Two studies examined the effects of breast-feeding on maternal cardiovascular function. In the first experiment, groups of breast-feeding and bottle-feeding women were compared on preejection period (PEP), heart rate (HR), cardiac output (CO), and total peripheral resistance (TPR) recorded for 1-min periods before and during standard laboratory stressors. Compared with bottle-feeders, breast-feeders had higher CO throughout the session, and greater decreases in CO and increases in TPR during cold pressor. In the second experiment, HR and blood pressure (BP) were compared before and after one breast-feeding and one bottle-feeding session in a within-subjects design. Both feeding methods increased BP but decreased HR, and systolic BP was higher for the breast-feeding than the bottle-feeding condition. Both studies support the notion that breast-feeding alters maternal cardiovascular function, possibly through the actions of oxytocin.

Startle modulation was investigated as participants first anticipated and then viewed affective pictures in order to determine whether affective modulation of the startle reflex is similar in these different task contexts. During a 6-s anticipation period, a neutral light cue signaled whether the upcoming picture would portray snakes, erotica, or household objects; at the end of the anticipatory period, a picture in the signaled category was viewed for 6 s. Male participants highly fearful of snakes were recruited to maximize emotional arousal during anticipation and perception. Results indicated that the startle reflex was potentiated when anticipating either unpleasant (phobic) or pleasant (erotic) pictures, compared to neutral stimuli, whereas during perception, reflexes were potentiated when viewing unpleasant stimuli, and reduced when viewing pleasant pictures. The startle reflex is modulated by hedonic valence in picture perception, and by emotional arousal in a task context involving picture anticipation.

This study provides the first psychophysiological analysis of narcissism by measuring autonomic responses during active and passive anticipatory coping in 40 undergraduate men who scored high or low on the Narcissistic Personality Inventory (NPI). Compared to the low NPI group, the high NPI group showed greater preejection period (PEP) shortening, cardiac deceleration, and skin conductance response (SCR) habituation during anticipation of an aversive stimulus (p < .02). As expected, SCR and PEP reactivity were greater during active than passive coping. In the case of PEP, this effect emerged only in the low NPI group; the high NPI group showed the greatest PEP reactivity during the first task, regardless of coping demands. These data support hypothesized relationships among narcissism, psychopathy, and psychological predictors of cardiovascular disease, and suggest that a psychobiological dimension may underlie important features of narcissism.

We tested the assumption that the slope of the within-individual regression equation of respiratory sinus arrhythmia (RSA) normalized by tidal volume (VT) upon respiratory cycle length (TTOT) can characterize ventilatory RSA modulation independent of cardiac vagal tone, whereas the intercept is varying as a function of vagal tone. We also explored whether a variation of VT is necessary to estimate slopes reliably. Four 3-min sequences paced at 8–18 cycles/min were performed supine and standing. Participants also breathed the same sequences in supine posture with voluntarily varying VT. The mean slope of RSA/VT upon TTOT was identical, and the mean intercept was lower for standing than supine (spontaneous VT) conditions. Stability of slopes was low between body postures, and was higher between spontaneous VT versus varying VT at the same body posture. The regression of RSA/VT upon TTOT allows for a valid estimation of ventilatory influences on RSA.

Language processing was investigated using event-related potentials obtained using a multichannel (58-channel) EEG system, with regard to semantic dependency (i.e., selectional restriction between a verb and the arguments it takes; the SR type) and syntactic dependency between sentence-final particles and interrogative phrases (the WH-Q type) in Japanese. It was found that semantic violations elicited the conventional N400, which was distributed in the bilateral occipital and the right temporal regions, and that the syntactic violations elicited the P600 in a broad area, predominantly in the centroparietal regions. Scalp current density mappings suggested that the right temporal cortex plays a significant role in integrating pieces of contextual information, especially when it is difficult to integrate a word in the context of a sentence, and that the P600 was connected to the syntactic processes conceivably indexed by the left temporal current sink with a relatively early onset.

