The fly Drosophila melanogaster can discriminate and remember visual landmarks. It analyses selected parts of its visual environment according to a small number of pattern parameters such as size, colour or contour orientation, and stores particular parameter values. Like humans, flies recognize patterns independently of the retinal position during acquisition of the pattern (translation invariance). Here we show that the central-most part of the fly brain, the fan-shaped body, contains parts of a network mediating visual pattern recognition. We have identified short-term memory traces of two pattern parameters--elevation in the panorama and contour orientation. These can be localized to two groups of neurons extending branches as parallel, horizontal strata in the fan-shaped body. The central location of this memory store is well suited to mediate translational invariance.
The world is permanently changing. Laboratory experiments on learning and memory normally minimize this feature of reality, keeping all conditions except the conditioned and unconditioned stimuli as constant as possible. In the real world, however, animals need to extract from the universe of sensory signals the actual predictors of salient events by separating them from non-predictive stimuli (context). In principle, this can be achieved if only those sensory inputs that resemble the reinforcer in their temporal structure are taken as predictors. Here we study visual learning in the fly Drosophila melanogaster, using a flight simulator, and show that memory retrieval is, indeed, partially context-independent. Moreover, we show that the mushroom bodies, which are required for olfactory but not visual or tactile learning, effectively support context generalization. In visual learning in Drosophila, it appears that a facilitating effect of context cues for memory retrieval is the default state, whereas making recall context-independent requires additional processing.
Operant behavior is studied in tethered Drosophila flies using visual motion, heat or odour as operandum and yaw torque, thrust or direction of flight as operans in various combinations (Fig. 1). On the basis of these results a conceptual framework of operant behavior is proposed: (1) It requires a goal (desired state) of which the actual state deviates. (2) To attain the goal a range of motor programs is activated (initiating activity, see Fig. 7). (3) Efference copies of the motor programs are compared to the sensory input referring to the deviation from the desired state (e.g. by cross-correlation). (4) In case of a significant coincidence the respective motor program is used to modify the sensory input in the direction towards the goal. (5) Consistent control of a sensory stimulus by a behavior may lead to a more permanent behavioral change (conditioning). In this scheme operant activity (1-4) and operant conditioning (1-5) are distinguished.
Background. The occurrence of a new skin disorder exactly at the site of another one, already healed and unrelated, was first described in 1955 that we are dealing with a dermatologic phenomenon and established a precise definition for this phenomenon. Fiftyeight cases corresponding to the definition of this phenomenon have been reported until now.Methods. The new phenomenon, for which the term "isotopic response" has been suggested, has been defined. Cases corresponding to the definition have been analyzed with special emphasis on the diseases involved, the time intervals, and the locations of the diseases. Eight new cases are described. Results.A total of 58 cases of isotopic response have been described. The first disease in most of the patients was herpes zoster; in three cases it was herpes simplex, in two varicella, and in one, thrombophlebitis. The second disease, which appeared exactly at the site of the first, already healed disease, was in most reported cases a carcinoma (26 cases, in particular 15 cases of breast carcinoma, 5 basal cell carcinomas (BCC), 4 squamous cell carcinomas (sec), 2 basosquamous carcinomas), or granuloma annulare (16 cases). Additional diseases were Kaposi's sarcoma (2 cases), pseudolymphoma (2 cases), sarcoid (2 cases), tinea (2 cases), tuberculoid and vasculitis granuloma (1 case), angiosarcoma, metastasis, Bowen's disease, Iymphoma, leukemia cutis, and acne (1 case each). The diseases did not show any predilection for a particular location. The interval between the first and second disease was extremely variable (ranging from days to years) and showed no particular features.In the eight additional cases described in the present report, the first disease was herpes simplex (6 cases) or herpes zoster (2 cases). The second disease was viral warts (3 cases) or squamous cell carcinoma (2 cases). Additional diseases were furunculosis, contact dermatitis, and molluscum contagiosum (1 case each).Conclusions. The new term, "isotopic response," describes the occurrence of a new skin disorder at the site of another, unrelated, and already healed skin disease.It is suggested that the term "isotopic response" be included in the lexicon (glossary) of dermatology.Introducing the new term and classifying all the cases under a single key word, will make it possible to locate and collect them easily and to search for the mechanism underlying this phenomenon. Int J Dermatol 1995; 34:341-348 Tattoo art by Mike "Rollo" Malone of the Ghina Sea Tattoo Studio, Honolulu, Hawaii, from the collection of Norman Goldstein, M.D. (dubbed the "tattoo guru" by Gharles Gruppa, M.D.)-The World of Tattoos, Honolulu, Hawaii.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.