Associative Odor Learning in <i>Drosophila</i> Abolished by Chemical Ablation of Mushroom Bodies

TLDR

The mushroom bodies of adult *Drosophila melanogaster*, comprising about 2,500 Kenyon cell fibers derived from four neuroblasts, are a key brain structure. Selective ablation of these Kenyon cells is achieved by feeding hydroxyurea to newly hatched larvae, producing precise and complete loss of mushroom bodies. Flies that develop without mushroom bodies exhibit normal olfactory, shock, and locomotor responses yet fail to learn odor cues paired with electric shock in a classical conditioning paradigm, confirming that mushroom bodies mediate associative odor learning.

Abstract

The corpora pedunculata, or mushroom bodies (MBs), in the brain of Drosophila melanogaster adults consist of approximately 2500 parallel Kenyon cell fibers derived from four MB neuroblasts. Hydroxyurea fed to newly hatched larvae selectively deletes these cells, resulting in complete, precise MB albation. Adult flies developing without MBs behave normally in most respects, but are unable to perform in a classical conditioning paradigm that tests associative learning of odor cues and electric shock. This deficit cannot be attributed to reductions in olfactory sensitivity, shock reactivity, or locomotor behavior. The results demonstrate that MBs mediate associative odor learning in flies.