Subcomponents of the N200 component of the event-related brain potential believed to be differentially sensitive to involuntary and voluntary cognitive processes were examined. Nonpatients (N = 131) identified initially by the Chapman and Depue research scales and classified later on the basis of diagnostic symptom clusters and family psychiatric history provided converging evidence for an intact mismatch negativity subcomponent. In contrast, the N2b subcomponent distinguished several groups of subjects. Results suggested abnormal voluntary cognitive processing, perhaps reflecting compensatory efforts in subjects at risk for or manifesting psychopathology, particularly those showing negative symptoms.

Our recent work suggests that innocuous somatosensory activity elicited by a brief electrical stimulus is inhibited by pain evoked by the same electrical stimulus but not by pain evoked by continuous heat. These results led to the hypothesis, tested in the present experiment, namely that pain only inhibits innocuous somatosensation when the painful and innocuous stimuli have short durations and close temporal and spatial overlap. A painful 200-ms laser pulse did not produce a decrease in the perceived magnitude of the innocuous electrical stimulus or in the amplitude of a scalp potential that earlier work suggested is generated by neurons involved in innocuous somatosensation. Hence, the pain-related inhibition of innocuous somatosensation observed in these electrical studies cannot be attributed solely to the duration or to the temporal and spatial overlap of the innocuous and painful stimuli. Laser pain did produce a small increase in the subjective magnitude of the innocuous electrical stimulus, which the electrophysiological evidence suggests might be due to a change in the late- but not the midlatency responses in the central innocuous somatosensory pathways.

This study investigated the role and time-course of phonology in accessing meaning during silent reading. In Experiment 1, the homophone effect was replicated in a semantic categorization task in French. When deciding whether a stimulus belonged to a semantic category (FOOD), subjects made more errors to homophones (MEET) than to orthographic controls (MELT). In Experiment 2, event-related brain potentials (ERPs) were used to study the online development of this effect. If access to meaning was mediated by phonology, smaller N400 components should be obtained to homophones than to orthographic controls. The ERP data exhibited a full-blown N400 component to homophones that did not differ from the N400 to controls. No differences between homophones and controls were found before the N400. After the N400, however, homophones differed from controls, with ERPs to homophones being similar to those of correct category exemplars. The results suggest that the final selection of a word's meaning does not depend on its phonological form. This result is incompatible with a strong phonological view according to which the only way to meaning is via a word's phonology.

Evidence suggests that a distinction between anxious apprehension (worry) and anxious arousal (somatic anxiety) might account for some discrepancies in the literature examining brain activity in anxiety. In the current study, we compared the regional brain activity of groups of anxious apprehension and anxious arousal participants, selected on the basis of self-report measures previously shown to be psychometrically distinct from each other and from a specific measure of depression. Patterns of hemispheric asymmetry in electroencephalogram alpha distinguished the two types of anxiety, with the anxious arousal group showing more right than left activity. No significant asymmetry was found for the anxious apprehension group. The results provide further support for contrasting patterns of brain activity in distinct types of anxiety. Research is needed to specify further the topography and functional significance of this distinction.

Baroreflex (BR) testing with phenylephrine (PE) and amyl nitrite (AN) provided an opportunity to evaluate the ability of impedance cardiography (IC) to track the rapid hemodynamic (HD) changes elicited by these drugs. The AN response was measured after inhalation and the PE response was measured after a bolus injection in 19 subjects on two occasions. High reliability was observed for all of the HD measures. Blood pressure (BP), peripheral resistance (PR), and preejection period (PEP) decreased significantly after administration of AN, whereas heart rate (HR) and cardiac output (dotted Q) increased. BP and total PR increased significantly after administration of PE; HR and dotted Q decreased and PEP did not change significantly. Stroke volume did not change significantly with either drug. The BR slope was reliably elicited with AN and PE. The IC and Finapres BP consistently detected short-term changes in HD responses to AN and PE. The pharmacological interventions demonstrated that IC measures followed the course predicted by the actions of the drugs. Change in PEP and dZ/dt reflected increased contractility. The BR sensitivity was also reproducible.

Associations between trait dominance and cardiovascular reactivity were examined in previously unacquainted healthy men and women. Subjects participated in three mixed-gender dyadic interactions with the same partner while their cardiovascular responses were assessed. Among men, but not women, trait dominance was positively and significantly associated with systolic blood pressure reactivity. For men and women, diastolic blood pressure reactivity was positively and significantly associated with trait dominance while participants prepared to interact and with partner's trait dominance while they interacted. All effects held after controlling for trait hostility. Dominance merits attention as a correlate of cardiovascular reactivity, a finding that parallels emerging patterns in the cardiovascular disease literature. Gender and gender-related social factors as potential moderators of this relationship are discussed.

