***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: The present study explores the relation among 4 personality traits associated with impulsive behavior and alcohol abuse . Personality traits were measured using the 4 subscales of the UPPS Impulsive Behavior Scale ( UPPS ; S. P. Whiteside & D. R. Lynam , 2001 ) . The UPPS and measures of psychopathology  were administered to clinical sample s of alcohol abusers high in antisocial personality traits ( AAPD ) , alcohol abusers low in antisocial personality traits ( AA ) , and a control group ( total N = 60 ) . Separate analyses of variance indicated that AAPDs had significant elevations on all 4 UPPS scales , whereas the AAs and controls differed only on the Urgency subscale . However , when controlling for psychopathology , group differences on the UPPS scales disappeared . The results suggest that personality traits related to impulsive behavior are not directly related to alcohol abuse but rather are associated with the elevated levels of psychopathology found in a subtype of alcohol abusers Although the ability to perform complex cognitive operations is assumed to be impaired following acute marijuana smoking , complex cognitive performance after acute marijuana use has not been adequately assessed under experimental conditions . In the present study , we used a within-participant double-blind design to evaluate the effects acute marijuana smoking on complex cognitive performance in experienced marijuana smokers . Eighteen healthy research volunteers ( 8 females , 10 males ) , averaging 24 marijuana cigarettes per week , completed this three-session outpatient study ; sessions were separated by at least 72-hrs . During sessions , participants completed baseline computerized cognitive tasks , smoked a single marijuana cigarette ( 0 % , 1.8 % , or 3.9 % Δ9-THC w/w ) , and completed additional cognitive tasks . Blood pressure , heart rate , and subjective effects were also assessed throughout sessions . Marijuana cigarettes were administered in a double-blind fashion and the sequence of Δ9-THC concentration order was balanced across participants . Although marijuana significantly increased the number of premature responses and the time participants required to complete several tasks , it had no effect on accuracy on measures of cognitive flexibility , mental calculation , and reasoning . Additionally , heart rate and several subjective-effect ratings ( e.g. , “ Good Drug Effect , ” “ High , ” “ Mellow ” ) were significantly increased in a Δ9-THC concentration-dependent manner . These data demonstrate that acute marijuana smoking produced minimal effects on complex cognitive task performance in experienced marijuana users Event-related fMRI was used to investigate the hypothesis that neural activity involved in response inhibition depends upon the nature of the response being inhibited . Two different Go/No-go tasks were compared-one with a high working memory load and one with low . The ' simple ' Go/No-go task with low working memory load required subjects to push a button in response to green spaceships but not red spaceships . A ' counting ' Go/No-go task ( high working memory load ) required subjects to respond to green spaceships as well as to those red spaceships preceded by an even number of green spaceships . In both tasks , stimuli were presented every 1.5 s with a 5:1 ratio of green-to-red spaceships . fMRI group data for each task were analyzed using r and om effects models to determine signal change patterns associated with Go events and No-go events ( corrected P < or = 0.05 ) . For both tasks , Go responses were associated with signal change in the left primary sensorimotor cortex , supplementary motor area ( SMA ) proper , and anterior cerebellum ( right > left ) . For the simple task , No-go events were associated with activation in the pre-SMA ; the working memory-loaded ' counting ' task elicited additional No-go activation in the right dorsolateral prefrontal cortex . The findings suggest that neural contributions to response inhibition may be task dependent ; the pre-SMA appears necessary for inhibition of unwanted movements , while the dorsolateral prefrontal cortex is recruited for tasks involving increased working memory load Persistent dose-related cognitive decrements have been reported in 28-day abstinent heavy marijuana ( MJ ) users . However , the neural substrates of these decrements in cognitive performance are not known . This study aim ed to determine if 25-day abstinent MJ users show persistent dose-related alterations in performance and brain activity using PET H(2)(15)O during the Iowa Gambling Task-IGT ( a decision-making task ) . Eleven heavy MJ users and 11 non-drug users participated . The MJ group resided in an inpatient research unit at the NIH/NIDA-IRP for 25 days prior to testing to ensure abstinence . A dose-related association was found between increased MJ use and lower IGT