O córtex pré-frontal medial (CPFM) é uma estrutura pertencente ao sistema límbico, sendo topograficamente divido em córtex cíngulo 1, cíngulo 2, pré- límbico (PL), infra-límbico (IL) e dorsopenducular (DP). Sua porção ventral (CPFMv) corresponde ao PL, IL e DP. O PL e o IL são capazes de modular o arco reflexo baroceptor, permitindo ajustes cardiovasculares que ocorrem durante reações de defesa. Trabalhos mostram que a transmissão glutamatérgica do CPFMv é capaz de controlar a atividade barorreflexa através de receptores NMDA. Além disso a liberação de glutamato pode ser modulada por outros neurotransmissores, como os endocanabinóides, que além de ativarem receptores CB1, também são agonistas de receptores TRPV1, nos quais facilitam a liberação de glutamato em várias áreas do sistema nervoso central. Portanto, a hipótese deste trabalho é a de que os receptores TRPV1 presentes no CPFM estariam participando da modulação do barorreflexo. Para testar esta hipóstese foram utilizados ratos Wistar, pesando de 240 a 260 gramas. Esses animais foram submetidos a estereotaxia para implante de cânulas guia no CPFMv. Setenta e duas horas depois foi implantado um cateter de polietileno na artéria femoral dos animais, o qual foi conectado ao aparelho de aquisição para monitoração da frequência cardíaca e pressão arterial no dia do teste. Um segundo cateter foi implantado na veia femoral para infusão de drogas vasoativas. Foram usados dois antagonistas de receptores TRPV1, a capsazepina e o a 6-iodonordiidrocapsaicina (6-IODO), além do agonista desses receptores, a capsaicina. A microinjeção da capsazepina no CPFMv reduziu o ganho das curvas de regressão linear dos componentes bradicárdico e taquicárdico do barorreflexo. Os parâmetros da curva sigmoide também foram reduzidos. Posteriormente, a administração de 6-IODO também reduziu o ganho das curvas de regressão linear das respostas bradicárdica e taquicárdica, bem como os parâmetros das curvas de regressão não-linear. Esta droga também foi utilizada para verificar se os receptores TRPV1 do PL e IL modulam diferentemente a resposta barorreflexa. Foi verificado que ambas as subáreas modulam a atividade barorreflexa da mesma maneira. A capsaicina, quando microinjetada bilateralmente no CPFMv aumentou o ganho das curvas de regressão linear relativas à bradicardia e taquicardia reflexas bem como aumentou os valores dos parâmetros da curva sigmoide. Além disso, o pré-bloqueio dos receptores TRPV1 do CPFMv com uma dose inefetiva de 6-IODO aboliu o aumento da atividade barorreflexa induzida pela capsaicina. Em um outro grupo de animais foi feito o pré-tratamento do CPFMv com uma dose inefetiva de 6-IODO e cinco minutos depois administrou-se doses maiores de capsaicina. Observou-se um deslocamento da curva dose resposta da capsaicina para a direita, sem alteração do efeito máximo. A conclusão do presente trabalho é a de que os receptores TRPV1 presentes no CPFMv modulam a resposta do arco reflexo baroceptor. / Medial prefrontal cortex (MPFC) is a limbic structure, being topographically divided in cingulate cortex 1, cingulate cortex 2, prelimbic (PL), infralimbic (IL) and dorsopenducular (DP) cortices. The ventral portion of the MPFC (vMPFC) comprises the IL, PL and DP. The IL and PL regions are able to modulate cardiovascular responses associated with defensive reactions, such as the baroreceptor reflex arc. Some studies have shown that the vMPFC glutamatergic transmission modulates the baroreflex activity, through NMDA receptors. Moreover, the glutamatergic release is controlled by other neurotransmitters, such as the endocannabinoids which are agonists of the TRPV1 receptors, besides its action on the CB1 receptors. Furthermore, the TRPV1 channels facilitate the glutamatergic transmission in several brain areas. Thus, the hypothesis of the present work is that the vMPFC TRPV1 receptors are involved in the baroreflex modulation. In order to test this assumption, male Wistar rats weighing 240-260 g were used. These animals were submitted to the stereotaxic surgery to implant stainless steel guide cannulas into the vMPFC. Seventy-two hours later, the animals had a polyethylene catheter