In an electroencephalographic (EEG) study of 27 pairs of monozygotic (MZ) twins discordant for schizophrenia, 13 pairs of MZ twins concordant for schizophrenia, 40 pairs of healthy MZ twins, and 91 healthy, unrelated subjects with repeated assessments, we investigated (a) the trait quality of brainwave patterns with respect to interindividual differences, intraindividual stability over time, and within-pair MZ concordance; (b) the EEG characteristics that enable discrimination between affected and unaffected individuals; and (c) the EEG characteristics that reflect the severity of illness. In comparison with healthy control subjects, the MZ twins who were discordant and concordant for schizophrenia exhibited a much lower within-pair EEG concordance, so that EEG abnormalities associated with schizophrenia and manifested differently in the co-twins concordant for schizophrenia seemed to reflect nongenetic, pathological developments of genetically identical brains.

Facial expressions provide an important behavioral measure for the study of emotion, cognitive processes, and social interaction. The Facial Action Coding System (Ekman & Friesen, 1978) is an objective method for quantifying facial movement in terms of component actions. We applied computer image analysis to the problem of automatically detecting facial actions in sequences of images. Three approaches were compared: holistic spatial analysis, explicit measurement of features such as wrinkles, and estimation of motion flow fields. The three methods were combined in a hybrid system that classified six upper facial actions with 91% accuracy. The hybrid system outperformed human nonexperts on this task and performed as well as highly trained experts. An automated system would make facial expression measurement more widely accessible as a research tool in behavioral science and investigations of the neural substrates of emotion.

Choice reaction time (RT) is shorter when the stimulus corresponds spatially to the response than when the stimulus does not, even when the stimulus location is irrelevant to the task. We used electromyographic measures to document that this effect is the result of a response conflict. The activity of the prime movers of two alternative responses was recorded during the performance of a visual RT task in which the irrelevant spatial correspondence between the stimuli and the responses was varied. Only the premotor component of RT was affected by the stimulus–response correspondence. Correct trials were distinguished according to whether or not the activation of the prime mover involved in the required response was preceded by an activation of the prime mover involved in the alternative response. Double muscular activation trials were more numerous for noncorresponding than for corresponding stimulus–response associations. Furthermore, these trials yielded longer RTs than the single muscular activation trials.

Learning to speak a new language requires the formation of recognition patterns for the speech sounds specific to the newly acquired language. The present study demonstrates the dynamic nature of cortical memory representations for phonemes in adults by using the mismatch negativity (MMN) event-related potential. We studied Hungarian and Finnish subjects, dividing the Hungarians into a naive (no knowledge of Finnish) and a fluent (in Finnish) group. We found that the MMN for a contrast between two Finnish phonemes was elicited in the fluent Hungarians but not in the naive Hungarians. This result indicates that the fluent Hungarians developed cortical memory representations for the Finnish phoneme system that enabled them to preattentively categorize phonemes specific to this language.

Using positron emission tomography, visual presentation of sentences was shown to cause increased regional cerebral blood flow relative to word lists in the left lateral anterior superior and middle temporal gyri, attributable to cognitive processes that occur during sentence comprehension in addition to those carried out during word comprehension. Additional comparisons showed that repeating words (in a different context, when subjects did not attempt to learn the initial lists) led to significant patterns of both increased blood flow (left putamen and right caudate) and decreased blood flow (left posterior temporal lobe). Increases are argued to reflect retrieval of memory traces, whereas decreases reflect diminished necessity for processing of input. A decrease in the left inferior parietal lobe was attributable to other factors.

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.

Event-related potentials (ERPs) provide a noninvasive method to evaluate neural activation and cognitive processes in schizophrenia. The pathophysiological significance of these findings would be greatly enhanced if scalp-recorded ERP abnormalities could be related to specific neural circuits and/or regions of the brain. Using quantitative approaches in which scalp-recorded ERP components are correlated with underlying neuroanatomy in schizophrenia, we focused on biophysical and statistical procedures (partial least squares) to relate the auditory P300 component to anatomic measures obtained from quantitative magnetic resonance imaging. These findings are consistent with other evidence that temporal lobe structures contribute to the generation of the scalp-recorded P300 component and that P300 amplitude asymmetry over temporal recording sites on the scalp may reflect anatomic asymmetries in the volume of the superior temporal gyrus in schizophrenia.

Twelve young and 11 elderly men (mean ages 21.1 and 70.1) performed a choice-reaction time (RT) task in which stimulus degradation and stimulus–response (S-R) compatibility were manipulated. The extant literature has suggested that the effects of age on RT are usually augmented (multiplicative) in more difficult task conditions, but also that the effects of age on the latency of the P300 component of the event-related brain potential (ERP) are constant (additive). The results indicated that the effects of age on RT were enhanced in more difficult conditions, whether the difficulty consisted of stimulus degradation or S-R incompatibility. However, the effects of age on P300 latency were enlarged as the stimuli were degraded, but not if the S-R mapping was incompatible. Thus, it appears that task content determines if effects of age on P300 latency are additive or multiplicative. A simple model is proposed that produces the obtained pattern of effects.

