This paper reports analysis of data from a previous study examining cardiovascular effects of rhythmical skeletal muscle tension (RSMT) at 0.1Hz. Our analysis examined whether 0.1Hz RSMT stimulates resonance properties of the cardiovascular system provided by baroreflex (BR) activity. Thirty-seven study participants tensed their large skeletal muscles, with and without crossing their legs, for 3-min periods at a rate of six tension/relaxation cycles/min. Tensing periods were preceded and followed by 3-min rest periods. RSMT elicited high-amplitude 0.1Hz oscillations in the cardiovascular system. We found increases in spectral power of ECG R-R interbeat interval (RRI), systolic blood pressure (SBP) and pulse transit time (PTT) at this frequency. The increases in SBP and PTT oscillations were greater than those in RRI. Only in SBP and PTT did total variability (standard deviation) increase. The phase angle between RRI and SBP oscillations was approximately 45 degrees . Although alpha low-frequency baroreflex gain was attenuated by RSMT, it was not significantly changed at 0.1Hz, consistent with BR-induced resonance effects. Our results are consistent with previous observations that 0.1Hz RSMT is effective in treating vasovagal reactions and indicate that the pathway is through resonance characteristics of the BR system. Implications for resonance applications for resonance in the sympathetically mediated vascular tone baroreflex closed loop are discussed.
In the past, Kleitman's notion of a basic rest-activity cycle (BRAC), which states an approximate 1.5-h rhythm of arousal, has received some empirical support in studies investigating physiological or psychological parameters. Our study investigated this ultradian rhythm in human cognitive performance. Sixty subjects were tested every 10 min for 9 h with an elementary cognitive task, the sentence-verification test (SVT), and provided ratings of alertness and mood. Heart period was always measured during performance of the SVT. Using rather conservative statistical methods, spectral analyses of time series revealed no significant 90-min periodicity for any of the variables. Instead, longer periodicities were the major sources of variance. Reanalyses using detrended and/or smoothed time series suggest that emergence of the BRAC might depend also on statistical methods. In conformity with recent studies it was concluded that several positive reports for the BRAC might be due to lack of conservatism in statistical methods.
This paper describes the methods used to acquire and reduce a massive amount of EEG data (Wylie et al., 1990). The description is introduced by a review of a previous effort (Mackie and Miller, 1978). The earlier effort created much of the design philosophy for the second effort. The majority of data in the Paradox database came from 400 trips contributed by 80 commercial drivers driving both day and night revenue-cargo runs of 10 or 13 h each. The sleep and driving EEG data were collected with ambulatory Medilog recorders. Breathing and oxyhemoglobin measures were collected during sleep for sleep-apnea determinations. The sleep and driving-EEG data were placed in raw digitized files (128 samples/second), with the latter also available as compressed-band arrays for 20-s epochs, with associated Rechtschaffen and Kales (1968) manual scoring by polysomnographers for all EEG data. Sleep EEG, subjective driving performance and discrete-task data were also placed in the database, integrated and time-registered to within 1-s accuracy with the driving EEG data. Each truck was extensively instrumented for lateral lane position, steering wheel position, speed, video image of the roadway, and video image of the face. Each driver recorded body temperatures several times per day, provided Stanford Sleepiness Scale readings several times each day, and was connected to the Vagal Tone Monitor while driving. In addition, driving segments were prefaced and followed by the performance of the Critical Tracking Task, the Psychomotor Vigilance Task, and the Code Substitution Task. The database should serve as an international resource from which many investigators may draw data.
Due to the Great East Japan Earthquake on 11 March 2011 and the following long-term earthquake swarm, many people living in the earthquake-affected areas have developed mental stress, even though clinically-diagnosable symptoms may not be apparent. Concurrently, many unusual reports have emerged in which persons complain of abnormally increased sensitivity to sudden ambient sounds during their daily lives (e.g., the sound of the washing machine on spin cycle). By recording event-related potentials to various sudden ambient sounds from young adults living in the affected areas, we found that the level of earthquake-induced mental stress, as indexed by the hyperarousal symptoms of posttraumatic stress disorder, was positively related to the magnitude of P3a to sudden ambient sounds. These results reveal a strong relationship between mental stress and enhanced involuntary attentional orienting in a large majority of trauma-exposed people without diagnosable symptoms.
The study of aversive Pavlovian conditioning in children can contribute to our understanding of how fears are acquired and extinguished during development. However, methodological issues hamper further research because of ethical and procedural concerns regarding the use of traditional aversive unconditional stimuli (USs) and no established method to measure trial-by-trial changes in the child's expectancy of the US. The present experiment used geometric shape conditional stimuli (CSs) and an unpleasant sound US with 8- to 11-year-old children. Reliable acquisition and extinction were observed with first, second, and third interval skin conductance responses, on-line expectancy judgments, and post-conditioning subjective ratings of pleasantness and arousal. The experiment confirms the novel use of an unpleasant sound of metal scraping on slate as a US in aversive conditioning with children. The methods have the potential to facilitate the ethical conduct of aversive conditioning research in children using psychophysiological, affective, and self-report expectancy measures.
