Andrew Scholey

Glucose administration, heart rate and cognitive performance: effects of increasing mental effort

Abstract  Rationale: It is known that glucose administration is capable of improving performance on tests of declarative verbal memory and non-mnemonic tasks requiring high ”mental effort”. At the same time, cognitively demanding tasks are associated with elevated heart rate, a response that could feasibly be part of a physiological mechanism serving to increase the delivery of glucose to active brain substrates. Objective: The present placebo-controlled, double-blind, balanced, crossover study examined the interaction between glucose administration, cognitive performance and heart rate during three tasks of differing mental demand and somatically-matched control tasks. Methods: The effects of a glucose drinkon participants’ performance on two serial subtraction tasks (Serial Threes and Serial Sevens) and a Word Retrieval (Verbal Fluency) task were assessed. Heart rates were monitored throughout the experiment, and participants rated each task in terms of its perceived mental demand. Results: Serial Sevens was rated as the most mentally demanding task, followed by Word Retrieval, then Serial Threes. Glucose consumption significantly improved performance on Serial Sevens, with a trend for improved performance on Word Retrieval. Both Serial Sevens and Serial Threes were associated with significant heart rate elevation above that seen in somatically matched control tasks (ruling out the possibility that accelerated heart rate was due to peripheral mechanisms alone). Unexpectedly, participants in the glucose condition had higher heart rates during cognitive processing. Additionally, individuals whose baseline heart rates were below the median performed better on Serial Threes and Serial Sevens. Conclusion: We suggest that supplemental glucose preferentially targets tasks with a relatively high cognitive load, which itself (through unknown mechanisms) mobilises physiological reserves as part of a natural response to such tasks. Furthermore, baseline heart rate and responses to cognitive demand and glucose administration may represent important physiological individual differences.

Chewing gum selectively improves aspects of memory in healthy volunteers.

CognitiveDrugResearchLtd.,ReadingRG301EA,UKMany people chew gum partly due to the belief that itincreases aspects of mental performance, including concen-tration. To the best of our knowledge no empirical evidenceexists to support this contention. The present experiment,therefore, examined the effects of chewing gum using acomprehensive and sensitive cognitive assessment batteryand two tasks manipulating cognitive load. Heart rateresponses were also measured.Seventy-five healthy adult participants (mean age 246years) were randomly assigned to one of three experimentalconditions (N‹25 per group): ‘‘chewing’’ – a piece of sugar-free chewing gum (Wrigley’s Extra Spearmint) was chewednaturally and constantly throughout the procedure; ‘‘shamchewing’’ – participants mimicked chewing movements in theabsence of gum; ‘‘quiet control’’ – no chewing behaviour wasperformed.Aspects of attention, working memory and long-termmemory were assessed using the Cognitive Drug Research(CDR) computerised battery. Stimuli were presented on acolour monitor and, except for two written word recall tasks,responses were collected automatically using a ‘‘Yes’’/‘‘No’’responsemodule.Thetaskswerepresentedintheorder:Wordpresentation, Immediate Word Recall, Picture Presentation,SimpleReactionTime,DigitVigilance,ChoiceReactionTime,Spatial Working Memory, Numeric Working Memory,Delayed Word Recall, Word Recognition and PictureRecognition (for details, e.g. see Kennedy et al. 2000).Following the CDR battery, participants performed compu-terised Serial Subtractions tasks. These assess concentrationand working memory and allow manipulation of cognitiveload (see Scholey et al., 2001 for details). In the present studySerialThrees(involvingtherepeatedsubtractionofthreefroma randomly generated starting number using the computer’snumerickeypad)thenSerialSevens(subtractionofseven)wereused, each for 2min.Eachcognitive taskoutcome measurewasanalysedby one-wayanalysisofvariance,withDunnettcomparisonstoisolatebetween-group effects where appropriate. The most strikingfindingwasasignificanteffectonbothimmediateanddelayedword recall, with more words being recalled in the chewingconditioncomparedwiththequietcontrolcondition(Table1).The Spatial Working Memory sensitivity index and Numericworkingmemoryreactiontimeweresimilarlyimprovedinthechewingcondition,andalsointheshamchewingconditionforthe latter measure (which reflects the efficiency of workingmemory operations). In addition, simple reaction times wereslowerintheshamchewingconditionthaninthequietcontrolcondition.Baseline heart rate recordings (sampled at 30-s intervals)began 240s prior to treatment and continued during a 180-speriod of chewing, sham chewing or sitting quietly prior tocognitive assessment (which lasted about 30min in all). Heartrate (mean bpm) was calculated during baseline, treatment,each of the 10 CDR tasks and both Serial Subtraction tasks.Heart rate changes relative to baseline were subjected to a3(Condition) 14(Phase) factorial ANOVA with repeatedmeasures on the latter factor. The main effect of conditionapproached significance, F(2,936)‹30, p‹006; heart ratesweresignificantlyhigherinthechewingconditionthaninquietcontrols, p<005 (Fig. 1). There was also a significant maineffect oftask,F(13,936)‹130,p<001:with theexceptionofSimple Reaction Time and Delayed Word Recall, all taskphasesofthestudywereassociatedwithsignificantincreasesinheart rate. There was also a significant task conditioninteraction, F(26,936)‹256, p<001.Theseresultsprovidedthefirstevidencethatthechewingofgum can improve episodic memory (involving the learning,storage and retrieval of information) and working memory(where information is held ‘‘on line’’). They did not indicatethat gum-chewing improves aspects of attention, at least asmeasured here.The impaired Simple Reaction Time during sham chewingmay reflect diversion of attentional resources during initialstages of performing this unfamiliar behaviour. This is con-sistent with the elevated heart rate observed while shamchewing in earlierphases of the experiment (Fig. 1). Althoughanactivecontrolisimportant,shamchewingmaynotbeidealfor this purpose, because most cognitive scores (except, nota-E-mail: a.scholey@unn.ac.uk bly, Numeric Working Memory Reaction Time) in this group0195–6663/02/

