RobustCircuit Project 8

Project 8 focuses on the higher order visual circuit defined by Dorsal Cluster Neurons (DCNs) that modulates attention-related optomotor behavior.  DCN circuit patterns are stochastically different between the left and right brain hemispheres.  Levels of asymmetry are sex-specific, higher in males, and a predictor of more precise and robust optomotor behavior.

Imprecision: DCN wiring patterns develop independently and variably between the left and right brain hemispheres.  Developmental imprecisions are higher in males than females.

Robustness: The outcomes of the DCN developmental process are robustly different distributions for left/right asymmetry and, correspondingly, behavior in males and females Hypothesis: Increased developmental imprecision specifically in male brains leads to increased DCN asymmetry and thereby increased visual attention behavior on average in males.

Hypothesis: Variability of intrinsic neuronal properties and electrical coupling is not detrimental, but rather supports a stable network splay state for efficient activation of flight muscles with a potentially reduced requirement for complex regulatory control.

Project Summary

In sexually dimorphic animals, males and females display qualitative differences in behavior, usually related to courtship and reproduction. Additionally, males and females exhibit quantitative differences for behaviors shared by both sexes. For example, both male and female Drosophila exhibit visual fixation behavior in Buridan’s paradigm, but female behavior is on average more ‘exploratory’ while male behavior is on average more ‘fixated’. My recent work has shown that increasing asymmetry of axonal projections of contralaterally projecting interneurons, the Dorsal Cluster Neurons (DCNs), leads to increased visual fixation behavior. In preliminary work for RobustCircuit, I have shown that there is indeed a higher asymmetry of DCN axonal projections in males compared to females. Since the development of DCN projection patterns includes intrinsically stochastic, non-heritable processes, these preliminary observations give rise to a surprising hypothesis: Male DCN wiring asymmetry (and consequently increased visual fixation behavior) are the consequence of a male-specific increase in the variability of developmental processes determining DCN branching patterns. An increase of DCN branching variability on the left and right side of the brain causes a rise of the average asymmetry and leads to sex-specific distributions of individually probabilistic behaviors. I hypothesize that male and female populations consist of individuals with a wide range of randomly unique, non-heritable behavior, while on average, genetic determinants in males shift the distribution average to more fixated visual orientation behavior. P8 will interrogate the sex-specific mechanisms underlying this distribution shift. When this work is concluded, I will have tested how the robust development of sexually dimorphic behavioral distributions is achieved through a genetically encoded increase in branching variability in males compared to females.

References

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