Neonatal sucking: Effects of quantity of the response-contingent fluid upon sucking rhythm and heart rate

The temporal organization of neonatal nutritive sucking and heart rate were studied in two consecutive 4-min periods to analyze the effects of two quantities of response-contingent fluid. One group of newborns experienced only the larger amount, a second experienced the smaller, and two other groups experienced both in counterbalanced order. Cumulative pausing time and intersuck intervals (sucking rate within bursts) were both affected by the amount of fluid delivered at each response. At the start of sucking bursts, heart rate accelerated to a stable level. Within-burst heart rates were higher with increased quantity of contingently delivered fluid. The results are discussed in relation to the distinction between nutritive and nonnutritive sucking and to previous findings on the effects of fluid sweetness upon sucking.     

Reinforcement from the sucking environment and subsequent modification of sucking behavior in the human neonate

The reinforcing aspects of sucking behavior in 36 human newborns was examined in a limited instrumental conditioning paradigm where sucking was both operant and reinforcer. During training, response density (rate based on sucking opportunity time) and latency were measures of two components of nonnutritive sucking, contingent negative pressure suction, and incidental jaw movement. The strategy for determining the reinforcing aspects of sucking involved comparisons of three types of sucking stimuli as reinforcers. The nature of modified operant sucking was investigated during extinction by examining number of sucks per burst, number of bursts emitted, and interburst interval time. The feedback from sucking which acted as reinforcement was concluded to be response density. Sucking was modified by changes in pausing behavior, including response latency and pauses between bursts of sucks. The number of sucks per burst also showed a significant change under certain conditioning arrangements.     

Effects of fluid delivery on the sucking response of the human newborn

Two experiments were conducted with human newborns to compare sucking behavior under nutritive and nonnutritive sucking conditions using several fixed-ratio schedules of reinforcement. Results showed that: (1) nutritive sucking produces higher over-all sucking rates but lower within-burst rates, (2) burst lengths are longer during nutritive than nonnutritive sucking, (3) fewer bursts per unit time occur during nutritive sucking, (4) fluid termination following nutritive sucking produces a sharp response decrement, suggestive of a negative contrast effect when compared with sucking rates under continuous no-fluid sucking. Response diminution occurs in the first 2–3 min of sucking under all conditions, reflecting the necessity of control comparisons in studies documenting sucking change under changing stimulus or reinforcement conditions.     

The quality of sucking in infants with colic

Feeding problems have been reported in infants with colic. The purpose of this study was to examine the nutritive sucking pattern of infants identified as having colic. Twenty-nine infants (16 with colic and 13 controls) between the ages of 1 to 3 months, being bottle-fed by their mothers, were observed by a blind examiner. We hypothesized that infants with colic would show greater disorganization in nutritive sucking and show greater variability in sucking rate than infants without colic, as assessed by the revised Neonatal Oral Motor Assessment Scale (NOMAS). Infants with colic were found to present a disorganized sucking pattern; namely, a lack of rhythmical movement and a difference in amount of sucks per burst than infants without colic. Methods of intervention are suggested.     

Effects of nutritive and non-nutritive sucking on infant heart rate variability during the first 6 months of life

The effects of eating on heart rate variability (HRV) differ between adults and newborns. This may reflect the impact of suckling on the overall psychophysiological and autonomic nervous system maturation. The purpose of the present study was to explore whether the reactions of HRV during feeding change towards the adult pattern during the first 6 months of life. In addition, the effects of non-nutritive and nutritive sucking on heart rate (HR) and HRV were compared. The participants were 23 infants on whom recordings were performed as newborns and at 6, 12 and 24 weeks old. Nutritive sucking caused an increase in HR and a decline in HRV. The results were consistent with previous reports of a decrease in high frequency components of HRV during feeding in newborns, reflecting a decrease in parasympathetic activity. This response was apparent in all four ages studied, and remained similar throughout the 6-month period. However, age as an independent factor seemed to influence both HR and HRV. Pacifier sucking had no significant effects on HRV at any age. The results demonstrate the physical strain that sucking imposes on the baby, with a specific autonomic nervous system response involved. We consider this response an essential part of the overall psychophysiological maturation of infants.     

