The concept of physiological individual response specificity (IRS) was critically discussed. A review of empirical studies focused on IRS magnitude, stability, and personality correlates. Using difference scores, an average of 33% of the participants showed a significant IRS. IRS stability was found in only 15% of the participants. In some studies, IRS incidence was associated with neuroticism or stress coping styles. We suggest that the IRS concept should include not only purely constitutional but also situational and psychological determinants. Predictions from this revised biopsychological model were tested with a data set comprising 48 healthy male participants who completed six tasks, which were replicated three times in 1-week intervals. At Session 1, 21% of the participants displayed a significant IRS. IRS stability was found in only 8% of the participants. Participants with a significant IRS at Session 1 reported higher levels of fear (anger and happiness as covariates) and of pounding heart. Between-session IRS (trait-IRS) but not within-session IRS (state-IRS) was associated with trait anxiety.

The effect of aerobic training on parasympathetic reactivity to mental stress is unclear. Thus, the parasympathetic response, as assessed by time series analysis of heart period variability (HPVts), of 10 trained male runners (trained group), 10 inherently low resting heart rate untrained men (low HR group), and 10 normal resting HR men (control group) at rest and to two mental stressors was examined. Participants completed a mental arithmetic and Stroop task. Resting HPVts at high and medium frequencies was significantly greater for the trained and the low HR groups than for the control group. Significantly greater decreases in HPVts at the medium frequency during arithmetic recovery were measured for the trained and low HR groups compared with the response of the control group. Significantly greater decreases in HPVts at both the the high and medium frequencies during the first two epochs of the Stroop occurred only for the trained and low HR groups. These results suggest that the greater HPVts at rest and decline in HPVts during and after mental challenge is influenced by both aerobic training and genetic inheritance.

P300 differences for target (.10), nontarget (.10), and standard tones (.80) were assessed using a three-stimulus oddball paradigm in which participants responded only to the target (n = 12). Target/standard (easy or difficult) and nontarget/standard (large or small) pitch differences were manipulated orthogonally. In all conditions, target tones elicited a parietal P300, which was affected only by the target/standard discrimination ease. Nontarget in the easy/large and difficult/small conditions elicited a parietal but smaller P300 than the target but in the easy/small condition elicited similar ERPs to the standard. However, nontarget stimuli in the difficult/large condition elicited an anterior maximum and earlier P300 (P3a) component. The findings suggest that target P300s are not influenced by the nontarget stimulus configuration, whereas the nontarget P300 outcomes are determined directly by the stimulus context. The theoretical implications are discussed.

P300 latency is commonly thought to provide a chronometric index of the duration of perceptual processing. Because the evidence in favor of this assumption is controversial, we examined whether P300 latency is influenced by perceptual processes, response selection, and by motoric processes in two experiments using a two-choice spatial stimulus-response compatibility (SRC) task. Both experiments revealed additive effects of perceptual difficulty with spatial SRC in reaction time and P300 latency. In addition, Experiment 2 showed that P300 latency measured in average waveforms is insensitive to motoric processes. The influence of spatial SRC on P300 latency disagrees with the view that P300 latency is sensitive only to stimulus evaluation processes. However, P300 latency may be used to discriminate between influences on premotoric and motoric processing stages. A response conflict account for the SRC effect on P300 latency is suggested.

Persons at risk for hypertension may show elevated blood pressure (BP) at rest and during mental stress; however, the hemodynamics underlying the BP of those persons at high risk are not well characterized. We chose 21 high risk and 21 low risk men using their parental hypertension history and resting systolic blood pressures on two screenings. Then, on a day of extended rest versus a day with prolonged mental arithmetic and reaction time tasks, we examined whether high risk BP elevations reflected greater vascular resistance or cardiac output. High risk men had raised systolic/diastolic pressures (Fs = 74/15, ps < .0001/.0001) and higher vascular resistance (F = 6.6, p < .02) with minimal differences in heart rate and cardiac output. This finding implicates vascular resistance as the altered element in BP control in these high risk men tested in a familiar environment with minimal task-related threat.

Event-related potentials to binaural complex tones were recorded from 40 depressed outpatients and 22 normal control participants at 30 electrode sites. Patients did not differ from control participants in N1 or P3 amplitude but showed greater N2. N2 was greater over right than over the left hemisphere at lateral sites in patients and control participants. A P3 asymmetry was found for control participants and patients with low scores on a physical anhedonia scale, but not for patients with high anhedonia scores. Topographic (local Laplacian) maps corresponding to P3 showed greater radial current flow over right than over left central regions in control participants. Patients with high anhedonia did not show this asymmetry, whereas patients with low anhedonia showed an intermediate asymmetry. These findings support the hypothesis that anhedonic depression is associated with dysfunction of right hemisphere mechanisms mediating the processing of complex pitch information.

We examined developmental differences in smooth pursuit eye tracking proficiency in a large sample of preadolescent, adolescent, and adult males. Smooth pursuit was quantified using general measures of oculomotor functioning and by examining the frequency and dynamic characteristics of specific saccadic events. Examination of age effects using general measures indicated that, by late adolescence, the smooth pursuit system reached adult levels of functioning. No significant differences were found between the adolescent and adult groups on most global measures. However, both groups had better eye tracking than the preadolescent group, suggesting that during preadolescence the oculomotor system is still developing and is not yet capable of optimal performance. Examination of the frequency and dynamic characteristics of the saccadic events yielded additional information regarding the nature of the smooth pursuit eye tracking differences of the three age groups.

