A new semi-theoretical thin layer model for modeling the air drying of cocoa beans with overnight tempering at ambient temperature was developed. The new model was a combination of the Page and ...two-term drying model. Results showed that the new model was found best described the drying process under the conditions tested (60, 70 and 80
°C). Effective diffusivities were found between 7.46
×
10
−11 and 1.87
×
10
−10
m
2/s. The Arrhenius constant and activation energy were estimated at 8.43
×
10
−4
m
2/s and 44.92
KJ/mol, respectively. Analyses of pH and cut test for bean quality showed that beans dried at 60
°C had lower acidity and good flavour quality as compared to other drying treatments.
•Muscarinic receptor (mAChR) activation promotes object memory destabilization.•The ubiquitin proteasome system (UPS) destabilizes synaptic proteins and memories.•M1 mAChR activation underlies the ...muscarinic effects on object memories.•UPS inhibition prevents memory destabilization prompted by M1 activation.•M1 mAChRs might stimulate the UPS via IP3 receptor-induced calcium release.
Consolidated memories can become destabilized during reactivation, resulting in a transient state of instability, a process that has been hypothesized to underlie long-term memory updating. Consistent with this notion, relatively remote memories, which are resistant to standard destabilization procedures, are reliably destabilized when novel information (i.e., the opportunity for memory updating) is present during reactivation. We have also shown that cholinergic muscarinic receptor (mAChR) activation can similarly destabilize consolidated object memories. Synaptic protein degradation via the ubiquitin proteasome system (UPS) has previously been linked to destabilization of fear and object-location memories. Given the role of calcium in regulating proteasome activity, we hypothesized that activation of cholinergic receptors, specifically M1 mAChRs, stimulates the UPS via inositol triphosphate receptor (IP3R)-mediated release of intracellular calcium stores to facilitate object memory destabilization. We present converging evidence for this hypothesis, which we tested using a modified spontaneous object recognition task for rats and microinfusions into perirhinal cortex (PRh), a brain region strongly implicated in object memory. We extend our previous findings by demonstrating that M1 mAChRs are necessary for novelty-induced object memory destabilization. We also show that proteasome inhibition or IP3R antagonism in PRh prevents object memory destabilization induced by novelty or M1 mAChR stimulation. These results establish an intracellular pathway linking M1 receptors, IP3Rs, and UPS activity to object memory destabilization and suggest a previously unacknowledged role for cholinergic signaling in long-term memory modification and storage.
We report several significant photodecomposition rates of methylene blue (MB) obtained before and after the refluxing process of own-synthesized two-dimensional (2D) zinc oxide (ZnO) nanopellets. ...Each photodecomposition rate of MB was found highly dependent on the weight of photocatalyst. The existing photodecomposition rate has been successfully improved to a factor of 22.0 times through refluxing process in excessive pyridine where the surface capping ligand (oleic acid) is removed from the 2D ZnO nanopellets. On the other hand, the refluxed photocatalyst (0.04
g) in this study was found to exhibit excellent recyclability up to three cycles. Furthermore, X-ray powder diffraction spectrums for the refluxed photocatatalyst, respectively, before and after three cycles of photocatalytic reactions, has generated the same patterns showing that the photocatalyst is stable and feasible to be used as an efficient photocatalyst material. Hence, these 2D ZnO nanopellets would provide a new alternative route as a highly efficient photocatalyst for wastewater treatment.
Studies were carried out to investigate the cocoa drying kinetics and compare the quality of the dried beans produced from sun and artificial hot air drying. Currently, these are the methods commonly ...used by cocoa farmers and plantations to dry cocoa beans. Drying trials were conducted in thin layer using natural sun light and by hot air inside an air-ventilated oven at air temperatures of 60
°C, 70
°C and 80
°C. Comparison was also made against freeze-dried cocoa beans for quality assessment. The quality attributes assessed were colour (
L*,
a*,
b* and hue angle), texture (hardness and fracturability) and polyphenol content (total polyphenols, epicatechin and catechin contents). Theoretical modelling was performed on the drying kinetics using Fick's law of diffusion and to determine the effective diffusivity values. Reasonable values were obtained for the coefficient of determination (
R
2) between the experimental and predicted moisture ratio data (range 0.9845–0.9976). Effective diffusivity values were found within the range reported in literatures (range 1.61
×
10
−10
m
2
s
−1–8.01
×
10
−11
m
2
s
−1). Quality assessment showed significant differences (
p
<
0.05) among the sun dried, freeze-dried and oven dried samples in texture, colour and polyphenol content.
