Psychophysiology

Event‐related potentials were recorded from 80 participants ranging in age from 7 to 24 years while they attended selectively to stimuli with a specified color (red or blue) in an attempt to detect the occurrence of target stimuli. Color attention effects were identified as frontal selection positivity (FSP; 140–275 ms), selection negativity (SN; 150–300 ms), and N2b (200–450 ms), whereas target detection was reflected in P3b (300–700 ms). There were age‐related decreases in the latencies of FSP, N2b, and P3b that paralleled decreases in reaction time and error rates. Also, the SN amplitude increased with advancing age, whereas both N2b and P3b showed changes in scalp topography. These results represent neurophysiological evidence that the efficiency of visual selective processes increases during childhood and adolescence. Developmental growth may take place at both relatively early and late levels of visual selective information processing.

The occurrence of mental fatigue during tasks like driving a vehicle increases risk of injury or death. Changes in electroencephalographic (EEG) activity associated with mental fatigue has been frequently studied and considered a promising biomarker of mental fatigue. This is despite differences in methodologies and outcomes in prior research. A systematic review with meta‐analyses was conducted to establish the influence of mental fatigue on EEG activity spectral bands, and to determine in which regions fatigue‐related EEG spectral changes are likely to occur. A high‐yield search strategy identified 21 studies meeting inclusion criteria for investigating the change in EEG spectral activity in non‐diseased adults engaged in mentally fatiguing tasks. A medium effect size (using Cohen's g) of 0.68 (95%CI: 0.24–1.13) was found for increase in overall EEG activity following mental fatigue. Further examination of individual EEG spectral bands and regions using network meta‐analyses indicated large increases in theta (g = 1.03; 95%CI: 0.79–1.60) and alpha bands (g = 0.85; 95%CI: 0.47–1.43), with small to moderate changes found in delta and beta bands. Central regions of the scalp showed largest change (g = 0.80; 95%CI: 0.46–1.21). Sub‐group analyses indicated large increases in theta activity in frontal, central and posterior sites (all g > 1), with moderate changes in alpha activity in central and posterior sites. Findings have implications for fatigue monitoring and countermeasures with support for change in theta activity in frontal, central and posterior sites as a robust biomarker of mental fatigue and change in alpha wave activity considered a second line biomarker to account for individual variability.

Interaural time and intensity disparities (ITD and IID) are the two cues to sound lateralization. “Time‐only” hypothesis claims that an IID is first converted to an interaural afferent delay (Δt), and is then processed by the central ITD mechanism, rendering a separate IID processor unnecessary. We tested this hypothesis by assessing the contribution of the cochlear latency effect to the psychophysical ITD/IID trading ratio. Auditory brainstem responses (ABRs) were used to measure the interaural afferent delays (Δts) that developed with a 20/sec dichotic click train used in the trading experiment. Except for small IIDs at low loudness levels, the physiological Δt delay produced by an IID was significantly smaller than the ITD psychophysically traded for the same IID. We concluded that the cochlear latency effect alone cannot explain the psychophysical ITD/IID trading ratios and a separate IID mechanism must be involved.

One difficulty associated with the study of dreams has been the absence of an objective indicator of dreaming in sleep other than REM. This study explores the use of a subjective judgment and instrumental response to mark the occurrence of dreams. Content reports of 8 subjects collected under two conditions were compared. On 2 nights the experimenter determined the time of the awakening and on the other 2 the subject's behavioral response was used as the indicator. The subjects' judgments that they were dreaming proved to be more accurate than was the experimenter's. A single case study of a high NREM responder carried out for 9 nights showed the frequency of NREM dreaming signals to covary with presleep mood.

The aim of the present study was to characterize the functional relationships between behaviorally evoked regional brain activation and cardiac autonomic activity in humans. Concurrent estimates of regional cerebral blood flow (rCBF; obtained by positron emission tomography), heart period, and high‐frequency heart period variability (HF‐HPV; an indicator of cardiac parasympathetic activity) were examined in 93 adults (aged 50–70 years) who performed a series of increasingly difficult working‐memory tasks. Increased task difficulty resulted in decreased heart period (indicating cardioacceleration) and decreased HF‐HPV (indicating decreased cardiac parasympathetic activity). Task‐induced decreases in heart period and HF‐HPV were associated with concurrent increases and decreases in rCBF to cortical and subcortical brain regions that are speculated to regulate cardiac autonomic activity during behavioral processes: the medial‐prefrontal, insular, and anterior cingulate cortices, the amygdala–hippocampal complex, and the cerebellum. These findings replicate and extend a small number of functional neuroimaging studies that suggest an important role for both cortical and subcortical brain systems in human cardiac autonomic regulation.

The polyvagal theory states that social behavior is linked to cardiac vagal control. This theory has been tested widely in infants and children, but less so in adults. Thus, we examined if resting or stress‐related changes in high‐frequency heart rate variability (HF‐HRV; a presumed index of vagal control) varied with social functioning in 50 healthy women (mean age 68 years). After completing assessments of social functioning, women were exposed to laboratory stressors with concurrent psychophysiological monitoring. Although stressor‐induced suppression of HF‐HRV was common, women with less stressor‐induced suppression of HF‐HRV reported more positive social functioning. Resting HF‐HRV was not related to social functioning. These findings are at apparent odds with the polyvagal theory; however, they complement prior work suggesting that emotional self‐regulation could plausibly modulate cardiac vagal control in association with social functioning.

The characteristics of mismatch negativity (MMN) elicited by dichotic stimulation were examined using frequency‐deviant stimuli presented to the right, to the left, or to both sides. The experiment was run twice, once using earphones and once using loudspeakers in free field. With both modes of stimulation, deviants presented in the left, right, or both ears, or tones that were switched between ears, elicited comparable MMNs, with a peak latency of about 180 ms. With earphones, the amplitude of the MMN was bigger at the frontal‐lateral right hemisphere sites than at the homologous left‐hemisphere sites for all deviance conditions. Scalp current density analysis revealed that deviance in the right side elicited bilaterally equivalent frontal current sinks and a trend towards stronger contralateral current sources at the mastoid sites. In contrast, left side deviance elicited frontal sinks and temporal current sources stronger over the right hemiscalp. These results are compatible with the multiple‐generator model of MMN. The attention‐related role of the MMN is discussed, suggesting comparable attention mechanisms for vision and audition.

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.

Despite publication of many well‐argued critiques of null hypothesis testing (NHT). behavioral science researchers continue to rely heavily on this set of practices. Although we agree with most critics' catalogs of NHT's flaws, this article also takes the unusual stance of identifying virtues that may explain why NHT continues to he so extensively used. These virtues include providing results in the form of a dichotomous (yes/no) hypothesis evaluation and providing an index (p value) Mini has a justifiable mapping onto confidence in repeatability of a null hypothesis rejection. The most‐criticized flaws of NHT can be avoided when the importance of a hypothesis, rather than the p value of its test, is used to determine that a finding is worthy of report, and when p=.05 is treated as insufficient basis for confidence in the replicability of an isolated non‐null finding. Together with many recent critics of NHT, we also urge reporting of important hypothesis tests in enough descriptive detail to permit secondary uses such as meta‐analysis.

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.