial nipple were associated with greater point-to-point variability (2-s intervals) in motor activity during the 30-s period preceding the presentation of the artificial nipple. This pattern of results indicates that the recent history of general motor activity as well as the level of activity at the instant of stimulus presentation may contribute to variation in responding to biologically relevant stimuli early in development.

Programmed to learn? The ontogeny of mirror neurons

“…Spontaneous motor activity usually involves the entire body (Almli, Ball & Wheeler, 2001;Groome et al , 1999), including arms and hands, which are often moved repeatedly in short bouts of activity (Adolph & Berger, 2005;Piaget, 1962). Cyclic movements (CM) with similar characteristics have also been reported in rat and sheep foetuses (MacLennan, Smotherman & Robertson, 1998;Robertson & Bacher, 1995;Robertson et al , 1996; Zhou et al (2003). Dotted line: stabilization after one cycle.…”

“…Spontaneous motor activity usually involves the entire body (Almli, Ball & Wheeler, 2001; Groome et al , 1999), including arms and hands, which are often moved repeatedly in short bouts of activity (Adolph & Berger, 2005; Piaget, 1962). Cyclic movements (CM) with similar characteristics have also been reported in rat and sheep foetuses (MacLennan, Smotherman & Robertson, 1998; Robertson & Bacher, 1995; Robertson et al , 1996; Smotherman, Robinson & Robertson, 1988; Suzue & Shinoda, 1999), probably representing an ubiquitous feature of mammalian motor development 2 . In humans, they persist after birth until at least 4–5 months of age (Groome et al , 1999; Robertson, 1987, 1990, 1993a).…”

Classical conditioning of responses to an artificial nipple in the rat fetus: Mu and kappa opioid systems

“…Because the immediate effects of milk on opioid activity are short-lasting, responsiveness reappears and suckling stimuli (i.e., nipple and milk) again come to direct the pup's attention. The suckling situation, when viewed from this perspective, includes a mechanism for the pup to alternate between processing stimuli relevant to continued expression of sucking and information relevant to other features of its immediate surroundings (MacLennan, Smotherman, & Robertson, 1998;Reilly, Robertson, & Smotherman, 1997).…”

Fetal cyclic motor activity in diabetic pregnancies: Sensitivity to maternal blood glucose

“…In fetal sheep, CM is sensitive to the spontaneous uterine contractions that normally occur during the last third of gestation, similar to Braxton-Hicks contractions in humans (Robertson et al, 1996). In the rat, CM is influenced by fetal exposure to cocaine (Simonik, Robinson, & Smotherman, 1994), and regulates behavioral responsiveness to perioral stimulation before and after birth (Bacher, Robertson, & Smotherman, 2000;MacLennan, Smotherman, & Robertson, 1998;Reilly, Robertson, MacLennan, & Smotherman, 1997). After birth in humans, CM is sensitive to sound and tightly coupled to visual attention Robertson, Bacher, & Huntington, 2001), and it appears to regulate social interaction with an adult (Huntington, 2001).…”