Pupil-linked arousal modulates behavior in rats performing a whisker deflection direction discrimination task

Non-luminance-mediated changes in pupil size have been widely used to index arousal state. Recent animal studies have demonstrated correlations between behavioral state-related pupil dynamics and sensory processing. However, the relationship between pupil-linked arousal and behavior in animals performing perceptual tasks has not been fully elucidated. In the present study, we trained head-fixed rats to discriminate between directions of whisker movements using a Go/No-Go discrimination paradigm while imaging their pupils. Reaction times in this discrimination task were significantly slower than in previously reported detection tasks with similar setup, suggesting that discrimination required an increased cognitive load. We found the pupils dilated for all trials following stimulus presentation. Interestingly, in correct rejection trials, where pupil dilations solely resulted from cognitive processing, dilations were larger for more difficult stimuli. Baseline pupil size before stimulus presentation strongly correlated with behavior, as perceptual sensitivity peaked at intermediate pupil baselines and reaction time was fastest at large baselines. We further explored these relationships by investigating to what extent pupil baseline was predictive of upcoming behavior and found that a Bayesian decoder had significantly greater-than-chance probability in correctly predicting behavioral outcomes. Moreover, the outcome of the previous trial showed a strong correlation with behavior on present trials. Animals were more liberal and faster in responding following hit trials, whereas perceptual sensitivity was greatest following correct rejection trials. Taken together, these results suggest a tight correlation between pupil dynamics, perceptual performance, and reaction time in behaving rats, all of which are modulated by fluctuating arousal state. NEW & NOTEWORTHY In this study, we for the first time demonstrated that head-fixed rats were able to discriminate different directions of whisker movement. Interestingly, we found that the pupil dilated more when discriminating more difficult stimuli, a phenomenon reported in human subjects but not in animals. Baseline pupil size before stimulus presentation was found to strongly correlate with behavior, and a Bayesian decoder had significantly greater-than-chance probability in correctly predicting behavioral outcomes based on the baseline pupil size.

Observation of the Effect of Gender on Children’s Concept of Motion; Sustainability Issue

Determination of the parameters of the movement of surrounding objects, and in particular their speed, is one of the basic skills of a human being. The study of development of basic concepts of motion has been done for years with different methods and in different contexts. We have analyzed the effect of the physical/scientific image of the world introduced to children by school education and its long- and short-term cognitive consequences. Our studies showed that children differentiate the concept of speed into two more specific concepts: average speed and instantaneous velocity. In the present work we present how the gender context is superimposed on this general picture. We found that initial, genuine pre-school concept of speed of girls and boys is, on average, different. Our analysis shows also that this gender effect vanishes quickly together with the appearance of physical definitions of kinematical quantities in physics/science curricula. We discuss also methodological aspect of the statistical ‘gender gap’ measure and we calculated the gender effect chance probability, p-value, to be slightly less than 0.001. The importance of observed effect for the sustainable science teaching processes is discussed.

Commentary:: Low-Confidence Responses on the Vocabulary Size Test

McDonald and Asaba (Vocabulary Learning and Instruction, 2015) reported an administration of the Vocabulary Size Test that was modified to include ‘‘I don’t know’’ as a fifth response option on all items, and in which participants later responded to the items originally marked as ‘‘I don’t know’’. McDonald and Asaba were inclined to favour the score calculated without the later (reluctant or low-confidence) responses. It is argued here that this goes beyond the data. In many educational contexts, strong encouragement is given to respond when unsure, as examinees to have a better-than-chance probability of being correct, and will be disadvantaged if they do not respond.