Sample Of Healthy Young Adults Research Articles

The acute side effects of bright light therapy: a placebo-controlled investigation.

Despite the emergence of numerous clinical and non-clinical applications of bright light therapy (LT) in recent decades, the prevalence and severity of LT side effects have not yet been fully explicated. A few adverse LT effects—headache, eye strain, irritability, and nausea—have been consistently reported among depressed individuals and other psychiatric cohorts, but there exists little published evidence regarding LT side effects in non-clinical populations, who often undergo LT treatment of considerably briefer duration. Accordingly, in the present study we examined, in a randomized sample of healthy young adults, the acute side effects of exposure to a single 30-minute session of bright white light (10,000 lux) versus dim red light (< 500 lux). Across a broad range of potential side effects, repeated-measures analyses of variance revealed no significant group-by-time (Pre, Post) interactions. In other words, bright light exposure was not associated with a significantly higher incidence of any reported side effect than was the placebo control condition. Nevertheless, small but statistically significant increases in both eye strain and blurred vision were observed among both the LT and control groups. Overall, these results suggest that the relatively common occurrence of adverse side effects observed in the extant LT literature may not fully extend to non-clinical populations, especially for healthy young adults undergoing LT for a brief duration.

Frontal cortical thinning and subcortical volume reductions in early adulthood obesity

Obesity depends on homeostatic and hedonic food intake behavior, mediated by brain plasticity changes in cortical and subcortical structures. The aim of this study was to investigate cortical thickness and subcortical volumes of regions related to food intake behavior in a healthy young adult sample with obesity. Thirty-seven volunteers, 19 with obesity (age=33.7±5.7 (20–39) years body-mass index (BMI)=36.08±5.92 (30.10–49.69)kg/m2) and 18 controls (age=32.3±5.9 (21–40) years; BMI=22.54±1.94 (19.53–24.97)kg/m2) participated in the study. Patients with neuropsychiatric or biomedical disorders were excluded. We used FreeSurfer software to analyze structural magnetic resonance images (MRI) and obtain global brain measures, cortical thickness and subcortical volume estimations. Finally, correlation analyses were performed for brain structure data and obesity measures. There were no between-group differences in age, gender, intelligence or education. Results showed cortical thickness reductions in obesity in the left superior frontal and right medial orbitofrontal cortex. In addition, the obesity group had lower ventral diencephalon and brainstem volumes than controls, while there were no differences in any other subcortical structure. There were no statistically significant correlations between brain structure and obesity measures. Overall, our work provides evidence of the structural brain characteristics associated with metabolically normal obesity. We found reductions in cortical thickness, ventral diencephalon and brainstem volumes in areas that have been implicated in food intake behavior.

Action modulated cognition: The influence of sensori–motor experience on the global processing bias

Whether we are aware of it or not, cognition is inherently biased. Researchers have attempted to modulate these biases using prism adaptation in both healthy and patient populations. Recent research suggests that prisms themselves might not be necessary; simply interacting with one side of space can produce similar effects (Dupierrix, Alleysson, Ohlmann and Chokron (2008). Brain Research, 1214, 127–135). Here we tested whether sensori–motor interaction with the environment affects aspects of cognition that should at first glance appear to be unrelated. While previous research involved tasks that were largely directional in nature (e.g., line bisection), we chose a task without a directional component, the hierarchical figures task (Navon, (1977). Cognitive Psychology, 9, 353–383). In a sample of healthy young adults, we found that after 5min of lateralized pointing (pointing solely to the left or right side of space), performance on the hierarchical figures task varied significantly as a function of pointing direction: interference from irrelevant global information increased after interacting with the left side of space and decreased after interacting with the right side of space. We discuss the results in relation to a “hemispheric imbalance” hypothesis. Our findings demonstrate that cognition can be readily influenced by interactions with the environment even without artificially distorting normal perceptuo–motor relationships.

Repeated measurement of salivary cortisol within and across days among shy young adults

Temperamental shyness emerges early in childhood and remains relatively stable throughout development and has been associated with high and low levels of the stress hormone cortisol. Studies examining the relation between shyness and cortisol have been limited because they have traditionally collected only one measure of cortisol on a single day in the laboratory, restricting the reliability and diurnal profile of the measure in the participant’s everyday environment. We collected 15 saliva samples across three separate days (i.e., upon waking, +60min post-waking, +8h post-waking, +10h post-waking, and bedtime) in a sample of healthy young adults selected for high and low shyness in order to characterize a portion of the diurnal cortisol rhythm. Overall, shy individuals demonstrated relatively lower cortisol across the day and across multiple mornings than non-shy adults. Higher self-reported social anxiety across multiple measures was also related to lower total cortisol levels across all participants. The present study replicates and extends our previous findings of low salivary cortisol measured in the laboratory in shy adults to repeated measurement in their everyday environments.

