Sample Of Healthy Young Adults Research Articles

Human navigation network: the intrinsic functional organization and behavioral relevance.

Spatial navigation is a crucial ability for living. Previous work has revealed multiple distributed brain regions associated with human navigation. However, little is known about how these regions work together as a network (referred to as navigation network) to support flexible navigation. In a novel protocol, we combined neuroimaging meta-analysis, and functional connectivity and behavioral data from the same subjects. Briefly, we first constructed the navigation network for each participant, by combining a large-scale neuroimaging meta-analysis (with the Neurosynth) and resting-state functional magnetic resonance imaging. Then, we investigated multiple topological properties of the navigation networks, including small-worldness, modularity, and highly connected hubs. Finally, we explored the behavioral relevance of these intrinsic properties in a large sample of healthy young adults (N=190). We found that navigation networks showed small-world and modular organization at global level. More importantly, we found that increased small-worldness and modularity of the navigation network were associated with better navigation ability. Finally, we found that the right retrosplenial complex (RSC) acted as one of the hubs in the navigation network, and that higher betweenness of this region correlated with better navigation ability, suggesting a critical role of the RSC in modulating the navigation network in human brain. Our study takes one of the first steps toward understanding the underlying organization of the navigation network. Moreover, these findings suggest the potential applications of the novel approach to investigating functionally meaningful networks in human brain and their relations to the behavioral impairments in the aging and psychiatric patients.

Effects of parental emotional warmth on the relationship between regional gray matter volume and depression-related personality traits

ABSTRACTThe depression-related personality trait is associated with the severity of patients’ current depressive symptoms and with the vulnerability to depression within the nonclinical groups. However, little is known about the anatomical structure associated with the depression-related personality traits within the nonclinical sample. Parenting behavior is associated with the depression symptoms; however, whether or not parenting behavior influence the neural basis of the depression-related personality traits is unclear. Thus in current study, first, we used voxel-based morphometry to identify the brain regions underlying individual differences in depression-related personality traits, as measured by the revised Neuroticism-Extraversion-Openness Personality Inventory, in a large sample of young healthy adults. Second, we use mediation analysis to investigate the relationship between parenting behavior and neural basis of depression-related personality traits. The results revealed that depression-related personality traits were positively correlated with gray matter volume mainly in medial frontal gyrus (MFG) that is implicated in the self-referential processing and emotional regulation. Furthermore, parental emotional warmth acted as a mediational mechanism underlying the association between the MFG volume and the depression-related personality trait. Together, our findings suggested that the family environment might play an important role in the acquisition and process of the depression-related personality traits.

Psychopathic traits affect the visual exploration of facial expressions

Deficits in emotional reactivity and recognition have been reported in psychopathy. Impaired attention to the eyes along with amygdala malfunctions may underlie these problems. Here, we investigated how different facets of psychopathy modulate the visual exploration of facial expressions by assessing personality traits in a sample of healthy young adults using an eye-tracking based face perception task. Fearless Dominance (the interpersonal-emotional facet of psychopathy) and Coldheartedness scores predicted reduced face exploration consistent with findings on lowered emotional reactivity in psychopathy. Moreover, participants high on the social deviance facet of psychopathy (‘Self-Centered Impulsivity’) showed a reduced bias to shift attention towards the eyes. Our data suggest that facets of psychopathy modulate face processing in healthy individuals and reveal possible attentional mechanisms which might be responsible for the severe impairments of social perception and behavior observed in psychopathy.

