Presentation to John Cacioppo on the occasion of the Award for Distinguished Contributions to Psychophysiology, Saturday October 21, 2000, San Diego.

The present study investigated the effect of target stimulus probability on the P3 component of the respiratory-related evoked potential (RREP). A single respiratory stimulus paradigm was employed where normal breaths served as standard stimuli and occluded breaths presented at various probability levels served as target stimuli. EEG was recorded from 29 channels in young adults in two conditions. In Condition 1, occlusions were presented at target probabilities of 0.5, 0.33, 0.25, 0.2, 0.1, and 0.05, that is, every 2nd, 3rd, 4th, 5th, 10th, and 20th breath. Order of target probability presentation varied randomly. Condition 2 used the same target probabilities, but held breathing rate constant by using a paced respiration task. Results indicated that P3 amplitude was significantly affected by stimulus probability, such that the component showed an inverse relationship with probability. This effect was similar between conditions. However, P3 amplitude reduced and latency increased when the secondary task of paced respiration was introduced. These data suggest that models developed to describe the effect of stimulus probability on the amplitude of visual and auditory P3 components are applicable to the respiratory somatosensory modality.

Previous research has suggested that the stimulus-preceding negativity (SPN) is largely independent of stimulus modality. In contrast, the scalp topography of the event-related desynchronization (ERD) related to the anticipation of stimuli providing knowledge of results (KR) is modality dependent. These findings, combined with functional SPN research, lead to the hypothesis that anticipatory ERD reflects anticipatory attention, whereas the SPN mainly depends on the affective-motivational properties of the anticipated stimulus. To further investigate the prestimulus ERD, and compare this measure with the SPN, 12 participants performed a time-estimation task, and were informed about the quality of their time estimation by an auditory or a visual stimulus providing KR. The KR stimuli could be either intact or degraded.

Auditory degraded KR stimuli were less effective than other KR stimuli in guiding subsequent behavior, and were preceded by a larger SPN. There were no effects of degradation on the SPN in the visual modality. Preceding auditory KR stimuli no ERD was present, whereas preceding visual stimuli an occipital ERD was found. However, contrary to expectation, the latter was larger preceding intact than preceding degraded stimuli. It is concluded that the data largely agree with an interpretation of the pre-KR SPN as a reflection of the anticipation of the affective-motivational value of KR stimuli, and of the prestimulus ERD as a perceptual anticipatory attention process.

Event-related potentials (ERPs) and behavioral responsiveness were investigated during the transition from wakefulness to sleep. Ten participants were presented with an auditory oddball task during repeated sleep onset periods. The EEG was recorded from 29 different scalp sites. A 1500-Hz tone pip was presented infrequently (p = .04) within a series of lower pitch 1000-Hz “standard” stimuli (p = .96). Participants were required to button press upon detection of the rare “target” stimulus. During wakefulness, almost all targets were detected. A large amplitude P300 was observed to these detected targets. This P300 was maximum over parietal areas of the scalp. During stage 1 sleep, subjects continued to respond on 47% of trials. The parietal P300 amplitude remained large to these detected targets. It was, however, much attenuated at frontal sites. When the participant failed to detect the target in either stage 1 or 2, no P300 was visible. P300 is thus associated with behavioral detection of the target stimulus, whether in wakefulness or stage 1 “sleep.” Trials were also sorted by reaction time (RT), in which bins 1–3 represented increasingly long RT. In the waking state, P300 amplitude did not significantly vary across the different bins. Although mean RT latency varied by 512 ms from bin 1 to bin 3, P300 latency varied by only 25 ms. Differences in RT are thus probably due to response-related processes rather than stimulus classification time.

During listening to a musical piece, unexpected harmonies may evoke brain responses that are reflected electrically as an early right anterior negativity (ERAN) and a late frontal negativity (N5). In the present study we demonstrate that these components of the event-related potential can be evoked preattentively, that is, even when a musical stimulus is ignored. Both ERAN and N5 differed in amplitude as a function of music-theoretical principles. Participants had no special musical expertise; results thus provide evidence for an automatic processing of musical information in “nonmusicians.”

Individuals with posttraumatic stress disorder (PTSD) have been found to show several event-related brain potential (ERP) abnormalities including reduced target P3b amplitude, P50 suppression, and P2 amplitude/intensity slope. Female Vietnam nurse veterans with (n = 29) and without (n = 38) current PTSD completed P50 paired-click, three-tone “oddball” and four-tone stimulus-intensity modulation procedures. Opposite to previous findings, the current PTSD group had larger target P3b amplitudes and increased P2 amplitude/intensity slopes. Reduced P50 suppression was associated with increased severity of general psychopathology, but not with PTSD diagnosis. Findings suggest that target P3b amplitude and P2 amplitude/intensity slope abnormalities reflect different pathophysiological processes. Future research is needed to determine whether the opposite ERP abnormalities observed in this PTSD sample reflect gender-, trauma-, or sample-specific findings.