Electrophysiological measures may be useful markers of the genetic underpinnings of complex behavior and psychopathology. Twin and family studies have been used to estimate the genetic contribution to the individual differences in a variety of electrophysiological measures. These studies are briefly reviewed here and published twin correlations from a number of studies with comparable methodology were selected for structural equation meta-analyses. For electroencephalographic (EEG) alpha power (11 twin groups) the heritability estimates in each of the single studies were high (averaged 79%), but it was not possible to equate the twin correlations across studies in the meta-analysis. In contrast, combining the data on alpha peak frequency (five twin groups) revealed a 'meta'-heritability of 81% (95% CI: 76-84%). Aggregating the twin correlations of five twin studies on the P300, the estimated meta-heritability is 60% (95% CI: 54-65%) for P300 amplitude and 51% (95% CI: 43-58%) for P300 latency. It is concluded that genomic variation contributes significantly to individual differences in all EEG and event related potential (ERP) measures studied to date.
Evidence suggests that individuals who are more obese may be more responsive to stress. Stress activates the sympathetic nervous system (SNS) and the adipose-tissue cytokine leptin stimulates SNS activity in animals. We examined the relationship between adiposity, leptin and physiological responses to acute laboratory stress in 67 women. We predicted that individuals with greater adiposity and/or higher plasma leptin would be more stress-responsive. Adiposity was unrelated to cardiovascular or neuroendocrine stress reactivity. However, women with larger waists had greater stress-induced increases in plasma leptin and interleukin-1 receptor antagonist (IL-1Ra). Similarly, women with higher basal leptin displayed greater stress-induced increases in heart rate and plasma interleukin-6, and larger decreases in heart rate variability and cardiac pre-ejection period. Heightened cardiovascular and inflammatory stress responses are predictive of future cardiovascular risk. Our findings suggest that the cytokines leptin and IL-1Ra may play a role in the association between obesity, stress and cardiovascular health.
Individuals with social phobia display neural hyperactivation towards angry facial expressions. However, it is uncertain whether they also show abnormal brain responses when processing angry voices. In an event-related functional magnetic resonance imaging study, we investigated brain responses to neutral and angry voices in 12 healthy control participants and 12 individuals with social phobia when emotional prosody was either task-relevant or task-irrelevant. Regardless of task, both phobic and non-phobic participants recruited a network comprising frontotemporal regions, the amygdala, the insula, and the striatum, when listening to angry compared to neutral prosody. Across participants, increased activation in orbitofrontal cortex during task-relevant as compared to task-irrelevant emotional prosody processing was found. Compared to healthy controls, individuals with social phobia displayed significantly stronger orbitofrontal activation in response to angry versus neutral voices under both task conditions. These results suggest a disorder-associated increased involvement of the orbitofrontal cortex in response to threatening voices in social phobia.
This study investigated cortical/cognitive relations in 30 4th, 8th and 12th grade students. All students were administered the Figural Intersection Test, a measure of cognitive development, and performed, three times with different targets, an event-related potential (ERP) oddball/selective-attention task. Two independent factors emerged from the ERP task that predicted development--speed of processing (P300 latency to Block 1 targets) and maturation of executive functioning (a composite ERP variable calculated as the ratio of RT and P300 latency divided by the accuracy to Block 2 targets). These two variables loaded on orthogonal factors in a principal components analysis, and were the only variables included in a stepwise regression of physiological variables on cognitive development. Speed of processing is modulated by myelination and synaptogenesis, and executive functioning is modulated by maturation of the frontal system. These electrophysiological markers could index these cortical transformations underlying cognitive development.
Neurobiological studies have demonstrated that psychotherapy is able to alter brain function in adults, however little exists on this topic with respect to children. This waiting-list controlled investigation focused on therapy-related changes of the P300 and the late positive potential (LPP) in 8- to 13-year-old spider phobic girls. Thirty-two patients were presented with phobia-relevant, generally disgust-inducing, fear-inducing, and affectively neutral pictures while an electroencephalogram was recorded. Participants received one session of up to 4h of cognitive-behavioral exposure therapy. Treated children showed enhanced amplitudes of the LPP at frontal sites in response to spider pictures. This result is interpreted to reflect an improvement in controlled attentional engagement and is in line with already existing data for adult females. Moreover, the girls showed a therapy-specific reduction in overall disgust proneness, as well as in experienced arousal and disgust when viewing disgust pictures. Thus, exposure therapy seems to have broad effects in children.
Although the etiology of clinical depression is unknown, women are more likely to suffer from major depressive disorder than men. In addition, in some women, there is a clear association between depression and specific phases of the menstrual cycle. Surprisingly little research has examined gender differences and the influences of the estrous cycle in this and other animal behavioral models of clinical depression. Learned helplessness is a valid animal model of stress-induced behavioral depression in which prior exposure to inescapable stress produces deficits in escape testing. Learned helplessness was studied in rats using an inescapable tail shock stress followed by a shuttle box test to determine escape latencies. Animals with mean escape latencies of >or=20 s after shuttle-box testing are defined as learned helpless. Males and normal cycling female rats in the estrus and diestrus II phases were studied. Female rats in the diestrus II phase had significantly higher escape latencies and exhibited a more helpless behavior than female rats in the estrus phase. Male rat escape latencies were intermediate between the two female phases. These results suggest a role for gonadal hormones in the development of stress-induced behavioral depression or 'learned helplessness.'
