<p>It has been suggested that primate brains are inherently biased towards gathering and processing the social information present in the world. In fact, the neural network that mediates our engagement with the external world - the default mode network (DMN) ¬- is strongly convergent with the neural circuitry for social cognition. The posterior cingulate (PCC) is believed to be a key node in both the DMN and in social cognition. Human and non-human primate studies have demonstrated a role for the PCC in outcome monitoring: it tracks rewards, subjective values of choices, task engagement and global choice strategies. It is also implicated in social cognition. Human studies show that PCC activity varies with the recall of autobiographical memories and exposure to social stimuli. While several electrophysiological studies explicate the response of PCC neurons to non-social outcome monitoring and valuation, there is a lack of similar studies for social valuation. This thesis is concerned with characterizing the neuronal responses in the PCC to social stimuli and determining whether social valuation occurs in the PCC in a manner similar to that previously described for non-social outcomes. I recorded the single unit activity of neurons in the PCC of rhesus macaques while they performed behavioral tasks that required attending to the faces of high-status or low-status individuals. Monkeys valued the faces of high-status individuals more than low-status individuals, though they were equally likely to identity and overtly attend to faces of both social classes. This differential valuation of face stimuli was represented in the firing activity of PCC neurons, with higher neuronal activity seen in response to subordinate faces as compared to dominant ones. Cells in the PCC did not track the individual identity of the presented faces. Furthermore, neuronal activity in the PCC predominantly tracked social value, and not non-social reward delivery as previously reported. Neuronal activity also predicted task engagement, with higher firing rates being predictive of a decrease in task engagement. To summarize, the PCC is biased towards social information processing, and neuronal activity in the PCC tracks social category information and the level of task engagement.</p> / Dissertation

