The neural basis of social recognition and affiliation
Please note: Johannes Larsch continues his research at the Université de Lausanne: Center for Integrative Genomics, UNIL.
Many animals live in groups and tirelessly coordinate movement with conspecifics in swarms, flocks, herds and shoals. For individuals, joining a group gives access to collective information about food or shelter and dilutes risk when predators attack. The importance of such group affiliation for survival suggests that dedicated neural circuits exist and that these circuits are conserved across animal species. We investigate shoaling, the innate behavior of swimming in groups in juvenile zebrafish to understand how social interactions emerge from neural computations in individual animals.
Psychophysics of Social Interactions in Virtual Reality
During shoaling, zebrafish look at each other. For what exactly? Are there specific sensory signals from each animal that attract conspecifics to join a group? And when attraction leads to coordination between fish, is there a fixed choreography or improvised turn taking? The fluent exchange of social signals between animals in a shoal has been hard to crack analytically. How can we separate cause from effect and measure each individual’s contribution to this entangled behavior?
We built a virtual reality system where freely swimming fish interact with computer controlled avatars. By analyzing interactions with systematically altered avatars, we discovered shapes and movements that attracted individual fish to virtual partners. Surprisingly, fish-like biological motion but not fish-like appearance was most important to trigger shoaling. Fish judged virtual partners within seconds and independent of reciprocal attraction. These results open exciting opportunities to investigate how the brain processes defined visual cues to control social behavior.
Brain-Wide Activity Mapping during Social Recognition
Shoaling behavior generates a complex and dynamic visual scenery where individuals must quickly locate and recognize conspecifics to control steering maneuvers and maintain a coherent group. Which parts of the conspecifics’ appearance or ‘gestalt’ are encoded in neural activity? What are the brain areas, cell types and circuit motifs driving shoaling behavior?
To address these questions, we monitor brain activity in juvenile zebrafish while presenting visual stimuli that trigger shoaling. Neurons that selectively respond to conspecific cues are candidates for functional and anatomical investigation including laser ablation, optogenetic activity modulation and circuit tracing.
Large-Scale Screening for Genetic Modifiers of Social Affiliation
Social affiliation is widespread among animals and, partly, controlled by conserved neural circuits and modulatory systems. At the same time, affiliation is highly variable across individuals within species ranging from loners to serial socializers. The extremes of this spectrum can be associated with deficits in processing social signals and, in humans, with psychiatric disorders such as autism and schizophrenia. Understanding sources of this behavioral diversity might reveal principles of neural function that hold true across species and offer mechanistic insights into human disorders.
We use large-scale high-content behavior analysis to characterize the phenotypic spectrum of shoaling behavior in wild type zebrafish and to screen a large collection of mutant zebrafish lines with lesions in genes associated with psychiatric disorders.