Spinal shape analysis in 1,020 healthy young adults aged from 19 to 30 years

Background: A number of studies on diseased spine have been published; however, there is a relative paucity of studies investigating spine shape characteristics in healthy populations. Such characteristics are needed for diagnostics of spine disorders and assessment of changes in the spinal shape that may have been caused by influence of the modern life style or intensive sport activity. Objective: The aim of the study was to determine characteristics of the spine shape in a large sample of healthy young adults. Methods: Population cross-sectional study. A non-radiographic surface method (system DTP-3) was used for the assessment of spine shape in the sagittal and frontal planes. A total of 1,020 participants (440 men, 580 women) took part in the study, their mean (± SD) age was 21.8 ± 1.9 years (range 19.1-29.7) for men and 21.9 ± 1.8 years (range 19.3-29.7) for women. All data were checked for normality and are presented as means, standard deviations, ranges, skewness, and kurtosis. Differences between the sexes were assessed with the two-sample t-test. Results: The average sagittal spinal shape was C3 - 12.9° - C7 - 43.0° - T10 - 27.1° - L5 for men and C3 - 12.1° - C6 - 44.5° - T11 - 34.1° - L5 for women. Men showed a significantly smaller thoracic kyphosis and lumbar lordosis curvatures than women. The average curvature due to the lateral deviation in the frontal plane was 6.1° for both sexes, the curvature was larger than 10° in 9.1% of men and 8.8% of women. We found left lateral deviation in 72.5% of men and in 63.6% of women. Conclusions: The study provides characteristics of the spine shape in a large sample of healthy young adults. Such characteristics should be part and parcel of determining the cut-off level for physiological spinal shape. Based on the results of the study, we suggest a lateral deviation of 10° as the maximum for a curvature to be still considered non-pathological.

Lutein and zeaxanthin status and auditory thresholds in a sample of young healthy adults

Objectives: Dietary carotenoids lutein (L) and zeaxanthin (Z) have been linked to improved visual and cognitive function. These effects are thought to be mediated by the presence of these pigments in critical regions of the retina and brain. There, it has been postulated that L and Z mediate improved performance by enhancing neural efficiency. The auditory system also relies on efficient segregating of signals and noise and LZ are also found in the auditory cortex. The purpose of the present study was to investigate the influence of LZ status (as assessed by the measuring levels in retina) on auditory thresholds in young non-smokers (N = 32, M = 20.72 ± 3.28 years).Design: LZ status was determined by measuring macular pigment (MP) optical density using a standardized psychophysical technique (customized heterochromatic flicker photometry). Auditory thresholds were assessed with puretone thresholds and puretone auditory thresholds in white noise.Results: MP density was related to many, but not all, of the puretone thresholds we tested: 250 Hz (F(6,32) = 4.36, P < 0.01), 500 Hz (F(6,32) = 2.25, P < 0.05), 1000 Hz (F(6,32) = 3.22, P < 0.05), and 6000 Hz (F(6,32) = 2.56, P < 0.05).Conclusion: The overall pattern of results is consistent with a role for L and Z in maintaining optimal auditory function.

Resting-State Coupling between Core Regions within the Central-Executive and Salience Networks Contributes to Working Memory Performance.

Previous studies investigated the distinct roles played by different cognitive regions and suggested that the patterns of connectivity of these regions are associated with working memory (WM). However, the specific causal mechanism through which the neuronal circuits that involve these brain regions contribute to WM is still unclear. Here, in a large sample of healthy young adults, we first identified the core WM regions by linking WM accuracy to resting-state functional connectivity with the bilateral dorsolateral prefrontal cortex (dLPFC; a principal region in the central-executive network, CEN). Then a spectral dynamic causal modeling (spDCM) analysis was performed to quantify the effective connectivity between these regions. Finally, the effective connectivity was correlated with WM accuracy to characterize the relationship between these connections and WM performance. We found that the functional connections between the bilateral dLPFC and the dorsal anterior cingulate cortex (dACC) and between the right dLPFC and the left orbital fronto-insular cortex (FIC) were correlated with WM accuracy. Furthermore, the effective connectivity from the dACC to the bilateral dLPFC and from the right dLPFC to the left FIC could predict individual differences in WM. Because the dACC and FIC are core regions of the salience network (SN), we inferred that the inter- and causal-connectivity between core regions within the CEN and SN is functionally relevant for WM performance. In summary, the current study identified the dLPFC-related resting-state effective connectivity underlying WM and suggests that individual differences in cognitive ability could be characterized by resting-state effective connectivity.

Structural asymmetry of the human cerebral cortex: Regional and between-subject variability of surface area, cortical thickness, and local gyrification

Structural asymmetry varies across individuals, brain regions, and metrics of cortical organization. The current study investigated regional differences in asymmetry of cortical surface area, thickness, and local gyrification, and the extent of between-subject variability in these metrics, in a sample of healthy young adults (N=200). Between-subject variability in cortical structure may provide a means to assess the extent of biological flexibility or constraint of brain regions, and we explored the potential influence of this variability on the phenotypic expression of structural asymmetry. The findings demonstrate that structural asymmetries are nearly ubiquitous across the cortex, with differing regional organization for the three cortical metrics. This implies that there are multiple, only partially overlapping, maps of structural asymmetry. The results further indicate that the degree of asymmetry of a brain region can be predicted by the extent of the region's between-subject variability. These findings provide evidence that reduced biological constraint promotes the expression of strong structural asymmetry.