Antipsychotic drugs (typical and atypical) are used in the treatment of mental disorders such as schizophrenia. Typical antipsychotic drugs (such as haloperidol) specifically target dopamine D2 receptors and produce extrapyramidal side effects. Atypical antipsychotic drugs (such as risperidone and olanzapine) primarily target dopamine D2 and serotonin 5HT2A receptors and produce fewer extrapyramidal symptoms (EPS) than do the typical antipsychotic drugs at clinically effective doses (Meltzer and Nash, 1991). It has been proposed that the prefrontal cortex (a brain region implicated in the pathophysiology of schizophrenia) is the locus of antipsychotic drug action to improve cognitive dysfunction and negative symptoms of schizophrenia (Weinberger and Lipska, 1995; Jakab and Goldman-Rakic, 1998). Moreover, it is possible that the effects in the prefrontal cortex may contribute to the differences between typical and atypical antipsychotic drugs as well as differences among atypical antipsychotic drugs (Horacek et al., 2006). The core pathology associated with the dorsolateral prefrontal cortex includes reduced cerebral volume, increased ventricle size and deficits in neuronal morphology, including increased cell packing density, reduction in dendrites and its associated dendritic spines (Selemon and Goldman-Rakic, 1999). However, since most neuropathology data emerge from in vivo imaging and post-mortem studies of patients with schizophrenia, it is difficult to interpret and distinguish between findings that have an etiological or iatrogenic basis. Thus, the objective of the current study was to examine the effects of antipsychotic drugs, at therapeutically relevant concentrations, in a rat brain region that is homologous to that of the human dorsolateral prefrontal cortex. The hypothesis upon which this study was based is that haloperidol, risperidone and olanzapine (at 65 to 80% striatal dopamine D2 receptor occupancy) induce changes to pyramidal cell architecture in the rat anterior cingulate cortex (Vogt and Gabriel, 1993; Hoover and Vertes, 2007). This hypothesis was investigated by (a) determining doses that are within the therapeutic range (65 to 80% striatal dopamine D2 receptor occupancy) by measuring the occupancy of haloperidol, risperidone and olanzapine in the presence of 3H-raclopride ( a dopamine D2 receptor antagonist) at dopamine D2 receptors in the rat striatum; and (b) examining whether therapeutic doses of antipsychotic drugs in rats cause neuropathology comparable to that observed in human post-mortem brains of patients with schizophrenia. Antipsyhcotic drug doses were selected using an appropriate in vivo dopamine D2 receptor occupancy method. The findings from this study revealed that 0.25 mg/kg/day haloperidol, 5 mg/kg/day risperidone and 10 mg/kg/day olanzapine achieved therapeutically relevant rat striatal dopamine D2 receptor occupancy in the range of 65 to 80%. To determine whether antipsychotic drugs at therapeutic doses established above induce changes in neuronal cell density and morphology; immunohistochemistry, single cell injection of lucifer yellow dye and Golgi-Cox impregnation of layer II/III pyramidal cells was performed. The results from these experiments revealed that the density of cells expressing NeuN, parvalbumin, calretinin or calbindin is highly unlikely to be affected by chronic exposure to haloperidol, risperidone and olanzapine. The current study evaluated the effects of chronic antipsychotic drug exposure on spontaneous locomotor activity of a rat in a novel environment. The purpose of this study was to differentiate between a direct and an indirect drug effect. It was found that at the doses established above, risperidone and olanzapine did not overtly reduce spontaneous locomotor activity of a rat in a novel environment relative to controls. In contrast, haloperidol reduced spontaneous locomotor activity of rat in an open field, although this was not statistically significant. Nevertheless, the data reported here allowed us to conclude that the level of activity across groups is unlikely to affect the data obtained in subsequent studies investigating the effects of chronic antipsychotic drug treatment on pyramidal cell structure. Intracellular injection of lucifer yellow dye into pyramidal cells revealed that chronic haloperidol treatment (28 days) was associated with a relative increase in basal dendritic arborisation, but neither of these drug treatments induced changes in arborisation that were different from controls. No statistically significant change in the basal dendritic arbor was detected with animals treated with risperidone relative to controls. Similarly using the Golgi-impregnation method, changes in soma size, dendritic branching, total number of branches and the density of dendritic spines in antipsychotic drug treated groups were not significantly different to controls. Taken together, this finding indicates that only relatively subtle neuritic changes may be attributed to chronic treatment with typical or atypical antipsychotic drugs administered at doses that avhieved striatal dopamine D2 receptor occupancy in the range of 65 to 80%. In summary, this study confirms that antipsychotic drugs are unlikely to induce changes to neuronal cell density or morphology in the rat anterior cingulate cortex at therapeutically relevant doses. Hence, it can be concluded that the observed neuropathology, found in the brains of patients with schizophrenia that have undergone antipsychotic drug therapy, is more likely to be caused by the disease and not the effects of the concomitant drug therapy.

The anterior cingulate cortex (ACC) is part of the cognitive and emotional brain circuitry that mediates social interaction. Imbalances between inhibitory, GABAergic neurons, and excitatory, glutamatergic neurons, in this region are essential to brain circuity during social responses and are thought to be involved with behaviors associated with autism spectrum disorder (ASD). Enriched cell populations of glutamatergic neurons, obtained through laser capture microdissection, were used for gene expression studies of GABAergic receptors (GABRA1, GABRA4, and GABBR1). Additionally, proteins that impact GABAergic synapses (Spinophilin, CPLX1, mTOR, IGF1R, PSD95, PARP1) were investigated using Western Blotting with punchdissected homogenate brain tissue from ACC and frontal cortical brain regions. No significant differences in gene expression nor protein were identified between ASD and control brain donors. Evidence of GABAergic synaptic pathology was not found; however, future studies of alternative GABAergic markers and increased study numbers are needed to confirm these findings in ASD human tissue.

