A recent positron emission tomography (PET) study on brain mechanisms in classical, or Pavlovian, conditioning is reviewed. The PET data were compared with skin conductance data recorded off-line. The participants were five men who participated in three different experimental phases. In the first (habituation) phase, a tone was repeated 24 times at random intervals. In the second (acquisition) phase, the tone was paired with a brief shock to the wrist. In the third (extinction) phase, the tone was presented alone again. Statistical parametric mapping analysis of the PET data showed significantly increased activation of the right hemisphere in the orbitofrontal cortex, dorsolateral prefrontal cortex, inferior and superior frontal cortices, and inferior and middle temporal cortices. In the left hemisphere, only Area 19 and the superior frontal cortex showed significant activation. The findings are discussed within a theoretical framework that argues for different brain mechanisms in acquisition and extinction in classical conditioning.

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.

The nature and early time course of the initial processing differences between visually matched linguistic and nonlinguistic images were studied with event-related potentials (ERPs). The first effect began at 90 ms when ERPs to written words diverged from other objects, including faces. By 125 ms, ERPs to words and faces were more positive than those to other objects, effects identified with the P150. The amplitude and scalp distribution of P150s to words and faces were similar. The P150 seemed to be elicited selectively by images resembling any well-learned category of visual patterns. We propose that (a) visual perceptual categorization based on long-term experience begins by 125 ms, (b) P150 amplitude varies with the cumulative experience people have discriminating among instances of specific categories of visual objects (e.g., words, faces), and (c) the P150 is a scalp reflection of letterstring and face intracranial ERPs in posterior fusiform gyrus.

We examined performance in young and elderly on an implicit (lexical decision) and an explicit (recognition) memory test. The difference in lexical decision times between old and new words was equivalent in the two groups, although the elderly were slower. In both groups, recognition accuracy (lower in the elderly) was higher following semantic than nonsemantic encoding, whereas lexical decision times were unaffected. Divergent brain potentials for old and new words during lexical decisions constituted a repetition effect, which reflected greater positivity (200–800 ms) for old words, particularly over the left hemisphere; this effect was smaller and later in the elderly. An electrophysiological marker of enhanced recollection for words from the semantic encoding task took the form of a left-sided positivity (500–800 ms). The effect was smaller in the elderly than the young, providing an additional index of their impaired recognition processes.

To examine associations between heart period variability (HPV) and psychopathology in young urban boys at risk for delinquency, a series of 69 7–11-year-old younger brothers of adjudicated delinquents received a standardized psychiatric evaluation and an assessment of heart period variability (HPV). Psychiatric symptoms were rated in two domains: externalizing and internalizing psychopathology. Continuous measures of both externalizing and internalizing psychopathology were associated with reductions in HPV components related to parasympathetic activity. These associations could not be explained by a number of potentially confounding variables, such as age, ethnicity, social class, body size, or family history of hypertension. Although familial hypertension predicted reduced HPV and externalizing psychopathology, associations between externalizing psychopathology and HPV were independent of familial hypertension. Psychiatric symptoms are associated with reduced HPV in young urban boys at risk for delinquency.

A male disadvantage has been reported in several outcome studies of children born preterm. Twenty-two healthy premature children (10 girls, 12 boys) born between 25 and 28 weeks of gestation and 20 controls born full-term (10 boys, 10 girls) were matched on socioeconomical status and age. Event-related potentials (ERPs) were recorded by using 14 electrodes in a visual oddball task, with 75% frequent and 25% rare stimuli. This task elicited a larger P3 to the rare than to the frequent stimuli, with a prominent parietocentral localization. However, the amplitude was larger in full-term boys than in full-term girls, a difference that was not observed between preterm boys and preterm girls, especially to targets and on the central electrodes. In addition, the preterm group was characterized by a frontal slow wave larger in boys than in girls. In these prematures, the lack of the sex-related difference may be accounted by differences in the strength of the neuronal generators in males, as they might have been affected by the high level of androgens by the fetal testis under the control of placental gonadotropes during the first two thirds of gestation.

