Exercise Dependency and Overuse Injuries in Attention Deficit Hyperactivity Disorder.

ABSTRACT: Attention deficit hyperactivity disorder (ADHD) is a common condition, but current medications have limitations, pushing a drive for alternative approaches. Different exercise-focused approaches have shown promise, but concern has also been raised about individuals with ADHD showing greater risk of addiction, including exercise dependency. Using an online survey, we examined current exercise practices, including exercise dependency and the presence of overuse injury, which could result from overexercising, in 114 adults with ADHD. We found that most were regularly exercising. None were classified as exercise dependent, but 38.9% were deemed symptomatic nondependent. Hyperactive-impulsive symptoms were a predictor of the level of exercise withdrawal experienced, and the co-occurrence of autism spectrum disorder was associated with greater risk of overuse injuries. The data indicate that ADHD may confer some greater risk of exercise dependency, aligning with previous studies investigating other addictions and suggesting further research is critical.

Sign-tracking and goal-tracking in humans: Utilising eye-tracking in clinical and non-clinical populations.

BACKGROUND: In Pavlovian conditioning, learned behaviour varies according to the perceived value of environmental cues. For goal-trackers (GT), the cue merely predicts a reward, whilst for sign-trackers (ST), the cue holds incentive value. The sign-tracking/goal-tracking model is well-validated in animals, but translational work is lacking. Despite the model's relevance to several conditions, including attention deficit hyperactivity disorder (ADHD), we are unaware of any studies that have examined the model in clinical populations. METHODS: The current study used an eye-tracking Pavlovian conditioning paradigm to identify ST and GT in non-clinical (N = 54) and ADHD (N = 57) participants. Eye movements were recorded whilst performing the task. Dwell time was measured for two areas of interest: sign (i.e., cue) and goal (i.e., reward), and an eye-gaze index (EGI) was computed based on the dwell time sign-to-goal ratio. Higher EGI values indicate sign-tracking behaviour. ST and GT were determined using median and tertiary split approaches in both samples. RESULTS: Despite greater propensity for sign-tracking in those with ADHD, there was no significant difference between groups. The oculomotor conditioned response was reward-specific (CS+) and present, at least partly, from the start of the task indicating dispositional and learned components. There were no differences in externalising behaviours between ST and GT for either sample. CONCLUSIONS: Sign-tracking is associated with CS+ trials only. There may be both dispositional and learned components to sign-tracking, potentially more common in those with ADHD. This holds translational potential for understanding individual differences in reward-learning.

The effects of tryptophan loading on Attention Deficit Hyperactivity in adults: A remote double blind randomised controlled trial.

BACKGROUND: Despite the impact and prevalence of Attention Deficit Hyperactivity Disorder (ADHD), current treatment options remain limited and there is a drive for alternative approaches, including those building on evidence of a role for tryptophan (TRP) and serotonin (5-HT). This study aimed to evaluate the effect of acute TRP loading on attention and impulsivity in adults with ADHD. TRIAL DESIGN AND METHODS: We conducted a remote double blind randomised controlled trial (RCT) using TRP loading to examine the effects of a balanced amino acid load in comparison to low and high TRP loading in individuals with ADHD (medicated, N = 48, and unmedicated, N = 46) and controls (N = 50). Participants were randomised into one of three TRP treatment groups using stratified randomisation considering participant group and gender using a 1:1:1 ratio. Baseline testing of attention and impulsivity using the Test of Variables of Attention Task, Delay Discounting Task, and Iowa Gambling Task was followed by consumption of a protein drink (BAL, LOW, or HIGH TRP) before repeated testing. RESULTS AND CONCLUSIONS: No effects of TRP were observed for any of the measures. In the present study, TRP loading did not impact on any measure of attention or impulsivity in those with ADHD or Controls. The findings need to be confirmed in another trial with a larger number of patients that also considers additional measures of dietary protein, plasma TRP and aggression. (Registration ID ISRCTN15119603).

The Effects of Different Exercise Approaches on Attention Deficit Hyperactivity Disorder in Adults: A Randomised Controlled Trial.

