Barth M, Heisenberg M
Theodor-Boveri-Institut für Biowissenschaften Lehrstuhl für Genetik, Würzburg, Germany.
Learn Mem. 1997 Jul-Aug;4(2):219-29. doi: 10.1101/lm.4.2.219.
The brain of Drosophila is structurally altered by sensory stimuli that the flies receive during their adult life. Size and fiber number of the mushroom bodies, central complex, and optic lobes are influenced by social, spatial, or olfactory cues. Recently, the optic lobes have been shown to depend on the light regime that flies experience. Structural plasticity in the brain is thought to be a correlate of functional adaptations and long-term memory. We therefore extend our investigation of volume changes to the calyces of the mushroom bodies and the central complex. We show that rearing flies in constant light for 4 days increases the volume of both structures by up to 15% compared to rearing them in total darkness. Much of this difference develops during the first day. The effect of light is not hormonally mediated, as monocularly deprived flies develop a smaller ipsilateral calyx. Mutant analysis suggests that light generates its effects through known visual pathways. In contrast to the optic lobes, in the calyx and central complex structural changes can be linked to cAMP signaling, as in the mutants dunce1 and amnesiac1 no volume differences are observed. Surprisingly, the mutant rutabaga1 shows a prominent light-dependent volume increase in the calyx and central complex, dissociating structural from behavioral plasticity. In complete darkness wild-type flies grow larger calyces under crowded conditions in their normal culture vials than if kept in small groups on fresh food. This stimulating effect of crowding is not observed in any of the cAMP mutants, including rutabaga1.
果蝇的大脑会因成虫期所接收的感觉刺激而发生结构改变。蘑菇体、中央复合体和视叶的大小及纤维数量会受到社交、空间或嗅觉线索的影响。最近研究表明，视叶依赖于果蝇所经历的光照条件。大脑中的结构可塑性被认为是功能适应性和长期记忆的一个相关因素。因此，我们将对体积变化的研究扩展到蘑菇体的萼片和中央复合体。我们发现，与在完全黑暗环境中饲养相比，持续光照4天饲养的果蝇，这两个结构的体积会增加多达15%。这种差异大部分在第一天就会显现。光照的影响并非由激素介导，因为单眼剥夺的果蝇同侧萼片会变小。突变分析表明，光照通过已知的视觉通路产生其效应。与视叶不同，在萼片和中央复合体中，结构变化可与cAMP信号传导相关联，因为在突变体dunce1和amnesiac1中未观察到体积差异。令人惊讶的是，突变体rutabaga1在萼片和中央复合体中显示出明显的光照依赖性体积增加，这将结构可塑性与行为可塑性区分开来。在完全黑暗的环境中，野生型果蝇在正常培养瓶中拥挤条件下比在新鲜食物上小群体饲养时萼片长得更大。在包括rutabaga1在内的任何cAMP突变体中都未观察到拥挤的这种刺激作用。
