Paul A. Obrist

Skin Resistance Levels and Galvanic Skin Response: Unilateral Differences

On five subjects, skin resistance levels and galvanic skin response were recorded unilaterally and simultaneously from each side of the body for between 24 and 36 days. Reliable differences in skin resistance were found in three subjects and in galvanic skin response in two subjects. The magnitude of the skin resistance difference was significantly reduced in four subjects during stimulation.

Stability of cardiovascular reactivity to laboratory stressors: A 2 1 2 yr follow-up

The temporal stability of cardiovascular reactivity to laboratory stressors over a 2 1/2 yr period was studied. Subjects who had earlier received a cold pressor and a shock avoidance reaction time task were brought back for retesting using almost identical tasks. Cardiovascular variables that were common to both sessions included heart rate, systolic and diastolic blood pressure, and pre-ejection period. Correlations were computed to examine the association of responses across both sessions for the four cardiovascular variables during rest and the two tasks. Correlations of both heart rate and systolic blood pressure were high for all tasks and rest, whereas inconsistent correlations were found for diastolic pressure and pre-ejection period. Inconsistencies in diastolic pressure are speculated to be due to individual differences in beta-adrenergic response, whereas lack of consistent pre-ejection period associations may be due to differences in methodology. The results generally support the assumption of stability of cardiovascular reactivity.

Cardiac-somatic changes during a simple reaction time task: A developmental study.

Abstract The relationship during a simple reaction time task between heart rate and four measures of task irrelevant somatic activity was evaluated in four age groups of children, i.e., 4-, 5-, 8-, and 10-year-olds and young adults, in order to evaluate further a hypothesized coupling of cardiac and somatic activity. At all age levels, phasic decreases in both heart rate and somatic activity coincident with performance were found with the magnitude of the effect increasing with age only on three somatic measures. However, tonic levels of both heart rate and somatic activity decreased with age. Performance on the reaction task was found to be inversely related to the age-related phasic somatic effects as well as age-related tonic heart rate and somatic activity.

A Psychobiological Perspective on the Cardiovascular System

Our research concerns the interaction between cardiovascular and behavioral processes. It primarily involves two parameters of the activities of the heart, rate and contractile force, and deals with two interrelated questions. First, can cardiovascular activity tell us anything about behavioral processes? This is the traditional approach of using a biological event as an index of some behavioral state or process. Second, can behavioral processes influence the cardiovascular system, particularly in regard to the etiology of pathological conditions of the cardiovascular system? This is the question of psychosomatics.

Pulse transit time: Relationship to blood pressure

The relationships between pulse transit time (PTT) and both systolic (SBP) and diastolic blood pressure (DBP) were evaluated in 114 human subjects during rest and stress. PTT was found to covary quite consistently with SBP, but not with DBP, when blood pressure was measured both noninvasively and invasively. Pharmacological blockade of the sympathetic innervation of the heart appreciably attenuated the relationship between PTT and SBP.

AUTONOMIC LEVELS AND LABILITY, AND PERFORMANCE TIME ON A PERCEPTUAL TASK AND A SENSORY-MOTOR TASK.

This experiment was intended to evaluate further an hypothesis in which perceptual and sensory-motor performances were considered to be influenced by autonomic processes via autonomic regulation of cortical activity. For this purpose, lability and level measures of sudomotor activity and heart rate were obtained during rest and performance in 54 male Ss. The hypothesis was consistently supported in 7 significant or near-significant correlations out of a possible 14. Faster performance time on the sensory-motor task was found with Ss having low resting heart rate, increased heart-rate variability during performance, and low levels of skin resistance. Faster performance time on the perceptual task was found in Ss with a high frequency of GSR activity during performance. Also, an interaction effect was suggested between some of the autonomic measures, being most pronounced in the perceptual task.

Blood pressure and cardiac changes during signalled and unsignalled avoidance in dogs

Alterations in blood pressure (BP) during two aversive behavioral tasks were studied in five chronically-prepared dogs. During a signalled-avoidance task, BP levels were not altered, although heart rate (HR) increased. While propranolol (0.3 mg/kg, IA) led to slight increases in resting pressure, and phenoxybenzamine (1.0 mg/kg) reductions, the tachycardia at avoidance onset was not affected. Exposure to an unsignalled-avoidance task led to elevated diastolic BP levels during a preavoidance period and to increases in systolic BP, HR and aortic dP/dt at the inception of the avoidance session. Again, neither drug affected the tachycardia during avoidance, but both agents precluded BP and aortic dP/dt increases. Patterns of intercorrelations among cardiovascular variables were similar for both tasks, and suggested that the basis of the BP maintenance shifted from vasomotor to cardiac control during the avoidance periods. The differential cardiovascular adjustments during these tasks could not be accounted for in terms of differences in response rate. Rather, the critical variable seemed to be the amount of feedback the animal received for responding.

The Cardiac-Somatic Relationship

To my surprise, the work we began in the mid-1960s observed a direct relationship between HR and somatomotor activities in several behavioral paradigms. This covariation between HR and somatomotor activity is what I call the cardiac-somatic relationship. The surprise came because I had viewed HR as a rather simple, direct index of the behavioral states generated by these paradigms, a measure independent of somatomotor activity. In fact, I had such a primitive understanding of somatomotor activity and related metabolic processes that initially I did not view the HR and somatic changes as integrated aspects of some more global response process that characterizes the cardiac-somatic concept. Rather, I looked at such HR changes as caused by the actual execution of the somatomotor response similar to the manner HR was viewed in the curarization studies concerning visceral learning (Miller, 1969). As such, these HR changes could be considered artifacts, as Smith (1954) proposed was the case for all conditioned autonomic responses.

Some autonomic correlates of serial learning.

Summary Some previous studies of the relationship between autonomic activity and sensory-motor performance tasks using repeated measurements on the same S have reported a curvilinear inverted U relationship. The present study was undertaken to determine the nature of the relationship between verbal serial learning and autonomic activity (GSR and heart rate), using a repeated-measurements design. This design made it possible to observe the relationship for each S and to evaluate individual differences in the type of relationship. Five S s were run for 28 to 36 days. A curvilinear function in the form of an inverted U was found in three S s between performance and one or more measures of autonomic activity. Linear functions were found in the remaining two S s. Some implications of the results are discussed.

BEHAVIOURAL–CARDIAC INTERACTIONS: THE PSYCHOSOMATIC HYPOTHESIS

Implicit in the psychobiological conceptualization of the interaction between behavioural and cardiovascular processes is that the cardiovascular adjustments, observed as concomitants of behavioural events, were independent of the basic metabolic functions of the cardiovascular system This is what we mean by the psychosomatic hypothesis. This position has come under critical scrutiny over the past decade because of at least two experimental observations. One, in behavioural paradigms, such as the classical aversive conditioning, heart rate was observed to be primarily under vagal control. In humans, this is expressed as an increase in vagal tone and, hence, cardiac deceleration. This appears to violate our assumptions that sympathetic excitator effects should predominate under such circumstances. Two, these vagal influences were observed to be directly related to striate muscle activity. In this case, one can argue that the heart rate effects reflect nothing more than the changes one might expect under conditions where the cardiovascular system is integrated to meet metabolic demands, such as when one exercises, etc.