Andrew M Dacks

West Virginia University | WVU · Department of Biology

Serotonin(5–HT) is known to modulate early development during critical periods when experience drives heightened levels of plasticity in neurons. Here, we take advantage of the genetically tractable olfactory system of Drosophila to investigate how serotonin modulates critical period plasticity in the CO2 sensing circuit of fruit flies. Our study r...

Natural behaviors are a coordinated symphony of motor acts that drive reafferent (self-induced) sensory activation. Individual sensors cannot disambiguate exafferent (externally induced) from reafferent sources. Nevertheless, animals readily differentiate between these sources of sensory signals to carry out adaptive behaviors through corollary dis...

Neural networks have an extensive ability to change in response to environmental stimuli. This flexibility peaks during restricted windows of time early in life called critical periods. The ubiquitous occurrence of this form of plasticity across sensory modalities and phyla speaks to the importance of critical periods for proper neural development...

Sensory systems are dynamically adjusted according to the animal's ongoing needs by neuromodulators, such as neuropeptides. Neuropeptides are often widely-distributed throughout sensory networks, but it is unclear whether such neuropeptides uniformly modulate network activity. Here, we leverage the Drosophila antennal lobe (AL) to resolve whether m...

Neural networks must be able to flexibly process information under different conditions. To this end, networks frequently rely on uniform expression of modulatory receptors by distinct classes of neurons to fine tune the computations supported by each neuronal class. In this study, we explore the consequences of heterogeneous, rather than uniform,...

Natural behaviors are a coordinated symphony of motor acts which drive self-induced or reafferent sensory activation. Single sensors only signal presence and magnitude of a sensory cue; they cannot disambiguate exafferent (externally-induced) from reafferent sources. Nevertheless, animals readily differentiate between these sources of sensory signa...

Sensory systems rely on neuromodulators, such as serotonin, to provide flexibility for information processing as stimuli vary, such as light intensity throughout the day. Serotonergic neurons broadly innervate the optic ganglia of Drosophila melanogaster, a widely used model for studying vision. It remains unclear whether serotonin modulates the ph...

Aedes aegypti and Anopheles coluzzii mosquitoes exhibit diurnal and nocturnal behaviors, respectively. Baik et al. reveal the clock network architecture underlying each species' light preferences.

Aedes aegypti and Anopheles coluzzii mosquitoes exhibit diurnal and nocturnal behaviors, respectively. Baik et al. reveal the clock network architecture underlying each species’ light preferences.

Serotonergic neurons project widely throughout the brain to modulate diverse physiological and behavioral processes. However, a single cell resolution understanding of the connectivity of serotonergic neurons is currently lacking. Using a whole-brain EM dataset of a female Drosophila, we comprehensively determine the wiring logic of a broadly proje...

The serotonergic system has been widely studied across animal taxa and different functional networks. This modulatory system is therefore well-positioned to compare the consequences of neuromodulation for sensory processing across species and modalities at multiple levels of sensory organization. Serotonergic neurons that innervate sensory networks...

Serotonergic neurons modulate diverse physiological and behavioral processes in a context-dependent manner, based on their complex connectivity. However, their connectivity has not been comprehensively explored at a single-cell resolution. Using a whole-brain EM dataset we determined the wiring logic of a broadly projecting serotonergic neuron (the...

Serotonin plays different roles across networks within the same sensory modality. Previously, we used whole-cell electrophysiology in Drosophila to show that serotonergic neurons innervating the first olfactory relay are inhibited by odorants (Zhang and Gaudry, 2016). Here we show that network-spanning serotonergic neurons segregate information abo...

Sensory systems rely on neuromodulators, such as serotonin, to provide flexibility for information processing in the face of a highly variable stimulus space. Serotonergic neurons broadly innervate the optic ganglia of Drosophila melanogaster , a widely used model for studying vision. The role for serotonergic signaling in the Drosophila optic lobe...

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 labelin...

Broad neuronal classes are surprisingly heterogeneous across many parameters, and subclasses often exhibit partially overlapping traits including transmitter coexpression. However, the extent to which transmitter coexpression occurs in predictable, consistent patterns is unknown. Here, we demonstrate that pairwise coexpression of GABA and multiple...

