Despite its ubiquity and significance, behavioral habituation is poorly understood in terms of the underlying neural circuit mechanisms. Here, we present evidence that habituation arises from potentiation of inhibitory transmission within a circuit motif commonly repeated in the nervous system. In Drosophila, prior odorant exposure results in a selective reduction of response to this odorant. Both short-term (STH) and long-term (LTH) forms of olfactory habituation require function of the rutabaga-encoded adenylate cyclase in multiglomerular local interneurons (LNs) that mediate GABAergic inhibition in the antennal lobe; LTH additionally requires function of the cAMP response element-binding protein (CREB2) transcription factor in LNs. The odorant selectivity of STH and LTH is mirrored by requirement for NMDA receptors and GABA A receptors in odorant-selective, glomerulus-specific projection neurons (PNs). The need for the vesicular glutamate transporter in LNs indicates that a subset of these GABAergic neurons also releases glutamate. LTH is associated with a reduction of odorant-evoked calcium fluxes in PNs as well as growth of the respective odorant-responsive glomeruli. These cellular changes use similar mechanisms to those required for behavioral habituation. Taken together with the observation that enhancement of GABAergic transmission is sufficient to attenuate olfactory behavior, these data indicate that habituation arises from glomerulus-selective potentiation of inhibitory synapses in the antennal lobe. We suggest that similar circuit mechanisms may operate in other species and sensory systems.abituation is a specific form of implicit learning in which repeated exposure to an unreinforced stimulus results in a decreased behavioral response (1-3). By filtering out such constant sensory input, habituation enhances an animal's ability to focus its cognitive resources on novel or salient features of the environment. Thus, habituation serves as a building block for normal cognition (2, 4). Although it has been studied in many different contexts, causal connections between mechanisms, neuronal changes, and behavioral habituation have not been clearly identified (2). Given our current understanding, it remains unclear whether similar or distinct mechanisms underlie different forms of habituation; also unclear is how these mechanisms compare with those mechanisms used in consolidation or extinction of associative memory (1, 5).The olfactory system provides an experimentally accessible circuit in which to analyze mechanisms that underlie different timescales of behavioral habituation (4, 6, 7). Particularly useful is the adult Drosophila olfactory system, which has organization similar to that of mammals (8, 9). Here, olfactory sensory neurons (OSNs) expressing a single type of functional odorant receptor molecules (ORs) send axons to the antennal lobe and synapse onto (i) glomerulus-specific projection neurons (PNs) that project to the mushroom body and lateral horn, (ii) multiglomerular local interneurons (LNs...
The WIN can be used with children as young as 6 years of age; however, age-specific ranges of normal recognition performance must be used.
A quaculture, 34 (1 9 8 3 ) 2 8 7-30 1 T he Indian pearl oyster Pinctada fucata w as spawned in the laboratory and the larvae w ere successfully reared to spat setting under tropical con dition s. T h e larve grow s through the straight-hinge, u m bo, eye sp ot and pediveliger stages in the pelagic phase b efore m etam orphosing to plantigrade and setting on a substratum as spat, and these stages are described. Large differences were n oticed in larval grow th w ithin and betw een fou r rearing experim ents. Isochrysis galbana was used as standard fo o d th roughou t larval rearing at a cell concentration range 8 0 -350/jul. Spatfall occu rred on day 24-32 o n a variety o f substrata. The highest density o f 4 .7 1 /cm * was observed on fibreglass tank b o tto m . G row th o f P. fucata larvae appears to be a step fu n ction , and that o f spat u p to 13 weeks describes a curvilinear form . IN TR O D U C TIO NFollow ing the developm ent o f techniques fo r farming o f pearl oyster Pinctada fucata and production o f cultured pearls in India (Alagarswami, 19 7 4 ), it became im portant to breed the species artificially as the popula tions in the natural beds display drastic fluctuations (Alagarswami and Qasim, 1973). Spat collection in inshore areas and bays yields only small quantities which com prise several species o f pearl oysters with a low per centage o f P. fucata (Alagarswami, 19 7 7 ). M ethods fo r controlled spawn ing o f pearl oyster were developed earlier (Alagarswami et al., 1980a) and larval rearing cou ld be carried o u t only up to the straight-hinge stage (Ala garswami et al., 1980b). Subsequently success has been achieved in produc tion o f pearl oyster spat in the experiments described in this paper.The few works on breeding o f the Japanese pearl oyster (Kobayashi, 0 0 4 4 -8 4 8 6 /8 3 /$ 0 3 .0 0
Reef associated fishes landed by hooks and lines at Mandapam landing centre in Ramanathapuram District, Tamil Nadu for a period of four years from October 2008 to May 2012 were studied based on fortnightly samplings. The hook and line fishing is seasonal in Gulf of Mannar and lasts for six months annually from October - November to April - May, as this area remains rough during the rest of the year. The average annual landing of fish during the study period was 171 t with a peak of 295 t in 2008-09 and showed a decline since then. A total of 32 species of reef associated fishes belonging to 14 families were landed. Among them, Sphyraena barracuda contributed the maximum with a share of 42% followed by Caranx heberi (15%). Family-wise landings indicated the dominance of Sphyraenidae (46%). The diversity index (H’) was the highest during 2008-09 and the evenness of distribution of individuals among different species did not show significant variation in different years. Funnel plots of average taxonomic distinctness (∆+ ) and variation in taxonomic distinctness (λ+ ) indicated that the values in most of the years are within the normal limits.
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