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Biomedical subjects

R F Simons

Publications and source records attributed to R F Simons.

At least 19 recordsLinked to original sources
PubMed2001

Prepulse effects as a function of cortical projection system.

A putative gating mechanism reduces startle blink, midline scalp potentials beginning with P50, and perceived loudness of startling stimuli. Tactile prestimuli were paired with auditory startle stimuli to determine if: (1) P50 inhibition is due to an extrinsic mechanism, (2) pairing differentially affects potentials reflecting modality specific and nonspecific system activity, and (3) crossmodal pairing modifies perceptual magnitudes of both pair members. Stimuli were presented alone and in pairs separated by 60 or 360 ms. Event-related potentials (ERPs) were recorded from midline and lateral sites; EMG was recorded from several facial and scalp muscles. Pairing reduced blink, and midline P50, N100 and P200 amplitudes; reductions were greater at the longer interval. P30 was largely unaffected by pairing. Pairing also differentially affected lateral N100 components reflecting later activity in specific and nonspecific systems. Results show that prestimulus inhibition of ERPs is not due to intrinsic refractoriness and that pairing differentially affects ERPs associated with modality specific and nonspecific projection systems.

Adult↗
PubMed2001

On the relationship of P3a and the Novelty-P3.

Deviant stimuli give rise to a late positive ERP component with latencies from 250 to 400 ms. Target deviants elicit a P300 with maximum amplitude over parieto-central recording sites while the 'P300' elicited by deviant nontarget stimuli occurs somewhat earlier and shows a more frontally-oriented scalp distribution. Two varieties of frontal P300s have been described, elicited either by rare stimuli (target or nontarget) presented in a two-stimulus oddball task (P3a) or by infrequent, unrecognizable stimuli presented in the context of a three-stimulus oddball task (Novelty-P3). The Novelty-P3 has been observed in a number of subsequent studies; the P3a has not been extensively studied and both its significance and existence have been called into question. The present report describes a replication of two prototypical studies with 'frontal' P3s observed in each context. Application of factor analysis to the two sets of ERP waveforms does not support a distinction between these two components.

Adult↗
PubMed2000

Proactive and reactive aggression in delinquent adolescents: relations to aggression outcome expectancies.

Investigated whether the relation between aggression and the tendency to expect positive outcomes for aggressive behavior is specific to the proactive subtype of aggression (as opposed to the reactive subtype). In a sample of 86 incarcerated adolescent boys ages 13 to 18, we measured outcome expectancies for aggression using audiotaped hypothetical vignettes. For each participant, staff members completed proactive and reactive aggression rating scales. Regression analyses revealed that the relation between aggression and outcome expectancies was indeed specific to proactive aggression. Furthermore, this finding was supported regardless of whether outcome expectancies were assessed using vignettes describing proactive-aggressive behavior or those describing reactive-aggressive behavior. We discuss these findings and argue that interventions to reduce proactive or reactive aggression should differ from each other by addressing the specific social cognitive processes involved in each type of aggression.

Adolescent↗
PubMed2000

Image motion and context: a between- and within-subjects comparison.

In two previous experiments, we studied how stimulus motion affects both the self-report of emotion experience and the physiological sequelae of emotion. In both studies, image motion intensified emotional responding, and the effect of motion was relatively specific to the arousal dimension of the emotion; there was little evidence that image motion altered the valence of the image. Moving images also appeared to sustain the attention of the participants for a longer period of time than did the still images. In these two experiments, however, image motion was manipulated within participants. In the present experiment, we used a between-subjects manipulation of image motion and found a nearly identical pattern of results. These data indicate that motion inherently increments the arousal value of an image and that this increment is not dependent on the context in which motion is introduced.

Adult↗
PubMed1999

Emotion-processing deficit in alexithymia.

College undergraduates were identified as alexithymic or control, based on their scores on the Toronto Alexithymia Scale (TAS; Taylor, Ryan, & Bagby, 1985). All subjects were presented standardized emotion-eliciting color slides for 6 s while facial muscle, heart rate, and skin conductance activity were recorded. Stimuli were presented a second time while subjects were asked to provide emotion self-reports using a paper-and-pencil version of the Self-Assessment Manikin (SAM; Lang, 1980) and to generate a list of words describing their emotional reaction to each slide. Consistent with the definition of alexithymia as a syndrome characterized, in part, by a deficit in the identification of emotion states, high TAS subjects supplied fewer emotion-related words than did controls to describe their response to the slides. Alexithymics also indicated less variation along the arousal dimension of the SAM, produced fewer specific skin conductance responses and showed less heart rate deceleration to the slides, regardless of category. No valence-related differences between alexithymic and control subjects were noted.