The purpose of the current study is to examine the moderating influence of the catechol O methyltransferase gene (COMT) on the maternal prenatal smoking/offspring externalizing disorder relationship. The sample consisted of 430 young adults born between 1981 and 1984 at the Mater Misericordiae Mother's Hospital in Brisbane, Australia, as well as their mothers and peers. Mothers reported their prenatal smoking status during pregnancy, and genetic data was obtained from the youth at a later follow-up in adulthood. The outcome measures in this study were mother and teacher reports of youth attention problems and aggression at age 15, and youth, mother and peer reports of youth attention problems and aggression at age 20 (combined to create latent factors of attention problems and aggression at each age). The COMT Val108/158Met polymorphism (rs4680) significantly interacted with maternal cigarette smoking during pregnancy to predict youth aggressive behavior at ages 15 and 20. This gene-environment interaction was not significant for youth attention problems.
There is growing evidence for neuropsychological dysfunction in obsessive-compulsive disorder (OCD) related to an underlying frontal lobe and/or basal ganglia dysfunction. The following paper is a systematical review of the existing literature on cognitive impairment in OCD patients. Fifty studies were surveyed with regard to methodological aspects and cognitive impairments found in OCD patients. In addition, the impact of confounding variables such as psychotropic medication, co-morbidity or severity of symptoms on neuropsychological functioning as well as effects of treatment are discussed. OCD is often related to memory dysfunction that seems to be associated with impaired organization of information at the stage of encoding. Several other executive functions are also commonly disturbed, though results are inconsistent. The results of our study suggest that some cognitive deficits seem to be common in OCD, but future studies should focus more on possible confounding variables such as co-morbidity or psychotropic medication.
One of the earliest recorded works in Biological Psychology was published in 1910 by Argentine psychiatrist José Ingenieros (1877-1925), Professor of Experimental Psychology at the Faculty of Philosophy and Letters of the University of Buenos Aires. Ingenieros, a multifaceted personality and prolific author and educator famous for his lapidary aphorisms, has been considered a 'luminary' for generations. Trained as a physician, he was the first scientist to establish a comprehensive psychological system in Latin America. His long list of publications includes more than 300 titles generally divided in two periods: studies in mental pathology and criminology (1897-1908) and studies in philosophy, psychology and sociology (1908-1925). His works were never made particularly available to English-speaking audiences, despite the fact that certain of his books are still best-sellers in the Spanish-speaking world. We present an overview of Ingenieros' life and work, and a detailed account of his profoundly interesting work Principios de Psicología Biológica, in which he analyzes the development, evolution and social context of mental functions. We also provide an English translation of the Introduction contributed by Nobel laureate Wilhelm Ostwald (1853-1932) to the 1922 German edition of the work, pertinent to the energetic principles Ingenieros used and the study of Psychology as a natural science. It is a hope, 80 years after Ingenieros' parting, to bibliographically resurrect this champion of reason, who, until now, has not been given his due placement in the international psychological and biomedical literature.
Donchin, Tueting, Ritter, Kutas and Heffley (1975) present evidence from a principal components analysis (PCA) that the CNV and P300 are independent. This short critique points out a number of erros in their PCA and presents a reworking of their analysis. A number of further aspects of Donchin et al.'s paper are also discussed. The general value of this contribution in drawing the attention of EP researchers to potential sources of error in the application of factor analysis is emphasized.
O'Connor and Shaw (1978) investigated the relationship between field-dependence-independence (taken as a measure of cognitive organization), handedness strength (taken as a measure of functional organization), and resting EEG coherence spectra in the alpha band (taken as a measure of cortical organization). All three variables were found to be significantly interrelated in the right-handed as well as the left-handed subsample. However, some inconsistencies in the original report suggested the need for reanalysis of the data. The results of that reanalysis are presented here. When a mean unsigned error was used as score for the Rod and Frame Test, more field-independent subjects consistently showed lower EEG coherence spectra than more field-dependent subjects. Also, both right-handed and left-handed field-independent individuals tended to show a stronger degree of handedness in the direction of their lateral preference than field-dependent subjects, indicating that a more field-independent approach is associated with greater specialization irrespective of the direction of lateral preference.
Kok (1986) investigated why P3 amplitudes are reduced when stimuli are degraded. He proposed that a positive moment-related component might overlap P3 after intact stimuli and a negative one after degraded stimuli ("MRP overlap" hypothesis). Discussing his findings, it is suggested that MRP overlap can only account for the result if another overlap hypothesis ("nogo overlap") is added. But even this combined hypothesis cannot explain reducing effects of degradation found in other paradigms. While other overlap hypotheses have been proposed in the literature, the most parsimonious hypothesis is to assume that P3 itself gets smaller after degraded stimuli.
