***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: Sustained attention abnormality in schizophrenia is usually refractory to available treatment . Nicotine can transiently improve sustained attention in schizophrenia patients , although its neural mechanisms are unknown . Underst and ing the neural basis of this effect may lead to new treatment strategies for this cognitive deficit . Twenty schizophrenia patients and 24 healthy comparison smokers participated in a double-blind , placebo-controlled , crossover , r and omized functional magnetic resonance imaging study comparing nicotine vs placebo patch on sustained attention , using the rapid visual information-processing task . Schizophrenia patients had impaired visual sustained attention accuracy and processing speed ( all P 's < .001 ) and showed significantly reduced activation in the frontal-parietal-cingulate-thalamic attention network compared with healthy comparison subjects . Nicotine administration enhanced accuracy and processing speed compared with placebo ( all P 's ≤.006 ) , with no drug × diagnosis interactions . However , schizophrenia patients ' task performance remained impaired during the nicotine condition , even when compared with healthy comparison subjects in the placebo condition ( all P 's ≤.01 ) . Nicotine exerted no significant reversal of the impaired attention network associated with schizophrenia . Activations in brain regions associated with nicotine-induced behavioral improvement were not significantly different between patients and comparison subjects . Thus , nicotine transiently enhanced sustained attention similarly in schizophrenia patients and in healthy comparison smokers . The neural mechanisms for this nicotinic effect in schizophrenia appear similar to those for healthy comparison subjects . However , nicotine , at least in a single sustained dose , does not normalize impaired sustained attention and its associated brain network in schizophrenia . These findings provide guidance for developing new treatment strategies for the sustained attention deficit in schizophrenia The goal of this study was to assess whether degree of information processing load differentially affects vigilance performance in patients with schizophrenia as compared to normal controls or patients with other attentional disorders . We contrasted the performance of clinical ly stable out patients with schizophrenia ( n = 18 ) , with that of normal controls ( n = 17 ) , and adults with developmental attentional/learning disorders ( n = 13 ) on simple and dem and ing versions of a visual continuous performance test ( CPT ) . Patients with schizophrenia were significantly impaired on both versions of the  CPT  compared to normal controls , and showed a significant decline in perceptual sensitivity and significantly more omission errors with increased processing dem and s. Compared to adults with developmental attentional/learning disorders , patients with schizophrenia manifested a tendency toward a decline in perceptual sensitivity . There were no significant differences between groups on a measure of response bias . The data support the hypothesis that patients with schizophrenia have insufficient information processing re sources to cope with higher processing dem and s on effortful attention tasks . Further study comparing schizophrenic patients with patients who have other neuropsychiatric disorders , controlling for severity of illness , is required to determine the specificity of this deficit in schizophrenia BACKGROUND Tobacco smoking , driven by the addictive properties of nicotine , is the most prevalent preventable cause of death in the Western world . Accumulated evidence suggests that nicotine may increase appetitive responding for nondrug incentives in the environment . METHODS To test this hypothesis , we conducted a r and omized , double-blind , placebo-controlled , crossover study of the effect of a single dose of transdermal nicotine on reward responsiveness in 30 psychiatrically healthy nonsmokers . A novel signal detection task in which correct responses were differentially rewarded in a 3:1 ratio was used to assess the extent to which participants modulated their behavior as a function of reward . RESULTS Despite expected adverse effects such as nausea , nicotine significantly increased response bias toward the more frequently rewarded condition , at the expense of accuracy , independent of effects on attention or overall vigilance . Additionally , response bias on placebo was greater in participants who received nicotine in the first session , indicating that an effect of nicotine on reward responsiveness or reward-based learning persisted for at least 1 week . CONCLUSIONS These findings suggest that a single dose of nicotine enhances response to non-drug-related rewards in the environment , with lasting effects . This effect may contribute to reinforcement of early smoking behavior and development of nicotine dependence Although continuous performance tasks ( CPTs ) are becoming more common in psychiatric research , it remains unclear which performance measures best differentiate psychiatric patient groups and along which psychological dimensions . To address this the authors examined sustained attention decrements in patients with bipolar disorder and schizophrenia using CPT measures of perceptual sensitivity , response bias , and psychomotor processing speed . Patients with bipolar disorder with psychotic features ( N=20 ) , schizophrenia ( N=20 ) , and healthy controls ( N=20 ) were evaluated using structured clinical interviews . These patients were rated with the Scale for the Assessment of Positive Symptoms and the Young Mania Rating Scale before completing a de grade d-stimulus version of the CPT .  Psychomotor processing speed was the only measure that reliably differentiated the groups across the entire vigilance period and was the strongest predictor of group membership . These findings suggest that reaction time measures may be sensitive to differences in the sustained attention abilities of patients with bipolar disorder and schizophrenia . By incorporating reaction time measures into CPT assessment s , discriminant ability may be enhanced Abstract The Continuous Performance Test ( CPT ) is a widely used procedure for sustained attention/vigilance measurement . However , though the key index of vigilance impairment is the decrement of sensitivity over time during the test period , only few studies have examined whether schizophrenics show a larger drop in CPT performance than do healthy controls . 