Frances K. Graham

Discordant effects of weak prestimulation on magnitude and latency of the reflex blink

In three experiments, the human blink response to 50-msec 105-dB white noise was markedly reduced by prior stimulation with weak tones, either 20 msec long or coextensive with lead intervals of 30 to 240 msec. Although the inhibitory effect was greater with a 70-dB than with a 60-dB lead tone, it was not affected by increasing the lead-tone duration beyond 20 msec. At lead intervals of 30 and 60 msec, the latency of blink onset was also reduced by prestimulation, and this effect was greater with the longer lead tones. Neither effect was an artifact of responding to the lead tone itself. The simultaneous occurrence of an inhibitory change in magnitude and a facilitatory change in latency, and the differential influence of lead stimulus duration, suggest that the magnitude and latency modifications involve different neural mechanisms with different time constants.

Arousal Systems and Infant Heart Rate Responses

Publisher Summary Several writers have recently proposed that there are two arousal systems that affect behavior differently; one energizing response while inhibiting receptive and consolidative processes and the other facilitating these processes and, thus, memory and learning. Sokolovs work, in particular, has stimulated considerable interest but attention has been largely focused on the facilitative “orienting” system to the neglect of an opposite-acting “defense” system. This chapter considers the evidence from adult studies that these two systems can be distinguished by the direction of heart rate (HR) change. It reviews typical procedures and problems encountered in studies of infant HR response and review the data from these studies to determine whether there is a developmental shift from primarily defensive reactions during the newborn period to increasingly probable and larger orienting reactions with increasing age.

Lead-Stimulation Effects on Human Cardiac Orienting and Blink Reflexes.

Innocuous prestimulation can inhibit or facilitate a startle reflex in lower animals, depending on its lead time and on whether it is dircrete or continues throughout the lead interval. Similar effects of lead stimulation on the unconditioned blink reflex were found in human subjects, but human subjects also showed an effect not seen in lower animals. Under conditions of temporal and stimulus uncertainty, the presentation of discrete stimuli at lead times that have no effect in rats produced blink facilitation as well as pronounced cardiac decelerations during the lead interval in man. The article suggests that this effect might be mediated by an attentional process and that it could be dissociated from effects produced by a classical arousal mechanism.

Effects of attending selectively to the spatial position of reflex-eliciting and reflex-modulating stimuli

The question of whether automatic, sensory processes can be modified by selectively directing attention to stimuli was addressed by comparing effects on brainstem reflexes that share a common efferent pathway but have distinct afferent limbs. Subjects judged the duration of brief but intense blink-eliciting tones (Experiment 1) or weak tones preceding a blink-eliciting air puff at interstimulus intervals producing blink inhibition (Experiment 2). Tones occurred unpredictably at left, right, or midline loci; designation of the target location varied across blocks of trials. Latency of blinks to lateralized blink-eliciting targets was facilitated selectively, and the magnitude of blinks evoked by air puff following lateralized prestimulus targets was inhibited selectively. There was no evidence for a midline selective effect. Results appear to support a preset differential processing of stimuli in sensory pathways at low, possibly subcortical, levels and the consequent modification of obligatory, automatic processes.

HABITUATION OF HEART RATE RESPONSE TO REPEATED AUDITORY STIMULATION DURING THE FIRST FIVE DAYS OF LIFE

10 newborns were stimulated for 5 successive days with a moderately intense sound. They responded with rapid acceleration of heart rate (HR) which returned to, but not below, prestimulus levels. Although the response was more prolonged on early trials of the first day than on any later trials or days, there was no significant intersession decrement. Rather, both prestimulus HR and peak HR change, adjusted for prestimulus level, rose significantly across days. Age controls showed that these changes were due to age and not to the repeated stimulation. Some habituation did occur within sessions. It was suggested that the relatively slow intrasession habituation and the absence of intersession habituation might be a function of the type of HR response evoked.

Physiological response to the suggestion of attitudes specific for hives and hypertension.

&NA; A specificity‐of‐attitude hypothesis for psychosomatic disease was tested experimentally by means of hypnotic suggestion of attitudes. Twenty healthy male subjects were given two attitude suggestions on each of 2 days, with the order of presentation reversed on the second day. The two attitudes employed were those associated with hives (the subject felt that he was being unjustly treated and could think of nothing he wanted to do about it), and hypertension (he had to be on guard against bodily assault). It was predicted that skin temperatures would rise more with the hives suggestion than with that for hypertension and that diastolic blood pressure would rise more with the hypertension than with the hives suggestion. Systolic blood pressure, respiratory rate, and pulse rate were also measured. No predictions of differential effects of the two attitudes on these variables were made. The predictions were confirmed. Mean change, maximal rise, and rate of change of skin temperature during the hives suggestion were significantly greater than the corresponding changes during the hypertension suggestion. All three measures of change in diastolic blood pressure were significantly greater during the hypertension than during the hives suggestion. There were no differential effects of the two attitude suggestions on systolic blood pressure, heart rate, or respiratory rate. The experimental design also permitted an analysis of the variance associated with factors other than the two attitude suggestions. There were significant differences during the control periods but not during attitude periods between the first and second day of experimenting. Intersubject differences were also important during control periods but were less so for attitude periods. Some significant variability was associated with the order of presentation of attitudes and with the two experimenters.

Newborn heart-rate response and response habituation as a function of stimulus duration.

The heart-rate response of newborns to auditory stimulation was found to be an inverted U-function of stimulus duration. Groups of 20 Ss each were tested with a 2, 6, 10, 18, or 30-second 75 db stimulus. Response to all stimuli was a heart-rate acceleration whose peak magnitude, latency, and duration varied with stimulus duration and with stimulus repetition. Maximal response occurred following the 10-second stimulus. Repetition of the four longest stimuli led to response decrement but there was no habituation of response to the 2-second stimulus. It was suggested that conflicting results of earlier studies might be reconciled on the assumption that the duration yielding maximal response is a function of stimulus intensity.

Cardiac orienting responses as a function of age

He art-rate changes, recorded from human Ss under conditions appropriate for eliciting orienting, were curvilinearly related to age and independent of differences in prestimulus heart rate. Deceleration was absent at birth, increased from 6 to 16 weeks, and lessened between 16 weeks and young adulthood.

INTELLIGENCE IN TREATED PHENYLKETONURIC CHILDREN: A DEVELOPMENTAL STUDY

Changes in intelligence of 22 diet-treated phenylketonuric children, and of their 6 untreated and 44 unaffected siblings, were studied for an average of 27 months. On both the first and the last intelligence testings, treated children, including those treated from early infancy, had significantly lower scores than their unaffected siblings. However, those treated before 2 years were more intelligent than later-treated children. During the study treated children developed more rapidly than they had before treatment but at a significantly slower rate than that of their unaffected siblings. Age at the beginning of treatment was significantly related to initial IQ, but not to rate of development during treatment. The untreated phenylketonuric group tended to show a decline in intelligence.

Effects of acoustic rise time on heart rate response

Effects of acoustic rise time on heart-rate (HR) response were tested in two experiments. With 50- and 75-dB tones, effects were not clear-cut, but, at 90 dB, fast onsets produced an initial acceleration and slow onsets an initial deceleration. Results were discussed in terms of orienting and startle responses.