Two apparently new effects in human cardiac responding, "primary bradycardia" and "vagal inhibition", were first described by the Laceys. These effects have been considered by some researchers to reflect differential cardiac innervation, analogous to similar effects observed in animal preparations with direct vagal stimulation. However, it has been argued that such effects arise merely from the data-analytic techniques introduced by the Laceys, and hence are not genuine cardiac cycle effects. Jennings, van der Molen, Somsen and Ridderinkhoff (Psychophysiology, 28 (1991) 596-606) recently proposed a plotting technique and statistical procedure in an attempt to resolve this issue. The present paper demonstrates that the plotting technique fails to achieve their stated aim, since it identifies data from identical cardiac responses as showing cardiac-cycle effects. In addition, the statistical procedure is shown to be reducible to a trivial test of response occurrence. The implication of these demonstrations, in the context of other work, is that this area of investigation has reached a dead end.
The research reported here was derived from the hypothesis that hyperventilation contributes to the decrement in performance observed in test-anxious students. From this point of view, students identified as test-anxious would be expected to hyperventilate to a greater extent than non-test-anxious students when confronted with the stress of testing. The experiment reported here tested this hypothesis by continuous capnographic monitoring of end-tidal CO2 and respiration frequency of 16 high- and 16 low-test-anxious boys and girls (ages 12-14 years) before and during tests of math and word-recall memory under conditions of high- and low-stress (i.e. 'strong' motivational instruction versus 'weak' motivational instructions). Consistent with predictions, high test-anxious students displayed lower levels of end-tidal CO2 (under the high-stress condition) and faster respiration frequencies than low test-anxious students. Both high- and low-test-anxious students scored higher on the math test under high-stress conditions, but differences between recall scores were not significant. Collateral data revealed a positive relationship between scores on the Nijmegen Hyperventilation Questionnaire and the Revised Suinn Test Anxiety Behavior Scale, and a negative relationship between the questionnaire scores (self reports of frequency of symptoms of hypocapnia) and drop in level of end-tidal CO2 during testing, i.e. high-test-anxiety group reported a greater frequency of symptoms of hyperventilation and a larger drop in level of end-tidal CO2 during testing than low-test-anxiety group.
Fowler et al. (Fowler, B., Hofer, K., Lipitkas, J., 2000. The exhaustive additivity displayed by nitrous oxide has implications for cognitive-energetical theory. Biol. Psychol. 52, 161-180) observed that nitrous oxide (N(2)O, an inhalation anaesthetic) does not interact with experimental manipulations derived from the additive factors literature. They proposed a two-tiered cognitive-energetical model to account for the apparent "exhaustive additivity". This model assumes that N(2)O affects a lower tier resulting in a non-selective effect on an upper tier, which is comprised of energetical mechanisms that are selectively linked to processing stages. In this commentary, it is argued that the "exhaustive additivity" can easily be accomodated by linear stage models. The findings of Fowler et al. suggest a new stage rather than a new model. Moreover, their new model seems to predict "exhaustive interaction" rather than "exhaustive additivity". It is concluded that Fowler et al. may have a highly interesting finding, but not for the reasons they submitted when accounting for the "exhaustive additivity" displayed by N(2)O.
Herbert and colleagues (2012) state that changes in autonomic activity following a specific type of interoceptive sensation, intensifies general interoceptive awareness. This conclusion is being critically examined and reformulated. A distinction is made between Interoceptive Awareness (IAw) and Interoceptive Accuracy (IAc); awareness not necessarily implying accuracy. Given the heterogeneity of interoceptive sensations, we question whether heartbeat perception tasks can be considered as a measure of overall IAw or overall IAc. Results are reinterpreted to indicate that homeostatic challenges which lead to an increase in inotropic cardiac activity, lead to an increased Accuracy of heartbeat perception, and perhaps increased Awareness of heartbeats. However, the findings do not provide conclusive evidence that such challenges increase other types of IAc, nor that they increase overall IAw. Furthermore, it remains unclear whether homeostatic challenges leading to a decrease in inotropic cardiac activity, lead to changes in accuracy of heartbeat perception.
Epileptic populations are generally considered inappropriate to investigate hemispheric specialization. However, (1) because hallucination occurs in the early stage of the ictus during which activation is observed in and around the focus, the former could be a direct result of the latter (hypothesis 1), and (2) the type of psychological content of ictal hallucination could depend on which hemisphere is ictally activated (hypothesis 2). It was predicted that, on the basis of quantitative analysis of previously published singles case reports, unilateral ictal hallucinations should occur in the visual field, ear or hemibody contralateral to the side of the ictal focus (test of hypothesis 1). It was also predicted that verbal ictal auditory hallucinations should result more often from left hemisphere foci, and non-verbal auditory ictal hallucinations from right hemisphere foci (test of hypothesis 2). Previously published cases (N=217) of ictal hallucination from a unilateral epileptic focus were reviewed and analyzed with multivariate statistics. Both predictions were strongly supported.
Evoked potentials were recorded at four scalp sites O1, O2, T5, T6; before and after the consumption of one of two alcohol dose levels, to the occurrence of disparate stimuli in dynamic random dot stereograms. Twenty young adult subjects, all of whom had vision which was normal or corrected to normal, were randomly assigned to the two dosage groups. Subjects viewed stimuli which embodied crossed disparity and followed one of three trajectories in depth. The task was to distinguish between and identify, by specific button presses, these trajectories. One half of the stimuli were presented with monocular cues to motion in depth (dark condition); in the remainder only stereoscopic depth information was available (uniform condition). Responses to both conditions showed alcohol-related reduction of evoked responses across all sites. It was concluded that the visual systems associated with the processing of motion in depth were susceptible to alcohol effects, as revealed by reductions in the amplitude of evoked responses.