Attention deficit hyperactivity disorder (ADHD) results in significant functional impairment. Current treatments, particularly for adults, are limited. Previous research indicates that exercise may offer an alternative approach to managing ADHD, but research into different types of exercise and adult populations is limited. The aim of this study was to examine the effects of acute exercise (aerobic cycling vs mind-body yoga exercises) on symptoms of ADHD in adults. Adults with ADHD (N = 82) and controls (N = 77) were randomly allocated to 10 min of aerobic (cycling) or mind-body (Hatha yoga) exercise. Immediately before and after exercise, participants completed the Test of Variables of Attention task, Delay Discounting Task, and Iowa Gambling Task to measure attention and impulsivity. Actigraphy measured movement frequency and intensity. Both groups showed improved temporal impulsivity post-exercise, with cycling beneficial to all, whilst yoga only benefited those with ADHD. There were no effects of exercise on attention, cognitive or motor impulsivity, or movement in those with ADHD. Exercise reduced attention and increased movement in controls. Exercise can improve temporal impulsivity in adult ADHD but did not improve other symptoms and worsened some aspects of performance in controls. Exercise interventions should be further investigated.

Hybrid flexible (HyFlex) teaching and learning: climbing the mountain of implementation challenges for synchronous online and face-to-face seminars during a pandemic.

In 2020, King's College London introduced HyFlex teaching as a means to supplement online and face-to-face teaching and to respond to Covid-19 restrictions. This enabled teaching to a mixed cohort of students (both online and on campus). This article provides an outline of how such an approach was conceptualized and implemented in a higher-education institution during an intense three-month period over that summer and prior to the limited re-opening of the university campus. This was a new approach that offers a number of pointers for reflection and provides key insights in on this novel learning environment and the physical and pedagogical contexts in which learning can occur. Technical implementation factors are detailed, along with both reflections on challenges and solutions. Pedagogical issues such as cognitive load, social presence, and resolving the issues of a cohort spread across two locations are discussed. While we should be mindful of the limitations of this relatively-specific research, and shouldn't therefore over-extrapolate our findings, one key finding is that delivering Hyflex is associated with a higher cognitive load. Further, the audio quality of our implementation enhanced the feeling of presence in the learning environment. We recommend providing appropriate technical and pedagogical training, as well as audio-visual and digital education support.

Effects of captions, transcripts and reminders on learning and perceptions of lecture capture.

Lecture capture is popular within Higher Education, but previous research suggests that students do not always optimally select content to review, nor do they make the most of specific functions. In the current study conducted in the 2019/20 academic year, we used a repeated-measures crossover design to establish the effects of transcripts with closed captioning, and email reminders, on use (self-reported and system analytics), perceptions of lecture capture and student performance, as measured by multiple-choice question (MCQ) tests designed to assess the module learning outcomes. System analytics (N = 129) and survey data (N = 42) were collected from students alongside qualitative data from semi-structured interviews (N = 8). We found that students value lecture capture highly, but do not access it extensively during the teaching period. The availability of transcripts and closed captions did not impact the amount of capture use or performance on MCQ tests, but did result in more positive perceptions of capture, including increased likelihood of recommending it to others. The use of email reminders referring students to specific segments of capture and reminding them of the functionality had no impact on any measure, although qualitative data suggested that the content of reminders may be used in revision rather than during the teaching period, which fell outside the period we investigated. Collectively, these data suggest that the use of captions and transcripts may be beneficial to students by allowing dual processing of visual and audio content, and a searchable resource to help consolidate their learning but there is little evidence to support reminders. Supplementary Information: The online version contains supplementary material available at 10.1186/s41239-022-00327-9.

Understanding the relationship between safety beliefs and knowledge for cognitive enhancers in UK university students.

BACKGROUND: Cognitive enhancers (CE) are prescription drugs taken, either without a prescription or at a dose exceeding that which is prescribed, to improve cognitive functions such as concentration, vigilance or memory. Previous research suggests that users believe the drugs to be safer than non-users and that they have sufficient knowledge to judge safety. However, to date no research has compared the information sources used and safety knowledge of users and non-users. OBJECTIVES: This study compared users and non-users of CE in terms of i) their sources of knowledge about the safety of CE and ii) the accuracy of their knowledge of possible adverse effects of a typical cognitive enhancer (modafinil); and iii) how the accuracy of knowledge relates to their safety beliefs. METHODS: Students (N = 148) from King's College London (UK) completed an anonymous online survey assessing safety beliefs, sources of knowledge and knowledge of the safety of modafinil; and indicated whether they used CE, and, if so, which drug(s). RESULTS: The belief that the drugs are safe was greater in users than non-users. However, both groups used comparable information sources and have similar, relatively poor drug safety knowledge. Furthermore, despite users more strongly believing in the safety of CE there was no relationship between their beliefs and knowledge, in contrast to non-users who did show correlations between beliefs and knowledge. CONCLUSION: These data suggest that the differences in safety beliefs about CE between users and non-users do not stem from use of different information sources or more accurate safety knowledge.