Inter-ocular asymmetry of retinal parameters as measured with Ocular Coherence Tomography (OCT) in a sample of healthy young adults

Inter-ocular asymmetry of retinal parameters as measured with Ocular Coherence Tomography (OCT) in a sample of healthy young adults

Cardiac morphology and function reference values derived from a large subset of healthy young Caucasian adults by magnetic resonance imaging.

Assessment of cardiac anatomy and function by cardiovascular magnetic resonance (CMR) is accurate and reproducible and is commonly performed to clarify borderline results obtained by other techniques. Normal reference values are lacking in a large sample of young healthy adults. As CMR is increasingly solicited to discriminate normality from equivocal disease in this population, we sought to determine reliable reference values. A sample of 434 Caucasian adults aged 26 ± 4 years (45% male) without cardiovascular disease or risk factors (including obesity and smoking) underwent CMR. Blood pressure, electrocardiogram, and plasma markers (lipid profile, fasting glucose, troponin, and Nt-pro-BNP) were within normal limits and typical of a low-cardiometabolic-risk profile. End-diastolic (ED), end-systolic (ES), and stroke volumes were greater in men for left and right atria and ventricles. Left ventricular (LV) mass was higher in men. ED wall thickness of all segments was greater in men, whereas ES wall thickening (segmental function) was similar in both genders. After normalization to body surface area, all gender differences remained. Left and right ventricular volumes were lower, and left atrial volumes were higher in older individuals. In contrast, LV mass was not associated with age. This is the first large database of reference ranges for ventricular and atrial functions, volumes, and mass in young Caucasian men and women devoid of cardiovascular disease and risk factors. These data will contribute to improving the accuracy of CMR interpretation for clinical and research applications.

Neural correlates of psychological resilience and their relation to life satisfaction in a sample of healthy young adults

Psychological resilience refers to the ability to thrive in the face of risk and adversity, which is crucial for individuals' mental and physical health. However, its precise neural correlates are still largely unknown. Here we used resting-state functional magnetic resonance imaging (rs-fMRI) to identify the brain regions underlying this construct by correlating individuals' psychological resilience scores with the regional homogeneity (ReHo) and then examined how these resilience-related regions predicted life satisfaction in a sample of healthy young adults. We found that the ReHo in the bilateral insula, right dorsal anterior cingulate cortex (dACC) and right rostral ACC (rACC) negatively predicted individual differences in psychological resilience, revealing the critical role of the salience network (SN) in psychological resilience. Crucially, the ReHo in the dACC within the SN mediated the effects of psychological resilience on life satisfaction. In summary, these findings suggest that spontaneous activity of the human brain reflect the efficiency of psychological resilience and highlight the dACC within the SN as a neural substrate linking psychological resilience and life satisfaction.

Examining the relation between respiratory sinus arrhythmia and depressive symptoms in emerging adults: A longitudinal study

Major depressive disorder (MDD) is a debilitating and prevalent disorder associated with lower quality of life and substantial economic burden. Recently, there has been strong interest in respiratory sinus arrhythmia (RSA) as a biological predictor of later depression. Theoretical work suggests that higher resting RSA indexes physiological flexibility and better emotion regulation whereas lower RSA may mark vulnerability for psychopathology. However, empirical findings have varied. This study examined whether lower resting RSA predicted later depressive symptoms in a sample of healthy young adults across one year (n=185). Results indicate that year one (Y1) resting RSA predicted Y2 depressive symptoms. This finding remained significant when accounting for the stability of RSA and depressive symptoms across both time points and when including trait anxiety, body mass index, and medication use in statistical models. Findings provide further support for RSA as a promising biological marker for understanding and predicting depressive symptoms.

Acute fluoxetine modulates emotional processing in young adult volunteers.