Adult↗
PubMed1999

Emotion processing in three systems: the medium and the message.

In the context of picture viewing, consistent and specific relationships have been found between two emotion dimensions (valence and arousal) and self-report, physiological and overt behavioral responses. Relationships between stimulus content and the emotion-response profile can also be modulated by the formal properties of stimulus presentation such as screen size. The present experiment explored the impact of another presentation attribute, stimulus motion, on the perceived quality of the induced emotion and on its associated physiological response pattern. Using a within-subject design, moving and still versions of emotion-eliciting stimuli were shown to 35 subjects while facial muscle, heart rate, skin conductance, and emotion self-reports were monitored. The impact of motion was dramatic. Self-report and physiological data suggested strongly that motion increased arousal, had little impact on valence, and captured and sustained the subject's attention to the image.

Adult↗
PubMed1998

Input and central processing expressed in ERP and heart rate changes to rare target and rare nontarget stimuli.

Whether late positive components of event-related potentials (ERPs) parallel changes in heart rate (HR) indicative of attention/orienting to rare stimuli has been debated. In the present study, a three-stimulus design was used, with rare target, rare nontarget, and frequent standard stimuli delivered under identical conditions except that instructions to subjects described the targets to which subjects should respond but did not describe the nontargets. In Experiment 1, stimuli varied among modalities; in Experiment 2, auditory stimuli were employed. Both ERPs and HR were consistent with automatic processing preceding two stages of controlled processing. Rare stimuli evoked larger parietal P300 and initial HR deceleration than standards. Presumably because of load-reducing effects of long interstimulus intervals, targets and nontargets were not distinguished before a late slow wave and a late phase of HR acceleration. Neither rare stimulus elicited a recognizable frontal P3a.

Acoustic Stimulation↗
PubMed1994

Emotional imagery and physical anhedonia.

A previous study by Fitzgibbons and Simons (1992) confirmed that subjects identified as anhedonic consistently report a reduced experience of pleasure when confronted with hedonic stimuli (i.e., color slides). Evidence that this emotion-processing deficit extended from the verbal report to the physiological and behavioral domains was mixed but suggested that poor imagery might be associated with the reduced capacity to experience pleasure. The present experiment was designed to test this hypothesis more directly. Anhedonic and normal control subjects were presented scripts, which they were to imagine as vividly as possible. During both script presentation and imagery, heart rate, skin conductance, and facial muscle activity were recorded. Verbal reports of emotional experience were obtained subsequent to each image. The physiological data, as well as an imagery questionnaire, were consistent with the poor imagery hypothesis and also with data from other laboratories (Lang, 1984), which suggests that imagery may be a fundamental aspect of emotion processing in humans.

Adult↗
PubMed1993

Lead stimulation effects on reflex blink, exogenous brain potentials, and loudness judgments.

Prepulse inhibition of the reflex blink by a weak stimulus shortly preceding a blink-eliciting stimulus has been described as a sensorimotor gating phenomenon that may protect processing of the first stimulus. To determine how a stimulus configuration that elicits prepulse inhibition also affects exogenous evoked potentials and perceived loudness of the paired stimuli, the three types of response were recorded simultaneously under four conditions: tone pairs of 75-110 dB and 75-75 dB and single control tones of each intensity. Two studies using different intrapair intervals found that blinks and exogenous potentials peaking after 50 ms were smaller for the second tone of pairs than for equal-intensity single tones. Pairing also reduced the loudness of 110-dB second tones, but the loudness of 75-dB first and second tones was unaffected or increased. These effects are discussed in terms of parallel processing of transient, unmodulated information in specific paths, steady-state modulated information in nonspecific paths, and a context-dependent effect on loudness judgments.

Acoustic Stimulation↗
PubMed1992

Reflex modification in psychosis-prone young adults.

The present study examined modification of the startle reflex in psychosis-prone and normal control subjects, using a continuous pure tone prestimulus (S1) and an intense white noise startle stimulus (S2). Reflex modification conditions consisted of stimulus pairs with onset asynchronies of 60, 120, and 2000 ms with a startle-alone condition as control. Startle was indexed by the eyeblink, which was measured by vertical electro-oculography. Subjects were identified as psychosis-prone by their high scores on the Perceptual Aberration or the Physical Anhedonia scales. Group differences in blink magnitude inhibition were observed between perceptual aberration and control subjects during short stimulus onset asynchronies, with perceptual aberrators showing significantly less inhibition than controls at 120 ms. No differences were evident between anhedonic and control subjects at the two short onset asynchronies nor were there any significant between-group differences when the interval between stimuli was long (2000 ms). These results suggest that subjects with perceptual aberrations may share with schizophrenics and other schizophrenia-spectrum subjects an underdeveloped mechanism which in normal subjects is presumed to operate during preattentive processing and functions to protect sensory information from the interfering effects of subsequent stimuli.