Background: Altered brain morphology was one of the first pathobiological findings associated with autism spectrum disorder. These gross abnormalities, documented in both white and gray matter areas in autistic brains, are postulated to contribute to disrupted neuronal communication. For example, glutamatergic pyramidal neurons in the anterior cingulate cortex (ACC) have decreased size and increased cell density in autism. Objectives: We sought to determine whether autism-related gene expression abnormalities exist in the ACC that might underlie previously observed cell morphological alterations found in this brain region. Specifically, levels of expression of genes associated with glutamatergic neurotransmission were measured in pyramidal neurons and surrounding astrocytes in the ACC of postmortem brain tissues from autism donors and matched developmentally normal control donors. Methods: Postmortem brain tissues were obtained from 6-8 age-matched pairs of male subjects who had autism and developmentally normal control males (age range 6-37). Laser-guided microdissection was used to capture pure populations of pyramidal neurons and astrocytes from layer III of the ACC. The expression of glutamate-related genes was measured in RNA isolates by reverse transcription followed by end-point PCR using three stable reference genes to normalize expression levels. Results: ACC pyramidal neurons from autism subjects demonstrated significantly reduced gene expressions of the obligatory glutamatergic NMDA receptor subunit NR1, a glutamate transporter SLC1A1, and the glutamate receptor anchoring protein GRIP1. There was also a robust reduction in the gene expression of the brain-derived neurotrophic factor (BDNF) receptor NTRK2 in autism pyramidal neurons, with gene expression levels of BDNF itself unaffected. No gene expression abnormalities were observed in ACC astrocytes surrounding the pyramidal neurons from autistic subjects. Conclusions: Autism spectrum disorder is associated with a reduction in the expression of genes associated with glutamatergic neurotransmission and downstream BDNF signaling in pyramidal neurons of the ACC. These findings suggest that glutamatergic signaling is compromised in these excitatory neurons in autism and raise hope that drugs or other treatments may be developed to overcome these pathobiological deficits.

A hallmark of higher-order cortical regions is their functional heterogeneity, but it is not well understood how these areas are able to encode diverse behavioral information. The anterior cingulate cortex (ACC), for example, is known to be important in a large range of behaviors, including, decision making, emotional regulation and social cognition. In support of this, previous work shows activation of the ACC to anxiety-related and social stimuli but does not use cellular resolution or cell-type specific techniques to elucidate the possible heterogeneity of its subcircuits. In this work, I investigate how subpopulations of neurons or microcircuits within the ACC encode these different kinds of stimuli. One type of inhibitory interneuron, which is positive for vasoactive intestinal peptide (VIP), is known to alter the activity of clusters of pyramidal excitatory neurons, often by inhibiting other types of inhibitory cells. Prior to this research, it was unknown whether the activity of VIP cells in the ACC (VIPACC) encodes anxiety-related or social information and whether all VIPACC activate similarly to the same behavioral stimuli. Using in vivo Ca2+ imaging and 3D-printed miniscopes in freely behaving mice to monitor VIPACC activity, I have identified distinct subpopulations of VIPACC that preferentially activate to either anxiogenic, anxiolytic, social, or non-social stimuli. I also demonstrate that these stimulus-selective subpopulations are largely non-overlapping and that clusters of cells may co-activate, improving their encoding. Finally, I used trans-synaptic tracing to map monosynaptic inputs to VIP and other interneuron subtypes in the ACC. I found that VIPACC receive widespread inputs from regions implicated in emotional regulation and social cognition and that some inputs differ between types of ACC interneurons. Overall, these data demonstrate that the ACC is not homogeneous – there is marked functional heterogeneity within one interneuron population in the ACC and connective heterogeneity across ACC cell types. This work contributes to our broader understanding of how the cortex encodes information across diverse contexts and provides insight into the complexity of neural processes involved in anxiety and social behavior.