Fluoxetine is generally regarded as the first-line pharmacological treatment for young people, as it is believed to show a more favourable benefit:risk ratio than other antidepressants. However, the mechanisms through which fluoxetine influences symptoms in youth have been little investigated. This study examined whether acute administration of fluoxetine in a sample of young healthy adults altered the processing of affective information, including positive, sad and anger cues. A total of 35 male and female volunteers aged between 18 and 21 years old were randomized to receive a single 20 mg dose of fluoxetine or placebo. At 6 h after administration, participants completed a facial expression recognition task, an emotion-potentiated startle task, an attentional dot-probe task and the Rapid Serial Visual Presentation. Subjective ratings of mood, anxiety and side effects were also taken pre- and post-fluoxetine/placebo administration. Relative to placebo-treated participants, participants receiving fluoxetine were less accurate at identifying anger and sadness and did not show the emotion-potentiated startle effect. There were no overall significant effects of fluoxetine on subjective ratings of mood. Fluoxetine can modulate emotional processing after a single dose in young adults. This pattern of effects suggests a potential cognitive mechanism for the greater benefit:risk ratio of fluoxetine in adolescent patients.

Risky decision-making and ventral striatal dopamine responses to amphetamine: A positron emission tomography [11C]raclopride study in healthy adults

Recent functional magnetic resonance imaging (fMRI) studies have provided compelling evidence that corticolimbic brain regions are integrally involved in human decision-making. Although much less is known about molecular mechanisms, there is growing evidence that the mesolimbic dopamine (DA) neurotransmitter system may be an important neural substrate. Thus far, direct examination of DA signaling in human risk-taking has centered on gambling disorder. Findings from several positron emission tomography (PET) studies suggest that dysfunctions in mesolimbic DA circuits may play an important role in gambling behavior. Nevertheless, interpretation of these findings is currently hampered by a need for better understanding of how individual differences in regional DA function influence normative decision-making in humans. To further our understanding of these processes, we used [11C]raclopride PET to examine associations between ventral striatal (VS) DA responses to amphetamine (AMPH) and risky decision-making in a sample of healthy young adults with no history of psychiatric disorder, Forty-five male and female subjects, ages 18–29years, completed a computerized version of the Iowa Gambling Task. Participants then underwent two 90-minute PET studies with high specific activity [11C]raclopride. The first scan was preceded by intravenous saline; the second, by intravenous AMPH (0.3mg/kg). Findings of primary analyses showed that less advantageous decision-making was associated with greater right VS DA release; the relationship did not differ as a function of gender. No associations were observed between risk-taking and left VS DA release or baseline D2/D3 receptor availability in either hemisphere. Overall, the results support notions that variability in striatal DA function may mediate inter-individual differences in risky decision-making in healthy adults, further suggesting that hypersensitive DA circuits may represent a risk pathway in this population.

Psychosocial Stressors and Salivary Cortisol Levels in A Sample of Healthy Young Adults

Psychosocial Stressors and Salivary Cortisol Levels in A Sample of Healthy Young Adults