Learning Approaches and Attitudes Toward Cognitive Enhancers in UK University Students.

The use of cognitive enhancers is gaining attention. Studies indicate that the theory of planned behavior (TPB) can model their use, with attitudes a key variable. However, the factors affecting attitude have been largely neglected. The aim of this study was to examine the relationship between learning approaches and individual competitiveness and attitudes toward cognitive enhancers in students. UK university students (N = 179) completed an anonymous online survey assessing their attitudes toward cognitive enhancers as well as competitiveness and learning approaches using the revised Study Process Questionnaire. Academic performance data were also collected. The analysis revealed that being competitive or having surface motives (i.e. wishing to work sufficiently to meet minimum requirements only) was predictive of a more positive attitude toward the drugs, whilst academic performance was a negative predictor. This research adds to previous work by demonstrating the importance of individual, rather than just institutional, competitiveness and identifying a role for learning approaches. Both offer avenues to target drug use because cooperation rather than competitiveness and deep rather than surface learning approaches can be driven from careful design of teaching and learning. This suggests that curriculum design could impact on attitudes toward cognitive enhancers, which in turn may alter the use of these drugs.

Why Educational Neuroscience Needs Educational and School Psychology to Effectively Translate Neuroscience to Educational Practice.

The emerging discipline of educational neuroscience stands at a crossroads between those who see great promise in integrating neuroscience and education and those who see the disciplinary divide as insurmountable. However, such tension is at least partly due to the hitherto predominance of philosophy and theory over the establishment of concrete mechanisms and agents of change. If educational neuroscience is to move forward and emerge as a distinct discipline in its own right, the traditional boundaries and methods must be bridged, and an infrastructure must be in place that allows for collaborative and productive exchange. In the present paper, we argue that school psychologists have the potential to fulfill this need and represent important agents of change in establishing better connections between research and practice. More specifically, we use the National Association of School Psychologists (NASP) (2020) Domains of Practice to highlight several areas where school psychology can actively support forging connections between neuroscience and educational practice. School psychologists represent untapped potential in their knowledge, skillset, and placement to serve a vital role in building the bridge between neuroscience and education.

Modelling predictors of UK undergraduates' attitudes towards smart drugs.

BACKGROUND: Smart drug use is increasing but we have little insight into their use. We hypothesized that use is predicted by attitudes and various factors including incremental morality and entity intelligence beliefs would be associated with positive attitudes, whilst perception of unfairness would be associated with negative attitudes. METHODS: UK undergraduates completed an online survey to establish attitudes towards smart drugs, previous use and likely future use as well as measures of several factors hypothesized to predict attitudes. RESULTS: Attitudes were found to predict previous and likely future use. Attitudes were more positive in those who believed that smart drugs were harmless and those who felt they knew enough to use them safely. By contrast, perceived unfairness was associated with negative attitudes. CONCLUSIONS: Interventions to reduce smart drug use should focus on attitudinal beliefs around potential harm and safety, as well as emphasizing the debate around unfairness.

An Investigation Into Response Inhibition in Distinct Clinical Groups Within Obsessive-Compulsive Disorder.

OBJECTIVE: Response inhibition has been frequently studied in obsessive-compulsive disorder (OCD) with mixed results. The inconsistent findings may stem in part from failure to consider the heterogeneity of the disorder. METHODS: The authors examined behavioral and event-related potential (ERP) components (N2 and P3) during a simple response inhibition go/nogo task in a sample of patients with OCD (N=48) and control subjects (N=53). Comparisons in behavioral and electrophysiological measures were made between groups (OCD compared with control) and within the OCD group in terms of symptom clusters (symmetry, forbidden thoughts, and cleaning) and comorbidity status (OCD only and OCD with depression). RESULTS: In the OCD group, the N2 component appeared more frontally localized compared with the control group. Participants with OCD demonstrated longer N2 latency and a larger difference in N2 between the nogo and go conditions, suggesting slower but greater conflict monitoring. P3 had a larger amplitude in the OCD group compared with the control group, indicative of greater response inhibition, but was also reduced in the nogo compared with go condition, suggesting suppressed response inhibition. No significant differences were found between symptom clusters, but patients with OCD only made more omission errors compared with patients with OCD and comorbid depression. The latter cohort also had faster P3 latencies, which, combined with the behavioral data, indicates slightly improved response inhibition when comorbid depression is found. CONCLUSIONS: On the basis of these results, it would seem unlikely that symptom clusters have contributed to previous inconsistencies in the literature. Comorbid depression, which may have affected previous results, should be considered in future research.

