This Week in The Journal
New Insights into Taste Information Processing Circuitry
Melissa S. Haley, Alfredo Fontanini, and Arianna Maffei
(see pages 7294–7306)
The gustatory cortex (GC) regulates taste information processing and consummatory decision-making. GC taste responses are reduced when the parvicellular region of the ventral posteromedial thalamic nucleus (VPMpc) is inactivated, and research has revealed that cortical inhibition may modulate GC integration of thalamic and limbic inputs. However, whether cortical inhibition modulates the VPMpc input into the GC is unexplored. In this issue, Haley et al. activated VPMpc inputs into the GC in slices using optogenetics to explore the synaptic properties of this input while investigating whether it is modulated by cortical inhibition. They found that VPMpc inputs are distributed across the GC but have layer- and cell-specific properties. They also found that GC responses to VPMpc activation are modulated by inhibitory GABA signaling through presynaptic and postsynaptic receptors. This insight into how inhibition modulates or gates the VPMpc–GC circuit is highly informative for our understanding of taste information processing and may aid in detecting novel treatment targets for disease states in which aberrant taste perception is a symptom.
Analyses of APL (green) morphology revealed 2–3 branches splitting from the primary neurite on both hemispheres. In this image, you can also see mushroom bodies (magenta) and neuropils (blue). These data were acquired with a 16× glycerol objective. Scale bar, 20 µm. Grid spacing, 20 µm. See Figure 3 for more information.
Novel Reward Circuit Discovered in Drosophila
Nino Mancini, Juliane Thoener, Esmeralda Tafani, Dennis Pauls, Oded Mayseless, et al.
(see pages 7393–7428)
Drosophila are a versatile animal research model in neuroscience for the ease with which they can be genetically manipulated and their low number of neurons. This has enabled breakthroughs in our understanding of neural circuit function. Because their larvae feed on sugary fruits, Drosophila are a particularly suitable model for investigating the neurogenetics of reward-learning and memory. In this issue, Mancini et al. investigated one of the most complex neurons in the larva brain: the anterior paired lateral neuron (APL). They used behavioral and connectomic analyses, optogenetics, calcium imaging, and pharmacology to investigate the role of this neuron in associating scents with reward. The authors provided an intricate account of the structure and connectivity of the APL and confirmed that it inhibits its cellular targets. But surprisingly, they also discovered that optogenetic activation of APL during odor presentation results in an odor-specific and reward-like associative memory. They further revealed that this may be due to activation of a dopamine-mediated mechanism. These findings uncover a novel mechanism for reward in Drosophila and validate the understanding that circuit function can be highly complex even in brains with very few neurons.