Individuals differ in the cardiac and vascular processes that underlie blood pressure elevations evoked by environmental stimuli; such differences may reflect variability in sympathoadrenal response. We separated 108 healthy, young-adult males into those with predominant elevations in either cardiac output or peripheral resistance when exposed to psychological challenges. We then asked if they differed on other measures of cardiovascular response, concomitant plasma catecholamine reactions or 24-h urinary excretion of catecholamines. Cardiac reactors, relative to vascular reactors, showed reduced cardiac pre-ejection period, a smaller reduction in stroke volume, and elevated plasma epinephrine response and 24-h urinary epinephrine excretion. Vascular reactors, relative to cardiac reactors, responded to mental stress with more elevated diastolic blood pressure, a rise in peripheral resistance and pulse wave velocity, and a greater reduction in stroke volume. Vascular reactors, however, did not show plasma norepinephrine response or 24-h urinary norepinephrine excretion that was greater than cardiac reactors. The results provide partial support for the hypothesis that variability in sympathoadrenal activity contributes to individual differences in cardiac and vascular reactivity, and extend prior observations by demonstrating covariation of behaviorally-elicited cardiac reactivity with the 24-h excretion of epinephrine.
Heart period variability (HPV) measured from 24 h ECG recordings predicts mortality following myocardial infarction and may be a measure of cardiovascular health in the general population. Since epidemiologic evaluation of healthy people will require alternatives less intensive than 24 h recording, we investigated the relationship between HPV derived from 24 h and 5 min recordings, using two approaches for obtaining RR intervals. Template-matching (TM) algorithms were applied to 24 h ECG recordings from 41 normal subjects (mean age 35.7 +/- 13 years). Five min of ECG data during this 24 h period also were collected by an on-line microcomputer-based system for peak detection (PD) analysis. Intraclass correlations comparing the TM and PD approaches on the 5 min period were .80 or greater for all measures of HPV. Pearson correlation coefficients between the 5 min (TM) estimates and 24 h data and 5 min (PD) estimates and 24 h data exceeded .60 and .55, respectively, for all but one variable, with all p values < .05. Thus, in healthy adults, TM and PD approaches to HPV estimation from short segments of ECG data are highly consistent and the correlations between HPV obtained from brief intervals and 24 h measures were substantial, suggesting that assessment of HPV as a screening measure of cardiac autonomic control in healthy adults may be feasible.
People with medically unexplained symptoms (MUS) often have a comorbid history of stress and negative affect. Although the verbal-cognitive and (peripheral) physiological stress systems have shown a great degree of independence, at the same time it is claimed that chronic stress and negative affect can result in a disregulated physiological stress system, which may lead to MUS. Previous studies could not demonstrate a straightforward between subject relationship between MUS and stress physiology, supporting the view of independence. The aim of the current study was to further explore this relationship using an improved methodology based on ecologically valid 24-h real-life ambulatory recordings. Seventy-four participants (19 male; 55 female) with heterogeneous MUS were compared with 71 healthy controls (26 male; 45 females). Momentary experienced somatic complaints and mood, heart rate, cardiac autonomic activity, respiration and saliva cortisol were monitored using electronic diary and ambulatory registration devices. Participants with MUS reported much more momentary complaints and negative affect as compared to controls. Although MUS seemed to be associated with elevated heart rate and reduced low and very-low frequency heart period variability, these effects disappeared after controlling for differences in sports behaviour. No group differences were found for cardiac autonomic activity, respiration, end-tidal CO(2) and saliva cortisol. Our 24-h real-life ambulatory study did not support the existence of a connection between MUS and disregulated peripheral stress physiology. Future studies may instead focus on central measures to reveal potential abnormalities such as deviant central processing of visceral signals in MUS patients.
This study investigated the effects of high-carbohydrate (HC) and high-fat (HF) diet on cognitive performance, and subjective and objective sleepiness. Seven male participants were kept awake for 24 h in a metabolic ward. Meals were given every 4h and cognitive performance and sleepiness ratings were assessed hourly. The Karolinska Drowsiness Test (KDT, EEG derived) was performed twice after meal. Performance in simple reaction time showed a significant interaction of diet and the post-prandial period, a slower reaction time was observed for the HC-diet 3.5 h after meal intake. Diet did not affect EEG measures but a general post-prandial increase of objective sleepiness was observed 3.5h after meal servings. The HC-diet was significantly associated with an increase of subjective sleepiness. The study demonstrated that the HC-diet caused larger oscillation in performance and increased sleepiness as compared to HF-diet throughout day and night.
