Individuality in the behavior of flies is not dependent on genetic characteristics. The differences caused by the interhemispheric asymmetry of the projections of neurons, connections which are distributed randomly in the process of ripening of cells. Article published in the journal Science.
There are no two identical organisms even if they are genetically identical, because the development is always influenced by many stochastic factors. Of course, individual variability concerns the brain varies its weight, size, anatomical features and even the morphology of individual neurons. Individually and innate behavior, but it is not clear what underlies this variability: the ability of neural networks to operate plastically, or random differences in their anatomy that arise in the process of development of the organism.
To study the characteristics of the brain of an individual is at the cellular level convenient for invertebrates, because they are easy to observe neurons of the hotel. One of the most popular models for biologists — flies Drosophila — suited to explore correlations anatomy of the nervous system and behavior. The brain of these insects contains only 100 thousand neurons and well-studied.
In the brain of fruit flies that is responsible for processing visual information, there is a cluster of nerve cells (dorsal cluster), the projection of which is considerably variable between individuals and even between the two hemispheres of the same flies. The axons of these neurons go to one of the two parts of the visual system: medulla or lobula. Where it will direct its projection of a single neuron due to the random events in the process of its development.
A team of scientists from Belgium, Germany and France under the leadership of Gerita Linneweber (Linneweber is below) from the Sorbonne University investigated the relationship between individual characteristics of the connections in the brain of Drosophila and behavior. This used the paradigm of Buridan, which allows to determine the response of insects to visual stimuli. Flies were placed on a white uniformly illuminated field; on the walls of the arena facing each other were placed two vertical black stripes. Insects could not reach up to these bands, and moved between them. In such conditions, flies typically walk back and forth from one contrasting object to another, but some Drosophila to examine the entire arena evenly. Thus, the behavior of insects in this paradigm is very individual. In order to assess this quantitatively, the authors used the average deviation of the trajectory of the flies from a straight line between the two strips.