Bipolar affective disorder and schizophrenia are highly heritable psychiatric illnesses and the leading causes of worldwide disability. The orbitofrontal cortex (OFC) is a region of the frontal lobe with wide spread connectivity with other brain areas involved in reward, motivation and emotion. Evidence from various neuroimaging, genetic, post-mortem and brain lesion studies suggest that orbitofrontal cortex may play a role in pathophysiology of mental illnesses. This thesis sought to investigate the pathogenesis of major psychiatric illnesses through the investigation of orbitofrontal morphology in schizophrenia and bipolar disorder and through its associations with brain structure and function. Orbitofrontal morphology and its structural and functional associations were examined in healthy controls, patients with schizophrenia or bipolar affective disorder, and those at high genetic risk using functional and structural MRI. In the first study we found that the orbitofrontal type III is more frequent and the orbitofrontal type I is less common in the right hemisphere in patients with schizophrenia while in patients with bipolar disorder type III appears more often in both left and right hemispheres. We then sought to examine the relationship of orbitofrontal morphology to disease risk in a study of 146 people at high risk of developing schizophrenia and 110 people at high risk of developing bipolar disorder. We discovered that in the unaffected high risk groups the orbitofrontal type III predicted the development of later psychiatric illnesses, when combined with anterior cingulate morphology. Finally we showed, in a further study, that OFC morphology was associated with measures of schizotypy, brain structure, brain function and cognition. In conclusion, orbitofrontal morphology is linked to major psychiatric disorder and has significant structural and functional associations. As orbitofrontal sulcogyral patterns are formed in early life a fuller awareness of their relevance to brain function holds out the prospect that we could use such measures as an indicator of vulnerability to the development of illness later in life. This work points to the potential for the foundation of a theory of predictive associations between morphological patterns and the development of psychosis.

Indiana University-Purdue University Indianapolis (IUPUI) / Social processing is the reception, interpretation, and reciprocation of social information and is critical for mental health. The neural structures, circuits, and substrates regulating these complex mechanisms are not well understood. Social processing in the form of social safety learning, as measured by a rat model of social familiarity-induced anxiolysis (SoFiA), was impaired following mild blast traumatic brain injury (mbTBI). Initial findings indicated that mbTBI altered resting state network activity in the orbitofrontal cortex (OFC) and was associated with accumulation of neurotoxin marker, acrolein, in lateral prefrontal cortex (PFC) (including OFC), indicating OFC as a brain region of interest that may contribute to social processing. Measuring GABA and Glutamate-related gene expression in OFC of mbTBI or sham-exposed rat brain revealed specific elevations of metabotropic glutamate receptor type 1 and 5 (mGluR1/5) expression in mbTBI but not sham OFC. Exposure-naïve rats intracranially injected with mGluR1/5 agonist demonstrated attenuated SoFiA, and this coincided with an impairment of social recognition (SR) behavior. Additionally, inactivation of OFC by local intracranial injection of GABAA agonist, muscimol, impaired two different measures of SR in which two conspecifics, or members of the same species, one novel and one familiar, were presented and required discrimination. Novelty seeking, decision-making, memory, and gregariousness were tested in isolation to determine OFC contributions to these specific behavioral contributions to SR test performance. OFC inactivation did not impair novelty seeking, non-social decision-making, or non-social memory as measured by novel object recognition (NOR) test, or gregariousness or social decision-making as measure by social preference (SP) test. When measuring SR behavior via consecutive presentation of two different conspecifics, OFC inactivation did not impact SR. Therefore, OFC is not directly responsible for social recognition, but rather the discrimination or ability to act upon discrimination of two simultaneously present conspecifics. These data suggest a novel role for OFC in high order processing or execution of action based on social information. / 2 years (2021-05-24)

In recent years Social Neuroscience has started to investigate how mood and culture influence social and emotional situations. In the present study differences in elicited emotion and neural activation were investigated when participants viewed films depicting social interactions. Film clips are preferred stimuli for elicitation of emotion in laboratory studies, but given the lack of standardised film sets in the literature, two behavioural studies were conducted prior to imaging. The first study (147 females, 30 males; 98.8% 18 to 24 years) identified a set of clips that elicited emotion profiles in which the target emotion (happy, sad) was strongest, as well as neutral clips, and demonstrated an effect of participants’ stable mood. The second study (143 females, 19 males; mean age 19.2 years) optimised the stimulus set and demonstrated effects of self-reported ethnic origin, mood and interest on profiles of elicited emotion. In the fMRI investigation 33 female and 8 male participants (mean age 19.2 years) viewed film clips in a block design experiment with loose and tight t-contrasts and retrospective ratings of elicited emotion. Across all-participants, social interaction depicting sadness activated key emotion-related structures such as left amygdala and insula, and medial frontal cortex that were not significantly activated with social interaction depicting happiness. However, greater activation was observed for Europeans than for non-Europeans in orbitofrontal cortex, anterior and posterior cingulate for happy social interaction and in hippocampus, precuneus and retrosplenial cortex for sad social interaction. Individual differences in trait emotions and stable mood were measured with PANAS-X. For high fatigue participants greater activation was observed in the left amgydala for happy social interaction. For participants with high positive stable mood greater activation was observed in the insula for happy and sad social interaction. The research described here indicates that self-reported ethnic origin and mood are potentially significant influences on elicited emotion and brain reactivity to positive and negative social and emotional situations.