Despite significant gains in the fields of pediatric neuroimaging and developmental neurobiology, surprisingly little is known about the developing human brain or the neural bases of cognitive development. This paper addresses MRI studies of structural and functional changes in the developing human brain and their relation to changes in cognitive processes over the first few decades of human life. Based on post-mortem and pediatric neuroimaging studies published to date, the prefrontal cortex appears to be one of the last brain regions to mature. Given the prolonged physiological development and organization of the prefrontal cortex during childhood, tasks believed to involve this region are ideal for investigating the neural bases of cognitive development. A number of normative pediatric fMRI studies examining prefrontal cortical activity in children during memory and attention tasks are reported. These studies, while largely limited to the domain of prefrontal functioning and its development, lend support for continued development of attention and memory both behaviorally and physiologically throughout childhood and adolescence. Specifically, the magnitude of activity observed in these studies was greater and more diffuse in children relative to adults. These findings are consistent with the view that increasing cognitive capacity during childhood may coincide with a gradual loss rather than formation of new synapses and presumably a strengthening of remaining synaptic connections. It is clear that innovative methods like fMRI together with MRI-based morphometry and nonhuman primate studies will transform our current understanding of human brain development and its relation to behavioral development.
We examined inhibitory mechanisms in dysphoria using direct measures of attentional control. Dysphoric and non-dysphoric participants performed standard and delayed versions of the antisaccade and prosaccade tasks with facial expressions as stimuli. Results showed higher error rates in the standard antisaccade task than in the delayed tasks, with the dysphoric group having higher error rates in response to emotional facial expressions, in particular happy expressions. Our findings indicate impaired attentional processing in response to emotional facial expressions, in particular happy expressions, in dysphoria. Implications for understanding the mechanisms underlying attentional control in dysphoria are discussed.
In this paper we review evidence that suggests that the stimulus evaluation system can pass information to the response activation system before evaluation is completed ("early communication"). This evidence is derived from measures of the lateralized readiness potential, which have been related in previous research to the preparation for movement. Early communication is evident in conflict and congruence paradigms. In both paradigms, a single stimulus, or two different stimuli, deliver two aspects of information. In the conflict paradigm, the first aspect of information (derived from preliminary evaluation) primes the incorrect response, while the second primes the correct response. In the congruence paradigm, information derived from preliminary and complete evaluation is congruent. In both paradigms, lateralized readiness potential measures suggest that preliminary evaluation is able to prime the response system, although the overt motor response may not be released until evaluation is completed. This demonstration of early communication has both theoretical and practical implications. First, it does not support single-decision models of information processing. Second, it suggests that the lateralized readiness potential, a continuous, analog measure of the activity of the response system, can be used to make inferences about the nature of the evaluation process, and to localize the effects of various manipulations on the information processing system.
To access the saliva level of 3-methoxy-4-hydroxy-phenylglycol (sMHPG) as an index of mental health in normal volunteers, we investigated the relationship between the sMHPG and the scores on the general health questionnaire-28 (GHQ-28). A total of 270 normal volunteers answered the GHQ-28 and the sMHPG levels were determined. The sMHPG levels in women and men were comparable. There was a significant negative correlation between the social dysfunction score on the GHQ-28 and sMHPG levels in women (P=0.0035), but not in men. Moreover, the sMHPG levels also correlated with the total GHQ-28 score (P=0.0205), the anxiety and the insomnia score (P=0.0306) in women. These data indicate a high social dysfunction score on the GHQ-28 to be associated with a reduced noradrenergic neuronal tone thus possibly reflecting psychomotor retardation in women.
Research suggests that frontal EEG asymmetry (FA) is a relatively stable trait associated with individual differences in dispositional affect (affective style) and liability to mood disorders. If FA is genetically determined, it can potentially serve as an endophenotype in genetic studies of temperament and mood disorders. The purpose of this study was to assess heritability of FA as well as alpha band EEG power measured at different frontal recording sites. Resting EEG data from a population-based sample of 246 young adult female twins including 73 monozygotic (MZ) and 50 dizygotic (DZ) pairs were analyzed using linear structural equation modeling. FA measured at mid-frontal locations (F3 and F4) showed low but significant heritability, suggesting that 27% of the observed variance can be accounted for by genetic factors. There was no evidence for genetic influences on FA measured at lateral-frontal (F7 and F8) locations. In contrast, alpha band power was highly heritable at all four frontal sites (85-87%). These findings suggest that: (1) genetic influences on FA are very modest and therefore FA has a limited utility as an endophenotype for genetic studies of mood disorders and (2) prefrontal neural circuitry underlying individual differences in affective style is characterized by high developmental plasticity.
Finger length ratio (2D:4D) is a sexually dimorphic trait. Men have relatively shorter second digits (index fingers) than fourth digits (ring fingers). Smaller, more masculine, digit ratios are thought to be associated with either higher prenatal testosterone levels or greater sensitivity to androgens, or both. Men with more masculine finger ratios are perceived as being more masculine and dominant by female observers, and tend to perform better in a number of physical sports. We hypothesized that digit ratio would correlate with propensity to engage in aggressive behavior. We examined the relationship between trait aggression, assayed using a questionnaire, and finger length ratio in both men and women. Men with lower, more masculine, finger length ratios had higher trait physical aggression scores (r(partial) = -0.21, N = 134, P = 0.028). We found no correlation between finger length ratio and any form of aggression in females. These results are consistent with the hypothesis that testosterone has an organizational effect on adult physical aggression in men.