We report the non-hydrolytic solution phase synthesis of two-dimensional zinc oxide (ZnO) nanopellets by using self-made organometallic compound (zinc (II) oleate, Zn(C
18H
33O
2)
2) as single ...precursor. Zn(C
18H
33O
2)
2 is prepared by ion exchange reaction between non-toxic fatty acid (palm oil extract) and ion Zn
2+. The controlling process of thermal pyrolysis of precursor is carried out under inert argon (Ar) atmosphere. This technique is very effective and reproducible in controlling the shape of ZnO semiconductor nanostructures. The as-synthesized ZnO nanocrystals are found in two-dimensionally well-faceted triangular and hexagonal thin pellet structures. Transmission electron micrograph(s) (TEM) show that the morphologies of ZnO nanopellets can be controlled by annealing duration. X-ray powder diffraction patterns reveal that all the peaks of ZnO nanopellets can be well indexed with standard hexagonal phase of ZnO crystal structure.
Rats, humans, and monkeys demonstrate robust crossmodal object recognition (CMOR), identifying objects across sensory modalities. We have shown that rats' performance of a spontaneous ...tactile-to-visual CMOR task requires functional integration of perirhinal (PRh) and posterior parietal (PPC) cortices, which seemingly provide visual and tactile object feature processing, respectively. However, research with primates has suggested that PRh is sufficient for multisensory object representation. We tested this hypothesis in rats using a modification of the CMOR task in which multimodal preexposure to the to-be-remembered objects significantly facilitates performance. In the original CMOR task, with no preexposure, reversible lesions of PRh or PPC produced patterns of impairment consistent with modality-specific contributions. Conversely, in the CMOR task with preexposure, PPC lesions had no effect, whereas PRh involvement was robust, proving necessary for phases of the task that did not require PRh activity when rats did not have preexposure; this pattern was supported by results from c-fos imaging. We suggest that multimodal preexposure alters the circuitry responsible for object recognition, in this case obviating the need for PPC contributions and expanding PRh involvement, consistent with the polymodal nature of PRh connections and results from primates indicating a key role for PRh in multisensory object representation. These findings have significant implications for our understanding of multisensory information processing, suggesting that the nature of an individual's past experience with an object strongly determines the brain circuitry involved in representing that object's multisensory features in memory.
The ability to integrate information from multiple sensory modalities is crucial to the survival of organisms living in complex environments. Appropriate responses to behaviorally relevant objects are informed by integration of multisensory object features. We used crossmodal object recognition tasks in rats to study the neurobiological basis of multisensory object representation. When rats had no prior exposure to the to-be-remembered objects, the spontaneous ability to recognize objects across sensory modalities relied on functional interaction between multiple cortical regions. However, prior multisensory exploration of the task-relevant objects remapped cortical contributions, negating the involvement of one region and significantly expanding the role of another. This finding emphasizes the dynamic nature of cortical representation of objects in relation to past experience.
Schizophrenia is associated with atypical multisensory integration. Rats treated sub-chronically with NMDA receptor antagonists to model schizophrenia are severely impaired on a tactile-to-visual ...crossmodal object recognition (CMOR) task, and this deficit is reversed by systemic nicotine. The current study assessed the receptor specificity of the ameliorative effect of nicotine in the CMOR task, as well as the potential for nicotinic receptor (nAChR) interactions with GABA and glutamate. Male Long-Evans rats were treated sub-chronically for 10 days with ketamine or saline and then tested on the CMOR task after a 10-day washout. Systemic nicotine given before the sample phase of the CMOR task reversed the ketamine-induced impairment, but this effect was blocked by co-administration of the GABAA receptor antagonist bicuculline at a dosage that itself did not cause impairment. Pre-sample systemic co-administration of the NMDA receptor antagonist MK-801 did not block the remediating effect of nicotine in ketamine-treated rats. The selective α7 nAChR agonist GTS-21 and α4β2 nAChR agonist ABT-418 were also tested, with only the latter reversing the ketamine impairment dose-dependently; bicuculline also blocked this effect. Similarly, infusions of nicotine or ABT-418 into the orbitofrontal cortex (OFC) reversed the CMOR impairment in ketamine-treated rats, and systemic bicuculline blocked the effect of intra-OFC ABT-418. These results suggest that nicotine-induced agonism of α4β2 nAChRs within the OFC ameliorates CMOR deficits in ketamine-treated rats via stimulation of the GABAergic system. The findings of this research may have important implications for understanding the nature and potential treatment of cognitive impairment in schizophrenia.
