Figure 3. Scheme representing the flow of information provided by external stimuli to integration centers in the central brain. This central integration results in interpretation and integration of the different inputs and the generation of an appropriate response. The role of stimuli or neuronal structures marked with an asterisk (*) in aggression has been more closely analyzed. Visual information is received by the retinal ommatidia and travels through the different layers of the optic lobes, lamina, medulla and lobula complexes, to the central brain.149 The described higher integration centers of this visual information include the mushroom bodies, the central complex and different neurons in the lateral protocerebrum.97-99,150 Olfactory information is sensed by olfactory neurons expressing olfactory receptors located on the third antennal segments and the maxillary palps. Odorant cues travel via these neurons to the glomeruli in the antennal lobe from where projection neurons send this information to higher integration centers, including the mushroom bodies and the lateral horn.93,151-155 Gustatory signals are sensed by gustatory receptors expressing gustatory receptors located on the proboscis, wings, legs and vaginal plate. These neurons all project to the SOG. The SOG has been shown to project toward multiple other brain regions including the antennal lobe, the lateral horn and the mushroom bodies.96,155,156 Mechanosensory information is sensed by a variety of receptors, located all over the body, which can be subdivided into a ciliated and a non-ciliated group. Non-ciliated mechanosensory receptors include nociceptors and muscle and visceral stretch receptors. Ciliated mechanosensory receptors include: bristles responsible for touch perception, campaniform sensilla on wings and haltere providing info on flight parameters and chordotonal organs including scolopidial organs providing proprioceptive and gravireceptive information.157,158 The fly's largest chordotonal organ, Johnston’s organ, is located in the second antennal segment and represents the flies ear. Part of these neurons have been shown to innervate the antennal mechanosensory and motor center of the brain, a neuropil lateral to the SOG and the antennal lobes, further higher integration is mainly unknown.100,157,158