Neuroimaging of Brain Networks and Function

The human brain consists of multiple interconnected large scale networks. Recent advances in structural and functional neuroimaging techniques have introduced new concepts and approaches to noninvasively assess brain networks, which has attracted enormous research interest. To examine human brain function, traditional neuroimaging research typically focuses on localizing neural responses to varying external stimuli or task demands. However, task-induced phasic neuronal responses account for less than 5% of the brain's energy budget, while the majority of the brain's energy is used for intrinsic spontaneous brain activities. Although the number of human brain imaging studies and the knowledge obtained from these studies are growing exponentially, there are many more unanswered questions regarding the structural organization and the function of brain networks. In this special issue, we have invited a few papers that studied structural and functional brain networks using various neuroimaging methods including resting-state fMRI, diffusion tensor imaging (DTI), arterial spin labeling (ASL) perfusion MRI, functional near-infrared spectroscopy (fNIRS), magnetoencephalogram (MEG), and imaging genetics. These studies involve healthy populations as well as multiple clinical populations, including patients with cirrhosis, mild cognitive impairment (MCI) and Alzheimer's disease (AD), attention deficit hyperactivity disorder (ADHD), and epilepsy. This specific issue includes several studies focusing on clinical populations. In one study by G. Zheng and colleagues, resting-state fMRI was used to examine functional connectivity changes in the progression of minimal hepatic encephalopathy and found continuously impaired intra- and intermodular connectivity in patients with cirrhosis. In another study, Y.-Y. Wai and colleagues used tract-based spatial statistics of DTI to characterize white matter integrity in different subtypes of MCI, including amnestic MCI, dysexecutive MCI, AD, and healthy controls. They found that amnestic MCI and AD patients share significant white matter damage, whereas dysexecutive MCI patients appear to have a distinct pathogenesis. In the third study, A. dos Santos Siqueira and colleagues used graph theory and analyzed a resting-state fMRI data set from healthy children and ADHD patients in the ADHD-200 database. Distinct patterns of network dysfunction were evident for both inattentive and combined ADHD subtypes. However, the authors observed that the classification scores for discriminating between ADHD and healthy subjects were close to chance and that functional connectivity estimations were strongly dependent on the sample characteristics. In the final study, H. Zhu and colleagues used resting-state MEG to identify the epileptogenic and other abnormal regions in patients with left temporal lobe epilepsy (TLE) and provided further evidence supporting the notion that TLE is not a focal focus but a multifocus disease. A few other studies in this specific issue examined brain networks and function in normal population. In one study by H. Lei and colleagues, resting-state fMRI was integrated with genetics to examine the effect of genetic variation of the MAOA gene on resting brain activity in healthy male adolescents. Those with the low-activity MAOA genotype exhibited lower amplitude of low-frequency fluctuation (ALFF) in the pons compared to those with the high-activity MAOA genotype. Moreover, there was a significant genotype by ALFF interaction effect on impulsivity scores. In another study, H. Niu and colleagues examined the effects of learning on resting brain activity using fNIRS and demonstrated that 5 days of visual perceptual learning significantly altered resting oxygenated hemoglobin functional connectivity between visual cortex and frontal/central areas. In the study by C. Xu and colleagues, the regional homogeneity (ReHo) approach was used as an index in the resting-state fMRI to investigate gender differences in spontaneous brain activity among a large sample of young healthy adults. This study found significant ReHo differences in multiple cortical regions and resting-state networks between male and female subjects. This specific issue also includes two studies on neuroimaging methods and one review paper. In one study, X. Li and colleagues compared FAIR and PICORE sequences and systematically optimized ASL imaging parameters for measuring cerebellum grey matter and white matter perfusion. In another study, M. Gorges and colleagues demonstrated a potential framework for multiparametric functional connectivity mapping through combination of resting-state fMRI with DTI. Finally, in the review paper, T. K. Das and colleagues highlighted the structure-function relationship of the brain networks using the Ising model and graph theory. In summary, studies published in this specific issue demonstrate a few examples of continuous efforts to integrate structural and functional neuroimaging methods as well as other research modalities in order to elucidate brain networks and their function in both normal healthy population and clinical patients. Hengyi Rao Danny Jiongjiong Wang Yihong Yang Yong He

Examining gray matter structures associated with individual differences in global life satisfaction in a large sample of young adults.

Although much attention has been directed towards life satisfaction that refers to an individual's general cognitive evaluations of his or her life as a whole, little is known about the neural basis underlying global life satisfaction. In this study, we used voxel-based morphometry to investigate the structural neural correlates of life satisfaction in a large sample of young healthy adults (n = 299). We showed that individuals' life satisfaction was positively correlated with the regional gray matter volume (rGMV) in the right parahippocampal gyrus (PHG), and negatively correlated with the rGMV in the left precuneus and left ventromedial prefrontal cortex. This pattern of results remained significant even after controlling for the effect of general positive and negative affect, suggesting a unique structural correlates of life satisfaction. Furthermore, we found that self-esteem partially mediated the association between the PHG volume and life satisfaction as well as that between the precuneus volume and global life satisfaction. Taken together, we provide the first evidence for the structural neural basis of life satisfaction, and highlight that self-esteem might play a crucial role in cultivating an individual's life satisfaction.

Extraversion mediates the relationship between structural variations in the dorsolateral prefrontal cortex and social well-being

Social well-being reflects the appraisal of one's circumstance and functioning in society, which is crucial for individuals' mental and physical health. However, little is known about the neural processes associated with social well-being. In this study, we used voxel-based morphometry (VBM) to identify the brain regions underlying individual differences in social well-being, as measured by the Social Well-being Scale (SWBS), in a large sample of young healthy adults. We found that social well-being was negatively correlated with gray matter volume in left mid-dorsolateral prefrontal cortex (mid-DLPFC) that is implicated in executive functioning, emotional regulation and social reasoning. The results remained significant even after controlling for the effect of socioeconomic status. Furthermore, although basic personality factors such as neuroticism, extraversion, and conscientiousness (as measured by the NEO Personality Inventory) all contributed to social well-being, only extraversion acted as a mediational mechanism underlying the association between the left mid-DLPFC volume and social well-being. Together, our findings provide the first evidence for the structural basis of individual differences in social well-being, and suggest that the personality trait of extraversion might play an important role in the acquisition and process of social well-being.

