On Oct 22, 2010, a research team from the Institute of Biophysics, Chinese Academy of Sciences and led by Dr. Zhefeng Gong, an Associate Professor from Professor Li Liu’s group published a report on Science about their recent discovery that two pairs of central brain neurons regulate Drosophila larval preference between light and darkness.
Animal behaviors are generally quite flexible. An animal can adjust their behavior according to the changes in natural environment, nutritional condition as well as factors like age. But, how are animal innate behaviors affected by external and internal factors? The underlying neural circuit is still not fully understood. In the case of human being, the behavioral habits and preferences changes as the external environmental factors or internal factors like age change. For example, love and hatred, both can change along with changes in external and internal conditions. In the case of invertebrates like Drosophila larva, the younger prefers to stay in dark whereas the older leave for sites with more light. Such behavioral change might meet the physiological needs ---- the larvae no longer need food that makes the darkness but they need a cleaner place for pupation. Gong et al.’s study demonstrated that two pairs of central brain neurons control the switch the preference between the light/darkness. If the neuronal activity is inhibited, the originally photophobic larva will prefer to stay in light; if the neurons are activated, even the older larva that does not avoid light now becomes photophobic.
These two pairs of neurons, the so called NP394 neurons, directly form synapses with and receive input from the biological rhythm-related lateral neurons (pdf neurons) which receive direct inputs from the larval visual sensory organs, the Bolwig’s organ (BO). Functional calcium imaging data showed that killing the pdf neurons actually enhanced the NP394 neuron’s response to visual stimulation, suggesting that there exists functional connection between the NP394 neurons and the pdf neurons and the pdf neurons play an inhibitory role on NP394 neurons. And the pdf neurons are not the only input neurons that deliver visual inform to NP394 neurons.
Dr. Nina Vogt and Professor Claude Desplan from New York University commented on this work as a study that “advances our understanding of how the animal brain interprets visual cues” and also a step “toward determining the neural basis of how both environmental and intrinsic cues modify innate behaviors”.
For this study, the macro- and micro- environments played crucial roles. International colleagues kindly provided some important experimental materials and the research progresses in related fields offered the most recent technical tools in answering the questions raised in the study. In the lab, there has accumulated a large amount of knowledge which forms the basis for further in-depth study and new techniques are encouraged for application. But the most decisive factors are the diligence of the authors and their serious attitude in scientific study. After preparation of the manuscript ready for submission, the authors have postponed the submission for several times, just to address the questions in study as complete and clear as possible.