SALTNESS, SWEETNESS, AND PREFERENCE: A study of quantitative relations in individual subjects

Individual scales were constructed for saltness and preference in an experiment with eight subjects and for sweetness and preference in a second experiment with seven of these subjects. It was found (1) that power functions described the individual relations between sodium chloride and sucrose concentration, on the one hand, and the subjective variables of saltness and sweetness, on the other hand, (2) that the exponents exceeded 1 but varied greatly between subjects, and (3) that there was a great variation over individuals with regard to the form of the saltness/preference and the sweetness/preference relations.     

Analysis and treatment of finger sucking

We analyzed and treated the finger sucking of 2 developmentally typical children aged 7 and 10 years. The functional analysis revealed that the finger sucking of both children was exhibited primarily during alone conditions, suggesting that the behavior was maintained by automatic reinforcement. An extended analysis provided support for this hypothesis and demonstrated that attenuation of stimulation produced by the finger sucking resulted in behavior reductions for both children. Treatment consisted of having each child wear a glove on the relevant hand during periods when he or she was alone. Use of the glove produced zero levels of finger sucking for 1 participant, whereas only moderate reductions were obtained for the other. Subsequently, an awareness enhancement device was used that produced an immediate reduction in finger sucking.     

Breast milk odor via olfactometer for tube-fed,premature infants

Human newborns use odor cues to orient to their source of nutrition. However, tube-fed, premature infants have restricted chemosensory experience. New methods of introducing breast milk odor to tube-fed premature infants will permit empiric tests of the effect of controlled exposure to nutrient odor. We therefore developed an infant olfactometer and piloted its use in 7 tube-fed, premature infants in the neonatal intensive care unit. Since nonnutritive sucking shortens the amount of time required to wean from tube-feeding, we tested the effect of breast milk odor on nonnutritive sucking. Six out of 7 subjects responded to breast milk odor with an increase in number of sucks. Statistical analysis supported the hypothesis that breast milk odor reinforces nonnutritive sucking. These results indicate the feasibility and potential of this experimental approach, and warrant further study of the effect of controlled nutrient odor exposure on feeding behavior of premature infants.     

Effects of auditory stimulation upon non-nutritive sucking by premature infants.

Changes in non-nutritive sucking contingent upon presentation of an auditory stimulus previously found capable of eliciting heart-rate acceleration was investigated in a sample of 24 premature infants. Across 30 10-sec. presentations of the stimulus, only transient changes in sucking rate during the first 6 trials were observed, and these effects obtained primarily for those infants showing few abnormalities in their non-nutritive sucking behavior. These results were discussed as reflecting possible differences in infants' attention associated with sucking pathology and the dependence of psychological assessment upon the specific response index used.     

Assessment of the taste interaction between two qualitatively similar-tasting substances: a comparison between comparison rules

The taste interaction between sucrose and fructose was assessed by using three different comparison procedures: the summated response comparison, the factorial plot comparison, and the equimolar comparison rule. The perceived sweetness intensities were obtained on a ratio scale by using a functional measurement approach in combination with a two-stimulus procedure. The conclusions obtained from each of the three comparison rules were identical. The taste interaction between sucrose and fructose could be explained to a large extent, but not completely, by the apparent taste "interactions" within sucrose and fructose as single substances. It is argued that the apparent taste interaction within a large number of single sugars and between two of these sugars in a mixture is somewhat synergistic at low sweetness levels, additive at intermediate sweetness levels, and suppressive at high sweetness levels.     

