Biology subjects

Lauritzen, J. S.

Publications and source records attributed to Lauritzen, J. S..

3 recordsLinked to original sources

bioRxiv2020

Circuit reorganization in the Drosophila mushroom body calyx accompanies memory consolidation

The capacity of utilizing past experience to guide future action is a fundamental and conserved function of the nervous system. Associative memory formation initiated by the coincident detection of a conditioned stimulus (CS, e.g. odour) and an unconditioned stimulus (US, e.g. sugar reward) can lead to a short-lived memory trace (STM) within distinct circuits [1-5]. Memories can be consolidated into long-term memories (LTM) through processes that are not fully understood, but depend on de-novo protein synthesis [6, 7], require structural modifications within the involved neuronal circuits and might lead to the recruitment of additional ones [8-17]. Compared to modulation of existing connections, the reorganization of circuits affords the unique possibility of sampling for potential new partners [18-20]. Nonetheless, only few examples of rewiring associated with learning have been established thus far [14, 21-24]. Here, we report that memory consolidation is associated with the structural and functional reorganization of an identified circuit in the adult fly brain. The formation and retrieval of olfactory associative memories in Drosophila requires the mushroom body (MB) [25]. We identified the individual synapses of olfactory projection neurons (PNs) that deliver a conditioned odour to the MB and reconstructed the complexity of the microcircuit they form. Combining behavioural experiments with high-resolution microscopy and functional imaging, we demonstrated that the consolidation of appetitive olfactory memories closely correlates with an increase in the number of synaptic complexes formed by the PNs that deliver the conditioned stimulus and their postsynaptic partners. These structural changes result in additional functional synaptic connections.

neuroscience↗

bioRxiv2019

Regulation of modulatory cell activity across olfactory structures in Drosophila melanogaster

All centralized nervous systems possess modulatory neurons that arborize broadly across multiple brain regions. Such modulatory systems are critical for proper sensory, motor, and cognitive processing. How single modulatory neurons integrate into circuits within their target destination remains largely unexplored due to difficulties in both labeling individual cells and imaging across distal parts of the CNS. Here, we take advantage of an identified modulatory neuron in Drosophila that arborizes in multiple olfactory neuropils. We demonstrate that this serotonergic neuron has opposing odor responses in its neurites of the antennal lobe and lateral horn, first and second order olfactory neuropils respectively. Specifically, processes of this neuron in the antennal lobe have responses that are inhibitory and odor-independent, while lateral horn responses are excitatory and odor-specific. The results show that widespread modulatory neurons may not function purely as integrate-and-fire cells, but rather their transmitter release is locally regulated based on neuropil. As nearly all vertebrate and invertebrate neurons are subject to synaptic inputs along their dendro-axonic axis, it is likely that our findings generalize across phylogeny and other broadly-projecting modulatory systems.\n\nSignificanceThe centrifugal innervation of neuronal circuits is ubiquitous across centralized nervous systems. Such inputs often arise from modulatory neurons that arborize broadly throughout the brain. How information is integrated in such cells and how release from their distant terminals is regulated remains largely unknown. We show that a serotonergic neuron that innervates multiple stages of odor processing in Drosophila has distinct activity throughout its neurites, including opposite polarity responses in first and second order olfactory neuropils. Disparate activity arises from local interactions within each target region. Our results show that such neurons exhibit dendritic computation rather than somatic integration alone, and that examining local interactions at release sites is critical for understanding centrifugal innervation.

neuroscience↗

bioRxiv2017

A Complete Electron Microscopy Volume Of The Brain Of Adult Drosophila melanogaster

Drosophila melanogaster has a rich repertoire of innate and learned behaviors. Its 100,000-neuron brain is a large but tractable target for comprehensive neural circuit mapping. Only electron microscopy (EM) enables complete, unbiased mapping of synaptic connectivity; however, the fly brain is too large for conventional EM. We developed a custom high-throughput EM platform and imaged the entire brain of an adult female fly. We validated the dataset by tracing brain-spanning circuitry involving the mushroom body (MB), intensively studied for its role in learning. Here we describe the complete set of olfactory inputs to the MB; find a new cell type providing driving input to Kenyon cells (the intrinsic MB neurons); identify neurons postsynaptic to Kenyon cell dendrites; and find that axonal arbors providing input to the MB calyx are more tightly clustered than previously indicated by light-level data. This freely available EM dataset will significantly accelerate Drosophila neuroscience.\n\nHIGHLIGHTS- A complete adult fruit fly brain was imaged, using electron microscopy (EM)\n- The EM volume enables brain-spanning mapping of neuronal circuits at the synaptic level\n- Olfactory projection neurons cluster more tightly in mushroom body calyx than expected from light-level data\n- The primary postsynaptic targets of Kenyon cells (KCs) in the MB are other KCs, as well as the anterior paired lateral (APL) neuron\n- A newly discovered cell type, MB-CP2, integrates input from several sensory modalities and provides microglomerular input to KCs in MB calyx\n- A software pipeline was created in which EM-traced skeletons can be searched for within existing large-scale light microscopy (LM) databases of neuronal morphology, facilitating cell type identification and discovery of relevant genetic driver lines

neuroscience↗