A Dopamine-Modulated Neural Circuit Regulating Aversive Taste Memory in Drosophila

Abstract

Summary Taste memories allow animals to modulate feeding behavior in accordance with past experience and avoid the consumption of potentially harmful food [1]. We have developed a single-fly taste memory assay to functionally interrogate the neural circuitry encoding taste memories [2]. Here, we screen a collection of Split-GAL4 lines that label small populations of neurons associated with the fly memory center - the mushroom bodies (MB) [3]. Genetic silencing of PPL1 dopamine neurons disrupts conditioned, but not naïve feeding behavior, suggesting these neurons are selectively involved in the conditioned taste response. We identify two PPL1 subpopulations that innervate the MB α lobe and are essential for aversive taste memory. Thermogenetic activation of these dopamine neurons during training induces memory, indicating these neurons are sufficient for the reinforcing properties of bitter tastant to the MBs. Silencing of either the intrinsic MB neurons, or the output neurons from the α lobe, disrupts taste conditioning. Thermogenetic manipulation of these output neurons alters naïve feeding response, suggesting that dopamine neurons modulate the threshold of response to appetitive tastants. Taken together, these findings detail a neural mechanism underlying the formation of taste memory and provide a functional model for dopamine-dependent plasticity in Drosophila.

Motor control of fly feeding

“…It is thought that this neuron may inhibit feeding while the fly is walking. Probosic extension is also inhibited by certain output neurons of the mushroom bodies, which may aid in setting the threshold of proboscis extension in response to aversive taste conditioning (Masek et al 2015).…”

Gustatory processing and taste memory inDrosophila

“…This multi-level gustatory system is different from human taste organization and provides a mechanism to control the decision to ingest food. Experimentally, the application of different tastants to the proboscis and tarsi provides a system to investigate how different taste modalities are integrated and, more recently, describe the neural mechanisms of memory formation (Keene and Masek 2012, Kirkhart and Scott 2015, Masek et al 2015). …”

“…This single-fly assay is inexpensive and amenable to high throughput analysis. It is also accessible to optogenetic techniques that stimulate distinct populations of peripheral or central brain neurons (Keene and Masek 2012, Masek et al 2015) and adaptable for functional imaging. Furthermore, this assay is unique from other classical conditioning assays because both the reinforcing cue (quinine) and the conditioned stimulus (fructose) are tastants processed as the same basic sensory modality.…”

Implementation of Geodesic Active Contour Approach for Pigment Spots Segmentation on the Iris Surface

“…2.1. (2003) Geodesic active contour Roy et al (2007) Variational level sets Daugman (2003) Fourier-based approximation Schuckers et al (2007) Active shape models Pundlik et al (2008) Graph cuts Zuo and Schmid (2010) Ellipse fitting He et al (2013) Pulling and pushing model Du et al (2014) Scale invariants feature transform Masek et al (2015; Circular Hough transform Lim et al, 2014;Huang et al, 1990;Yuan et al (2005) Edge detection and Hough transform Huang et al (1990) Phase congruency and Hough transform Based on available documented literatures, Jillela and Ross (2013) had reported there is various iris segmentation approaches have been proposed to deal with the non-ideal eye image such as off-angled, occlusion and blurry motion situation as summarizes in Table 2.2. However, it is very rare to find documented publications on pigment spots.…”