implanted into the femoral artery which was connected to the acquisition system to blood pressure and heart rate recording in the day-test. A second catheter was implanted into the femoral vein in order to infuse vasoactive drugs. Two TRPV1 receptors antagonists, 6-iodonordihydrocapsaicina (6-IODO) and caspazepine, besides the TRPV1 agonist, capsaicin, were used. Capsazepine microinjection into the vMPFC reduced the slope of the linear regression of the bardycardic and tachycardic components of the baroreflex. The sigmoid curve parameters were also reduced. Afterwards, the administration of 6-IODO also decreased the slope of the tachycardic and bradycardic responses, as well as the non-linear regression curve parameters. On the other hand, capsaicin bilaterally microinjected into the vMPFC increased the slope in both bradycardic and tachycardic reflex responses as well as the sigmoid curve parameters. Pretreatment of the vMPFC TRPV1 receptors with an ineffective dose of 6-IODO abolished the baroreflex activity increasing induced by capsaicin. In another group of animals, higher doses of capsaicin were administred into the vMPFC 5 minutes after the microinjection of an ineffective dose of 6-IODO. Thus, a doseresponse curve right displacement was observed, with no alteration in the maximum effect level of capsaicin. Beyond that, PL and IL TRPV1 receptors equally modulate baroreceptor reflex arc. In conclusion, the present work shows tha vMPFC TRPV1 receptors are involved in the baroreceptor reflex response

Multiple interactions between dopamine (DA), glutamate, and nitric oxide (NO) in mesolimbic and corticostriatal circuits suggest that NO may play a critical role in cocaine-induced behavioral and neural plasticity. Clinical and preclinical studies have revealed that females and adolescents display unique vulnerabilities to the behavioral and neurochemical effects of cocaine as a result of sex-dependent and ontogeny-dependent differences in dopaminergic systems. Thus, my research objectives were to investigate the contributions of the neuronal nitric oxide synthase (nNOS) gene, ontogeny, and gender on the rewarding and sensitizing effects of cocaine. I found that nNOS significantly influences the rewarding aspects of cocaine in adolescent mice and adult male mice (i.e., major deficits in several phases of cocaine conditioned place preference (CPP) were detected in nNOS knockout (KO) adolescent mice and nNOS KO adult male mice). However, the contribution of nNOS was sex-dependent as CPP phases were normal in KO adult females. In contrast to CPP, I found a major ontogeny-dependent contribution of nNOS to the sensitizing effects of cocaine. Namely, while nNOS is essential for the development of behavioral sensitization in adult males, this type of behavioral plasticity develops independently of nNOS during adolescence. The contribution of nNOS was once again sex-dependent as behavioral sensitization was normal in adult KO females. Together, this line of investigation has revealed that the NO-signaling pathway has a) a sex-dependent role in the neuroplasticity underlying cocaine CPP and b) a sex-dependent and ontogeny-dependent influence on cocaine-induced behavioral sensitization. Stereological and western blot analysis revealed that a sensitizing regimen of cocaine resulted in an increase in nNOS and tyrosine hydroxylase (TH) immunoreactivity in the dorsal striatum (dST) of adult, but not adolescent, wild-type (WT) male mice. In the absence of nNOS, dopaminergic neurons in the ventral tegmental area (VTA) were severely reduced and cocaine caused a downregulation of dST TH suggesting that nitrergic levels modulate TH. Thus, the finding that nNOS is essential for the development of sensitization in adulthood, but not adolescence, together with the fact that cocaine upregulated nNOS and TH in the dST in adult, but not adolescent mice, strongly suggest that the nitrergic system underlies behavioral sensitization through modulation of the dopaminergic system in adulthood. These findings suggest different approaches in the clinical treatment of drug craving and drug-seeking behavior in adolescent and adult patients.