This study analyzed the relationship between the OF functioning of 100 incarcerated male offenders and their psychopathy symptoms. The study's rejected hypothesis had predicted a significant relationship between measures of OF functioning and the Defective Affective Experience (DAE) and Impulsive and Irresponsible Behavioral Style (IIB) factors of the Cooke and Michie (2001) three-factor model of psychopathy. Regression analysis failed to demonstrate a relationship between OF functioning and the DAE and IIB factors. Group differences on OF functioning were not demonstrated between participants in the upper and lower quartiles of a summed DAE and IIB factor score. A general role for OF functioning in criminal behavior was suggested as two OF measures accounted for 14.9% of the variance of criminal convictions.

Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal.

The amygdala and hippocampus interact with thalamocortical systems to regulate cognitive-emotional learning, and lesions of amygdala, hippocampus, thalamus, and cortex have different effects depending on the phase of learning when they occur. In examining eyeblink conditioning data, several questions arise: Why is the hippocampus needed for trace conditioning where there is a temporal gap between the conditioned stimulus offset and the onset of the unconditioned stimulus, but not needed for delay conditioning where stimuli temporally overlap and co-terminate? Why do amygdala lesions made before or immediately after training decelerate conditioning while those made later have no impact on conditioned behavior? Why do thalamic lesions degrade trace conditioning more than delay conditioning? Why do hippocampal lesions degrade recent learning but not temporally remote learning? Why do cortical lesions degrade temporally remote learning, and cause amnesia, but not recent or post-lesion learning? How is temporally graded amnesia caused by ablation of medial prefrontal cortex? How are mechanisms of motivated attention and the emergent state of consciousness linked during conditioning? How do neurotrophins, notably Brain Derived Neurotrophic Factor (BDNF), influence memory formation and consolidation? A neural model, called neurotrophic START, or nSTART, proposes answers to these questions. The nSTART model synthesizes and extends key principles, mechanisms, and properties of three previously published brain models of normal behavior. These three models describe aspects of how the brain can learn to categorize objects and events in the world; how the brain can learn the emotional meanings of such events, notably rewarding and punishing events, through cognitive-emotional interactions; and how the brain can learn to adaptively time attention paid to motivationally important events, and when to respond to these events, in a context-appropriate manner. The model clarifies how hippocampal adaptive timing mechanisms and BDNF may bridge the gap between stimuli during trace conditioning and thereby allow thalamocortical and corticocortical learning to take place and be consolidated. The simulated data arise as emergent properties of several brain regions interacting together. The model overcomes problems of alternative memory models, notably models wherein memories that are initially stored in hippocampus move to the neocortex during consolidation.

Early life stress is a prevalent problem affecting many worldwide and can be experienced in a variety of ways, including limited access to resources as in many low socioeconomic status households. In humans, exposure to stress early in life is linked to various psychiatric conditions such as substance use disorder, attention-deficit/hyperactivity disorder, and gambling. One characteristic that these disorders share is elevated impulsivity. Impulsivity is a multifaceted construct and often behaviors are classified as either an impulsive choice (e.g., inability to delay gratification) or an impulsive action (e.g., inability to inhibit premature responses). In the first set of experiments presented here, we characterize the limited bedding and nesting model (LBN) of early life adversity in rodents, in which rat dams and their pups are housed in a limited resource environment from postnatal day (PND) 2 through 9. This model works by inducing stress in the dams, which alters their maternal care behaviors towards pups. As a result, this altered care can be stressful for the developing pups. We have found that LBN exposure promoted resilience to addiction-related phenotypes in adult male, but not female rats. Specifically, LBN reduced impulsive choice, morphine self-administration, and nucleus accumbens (NAc) glutamate transmission in males, effects not seen in females. Additionally, changes in NAc gene transcription unique to LBN males may contribute to resilience. We build on these findings in the second set of experiments, which explores whether LBN alters impulsive action, risky decision-making, and the gene transcriptome of the orbitofrontal cortex (OFC). We found that LBN increased impulsive action in males. Additionally, we found LBN exposure in rats across sex reduces risky choice. These changes in behavior were accompanied by highly specific changes in gene transcription in the OFC, which is a brain region that mediates both impulsive and risky decision-making behaviors. The identification of genes and signaling pathways that are altered by LBN in the male OFC lays the groundwork for future studies investigating the mechanisms by which early life stress alters addiction-related phenotypes. / Psychology

No description available.