Chronic amphetamine enhances visual input to and suppresses visual output from the superior colliculus in withdrawal.

Heightened distractibility is a core symptom of Attention Deficit Hyperactivity Disorder (ADHD). Effective treatment is normally with chronic orally administered psychostimulants including amphetamine. Treatment prevents worsening of symptoms but the site of therapeutic processes, and their nature, is unknown. Mounting evidence suggests that the superior colliculus (SC) is a key substrate in distractibility and a therapeutic target, so we assessed whether therapeutically-relevant changes are induced in this structure by chronic oral amphetamine. We hypothesized that amphetamine would alter visual responses and morphological measures. Six-week old healthy male rats were treated with oral amphetamine (2, 5 or 10 mg/kg) or a vehicle for one month after which local field potential and multiunit recordings were made from the superficial layers of the SC in response to whole-field light flashes in withdrawal. Rapid Golgi staining was also used to assess dendritic spines, and synaptophysin staining was used to assess synaptic integrity. Chronic amphetamine increased local field potential responses at higher doses, and increased synaptophysin expression, suggesting enhanced visual input involving presynaptic remodelling. No comparable increases in multiunit activity were found suggesting amphetamine suppresses collicular output activity, counterbalancing the increased input. We also report, for the first time, five different dendritic spine types in the superficial layers and show these to be unaffected by amphetamine, indicating that suppression does not involve gross postsynaptic structural alterations. In conclusion, we suggest that amphetamine produces changes at the collicular level that potentially stabilise the structure and may prevent the worsening of symptoms in disorders like ADHD.

Repeated intermittent oral amphetamine administration results in locomotor tolerance not sensitization.

BACKGROUND: The phenomenon of locomotor sensitization to injected amphetamine is well-characterised. The increased locomotor activity found acutely is enhanced with repeated intermittent treatment. This effect arises due to hypersensitization of the dopaminergic system and is linked to drug addiction. A clinical population exposed to chronic repeated intermittent amphetamine treatment, such as is found for attention deficit hyperactivity disorder (ADHD), may be expected to be more at risk of addiction following this treatment. However, evidence suggests the opposite may be true. This suggests the route of administration may determine the direction of effects. AIMS AND METHODS: We aimed to establish how an oral amphetamine treatment regimen, similar to that used in ADHD, impacts on locomotor activity, specifically whether tolerance or sensitization would arise. Healthy hooded Lister rats were given amphetamine (2 mg/kg, 5 mg/kg and 10 mg/kg) or a vehicle solution once daily for 4 weeks with a 5 day on, 2 day off schedule. Locomotor activity was measured on the first day of treatment to establish the acute effects and on the final day of treatment to examine the chronic effects. RESULTS: As expected, acute doses of amphetamine increased locomotor activity, although this only reached statistical significance for the 5 mg/kg and 10 mg/kg doses. By contrast, after chronic treatment, animals administered these doses showed reduced activity indicating drug tolerance rather than sensitization had occurred. CONCLUSION: We suggest that the route of administration used in ADHD, which results in more stable and longer duration drug levels in the blood, results in tolerance rather than sensitization and that this effect could explain the reduced likelihood of substance addiction in those treated with psychostimulants for ADHD.

Chronic amphetamine treatment affects collicular-dependent behaviour.

Distractibility can be defined as an attention deficit where orientation toward irrelevant targets cannot be inhibited. There is now mounting evidence that the superior colliculus is a key neural correlate of distractibility, with increased collicular-activity resulting in heightened distractibility. Heightened distractibility is reduced by amphetamine, which acutely suppresses collicular responsiveness. However, when amphetamine is used to treat distractibility, it is given chronically, yet no data exist on whether chronic amphetamine treatment affects the colliculus. Here, the effect of chronic amphetamine treatment was assessed in healthy hooded lister rats on two collicular dependent behaviours following a twenty-eight day treatment period: i) orienting to visual stimuli, and ii) height-dependent modulation of air-righting. We found no significant impact of amphetamine treatment on visual orienting despite showing dose-dependent decreases in orienting to repeated stimuli. However, we did find that treatment with amphetamine significantly reduced the ability to modulate righting according to the height the animal is dropped from - a function known to be dependent on the colliculus. We suggest that the results are in line with previous research showing acute amphetamine suppresses collicular activity and we speculate that the psychostimulant may increase receptive field size, altering time-to-impact calculations carried out by the colliculus during air-righting.