performance and alterations in brain activity . The MJ group showed greater activation in the left cerebellum and less activation in the right lateral orbitofrontal cortex ( OFC ) and the right dorsolateral prefrontal cortex ( DLPFC ) than the Control group . When the MJ group was divided into Moderate ( 8 - 35 joints/week ) and Heavy users ( 53 - 84 joints/week ) , the Heavy MJ group showed less activation in the left medial OFC and greater activation in the left cerebellum than the Moderate group . However , brain activity and task performance were similar between the Moderate MJ users and the Control group , suggesting a " threshold effect " . These preliminary findings indicate that very heavy users of MJ have persistent decision-making deficits and alterations in brain activity . Specifically , the Heavy MJ users may focus on only the immediate reinforcing aspects of a situation ( i.e. , getting high ) while ignoring the negative consequences . Thus , faulty decision-making could make an individual more prone to addictive behavior and more resistant to treatment . Finally , it is unclear if these neurologic findings will become progressively worse with continued heavy MJ use or if they will resolve with abstinence from MJ use Rationale Δ9-Tetrahydrocannabinol ( THC ) is the main active constituent of cannabis . In recent years , the average THC content of some cannabis cigarettes has increased up to approximately 60 mg per cigarette ( 20 % THC cigarettes ) . Acute cognitive and psychomotor effects of THC among recreational users after smoking cannabis cigarettes containing such high doses are unknown . Objectives The objective of this study was to study the dose – effect relationship between the THC dose contained in cannabis cigarettes and cognitive and psychomotor effects for THC doses up to 69.4 mg ( 23 % ) . Material s and methods This double-blind , placebo-controlled , r and omised , four-way cross-over study included 24 non-daily male cannabis users ( two to nine cannabis cigarettes per month ) . Participants smoked four cannabis cigarettes containing 0 , 29.3 , 49.1 and 69.4 mg THC on four exposure days . Results The THC dose in smoked cannabis was linearly associated with a slower response time in all tasks ( simple reaction time , visuo-spatial selective attention , sustained attention , divided attention and short-term memory tasks ) and motor control impairment in the motor control task . The number of errors increased significantly with increasing doses in the short-term memory and the sustained attention tasks . Some participants showed no impairment in motor control even at THC serum concentrations higher than 40 ng/mL. High feeling and drowsiness differed significantly between treatments . Conclusions Response time slowed down and motor control worsened , both linearly , with increasing THC doses . Consequently , cannabis with high THC concentrations may be a concern for public health and safety if cannabis smokers are unable to titrate to a high feeling corresponding to a desired plasma THC level Cannabis sativa , the most widely used illicit drug , has profound effects on levels of anxiety in animals and humans . Although recent studies have helped provide a better underst and ing of the neurofunctional correlates of these effects , indicating the involvement of the amygdala and cingulate cortex , their reciprocal influence is still mostly unknown . In this study dynamic causal modelling ( DCM ) and Bayesian model selection ( BMS ) were used to explore the effects of pure compounds of C. sativa [ 600 mg of cannabidiol ( CBD ) and 10 mg Delta 9-tetrahydrocannabinol ( Delta 9-THC ) ] on prefrontal-subcortical effective connectivity in 15 healthy subjects who underwent a double-blind r and omized , placebo-controlled fMRI paradigm while viewing faces which elicited different levels of anxiety . In the placebo condition , BMS identified a model with driving inputs entering via the anterior cingulate and forward intrinsic connectivity between the amygdala and the anterior cingulate as the best fit . CBD but not Delta 9-THC disrupted forward connectivity between these regions during the neural response to fearful faces . This is the first study to show that the disruption of prefrontal-subocritical connectivity by CBD may represent neurophysiological correlates of its anxiolytic properties CONTEXT Cannabis use can both increase and reduce anxiety in humans . The neurophysiological substrates of these effects are unknown . OBJECTIVE To investigate the effects of 2 main psychoactive constituents of Cannabis sativa ( Delta9-tetrahydrocannabinol [ Delta9-THC ] and cannabidiol [ CBD ] ) on regional brain function during emotional processing . DESIGN Subjects were studied on 3 separate occasions using an event-related functional magnetic resonance imaging paradigm while viewing faces that implicitly elicited different levels of anxiety . Each scanning session was preceded