Fig. 6: Information flow through the Drosophila central brain.

a, We applied an information flow model for connectomes²⁶ to the connectome of the central brain neurons. Neurons are traversed probabilistically according to the ratio of incoming synapses from neurons that are in the traversed set. The information flow calculations were seeded with the afferent classes of neurons (including the sensory categories). b, We rounded the traversal distances to assign neurons to layers. For gustatory neurons, we show a subset of the neurons (up to 1,000) that are reached in each layer. Neurons are coloured according to the traversal distance in c. c, UMAP analysis of the matrix of traversal distances, resulting in a 2D representation of each neuron in the central brain. Neurons from the same class co-locate (see also Extended Data Fig. 9). The small UMAP plots aligned with layers in b show where the neurons for each rank from the gustatory neurons fall within the distribution (black dots). Bottom, we coloured neurons in the UMAP plot by the rank order in which they are reached from gustatory seed neurons. Red neurons are reached earlier than blue neurons. LN, local neuron. d, As in c, bottom, for multiple seed neuron sets (see Extended Data Fig. 8c for the complete set). Mech. - JO, mechanosensory—Johnston’s organ. e, For each sensory modality, we used the traversal distances to establish a neuron ranking. Graphs show the distributions of neurons of each superclass within the specific rankings for each sensory modality (see Extended Data Fig. 8a for the complete set). f, Neurons were assigned to neurotransmitter types. Graphs show their distribution within the traversal rankings similar to d. Arrows highlight the sequence of GABA–glutamate peaks found for almost all sensory modalities (see Extended Data Fig. 8b for the complete set).