Remembering previously experienced events can happen as a result of an effortful retrieval attempt. At other occasions, a memory can enter our minds without any apparent effort – or, indeed, intention - to retrieve. Although it has long been appreciated that retrieval from episodic memory is intertwined with cognitive control, the neural mechanisms of memory-control interactions remain unclear. In this thesis I have used functional magnetic resonance imaging (fMRI) and scalp-recorded event-related potentials (ERP) to study the neural basis of episodic retrieval at varying levels of cognitive control. The dorsolateral prefrontal cortex (dlPFC) has been suggested to support a cognitive control mechanism (context processing) which is relevant during various situations that demand maintenance of current goals and rules. Although increased dlPFC recruitment with increasing context processing demands has been demonstrated during episodic retrieval, there are relatively few studies directly comparing the engagement of dlPFC during episodic retrieval with that during other task domains. In Study I, context processing demands were amplified in episodic retrieval, auditory attention and emotion regulation tasks. This led to overlapping dlPFC recruitment in the first two domains and a divergent reliance on ventromedial prefrontal cortex in the emotion domain. Thus, when selection between competing representations needs to be carried out in accordance with the currently relevant goals and task rules, the episodic memory system interacts with domain-general cognitive control mechanisms. Studies II and III explored the reactive nature of retrieval-specific control mechanisms: can we flexibly switch between semantic and episodic retrieval based on the information extracted from a retrieval cue? This was studied using a recognition memory task where the relevant information could with equal probability be supplied by the semantic or the episodic memory system. The fMRI results (Study II) showed that the brain activation during the ‘episodic’ but not the ‘semantic’ trials was expressed in the right prefrontal cortex. As the order of trials was unpredictable, the corresponding changes in brain activation might be evoked by differences in early cue-trace interactions. An event-related potential study (Study III) with the same experimental protocol as in Study II showed that neural processing corresponding to the two trial types diverged as early as in the time window 100-140 ms post-cue onset, thus highlighting the importance of early cue-trace matching in the selection of further retrieval processing. Study IV explored incidental episodic retrieval. Although this form of retrieval is a common experience in everyday life and a disturbing symptom in some psychiatric conditions, it is not clear how such spontaneous expressions of memory are initiated and to what extent the prefrontal cortex is engaged. The fMRI results showed, consistent with Study I, that dlPFC is specifically associated with the intention to retrieve, independently of success. Retrieval success engaged similar networks for incidentally as well as intentionally retrieved memories, comprising the hippocampus, precuneus, ventrolateral PFC, and the anterior cingulate cortex. Collectively, the fMRI and ERP results indicated that incidental retrieval was initiated by early (< 200 ms) oldness estimation carried out on the semantic information extracted from the retrieval cues. Taken together, the results of this thesis indicate that episodic retrieval can be initiated via two routes:  a bottom-up input rising early during the cue processing, and a top-down input provided by the cognitive control processes mediated by the prefrontal cortex.