Acoustic Stimulation↗
PubMed1992

Affective response to color-slide stimuli in subjects with physical anhedonia: a three-systems analysis.

Emotion-provoking visual stimuli were presented to college undergraduates identified as anhedonic or normal, based on their scores on the Physical Anhedonia Scale (Chapman, Chapman, & Raulin, 1976). The affective stimuli (35 mm color slides) were chosen to elicit a wide range of both positive and negative emotion, with emotional response assessed through affective judgments, viewing time, and monitoring of a variety of physiological systems (heart rate, skin conductance, and facial musculature). The experiment was successful in demonstrating differential emotional response in the two subject groups; anhedonic subjects reported a less positive response than control subjects to positive and neutral stimuli and showed no association between heart rate and the emotion content of the slides. Paradoxically, activity in the muscles of facial expression was greater in anhedonic than control subjects during the presentation of both positive and negative slides. No between-group differences were noted in the viewing-time measure. The results are discussed in the context of Lang's bioinformational theory of human emotion (Lang, 1984, 1985).

Adult↗
PubMed1986

Relationships among negative life events, physiological reactivity, and health symptomatology.

College undergraduates classified as high (n = 25) and low (n = 25) on recent life stress participated in an experiment involving a novel laboratory stressor. Heart rate and pulse arrival time (PAT) were measured during baseline, anticipation, testing, and recovery periods of the experiment. The results did not replicate those obtained by Pardine and Napoli in that high and low life stress subjects did not show differential physiological reactions. In addition, regression analyses failed to demonstrate that physiological reactivity moderated the relationship between life stress and subsequent self-reported psychiatric or physical health symptomatology. The present findings demonstrated neither the stress-buffering effects of physiological reactivity nor a relationship between life stress and reactivity when the latter was conceptualized as an outcome.

Adult↗
PubMed1985

Pregnancies following the frozen storage of expanding human blastocysts.

Human blastocysts were frozen in Earle's solution containing pyruvate and human serum, using glycerol as cryoprotectant, and stored in liquid nitrogen. Thawed blastocysts were replaced in 11 patients, which resulted in two pregnancies. One blastocyst giving a pregnancy was hatching when replaced. Three parameters appeared to be important for embryo survival and implantation: the interval between ovulation and replacement of the thawed blastocysts, satisfactory embryonic development before freezing, and the stage of blastulation when cooling began.

Blastocyst↗
PubMed1985

Smooth pursuit eye movements in subjects reporting physical anhedonia and perceptual aberrations.

Two studies were conducted to evaluate the ability of schizotypic subjects to track the horizontal movement of a light source across the face of an oscilloscope. In the first experiment, subjects were selected based on their scores on the Physical Anhedonia Scale (Chapman et al., 1976). The high anhedonic group was found to be significantly more variable than the low anhedonic group and contained three subjects with particularly deviant smooth pursuit eye movements (SPEM). In the second study, an additional group of schizotypic subjects who scored high on the Perceptual Aberration Scale (Chapman et al., 1978) was selected. In this study, eye-tracking records produced by both the anhedonic and perceptual aberration subjects were more variable than those recorded from control subjects, and once again, the most deviant records were produced by a small subgroup (n = 10) of the schizotypic subjects. These questionnaire-identified schizotypes with poor tracking ability might comprise a group of subjects especially vulnerable to a future schizophrenia-like disorder.

Adolescent↗
PubMed1985

Cryopreservation of cleaving embryos and expanded blastocysts in the human: a comparative study.

The survival and implantation capacity of cryopreserved cleaving (5-cell to 10-cell) human embryos and expanded blastocysts was compared. Twice as many cleaving embryos were frozen as were expanding blastocysts because of the low developmental potential of human embryos in vitro. However, significantly more expanded blastocysts survived cryopreservation than cleaving embryos, and relatively more pregnancies were established by the replacement of thawed blastocysts than by the replacement of thawed cleaving embryos. Cleaving embryos from 26 women were thawed; 17 had thawed embryos replaced, and 4 subsequently became pregnant. Expanded blastocysts were thawed from 23 other women; 15 had thawed blastocysts replaced, and 8 subsequently became pregnant. The pregnancy of one patient in each group aborted; both patients were over 40 years of age. It is estimated that by maintaining the current policy of replacing three fresh embryos and freezing any remaining embryos when they reach blastocyst stage, the total incidence of pregnancy would increase by 3%.

Abortion, Spontaneous↗