We developed a new model of psychological “open-field” stress in freely moving rats. Blood pressure and heart rate of the rats were measured by radiotelemetry and behavior analyzed by video tracking software. Open-field exposure induced marked increases in blood pressure and heart rate. Repeated daily exposure induced pressor responses that were slightly higher on Day 4 when compared to Day 1. Pretreatment with the β1-adrenoceptor antagonist atenolol inhibited the tachycardia whereas the ganglion blocker pentolinium inhibited the pressor response, indicating involvement of the sympathetic nervous system. Pretreatment with diazepam prevented the novelty stress-induced pressor response and reduced the tachycardia. These results show that the psychological stress of exposing rats to an open field induces marked cardiovascular effects that are mediated by sympathetic hyperactivity. This model is unique in that it focuses on psychological stress and allows concomitant measurement of blood pressure, heart rate, and behavior in freely moving rats.

Schizophrenia patients and their relatives have saccadic abnormalities characterized by problems inhibiting a response. The dorsolateral prefrontal cortex and its associated circuitry ostensibly mediate inhibition and support correct delayed response performance. In this context, two components of delayed response task performance are of interest: memory saccade metrics and error saccades made during the delay. To evaluate these variables, an ocular motor delayed response task was presented to 23 schizophrenia patients, 25 of their first-degree biological relatives, and 19 normal subjects. The measure that best differentiated groups was an increased frequency of error saccades generated during the delay by schizophrenia subjects and relatives. Decreased memory saccade gain also characterized patients and relatives. The similar pattern of results demonstrated by the patients with schizophrenia and their relatives suggests that performance on ocular motor delayed response tasks, either alone or in combination with other saccadic variables, may provide useful information about neural substrates associated with a liability for developing schizophrenia.

The brain's responsiveness to changes in sound frequency has been demonstrated by an overwhelming number of studies. Change detection occurs unintentionally and automatically. It is generally assumed that this brain response, the so-called mismatch negativity (MMN) of the event-related brain potential or evoked magnetic field, is based on the outcome of a memory-comparison mechanism rather than being due to a differential state of refractoriness of tonotopically organized cortical neurons. To the authors' knowledge, however, there is no entirely compelling evidence for this belief. An experimental protocol controlling for refractoriness effects was developed and a true memory-comparison-based brain response to pitch change was demonstrated.

The n-back task was hypothesized to be a dual task, permitting the imposition of parametrically increasing attentional and working memory demands, while keeping constant the demands of an embedded matching subtask. Visual targets were presented for 200 ms every 2.2 s at pseudorandomly varying positions on a computer screen. Participants were required to remember the most recent 0, 1, 2, or 3 positions and responded with a choice button push to whether the current target position matched the position presented n items previously. P300 peak latency was constant across n-back tasks, reflecting constant perceptual and cognitive demands of the matching subtask. P300 peak amplitude decreased with increasing memory load, reflecting reallocation of attention and processing capacity away from the matching subtask to working memory activity. These data support a dual-task nature of the n-back, which should be considered when employing this paradigm.

The activity of the agonist muscles was recorded during the performance of a two-choice visual reaction time (RT) task in which the compatibility of the stimulus–response mapping was manipulated. Correct trials were distinguished according to whether or not the activation of the agonist of the required response was preceded by an activation of the agonist of the nonrequired response. Double activation trials were more numerous for the incompatible than for the compatible mapping. Furthermore, these trials yielded longer RTs than the single muscular activation trials. These results suggest that initial activations of nonrequired responses are more frequently aborted and corrected when the mapping is incompatible than when it is compatible. This finding supports the dimensional overlap model of stimulus–response compatibility (S. Kornblum, T. Hasbroucq, & A. Osman, 1990).