The aim of this doctoral thesis was to study neuropsychological function in relation to structural and functional brain changes in Alzheimer´s disease (AD). In the first study relations between hippocampal volume, neuropsychological function and limbic-hypothalamic-pituitary-adrenal (LHPA) axis disturbances in AD were investigated with magnetic resonance imaging (MRI). Reduced hippocampal CA1 volume and suppressed cortisol levels in combination, best predicted the variation in neuropsychological performance. The conclusion was that reduced hippocampal volume and LHPA axis disturbances are associated to level of cognitive function in AD. The second study focused on whether patients with early AD showed an altered regional cerebral blood flow (rCBF) pattern compared to control persons, correlation between performance on memory tests and rCBF in sub-lobar volumes of the brain were investigated. The rCBF was measured with single photon emission computed tomography (SPECT). AD-patients showed a significantly lower rCBF in temporoparietal regions including left hippocampus compared to controls. The diagnostic sensitivity and specificity for AD was high in temporoparietal regions. AD-patients had significantly lower performance on semantic and, in particular, episodic memory-tests compared to the controls, and their performance on several episodic tests correlated with rCBF in parietal and temporal regions including left hippocampus, which suggest that abnormalities in the rCBF pattern underlie impaired episodic memory functioning in AD. The conclusion was that an observer-independent analyzing method for SPECT with sub-lobar volumes VOI´s is promising in the diagnosis of AD. In a third study possible differences in memory-related functional brain activation between persons with high versus low risk for AD were examined with functional magnetic resonance imaging (fMRI). The high-risk individuals performed worse than low-risk individuals on tests of episodic memory. Patterns of brain activity during episodic encoding and retrieval showed significant group differences. During both encoding and retrieval, the low-risk persons showed increased activity relative to a baseline condition in prefrontal and hippocampal brain regions that previously have been implicated in episodic memory. By contrast, the high-risk persons did not significantly activate any prefrontal regions, but instead showed increased activity in visual occipito-temporal regions. The conclusion was that patterns of prefrontal brain activity related to episodic memory differed between persons with high versus low risk for AD, and lowered prefrontal activity may predict subsequent disease. In a final study SPECT was used to map patterns of rCBF in an activated state (an episodic encoding task) and in a rest condition in persons with mild AD and in healthy elderly control persons. A reduction of rCBF in temporoparietal regions that was more pronounced in mild AD in the activated encoding task was observed. The conclusion was that there are rCBF differences between mild AD patients and healthy controls in temporoparietal regions, and the temporoparietal reduction is more pronounced during activation than during rest which might be important in the early diagnosis of AD. Taken together, these findings show that level of neuropsychological function, notably episodic memory, can be systematically related to functional disturbances in the LHPA axis and to the function of temporoparietal and prefrontal brain regions in AD patients. These changes are detectable in patients with risk for AD and in an early phase of AD which suggests that the obtained results might be important for early diagnosis of AD.

Alcohol dependence (alcoholism) is a complex disease influenced by both environmental factors and genetic predisposition. Mouse models have been used to study many alcohol dependence-related traits and the genetics that underlie them. Two of the most commonly used mice in alcohol research are the C57BL/6J (B6) and DBA/2J (D2) inbred strains, which diverge on several alcohol-related traits including the development of acute physical dependence. Here we utilized the B6 and D2 mice as a genetic model of acute physical dependence, coupled with mRNA Differential Display (DD) and cDNA microarray analysis, to uncover the transcriptional response of the brain to an acute dose of alcohol as a function of time. About 150 genetically divergent and alcohol-responsive genes were identified between the whole brains of B6 and D2 mice using DD and were added as additional targets to the mouse microarrays. Microarray analysis of the prefrontal cortex of B6 and D2 mice revealed strain-specific, acute alcohol-responsive transcriptome remodeling manifested as temporal patterns of gene expression. Distinct expression patterns were identified for physiologically relevant alcohol-related consequences including intoxication, withdrawal and neuroadaptation. In silico characterization of the differentially expressed genes showed genotype dependent and independent transcriptional regulation and functional classification. In addition, categorization of differentially expressed genes by their cellular profiles revealed that some of the genes were known to be more highly expressed in either excitatory or inhibitory neuronal cell types. Our results indicate that the B6 and D2 prefrontal cortices have very different cellular and molecular responses to acute alcohol exposure. The specific roles that the genes identified in this study may play in mediating the divergent alcohol-related behavior between the strains warrant further study. / text