The effects of methylphenidate (0.3 mg/kg) on young adults' paired-associate learning (PAL) of consonant–vowel–consonant (CVC) pairs and concomitant event-related potentials were assessed. The stimulant elevated mood and heart rate but did not affect PAL performance. For the first CVC, there were amplitude increases with learning for P3b at Pz, P2 at midline sites, and for a negative slow wave at Cz. For the second CVC, P3b and positive slow wave amplitude declined with learning. Increases in P3b amplitude to the first CVC were attributed to increments in stimulus meaningfulness. Decreases in P3b amplitude to the second CVC were interpreted as resulting from fewer disconfirmed expectations of feedback. The negative slow wave following the first CVC was viewed as a contingent negative variation. Methylphenidate increased parietal P3b amplitude for CVC 2, averaged over learning phases.

A heartbeat detection task, based on the method of constant stimuli (MCS), requires participants to judge which of a series of tones presented at different delays following a heartbeat are coincident with the heartbeat. Two experiments were conducted to test the validity of the MCS in assessing individual differences in the ability to detect heartbeat sensations. The first experiment found the MCS to be valid, in that about one-third of subjects met the criterion for classification as heartbeat detectors when the tones were presented with respect to their actual heartbeats, but only one subject met the criterion when the tones were presented with respect to previously recorded heartbeats. The second experiment manipulated the timing of the comparison intervals (i.e., R + 100–600 ms rather than R + 0–500 ms) to examine the validity of the median R-wave to tone interval as an index of temporal location of perceived heartbeats, and found it to be a valid index.

Psychophysiological “preparatory” responses may or may not depend on a focused expectation of when a stimulus will occur. Changes in heart rate, pupillary diameter, and brain potentials were examined during trials in which foreperiod of a simple reaction time (RT) task was fixed or unpredictable. Trials were also included in which stimuli for the speeded motor reaction were triggered by psychophysiological changes occurring spontaneously in the foreperiod. Thirty-two college-aged volunteers equally divided by gender participated in the experiment. Reducing expectancy, by using nonaging foreperiods, eliminated transient prestimulus psychophysiological responses but failed to eliminate slow changes over the foreperiod—slowing of heart rate, dilation of the pupil, and cortical surface negativity. Triggering the reaction stimulus by physiological changes did not influence RT. Correlations between psychophysiological changes in the foreperiod and between these changes and RT were generally low. The results were consistent with a multiprocess view of preparation.

A new method based on jackknifing is presented for measuring the difference between two conditions in the onset latencies of the lateralized readiness potential (LRP). The method can be used with both stimulus- and response-locked LRPs, and simulations indicate that it provides accurate estimates of onset latency differences in many common experimental conditions.

A new method based on jackknifing is presented for measuring the difference between two conditions in the onset latencies of the lateralized readiness potential (LRP). The method can be used with both stimulus- and response-locked LRPs, and simulations indicate that it provides accurate estimates of onset latency differences in many common experimental conditions.

The P300 component and the oscillatory 4–7 Hz electroencephalographic activity of auditory event-related brain potentials (ERPs) were assessed to study differences between passive and oddball task conditions. Theta responses from 15 adults were analyzed for single-sweep amplitude, phase locking, and enhancement against prestimulus activity. ERPs were characterized by enhanced and strongly phase-locked theta oscillations in the early (0–300 ms) poststimulus epoch, with only the late (300–600 ms) theta responses at Fz and Pz affected by the oddball condition. P300 was strongly associated not only with the concurrent theta oscillations but also with the evoked theta activity preceding P300 (0–300 ms). It was concluded that single theta response parameters can reveal specific functional differences between passive and oddball conditions and that a strong relationship exists between the theta frequency component and the time domain P300 ERP component.

The P300 component and the oscillatory 4–7 Hz electroencephalographic activity of auditory event-related brain potentials (ERPs) were assessed to study differences between passive and oddball task conditions. Theta responses from 15 adults were analyzed for single-sweep amplitude, phase locking, and enhancement against prestimulus activity. ERPs were characterized by enhanced and strongly phase-locked theta oscillations in the early (0–300 ms) poststimulus epoch, with only the late (300–600 ms) theta responses at Fz and Pz affected by the oddball condition. P300 was strongly associated not only with the concurrent theta oscillations but also with the evoked theta activity preceding P300 (0–300 ms). It was concluded that single theta response parameters can reveal specific functional differences between passive and oddball conditions and that a strong relationship exists between the theta frequency component and the time domain P300 ERP component.

The impact of artifacts on estimates of heart period variability were evaluated by modeling the effects of missed R-waves and spurious R-wave detections in actual and simulated heart period series. Results revealed that even a single artifact, occurring within a 128-s interbeat interval series, can impart substantial spurious variance into all commonly analyzed frequency bands, including that associated with respiratory sinus arrhythmia. In fact, the spurious variance introduced by a single artifact may be greater than that associated with true basal heart period variability and can far exceed typical effect sizes in psychophysiological studies. The effects of artifacts are not related to a specific analytical method and are apparent in both frequency and time domain analyses. Results emphasize the importance of artifact detection and resolution for studies of heart period variability.

The impact of artifacts on estimates of heart period variability were evaluated by modeling the effects of missed R-waves and spurious R-wave detections in actual and simulated heart period series. Results revealed that even a single artifact, occurring within a 128-s interbeat interval series, can impart substantial spurious variance into all commonly analyzed frequency bands, including that associated with respiratory sinus arrhythmia. In fact, the spurious variance introduced by a single artifact may be greater than that associated with true basal heart period variability and can far exceed typical effect sizes in psychophysiological studies. The effects of artifacts are not related to a specific analytical method and are apparent in both frequency and time domain analyses. Results emphasize the importance of artifact detection and resolution for studies of heart period variability.