Recent studies have demonstrated that positive and negative affective reactivity can be predicted by resting electroencephalographic (EEG) asymmetry in frontal brain regions. These studies used different methods to assess asymmetry and affectivity. The goal of the present study was a conceptual replication of these results and to investigate their independence of employed procedures. Resting EEG of 37 subjects was recorded and affective slides were presented to obtain ratings of subjects' emotional reactions. Different procedures were applied to the data to assess the relation between asymmetries and affective reactivity. Depending on the particular analysis procedure, there were associations between anterior asymmetry and affectivity in line with the published findings, opponent to those findings, or no relation between anterior asymmetry and affective reactivity.

To reveal areas in the central nervous system of importance for electrodermal control, regional cerebral blood flow (rCBF) was correlated to nonspecific skin conductance fluctuations (NSF) during aversive and nonaversive conditions. Participants viewed a TV screen displaying white noise or snake videotapes presented both with and without electric shocks given to the right hand. H215O positron emission tomography was used to measure rCBF, and the constant voltage technique was used to measure NSF from the left hand. Electrodermal activity was positively related to rCBF in the left primary motor cortex (MI, Brodmann's Area 4) and bilaterally in the anterior (Areas 24 and 32) and posterior cingulate cortex (Area 23). Negative relations were observed bilaterally in the secondary visual cortex (Areas 18 and 19) and the right inferior parietal cortex (Area 39), with a tendency also for the right insular cortex (Areas 13, 15, and 16). Because results from lesion and stimulation studies in humans converge with the present imaging results, we conclude that the cingulum and the motor cortex, in addition to the parietal and possibly the insular cortex, form part of one or several distributed neural network(s) involved in electrodermal control. Because these areas also support anticipation, affect, and locomotion, electrodermal responses seem to reflect cognitively or emotionally mediated motor preparation.

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.

Secretory immunoglobulin A (sIgA) in saliva and cardiovascular reactions to mental arithmetic and cold pressor tasks were recorded in 16 healthy young men on two sessions, 4 weeks apart. Both tasks elicited significant increases in sIgA secretion rate, reflecting increases in both salivary volume and sIgA concentration. Whereas mental arithmetic elicited a mixed pattern of alpha- and beta-adrenergic cardiovascular reactions, the pattern of reactions to cold pressor was predominantly alpha-adrenergic. Task levels of sIgA secretion rate, sIgA concentration, and saliva volume showed moderate to high test–retest reliability (r = .52–.83), although test-retest correlations were less impressive for change scores (r = −.19–.53). The pattern of correlations between change in sIgA secretion rate and cardiovascular reactivity variables was inconsistent.

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.

Secretory immunoglobulin A (sIgA) in saliva and cardiovascular reactions to mental arithmetic and cold pressor tasks were recorded in 16 healthy young men on two sessions, 4 weeks apart. Both tasks elicited significant increases in sIgA secretion rate, reflecting increases in both salivary volume and sIgA concentration. Whereas mental arithmetic elicited a mixed pattern of alpha- and beta-adrenergic cardiovascular reactions, the pattern of reactions to cold pressor was predominantly alpha-adrenergic. Task levels of sIgA secretion rate, sIgA concentration, and saliva volume showed moderate to high test–retest reliability (r = .52–.83), although test-retest correlations were less impressive for change scores (r = −.19–.53). The pattern of correlations between change in sIgA secretion rate and cardiovascular reactivity variables was inconsistent.

In this study we investigated facial electromyographic (EMG) responses to vocal affect expressions. We also measured emotion-related action tendencies by requesting the subjects to indicate their tendency to approach or withdraw from the person uttering the stimulus word. In addition, emotional contagion (EC) was measured with a questionnaire-based scale. The results showed that hearing the expression of anger increased EMG activity in the subjects' brow region more than hearing contentment. In contrast, the expression of contentment activated the periocular muscle region more than anger. The expressions of anger elicited behavioral withdrawal responses, whereas the neutral expressions and contentment evoked approach responses. Subjects scoring low and high on EC exhibited different patterns of EMG responses. The results support the view that negative and positive affects are contagious from hearing human vocal affect expressions.