The P3 amplitude is augmented by decrements in target-probability, increments in the number of nontargets preceding the target, and extensions of the interstimulus interval (ISI). Each of these changes prolongs the target-to-target interval (TTI) and, consequently, results attributed to these factors might, at least partially, be accounted for by the TTI. Recent research also indicates that the P3s elicited by targets in one-, two-, and three-stimuli tasks (in which the TTI remains invariant) are similar. However, the TTI has not been examined systematically in previous research. The present study had subjects listen to a randomized ISI (0.5, 1, 2, or 4 s) version of the auditory oddball task in which targets occurred after one, two, three, four, or five nontargets. Event-related potentials were analyzed based on ISI, sequential structure, and TTI. The study examined sequence and ISI effects independent of TTI effects and demonstrated that extensions of ISI affected N1 but not P3 amplitude, extensions of TTI enhanced P3 amplitude independent of sequential structure, and sequential structure failed to influence P3 amplitude when TTI was controlled.

What cognitive processes underlie event-related brain potential (ERP) effects related to visual multidimensional selective attention and how are these processes organized? We recorded ERPs when participants attended to one conjunction of color, global shape and local shape and ignored other conjunctions of these attributes in three discriminability conditions. Attending to color and shape produced three ERP effects: frontal selection positivity (FSP), central negativity (N2b), and posterior selection negativity (SN). The results suggested that the processes underlying SN and N2b perform independent within-dimension selections, whereas the process underlying the FSP performs hierarchical between-dimension selections. At posterior electrodes, manipulation of discriminability changed the ERPs to the relevant but not to the irrelevant stimuli, suggesting that the SN does not concern the selection process itself but rather a cognitive process initiated after selection is finished. Other findings suggested that selection of multiple visual attributes occurs in parallel.

In a recent paper, Pritchard, Krieble, and Duke (Psychophysiology, 33, 362–368, 1996) studied the validity of spatial embedding of electroencephalographic (EEG) data and rejected this method in favor of time-delay embedding. The present paper describes the nonlinear characterization of brain dynamics using either spatial or time-delay embedding. We discuss the arguments published in Pritchard et al. (1996) and demonstrate that the spatial embedding cannot be rejected on this basis. We also point out the limitations of both spatial and time-delay embeddings related to the spatial extension and the high-dimensional dynamics of brain activity.

The purpose of the study was to examine the hypothesis that distractibility is a fundamental characteristic of mild closed head injury (MHI). The claim that cognitive symptoms in MHI are due to a mild type of frontotemporal injury was also investigated. Cognitive event-related potentials (ERPs), accuracy and reaction time to target stimuli in a dichotic listening paradigm, and neuropsychological test results were studied in patients with MHI (N = 15), patients with verified frontal lobe damage (N = 10), and healthy controls (N = 13). Information processing reflecting target detection (N2, P3b) and sustained selective attention (processing negativity) was studied. The MHI and frontal patients did not differ on behavioral measures, except that the MHI group had significantly longer reaction times to target stimuli in the ERP task. Both patient groups had deviant ERPs compared with controls, but their ERP patterns differed in important respects. Contrary to expectations, the MHI patients had the most abnormal ERPs. They showed significantly smaller N2 and Nd amplitudes than frontal patients and controls, indicating that the mediating cognitive mechanisms were not equivalent in MHI and frontal injury. The data suggest that MHI patients allocated less processing resources to the task than either the control subjects or the patients with frontal lobe damage.

Careful consideration of the issues raised by Pezard and colleagues (in this issue of Psychophysiology) allows for the conclusion that spatial embedding may be valid as a method of dynamical reconstruction. However, two problems with the technique cannot be ignored. First, spatial embedding of EEG invariably involves linear cross-correlation among channels, which distorts the dynamical reconstruction due to compression toward the main state-space diagonal. Further, before spatially embedding across a set of channels, one must first check for at least “similar” dynamics among them, using, for example, a measure such as estimated mutual dimension. Measuring a “whole cortex” state via spatial embedding may also be possible in principle, except for the nontrivial obstacle of separating local dynamics that are heterogeneous across the cortex from activity reflecting the “unified field” of the cortex as a whole.

The effects of prior task exposure on cardiovascular reactivity to stress were examined in two experiments by randomly assigning participants to repeated exposure groups that performed mental arithmetic pretest and test tasks versus delayed exposure groups that performed only the test task after prolonged rest. Impedance cardiographic and blood pressure measures were recorded continuously from 60 undergraduate men in Experiment 1 and 112 undergraduate men and women in Experiment 2. Task repetition attenuated cardiovascular reactivity and improved task performance in repeated exposure groups (p < .001), suggesting an integrated process of behavioral adaptation. During the test task, delayed exposure groups showed greater cardiac reactivity (p < .01), but not vascular reactivity, than repeated exposure groups. Thus, cardiac reactivity varied as a specific function of prior task exposure, whereas vascular reactivity varied as a general function of time.