48 schizophrenic in patients and 48 controls were investigated with the Munich CPT ( 480 visual stimuli , 25 % target stimuli , one stimulus per second ) . Stimuli were de grade d by r and omly inverting 40 % , 41 % , 42 % , or 43 % of the pixels . Results were calculated separately for three consecutive trial sections . Additionally , PANSS ratings , medication , and other clinical data were documented . Schizophrenics show a vigilance decrement over time , controls show a vigilance increase . Differential vigilance changes were not related to the level of stimulus degradation . Schizophrenics  performed worse than controls only at the lowest degradation level . While overall sensitivity correlated negatively with the dose of atypical neuroleptics and benzodiazepines , vigilance shifts over time correlated negatively with the dose of typical neuroleptics . Furthermore , sensitivity was related to the cognitive PANSS syndrome , number of admissions/ duration of illness . Differential sensitivity decrements of schizophrenics and controls can be shown if suited CPT procedures are used . The need for basic research on experimental conditions of the CPT as well as examination of the relationship between sustained attention/vigilance decrements and clinical features of schizophrenia is suggested Introduction . Although deficits in executive functioning in schizophrenia have been consistently reported , their precise relationship to symptomatology remains unclear . Recent approaches to executive functioning in nonschizophrenia studies have aim ed to “ fractionate ” the individual cognitive processes involved . In this study , we hypothesised that if these processes are fractionable , then particular symptom syndromes may be selectively related to executive deficits . In particular , it was hoped that this approach could clarify whether negative and positive symptoms of schizophrenia are differentially related to particular aspects of executive/attentional functions . Methods . A total of 32 patients with schizophrenia and 16 matched controls were assessed on a series of tasks design ed to tap the theoretically derived executive functions of Inhibition , Shifting set , Working memory , and Sustained attention . Results . Negative symptoms were significantly predicted by performance on an  “ Inhibition ” task ( Stroop ) , and not by performance on any other task . Furthermore , for a subgroup of patients with predominantly negative symptoms variance in positive symptoms was only significantly predicted by performance on a  set-shifting task ( Visual Elevator ) , and not by performance on other tasks , including inhibition .  Conclusions . Our results support the contention that negative symptoms can , at least partly , be conceived of as cognitive behaviours expressing specific executive deficits . Specifically , we discuss the possibility that negative symptoms may , in part , express a failure in response monitoring . We further suggest that the disordered metacognition result ing in positive symptoms may be mediated by cognitive flexibility in patients with a predominantly negative symptom profile Perceptual sensitivity to a visual target presented in a r and om continuous sequence of targets and nontargets decreased rapidly over time when stimuli were highly de grade d visually but not when moderately de grade d or unde grade d. Large declines in sensitivity , independent of changes in response criterion , were found after only 5 minutes of observation . These rapid decrements of sensitivity to de grade d targets seem to result from dem and s on the limited capacity of visual attention Substantial gains have been made on the neurobiology of attention from systems neuroscience work in animal models and human cognitive neuroscience . However , the integration of rodent-based research on the specific neurotransmitter systems that subserve attention with the results from human behavioral and neuroimaging studies has been hampered by the lack of tasks that validly assess attention in both species . To address this issue , an operant sustained attention task that has been extensively used in research on the neurobiology of attention in rats was re design ed and vali date d for use in humans . Although humans showed better performance overall , the two species showed similar effects of several attention-related variables , including the introduction of distractor-related challenge . This task provides a useful tool for integrative , cross-species research and may help to determine how specific neurotransmitter systems contribute to the hemodynamic changes observed in human functional neuroimaging experiments Nicotine enhances attentional functions . Since chronic nicotine exposure through smoking induces neuroadaptive changes in the brain at a structural and molecular level , the present functional MRI ( fMRI ) study aim ed at investigating the neural mechanisms underlying visuospatial and sustained attention in smokers and non-smokers . Visuospatial attention was assessed with a location-cueing paradigm , while sustained attention was measured by changes in response speed over time . During invalid trials , neural activity within the basal forebrain was selectively enhanced in smokers and higher basal forebrain activity was associated with increased parietal cortex activation . Moreover , higher levels of expired carbon monoxide in smokers before scanning were associated with higher parietal cortex activation and faster responses to invalidly cued targets . Smokers showed a slowing of responses and additionally recruited an area within the right supramarginal gyrus with increasing time on task . Activity decreases over time were observed in visual areas in smokers . The data provide evidence for altered attentional functions in smokers as compared with non-smokers , which were partly modulated by residual nicotine levels and were observed at a behavioural level for sustained and at a neural level for spatial and sustained attention 
    Output:
    
Two types of assessment lead to opposite findings ; they do not evaluate sustained attention the same way .
Studies using overall assessment s of sustained attention ability tend to reveal a deficit , whereas studies using over time assessment s do not .