Attentional modulation of the startle reflex was studied in 16 unmedicated schizophrenia patients and 15 control individuals during the 18F-2-deoxyglucose uptake period for positron emission tomography. In a task involving attended, ignored, and novel tones that served as prepulses, control individuals showed greater prepulse inhibition (PPI) at 120 ms and greater prepulse facilitation at 4,500 ms during attended than during ignored prepulses; the amount of PPI and facilitation during novel prepulses was intermediate. In contrast, patients failed to show differential PPI at 120 ms and tended to show greater facilitation at 4,500 ms during novel prepulses. For control individuals, greater PPI was associated with higher relative metabolic activity rates in prefrontal (Brodmann Areas 8, 9, and 10 bilaterally) and lower in visual cortex. Patients showed this relationship only for Area 10 on the left. Patients also had low metabolism in superior, middle, and inferior prefrontal cortex. Consistent with animal models, our results demonstrate the importance of the functional integrity of prefrontal cortex to PPI modulation.

Recent studies have demonstrated that positive and negative affective reactivity can be predicted by resting electroencephalographic (EEG) asymmetry in frontal brain regions. These studies used different methods to assess asymmetry and affectivity. The goal of the present study was a conceptual replication of these results and to investigate their independence of employed procedures. Resting EEG of 37 subjects was recorded and affective slides were presented to obtain ratings of subjects' emotional reactions. Different procedures were applied to the data to assess the relation between asymmetries and affective reactivity. Depending on the particular analysis procedure, there were associations between anterior asymmetry and affectivity in line with the published findings, opponent to those findings, or no relation between anterior asymmetry and affective reactivity.

The bandwidth for the recording of the orbicularis oculi blink reflex electromyogram (EMG) response is optimal when low-frequency artifacts, such as motion artifacts and cross-talk from other muscles, are maximally suppressed, whereas true EMG signal power is maximally retained. The optimal bandwidth was investigated for acoustic, electrocutaneous, and photic blink reflexes. Reflexes were recorded with varying bandwidth and interelectrode distances of 12 and 36 mm. Power spectra of the EMG signals were calculated and compared with a theoretical spectrum of the uncontaminated EMG signal. For both electrode distances, the optimal bandwidth was on the average 28–500 Hz for acoustic and electrocutaneous blink reflexes and 12–500 Hz for photic blinks. Using photic stimuli, however, a high-pass filter frequency larger than 12 Hz (probably at least 30 Hz) in combination with occlusion of the eye will be necessary to avoid influences of retinal potentials. Given the optimal bandwidth, a larger electrode spacing may be expected to moderately improve the detectability of small blinks in all stimulus conditions.

There is evidence that frontal lobe function may diminish in normal aging. The P3 component of the event-related brain potential (ERP) elicited by target events in an oddball paradigm becomes more frontally oriented in elderly subjects. It was hypothesized that the extent to which the P3 distribution is frontally oriented in old subjects may index less efficient frontal lobe function. In this study, bootstrapping methods were used to establish the reliability of the locations of maxima of surface brain activity obtained with ERP recordings from young and old subjects. The results indicated that brain activity maxima are reliable for a given individual. However, among the elderly only, there were also clear individual differences in the distribution of the P3 component elicited by target stimuli in an oddball paradigm. On the basis of these differences, the old subjects were divided into two groups. In line with predictions, those elderly subjects who showed frontal-maximal P3 scalp distributions had lower performance on standardized neuropsychological tests of frontal lobe function than those elderly subjects who showed posterior-maximal scalp topographies.

In two experiments, event-related brain potentials were recorded to word pairs simultaneously presented to both ears, with instructions to attend to one ear and detect occasional nonwords in that ear. This attentional manipulation yielded four patterns of word repetition on successive trials: first and second presentations attended (AA), both unattended (UU), and across ears (AU and UA). A prominent attenuation of N400 due to immediate repetition of words was observed on AA trials. However, when first presentations were ignored on UU and UA trials, no repetition effect was obtained. These findings indicate that the repetition effect on N400 depends on attentional processing of first presentations.

Two studies of the relationship between depression and resting frontal electroencephalographic (EEG) activity are reported. Although considerable research supports the theory of left and right hemispheric specialization for approach and withdrawal behaviors, only four studies involving clinically depressed individuals have been published to date. Despite methodological similarities with published research, no significant differences in frontal activation emerged between depressed and nondepressed participants with either college students having high Beck Depression Inventory scores (Study 1) or with individuals diagnosed with DSM-III-R depression (Study 2). Post hoc analyses in Study 2 revealed one effect confined to lateral frontal leads during the first 2 min of EEG data; this finding was significant in only one of three reference montages. Results are discussed in light of methodological considerations and mediating variables such as temperament and coping styles.

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.