Significance Across vertebrates and invertebrates, corollary discharge circuits (CDCs) project to and inform sensory networks about an animal’s movements, which directly impact sensory processing. Failure of CDCs likely underlie sensory hallucinations in schizophrenia, Parkinson’s disease, and dyspnea, highlighting the fundamental importance of CDC...

Neuromodulation is a ubiquitous feature of neural systems, allowing flexible, context specific control over network dynamics. Neuromodulation was first described in invertebrate motor systems and early work established a basic dichotomy for neuromodulation as having either an intrinsic origin (i.e., neurons that participate in network coding) or an...

Nervous systems must adapt to shifts in behavioural ecology. One form of adaptation is neural exaptation, in which neural circuits are co-opted to perform additional novel functions. Here, we describe the co-option of a motor-to-somatosensory circuit into an olfactory network. Many moths beat their wings during odour-tracking, whether walking or fl...

Heterogeneity of individual neurons within a population expands the computational power of the entire neural network. However, the organizing principles that support heterogeneity within a neuronal class are often poorly understood. Here, we focus on a highly heterogeneous population of local interneurons whose traits co-vary seemingly at random. W...

Modulatory neurons project widely throughout the brain, dynamically altering network processing based on an animal’s physiological state. The connectivity of individual modulatory neurons can be complex, as they often receive input from a variety of sources and are diverse in their physiology, structure, and gene expression profiles. To establish b...

Neuromodulation confers flexibility to anatomically-restricted neural networks so that animals are able to properly respond to complex internal and external demands. However, determining the mechanisms underlying neuromodulation is challenging without knowledge of the functional class and spatial organization of neurons that express individual neur...

Often distinct elements serve similar functions within a network. However, it is unclear whether this network degeneracy is beneficial, or merely a reflection of tighter regulation of overall network performance relative to individual neuronal properties. We review circumstances where data strongly suggest that degeneracy is beneficial in that it m...

Transmission, critical to the establishment and persistence of host-associated microbiotas, also exposes symbionts to new environmental conditions. With horizontal transmission, these different conditions represent major lifestyle shifts. Yet, genome-wide analyses of how microbes adjust their transcriptome towards these dramatic shifts remain under...

Neural circuits projecting information from motor to sensory pathways are common across sensory domains. These circuits typically modify sensory function as a result of motor pattern activation; this is particularly so in cases where the resultant behavior affects the sensory experience or its processing. However, such circuits have not been observ...

The release of neuromodulators by widely projecting neurons often allows sensory systems to alter how they process information based on the physiological state of an animal. Neuromodulators alter network function by changing the biophysical properties of individual neurons and the synaptic efficacy with which individual neurons communicate. However...

Transmission plays a key role in the evolution of symbiosis. Mixed mode transmission combines horizontal and vertical mechanisms for symbiont acquisition. However, features that enable mixed transmission are poorly understood. Here, we determine the mechanistic basis for the recruitment of the beneficial bacterium, Aeromonas veronii by the leech, H...

Supplementary Information for Hitchhiking of Host Biology by Beneficial Symbionts Enhances Transmission

Neuromodulation, the alteration of individual neuron response properties, has dramatic consequences for neural network function and is a phenomenon observed across all brain regions and taxa. However, the mechanisms underlying neuromodulation are made complex by the diversity of neuromodulatory receptors expressed within a neural network. In this s...

Phylogenetic analysis of serotonin receptors from insects (I) and vertebrates (V). The figure is arbitrarily rooted on the vertebrate 5-HT3 clade, but should be treated as unrooted. Note the reconstruction of the 5-HT2 clade uniting both insect and vertebrate versions of these receptors. (TIF)

List of all receptor sequences used for phylogenetic analysis. (DOCX)

Behavioral states often preferentially enhance specific classes of behavior and suppress incompatible behaviors. In the nervous system, this may involve upregulation of the efficacy of neural modules that mediate responses to one stimulus and suppression of modules that generate antagonistic or incompatible responses to another stimulus. In Aplysia...

Neurotransmitters can have diverse effects that occur over multiple timescales often making the consequences of neurotransmission difficult to predict. To explore the consequences of this diversity we used the buccal ganglion of Aplysia to examine the effects of GABA release by a single interneuron, B40, on the intrinsic properties and motor output...

