Biology subjects

Nitabach, M.

Publications and source records attributed to Nitabach, M..

3 recordsLinked to original sources

bioRxiv2020

A neuronal ensemble encoding adaptive choice during sensory conflict

Feeding decisions are fundamental to survival, and decision making is often disrupted in disease, yet the neuronal and molecular mechanisms of adaptive decision making are not well understood. Here we show that neural activity in a small population of neurons projecting to the fan-shaped body higher-order central brain region of Drosophila represents final food choice during sensory conflict. We found that hungry flies made tradeoffs between appetitive and aversive values of food in a decision making task to choose bittersweet food with high sucrose concentration, but adulterated with bitter quinine, over sweet-only food with less sucrose. Using cell-specific optogenetics and receptor RNAi knockdown during the decision task, we identified an upstream neuropeptidergic and dopaminergic network that relays internal state and other decision-relevant information, such as valence and previous experience, to a specific subset of fan-shaped body neurons. Importantly, calcium imaging revealed that these neurons were strongly inhibited by the taste of the rejected food choice, suggesting that they encode final behavioral food choice. Our findings reveal that fan-shaped body taste responses to food choices are determined not only by taste quality, but also by previous experience (including choice outcome) and hunger state, which are integrated in the fan-shaped body to encode the decision before relay to downstream motor circuits for behavioral implementation. Our results uncover a novel role for the fan-shaped body in choice encoding, and reveal a neural substrate for sensory and internal state integration for decision making in a genetically tractable model organism to enable mechanistic dissection at circuit, cellular, and molecular levels.

neuroscience↗

bioRxiv2020

Cholinergic relay from punishment- to reward-encoding dopamine neurons signals punishment withdrawal as reward in Drosophila

Animals form and update learned associations between otherwise neutral cues and aversive outcomes to predict and avoid danger in changing environments. When a cue later occurs without punishment, this unexpected withdrawal of aversive outcome is encoded as reward, via activation of reward-encoding dopaminergic neurons. Using real-time in vivo functional imaging, optogenetics, behavioral analysis, and electron-microscopy, we identify the neural mechanism through which Drosophila reward-encoding dopaminergic neurons are activated when an olfactory cue is unexpectedly no longer paired with electric shock punishment. Reduced activation of punishment-encoding dopaminergic neurons relieves depression of synaptic inputs to cholinergic neurons, which in turn synaptically increase odor responses of reward-encoding dopaminergic neurons to decrease odor avoidance. These studies reveal for the first time how an indirect excitatory cholinergic synaptic relay from punishment- to reward-encoding dopaminergic neurons encodes the absence of a negative as a positive, revealing a general circuit motif for unlearning aversive memories that could be present in mammals.

neuroscience↗

bioRxiv2016

C. elegans detect the color of pigmented food sources to guide foraging decisions.

Here we establish that, contrary to expectations, Caenorhabditis elegans nematode worms possess a color discrimination system despite lacking any opsin or other known visible light photoreceptor genes. We found that white light guides C. elegans foraging decisions away from harmful bacteria that secrete a blue pigment toxin. Absorption of amber light by this blue pigment toxin alters the color of light sensed by the worm, and thereby triggers an increase in avoidance. By combining narrow-band blue and amber light sources, we demonstrated that detection of the specific blue:amber ratio by the worm guides its foraging decision. These behavioral and psychophysical studies thus establish the existence of a color detection system that is distinct from those of other animals.

neuroscience↗