Integrative properties of the Pe1 neuron, a unique mushroom body output neuron

A mushroom body extrinsic neuron, the Eel neuron, connects the peduncle of the mushroom body (MB) with two areas of the protocerebrum in the honeybee brain, the lateral protocerebral lobe (LPL) and the ring neuropil around th e alpha-lobe. Each side of the bee brain contains only one Eel neuron. Usin g a combination of intracellular recording and neuroanatomical techniques w e analyzed its properties of integrative processing of the different sensor y modalities. The Pel neuron responds to visual, mechanosensory, and olfact ory stimuli. The responses are broadly tuned, consisting of a sustained inc rease of spike frequency to the onset and offset of light flashes, to horiz ontal and vertical movements of extended objects, to mechanical stimuli app lied to the antennae or mouth parts, and to all olfactory stimuli tested (2 9 chemicals). These multisensory properties are reflected in its dendritic organization. Serial reconstructions of intracellularly stained Pel neurons using confocal microscopy reveal that the Pel neuron arborizes throughout all layers of MB peduncle with finger-like, vertically oriented dendrites. The peduncle of the MB is formed by the axons of Kenyon cells, whose dendri tic inputs are organized in modality-specific subcompartments of the calyx region. The peduncular arborization indicates that the Eel neuron receives input from Kenyon cells of all calycal subcompartments. Because the Pel neu ron changes its odor responses transiently as a consequence of olfactory le arning, we hypothesize that the multimodal response properties might have a role in memory consolidation and help to establish contextual references i n the long-term trace.