Zebrafish choice behavior is sensitive to reinforcer rate, immediacy, and magnitude ratios

The effects of simultaneous point gains and losses on human persistence

Four experiments assessed the effects of simultaneous point gains and losses on human responding on a moving response button. Experiments 1 and 2 examined the effects of point loss arranged in variable-time (VT) and variable-interval (VI) schedules on persistence. For that purpose, a multiple schedule was in force. One component had point gains only, and the other had point gains and losses. The net reinforcement rate was equated across components by arranging greater point gains in the gains-plus-losses component. Increases in the speed of the moving response button disrupted responding during test sessions. No differential persistence between point-gains and point-gains-and-loss conditions was observed during Experiments 1 and 2. To ensure that point losses could function as punishers, Experiments 3 and 4 compared the effects of point loss arranged in fixed-ratio (FR) or VI schedules on response rate and persistence. The FR and VI point loss decreased the response rate during Experiment 3 but did not produce differential persistence in Experiment 4. These results suggest that point loss decreases response rate but does not weaken persistence more than gains strengthen persistence.

Can we gain translational insights into the functional roles of cerebral cortex from acortical rodent and naturally acortical zebrafish models?

Cerebral cortex is found only in mammals and is particularly prominent and developed in humans. Various rodent models with fully or partially ablated cortex are commonly used to probe the role of cortex in brain functions and its multiple subcortical projections, including pallium, thalamus and the limbic system. Various rodent models are traditionally used to study the role of cortex in brain functions. A small teleost fish, the zebrafish (Danio rerio), has gained popularity in neuroscience research, and albeit (like other fishes) lacking cortex, its brain performs well some key functions (e.g., memory, consciousness and motivation) with complex, context-specific and well-defined behaviors. Can rodent and zebrafish models help generate insights into the role of cortex in brain functions, and dissect its cortex-specific (vs. non-cortical) functions? To address this conceptual question, here we evaluate brain functionality in intact vs. decorticated rodents and further compare it in the zebrafish, a naturally occurring acortical species. Overall, comparing cortical and acortical rodent models with naturally acortical zebrafish reveals both distinct and overlapping contributions of neocortex and 'precortical' zebrafish telencephalic regions to higher brain functions. Albeit morphologically different, mammalian neocortex and fish pallium may possess more functional similarities than it is presently recognized, calling for further integrative research utilizing both cortical and decorticated/acortical vertebrate model organisms.

Selective effects of conspecific movement on social preference in zebrafish (Danio rerio) using real-time 3D tracking and 3D animation

Zebrafish show social behavior such as shoaling and schooling, which is a result of complex and interdependent interactions among conspecifics. Zebrafish social behavior is interdependent in the sense that one fish's behavior affects both conspecific behavior and, as a result, their own behavior. Previous research examined effects of the interdependent interactions on the preference for social stimulus but lacked clear evidence that specific conspecific movements were reinforcing. The present research examined whether dependency between individual experimental fish's motion and a social-stimulus fish's motions contributes to preference for the social stimulus. In Experiment 1, a 3D animated stimulus fish either chased individual experimental fish or was motionless, serving as dependent and independent motions, respectively. In Experiment 2, the stimulus fish either chased experimental fish, moved away, or moved independently of the experimental fish. In both experiments, experimental fish spent more time near the stimulus fish showing dependent and interactive movements, indicating preference for dependent motion over independent motion, and chasing over other motions. Implications of these results are discussed including a potential role of operant conditioning in the preference for social stimuli.

Effects of signaled and unsignaled delays of reinforcement on response maintenance in zebrafish (Danio rerio)

Effects of delays of reinforcement on zebrafish behavior were examined following training with immediate reinforcement. The delay was either signaled by an exteroceptive stimulus present for the entire delay period (fully signaled), signaled briefly only at delay onset (partial signal), or without a stimulus (unsignaled). Unsignaled delays consistently resulted in low response rates. Fully signaled delays resulted in higher response rates than unsignaled delays when the delay was 3 s, but this difference in response rates disappeared at 6-s delays. Partially signaled delays were less effective in maintaining responding than fully signaled delays, but more effective than unsignaled delays, although these results were only suggestive. These results indicate that stimulus changes that occur during delays to reinforcement have similar effects with zebrafish as with other species, but also that responding of zebrafish has a relatively low tolerance to the delay duration. A vast majority of experiments examining zebrafish behavior suggests that the fish have potential to serve as an interface between biological and behavioral science, but this may not be the case in some research areas involving delays, such as delay discounting.