Finger lengths and the ratio of index finger to ring finger length (2D:4D) may be markers of gonadal hormone exposure. The current study investigated possible associations between absolute finger lengths, 2D:4D ratios, and gender-related personality traits in over 2000 participants. Regression analyses showed no associations between men's 2D:4D ratios and gender-related personality traits and weak associations between women's 2D:4D ratios and gender-related occupational preferences. Men's absolute finger lengths were weakly associated with self-ascribed masculinity, and women's absolute finger lengths were weakly associated with masculine occupational preferences. Big Five personality traits were assessed in a subsample of over 1000 participants. Analyses showed a weak positive association between 2D:4D and extraversion and a weak negative association between 2D:4D and openness to experience. Absolute finger lengths showed a weak negative association with agreeableness and a tendency to be associated with women's but not men's openness. Overall, associations between finger-length measures and personality were weak and inconsistent.
Previous research has shown an association between eye contact and prenatal testosterone measured in amniocenteses samples. The purpose of this study was to test the association between eye contact and prenatal androgen action measured via second to fourth digit ratios (2D:4D ratios), and to explore the relationship between eye contact and postnatal testosterone levels. Participants included 72 children, between the ages of 18 and 24 months, and their parents. Salivary testosterone levels were obtained when children were 3-months old. At 18-months, 2D:4D ratios were measured and parent-child dyads participated in an 8-minute play session that was recorded and later coded for duration and frequency of eye contact. Results indicated that larger 2D:4D ratios (indicative of lower androgen levels) significantly predicted longer duration and more frequency of eye contact, while postnatal testosterone levels were unrelated to eye contact. These novel findings suggest prenatal androgens may influence the emergence of social development.
Intersexual and intrasexual variation in second to fourth digit length (2D:4D) in humans may result from differential exposure to fetal testosterone. 2D:4D predicts several physiological, psychological and performance traits in adulthood. These relationships may reflect the 'pleiotropic' effects of testosterone on development of digits and diverse organ systems, which are expressed in adulthood. We hypothesized that 2D:4D also predicts academic success of students. 2D:4D of right hand positively predicted examination marks of males from two three-year degree courses (TYDCs). Marks of females did not covary with 2D:4D. Males from the two TYDCs differed in 2D:4D. The present results thus add to the rapidly accumulating literature on 2D:4D showing correlations with phenotypic traits in humans. If testosterone affects 2D:4D and intellectual performance, our results suggest that testosterone levels are under stabilizing selection because of effects on performance traits documented in previous studies and antagonistic effects on intellectual performance (present study).
The neural basis of abnormal processing of phobia-related linguistic cues in individuals suffering from social phobia is unknown, particularly in respect to different task conditions. Using event-related functional magnetic resonance imaging, this study investigated brain activation to phobia-related and phobia-unrelated words in 19 socially phobic patients and 18 healthy control subjects (HC) while subjects had to attend either to social meaning or to grammatical category of words (direct or indirect task). During the indirect task, patients, compared to HC, showed an increased activation of the amygdala and orbitofrontal cortex (OFC) in response to phobia-related vs. phobia-unrelated words. Activation of the insula was positively correlated with patients' symptom severity during the direct task. The results suggest a specific role of the amygdala and OFC during the processing of verbal phobia-relevant distracting information. In contrast, insula activation seems to be more important for direct processing of disorder-related words, especially in more severe cases of social phobia.
Many variables have been assumed to reflect speed of processing, and most are strongly related to age in the period of adulthood. One of the primary theoretical questions with respect to aging and speed concerns the relative roles of specific and general age-related effects on particular speed variables. Distinguishing between specific (or unique) and general (or shared) age-related influences on measures of speed has been complicated, in part because the issues are sometimes framed in terms of extreme all-or-none positions, and because few researchers have employed analytical procedures suitable for estimating the relative contributions of each type of influence. However, recent methods focusing on partitioning age-related variance have indicated that large proportions of the age-related effects on individual speed variables are shared with age-related effects on other variables. Although these theoretical ideas and analytical procedures are fairly new, they may be relevant to a variety of psychophysiological or neurobiological variables.
Using the Iowa Gambling Task (IGT) and psychophysiological correlates of emotional responses (i.e., heart rate and skin conductance), we investigate the effects of trait anxiety (TA) on decision-making. We find that high TA is associated with both impaired decision-making and increased anticipatory physiological (somatic) responses prior to advantageous trials. For both high and low TA, skin conductance responses preceding advantageous trials predict decisions. At the same time, somatic responses to choice outcomes reflect differences between high and low TA sensitivities to punishments and rewards. The pattern of impaired decision-making and increased somatic markers that we find in high TA may have important implications for neuropsychological decision theory. In particular, it offers an example of defective modulation of somatic signals, coupled with disrupted discrimination of advantageous and disadvantageous choices.
It has been suggested that the P3 event-related potential (ERP) may mark the operation of certain working or long-term memory processes. It has also been reported that cholinergic blockade by scopolamine induces significant memory impairment and is associated with an increased latency, as well as amplitude reduction or abolition of the auditory P3, thus supporting hypothesised links between P3 and long-term memory function. An intriguing anomaly is that, while visual P3 latency is also increased by scopolamine, amplitude is not changed. The aim of this study was to make a more detailed assessment of the effects of scopolamine on the visual P3 at a drug dose known to induce memory impairment. After drug administration, memory performance was significantly impaired and visual P3 latency was significantly increased. There was little evidence of parietal P3 amplitude reduction, but frontal P3 amplitude was significantly reduced in both target and non-target conditions. These findings, when considered in the light of a more recent study of the effects of scopolamine on auditory P3, suggest that cholinergic blockade produces a common effect in both visual and auditory modalities of significant frontal P3 amplitude reduction, but no significant parietal P3 amplitude reduction. These results are consistent with the view that there are modality-independent generators of the parietal and frontal P3. The finding of drug-induced memory impairment and modulations of frontal ERP deflections is also consistent with recent evidence of a significant role for regions of the frontal lobe in encoding and retrieval of long-term memories.
