Many of the social, economic, and political problems facing people with schizophrenia are due to a misconception in the community that schizophrenia is not a biologically based disease but a myth. Because the diagnosis is based on self-reported symptoms, it is difficult for many people to acknowledge that schizophrenia is real. One goal of psychophysiological research has been to anchor both diagnosis and symptoms in biological reality. Reduction of the amplitude of the P300 component of the event-related potential (ERP) is the most replicable biological marker of the disease. Data are presented suggesting that P300 is both a state and a trait marker of the disease and may be sensitive to the progressive/degenerative course of the disease. Although the P300 tracks changes in clinical symptoms, it remains reduced even in patients in relative remission. P300 amplitude reduction is related to enduring negative symptoms, waning of attention, and gray matter volume deficits. ERP components other than P300 can also manifest the biological reality of various symptoms of the disease.

For almost two decades, researchers have demonstrated that hypertension is reliably associated with decreased perception of pain. More recently, a growing body of evidence has begun to suggest that hypoalgesia is not a consequence of high blood pressure, as the phenomenon precedes the onset of hypertension in individuals at risk for the disorder. This article provides a review of empirical evidence of decreased pain perception in normotensive persons with a family history of hypertension, elevated resting blood pressure, or exaggerated cardiovascular reactivity to stress. Based on the existing evidence, hypoalgesia is argued to be a correlate of dysregulation of central nervous system structures involved in both pain control and cardiovascular regulation in individuals who are genetically predisposed to develop high blood pressure. As such, hypoalgesia may serve as a valuable method of identifying individuals at greatest risk for hypertension.

In this study, we explored the effects of flash intensity and age on visual-evoked potentials (VEPs) in a sample of 85 children aged 8–15 years. Results of previous studies are discrepant regarding the extent to which children show an evoked potential augmenting tendency at vertex, which has been reported to be a characteristic of an immature inhibitory control system. In the present study, VEPs to light flashes of four different intensities were recorded at Cz. The results confirmed that P1N1 and N1P2 at Cz were positively related to increases in stimulus intensity, whereas N1 was not related reliably to intensity. This difference between peak–peak and baseline–peak amplitude findings at Cz relative to evoked potential augmenting and reducing may help to explain discrepant results among earlier studies. Developmental changes were found for our sample of children that were independent of stimulus intensity: N1 amplitude increased significantly with age, whereas N1 latency showed a small (nonsignificant) age-related decrease.

Two experiments examined the effects of visually presented threat and nonthreat word lead stimuli on blink modification among unselected young adults (Experiment 1, N = 35) and participants selected for low and high trait anxiety (Experiment 2, N = 60). The blink reflex was elicited by a white noise probe of 105 dB. Lead stimulus intervals of 60, 120, 240, and 2000 ms were used in both experiments. Prepulse inhibition was observed at the 240-ms interval and prepulse facilitation was observed at the 60-ms interval in both experiments. Also, greater facilitation was found in both experiments during threat words at the 60-ms interval and greater inhibition during threat words at the 240-ms interval. Experiment 2 provided some evidence that the greater facilitation during threat words than during nonthreat words at the 60-ms probe interval may be found in high trait anxious participants, but not in low trait anxious participants. The results are discussed in relation to contemporary information processing theories of anxiety.

Rhythmic properties of spoken language such as metrical stress, that is, the alternation of strong and weak syllables, are important in speech recognition of stress-timed languages such as Dutch and English. Nineteen subjects listened passively to or discriminated actively between sequences of bisyllabic Dutch words, which started with either a weak or a strong syllable. Weak-initial words, which constitute 12% of the Dutch lexicon, evoked more negativity than strong-initial words in the interval between P2 and N400 components of the auditory event-related potential. This negativity was denoted as N325. The N325 was larger during stress discrimination than during passive listening. N325 was also larger when a weak-initial word followed a sequence of strong-initial words than when it followed words with the same stress pattern. The latter difference was larger for listeners who performed well on stress discrimination. It was concluded that the N325 is probably a manifestation of the extraction of metrical stress from the acoustic signal and its transformation into task requirements.

The temporal and hierarchical relationships between the dorsal and the ventral streams in selective attention are known only in relation to the use of spatial location as the attentional cue mediated by the dorsal stream. To improve this state of affairs, event-related brain potentials were recorded while subjects attended simultaneously to motion direction (mediated by the dorsal stream) and to a property mediated by the ventral stream (color or shape). At about the same time, a selection positivity (SP) started for attention mediated by both streams. However, the SP for color and shape peaked about 60 ms later than motion SP. Subsequently, a selection negativity (SN) followed by a late positive component (LPC) were found simultaneously for attention mediated by both streams. A hierarchical relationship between the two streams was not observed, but neither SN nor LPC for one property was completely insensitive to the values of the other property.