The mismatch negativity (MMN) was used as a probe to evaluate changes, with age, of transient auditory memory. Subjects were 16 young (M = 23 years) and 16 old (M = 72 years) people. Standard auditory stimuli were presented in trains of eight tones (1000 Hz) with either a 1-s or 8-s intertrain interval (ITI). Occasionally, the first stimulus of a train was replaced with a 1200 Hz tone (deviant). The MMN was recorded while subjects watched a silent movie and ignored the sounds. Both groups of subjects showed an MMN response to deviant stimuli under the 1-s ITI condition, but MMNs were only seen for some subjects under the 8-s ITI condition. After MMN recording, subjects performed a discrimination task to the tones used for recording MMNs. Accuracy for both groups was near 100% at both ITIs. These results suggest that generation of MMN is a function of the perceptual grouping of the acoustical stimuli and that the integrity of perceptual grouping may be maintained with increased age.

The current study was designed to clarify the psychological functions most closely associated with frontal brain asymmetry. Electroencephalography (EEG) was recorded from 60 participants while they performed a delayed reaction time (RT) task that included manipulations of incentive, expectancy, and response. Significant alpha asymmetry effects were reflected in topographic differences across anterior EEG sites. Variations in monetary incentives resulted in parametric changes in anterior frontal alpha asymmetry. Manipulations of outcome expectancies were related to mid-frontal EEG changes that differed for men and women. Varied response requirements were related to central asymmetry patterns. Taken together, the findings suggest that regionally specific patterns of frontal asymmetry are functionally related to particular aspects of approach–withdrawal tendencies involved in the temporal guidance and regulation of goal-directed behavior.

We describe a simple method for computer quantification of eye movement (EM) potentials during REM sleep. This method can be applied by investigators using either period-amplitude (PA) or Fast Fourier Transform (FFT) spectral EEG analysis without special hardware or computer programming. It provides good correlations with visual ratings of EM in baseline sleep and after administration of GABAergic hypnotics. We present baseline data for both PA and FFT measures for 16 normal subjects, studied for 5 consecutive nights. Both visually rated and computer-measured EM density (EMD) showed high night-to-night correlations across baseline and drug nights and the computer measures detected the EMD suppression that is produced by GABAergic drugs. Measurement of EM in addition to stage REM provides biologically significant information and application of this simple computer method, which does not require pattern recognition algorithms or special hardware, could provide reliable data that can be compared across laboratories.

Increased frequency of anticipatory saccades during smooth pursuit eye movements is a potential marker of genetic risk for schizophrenia. Postsaccadic slowing criteria are used to separate anticipatory from other types of saccades. However, the necessary duration of slowed pursuit required to identify an anticipatory saccade remains undetermined. We explored the effect of various postsaccadic slowing duration criteria on effect size in a comparison of younger and older schizophrenic and normal adults. For large anticipatory saccades, varying the duration of postsaccadic slowing criteria did not notably change effect size. For smaller leading saccades, a limited 50-ms duration postsaccadic slowing criterion produced the largest effect size (1.54), and maintained a similar effect size across a broad age range. Leading saccades with a limited duration postsaccadic slowing criteria are a possible marker of genetic risk for schizophrenia.

Temporal auditory processing deficits are thought to play an important role in some pathologies of speech understanding difficulties. The purposes of the present study were to determine whether short silent gaps within a pure tone can be used to elicit mismatch negativity (MMN) as an objective measure of temporal resolution, and to investigate the relation between MMN and performance on a behavioral gap-detection task. The stimuli used for both tasks were 1-kHz sinusoids presented in a low-pass masking noise. Behavioral gap-detection thresholds were determined using an adaptive three-alternative forced-choice procedure. To elicit MMN, a series of deviant stimuli with varying gap durations was generated and presented in an oddball paradigm among standard stimuli without a gap. Only the gaps larger than the mean behavioral gap-detection threshold evoked a clear MMN. There was no clear relation between psychoacoustic and MMN thresholds.

