![]() In their new paper, the researchers looked at the way flies respond to thirst, which hasn’t been studied much most of the work in flies has focussed on hunger. By studying the anatomy of reward in the fly, Waddell and his colleagues hope to shed some light on human yearnings. But it’s remarkably similar to ours in certain fundamental respects. Its neural anatomy is very different from ours in the details-flies and mammals are separated by hundreds of millions of years of evolution. There are about a hundred thousand neurons in the fruit-fly brain, versus nearly ninety billion in the human brain. Drosophila melanogaster has been a tiny laboratory workhorse for more than a century, ever since it helped prove the theory of chromosomal inheritance. The group, which is led by Scott Waddell, studies rewards, motivation, and memory in the comparatively simple brain of the fruit fly. The latest issue of the journal Nature Neuroscience includes an article by a group of researchers from the Centre for Neural Circuits and Behaviour, at Oxford. But, amid all the neural activity generated by such broad categories of behavior as liking, wanting, and learning, it’s hard to figure out where it all starts in the mammalian brain. Dopamine, a hormone secreted by certain neurons, is known to play a major role in pleasure and reward. In one recent review of the literature, Berridge notes reward-related activity in the orbitofrontal cortex, the anterior cingulate, and the insula, as well as in deeper, subcortical structures, such as the nucleus accumbens, the ventral pallidum, the ventral tegmentum, the amygdala, and some of the dopamine pathways between them. They get lost in whole South Sea archipelagoes of hot spots. So many brain areas light up in response to a sweet taste, a hit of intravenous cocaine, a jackpot win, or a subliminal glimpse of a smiley face that researchers can’t make much sense of what’s going on. But when scientists go hunting for these hot spots, using neural recordings and neuroimaging studies, they find them all over the place. Presumably, there are dedicated places in the brain-Berridge calls them “hedonic hot spots”-where the gloss of pleasure is painted on, where a certain sheen and glimmer is cast over life’s rewards. In other words, the experience of reward is generated from within as well as from without. ‘Wanting’ and ‘liking’ reactions are actively generated by neural systems that paint the desire or pleasure onto the sensation -as a sort of gloss painted on the sight, smell or taste.” “Our fundamental starting point,” he has written, “is that the temptation and pleasure of sweet, fatty, or salty foods arise actively within the brain, not just passively from physical properties of foods themselves. In the science of reward, Berridge’s framework is both influential and controversial. And, over the course of their lives, they will build up huge reservoirs of associations around whatever they like this is learning. (When they taste something bitter, they all open their mouths in a remarkably similar gape.) They will try to get more of what they like this is wanting. How and where do pleasure and motivation-the impulse to eat a piece of chocolate cake, say, or to resist it-arise in the brain? Berridge divides the components of reward into “liking,” “wanting,” and “learning.” When human newborns, young orangutans, chimpanzees, monkeys, or even rats and mice taste something sweet, for instance, they all stick out their tongues just a little this is liking. doi:10.3389/ Berridge, a psychologist at the University of Michigan, has spent more than thirty years trying to understand the biology of rewards. Perceptual Sensitivity and Response to Strong Stimuli Are Related. doi:10.1371/journal.pone.0150783īolders AC, Tops M, Band GPH, Stallen PJM. Age- and gender-related mean hearing threshold in a highly-screened population: The Korean National Health and Nutrition Examination Survey 2010–2012. ![]() A conceptual model of tactile processing across body features of size, shape, side, and spatial location. Olfaction as a soldier- a review of the physiology and its present and future use in the military. Personality and perceptions of common odors. ![]() ![]() The effects of age on sensory thresholds and temporal gap detection in hearing, vision, and touch. Humes LE, Busey TA, Craig JC, Kewley-Port D.
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