Hippocampus-lateral septum circuitry mediates foraging-related spatial memory in rats

ABSTRACTRemembering the location of a food or water source is essential for survival. Here we identify a hippocampal-septal neural circuit that is necessary for spatial memory based specifically on appetitive reinforcement. Both reversible and chronic disconnection of ventral hippocampus CA1 subregion (CA1v) projections to the lateral-septum (LS) using pathway-specific dual viral approaches impaired spatial memory retention for the location of either food or water reinforcement. However, disconnection of this pathway did not affect performance in an aversive escape-motivated spatial memory task that used the same apparatus and visuospatial cues. The selectivity of this pathway in mediating foraging-related spatial memory was further supported by results showing that CA1v-LS disconnection did not affect anxiety-like behavior, locomotor activity, or social and olfactory-based appetitive learning. To examine whether CA1v-LS mediation of foraging-related spatial memory involves collateral projections of CA1v neurons, we utilized virus-based neural pathway tracing analyses to identify the medial prefrontal cortex (mPFC) as a collateral target of LS-projecting CA1v neurons. However, functional disconnection of CA1v and mPFC did not affect appetitive spatial memory, thus further supporting the selectivity of CA1v-LS signaling for this behavior. The nucleus accumbens, lateral hypothalamic area, and other brain regions associated with food motivation and reward were identified as second-order targets of CA1v-LS signaling using a multisynaptic anterograde tracing approach. Collective results reveal that CA1v to LS communication plays a critical role in remembering an environmental location based on appetitive (food or water) but not aversive (escape) reinforcement, thus identifying a novel neural pathway regulating foraging-related memory processes.

Corrosion performance of steel reinforcement in concrete admixed with magnesium chloride and sulphate

Purpose Besides with a large amount of Na+ and Cl− ions in seawater, the presence of Mg+2 and SO4−2 ions builds more complex corrosion mechanism. This paper aims to investigate the corrosion of embedded reinforcement in concrete with the environment of both Cl− and SO4−2 anions associated Mg+2 cation. Design/methodology/approach The concrete specimens were prepared by using ordinary Portland cement (OPC), and OPC blended with metakaolin (MK) for water to cementitious material ratio (w/cm) 0.48 and 0.51. The concrete mixes were contaminated with the addition of MgCl2 alone and combined MgCl2 and MgSO4 in mix water. Reinforcement corrosion was evaluated by half-cell potential and corrosion current densities (Icorr) at regular intervals. Moreover, the influence of cementitious material type, salt type and w/cm ratio on electrical resistivity of concrete was also investigated. The statistical models were developed for electrical resistivity as a function of calcium to aluminium content ratio, compressive strength, w/cm ratio and age of concrete. Findings Although the corrosion initiation time increases in the concomitant presence of MgSO4 and MgCl2 as internal source compared to MgCl2, Icorr values are higher in both OPC and MK blended concrete. However, electrical resistivity decreased with addition of MgSO4. MK blended concrete performed better with increased resistivity, corrosion initiation time and decreased Icorr values. Originality/value This study reports statistical distributions for scattered Icorr of rebar in different concrete mixtures. Stepwise regression models were developed for resistivity by considering the interactions among different variables, which would help to estimate the resistivity through basic information.

CONSTRUCTION ENGINEERING AND CONSTRUCTION MATERIALS

Construction Engineering is very important part of Civil Engineering. We can’t think about a good and stable structure without good quality of construction. And the construction materials is also play an important role for any construction work. Construction engineering is a professional discipline that deals with the designing, planning, construction and management of infrastructures such as roads, tunnels, bridges, airports, railroads, facilities, buildings, dams, utilities and other projects. Civil Engineering is a related field that deals more with the practical aspects of projects. Construction engineers learn some of the design aspects similar to civil engineers as well as project site management aspects. Construction Engineers are heavily involved in the design and management/ allocation of funds in these projects. They are charged with risk analysis, costing and planning. Many types of building materials are used in the construction industry to create buildings and structures. KEYWORDS: Construction materials as like Brick, Stone, Cement, Lime-stone, Lime, Water, Reinforcement Steel, Wood etc.

Naloxone Decreases Responding for Conditioned Reinforcement in Rats

That opioids can mediate unconditioned reinforcement is well established, but there is little evidence indicating whether they modify conditioned reinforcement. Here, a tone which initially served as a discriminative stimulus for the availability of water reinforcement was established as a conditioned stimulus. When later given a choice between pressing a lever producing the tone (but not water) or one which produced no effect, rats chose the tone-producing lever 66% of the time. Naloxone (3.0 mg/kg) reduced overall responding and completely eliminated the preference for the tone-producing lever. Results are briefly discussed in terms of the importance of understanding mechanisms serving conditioned reinforcement.

Behavioral estimates of absolute threshold in rat

Dark-adapted thresholds of albino and pigmented rats were estimated using behavioral methods. Albino and pigmented rats who had been water deprived learned to bar press for water reinforcement when a light stimulus was presented. Absolute threshold was defined to be the light intensity at which bar pressing behavior was significantly modified by the presence of the light stimulus. Albino rats had an average threshold of −5.23 log cd/m2 and the pigmented rats had a threshold of −5.0 log cd/m2. These values are close to −5.3 log cd/m2, the psychophysical threshold of human observers in the same apparatus. Consistent with our earlier electrophysiology, these behavioral experiments provide no evidence for an albino/pigmented sensitivity difference. Comparisons are made between behavioral and electrophysiological determinations of absolute threshold in albino and pigmented rats. Thresholds determined behaviorally agree remarkably well with those derived from visual evoked potentials.