by the ingestion of either 10 mg of Delta9-THC , 600 mg of CBD , or a placebo in a double-blind , r and omized , placebo-controlled design . PARTICIPANTS Fifteen healthy , English-native , right-h and ed men who had used cannabis 15 times or less in their life . MAIN OUTCOME MEASURES Regional brain activation ( blood oxygenation level-dependent response ) , electrodermal activity ( skin conductance response [ SCR ] ) , and objective and subjective ratings of anxiety . RESULTS Delta9-Tetrahydrocannabinol increased anxiety , as well as levels of intoxication , sedation , and psychotic symptoms , whereas there was a trend for a reduction in anxiety following administration of CBD . The number of SCR fluctuations during the processing of intensely fearful faces increased following administration of Delta9-THC but decreased following administration of CBD . Cannabidiol attenuated the blood oxygenation level-dependent signal in the amygdala and the anterior and posterior cingulate cortex while subjects were processing intensely fearful faces , and its suppression of the amygdalar and anterior cingulate responses was correlated with the concurrent reduction in SCR fluctuations . Delta9-Tetrahydrocannabinol mainly modulated activation in frontal and parietal areas . CONCLUSIONS Delta9-Tetrahydrocannabinol and CBD had clearly distinct effects on the neural , electrodermal , and symptomatic response to fearful faces . The effects of CBD on activation in limbic and paralimbic regions may contribute to its ability to reduce autonomic arousal and subjective anxiety , whereas the anxiogenic effects of Delta9-THC may be related to effects in other brain regions Background Marijuana intoxication appears to impair response inhibition , but it is unclear if impaired inhibition and associated brain abnormalities persist after prolonged abstinence among adolescent users . We hypothesized that brain activation during a go/no-go task would show persistent abnormalities in adolescent marijuana users after 28 days of abstinence . Methods Adolescents with ( n = 16 ) and without ( n = 17 ) histories of marijuana use were compared on blood oxygen level dependent ( BOLD ) response to a go/no-go task during functional magnetic resonance imaging ( fMRI ) after 28 days of monitored abstinence .  Participants had no neurological problems or Axis I diagnoses other than cannabis abuse/dependence . Results Marijuana users did not differ from non-users on task performance but showed more BOLD response than non-users during inhibition trials in right dorsolateral prefrontal , bilateral medial frontal , bilateral inferior and superior parietal lobules , and right occipital gyri , as well as during “ go ” trials in right prefrontal , insular , and parietal cortices ( p < 0.05 , clusters > 943 μl ) . Differences remained significant even after controlling for lifetime and recent alcohol use . Conclusions Adolescent marijuana users relative to non-users showed increased brain processing effort during an inhibition task in the presence of similar task performance , even after 28 days of abstinence . Thus , increased brain processing effort to achieve inhibition may pre date the onset of regular use or result from it . Future investigations will need to determine whether increased brain processing effort is associated with risk to use This individual differences study examined the separability of three often postulated executive functions-mental set shifting ( " Shifting " ) , information updating and monitoring ( " Updating " ) , and inhibition of prepotent responses ("Inhibition")- and their roles in complex " frontal lobe " or " executive " tasks . One hundred thirty-seven college students performed a set of relatively simple experimental tasks that are considered to predominantly tap each target executive function as well as a set of frequently used executive tasks : the Wisconsin Card Sorting Test ( WCST ) , Tower of Hanoi ( TOH ) , r and om number generation ( RNG ) , operation span , and dual tasking .  Confirmatory factor analysis indicated that the three target executive functions are moderately correlated with one another , but are clearly separable . Moreover , structural equation modeling suggested that the three functions contribute differentially to performance on complex executive tasks . Specifically , WCST performance was related most strongly to Shifting , TOH to Inhibition , RNG to Inhibition and Updating , and 
    Output:
    
Functional imaging studies of impulsivity studies suggest that prefrontal blood flow is lower in chronic cannabis users than in controls .
Studies of acute administration of THC or marijuana report increased brain metabolism in several brain regions during impulsivity tasks .
Structural imaging studies of cannabis users found differences in reduced prefrontal volumes and white matter integrity that might mediate the abnormal impulsivity and mood observed in marijuana users .