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Biomedical subjects

L E Roberts

Publications and source records attributed to L E Roberts.

10 recordsLinked to original sources
PubMed1992

Physiological and psychological differentiation of bidirectional baroreceptor carotid manipulation in humans.

We investigated a phase-related-external-suction (PRES) method of bidirectional carotid stimulation which, unlike other methods, is not readily discriminable for direction (excitation vs. inhibition). Thirty-two subjects were first given 128 6-s PRES trials (64 each excitatory and inhibitory) which were signaled by two tones of differing frequency. There followed a 20-trial discrimination phase where subjects' task was to identify excitatory and inhibitory PRES trials (randomly presented) in terms of the two tone signals. Physiological (HR) discrimination was bidirectional (deceleration and acceleration for excitatory and inhibitory PRES trials, respectively), reflex-like (no habituation), but asymmetrical in magnitude (larger decelerations than accelerations), and topography (e.g., presence of a short latency deceleration). Group psychological discrimination was absent, although two subjects had a 100% hit rate on the discrimination test. There were, however, no systematic HR changes associated with these two subjects. Finally, the small-magnitude (2-3 bpm) physiological HR reflex was markedly augmented by what appeared to be a psychological, attentional factor. Accordingly, while the results indicated a dissociation between physiological and psychological differentiation, there was also evidence of a psychological factor (attention) influencing a physiologically induced reflex.

Adult↗
PubMed1992

Modulation of slow cortical potentials by instrumentally learned blood pressure responses.

We assessed whether instrumentally-learned pressor responses inhibit electrocortical activity, as predicted by learning theories of idiopathic hypertension. Subjects received beat-by-beat feedback for increases and decreases in mean arterial pressure measured from the finger (Peñáz method). Slow potentials were recorded from the midsagittal line during the final training session. Also recorded at this time were heart rate, eye movements, respiration, and post-session verbal reports of the subject's control strategies. Thirteen of 14 subjects differentiated blood pressure increases and decreases at p less than .05 or better during the final session (within-subject discriminative operant procedure). Slow potentials were less negative on blood pressure increase compared to decrease trials at all midsagittal sites (p less than .02), indicating relative cortical inhibition by pressor responses. This effect occurred even though subjects reported tensing of muscles on increase trials (p less than .01), a behavioral activity previously associated with augmented rather than diminished cortical negativity. On increase trials slow potentials shifted toward positivity just prior to heart rate deceleration (the latter effect confirming activation of the baroreceptors).

Adult↗
PubMed1991

Evidence for autonomic-autonomic dissociation: an alternative to Dworkin and Dworkin (1990).

Dworkin and Dworkin (1990) reported that conditioned responses of the tibial nerve (a putative measure of skeletal motor activity) were uncorrelated with conditioned responses of the plantar vasculature during discriminative Pavlovian conditioning in the chronically paralyzed rat. On the basis of this finding, Dworkin and Dworkin concluded that the vasomotor response had not been mediated by skeletal motor processes. This commentary presents neuroanatomical, physiological, and behavioral evidence that suggests that sudomotor (sweat gland) and not skeletal motor efference might have been responsible for the classically conditioned tibial nerve response of Dworkin and Dworkin (1990). If this interpretation is correct, then Dworkin and Dworkin have documented an autonomic-autonomic dissociation, not a skeletal motor-autonomic dissociation. Response mechanisms in Pavlovian and instrumental autonomic conditioning are discussed.

Animals↗
PubMed1990

Extended dissociative training of sudomotor response patterns.

Subjects viewed two feedback displays, one depicting skin conductance and the other either respiratory behavior (respiration group) or subtle body movements (movement group). The subject's task was to increase skin conductance and the concomitant activity on integration trials, and to increase conductance while holding the concomitant behavior constant on dissociation trials. All subjects succeeded at integration over 15 sessions of training. In addition, 4 of 5 subjects in the respiration group successfully increased skin conductance on dissociation trials without altering the pre-trial pattern of breathing. However, volar activities (e.g., finger-to-finger contact, finger flexion) were observed on these trials. Volar activities were also adopted on dissociation trials by subjects trained in the movement group. Successful subjects in this group identified volar manipulations that did not affect a sensitive movement transducer. Attempts by subjects to compensate for habituation of conductance responses to deep breaths and finger flexion reduced or reversed within-subject correlations involving these concomitants, on integration and dissociation trials. The results do not support the view that visceral-somatic linkages can be uncoupled through instrumental learning.

Adult↗
PubMed1989

Self-report during feedback regulation of slow cortical potentials.

Subjects received exteroceptive feedback for bidirectional changes in slow cortical potentials or alpha power measured from the vertex. The slow potential group succeeded in shifting slow potentials toward negativity and positivity on feedback and transfer trials requiring these changes, after two sessions of training. Differentiation of negativity and positivity was accompanied by verbal reports of somatomotor activation that occurred on trials on which negative slow potentials were required (p less than .01). Vertical and lateral eye movements, chin and frontalis electromyogram, and heart rate did not differentiate between negativity and positivity trials in the slow potential negativity during feedback. Although the alpha power group did not succeed at controlling changes in alpha, evidence of a training effect appeared in verbal reports of emotional arousal (p less than .05) and focused vision (p less than .08) on alpha suppression trials in this group. We discuss the findings from the viewpoint that biofeedback tasks involving electrocortical responses are problems in the organization of action that subjects seek to solve.

Adult↗
PubMed1978

A comparison of the mechanisms and some properties of instructed sudomotor and cardiac control.

Instructed control defined as differential compliance with verbal instructions to increase and decrease a response was assessed when a change in sudomotor activation or heart rate was specified as the behavioral goal. Instructed control of heart rate was evident prior to explicit feedback training for this response, but instructed control of sudomotor activation defined as finger sweating and measured as skin conductance was not. Feedback training subsequently established instructed control of sudomotor responding, but such training did not lead to a significant improvement in control of heart rate. Explicit strategy suggestions emphasizing emotional responding and intended or actual movement appeared to interfere with the performance of instructed control under both target conditions. Instructed changes in heart rate were attended by correlated changes in somatomotor and respiratory function. Somatomotor and respiratory responses were also observed when subjects were instructed to change sudomotor activation, but these correlated activities were of small magnitude and were not augmented by feedback training as was target responding. Several accounts of the basis for differences that were evident between the target conditions with respect to feedback effects and response patterns are discussed.

Adult↗
PubMedDate not supplied

Area-specific self-regulation of slow cortical potentials on the sagittal midline and its effects on behavior.

Exteroceptive feedback was given for negative and positive shifts in slow potentials (SPs) recorded from Fz, Cz, or Pz (between groups design). Slow potentials at the feedback site were referred to adjacent scalp and non-cephalic electrodes, so as to confine SP shifts to the feedback location. Area-specific regulation of SPs was obtained at each midsagittal site after 3 days of feedback training. Subjects reported sensorimotor and emotional arousal when negative SP shifts were trained frontally, but not when negative shifts were trained parietally (cognitive/attentional strategies reported after parietal feedback). Area-specific regulation of SPs was subsequently abolished when behavioral tasks were added to further probe frontal/parietal differences (dual-task procedure). These findings indicate that area-specific self-regulation of SPs is possible on the sagittal midline, and that self-regulated parietal SPs (in contrast to frontal ones) arise from non-motoric generators. The source of SP self-regulation was more readily probed by verbal reports of feedback strategy than by study of dual-task relations, because feedback control was disrupted by the dual-task requirement.

Adult↗