Gustatory cross adaptation between sweet-tasting compounds

Taste profiles were obtained for 16 compounds after adaptation to sucrose, saccharin, and water. Sucrose adaptation reduced the sweetness of all sweet compounds. Saccharin adaptation, when analyzed over all compounds, also reduced sweetness, but the effect was less than that of sucrose. It is concluded that there may be a single receptor mechanism for the sweet quality. Adaptation to sucrose also increased the saltiness, sourness, and bitterness of the other compounds slightly. This increase should be attributed to the taste : induced in water by adaptation to sucrose rather than a potentiation of the other compounds per se.     

Effects of instructions, biofeedback, reward, and cognitive mediation on the control of heart rate and the application of that control in a stressful situation

Subjects in Phase 1 of this experiment were (a) instructed to try to either increase or decrease their heart rate, (b) with or without the use of biofeedback, and (c) with or without the promise of money for successful performance, whereas no-treatment subjects were given no instructions, no biofeedback, and no promise of reward. Results indicated that (a) when simply instructed to do so, subjects could increase but not decrease their heart rates relative to no treatment controls, (b) the promise of money for good performance aided subjects in increasing but not decreasing heart rate, and (c) biofeedback did not aid subjects in either increasing or decreasing heart rate. Various cognitive strategies employed by subjects in controlling their heart rates are discussed.In Phase 2, subjects in a stress condition were told that they would receive a series of painful electric shocks, whereas subjects in a no stress condition were not told about shocks. All subjects were instructed to try to decrease their heart rates during the “shock” period. Heart rate and self report data revealed that (a) the manipulation was successful in increasing stress, and (b) previous training in decreasing heart rate, with or without biofeedback, did not aid subjects in decreasing their heart rates in the face of the stress.     

Depressed mothers' newborns show less discrimination of other newborns' cry sounds

Newborns' crying in response to the cry of another newborn has been called an empathetic response. The purpose of this study was to determine whether newborns of depressed mothers showed the same response. Newborns of depressed and non-depressed mothers were presented with cry sounds of themselves or other infants, and their sucking and heart rate were recorded. The newborns of non-depressed mothers responded to the cry sounds of other infants with reduced sucking and decreased heart rate. In contrast, the newborns of depressed mothers did not show a change in their sucking or heart rate to the cry sounds of other infants. This lesser attentiveness/responsiveness to other infants' cry sounds may predict their later lack of empathy.     

The organization of non-nutritive sucking in the premature infant

Changes in non-nutritive sucking contingent upon the repeated presentation of unpatterned and patterned light stimulation were examined in a sample of 18 premature infants. Stimulus contingent sucking change in chronologically younger infants tended to be somewhat shorter in duration than that of the chronologically older infants and showed stimulus contingent sucking acceleration as well as suppression. Evidence was also found for less orienting among infants showing abnormalities in their sucking behavior. No evidence for habituation was found in any subgroup. Possible factors contributing to the strength and nature of stimulus contingent non-nutritive sucking changes in infants are discussed.     

An inexpensive electro-fistular swivel for negative feedback control of self-stimulation

A swivel was developed for concurrent intraorganismic fluid injection and intracranial electrical stimulation of the unrestrained rat. Effects of various intragastric injections on bar-pressing maintained by electrical stimulation of the hypothalamus were studied. In some subjects, intragastric injections of either water or milk decreased the rate of responding. This decrease resulted from pauses in responding rather than from decreases in the local rates of responding. The decrement in responding occurred at a lower gastric volume during milk injection than during water injection. In other subjects, however, neither water, milk, nor 32% sucrose injections affected the rate of self-stimulation.     

An on-line program to calculate respiratory sinus arrhythmia amplitude

A variety of evidence shows that the amplitude of respiratory sinus arrhythmia (RSA)—the peak-to-peak variations in heart rate caused by respiration—is a valid and reliable index of para-sympathetic cardiac control. An on-line program to calculate RSA amplitude on a breath-by-breath basis is described. The validity of the RSA amplitude values obtained through the computer pro-gram were tested in two studies. From the first one, the correlations between RSA amplitude and a set of cardiorespiratory variables, under both rest and auditory stimulation conditions, are reported. In the second study, the effect of atropine administration on the RSA amplitude, under both rest and mental load conditions, was examined. The results of both studies are con-gruent with predictions and suggest the usefulness of the software.     