•Multisensory integration (MSI) is essential to everyday behavior.•The neural substrates of MSI are poorly understood.•We review non-human studies of MSI using crossmodal object recognition ...tasks.•This research reveals roles for various cortical regions and neurochemical systems.
The ability to integrate information from different sensory modalities to form unique multisensory object representations is a highly adaptive cognitive function. Surprisingly, non-human animal studies of the neural substrates of this form of multisensory integration have been somewhat sparse until very recently, and this may be due in part to a relative paucity of viable testing methods. Here we review the historical development and use of various “crossmodal” cognition tasks for non-human primates and rodents, focusing on tests of “crossmodal object recognition”, the ability to recognize an object across sensory modalities. Such procedures have great potential to elucidate the cognitive and neural bases of object representation as it pertains to perception and memory. Indeed, these studies have revealed roles in crossmodal cognition for various brain regions (e.g., prefrontal and temporal cortices) and neurochemical systems (e.g., acetylcholine). A recent increase in behavioral and physiological studies of crossmodal cognition in rodents augurs well for the future of this research area, which should provide essential information about the basic mechanisms of object representation in the brain, in addition to fostering a better understanding of the causes of, and potential treatments for, cognitive deficits in human diseases characterized by atypical multisensory integration.
According to the memory-enhancing hypothesis of addictive drugs, post-training administration of cocaine should enhance consolidation and thus facilitate learning. This hypothesis has not been tested ...in appetitive tasks reinforced by sucrose.
The current study assessed the effect of post-training cocaine administration on the acquisition of a win-stay task, and modulation of this effect by co-administration of diazepam. Male Sprague–Dawley rats (n=63) were trained for 5days on a win-stay task performed on an 8-arm radial maze, and were administered cocaine (0, 2.5, 7.5 or 20mg/kg), diazepam (1mg/kg), or cocaine (7.5mg/kg)+diazepam (1mg/kg) immediately following each training session. Post-training cocaine caused dose-dependent impairments that appeared linked to the development of cocaine-induced sucrose taste avoidance and/or cocaine-induced anxiety. When it was attempted to modify these learned side effects of cocaine by co-administration of diazepam, it was observed that the drug combination slowed task completion and reduced overall number of nose pokes.
These findings suggest that post-training cocaine can alter behavior on appetitive tasks through learned motivational deficits rather than through a selective action on memory consolidation. The implications for the memory-enhancing hypothesis of addictive drugs are discussed.
•The effect of post-training administration of cocaine was studied on acquisition of a win stay task•Post-training cocaine caused dose-dependent impairments•Diazepam compounded the impairments caused by cocaine•These impairments were likely not due to impaired memory consolidation
Rationale
It has been proposed that drugs of abuse reinforce behavior partly, or wholly, because they facilitate learning by enhancing memory consolidation. Cocaine can clearly serve as a reinforcer, ...but its effect on learning has not been fully characterized.
Objectives
To explore the effects of different regimens of pre- and post-training cocaine administration on win-stay and object learning.
Methods
Cocaine naïve and cocaine pre-exposed (30 mg/kg/day, ×5 days followed by 7 days drug-free) male Sprague-Dawley rats received cocaine (0, 1, 2.5, 7.5, or 20 mg/kg, i.p.) immediately following training on a win-stay task in a radial maze or following the sample phase of an object learning task. Win-stay performance was also assessed in tests of extinction and after a set shift.
Results
Post-training cocaine did not improve accuracy on the win-stay task and produced performance deficits at 20 mg/kg. These deficits were attenuated by prior cocaine exposure. There was indirect evidence of facilitated learning in extinction and set shift tests, but the effective dosage was different (2.5 and 7.5 mg/kg, respectively). Post-training cocaine produced dose-dependent improvements in object learning.
Conclusion
Post-training cocaine administration can facilitate learning, but this effect is highly dependent on the dose and the type of task employed.
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