@article {67773, title = {Non-preferred contrast responses in the Drosophila motion pathways reveal a receptive field structure that explains a common visual illusion.}, journal = {Current Biology}, volume = {31}, year = {2021}, month = {2021 Dec 06}, pages = {5286}, abstract = {

Diverse sensory systems, from audition to thermosensation, feature a separation of inputs into ON (increments) and OFF (decrements) signals. In the Drosophila visual system, separate ON and OFF pathways compute the direction of motion, yet anatomical and functional studies have identified some crosstalk between these channels. We used this well-studied circuit to ask whether the motion computation depends on ON-OFF pathway crosstalk. Using whole-cell electrophysiology, we recorded visual responses of T4 (ON) and T5 (OFF) cells, mapped their composite ON-OFF receptive fields, and found that they share a similar spatiotemporal structure. We fit a biophysical model to these receptive fields that accurately predicts directionally selective T4 and T5 responses to both ON and OFF moving stimuli. This model also provides a detailed mechanistic explanation for the directional preference inversion in response to the prominent reverse-phi illusion. Finally, we used the steering responses of tethered flying flies to validate the model{\textquoteright}s predicted effects of varying stimulus parameters on the behavioral turning inversion.

}, issn = {1879-0445}, doi = {10.1016/j.cub.2021.09.072}, author = {Gruntman, Eyal and Reimers, Pablo and Romani, Sandro and Reiser, Michael B} } @article {65246, title = {The computation of directional selectivity in the OFF motion pathway.}, journal = {eLife}, volume = {8}, year = {2019}, month = {2019 Dec 11}, abstract = {

In flies, the direction of moving ON and OFF features is computed separately. T4 (ON) and T5 (OFF) are the first neurons in their respective pathways to extract a directionally selective response from their non-selective inputs. Our recent study of T4 found that the integration of offset depolarizing and hyperpolarizing inputs is critical for the generation of directional selectivity. However, T5s lack small-field inhibitory inputs, suggesting they may use a different mechanism. Here we used whole-cell recordings of T5 neurons and found a similar receptive field structure: fast depolarization and persistent, spatially offset hyperpolarization. By assaying pairwise interactions of local stimulation across the receptive field, we found no amplifying responses, only suppressive responses to the non-preferred motion direction. We then evaluated passive, biophysical models and found that a model using direct inhibition, but not the removal of excitation, can accurately predict T5 responses to a range of moving stimuli.

}, issn = {2050-084X}, doi = {10.7554/eLife.50706}, author = {Gruntman, Eyal and Romani, Sandro and Reiser, Michael B} } @article {48998, title = {Simple integration of fast excitation and offset, delayed inhibition computes directional selectivity in Drosophila.}, journal = {Nature Neuroscience}, volume = {21}, year = {2018}, month = {2018 Jan 08}, pages = {250-7}, abstract = {

A neuron that extracts directionally selective motion information from upstream signals lacking this selectivity must compare visual responses from spatially offset inputs. Distinguishing among prevailing algorithmic models for this computation requires measuring fast neuronal activity and inhibition. In the Drosophila melanogaster visual system, a fourth-order neuron-T4-is the first cell type in the ON pathway to exhibit directionally selective signals. Here we use in vivo whole-cell recordings of T4 to show that directional selectivity originates from simple integration of spatially offset fast excitatory and slow inhibitory inputs, resulting in a suppression of responses to the nonpreferred motion direction. We constructed a passive, conductance-based model of a T4 cell that accurately predicts the neuron{\textquoteright}s response to moving stimuli. These results connect the known circuit anatomy of the motion pathway to the algorithmic mechanism by which the direction of motion is computed.

}, issn = {1546-1726}, doi = {10.1038/s41593-017-0046-4}, author = {Gruntman, Eyal and Romani, Sandro and Reiser, Michael B} } @article {47746, title = {Integration of the olfactory code across dendritic claws of single mushroom body neurons.}, journal = {Nature Neuroscience}, volume = {16}, year = {2013}, month = {2013 Oct 20}, pages = {1821-9}, abstract = {

In the olfactory system, sensory inputs are arranged in different glomerular channels, which respond in combinatorial ensembles to the various chemical features of an odor. Here we investigate where and how this combinatorial code is read out deeper in the brain. We exploit the unique morphology of neurons in the mushroom body (MB), which receive input on large dendritic claws. Imaging odor responses of these dendritic claws shows that input channels with distinct odor tuning converge on individual MB neurons. We determined how these inputs interact to drive the cell to spike threshold using intracellular recordings to examine MB responses to optogenetically controlled input. Our results provide an elegant explanation for the characteristic selectivity of MB neurons: these cells receive different types of input, and require those inputs to be coactive in order to spike. These results establish the MB as an important site of integration in the fly olfactory system.

}, doi = {10.1038/nn.3547}, author = {Gruntman, Eyal and Turner, Glenn C} } @article {47219, title = {Integration of the olfactory code across dendritic claws of single mushroom body neurons.}, journal = {Nature Neuroscience}, volume = {16}, year = {2013}, month = {2013 Dec}, pages = {1821-9}, abstract = {

In the olfactory system, sensory inputs are arranged in different glomerular channels, which respond in combinatorial ensembles to the various chemical features of an odor. We investigated where and how this combinatorial code is read out deeper in the brain. We exploited the unique morphology of neurons in the Drosophila mushroom body, which receive input on large dendritic claws. Imaging odor responses of these dendritic claws revealed that input channels with distinct odor tuning converge on individual mushroom body neurons. We determined how these inputs interact to drive the cell to spike threshold using intracellular recordings to examine mushroom body responses to optogenetically controlled input. Our results provide an elegant explanation for the characteristic selectivity of mushroom body neurons: these cells receive different types of input and require those inputs to be coactive to spike. These results establish the mushroom body as an important site of integration in the fly olfactory system.

}, keywords = {Animals, Animals, Genetically Modified, Calcium, Dendrites, Drosophila, Drosophila Proteins, Electric Stimulation, Female, Luminescent Proteins, Membrane Potentials, Models, Neurological, Mushroom Bodies, Neurons, Odors, Olfactory Pathways, Patch-Clamp Techniques, Photic Stimulation, Rhodopsin, Synapses}, issn = {1546-1726}, doi = {10.1038/nn.3547}, author = {Gruntman, Eyal and Turner, Glenn C} }