Heterogeneity of strategy use in the Iowa gambling task: A comparison of win-stay/lose-shift and reinforcement learning models

The Iowa gambling task (IGT) has been used in numerous studies, often to examine decision-making performance in different clinical populations. Reinforcement learning (RL) models such as the expectancy valence (EV) model have often been used to characterize choice behavior in this work, and accordingly, parameter differences from these models have been used to examine differences in decision-making processes between different populations. These RL models assume a strategy whereby participants incrementally update the expected rewards for each option and probabilistically select options with higher expected rewards. Here we show that a formal model that assumes a win-stay/lose-shift (WSLS) strategy--which is sensitive only to the outcome of the previous choice--provides the best fit to IGT data from about half of our sample of healthy young adults, and that a prospect valence learning (PVL) model that utilizes a decay reinforcement learning rule provides the best fit to the other half of the data. Further analyses suggested that the better fits of the WSLS model to many participants' data were not due to an enhanced ability of the WSLS model to mimic the RL strategy assumed by the PVL and EV models. These results suggest that WSLS is a common strategy in the IGT and that both heuristic-based and RL-based models should be used to inform decision-making behavior in the IGT and similar choice tasks.

The survey of autobiographical memory (SAM): A novel measure of trait mnemonics in everyday life

Compared to the abundance of laboratory-based memory tasks, few measures exist to assess self-reported memory function. This need is particularly important for naturalistic mnemonic capacities, such as autobiographical memory (recall of events and facts from one's past), because it is difficult to reliably assess in the laboratory. Furthermore, naturalistic mnemonic capacities may show stable individual differences that evade the constraints of laboratory testing. The Survey of Autobiographical Memory (SAM) was designed to assess such trait mnemonics, or the dimensional characterization of self-reported mnemonic characteristics. The SAM comprises items assessing self-reported episodic autobiographical, semantic, and spatial memory, as well as future prospection. In a large sample of healthy young adults, the latent dimensional structure of the SAM was characterized with multiple correspondence analysis (MCA). This analysis revealed dimensions corresponding to general mnemonic abilities (i.e., good vs poor memory across subtypes), spatial memory, and future prospection. While episodic and semantic items did not separate in this data-driven analysis, these categories did show expected dissociations in relation to depression history and to laboratory-based measures of recollection. Remote spatial memory as assessed by the SAM showed the expected advantage for males over females. Spatial memory was also related to autobiographical memory performance. Brief versions of the SAM are provided for efficient research applications. Individual differences in memory function are likely related to other health-related factors, including personality, psychopathology, dementia risk, brain structure and function, and genotype. In conjunction with laboratory or performance based assessments, the SAM can provide a useful measure of naturalistic self-report trait mnemonics for probing these relationships.

753 Impact of Fat Distribution on the Cardiometabolic Risk Profile of Non-Obese Healthy Young Men and Women

Relative contributions of abdominal versus cardiac adipose tissues to the cardiometabolic profile of young and healthy adults are unknown. We investigated the associations between subcutaneous abdominal adipose tissue (SAT), visceral abdominal adipose tissue (VAT) and epicardial adipose tissue (EAT) with markers of the cardiometabolic profile in young and apparently healthy males and females. Two hundred and eighty young and apparently healthy subjects (no known risk factors of cardiovascular/metabolic disease, 48% male; age 18 to 35 years; body mass index (BMI) <30 kg/m2) underwent magnetic resonance imaging after voluntary recruitment in the community. We quantified abdominal subcutaneous adipose tissue (SAT), visceral abdominal adipose tissue (VAT) and visceral epicardial adipose tissue (EAT). Plasma cardiometabolic risk profile was assessed for each subject (blood pressure, lipid profile, fasting glucose). Associations with markers of the cardiometabolic profile were stronger for VAT and EAT than for SAT. In multivariable regression analyses including all three adipose tissues and taking into account gender and age, only VAT maintained significant associations to systolic and diastolic blood pressure, and plasma low-density lipoprotein cholesterol, total/high-density lipoprotein cholesterol ratio, triglycerides and apolipoproteins B/A1 ratio. In an effort to identify the strongest office-based predictor of visceral adiposity in this young and apparently healthy young adult sample, we determined that while BMI, waist circumference (WC) and waist-to-hip ratio were all associated to VAT in univariable analyses (p<0.05 for all), only WC remained independently associated to VAT in multivariable analysis (p<0.001). Concurrently, WC was also an independent predictor of EAT in multivariable analysis (p<0.001). Because visceral adipose tissues - EAT, and to a greater extent VAT - are more strongly and widely associated with the cardiometabolic profile than is SAT, we believe that assessing visceral adiposity is relevant in young and apparently healthy adults. Beyond simply measuring BMI, the addition of WC measurement in young and apparently healthy adults improves the prediction of visceral adiposity.