Instrumental conditioning for food reinforcement in the spontaneously hypertensive rat model of attention deficit hyperactivity disorder.

BACKGROUND: The spontaneously hypertensive rat is thought to show good validity as a model of attention deficit hyperactivity disorder, in part because of impaired delayed reinforcement behaviour, corresponding to the dynamic developmental theory of the disorder. However, some previous studies may have been confounded use of fluid reward. Therefore, the objective of this study was to assess the spontaneously hypertensive rat and two comparison strains (Wistar and Wistar Kyoto) using a non-delayed food reinforcement paradigm in an attempt to advance knowledge of basic learnt behaviour in this strain, without potentially confounding reward sensitivity, which could impact on motivation to learn. Rats were trained on a fixed ratio 1 two choice discrimination schedule, extinction, reacquisition and reversal. We also tested non-reinforced spontaneous alternation to facilitate data interpretation. RESULTS: The spontaneously hypertensive rat displayed slower shaping and reduced on task activity during task acquisition, contrasting with previous results which indicate either enhanced responding and an impairment only when a delay is used; we suggest several reasons for this. In line with previous work, the same strain exhibited poor extinguishing of behaviour but were not impaired to the same extent on reversal of the discrimination. Finally, non-reinforced alternations on a Y-maze were also reduced in the spontaneously hypertensive rat. CONCLUSIONS: In sum, the spontaneously hypertensive rat appear to show poor response inhibition in reinforced and non-reinforced contexts. However, impaired response inhibition was reduced during reversal when an opposite response produced food reward alongside presentation of the conditioned stimulus. We discuss the possibility of enhanced attribution of incentive salience to cues in this strain and highlight several points of caution for researchers conducting behavioural assessments using the spontaneously hypertensive rat and their associated comparison strains.

Auditory responses in a rodent model of Attention Deficit Hyperactivity Disorder.

A central component of Attention Deficit Hyperactivity Disorder (ADHD) is increased distractibility in response to visual and auditory stimuli, which is linked to the superior colliculus (SC). Furthermore, there is now mounting evidence of altered collicular functioning in ADHD and it is proposed that a hyper-responsive SC could mediate symptoms of ADHD, including distractibility. In the present study we conducted a systematic characterisation of the intermediate and deep layers of the SC in the most commonly used and well-validated model of ADHD, the spontaneously hypertensive rat (SHR), building on prior work showing increased distractible behaviour in this strain using visual distractors. We examined collicular-dependent orienting behaviour, local field potential (LFP) and multiunit activity (MUA) in response to auditory stimuli in the anaesthetised rat, and morphological measures, in the SHR in comparison to the Wistar Kyoto (WKY) and Wistar (WIS). We found no evidence of increased distractibility in the behavioural data but suggest that this may arise due to cochlear hearing loss in the SHR. Furthermore, the electrophysiology data indicate that the SC in the SHR may still be hyper-responsive, normalising the amplitude of auditory responses that would otherwise be reduced due to the hearing impairment. The morphological measures of collicular volume, cell density and ratios did not indicate this potential hyper-responsiveness had a basis at the structural level examined. These findings have implications for future use of the SHR in auditory processing studies and may represent a limitation to the validity of this animal model.

Fast quantitative determination of methylphenidate levels in rat plasma and brain ex vivo by MALDI-MS/MS.

This study presents a simple and sensitive high-throughput matrix-assisted laser desorption/ionization time-of-flight tandem mass spectrometry (MALDI-MS/MS) method for ex vivo quantification of methylphenidate (MPH) in rat plasma and brain. The common MALDI matrix alpha-cyano-4-hydroxycinnamic acid was used to obtain an optimal dried droplet preparation. For method validation, standards diluted in plasma and brain homogenate prepared from untreated (control) rats were used. MPH was quantified within a concentration range of 0.1-40 ng/ml in plasma and 0.4-40 ng/ml in brain homogenate with an excellent linearity (R2 ≥ 0.9997) and good precision. The intra-day and inter-day accuracies fulfilled the FDA's ±15/20 critera. The recovery of MPH ranged from 93.8 to 98.5% and 87.2 to 99.8% in plasma and homogenate, respectively. We show that MPH is successfully quantified in plasma and brain homogenate of rats pre-treated with this drug using the internal standard calibration method. By means of this method, a linear correlation between plasma and brain concentration of MPH in rodents pre-treated with MPH was detected. The simple sample preparation based on liquid-liquid extraction and MALDI-MS/MS measurement requires approximately 10 s per sample, and this significantly reduces analysis time compared with other analytical methods. To the best of our knowledge, this is the first MALDI-MS/MS method for quantification of MPH in rat plasma and brain. Copyright © 2015 John Wiley & Sons, Ltd.

