***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 
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    Input: The present study investigated the extent of expectancy in the ability of glucose to affect cognitive performance . Using a within-subjects design , subjects ( n 26 ) completed four experimental sessions ( in counterbalanced order and after an initial practice session ) during which they were given a 500 ml drink 30 min prior to completing a cognitive assessment battery . In addition , all subjects completed a baseline practice session during which they were given no drink . During two of the sessions , subjects were given a drink containing 50 g glucose and on the other two they were given a drink containing aspartame . A balanced placebo design was used , such that for half the sessions subjects were accurately informed as to the content of the drink ( glucose or aspartame ) , whereas in the other two sessions they were misinformed as to the content of the drink . The task battery comprised a 6 min visual analogue of the  Bakan vigilance task  , an immediate verbal free-recall task , an immediate verbal recognition memory task and a measure of motor speed ( two-finger tapping ) . Blood glucose and self-reported mood were also recorded at several time points during each session . Glucose administration was found to improve recognition memory times , in direct contrast to previous findings in the literature . Glucose administration also improved performance on the Bakan task ( relative to the control drink ) , but only in sessions where subjects were informed that they would receive glucose and not when they were told that they would receive aspartame . There were no effects either of the nature of the drink or expectancy on the other measures . These results are interpreted in terms of there being some contribution of expectancy concerning the positive effects of glucose on cognition in studies which have not used an equi-sweet dose of aspartame as a control drink The long-term physiological effects of refined carbohydrates on appetite and mood remain unclear . Reported effects when subjects are not blind may be due to expectations and have rarely been studied for more than 24 h. The present study compared the effects of supplementary soft drinks added to the diet over 4 weeks on dietary intake , mood and BMI in normal-weight women ( n 133 ) . Subjects were categorised as ' watchers ' or ' non-watchers ' of what they ate then received sucrose or artificially sweetened drinks ( 4 x 250 ml per d ) . Expectancies were varied by labelling drinks ' sugar ' or ' diet ' in a counter-balanced design . Sucrose supplements provided 1800 kJ per d and sweetener supplements provided 67 kJ per d. Food intake was measured with a 7 d diary and mood with ten single Likert scales . By 4 weeks , sucrose supplements significantly reduced total carbohydrate intake ( F(1,129 ) = 53.81 ; P<0.001 ) , fat ( F(2,250 ) = 33.33 ; P<0.001 ) and protein intake ( F(2,250 ) = 28.04 ; P<0 - 001 ) compared with sweetener supplements .  Mean daily energy intake increased by just under 1000 kJ compared with baseline ( t ( 67 df ) = 3.82 ; P < 0.001 ) and was associated with a non-significant trend for those receiving sucrose to gain weight . There were no effects on appetite or mood . Neither dietary restraint status as measured by the Dutch Eating Behaviour Question naire nor the expectancy procedure had effects . Expectancies influenced mood only during baseline week . It is concluded that sucrose satiates , rather than stimulates , appetite or negative mood in normal-weight subjects During education and early career , young adults often face examinations and assessment centers . Coffee and energy drinks are convenient and commonly used to enhance or maintain performance in these situations . Whether these macronutrients improve performance in a dem and ing and drawn-out multi-task situation is not clear . Using double-blind , placebo-controlled studies , we set out to examine the effects of caffeine and glucose in an assessment center-like situation , under natural consumption conditions , in a group of young adults who were heterogeneous with respect to consumption patterns . We measured multi-task performance including logical thinking , processing speed , numeric and verbal memory , attention and the ability to concentrate , and mood over a two-hour period . Caffeine and glucose were administered in common beverages with appropriate placebo controls allowing the assessment of psychological effects of expectancy . Importantly , and in contrast to most previous studies , participants retained their habitual caffeine and sugar intake ( studies 1 and 2 ) as this represents common behavior . Based on the bulk of literature , we hypothesized that ( i ) caffeine enhances attentional performance and mood , while performance in more complex tasks will remain unchanged , and that ( ii ) glucose enhances performance on memory tasks accompanied with negative mood . Our results provide evidence that neither caffeine nor glucose significantly influence cognitive performance when compared with placebo , water , or no treatment controls in a multi-task setting . Yet , caffeine and , by trend , placebo improve dispositions such that participants perceive preserved mental energy throughout the test procedure . These subjective effects were stronger after 24 h caffeine abstinence ( study 3 ) . Future studies will have to address whether these mood changes actually result in increased motivation during a challenging task Rationale The cognition-enhancing effects of glucose administration  to humans have been well-documented ; however , it remains unclear whether this effect preferentially targets episodic memory or other cognitive domains . Objectives The effect of glucose on the allocation of attentional re sources during memory encoding was assessed using a sensitive dual-attention paradigm . Material s and methods One hundred and twenty volunteers ( mean age 21.60 , SD 4.89 , 77 females ) took part in this r and omised , double-blind , placebo-controlled , parallel groups study where each consumed a 25-g glucose drink or a placebo . Half of the participants in each drink condition attempted to track a moving on-screen target during auditory word presentation . The distance between the cursor and the tracking target was used as an index of attentional cost during encoding . Effects of drink and tracking on recognition memory and drink on tracking performance were assessed . Self-rated appetite and mood were co-monitored . Results Co-performing the tracking task significantly impaired memory performance irrespective of drink condition . In the placebo – tracking condition , there was a cost to tracking manifest as greater deviation from target during and immediately following word presentation . Compared with placebo , the glucose drink significantly improved tracking performance during encoding . There were significant time-related changes in thirst and alertness ratings but these were not differentially affected by drink or tracking conditions . Conclusion Tracking but not memory was enhanced by glucose . This finding suggests that , under certain task conditions , glucose administrations does not preferentially enhance memory performance . One mechanism through which glucose acts as a cognition enhancer is through allowing greater allocation of attentional re sources A series of three studies examined the influence of  glucose drinks  and increasing blood glucose levels  on  mood .  