Vertical brushing versus horizontal brushing: a randomized split-mouth clinical trial.

The aim of this randomized, single-blind, splitmouth design, clinical trial was to evaluate the effectiveness in plaque removal of two brushing methods, the vertical and the horizontal, in a sample of healthy young adults. Forty-nine subjects were enrolled and 43 completed the study. All subjects abstained from oral hygiene practices for 48 hours. Plaque and gingival abrasions were recorded according to the Rustogi Modified Navy Plaque Index (RMNPI) and the van der Weijden method by one calibrated examiner before and immediately after the brushing session. A dental hygienist performed the two brushing methods using a randomized split-mouth design. The average plaque scores from the whole mouth, interproximal surfaces, and gingival margin were obtained before and after brushing, and the differences were evaluated using one-way analysis of variance. The differences in mean plaque scores between pre- and postbrushing were statistically significant for both methods. Considering the interbrushing differences, the vertical method produced lower plaque scores compared to the horizontal for the whole mouth (P=.02). In the interproximal surfaces, the vertical method removed more plaque compared to the horizontal one (P<.01). In the gingival margin no statistically significant differences in plaque scores were recorded. Only 10 gingival abrasions were registered, mainly produced by the horizontal method. RESULTS suggest that both toothbrushing methods are effective in plaque removal; nevertheless, the vertical brushing method has demonstrated to remove more plaque from the interproximal surfaces than the horizontal method.

Gender-specific neuroanatomical basis of behavioral inhibition/approach systems (BIS/BAS) in a large sample of young adults: A voxel-based morphometric investigation

The behavioral inhibition system (BIS) and the behavioral activation system (BAS) are two fundamental motivational systems which are not only responsible for affective states, behavior and personality, but also related to predispositions for various forms of psychopathology. A wide range of previous studies revealed sex differences in both BIS/BAS and affective disorders (e.g., anxiety disorder) and externalizing disorders (e.g., addictive and impulsive behaviors), and a close link might exist between them. It remains to be clarified, however, whether the relationships between neuroanatomical characteristics and BIS/BAS exhibit sex differences. To investigate, voxel-based morphometry (VBM) was used to examine sex differences in the correlations between regional gray matter volume (rGMV) and scores on the Behavioral Inhibition System/Behavioral Activation System (BIS/BAS) scale in a large sample of healthy young adults (n=353). Results showed that females displayed a negative correlation between BIS sensitivity and rGMV in the parahippocampal gyrus (PHG), as well as positive correlations between BAS sensitivity and rGMV in the ventromedial prefrontal cortex (vmPFC) and inferior parietal lobule (IPL), whereas males showed the opposite pattern. These findings suggest that the brain regions associated with processing of negative emotions (PHG) and reward-related information (vmPFC and IPL) may contribute to sex-related differences in rGMV correlates of BIS and BAS, respectively. The present findings demonstrated the evidence of sex-linked neuroanatomical background of BIS and BAS among non-clinical subjects and might encourage future research into the gender-specific relationships between BIS/BAS and related affective disorders and externalizing disorders.

The impact of sex and menstrual cycle on the acoustic startle response

Sex differences in fear and anxiety have been widely reported although results are not entirely consistent depending on measures used. Also, a possible influence of the menstrual cycle is often not taken into account, and effect sizes are not always discussed. In a sample of healthy young adults (n=111 women without hormonal contraceptives and n=107 men) the acoustic startle response (ASR) and emotional ASR modulation were analysed. We found no significant effect of sex on ASR (p=.269) but a significant effect of menstrual cycle (p=.027, η2=0.105). Compared to men, women showed increased ASR during the late luteal phase probably reflecting elevated negative emotionality, and during ovulation which, however, might be due to increased auditory sensitivity and changes in general CNS arousal. Neither sex nor menstrual cycle affected startle modulation. Thus, at least in young adults, menstrual cycle but not sex per se appears to contribute significantly to ASR variance.