Coffee time: Low caffeine dose promotes attention and focus in zebrafish

Abstract

In this study we investigated the ability of zebrafish to discriminate visual signs and associate them with a reward in an associative-learning protocol including distractors. Moreover, we studied the effects of caffeine on animal performance in the task. After being trained to associate a specific image pattern with a reward (food) in the presence of other, distractor images, the fish were challenged to locate the exact cue associated with the reward. The distractors were same-colored pattern images similar to the target. Both the target and distractors were continually moved around the tank. Fish were exposed to three caffeine concentrations for 14 days: 0 mg/L (control, n = 12), 10 mg/L (n = 14), and 50 mg/L (n = 14). Zebrafish spent most of the time close to the target (where the reward was offered) under the effects of 0 and 10 mg/L caffeine, and the shortest latency to reach the target was observed for the 10-mg/L caffeine group. Both caffeine treatments (10 and 50 mg/L) increased the average speed and distance traveled when compared to the control group. This study confirms previous results showing that zebrafish demonstrate conditioned learning ability; however, low-dose caffeine exposure seems to favor visual cue discrimination and to increase zebrafish performance in a multicue discrimination task, in which primarily focus and attention are required in order to obtain the reward.Caffeine is one of the most consumed stimulants in the world (Ferré, 2008;Lieberman, 1992). It is present in a wide range of products, including coffee, energy drinks, teas, and chocolate. The popularity of this substance lies in its beneficial effects, such as heightened attention and alertness and decreased fatigue

Effects of Caffeine Consumption on Attention Deficit Hyperactivity Disorder (ADHD) Treatment: A Systematic Review of Animal Studies

“…In a similar manner, caffeine treatment alone did not alter locomotion in SHR [51,59,60], preadolescent SHR [57], or young LDLr mice [58]. Nonetheless, caffeine treatment did increase locomotor activity in adolescent female SHRs [57], zebrafish [54]. Furthermore, it produced an increase related to dose in locomotion in CD rats and a significant attenuation of CGS-21680-induced hypolocomotion in CD rats [55], and it attenuated locomotor activity in middle-aged LDLr mice [58] and 6-OHDA lesioned rats throughout the prepubertal period [53].…”

“…Regarding attention, caffeine treatment improved the attentional and behavioral flexibility of SHRs [51], the spatial attention of 6-OHDA lesioned rats [53], and SI in ICR mice [52] during adolescence. Caffeine treatment improved the reaction time of LE and CD rats [55] and focus and attention in zebrafish [54] during adulthood.…”

“…Szczepanik et al [58] linked the age-dependent effect induced by caffeine with the idea that the blockade of adenosine A 1 /A 2A receptors attempts to renormalize a potentially maladaptive system [66], with age an important escalating factor in mice. In a different study, Ruiz-Oliveira et al [54] proposed that caffeine-induced bursts of locomotion may be caused by a decrease in fatigue [67] rather than by an anxiogenic response. Importantly, the attenuation of motor activity by caffeine consumption was determined as a natural effect of growth rather than an effect of caffeine intake by Caballero et al [53].…”

“…Ruiz-Oliveira et al [54] evaluated the effect of caffeine on zebrafish performance in a task requiring focus and attention, the discrimination task. The task took place in three phases: tank acclimation, training, and test.…”

“…Caffeine consumption (0.3 mg/mL in drinking water) and physical exercise in running wheels for 6 weeks, either during adolescence (30 days old) or adulthood (4-5 months old), did not relate to changes in spontaneous locomotion in SHR, in an open field, during the 5 min habituation phase of the object recognition test. Ruiz-Oliveira et al [54] studied the effects of caffeine on zebrafish (4 months old, wild type, both sexes). Low concentrations of caffeine (10 mg/L) affected locomotor parameters, increasing average speed and decreasing freezing behavior.…”