Experiment one considered the short-term effect of a glucose containing drink on mood in young adults : a glucose drink in the morning and higher blood glucose levels were both associated with feeling less tense . Higher blood glucose was also correlated with greater self-reported energy . In the second experiment high blood glucose levels were sustained for 2 hr by repeatedly taking a glucose containing drink . Again higher blood glucose levels were associated with reports of less tension . In a final study subjects were placed in a frustrating situation . The consumption of a glucose drink result ed in fewer negative responses , following a negative statement from the experimenter , in subjects who had fasted over-night . It was concluded that higher blood glucose levels are associated with feeling less tense In this study we determined the short-term effects of a glucose drink and a sucrose drink compared to a placebo on cognitive performance and mood in elderly people with subjective , mild memory complaints using a r and omized crossover study design . In total , 43 nondiabetic older adults with self-reported memory complaints were included .  Drinks consisted of 250 ml with dissolved glucose ( 50 g ) , sucrose ( 100 g ) , or a mixture of artificial sweeteners ( placebo ) .  Multiple neuropsychological tests were performed and were combined by means of z scores into four cognitive domains : episodic memory , working memory , attention and information ( processing speed ) , and executive functioning . Mood was assessed with the short Profile of Mood Status ( s-POMS ) question naire . Blood glucose concentrations were measured at five time points to divide participants into those with a better or poorer blood glucose recovery . Performance on the domain of attention and information processing speed was significantly better after consuming the sucrose drink ( domain score of 0.06 , SD = 0.91 ) than after the placebo drink ( –0.08 , SD = 0.92 , p = .04 ) . Sucrose had no effect on the other three domains , and glucose had no effect on any of the domains compared to the placebo . When dividing participants into poorer or better glucose recoverers , the beneficial effect of sucrose on attention and information processing speed was only seen in participants with a poorer recovery . After sucrose consumption , depressive feelings and tension were slightly higher than after the placebo . To conclude , 100 g sucrose , but not 50 g glucose , optimized attention and information processing speed in the short term in this study in elderly people with subjective , mild memory complaints The role of carbohydrates on mood and cognition is fairly well established , however research examining the behavioural effects of the other macronutrients is limited . The current study compared the effects of a 25 g glucose drink to energetically matched protein and fat drinks and an inert placebo . Following a blind , placebo-controlled , r and omised crossover design , 18 healthy young adults consumed drinks containing fat , glucose , protein and placebo .  Cognitive performance was examined at baseline and again 15- and 60 min post drink . Mood was assessed at baseline and then 10- , 35- and 80 min post drink . Attention and speed were enhanced 15 min following fat or glucose ingestion and working memory was enhanced 15 min following protein ingestion . Sixty minutes post drink memory enhancements were observed after protein and memory impairment was observed following glucose . All drinks increased ratings of alertness . The findings suggest that macronutrients : ( i ) have different windows of opportunity for effects ( ii ) target different cognitive domains Previous studies have found a small association between the level of blood glucose  and subjective reports of energy in those sitting quietly . Given reports that both memory and attention are influenced by the level of blood glucose it was hypothesised that under conditions of cognitive dem and there would be a stronger association between mood and blood glucose levels . In three studies , with three cognitive tasks , the Stroop Task , Rapid Information Processing Task , and a difficult test of h and -eye coordination , falling blood glucose was associated with feeling less energetic The effects of a sucrose drink ( 160 kcals/40 grams of cane sugar ) on mood state ( Profile of Mood States ) were examined over time in a between-subjects , blind placebo design . Orosensory factors were virtually eliminated due to the prior use of a benzocaine anaesthetic lozenge . The ingestion of sucrose failed to have any substantial effect on mood immediately after intake or 30 and 60 min thereafter , although two female subjects reported an increase in energy at 30 min . There was no evidence that the carbohydrate preload increased hunger or eating , rather a delay in food intake was noted subsequent to the ingestion of sugar which was not found following ingestion of saccharin or water The long-term effects of sucrose on appetite and mood remain unclear . Normal weight subjects compensate for sucrose added blind to the diet ( Reid et al. , 2007 ) . Overweight subjects , however , may differ . In a single-blind , between-subjects design , soft drinks ( 4x25cl per day ; 1800kJ sucrose sweetened versus 67kJ aspartame sweetened ) were added to the diet of overweight women ( n=53 , BMI 25 - 30 , age 20 - 55 ) for 4 weeks . A 7-day food diary gave measures of total energy , carbohydrate , protein , fat , and micronutrients . Mood and hunger were measured by ten single Likert scales rated daily at 11.00 , 14.00 , 16.00 , and 20.00 . Activity levels were measured by diary and pedometer . Baseline energy intake did not differ between groups . During the first week of the intervention energy intake increased slightly in the sucrose group , but not in the aspartame group , then decreased again , so by the final week intake again did not differ from the aspartame group . Compensation was not large enough to produce significant changes in the composition of the voluntary diet . There were no effects on hunger or mood . It is concluded that overweight women do not respond adversely to sucrose added blind to the diet , but compensate for it by reducing voluntary energy intake . Alternative explanations for the correlation between sugary soft drink intake and weight gain are discussed 
    Output:
    
Conclusions The results from this review show limited effects of glucose ingestion on mood and no effect of sucrose on mood