May 14, 2014
Follow That Fish – Understanding Alcohol And Social Behavior
April Flowers for redOrbit.com – Your Universe Online
Alcohol consumption affects social behavior, as any college student can tell you. But does it have to have such an effect? A new study from New York University's (NYU) Polytechnic School of Engineering suggests that the complex interplay between alcohol and social behavior can be understood and the negative effects perhaps mitigated. Their groundbreaking experiments, described in the journal Alcohol: Clinical and Experimental Research, center on an unlikely test subject: the zebrafish.Maurizio Porfiri, associate professor of mechanical and aerospace engineering and director of the school’s Dynamical Systems Laboratory, led a team of scientists that included NYU School of Engineering Research Scholar Fabrizio Ladu and Postdoctoral Fellow Sachit Butail, along with Visiting Scientist Simone Macrì, Ph.D., of the Istituto Superiore di Sanità in Rome, Italy. Their experiment completely overturned the traditional paradigm for alcohol-related research. The traditional paradigm consists of all subjects being exposed to alcohol, then analyzing the behavior and movements of the group. The new method allows for detailed tracking of a single, alcohol-exposed zebrafish swimming amid a school of "sober" fish.
The working theory driving this experiment is that an individual's response to alcohol would vary depending on the presence or absence of unexposed peers. The remarkable effect that the alcohol-exposed fish would have on its peers, however, was completely unexpected.
For the experiment, a single zebrafish was exposed to four concentrations of ethanol in water—ranging from zero to acute exposure, which causes no harm to the fish—then released into a group of untreated zebrafish. The team believes their efforts are the first to allow ethanol-exposed and untreated zebrafish to swim freely together. The researchers developed a custom algorithm that allowed them to track a single fish throughout the experiment, while at the same time analyzing group behavior.
Alcohol exposure has been shown to affect the locomotion of a zebrafish in previous studies. At low concentrations, the fish's movements become faster. As the dose increases, the swimming motion slows down. The cohesion of the group is also negatively affected by alcohol exposure.
As expected, the single exposed zebrafish showed predictable locomotion changes when observed alone after exposure. When added to the unexposed group, however, the zebrafish's behavior was remarkably different. The swimming speeds of fish exposed to intermediate or high concentrations nearly doubled, indicating that the presence of peers had a substantial impact on social behavior under the influence of alcohol.
Perhaps the most remarkable finding of the study was that the unexposed fish also modulated their behavior and swimming speeds differentially in the presence of a shoalmate exposed to different levels of alcohol.
“These results were very surprising,” explained Porfiri. “It is clear that the untreated fish were matching the swimming speed of the alcohol-exposed fish, and this correlation was especially strong at an intermediate level of alcohol exposure. At very high or low levels, the influence decreases.”
The swimming speed increase of the exposed individual might be explained as hyper-reactivity to an enriched environment—in other words, the tank full of unexposed peers. As with humans, alcohol has been shown to reduce inhibitory behavior in zebrafish—meaning that the faster swimming speed could also reflect a heightened interest in interacting with the school. Regardless of the underlying mechanism, this deviation from expected behavior is very significant, the authors say, because it highlights the ability of social stimuli, such as the untreated fish, to change an individual’s response to alcohol.
The unexpected ability of the alcohol-exposed zebrafish to influence the behavior of the school might be a form of leadership. The researchers caution, however, that aggressive, risk-taking behaviors, which are common under the disinhibitory effects of alcohol, might resemble normal leadership behavior in this species.
“This research integrates rigorous principles from engineering and biology to develop an experiment that sheds light on the complex interactions among individuals in a group, their individuality and their collective behavior,” said Massimo Ruzzene, NSF program director for the Division of Civil, Mechanical and Manufacturing Innovation. “Analysis of complex dynamical systems is an important area of research. An understanding of complex systems, ranging from smart robots that assist in surgery to manufacturing enterprises and emergency response teams, is integral to our ability to respond effectively to emerging challenges and opportunities.”
The new method of experimentation developed for this study holds a great deal of promise for future research on the social determinants of individual responses to alcohol, the researchers believe. The team was able to study how social environments shape the impact of alcohol on behavior by dissociating sociality from exposure. To what degree social influence is exerted by exposed or unexposed individuals is affected by group size will be the focus of future studies by the group.
The findings will advance our understanding of how social interactions magnify or mitigate negative effects of alcohol abuse, and could possibly lead to new, improved therapies to reduce these effects.