Le trouble obsessionnel-compulsif (TOC) est un trouble anxieux fréquent et invalidant. Pour un grand nombre de patients, il existe une résistance aux thérapeutiques actuellement disponibles, soulignant toute l'importance de mieux préciser la physiopathologie du TOC. Le principal objectif de cette thèse est d’étudier les altérations anatomiques et fonctionnelles des voies thalamo-corticales intéressant le cortex orbitofrontal (COF) et le cortex cingulaire antérieur (CCA) dans le TOC. Pour cela, nous avons utilisé plusieurs outils complémentaires permettant d’appréhender cette problématique sous différents angles méthodologiques.Concernant les altérations anatomiques associées au TOC, nous avons rapporté les données de méta-analyses des études de neuro-imagerie volumétrique et morphométrique ainsi que les résultats d'une étude originale d'imagerie volumétrique. Une diminution du volume orbitofrontal, une augmentation du volume thalamique et une relation entre ces modifications de volumes ont été observées chez les patients avec TOC comparativement aux témoins. Les modifications de densité de matière grise concernaient le COF et le putamen dans le sens d'une augmentation et les cortex pariétal et préfrontal dorsolatéral dans le sens d'une diminution dans le TOC.Concernant les altérations fonctionnelles associées au TOC, nous avons détaillé un travail de méta-analyse des études d'imagerie fonctionnelle, un travail expérimental chez le primate basé sur des manipulations pharmacologiques intra-cérébrales, puis un travail expérimental chez l'homme reposant sur le développement d'une tâche comportementale originale couplée à l'imagerie fonctionnelle. Dans notre méta-analyse, nous avons décrit la participation fonctionnelle de régions comme le COF, le thalamus et le striatum lorsque des symptômes obsessionnels et compulsifs étaient provoqués chez des patients. Chez le primate subhumain, nous avons montré qu'une hyperactivation du noyau ventral-antérieur, par levée de l'inhibition GABAergique, entraînait l'apparition de comportements pseudo-compulsifs. Ensuite, à l'aide d'une tâche originale qui mettait les sujets en situation de vérifier, nous avons mis en évidence que les dysfonctions orbitofrontales associées au doute lors de la prise de décision n'étaient pas modulées ni par les informations contextuelles (signaux d'erreur), ni par la réponse comportementale chez les patients avec TOC comparativement à des sujets témoins.Enfin, la superposition des cartes morphométriques et fonctionnelles a trouvé une relation entre les altérations anatomiques et fonctionnelles au sein du COF. Nos résultats soulignent toute l'importance des voies thalamo-orbitofrontales dans la physiopathologie du TOC. / Obsessive-compulsive disorder (OCD) is a frequent and disabling anxiety disorder. Available treatments are effective for most patients but impairing residual symptoms and treatment resistance are common in OCD patients. Therefore, a better understanding of OCD pathophysiology is essential for further improvement of therapeutic strategies. The main goal of my thesis was to assess the anatomical and funtional thalamocortical alterations associated with OCD. Concerning the anatomical thalamocortical alterations associated with OCD, we conducted two meta-analyses of anatomical neuroimaging studies and an original volumetric neuroimaging study. We reported a smaller thalamic volume and a greater orbitofrontal volume, but also an inverse relationship between the volume changes in OCD patients compared with healthy subjects. Furthermore, we showed that gray matter density within the orbitofrontal cortex and the putamen were enhanced in OCD. Concerning the functional thalamocortical alterations associated with OCD, we reported data coming from a meta-analysis of functional neuroimaging studies, an experimental study in subhuman primates using local brain pharmacological manipulations and an event-related neuroimaging study in OCD patients. In our meta-analysis, we showed that the orbitofrontal cortex, the thalamus and the striatum were involved in the mediation of OCD symptoms. In subhuman primates, the pharmacologically induced overactivity within the ventralanterior thalamic nucleus leaded to the emergence of compulsive-like behaviors. Then, in our neuroimaging study, we found that doubt-related orbitofrontal dysfunctions were not modulated by neither error signals nor compulsive-like behaviors in OCD patients, compared with healthy subjects. Finally, we described by using meta-analytic data that anatomical and functional brain alterations overlap with the lateral orbitofrontal cortex in OCD. In conclusion, our results suggest that the thalamo-orbitofrontal network may play a primary role in the genesis and mediation of OCD symptoms.