Abstract 193: Contribution of Visceral and Epicardial Adipose Tissues to the Variation in the Cardiometabolic Risk of Apparently Healthy Young Adults

OBJECTIVE: Relative contributions of abdominal versus epicardial adipose tissues to the cardiometabolic profile of young and healthy adults are unknown. We investigated the associations between subcutaneous abdominal adipose tissue (SAT), visceral abdominal adipose tissue (VAT) and epicardial adipose tissue (EAT) with markers of the cardiometabolic profile in young and apparently healthy males and females. METHOD AND RESULTS: Two hundred and eighty young and apparently healthy subjects (48% (134 of 280) male; age 18 to 35 years; BMI &lt;30 kg/m2) underwent magnetic resonance imaging after voluntary recruitment in the community. We quantified SAT, VAT and EAT. Plasma cardiometabolic risk profile was assessed for each subject (blood pressure, lipid profile, fasting glucose). Associations with markers of the cardiometabolic profile were stronger for VAT and EAT than for SAT. In multivariable regression analyses including all three adipose tissues and taking into account gender and age, only VAT maintained significant associations to systolic and diastolic blood pressure, and plasma low-density lipoprotein cholesterol, total/high-density lipoprotein cholesterol ratio, triglycerides and apolipoproteins B/A1 ratio. In an effort to identify the strongest office-based predictor of visceral adiposity in this young and apparently healthy young adult sample, we determined that while BMI, waist circumference (WC) and waist-to-hip ratio were all associated to VAT in univariable analyses (p&lt;0.05 for all), only WC remained independently associated to VAT in multivariable analysis (p&lt;0.001). Concurrently, WC was also an independent predictor of EAT in multivariable analysis (p&lt;0.001). CONCLUSION - Because visceral adipose tissues - EAT, and to a greater extent VAT - are more strongly and widely associated with the cardiometabolic profile than is SAT, we believe that assessing visceral adiposity is relevant in young and apparently healthy adults. Beyond simply measuring BMI, the addition of WC measurement in young and apparently healthy adults improves the prediction of visceral adiposity.

Bipolar disorder ANK3 risk variant effect on sustained attention is replicated in a large healthy population

Independent genome-wide association studies have implicated a common single nucleotide polymorphism within the ANK3 gene (rs10994336) in bipolar disorder (BD) susceptibility, thus establishing rs10994336 marker as a strong candidate predisposing genetic factor for BD. Furthermore, recent findings demonstrate that this variant impacts on cognitive functioning in BD patients, their unaffected relatives, and healthy controls by influencing sustained attention. Here, we aimed to replicate this finding in a large population-based sample of healthy young adults (n=1808). Sustained attention was evaluated using the Continuous Performance Test as in the original study and working memory was assessed with the n-back task. Individuals carrying the BD risk T-allele showed significantly reduced sensitivity in target detection, increased errors of commission, and atypical response latency variability. In addition, we confirmed the lack of an association between the rs10994336 variant and working memory, as well as general intellectual ability, suggesting a specific effect on the Continuous Performance Test performance.