The reticular-activating hypofrontality model of acute exercise (RAH) predicts exercise-induced hypoactivity in frontal cortex which mediates executive function. Connors Continuous Performance Test (CCPT) was used to investigate changes in executive function during- and post treadmill running in healthy volunteers (n=30, 15 male). In a randomized order, subjects performed the CCPT at rest, during low- (LI; 63% maximal heart rate; MHR) and moderate intensity (MI; 75% MHR). Separately, subjects then performed isocalorifically matched exercise bouts of LI, MI and high intensity interval training (HIT) consisting of 4x4 min with 90% MHR and 3 min recovery at 60-70% MHR. Repeated measures ANOVAs revealed main effects of exercise intensity for reaction time RT during- (p≤0.001) and post exercise (p≤0.0001). Subsequent analyses showed an overall increase of RT during exercise compared to rest (p≤0.005). RT decreased significantly from rest to post exercise levels in an exercise intensity dependent, linear fashion (p≤0.0001). Commission errors showed a non significant linear trend to increase both during (p=0.057), and post exercise (p=0.052) as a function of intensity. In a follow up study, we sought to relate observed exercise effects to frontal cortex activity through the use of transcranial direct current stimulation (tDCS) (n=4) and transcranial magnetic stimulation (TMS) over the dorsolateral prefrontal cortex (DLPFC). Prior to TMS stimulation cortical excitability was estimated post running through motor-evoked potentials (MEP) elicited from the primary motor cortex (M1) induced by single burst TMS and measured in the first dorsal interosseous (FDI) muscle using electromyography. At rest, inhibitory cathodal tDCS with left DLPFC cathode and right supraorbital anode led to improved reaction time and increased amount of commission errors, whereas anodal stimulatory tDCS in the immediate post exercise period was unable to recover the post exercise effect. Continuous theta burst stimulation over the left DLPFC post running further impaired inhibitory control and facilitated reaction time. Different findings during- and after- exercise suggests that potential contributing mechanisms such as computational and metabolic factors may be differentially active during these respective conditions. Furthermore, the fact that an inhibitory TMS protocol pronounced the post running effects even more and that we were able to mimic the reported RAH effects at rest with inhibitory frontal tDCS, but observed different patterns during exercise, suggests that the latter state cannot be fully explained by reducing activity in the left frontal cortex alone. Failure to modify the after exercise effect with stimulatory tDCS also supports an interplay of different factors and might emphasize the strong, robust effects of exercise that cannot simply be attenuated by current application. Increases in MEP post running for 35min paired with the observed performance decrements imply an excited state of M1 and might serve as an explanatory cross-link to central fatigue suggesting that a hypofrontal state might enhance the motor cortical drive to activate muscles.

Introduction. Numerous studies have suggested that maternal care can influence the development and expansion of an individual's self-esteem. Yet the neural mechanisms of this relationship remain unexplored. Incidentally, it has already been demonstrated that a brain region, namely the Hippocampus (HC) is associated with both self-esteem and maternal care. Thus suggesting that there may be a three-way relationship. This also provided the impetus to speculate that a similar interaction could be observed in other brain regions like for example, the Dorsolateral Prefrontal cortex (DLPFC) and the Medial Prefrontal Cortex (MPFC). Therefore, the aim of this study is to scrutinize the possible relationship between mother care, self-esteem and neural correlates including the DLPFC, MPFC and HC, with emphasis on how normal variations in mother care could have consequences for the relationship between self-esteem and particularly the prefrontal cortices. Methods . Fifty-one subjects were recruited on the basis of their maternal scores, as assessed by the Parental Bonding Index and were consequently assigned to either a high mother care (MOCA) or low MOCA group. Their self-esteem was measured through various self-esteem scales including the Rosenberg self-esteem scale. The structural integrity of the regions was ascertained through the use of both manual and semi automated segmenting procedures. Results . Initial Bivariate correlations reported a negative association between DLPFC volumes and self-esteem in the high MOCA group while HC was positively associated with self-esteem in both high and low MOCA groups. There were no associations to report for the MPFC. Additional analysis revealed that the Biregional association was sex specific. Discussion. For the first time, we were successful in associating DLPFC volume with self-esteem. In addition, we successfully replicated the association between self-esteem and HC volume. This study could provide an indication how of maternal care could have a sex specific affect not only on the evolution of self-esteem, but also on the regions they may be targeting.

