Retention of Memory through Metamorphosis: Can a Moth Remember What It Learned As a Caterpillar?

Insects that undergo complete metamorphosis experience enormous changes in both morphology and lifestyle. The current study examines whether larval experience can persist through pupation into adulthood in Lepidoptera, and assesses two possible mechanisms that could underlie such behavior: exposure of emerging adults to chemicals from the larval environment, or associative learning transferred to adulthood via maintenance of intact synaptic connections. Fifth instar Manduca sexta caterpillars received an electrical shock associatively paired with a specific odor in order to create a conditioned odor aversion, and were assayed for learning in a Y choice apparatus as larvae and again as adult moths. We show that larvae learned to avoid the training odor, and that this aversion was still present in the adults. The adult aversion did not result from carryover of chemicals from the larval environment, as neither applying odorants to naïve pupae nor washing the pupae of trained caterpillars resulted in a change in behavior. In addition, we report that larvae trained at third instar still showed odor aversion after two molts, as fifth instars, but did not avoid the odor as adults, consistent with the idea that post-metamorphic recall involves regions of the brain that are not produced until later in larval development. The present study, the first to demonstrate conclusively that associative memory survives metamorphosis in Lepidoptera, provokes intriguing new questions about the organization and persistence of the central nervous system during metamorphosis. Our results have both ecological and evolutionary implications, as retention of memory through metamorphosis could influence host choice by polyphagous insects, shape habitat selection, and lead to eventual sympatric speciation

Neurovascular unit dysfunction with blood-brain barrier hyperpermeability contributes to major depressive disorder: a review of clinical and experimental evidence

About one-third of people with major depressive disorder (MDD) fail at least two antidepressant drug trials at 1 year. Together with clinical and experimental evidence indicating that the pathophysiology of MDD is multifactorial, this observation underscores the importance of elucidating mechanisms beyond monoaminergic dysregulation that can contribute to the genesis and persistence of MDD. Oxidative stress and neuroinflammation are mechanistically linked to the presence of neurovascular dysfunction with blood-brain barrier (BBB) hyperpermeability in selected neurological disorders, such as stroke, epilepsy, multiple sclerosis, traumatic brain injury, and Alzheimer’s disease. In contrast to other major psychiatric disorders, MDD is frequently comorbid with such neurological disorders and constitutes an independent risk factor for morbidity and mortality in disorders characterized by vascular endothelial dysfunction (cardiovascular disease and diabetes mellitus). Oxidative stress and neuroinflammation are implicated in the neurobiology of MDD. More recent evidence links neurovascular dysfunction with BBB hyperpermeability to MDD without neurological comorbidity. We review this emerging literature and present a theoretical integration between these abnormalities to those involving oxidative stress and neuroinflammation in MDD. We discuss our hypothesis that alterations in endothelial nitric oxide levels and endothelial nitric oxide synthase uncoupling are central mechanistic links in this regard. Understanding the contribution of neurovascular dysfunction with BBB hyperpermeability to the pathophysiology of MDD may help to identify novel therapeutic and preventative approaches

Mémoire, vieillissement et niveaux du traitement: dissociation entre deux tâches d'orientation sémantique.

Certains auteurs supposent que parce que les sujets âgés ne traitent pas l’information aussi profondément que les sujets plus jeunes, ils présentent des performances plus faibles en mémoire. Dans la présente étude, nous avons manipulé les effets de l’âge et du niveau du traitement sur une tâche de rappel libre. Les niveaux du traitement sont opérationnalisés avec des tâches orientées à l’encodage, où nous avons comparé, chez des sujets jeunes et âgés les effets la réalisation de deux tâches sémantiques différentes (jugement d’agrément et la production d’un associé) par rapport à l’effet de la mise en oeuvre d’une tâche non sémantique (comptage de voyelles). Les résultats ont montré que seule la tâche de jugement d’agrément permettait d’ob¬ server une interaction entre l’âge et le niveau du traite¬ ment, contrairement à la tâche de production d’associés qui permet aux sujets âgés, comme aux sujets jeunes d’aug¬ menter leurs performances au test de rappel libre. Les résultats suggèrent qu’avec une tâche appropriée, les sujets âgés sont en mesure d’effectuer des traitements efficaces pour la mémorisation et sont interprétés dans le cadre de l’hypothèse environnementale.Taconnat Laurence, Isingrini Michel. Mémoire, vieillissement et niveaux du traitement : dissociation entre deux tâches d’orientation sémantique. In: Bulletin de psychologie, tome 57 n°474, 2004. pp. 635-639

Connaissances et contrôle exécutif : deux facteurs cognitifs de protection contre le vieillissement de la mémoire épisodique ?

International audienceIn this study we refer to Craik and Bialystok's model distinguishing the “knowledge” (cultural learning experience that forms the basis for knowledge of the world) and the “executive control” (set of operations that control and regulate cognitive performance) as two main factors susceptible accounting for the age-related negative effects on the cognitive functioning, and for a possible age-related protective effect. Thus, the aim of the present study was to examine the possible protective effect of these two factors on the age-related decline in a cued-recall task. Four age groups of participants (20–39 years, 40–59 years, 60–74 years and 75–90 years) were administered with a word-stem cued-recall test to assess episodic memory, a “vocabulary” sub-test of the WAIS-R to assess knowledge and a reading span test to assess control. Results showed an age-related effect on the episodic memory, the control performance and the knowledge measure, indicating that performance decreases with age. A GLM analysis revealed a positive effect of the knowledge and the control factors on the cued-recall performance, and interaction between age and the knowledge factor resulting from a positive effect of the knowledge level only for the youngest group of participants (20–39 years). Furthermore, results revealed an interaction between age and the control factor, indicating a positive effect of the control level for the two oldest groups of participants (60–74 years and 75–90 years). These results suggest that, contrary to the knowledge, the control factor could be an effective protection against the age-related negative effects on the episodic memory.En nous basant sur le modèle de Craik et Bialystok (2006, 2008) qui distingue les « connaissances » et le « contrôle exécutif » comme deux facteurs susceptibles d’expliquer les effets négatifs du vieillissement mais aussi les phénomènes de protection qui l’accompagnent, nous avons souhaité examiner le potentiel effet protecteur de ces deux facteurs sur le déclin des performances de rappel indicé associé au vieillissement. Une analyse GLM a mis en évidence une interaction entre l’âge et le facteur connaissances indiquant un effet bénéfique des connaissances uniquement pour le groupe d’âge le plus jeune (20–39 ans). De plus, une interaction entre l’âge et le facteur contrôle a également été révélée, indiquant un effet bénéfique d’un haut niveau de contrôle pour les groupes d’âge 60–74 ans et 75–90 ans. Ces résultats suggèrent que, contrairement aux connaissances, le contrôle pourrait constituer un bon candidat en tant que facteur de protection efficace contre les effets délétères du vieillissement sur la mémoire épisodique