The Drosophila Mushroom Body: From Architecture to Algorithm in a Learning Circuit

Annu Rev Neurosci. 2020 Jul 8;43:465-484. doi: 10.1146/annurev-neuro-080317-0621333. Epub 2020 Apr 13.

Abstract

The Drosophila brain contains a relatively simple circuit for forming Pavlovian associations, yet it achieves many operations common across memory systems. Recent advances have established a clear framework for Drosophila learning and revealed the following key operations: a) pattern separation, whereby dense combinatorial representations of odors are preprocessed to generate highly specific, nonoverlapping odor patterns used for learning; b) convergence, in which sensory information is funneled to a small set of output neurons that guide behavioral actions; c) plasticity, where changing the mapping of sensory input to behavioral output requires a strong reinforcement signal, which is also modulated by internal state and environmental context; and d) modularization, in which a memory consists of multiple parallel traces, which are distinct in stability and flexibility and exist in anatomically well-defined modules within the network. Cross-module interactions allow for higher-order effects where past experience influences future learning. Many of these operations have parallels with processes of memory formation and action selection in more complex brains.

Keywords: action selection; associative learning; dopamine; pattern separation; plasticity; valence.

Publication types

  • Review

MeSH terms

  • Animals
  • Behavior, Animal
  • Humans
  • Learning / physiology*
  • Memory / physiology*
  • Mushroom Bodies / physiology*
  • Olfactory Pathways / physiology
  • Smell / physiology*