Detecting deviant, and potentially meaningful, auditory events depends on transient representations of preceding stimuli. Here, we examined whether the neural circuitry underlying deviance detection system varied as a function of deviance type. In different blocks of trials, participants were presented with a sequence that included standard and deviant tones differing in frequency or a sequence of tones that alternated regularly in frequency with occasional deviant repetitions. Both frequency- and pattern-deviant stimuli elicited a mismatch negativity (MMN) peaking between 120 and 175 ms poststimulus. The MMN amplitude distribution was more frontal for frequency-deviant than for pattern-deviant stimuli. There are two possible explanations for these results. Both frequency- and pattern-deviation MMNs might arise in the same set of generators whose relative strength of activation varies. Alternatively, frequency- and pattern-deviation MMNs could originate in different generators. These alternatives were investigated using principal component analysis and signal identification methods. These methods revealed that no common signal space could account for both of the MMNs, indicating different generator sources for the analysis of frequency and pattern deviance. The results suggest separate memory-related processing for auditory frequency and patterns and indicate that the neural circuit of deviance detection varies as a function of the perceptual context.

The capacity of working memory has been suggested to differ among people and these differences affect performance in a wide variety of cognitive tasks. This study explored electrophysiological correlates of individual differences in working memory capacity by means of event-related potentials. Thirty-four healthy students performed two- and five-choice reaction time tasks. In the two-choice reaction time (2CRT) task, two digits (3 and 7) were presented visually with probabilities of .20 and .80. In the five-choice reaction time (5CRT) task, five digits (3, 4, 5, 6, and 7) were presented equiprobably in a random order. Participants were required to press a button corresponding to each digit with a different finger. Working memory capacity of each participant was assessed by the reading span test originated by M. Daneman and P.A. Carpenter (1980). Participants with high reading span produced larger P300s than did persons with low reading span in the 5CRT task, but the difference was not significant in the 2CRT task. It had been suggested that individual differences in working memory capacity would affect initial stages of information processing as early as 300 ms after stimulus onset.

The effect of level of muscle tension on the perception of painful stimuli was assessed in 13 chronic back pain patients, 14 subjects at high risk for chronic back pain, and 14 matched healthy controls. Subjects received painful intracutaneous electric stimuli to the forearm or the lower back while they produced either high or low muscle tension levels. Visual analog scale (VAS) ratings of acute pain were obtained after each trial. Electroencephalograms, electromyograms, skin conductance levels, and blood pressure were measured during the trials. Although subjective pain ratings were not significantly affected by muscle tension levels, the chronic pain patients displayed elevated N150 and N150/P260 amplitudes of the somatosensory-evoked potentials in the low as compared to the high muscle tension condition. The high risk group showed a trend toward higher N150 amplitudes in the low as compared to the high tension condition. The results of this study partially support the hypothesis that increases in muscle tension might serve as a pain-reducing mechanism in chronic pain patients and those at risk for chronicity, thus leading to a vicious pain-tension cycle.

We tested the hypothesis that psychopathy is associated with abnormal processing of semantic and affective verbal information. In Task 1, a lexical decision task, and in Task 2, a word identification task, participants responded faster to concrete than to abstract words. In Task 2, psychopaths made more errors identifying abstract words than concrete words. In Task 3, a word identification task, participants responded faster to positive than to negative words. In all three tasks, nonpsychopaths showed the expected event-related potential (ERP) differentiation between word stimuli, whereas psychopaths did not. In each task, the ERPs of the psychopaths included a large centrofrontal negative-going wave (N350); this wave was absent or very small in the nonpsychopaths. The interpretation and significance of these differences are discussed.

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.

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.

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.

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.

A. R. Haig, E. Gordon, and S. Hook (1997) disputed G. McCarthy and C. C. Wood's (1985) contention that scaling should be used when assessing the statistical significance of between condition (or group) differences in the shapes of event-related potential (ERP) scalp topographies. Haig et al. based their contention upon the lack of empirical realism in McCarthy and Wood's model of within-group ERP noise, claiming that McCarthy and Wood's results could not be generalized to realistic ERP data. We argue, on both empirical and theoretical grounds, that Haig et al. do not make a compelling case against generalization of McCarthy and Wood's results. Moreover, Haig et al.'s conclusion is based upon a misconception of how scaling should be used. We conclude that when a quantitative measure of differences between topographic shapes is needed, scaling is not an option—it is a requirement.

Event-related potentials (ERPs) were recorded during a go/no-go reaction time (RT) task in which subjects responded to rare target tones and withheld response to frequent tones. In a predictable condition, a rare visual stimulus signalled the impending occurrence of a rare tone, whereas a frequent visual stimulus signalled that a frequent tone would be presented. The rare visual stimuli elicited P3, associated with violations of expectations, whereas the rare tones, being predictable, did not. The rare tones elicited the mismatch negativity (MMN), a component associated with preattentive deviance detection, despite the fact that they were expected. RT was faster in the predictable condition than in another condition in which the tones were not predictable. The P3 and RT data indicate, respectively, that subjects anticipated and were ready to respond to the target tones. The MMN result indicates that immediately before target tones, the preattentive system underlying the MMN was set for frequent tones, being unaffected by the information available to the higher order system. Thus, the higher order cognitive system associated with P3 and the lower order cognitive system associated with the MMN were prepared simultaneously for opposite events.