A quantitative, theory-driven model of hemodynamics was developed, relating reactivity in blood pressure to orthogonal dimensions of “hemodynamic profile” and “compensation deficit,” which were derived from the (multiplicative) interaction of cardiac output and total peripheral resistance. A Finapres 2300e was used to estimate blood pressure, cardiac output, and total peripheral resistance in 100 healthy men and women during mental arithmetic and cold pressor tasks on two occasions. Results were consistent with model predictions. As predicted, cardiac output and peripheral resistance reactions were curvilinearly related, and blood pressure reactivity was strongly related to compensation deficit (r = .76–.89). Conversely, the orthogonally defined hemodynamic profile remained independent of blood pressure reactivity (r = .11 or less). The data show that the present model overcomes several difficulties and inconsistencies in previous attempts to obtain an independent measure of hemodynamic profile. The new model could help to elucidate sources of cardiovascular pathogenesis not suggested from the study of blood pressure reactivity alone.

The human infant's neurophysiological responses to feeding are poorly understood. We found recently a significant increase of EEG amplitude in the newborn during nutritive feeding, but not during pacifier sucking. In this study, we report EEG responses to feeding in 13 infants at the ages of 3 and 6 months. The undifferentiated response of the newborn was found to wane until the age of 3 months, whereas in 6-month-old infants, relatively abundant rhythmic 3–5 Hz theta activity was recorded during feeding with an amplitude maximum in right posterior areas. Cessation of feeding was followed by cessation of theta activity. The rhythmic 3–5 Hz theta response to feeding is likely to represent emotional arousal, as it is similar to previous findings showing posterior theta increase in other settings connected with emotional arousal in infants.

Acute stress elevates blood lipids, with the largest increases among men and postmenopausal women. The mechanisms for the effect are unknown, but may be due to altered lipid metabolism. This study investigated if acute stress induces transient reductions in triglyceride clearance in middle-aged men and women, and determined if gender and menopause affect triglyceride metabolism. Of the 35 women, half were premenopausal, and half were naturally postmenopausal; men (n = 35) were age matched. Clearance of an intravenously administered fat emulsion was assessed twice: once during a nonstress session, and again during a stress-testing session. During the stress session, a battery of behavioral stressors (serial subtraction, speech, mirror tracing, and Stroop) were performed for 40 min. The clearance rate of exogenous fat was significantly diminished during the stress, relative to the nonstress session. Women had more efficient clearance, relative to men, but there were no effects of menopausal status. The diminished ability to clear an intravenous fat emulsion during stress suggests one mechanism for stress-induced elevations in lipids.

We studied the modulation of oscillatory resistance (Ros) by viewing and imagery of affective pictures. Thirty nonasthmatic participants viewed 36 affective slides precategorized as positive, neutral, and negative in valence. Each picture was presented for 15 s, followed by an imagery epoch of 15 s. Ros, facial EMGs, respiration, skin conductance response, heart period, and respiratory sinus arrhythmia were measured throughout the session, as well as viewing time and ratings of pleasure, arousal, and interest. Increases of Ros were observed for negative pictures, and little changes for positive or neutral pictures. Other physiological parameters did not mirror this response pattern, leaving no clear indication for a ventilatory or vagal origin of Ros changes. Overall differences between behavioral contexts of visual processing and imagery revealed evidence for a coupling of cardiac and respiratory responses, which included changes in Ros. The findings in Ros are discussed in the light of earlier discrepant findings on the affective modulation of airway resistance and cardiac activity.

This study examined stress cortisol responses and cognitive performance. We initially measured cortisol responses of 40 right-handed healthy male volunteers to counterbalanced mental arithmetic and public speaking stressors. We then examined the relationship between cortisol reactivity and dichotic listening and mental arithmetic performance. High cortisol responders made more errors and completed fewer mental arithmetic items than low reactors. On dichotic listening, high responders tended toward better performance in all conditions and to both ears. High responders showed better performance to the right ear in the forced right than in the nonforced condition, whereas no difference between these conditions was found in low responders. High cortisol responders may have an increased focus on sensory stimuli and a decreased allocation of resources to working memory tasks.

A visual Simon task was used to study the influence of aging on visuospatial attention and inhibitory control processes. Responses were much slower for elderly than for young participants. The delay in trials in which stimulus and response side did not correspond as compared to when they did correspond (the Simon effect) was larger for older people, even after correcting for general slowing due to aging. The slowing of responses reflected a slowing of internal processing, as indicated by progressively larger delays of the peak latencies of the N1, the posterior contralateral negativity (PCN), and P3. A comparison between the amplitudes of the PCN and early lateralized readiness potential (pre-LRP) indicated that transmission from posterior sites (PCN) to the motor cortex may be affected by age. The data support the view that aging affects an inhibitory process that controls direct visuomotor transmission.

Both the amplitude and latency of P300 vary with changes in stimulus parameters. Stimuli at intensities or pitch separations near threshold evoke a smaller and later P300. P300 is also affected by extraneous stimulus parameters in tasks where stimulus frequency separation is large and stimuli are well above intensity thresholds. For example, the presence of background white noise when tones are suprathreshold and easily detectable has been reported to increase P300 latency. However, the effects of background masking noise on P300 amplitude and scalp topography have not been reported. Subjects performed an oddball task both in the presence and in the absence of background noise. Performance accuracy was unaffected by background noise. P300 showed latency increases when noise was present, but P300 peak amplitude was unaffected. P300 scalp topography was stable across both conditions. P300 latency is affected by background noise, even when performance is not, but amplitude and amplitude topography remain unaffected.