Attenuation of laboratory-induced stress in humans after acute administration of Melissa officinalis (Lemon Balm).

– see front matter # 2002 Elsevier Science Ltd. All rights reserved.

A low glycaemic index breakfast cereal preferentially prevents children's cognitive performance from declining throughout the morning

Objective: Melissa officinalis (lemon balm) is contemporaneously used as a mild sedative and/or calming agent. Although recent research has demonstrated modulation of mood in keeping with these roles, no studies to date have directly investigated the effects of this herbal medication on laboratory-induced psychological stress. Methods: In this double-blind, placebo-controlled, randomized, balanced crossover experiment, 18 healthy volunteers received two separate single doses of a standardized M. officinalis extract (300 mg, 600 mg) and a placebo, on separate days separated by a 7-day washout period. Modulation of mood was assessed during predose and 1-hour postdose completions of a 20-minute version of the Defined Intensity Stressor Simulation (DISS) battery. Cognitive performance on the four concurrent tasks of the battery was also assessed. Results: The results showed that the 600-mg dose of Melissa ameliorated the negative mood effects of the DISS, with significantly increased self-ratings of calmness and reduced self-ratings of alertness. In addition, a significant increase in the speed of mathematical processing, with no reduction in accuracy, was observed after ingestion of the 300-mg dose. Conclusion: These results suggest that the potential for M. officinalis to mitigate the effects of stress deserves further investigation.

Salvia lavandulaefolia (Spanish Sage) enhances memory in healthy young volunteers

This study investigated whether the glycaemic index (GI) of breakfast cereal differentially affects childrens attention and memory. Using a balanced cross-over design, on two consecutive mornings 64 children aged 6-11 years were given a high GI cereal and a low GI cereal in a counterbalanced order. They performed a series of computerised tests of attention and memory, once prior to breakfast and three times following breakfast at hourly intervals. The results indicate that childrens performance declines throughout the morning and that this decline can be significantly reduced following the intake of a low GI cereal as compared with a high GI cereal on measures of accuracy of attention (M=-6.742 and -13.510, respectively, p<0.05) and secondary memory (M=-30.675 and -47.183, respectively, p<0.05).

Modulation of cognition and mood following administration of single doses of Ginkgo biloba, ginseng, and a ginkgo/ginseng combination to healthy young adults

Sage (Salvia) has a longstanding reputation in British herbal encyclopaedias as an agent that enhances memory, although there is little evidence regarding the efficacy of sage from systematized trials. Based on known pharmacokinetic and binding properties, it was hypothesised that acute administration of sage would enhance memory in young adult volunteers. Two experiments utilised a placebo-controlled, double-blind, balanced, crossover methodology. In Trial 1, 20 participants received 50, 100 and 150 microl of a standardised essential oil extract of Salvia lavandulaefolia and placebo. In Trial 2, 24 participants received 25 and 50 microl of a standardised essential oil extract of S. lavandulaefolia and placebo. Doses were separated by a 7-day washout period with treatment order determined by Latin squares. Assessment was undertaken using the Cognitive Drug Research computerised test battery prior to treatment and 1, 2.5, 4 and 6 h thereafter. The primary outcome measures were immediate and delayed word recall. The 50 microl dose of Salvia essential oil significantly improved immediate word recall in both studies. These results represent the first systematic evidence that Salvia is capable of acute modulation of cognition in healthy young adults.