Reproducibility and criterion-related validity of the sit and reach test and toe touch test for estimating hamstring flexibility in recreationally active young adults

Objective1) to examine the test-retest reproducibility and criterion-related validity of the sit and reach test (SRT) and the toe touch test (TT) for estimating hamstring flexibility measured through the passive straight leg raise test (PSLR); and 2) to determine whether the SRT cut-off scores may be used for the TT test to identify participants in this sample of young healthy adults as having short hamstring flexibility. DesignTest-retest design. SettingControlled laboratory environment. Participants243 active recreationally young adults. Main outcome measuresParticipants performed the SRT, the TT test and PSLR twice in a randomized order with a 4-week interval between trials. Reproducibility was examined using typical percentage error (coefficient of variation [CV]) and intraclass correlation coefficient (ICC) as well as their respective confidence limits. Regression and Kappa correlation statistical analyses were performed to study the association of the SRT and TT test with the PSLR test and the 95% limits of agreement (LoA) between SRT and TT test were calculated to explore differences in the mean differences between these measurements. ResultsThe finding showed acceptable reproducibility measures for SRT (8.74% CV; 0.92 ICC), TT test (9.86% CV; 0.89 ICC) and PSLR (5.46% CV; 0.85 ICC). The SRT (R2 = 0.63) and TT test (R2 = 0.49) were significantly associated with PSLR. The 95% LoA between SRT and TT test reported systematic bias (2.84 cm) and wide 95% random error (±9.72 cm). ConclusionsReproducibility of SRT, TT test and PSLR is acceptable and the criterion-related validity of SRT and TT test is moderate. Furthermore, the SRT cut-off scores should not be used for TT test for the detection of short hamstring muscles.

Valutazione dell’efficacia di due dispositivi monouso per l’igiene orale

Objectives To assess the effectiveness of two disposable devices for personal dental hygiene. Materials and methods Experimental, randomized, controlled study of a sample of young healthy adults. The subjects were randomly assigned to a test or a control group. The former subjects used the disposable dental hygiene devices (a low-density polyethylene toothbrush and a polyurethane sponge swab), and the controls used their own traditional toothbrushes. Two calibrated operators calculated the plaque index as described by Dababneh (NMPS) and the gingival index using the Löe and Silness method (GI), at the beginning of the study (T0) and after 48 hours (T1). Results Compared with controls, the test group presented a significant increase in the plaque index at T1 among the users of disposable devices, that was smaller in those who used the toothbrush (tooth brush p-value ≤0.002 vs sponge swab p-value ≤0.001), in comparison with the control group (one-way ANOVA). Conclusions The use of a disposable toothbrush is better than using a disposable sponge swab.

Validity of the Smarthealth Watch to Measure Heart Rate During Rest and Exercise

The purpose of this study was to examine the validity of the Smarthealth watch (Salutron, Inc., Fremont, California, USA), a heart rate monitor that includes a wristwatch without an accompanying chest strap. Twenty-five individuals participated in 3-min periods of standing, 2.0 mph walking, 3.5 mph walking, 4.5 mph jogging, and 6.0 mph running. Heart rate was simultaneously measured and recorded at 60-sec intervals using three methods: the Smarthealth wristwatch, the Polar Vantage XL monitor with an accompanying chest strap (Kempele, Finland), and an electrocardiograph, which served as the criterion method. The heart rates obtained from the Smarthealth watch were highly correlated with those from the electrocardiograph (r ≥ .95) and the standard error of estimate was below 5 bpm for all measurements. Additionally, correlation coefficients and standard errors of estimate between the Smarthealth watch and Polar heart rate monitor were ≥.97 and <3.7 bpm, respectively. However, the Smarthealth watch exhibited a reduced ability to detect a heart rate during the 4.5 and 6.0 mph conditions compared to the Polar heart rate monitor (6% and 13.9% reduced ability, respectively). The Smarthealth watch appears to be a valid device for monitoring heart rate while standing and during treadmill exercise involving walking and jogging in a healthy young adult sample, although it may not be able to consistently detect a heart rate when body motion is excessive.

Cortisol Awakening Response and Hippocampal Volume: Vulnerability for Major Depressive Disorder?