Using the five-choice serial reaction time task to examine the effects of atomoxetine and methylphenidate in the male spontaneously hypertensive rat.

Attention deficit hyperactivity disorder (ADHD) is the most common neurodevelopmental disorder and is normally treated with either stimulant or non-stimulant medication such as methylphenidate and atomoxetine respectively. The impact of these drugs on attention and impulsivity has been explored extensively in healthy animals but there is little research into their effects in an animal model of ADHD. In the present study we investigated the effects of both drugs on the spontaneously hypertensive rat (SHR) model of ADHD using the five-choice serial reaction time task (5CSRTT). We found a number of difficulties associated with training this vulnerable strain on such a complex task. However, where rats were able to learn the task we found very small effects of methylphenidate; increased incorrect responding and therefore decreased accuracy, a marker of attention at a single dose. There were no significant effects of atomoxetine on accuracy once multiple comparisons were taken into consideration. We found no effects of either drug on premature responding, a marker of impulsivity. These results indicate that the 5CSRTT may not be most sensitive to the impulsivity displayed in the SHR. Furthermore, they suggest that the SHR may lack predictive validity and further investigation is needed to optimise use of this model.

The effects of methylphenidate on cognitive performance of healthy male rats.

WE AIMED TO INVESTIGATE THE EFFECTS OF METHYLPHENIDATE (MPH) IN HEALTHY RATS ON TWO DISTINCT RADIAL MAZE TASKS WHICH RELY ON BRAIN STRUCTURES AND NEUROTRANSMITTERS KNOWN TO BE AFFECTED BY MPH: the Random Foraging Non-Delay Task (RFNDT) and the Delayed Spatial Win Shift Task (DSWT). Hooded Lister rats were trained to complete either the RFNDT or the DSWT having received oral treatment of either a vehicle or MPH (3.0 mg/kg and 5.0 mg/kg for RFNDT, 3.0 mg/kg for DSWT). We found no effect of MPH on the RFNDT relative to the control group. However, those treated with 5.0 mg/kg MPH did take significantly longer to reach criterion performance than those treated with the 3.0 mg/kg MPH, suggesting some doses of MPH can have detrimental effects. For the DSWT, if MPH was present in both phases, performance did not differ from when it was absent in both phases. However, when present in only one phase there was an increase in errors made, although this only reached significance for when MPH was present only in the test-phase. These data suggest that MPH may have detrimental effects on task performance and can result in state-dependent effects in healthy individuals.

Appetitive and consummative responding for liquid sucrose in the spontaneously hypertensive rat model of attention deficit hyperactivity disorder.

The spontaneously hypertensive rat (SHR) is one proposed animal model of attention deficit hyperactivity disorder (ADHD) argued to show strong face validity on the basis of behavioural characteristics. However, SHR may have fundamental alterations to the sensitivity of fluid reward due to altered renal function that has the potential to affect performance in complex reinforced behavioural tests. This could particularly confound determination of operant motivational alterations in the SHR. We assessed baseline bodyweight, home cage lab chow and water intake in the SHR and their typical control strains: Wistar and Wistar Kyoto. We also assessed sucrose preference, and appetitive and consummative positive and negative contrast for sucrose (4% versus 20%) on a motivational runway. As expected, SHR showed enhanced water intake compared to Wistar and Wistar Kyotos but comparable lab chow intake at baseline. SHR exhibited sucrose preference for 4% and 20%, as did both control strains, but the preference for 4% was enhanced in the SHR. SHR showed significant negative and positive contrast in sucrose consumption on the runway, as did Wistar Kyotos. Wistars exhibited neither. Appetitive contrast was not measurable in the SHR due to a robust locomotor velocity increase at the age of testing. The enhanced fluid intake found in the SHR argues against using fluid reinforcers in behavioural tests. We suggest the presence of both forms of contrast in the SHR is unusual for rats tested in ad lib. food conditions while the contrast pattern in Wistars indicate abnormalities in reward sensitivity in this control strain.