Oxytocin plays an important role in human attachment, trust, social perception, memory, and fear regulation. Evidence suggests that CD38, a regulator of oxytocin release, may also be critical in these processes. The purpose of this study was to investigate the predictors of plasma oxytocin level measured after a task requiring intimate trust (secret sharing), modeling psychotherapeutic processes, and a neutral social interaction. Results revealed that peripheral CD38 expression positively predicted both trust-related and trust-unrelated oxytocin levels. In addition, habituation of arousal, as measured by skin conductance response, and attachment anxiety also emerged as predictors of oxytocin level in the trust-related condition. These results suggest that CD38 plays a general role in oxytocin secretion, whereas habituation of arousal and attachment anxiety are specifically related to situations involving intimate trust.
Attention Deficit Hyperactivity Disorder (ADHD) is a developmental disorder that has previously been related to a decreased sensitivity to errors and feedback. Supplementary to the traditional performance measures, this study uses autonomic measures to study this decreased sensitivity in ADHD and the modulating effects of medication. Children with ADHD, on and off Methylphenidate (Mph), and typically developing (TD) children performed a selective attention task with three feedback conditions: reward, punishment and no feedback. Evoked Heart Rate (EHR) responses were computed for correct and error trials. All groups performed more efficiently with performance feedback than without. EHR analyses, however, showed that enhanced EHR decelerations on error trials seen in TD children, were absent in the medication-free ADHD group for all feedback conditions. The Mph-treated ADHD group showed 'normalised' EHR decelerations to errors and error feedback, depending on the feedback condition. This study provides further evidence for a decreased physiological responsiveness to errors and error feedback in children with ADHD and for a modulating effect of Mph.
The serotonin 5HTR2C receptor has been shown to mediate HPA axis activation during stress. We hypothesized that a functional polymorphism (rs6318) of the 5HTR2C gene would be associated with HPA axis response to a laboratory stress protocol. The present sample consisted of 41 men (22 African Americans, 19 Caucasians). We found that at rest men with the more active rs6318 Ser23 C allele had similar cortisol values compared to those with the less active Cys23 G allele. During laboratory stress, however, men with the Ser23 C allele exhibited the predicted significantly higher cortisol levels (p<0.001), as well as larger increases in anger (p=0.08) and depressive mood (p=0.006) ratings, compared to the Cys23 G carriers. The increase in cortisol was significantly related to the increases in ratings of anger and depression assessed before and after the emotion induction, and these correlations became nonsignificant when rs6318 genotype was covaried. We conclude that genetic variation in 5HTR2C may be associated with HPA axis activation and stimulated by emotional stress, and also with both psychological and physiological endophenotypes that increase the risk of cardiovascular disease and type-2 diabetes.
Here we examine the effects of both self-reported and independent observer-reported environmental risk indices, the serotonin transporter gene promoter (5HTTLPR) polymorphism, and their interaction on self-esteem. This trait was assessed during early and mid adolescence (mean age=14 and 16.5, respectively) and young adulthood (mean age=21.8) in a prospective cohort of 1214 unrelated participants in the Longitudinal Study of Adolescent Health (Add Health). Using structural equation modeling we identified a gene-environment (G×E) interaction using observer-report but not self-report measures of environmental stress exposure during adolescence: 5HTTLPR genotype and observer-reports of home and neighborhood quality (HNQ) during adolescence interacted to predict self-esteem levels in young adulthood (p<.004). Carriers of the s allele who lived in poor HNQ conditions during adolescence reported lower self-esteem in young adulthood than those with a good HNQ during adolescence. In contrast, among individuals with the l/l genotype, adolescent HNQ did not predict adulthood self-esteem. Genes may moderate the effect of adolescent environmental conditions on adulthood self-esteem.
Fear extinction is the decrease in conditioned fear responses that normally occurs when a conditioned stimulus (CS) is repeatedly presented in the absence of the aversive unconditioned stimulus (US). Extinction does not erase the initial CS-US association, but is thought to form a new memory. After extinction training, extinction memory competes with conditioning memory for control of fear expression. Deficits in fear extinction are thought to contribute to post-traumatic stress disorder (PTSD). Herein, we review studies performed in rats showing that the medial prefrontal cortex plays a critical role in the retention and expression of extinction memory. We also review human studies indicating that prefrontal areas homologous to those critical for extinction in rats are structurally and functionally deficient in patients with PTSD. We then discuss how findings from rat studies may allow us to: (1) develop new fear extinction paradigms in humans, (2) make specific predictions as to the location of extinction-related areas in humans, and (3) improve current extinction-based behavioral therapies for anxiety disorders.