Major depressive disorder is associated with dysregulated basal cortisol levels and small hippocampal (HC) volume. However, it is still debated whether these phenomena are a consequence of the illness or whether they may represent a vulnerability marker existing before the illness onset. Here, we aimed to examine this notion of vulnerability by assessing whether abnormalities in basal cortisol secretion and HC volumes are already present in a sample of healthy young adults who showed varying levels of depressive tendencies, but at subclinical levels. We recruited healthy young men and women from the local university. On the basis of depression scores derived from standard questionnaires, three groups were formed: a control group (n = 27), a subclinical group (n = 23), and a high-risk subclinical group (n = 9). The participants underwent a magnetic resonance imaging scan and collected saliva samples for the assessment of diurnal cortisol levels. Both the subclinical and the high-risk subclinical group failed to show a significant increase in cortisol levels after awakening. The high-risk subclinical group also showed a lower area-under-the-curve increase of cortisol levels after awakening compared with control subjects. In addition, this group also had smaller total HC volume compared with control subjects. The findings from this subclinical sample suggest that dysregulated cortisol awakening response and small HC volume may constitute vulnerability factors for major depressive disorder. Further investigations are needed to discern the mechanisms that may underlie these phenomena.

Increased cortisol awakening response and afternoon/evening cortisol output in healthy young adults with low early life parental care

Growing evidence from animal and human studies suggests a profound and long-lasting influence of early life experiences--ranging from variations in parenting behavior to severe adversity--on hypothalamic-pituitary-adrenal axis function. The aim of the current investigation was to examine the association between naturally occurring variations in early life parental care and the cortisol awakening response (CAR), afternoon/evening cortisol output and key psychological variables in a sample of healthy young adults. Fifty-eight (19 male and 39 female) participants between 18 and 30 years of age completed psychological questionnaires and collected saliva at awakening, 30 min thereafter and at 3 p.m., 6 p.m., and 9 p.m. on three non-consecutive weekdays. Participants with low (compared to high) parental care experiences exhibited an increased CAR, increased afternoon/evening cortisol output, decreased self-esteem, and increased depressive symptomatology and anxiety. We suggest that the elevated CAR and afternoon/evening cortisol levels might reflect a biological correlate of adversity-induced vulnerability for psychopathology. This study is first to show an association between the retrospective perception of early life parental care and cortisol circadian rhythms in healthy young adults.

Who Fails the Iowa Gambling Test (IGT)? Personality, Neuropsychological, and Near-Infrared Spectroscopy Findings in Healthy Young Controls

The Iowa gambling task (IGT) was designed to assess clinically relevant decision-making impairment, yet some studies find high rates of failure in otherwise healthy control groups. The current study examined variables potentially related to IGT failure, including negative affect, intellect, personality, and executive functioning, in a well-screened sample of healthy young adults. In addition, cerebral oxygenation (near-infrared spectroscopy) was assessed. Results indicated that those who failed the IGT had lower estimated intellect, made more commission errors on the 2-back task, and showed less bilateral dorsolateral prefrontal cortex oxygenation, relative to those who passed. Overall findings are consistent with prior literature suggesting that frontal lobe functioning is related to successful IGT performance and that executive functioning and working memory skills are important components of IGT performance, even in those without clinical disorders or evidence of "real world" dysfunction.

One-Year Delayed Recall Performance of the Rey-Osterrieth Complex Figure in a Healthy Young Adult Sample

This study investigated the performance of the very long-term delayed recall trial (1 year) of the Rey-Osterrieth Complex Figure Test (ROCF) in a healthy young adult sample. Forty-one healthy university students were given the delayed recall trial, one year after receiving the copy and the 3-minutes delayed recall trial of the ROCF. Although a significant decrease of the recall score was shown by comparison with the 3-minutes delayed recall trial, all the participants were able to draw a certain figure including the main features of the ROCF on the 1-year delayed recall trial.

Convergent Validity and Effect of Instruction Modification on the Groton Maze Learning Test: A New Measure of Spatial Working Memory and Error Monitoring

This study examined the convergent validity and effect of instruction modification on the Groton Maze Learning Test (GMLT), a computerized hidden maze learning test. Performance on the GMLT was compared to performance on widely used pencil-and-paper and computerized measures of working memory, route selection, and planning/problem solving in a sample of healthy young adults. Performance on GMLT outcome measures correlated with performance on comparator measures of working memory, route selection, and planning (r = 0.31–0.44). Instruction modification (withholding simple instructions) increased the number of rule-break errors on the GMLT (Cohen's d = 0.59). These results provide support for the convergent validity of the GMLT in assessing working memory, route selection, and planning/problem solving, and suggest that a simple instructional modification may yield a novel measure of executive function: feedback monitoring and procedural rule acquisition and application.

Cognition in healthy aging is related to regional white matter integrity, but not cortical thickness.

