The impact of brain lateralization and Anxiety-Like behaviour in an extensive operant conditioning task in Zebrafish (Danio rerio)

© 2019 by the authors. Several studies in mammals, birds, and fish have documented better cognitive abilities associated with an asymmetrical distribution of cognitive functions in the two halves of the brain, also known as 'functional brain lateralization'. However, the role of brain lateralization in learning abilities is still unclear. In addition, although recent studies suggest a link between some personality traits and accuracy in cognitive tasks, the relation between anxiety and learning skills in Skinner boxes needs to be clarified. In the present study, we tested the impact of brain lateralization and anxiety-like behaviour in the performance of an extensive operant conditioning task. Zebrafish tested in a Skinner box underwent 500 trials in a colour discrimination task (red vs. yellow and green vs. blue). To assess the degree of lateralization, fish were observed in a detour test in the presence of a dummy predator, and anxiety-like behaviour was studied by observing scototaxis response in an experimental tank divided into light and dark compartments. Although the low performance in the colour discrimination task did not permit the drawing of firm conclusions, no correlation was found between the accuracy in the colour discrimination task and the behaviour in the detour and scototaxis tests. This suggests that neither different degrees of asymmetries in brain lateralization nor anxiety may significantly impact the learning skills of zebrafish

Anisotropy of perceived numerosity: Evidence for a horizontal\u2013vertical numerosity illusion

Many studies have investigated whether numerical and spatial abilities share similar cognitive systems. A novel approach to this issue consists of investigating whether the same perceptual biases underlying size illusions can be identified in numerical estimation tasks. In this study, we required adult participants to estimate the number of white dots in arrays made of white and black dots displayed in such a way as to generate horizontal\u2013vertical illusions with inverted T and L configurations. In agreement with previous literature, we found that participants tended to underestimate the target numbers. However, in the presence of the illusory patterns, participants were less inclined to underestimate the number of vertically aligned white dots. This reflects the perceptual biases underlying horizontal\u2013vertical illusions. In addition, we identified an enhanced illusory effect when participants observed vertically aligned white dots in the T shape compared to the L shape, a result that resembles the length bisection bias reported in the spatial domain. Overall, we found the first evidence that numerical estimation differs as a function of the vertical or horizontal displacement of the stimuli. In addition, the involvement of the same perceptual biases observed in spatial tasks supports the idea that spatial and numerical abilities share similar cognitive processes

Searching for the Critical p of Macphail’s Null Hypothesis: The Contribution of Numerical Abilities of Fish

In 1985, Macphail argued that there are no differences among the intellects of non-human vertebrates and that humans display unique cognitive skills because of language. Mathematical abilities represent one of the most sophisticated cognitive skills. While it is unquestionable that humans exhibit impressive mathematical skills associated with language, a large body of experimental evidence suggests that Macphail hypothesis must be refined in this field. In particular, the evidence that also small-brained organisms, such as fish, are capable of processing numerical information challenges the idea that humans display unique cognitive skills. Like humans, fish may take advantage of using continuous quantities (such as the area occupied by the objects) as proxy of number to select the larger/smaller group. Fish and humans also showed interesting similarities in the strategy adopted to learn a numerical rule. Collective intelligence in numerical estimation has been also observed in humans and guppies. However, numerical acuity in humans is considerably higher than that reported in any fish species investigated, suggesting that quantitative but not qualitative differences do exist between humans and fish. Lastly, while it is clear that contextual factors play an important role in the performance of numerical tasks, inter-species variability can be found also when different fish species were tested in comparable conditions, a fact that does not align with the null hypothesis of vertebrate intelligence. Taken together, we believe that the recent evidence of numerical abilities in fish call for a deeper reflection of Macphail’s hypothesis

Does brain lateralization affect the performance in binary choice tasks? A study in the animal model Danio rerio

Researchers in behavioral neuroscience commonly observe the behavior of animal subjects in the presence of two alternative stimuli. However, this type of binary choice introduces a potential confound related to side biases. Understanding whether subjects exhibit this bias, and the origin of it (pre-existent or acquired throughout the experimental sessions), is particularly important to interpreting the results. Here, we tested the hypothesis according to which brain lateralization may influence the emergence of side biases in a well-known model of neuroscience, the zebrafish. As a measure of lateralization, individuals were observed in their spontaneous tendencies to monitor a potential predator with either the left or the right eye. Subjects also underwent an operant conditioning task requiring discrimination between two colors placed on the left-right axis. Although the low performance exhibited in the operant conditioning task prevents firm conclusions from being drawn, a positive correlation was found between the direction of lateralization and the tendency to select the stimulus presented on one specific side (e.g., right). The choice for this preferred side did not change throughout the experimental sessions, meaning that this side bias was not the result of the prolonged training. Overall, our study calls for a wider investigation of pre-existing lateralization biases in animal models to set up methodological counterstrategies to test individuals that do not properly work in a binary choice task with stimuli arranged on the left-right axis

Is the Susceptibility to Visual Illusions Related to the Relative Brain Size? Insights from Small-Brained Species

Visual illusions are powerful tools to understand similarities and differences in the perceptual mechanisms of human and nonhuman animals. Such investigation is particularly important in the presence of animal species whose brains largely differ from ours, because it can reveal whether perceptual laws described in humans are strictly related to the peculiarity of large brains, as the case of mammals and birds. Here we review the literature on visual illusions in species with a much smaller relative brain size. Most works on this subject have investigated fish, whereas only a few studies have been conducted on amphibians and reptiles. Taken together, the existing literature found more similarities than differences in the perceptual mechanisms underlying size, numerosity, brightness, motion, and subjective contours among vertebrates, regardless of the high variability in the relative brain size of the species

How COVID-19 lockdown affected physical activity levels and wellbeing: an Italian Survey

Numerous studies have examined the relationship between changes in Physical Activity (PA) and mental health during the lockdown. With respect to Italy, there is a lack of studies investigating changes in the type of and in the levels of PA performed pre- and during the lockdown and the relationship among PA changes and psychological variables such as distress, intolerance of uncertainty (IU), physical and mental health, body dissatisfaction (BD), and motivation towards PA. Furthermore, no studies have considered pre-lockdown activity levels and gender differences when investigating changes in PA and psychological variables. For this purpose, we administered questionnaires assessing PA levels before and during the lockdown and psychological variables. We collected data from 1364 adults (377 males). Results indicated that 48.40% of participants did not change their PA levels, and a small percentage increased it (8.96%). In terms of PA reduction, 42.64% of participants showed a decrease in PA. These participants were highly active before the pandemic. We observed that a PA reduction during the lockdown was associated with higher distress and lower mental health, while changes in PA did not seem to have affected BD and IU. Only small differences in physical health were found between individuals who increased, maintained, or decreased PA. Mixed results emerged pertaining to motivation towards PA. Gender differences were not related to participants' PA level pre-lockdown nor to PA changes from pre- to the lockdown. Our study further supports the hypothesis that practicing PA during stressful situations like the pandemic may preserve psychological wellbeing