When given a choice between getting a high reward that requires climbing a high ramp or pressing a lever multiple times, versus freely obtaining a low reward, healthy rats prefer the former, while rats with lesions to the anterior cingulate cortex (ACC) prefer the latter. We developed two novel effort tasks to examine if ACC mediates other types of physical effort (weight-lifting) as well as emotional effort (courage). We replicated previous findings on a modified version of the ramp-climbing task, showing that ACC lesions impair these decisions. Lesions of ACC did not impair weight-lifting effort, even when higher levels of effort were used and training on the task was eliminated. Initially, lesions of ACC did not impair courage effort. When the task effort was subsequently increased, rats with ACC lesions showed a failure to adapt to novelty throughout testing. This research indicated that not all effort is mediated by ACC. / xii, 177 leaves : ill. ; 29 cm

Fragile X Syndrome (FXS) is the leading cause of inherited intellectual disability. The disorder is caused by a trinucleotide expansion that silences the Fragile X Mental Retardation 1 (Fmr1) gene resulting in the loss of its protein product, the Fragile X Mental Retardation Protein (FMRP). FXS patients show broad clinical phenotypes including intellectual disability, as well as a number of cognitive and behavioral problems. The lack of FMRP is believed to be the direct cause of the deficits seen in FXS patients. FMRP is an RNA-binding protein that is expressed in the brain and testes. This protein is believed to form a messenger ribonucleoprotein complex with mRNAs in the nucleus and subsequently export them to polyribosomes in the cytoplasm, therefore influencing translation of its bound mRNAs. Importantly, FMRP has long been suspected to be involved in synaptic plasticity due to its ability to bind several mRNAs that encode for proteins important in synaptic plasticity. Such proteins include the GluN1, GluN2A and GluN2B subunits of the N-methyl-D- aspartate receptor (NMDAR). FMRP is expressed in the hippocampus, a region of the brain involved in learning and memory processes. Recently, impaired NMDAR functioning in the dentate gyrus (DG) subregion of the hippocampus has been observed in Fmr1 knockout (-/y) mice. This impairment also resulted in reduction in long-term potentiation (LTP) and long-term depression (LTD) of synaptic efficacy, two biological models of learning and memory. In the present study, I focused on the levels of the NMDAR GluN1, GluN2B and Glu2B subunits in order to determine the synaptic plasticity alterations seen in the DG of Fmr1-/y mice. Using Western blotting, I found that there is a decrease in the GluN1, GluN2A and GluN2B subunits in the DG of young adult Fmr1-/y mice, indicating that these mice have significantly lower amounts of total NMDARs. These results could explain the altered LTP and LTD seen in Fmr1-/y mice at the molecular level and might contribute to the intellectual impairments seen in these KO mice. NMDARs appear to be important in the development and maturation of synapses. The GluN2A and GluN2B subunits are developmentally regulated, where GluN2B is predominantly expressed early in development and GluN2A in the adult brain. A dysregulation of GluN2A and GluN2B subunits has been proposed to affect the maturation and formation of synapses. Intriguingly, FMRP is also believed to play a functional role in early brain development. Thus, this study also focused on the developmental expression of the GluN1, GluN2A and GluN2B subunits in the DG, Cornu Ammonis, prefrontal cortex and cerebellum of Fmr1-/y mice, all of which are brain regions implicated in FXS. We found that the developmental expression of these subunits is altered in Fmr1-/y mice in specific brain regions. Together, these results demonstrate that the loss of FMRP differentially affects GluN1, GluN2A and GluN2B subunit expression both developmentally and spatially, further implicating NMDARs in the pathophysiology of FXS. / Graduate

Lic.-avh. (sammanfattning) Stockholm : Karolinska institutet, 2007. / Härtill 3 uppsatser.