Decoding odor quality and intensity in the Drosophila brain

To internally reflect the sensory environment, animals create neural maps encoding the external stimulus space. From that primary neural code relevant information has to be extracted for accurate navigation. We analyzed how different odor features such as hedonic valence and intensity are functionally integrated in the lateral horn (LH) of the vinegar fly, Drosophila melanogaster. We characterized an olfactory-processing pathway, comprised of inhibitory projection neurons (iPNs) that target the LH exclusively, at morphological, functional and behavioral levels. We demonstrate that iPNs are subdivided into two morphological groups encoding positive hedonic valence or intensity information and conveying these features into separate domains in the LH. Silencing iPNs severely diminished flies' attraction behavior. Moreover, functional imaging disclosed a LH region tuned to repulsive odors comprised exclusively of third-order neurons. We provide evidence for a feature-based map in the LH, and elucidate its role as the center for integrating behaviorally relevant olfactory information

Connectivity and computations in higher-order olfactory neurons in Drosophila

Understanding how odors are encoded in the brain is of fundamental importance to neurobiology. The first two stages of olfactory information processing have been relatively well studied in both vertebrates and invertebrates. However, the organizational principles of higher order olfactory representations remain poorly understood. Neurons in the first relay of the olfactory system segregate into glomeruli, each corresponding to an odorant receptor. Higher-order neurons can receive input from multiple glomeruli, but it is not clear how they integrate their inputs and generate stimulus selectivity

Consistent and Inconsistent Social Characteristics and the Determination of Power and Prestige Orders

The work reported here was significant in the generalization of the first theory of status characteristics and expectation states (Technical Report #12 and Berger et al., 1966). The first theory could only account for status generalization from a single characteristic; this paper reports experimental results for two status characteristics. Experimental data showed that the characteristics combined, which was incorporated in the theoretical extension to two characteristics published by Berger et al. (1974)

The Process of Status Evolution

This Technical Report discusses results from fifty nine 3 person groups. Although groups began with no induced status or expectation differentiation, about half showed participation inequality from the first 2-minute period and half developed inequality structures after some interaction. The task (coming up with an interesting task for groups to discuss) created high task focus and collective orientation

Precise Temperature Compensation of Phase in a Rhythmic Motor Pattern

Computational modeling and experimentation in a model system for network dynamics reveal how network phase relationships are temperature-compensated in terms of their underlying synaptic and intrinsic membrane currents

Participation in Heterogeneous and Homogeneous Groups: A Theoretical Integration

The authors define a behavior interchange pattern that can affect performance expectation states and behavior. This WP was published by the authors (1991)

Multi-Characteristic Status Situations and the Determination of Power and Prestige Order

This technical report builds on the research reported in Technical Report 32. It reports a second experiment investigating how two status characteristics affect expectations and power and prestige. The theoretical goal was to further compare predictions based on combining all status information and predictions based on "balancing" or ignoring some information. The combining assumption was later incorporated in the general theory

Neuronal mechanisms underlying innate and learned olfactory processing in Drosophila

Olfaction allows animals to adapt their behavior in response to different chemical cues in their environment. How does the brain efficiently discriminate different odors to drive appropriate behavior, and how does it flexibly assign value to odors to adjust behavior according to experience? This review traces neuronal mechanisms underlying these processes in adult Drosophila melanogaster from olfactory receptors to higher brain centers. We highlight neural circuit principles like lateral inhibition, segregation and integration of olfactory channels, temporal accumulation of sensory evidence, and compartmentalized synaptic plasticity underlying associative memory

Author response

We identified the neurons comprising the Drosophila mushroom body (MB), an associative center in invertebrate brains, and provide a comprehensive map describing their potential connections. Each of the 21 MB output neuron (MBON) types elaborates segregated dendritic arbors along the parallel axons of similar to 2000 Kenyon cells, forming 15 compartments that collectively tile the MB lobes. MBON axons project to five discrete neuropils outside of the MB and three MBON types form a feedforward network in the lobes. Each of the 20 dopaminergic neuron (DAN) types projects axons to one, or at most two, of the MBON compartments. Convergence of DAN axons on compartmentalized Kenyon cell-MBON synapses creates a highly ordered unit that can support learning to impose valence on sensory representations. The elucidation of the complement of neurons of the MB provides a comprehensive anatomical substrate from which one can infer a functional logic of associative olfactory learning and memory