One challenge in the analysis of event-related potentials (ERPs) is to identify task-related differences in scalp topography. The multivariate Partial Least Squares (PLS) analysis was used to identify the spatiotemporal distribution of ERP differences related to experimental manipulations. Two simulations included latency shifts and amplitude changes at peaks with temporal overlap. PLS identified effects only at modeled timepoints and electrodes. In contrast, principal components analysis identified differences at most timepoints. We also demonstrated that PLS identified combinations of waveform differences, not isolated sources. ERP components in an auditory oddball task were also assessed with PLS. The primary distinction was between ERPs on hit and correct rejection trials, expressed at multiple timepoints and electrodes. PLS provides a mechanism to describe experimental differences in ERP waveforms, simultaneously across the head.

White and Yee (1997) found that normal suppression of the P50 component of the event-related potential was disrupted during a paired-click paradigm when nonpsychiatric subjects performed mental arithmetic (MA) problems aloud, concurrently with the presentation of auditory stimuli. In fact, the degree of disruption reflected in the P50 suppression ratio fell within the range that is typically observed in schizophrenia patients. The present study was conducted to clarify the processes that might underlie the apparent disruption of P50 suppression during performance of an oral MA task. Participants completed a series of tasks designed to examine the impact of competing cognitive activity, competing auditory stimulation, muscle activity, and acute psychological stress on P50 amplitude and P50 suppression. Results suggested that psychological stress and heightened facial muscle activity may exert modulatory effects on P50 suppression.

We used a novel application of principal components analysis (spatiotemporal PCA) to decompose the event-related brain potentials (ERPs) obtained with a dense electrode array, with the purpose of elucidating the late ERP components elicited by deviant stimuli under “attend” and “ignore” conditions. First, a “spatial” PCA was performed to identify a set of scalp distributions (spatial factors or “virtual electrodes”) that accounted for the spatial variance in the data set. The data were expressed as spatial factor scores or “virtual ERPs” measured at each of the virtual electrodes. These virtual ERPs were submitted to a “temporal” PCA, yielding a set of temporal factors or “virtual epochs.” Statistical analyses of the temporal factor scores found that (1) attended deviant stimuli elicited the P300 and Novelty P3 components, the latter being largest for highly salient nontargets; (2) “ignored” deviants elicited a small Novelty P3, and depending on the primary task, a small P300; and (3) the classical Slow Wave consisted of separate frontal-negative and posterior-positive components.

Brain mechanisms extracting invariant information from varying auditory inputs were studied using the mismatch-negativity (MMN) brain response. We wished to determine whether the preattentive sound-analysis mechanisms, reflected by MMN, are capable of extracting invariant relationships based on abstract conjunctions between two sound features. The standard stimuli varied over a large range in frequency and intensity dimensions following the rule that the higher the frequency, the louder the intensity. The occasional deviant stimuli violated this frequency–intensity relationship and elicited an MMN. The results demonstrate that preattentive processing of auditory stimuli extends to unexpectedly complex relationships between the stimulus features.

The purposes of the present study were to determine the autonomic origins of a bradycardiac response to a moderate intensity nonsignal auditory stimulus and the changes in autonomic cardiac control of this response as a function of habituation. Pure tone stimuli were repeatedly presented to participants while phasic changes in heart period (HP), preejection period (PEP), and respiratory sinus arrhythmia (RSA) were observed. Tone stimuli initially elicited an increase in HP, an increase in RSA, and a decrease in PEP, suggesting a coactivation of the parasympathetic and sympathetic inputs mediating changes in the bradycardiac HP response. As expected, HP responses habituated with repeated presentations of the tones. PEP and RSA responses, however, demonstrated different habituation rates than HP. These data demonstrate that cardiodeceleratory responses to nonsignal stimuli can arise from changes in activity of both autonomic divisions and document the importance of considering the autonomic origins of habituating cardiac responses in order to fully understand the process of response habituation.