It is well established that healthy aging is accompanied by structural changes in many brain regions and functional decline in a number of cognitive domains. The goal of this study was to determine (1) whether the regional distribution of age-related brain changes is similar in gray matter (GM) and white matter (WM) regions, or whether these two tissue types are affected differently by aging, and (2) whether measures of cognitive performance are more closely linked to alterations in the cerebral cortex or in the underlying WM in older adults (OA). To address these questions, we collected high-resolution magnetic resonance imaging (MRI) data from a large sample of healthy young adults (YA; aged 18-28) and OA (aged 61-86 years). In addition, the OA completed a series of tasks selected to assess cognition in three domains: cognitive control, episodic memory, and semantic memory. Using advanced techniques for measuring cortical thickness and WM integrity, we found that healthy aging was accompanied by deterioration of both GM and WM, but with distinct patterns of change: Cortical thinning occurred primarily in primary sensory and motor cortices, whereas WM changes were localized to regions underlying association cortices. Further, in OA, we found a striking pattern of region-specific correlations between measures of cognitive performance and WM integrity, but not cortical thickness. Specifically, cognitive control correlated with integrity of frontal lobe WM, whereas episodic memory was related to integrity of temporal and parietal lobe WM. Thus, age-related impairments in specific cognitive capacities may arise from degenerative processes that affect the underlying connections of their respective neural networks.

Low wintertime vitamin D levels in a sample of healthy young adults of diverse ancestry living in the Toronto area: associations with vitamin D intake and skin pigmentation

BackgroundVitamin D plays a critical role in bone metabolism and many cellular and immunological processes. Recent research indicates that concentrations of serum 25-hydroxyvitamin D [25(OH)D], the main indicator of vitamin D status, should be in excess of 75 nmol/L. Low levels of 25(OH)D have been associated with several chronic and infectious diseases. Previous studies have reported that many otherwise healthy adults of European ancestry living in Canada have low vitamin D concentrations during the wintertime. However, those of non-European ancestry are at a higher risk of having low vitamin D levels. The main goal of this study was to examine the vitamin D status and vitamin D intake of young Canadian adults of diverse ancestry during the winter months.MethodsOne hundred and seven (107) healthy young adults self-reporting their ancestry were recruited for this study. Each participant was tested for serum 25(OH)D concentrations and related biochemistry, skin pigmentation indices and basic anthropometric measures. A seven-day food diary was used to assess their vitamin D intake. An ANOVA was used to test for significant differences in the variables among groups of different ancestry. Linear regression was employed to assess the impact of relevant variables on serum 25(OH)D concentrations.ResultsMore than 93% of the total sample had concentrations below 75 nmol/L. Almost three-quarters of the subjects had concentrations below 50 nmol/L. There were significant differences in serum 25(OH)D levels (p < 0.001) and vitamin D intake (p = 0.034) between population groups. Only the European group had a mean vitamin D intake exceeding the current Recommended Adequate Intake (RAI = 200 IU/day). Total vitamin D intake (from diet and supplements) was significantly associated with 25(OH)D levels (p < 0.001). Skin pigmentation, assessed by measuring skin melanin content, showed an inverse relationship with serum 25(OH)D (p = 0.033).ConclusionWe observe that low vitamin D levels are more prevalent in our sample of young healthy adults than previously reported, particularly amongst those of non-European ancestry. Major factors influencing 25(OH)D levels were vitamin D intake and skin pigmentation. These data suggest a need to increase vitamin D intake either through improved fortification and/or supplementation.

Gray matter correlates of fluid, crystallized, and spatial intelligence: Testing the P-FIT model

The parieto-frontal integration theory (P-FIT) nominates several areas distributed throughout the brain as relevant for intelligence. This theory was derived from previously published studies using a variety of both imaging methods and tests of cognitive ability. Here we test this theory in a new sample of young healthy adults ( N = 100) using a psychometric battery tapping fluid, crystallized, and spatial intelligence factors. High resolution structural MRI scans (3T) were obtained and analyzed with Voxel-based Morphometry (VBM). The main findings are consistent with the P-FIT, supporting the view that general intelligence ( g) involves multiple cortical areas throughout the brain. Key regions include the dorsolateral prefrontal cortex, Broca's and Wernicke's areas, the somato-sensory association cortex, and the visual association cortex. Further, estimates of crystallized and spatial intelligence with g statistically removed, still share several brain areas with general intelligence, but also show some degree of uniqueness.