Early Olfactory, but not Gustatory Processing, is Affected by the Selection of Heritable Cognitive Phenotypes in Honey Bee

Associative learning enables animals to predict rewards or punishments by their associations with predictive stimuli, while non-associative learning occurs without reinforcement. The latter includes latent inhibition (LI), whereby animals learn to ignore an inconsequential ‘familiar’ stimulus. Individual honey bees display heritable differences in expression of LI. We examined the behavioral and neuronal responses between honey bee genetic lines exhibiting high and low LI. We observed, as in previous studies, that high LI lines learned a familiar odor more slowly than low LI bees. By measuring gustatory responses to sucrose, we determined that perception of sucrose reward was similar between both lines, thereby not contributing to the LI phenotype. We then used extracellular electrophysiology to determine differences in neural responses of the antennal lobe (AL) to familiar and novel odors between the lines. Low LI bees responded significantly more strongly to both familiar and novel odors than the high LI bees, but the lines showed equivalent differences in response to the novel and familiar odors. This work suggests that some effects of genotype are present in early olfactory processing, and those effects could complement how LI is manifested at later stages of processing in brains of bees in the different lines

Effects of maternal binge alcohol consumption on emotional, cognitive and addictive behaviour in mice

Maternal alcohol binge drinking during pregnancy can be deleterious for the developing foetus, leading to a wide range of long-lasting morphological and neurobehavioural disabilities known as foetal alcohol spectrum disorders, associated with a higher risk of developing substance use disorders later in life. We sought to assess the effects of prenatal and postnatal alcohol exposure on cognitive, emotional, motor and addictive behaviour in mice and its underlying molecular mechanisms. Pregnant C57BL/6 female mice underwent a procedure to model alcohol binge drinking either during gestation or throughout both the gestation and lactation periods. Then, male offspring were assessed for their behaviour at adulthood. Binge alcohol exposure during early brain development induces cognitive deficits, increased anxiety-like behaviour, motor coordination impairments, and age-dependent locomotor activity alterations. Behavioural effects are associated with an upregulation of pro-inflammatory signalling, gliosis, neuronal death, myelin impairments and epigenetic modifications in the prefrontal cortex and hippocampus. Furthermore, early alcohol exposed mice show alterations in brain network connectivity. Curcumin treatment ameliorates anxiety and cognitive dysfunctions, and rescues alcohol-induced neuroinflammation. In addition, mice exposed to alcohol in utero and postnatally show increased susceptibility to later alcohol and cocaine intake compared with their counterparts. Molecular analyses of the prefrontal cortex and striatum of these animals suggest alterations in the glutamatergic excitability within the mesocorticolimbic reward system following cocaine-induced reinstatement. Altogether, our results reveal that maternal binge-like alcohol consumption induces molecular alterations in offspring’s brain that may underlie the long-lasting impairments in offspring’s behaviour.El consum maternal d’alcohol en afartament durant l’embaràs pot resultar perjudicial per al fetus en desenvolupament, donant lloc a una àmplia gamma de discapacitats físiques i mentals conegudes com a trastorns de l’espectre alcohòlic fetal que persisteixen al llarg de la vida i estan associades a un major risc de desenvolupar trastorns d’ús de substàncies en el futur. En aquesta tesi hem tractat d’avaluar els efectes de l’exposició prenatal i postnatal a l’alcohol en la conducta cognitiva, emocional, motora i addictiva en ratolins i els mecanismes moleculars subjacents a aquests. Les femelles de ratolins C57BL/6 embarassades van ser sotmeses a un procediment per modelar el consum d’alcohol en afartament durant la gestació o bé, al llarg dels períodes de gestació i lactància. A continuació es va avaluar el comportament de la descendència masculina a l’edat adulta. S’ha observat que l’exposició d’alcohol en afartament durant el desenvolupament cerebral indueix dèficits cognitius, augment de l’ansietat, alteracions de coordinació motora i de l’activitat locomotora en funció de l’edat. Els efectes del comportament estan associats a un increment de la senyalització proinflamatòria, gliosi, mort neuronal, deteriorament de la mielina i modificacions epigenètiques en el còrtex prefrontal i l’hipocamp, així com també alteracions en la connectivitat de la xarxa neuronal. El tractament de curcumina alleuja l’ansietat i les disfuncions cognitives, i restableix la neuroinflamació induïda per l’alcohol. A més, els ratolins exposats a l’alcohol durant la gestació i la lactància mostren una major susceptibilitat a la ingesta posterior d’alcohol i cocaïna en comparació amb els seus homòlegs. Els anàlisis moleculars de l’escorça prefrontal i de l’estriat d’aquests animals suggereixen la presència d’alteracions en l’excitabilitat glutamatèrgica en el sistema de recompensa mesocorticolimbic després de la recaiguda induïda per cocaïna. En conjunt, els nostres resultats indiquen que el consum maternal d’alcohol en afartament provoca alteracions moleculars en el cervell de la descendència com a mecanisme subjacent a les alteracions relatives al comportament persistents

The role of schizophrenia susceptibility genes in associative learning

Schizophrenia is highly heritable, indicating that a large proportion of one’s susceptibility to developing the disorder is attributable to genetics. Recent large-scale genomic studies have revealed that genetic variants in patients with schizophrenia affect genes involved in synaptic plasticity processes, which are required for learning and memory, including genes encoding protein complexes associated with the NMDA receptor and the postsynaptic density. Further evidence suggests that associative learning may be particularly affected, although it is unclear which components of this cognitive process are implicated in schizophrenia. The present studies investigated the relationship between particular phases of associative learning, represented by the consolidation, retrieval and extinction of contextual fear memory in rats, with genetic variants, psychoactive drugs and postsynaptic density proteins associated with schizophrenia. I tested associative learning-related gene expression datasets for enrichment in genetic copy number variants from a large cohort of patients with schizophrenia and demonstrated that only genes associated with extinction learning are enriched in patient variants (Chapter 3). I report that fear extinction in rats was impaired by administration of the NMDA antagonist and psychotomimetic, ketamine (Chapter 4). The expression of activity- induced, postsynaptic density products of the Homer1 gene, which has been linked to psychiatric disease, was differentially regulated in specific hippocampal subregions following extinction learning (Chapter 5), and the effect of a partial knockdown of these genes during different phases of associative learning was investigated (Chapter 6). These results build on clinical studies linking abnormalities in associative and, specifically, extinction learning with schizophrenia and support the notion that genetic variants associated with the disorder impact particular cognitive domains. My findings are consistent with the theory that altered inhibitory-type learning processes contribute to the manifestation of schizophrenia