Influence of auditory tempo on the endogenous rhythm of non-nutritive sucking

The aim of this study was to examine the perception of time in the first months of life. Does the perception of contextual temporal information (an auditory tempo) induce modifications in spontaneous motor behavior (in the present case, non-nutritive sucking behavior) at birth and at 2 months? Two auditory tempos were successively tested. The first was the same as the previously recorded spontaneous motor tempo (SMT); the second was 15% faster or 15% slower than the infant's SMT according to the group. Results showed that modification of the sucking tempo depended on age and contextual temporal information. Two-month-old infants were able to adapt their endogenous sucking rhythm to an external tempo if it was faster than their spontaneous rhythm. Results also confirmed that slowing down the sucking rate was difficult for both groups of infants. In sum, the results suggest that, to a certain extent, very young infants are sensitive to contextual modifications (which indicates that they perceive them). This study has thus identified certain features of the internal time base rate from birth which could help define a developmental internal clock model of contextual temporal processing.     

Acquired flavour preferences: contextual control of adaptation-level effects

This experiment investigated the role of context in the expression of conditioned flavour preferences. Rats were trained on a mixture of almond and sucrose and were then given intermixed exposures to almond in one context (Context A) and to sucrose in a second context (Context S). Finally, choice tests were given in both contexts, with one group given almond-versus-water tests and the other almond + sucrose-versus-sucrose tests. Preference for almond over water was greater in Context A than in Context S. Conversely, preference for almond + sucrose over sucrose was greater in Context S than in Context A. These results suggest that the perceived sweetness of a flavour depends on the context in which it is presented and confirm that expression of a flavour preference depends on the type of test employed.     

Anxiety, perception, and control of heart rate

8 women and 8 men took Cattell's IPAT-anxiety questionnaire and later McFarland's test of ability to perceive heart activity. The second test involved subjects' tracking their own heart rates, then they enrolled in an EKG biofeedback session to evaluate ability to increase and decrease heart rate from subjects' resting baselines. At the end of the session each subject completed Blanchard, et al.'s questionnaire to specify the cognitive strategies used for heart-rate control. Heart rate, abdominal respiration rate, respiration amplitude, EEG percent power in theta, alpha, and beta bands were evaluated. Success of heart-rate decrease seemed to depend mainly on activity levels: the subjects who achieved high scores on the activity test decreased heart rate significantly better than did low scorers. The relationship between scores for perception of heart and increases in heart rate was nonsignificant: increased heart-rate seemed to depend on differences in respiration between the rest and periods of increase. The significant, negative correlation between trait anxiety and perceptions of heart activity suggested that anxiety affected subjects' ability to perceive heart rate. The theta EEG power of the right hemisphere was significantly higher in subjects scoring high than for those low in perception of heart activity. During heart-rate increase tasks subjects mainly reported use of 'arousal responses,' similarly during heart-rate decrease tasks they reported use of relaxation responses.     

Acquired flavour preferences: Contextual control of adaptation-level effects

This experiment investigated the role of context in the expression of conditioned flavour preferences. Rats were trained on a mixture of almond and sucrose and were then given intermixed exposures to almond in one context (Context A) and to sucrose in a second context (Context S). Finally, choice tests were given in both contexts, with one group given almond-versus-water tests and the other almond + sucrose-versus-sucrose tests. Preference for almond over water was greater in Context A than in Context S. Conversely, preference for almond + sucrose over sucrose was greater in Context S than in Context A. These results suggest that the perceived sweetness of a flavour depends on the context in which it is presented and confirm that expression of a flavour preference depends on the type of test employed.