As teorias mais influentes acerca do funcionamento do córtex pré-frontal (PFC) tomam essa estrutura como um córtex de associação e de integração de informações oriundas de outras estruturas nervosas. Isso implicaria na participação direta do PFC nos processos de memória operacional e em processo atencionais. Estudos hodológicos e neurofisiológicos sugerem, que o córtex orbitofrontal (OFC) seria responsável pela integração de informações de caráter sensorial, motivacional e afetivo, enquanto o córtex pré-frontal ventromedial (vmPFC) seria diretamente ligado ao OFC, tendo um papel crucial na codificação de estímulos emocionais oriundos da amígdala. Nesse contexto, é aceito que a integração das informações feita por essas estruturas seja essencial para o processo de tomada de decisões, uma vez que esse comportamento necessita de uma avaliação do ambiente em termos de comparações de situações novas a experiências prévias armazenadas na memória, assim como um balanço entre custos, benefícios e cálculo de possíveis valores da recompensa. Para testar essas hipóteses, ratos com danos seletivos no vmPFC foram submetidos testes de avaliação de ansiedade e medo condicionado no paradigma de teste e reteste no labirinto em cruz elevado (LCE), assim como a testes de memória de referência espacial e memória operacional no labirinto aquático de Morris. Outro grupo de animais teve matrizes de multi-eletrodos implantadas no OFC para a avaliação da atividade neuronal dessa estrutura em um teste envolvendo tomada de decisões, no qual devem escolher entre ganhar 1 pellet de chocolate imediatamente ou 4 pellets envolvendo atrasos variados. No teste no LCE, animais com lesão no vmPFC diferem dos animais controle por apresentarem uma diminuição do tempo de avaliação de risco sem apresentar alterações nos parâmetros que aferem memória, atividade locomotora e ansiedade. No teste de memória de referência espacial após treinamento extensivo de busca pela plataforma em um mesmo local no labirinto aquático, animais com lesão persistem no local quando se retira a plataforma (probe test). Já no teste de memória operacional, no qual a localização da plataforma é alterada diariamente, esses animais não diferem do grupo controle. Na tarefa envolvendo tomada de decisões, observou-se uma atividade eletrofisiológica de neurônios do OFC relacionada ao momento crítico no qual o animal deve realizar uma escolha. Em conjunto, esses resultados mostram que o vmPFC está relacionado à flexibilidade comportamental e tomada de decisões, possivelmente em conjunto com o OFC, cuja atividade neuronal sugere uma participação nos processos de tomada de decisões e de elaboração de estratégias / The most influential theories on the function of the prefrontal cortex (PFC) suggest that this structure is an association cortex, responsible for integration of information received from other parts of the brain. This would implicate in direct participation of the PFC in working memory and attentional processes. Given this context, hodological and neurophysiological studies suggest that the orbitofrontal cortex (OFC) would be responsible for the integration of sensory, motivational and affective aspects, while the ventromedial prefrontal cortex (vmPFC), which is directly connected to the OFC, would have a key role in encoding emotional stimuli from the amygdala. It is well accepted that the processing of these aspects of information is crucial for decision-making processes, given the fact that this expression of behavior requires an evaluation of the environment in terms of comparing novel situation to previous experiences, as well as processing the balance between costs, outcomes and reward values. In order to test these hypotheses, rats with selective lesions to the vmPFC were subjected to the elevated plus maze (EPM) to evaluate anxiety and conditioned fear in the test retest paradigm. Animal were also tested in a spatial reference memory and a working memory tasks in the Morris water maze. Another group of rats had multi-electrode arrays chronically implanted in the OFC for the evaluation of the neuronal activity during a decision-making task, in which the animals had to choose between a small reward of one chocolate pellet immediately and a large reward of four chocolate pellets after varying delays. The results of the EPM show that animals with lesion to the vmPFC differ from control animals by showing diminished time evaluating risk in the second exposure to the EPM, without damage to locomotor activity, memory and anxiety levels. In the reference spatial memory task in the water maze, after extensive training searching for the hidden platform in the same location, lesioned animals persisted searching for the platform in that particular location after it was removed (probe test). However, in the working memory task, in which the platform is presented in a different location each day, lesioned animals did not differ from control animals. In the decision-making task, differential electrophysiological activity in OFC neurons was observed, particularly in the moment of the task in which the animal was required to perform the choice between rewards. Together, these results suggest that the vmPFC is related to behavioral flexibility and decision-making, possibly acting together with the OFC, which neuronal activity suggests participation in decision-making processes