Behavior is a product of both the stimuli encountered and the current internal state. At the level of the nervous system, the internal state alters the biophysical properties of, and connections between, neurons establishing a "network state." To establish a network state, the nervous system must be altered from an initial default/resting state, bu...

The simplicity and accessibility of the olfactory systems of insects underlie a body of research essential to understanding not only olfactory function but also general principles of sensory processing. As insect olfactory neurobiology takes advantage of a variety of species separated by millions of years of evolution, the field naturally has yield...

Local interneurons (LNs) play important roles in shaping and modulating the activity of output neurons in primary olfactory centers. Here, we studied the morphological characteristics, odor responses, and neurotransmitter content of LNs in the antennal lobe (AL, the insect primary olfactory center) of the moth Manduca sexta. We found that most LNs...

The structure of the brain is a consequence of selective pressures and the ancestral brain structures modified by those pressures. The Hymenoptera are one of the most behaviorally complex insect orders, and the olfactory system of honeybees (one of the most derived members) has been extensively studied. To understand the context in which the olfact...

Neural networks receive input that is transformed before being sent as output to higher centers of processing. These transformations are often mediated by local interneurons (LNs) that influence output based on activity across the network. In primary olfactory centers, the LNs that mediate these lateral interactions are extremely diverse. For insta...

Current knowledge of the olfactory system of. Manduca sexta is discussed within the context of the natural history of this model organism. The anatomy of the olfactory system is described progressing from the antennas to the antennal lobes and then to higher centers of olfactory processing in the brain. The principles of olfactory information proce...

Visual scenes comprise enormous amounts of information from which nervous systems extract behaviorally relevant cues. In most model systems, little is known about the transformation of visual information as it occurs along visual pathways. We examined how visual information is transformed physiologically as it is communicated from the eye to higher...

The mechanisms of processing a visual scene involve segregating features (such as color) into separate information channels at different stages within the brain, processing these features, and then integrating this information at higher levels in the brain. To examine how this process takes place in the insect brain, we focused on the medulla, an a...

Sensory systems must be able to extract features of environmental cues within the context of the different physiological states of the organism and often temper their activity in a state-dependent manner via the process of neuromodulation. We examined the effects of the neuromodulator serotonin on a well-characterized sensory circuit, the antennal...

Animals use vision to perform such diverse behaviors as finding food, interacting socially with other animals, choosing a mate, and avoiding predators. These behaviors are complex and the visual system must process color, motion, and pattern cues efficiently so that animals can respond to relevant stimuli. The visual system achieves this by dividin...

The nervous system copes with variability in the external and internal environment by using neuromodulators to adjust the efficacy of neural circuits. The role of serotonin (5HT) as a neuromodulator of olfactory information processing in the antennal lobe (AL) of Manduca sexta was examined using multichannel extracellular electrodes to record the r...

Serotonin (5-hydroxytryptamine; 5HT) functions in insects as a neurotransmitter, neuromodulator, and neurohormone. In the sphinx moth Manduca sexta, each of the paired antennal lobes (ALs; the primary olfactory centers in the insect brain) has one 5HT-immunoreactive (5HT-ir) neuron that projects into the protocerebrum, crosses the posterior midline...

Serotonin and octopamine (OA) are biogenic amines that are active throughout the nervous systems of insects, affecting sensory processing, information coding and behavior. As an initial step towards understanding the modulatory roles of these amines in olfactory processing we cloned two putative serotonin receptors (Ms5HT1A and Ms5HT1B) and one put...

Octopamine is a neuroactive monoamine that functions as a neurohormone, a neuromodulator, and a neurotransmitter in many invertebrate nervous systems, but little is known about the distribution of octopamine in the brain. We therefore used a monoclonal antibody to study the distribution of octopamine-like immunoreactivity in the brain of the hawkmo...

The role of serotonin in controlling feeding in flesh flies is examined. Amount of feeding was recorded over 6 h for flies injected with serotonin or saline. The proportion of time spent on various behaviors over a period of 1 h was recorded after the injection of serotonin or saline or no injection. Corresponding electrophysiological measurements...