Dose dependent changes in cognitive performance and mood following acute administration of Ginseng to healthy young volunteers

It has previously been demonstrated in separate studies that single doses of Ginkgo biloba, Panax ginseng, and a combination of the two extracts can improve different aspects of cognitive performance in healthy young volunteers. The present study directly compared the effects of single doses of G. biloba, ginseng, and a product combining the two on aspects of mood and cognitive performance in the same cohort of healthy, young adult volunteers. The study followed a randomised placebo-controlled, double-blind, balanced, cross-over design. Twenty participants received 360 mg of ginkgo, 400 mg of ginseng, 960 mg of a product combining the two extracts, and a matching placebo. Treatment order was dictated by random allocation to a Latin square, with a 7-day wash-out period between treatments. Cognitive testing comprised completion of the Cognitive Drug Research (CDR) computerised assessment battery and two serial subtraction mental arithmetic tasks. Mood was assessed with Bond-Lader visual analogue scales. Following a baseline cognitive assessment, further test sessions took place 1, 2.5, 4, and 6 h after the days treatment was taken. The results largely supported previous findings. All three treatments were associated with improved secondary memory performance on the CDR battery, with the ginseng condition evincing some improvement in the speed of performing memory tasks and in the accuracy of attentional tasks. Following ginkgo and the ginkgo/ginseng combination performance of both the Serial Threes and Serial Sevens, subtraction tasks was also improved at the later testing sessions. No modulation of the speed of performing attention tasks was evident. Improvements in self-rated mood was also found following ginkgo and to a lesser extent the combination product.

Single doses of Panax ginseng (G115) reduce blood glucose levels and improve cognitive performance during sustained mental activity

Recent evidence suggests that chronic administration of Ginseng can improve cognitive performance in animals and in humans. No previous study has examined the possibility of cognitive effects following single doses of Ginseng in healthy adults. The present study investigated whether acute administration of Ginseng (G115, Pharmaton SA) had any consistent effect on mood and four aspects of cognitive performance (“Quality of Memory”, “Speed of Memory”, “Quality of Attention” and “Speed of Attention”) that can be derived by factor analysis of the Cognitive Drug Research computerised assessment battery. The study followed a placebo-controlled, double-blind, balanced, crossover design. Twenty healthy young adult volunteers received 200,400, and 600 mg of G115, and a matching placebo, in counterbalanced order, with a 7 day wash-out period between treatments. Following a baseline cognitive assessment, further test sessions took place 1, 2.5, 4 and 6h after the days treatment The most striking result was a significant improvement in “Quality of Memory” and the associated “Secondary Memory” factor at all time points following 400 mg of Ginseng. Both the 200 and 600 mg doses were associated with a significant decrement of the “Speed of Attention” factor at later testing times only. Subjective ratings of alertness were also reduced 6h following the two lowest doses. To the best of our knowledge this represents the first demonstration of a modulation of mood and cognitive performance by acute administration of Ginseng.

Oxygen administration selectively enhances cognitive performance in healthy young adults: a placebo-controlled double-blind crossover study

Single doses of the traditional herbal treatment Panax ginseng have recently been shown to elicit cognitive improvements in healthy young volunteers. The mechanisms by which ginseng improves cognitive performance are not known. However, they may be related to the glycaemic properties of some Panax species. Using a double-blind, placebo-controlled, balanced crossover design, 30 healthy young adults completed a 10min test battery at baseline, and then six times in immediate succession commencing 60min after the day’s treatment (placebo, 200mg G115 or 400mg G115). The 10 min battery comprised a Serial Threes subtraction task (2min); a Serial Sevens task (2min); a Rapid Visual Information Processing task (5min); then a ‘mental fatigue’ visual analogue scale. Blood glucose was measured prior to each day’s treatment, and before, during and after the post-dose completions of the battery. Both the 200mg and 400mg treatments led to significant reductions in blood glucose levels at all three post-treatment measurements (p 0.005 in all cases). The most notable behavioural effects were associated with 200mg of ginseng and included significantly improved Serial Sevens subtraction task performance and significantly reduced subjective mental fatigue throughout all (with the exception of one time point in each case) of the post-dose completions of the 10min battery (p 0.05). Overall these data suggest that Panax ginseng can improve performance and subjective feelings of mental fatigue during sustained mental activity. This effect may be related to the acute gluco-regulatory properties of the extract.

Effects of Panax ginseng, consumed with and without glucose, on blood glucose levels and cognitive performance during sustained ‘mentally demanding’ tasks

Abstract It was recently demonstrated that oxygen administration can improve performance on a simple word recall task in healthy young adults. This study was aimed at determining the impact of various durations of oxygen administration on a wider range of cognitive measures. This was achieved using the Cognitive Drug Research computerised test battery, and employing a double-blind, placebo-controlled crossover design. Over a period of 7 weeks, 20 participants were trained and subsequently assessed on the test battery under several durations of oxygen inhalation; air administered in an identical fashion served as a control. The results provided support for our earlier work in that increases were found in both immediate and delayed word recall. In addition, oxygen administration significantly improved performance on several measures of attention and vigilance. Simple reaction time, choice reaction time, digit vigilance reaction time and picture recognition reaction time were improved in a manner which depended on the duration of oxygen inspired. With the exception of word recall, no significant improvements were found for any measure of accuracy, nor were word recognition, digit memory scanning, or spatial memory improved. These results are discussed in the context of stages of information processing and are consistent with the hypothesis that cognitive performance is “fuel-limited” and can be differentially augmented by increasing the availability of the brain’s metabolic resources.