Segregation of Visual Information in the Bee Brain

Abstract

Photoreceptors in the eye basically provide information about light intensities from which brains extract different kinds of visual cues (e.g. color, movement, pattern). How do the properties and response characteristic of visual interneurons differ from the periphery to the central brain? I intracellularly recorded from neurons in the second and third optic ganglia (medulla and lobula) and the central brain (protocerebrum) of bees (mainly bumblebees; Bombus impatiens) while presenting color and motion stimuli. Bees rely on such stimuli during flight and foraging and show sophisticated visual learning abilities. We found that neurons in the distal medulla are color specific while ones in the proximal medulla show complex, often antagonistic color responses. Neurons in the distal lobula (layers 1-4) mainly process motion information while the proximal lobula (layers 5 and 6) seems to combine color and motion responses. Anterior parts of the central brain receive complex input representing combinations of motion and color information characterized by specific temporal properties (e.g. temporal precision, 'novelty' information or entrainment). This kind of often sparsely coded information is also represented in the mushroom bodies, learning and memory centers in the insect brain. In contrast, posterior parts of the central brain receive mainly motion information and show more reliable responses yet less precise spike timing. While the former kind of information (temporally precise or novelty in anterior pathways) is suited to form stimulus associations relevant during foraging, the latter, more reliable information is thought to support fast optomotor flight control maneuvers and other less plastic behaviors.