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Parallel processing of neuronal inputs relies on assembling neural circuits into distinct synaptic-columns and layers. This is orchestrated by matching recognition molecules between afferent growth cones and target areas. Controlling the expression of these molecules during development is crucial but not well understood. The developing Drosophila visual system is a powerful genetic model for addressing this question. In this model system, the achromatic R1-6 photoreceptors project their axons in the lamina while the R7 and R8 photoreceptors, which are involved in colour detection, project their axons to two distinct synaptic-layers in the medulla. Here we show that the conserved homeodomain transcription factor Orthodenticle (Otd), which in the eye is a main regulator of rhodopsin expression, is also required for R1-6 photoreceptor synaptic-column specific innervation of the lamina. Our data indicate that otd function in these photoreceptors is largely mediated by the recognition molecules flamingo (fmi) and golden goal (gogo). In addition, we find that otd regulates synaptic-layer targeting of R8. We demonstrate that during this process, otd and the R8-specific transcription factor senseless/Gfi1 (sens) function as independent transcriptional inputs that are required for the expression of fmi, gogo and the adhesion molecule capricious (caps), which govern R8 synaptic-layer targeting. Our work therefore demonstrates that otd is a main component of the gene regulatory network that regulates synaptic-column and layer targeting in the fly visual system. [ABSTRACT FROM AUTHOR]

The cognitive functioning varies during the day and it can be modulated by the time in which individuals reach their arousal peak during the day. Morning-types should have cognitive peak in the morning while evening-types should have cognitive peak in the evening, reflecting the synchrony effect. The aim was to investigate time-of-day and synchrony effects on long-term memory with a network-like structure, using semantic classification and number-matching tasks. Evening- and morning-types performed two tasks in three times of the day: morning, afternoon and evening. In semantic classification task, a time-of-day effect was found while synchrony effect did not. Moreover, the circadian typology seemed to modulate the retrieval efficiency from long-term memory. In number-matching task, no time-of-day as well as synchrony effects were reliable. As before, the circadian typology seemed to influence the retrieval of semantic information. The study may demonstrate that circadian typology seems to differ for the strategies in retrieval information from memory with a network-like structure. [ABSTRACT FROM AUTHOR]