Biology subjects

Merlo, E.

Publications and source records attributed to Merlo, E..

5 recordsLinked to original sources

bioRxiv2025

The status of human goal-directed actions after manipulations of the action-outcome contingency

Goal-directed actions are those performed with the expectation of producing a specific outcome and are therefore sensitive to changes in the outcomes current value without re-experiencing the action-outcome contingency. Disrupting the action-outcome association by a number of interventions can reduce responding, but whether such interventions also affect the goal-directedness of human responses remains unknown. We trained participants to perform different actions for two distinct outcomes in two groups. One group experienced extinction (i.e., complete suspension of outcome delivery for a specific previously rewarded action) whereas the other was given non-contingent training (i.e., outcomes were presented independently of responding). Goal-directed control was tested by outcome devaluation, making one of the two outcomes less desirable, and responding was then tested in the absence of outcome presentations. Despite having been significantly reduced in both groups by extinction and non-contingent training, responding remained sensitive to outcome value, suggesting that human goal-directed behavior is resistant to action-outcome contingency interventions. We discuss these results in light of recent theories of goal-directed behavior.

animal behavior and cognition↗

bioRxiv2024

Translating human drug use patterns into rat models: exploring spontaneous interindividual differences via refined drug self-administration procedures

Heroin and cocaine users tailor their dosage and frequency of use, as well as their method of administration, to maximize the drugs pleasurable effects and prevent withdrawal symptoms. On the other hand, many preclinical self-administration and choice experiments employ fixed unit doses and mandatory timeouts after doses (known as discrete dimension procedures). These restrictions fail to consider the distinct pharmacokinetic properties of heroin and cocaine, leading to uniform and comparable behaviors (including drug-taking patterns). This uniformity contrasts sharply with the significantly different ways humans use heroin and cocaine, which are characterized by highly individualized drug use behaviors. Here, we introduce a no-timeout procedure that overcomes this limitation (continuous dimension procedure). We analyzed the heroin and cocaine taking- and seeking-patterns and estimated drug-brain levels in the presence or absence of timeout between drug injections. We further assessed how absence of timeout and the availability of drug or social peer (access time to the two rewards) affect drug preference. Removing the timeout had a profound effect on pattern of heroin taking and seeking, promoting the emergence of burst-like drug intake and social withdrawal as revealed by a discrete choice procedure. On the other hand, timeout removal had a lesser impact on cocaine taking and seeking and did not impact social preference. By removing timeout during self-administration and increasing the access time during choice resulted in a self-administration procedure that more closely mimic human heroin intake, offering a platform to identify novel medications.

neuroscience↗

bioRxiv2020

The relic ecosystem of Gymnosporia senegalensis (Lam.) Loes. in an agricultural plastic sea: past, present and future scenarios

Gymnosporia senegalensis is a shrub belonging to the Celastraceae family, which is native to tropical savannahs. Its only European populations are distributed discontinuously along the south-eastern coast of the Iberian Peninsula, forming plant communities with great ecological value, unique in Europe. As it is an endangered species that makes up plant communities with great palaeoecological significance, the development of species distribution models is of major interest under different climatic scenarios, past, present and future, based on the fact that the climate could play a relevant role in the distribution of this species as well as in the conformation of the communities in which it is integrated. Palaeoecological models were generated for the Maximum Interglacial, Last Maximum Glacial and Middle Holocene periods. The results obtained showed that the widest distribution of this species, and the maximum suitability of its habitat, occurred during the Last Glacial Maximum, when the temperatures of the peninsular southeast were not as contrasting as those of the rest of the European continent and were favored by higher rainfall. Under these conditions, large territories could act as shelters during the glacial period, a hypothesis reflected in the models results for this period, which exhibit a further expansion of G. senegalensis ecological niche. The future projection of models in around 2070, for four Representative Concentration Pathway (RCP) according to the fifth report of the Intergovernmental Panel on Climate Change IPCC, showed that the most favorable areas for this species would be Campo de Dalias (southern portion of Almeria province) as it presents the bioclimatic characteristics of greater adjustment to G. senegalensis ecological niche model. Currently, these areas are almost totally destroyed and heavily altered by intensive agriculture under plastic, also causing a severe fragmentation of the habitat, which implies a prospective extinction scenario in the near future.

ecology↗

bioRxiv2019

Identification of a Novel Retrieval-Dependent Memory Process in the Crab Neohelice granulata

Fully consolidated associative memories may be altered by alternative retrieval dependent memory processes. While a brief exposure to the conditioned stimulus (CS) can trigger reconsolidation of the original memory, a prolonged CS exposure will trigger memory extinction. The conditioned response is maintained after reconsolidation, but is inhibited after extinction, presumably by the formation of a new inhibitory memory trace. In rats and humans, it has been shown that CS exposure of intermediate duration leave the memory in an insensitive or limbo state. Limbo is characterised by the absence of reconsolidation or extinction. Here we investigated the evolutionary conserved nature of limbo using a contextual Pavlovian conditioning (CPC) memory paradigm in the crab Neohelice granulata. In animals with fully consolidated CPC memory, systemic administration of the protein synthesis inhibitor cycloheximide after 1 CS presentation disrupted the memory, presumably by interfering with memory reconsolidation. The same intervention given after 320 CSs prevented CPC memory extinction. Cycloheximide had no behavioural effect when administered after 80 CS presentations, a protocol that failed to extinguish CPC memory. Also, we observed that a stronger CPC memory engaged reconsolidation after 80 CS instead of limbo, indicating that memory strength affects the parametrical conditions to engage either reconsolidation or limbo. Altogether, these results indicate that limbo is an evolutionary conserved memory process segregating reconsolidation from extinction in the number of CSs space. Limbo appears as an intrinsic component of retrieval dependent memory processing, with a key function in the transition from memory maintenance to inhibition. Author statement (CRediT Roles)Santiago A. Merlo: Conceptualization, Data curation, Formal Analysis, Investigation, Software, Validation, Visualization, Writing - original draft, Writing - review & editing. Jimena Santos: Investigation, Writing - review & editing. Maria Eugenia Pedreira: Conceptualization, Funding acquisition, Project administration, Resources, Supervision, Validation, Writing - original draft, Writing - review & editing. Emiliano Merlo: Conceptualization, Funding acquisition, Project administration, Resources, Supervision, Validation, Writing - original draft, Writing - review & editing.

neuroscience↗

bioRxiv2019

Behavioural Evaluation of the Anticonvulsant Properties of the Traditional Medicine Anonna Senegalensis on Parabss Drosophila melanogaster Mutants.

Epilepsy is the most common serious neurological disorder affecting 50 million people worldwide, 40 millions of which live in developing countries. Despite the introduction of a dozen of new Anti-Epileptic Drugs (AEDs), one third of the patients continue to have seizure regardless of receiving a AEDs treatment. This emphasize on the need to discover new drugs with different mechanisms of action. Traditional medicine (TM), pays a significant role in the treatment of epilepsy in many countries and offers an affordable and accessible alternative to AEDs. However, the lack of both empirical testing in animal models and clinical data places constrains to their clinical recommendation.\n\nIn this study, we use Drosophila melanogaster as a model for epilepsy and tested the anti-seizure effect of leaf and stem bark aqueous extract form Annona senegalensis, a plant used as anti-convulsant by rural populations in Africa.\n\nOur results show, that at the concentrations tested, the leaf extract of A. senegalensis was more effective than the AEDs phenytoin and phenobarbital to control seizures. These promising results demonstrate that Drosophila is an excellent model for new drug discovery and that it could be used to do large scale screening of TMs for the treatment of epilepsy.

pharmacology and toxicology↗