京都大学 / 新制・課程博士 / 博士(医学) / 甲第24842号 / 医博第5010号 / 新制||医||1068(附属図書館) / 京都大学大学院医学研究科医学専攻 / (主査)教授 髙橋, 良輔, 教授 林, 康紀, 教授 井上, 治久 / 学位規則第4条第1項該当 / Doctor of Medical Science / Kyoto University / DFAM

Bakgrund: Smärta definieras som en subjektiv upplevelse där upplevelsen till viss del formas i hjärnan genom komplexa processer. Långvarig stress har visat sig leda till förändring i smärtkänsligheten vilket kanske förklaras av att akut stress förändrar aktivitet i främre delar av hjärnan. Anterior cingulate cortex (ACC) är ett frontalt hjärnområde med en roll i den emotionella upplevelsen av smärta. Det finns indikationer på förändringar i ACC av den hämmande transmittorsubstansen GABA, och den stimulerande transmittorsubstansen glutamat, vid vissa smärttillstånd.  Motiv: I dagsläget saknas kunskap om hur stress påverkar smärtkänslighet samt hur det påverkar grundnivåerna av transmittorsubstanserna GABA och glutamat.  Syfte: Att studera samband mellan skattad stress och skattad smärta, samt studera samband mellan skattad stress, smärta, GABA och glutamat i två ACC regioner.  Metod: En experimentell pilotstudie med kvantitativ design utfördes med 10 friska deltagare. Percieved Stress Questionnaire användes för skattning av stressnivåer före smärtprovokation och Numeric Rating Scale användes för att skatta smärta vid smärtprovokation. GABA- och glutamatnivåer i två ACC regioner mättes med hjälp av Magnetic Resonans Spectroscopi.  Resultat: Spearmans test visade att det fanns ett signifikant positivt samband mellan skattad stress och skattad smärta (r=.86, p=.001). Det fanns även signifikant positivt samband mellan skattad stress och glutamat (r=.778, p=.008), skattad smärta och glutamat (r=.729, p=.017). Samt ett signifikant negativt samband mellan skattad stress och GABA (r= -.687, p=.028), skattad smärta och GABA (r=-.667, p=.035) i två ACC regioner.  Konklusion: Resultatet indikerar att sambandet mellan stress och smärta kan förklaras av förändringar i transmittorsubstansnivåer i två ACC regioner. Denna kunskap kan bidra till ökad förståelse hos vårdpersonalen för individuella skillnader i smärtkänslighet och hur komplex situationen kring patienter med smärta är, vilket motiverar till omvårdnadsåtgärder som minskar stress och smärta. / Background: Pain is defined as a subjective experience that some extent is formed through complex processes in the brain. Prolonged stress can affect pain sensitivity, which may be explained by changes in frontal parts of the brain. The anterior cingulate cortex (ACC) is a frontal brain area that plays a role in the emotional experience of pain. In certain pain conditions, there are indications of changes in the neurotransmitter level GABA and glutamate in ACC. Motive: At present, there is a lack of knowledge about how stress affects pain sensitivity and how it affects the basic levels of the neurotransmitter GABA and glutamate in ACC.  Aim: To study the correlation between rated stress and pain, and study the correlation between rated stress, pain, GABA, and glutamate in ACC.  Methods: An experimental pilot study was performed with 10 healthy participants. The Perceived Stress Questionnaire was used to rate stress levels before pain provocation and the Numeric Rating Scale was used to rate pain during pain provocation. GABA and glutamate levels were measured in ACC by Magnetic Resonance Spectroscopy.  Result: Spearman´s test showed a significant positive correlation between rated stress and rated pain (r = .86, p = .001). There was a significant positive relationship between rated stress and glutamate (r = .778, p = .008), rated pain and glutamate (r = .729, p = .017) and a significant negative correlation between rated stress and GABA (r = -.687, p = .028), rated pain and GABA (r = -.667, p = .035) in ACC.  Conclusion: The results indicate that the correlation between stress and pain can be explained by changes in transmitter levels in the ACC region. This knowledge can contribute to increased understanding among healthcare professionals for individual differences in pain sensitivity and the complexity of pain conditions.

We humans depend heavily on cognitive control to make decision and execute goal-directed behaviors, without which our behavior would be overpowered by automatic, stimulus-driven responses. In my dissertation, I focus on a brain region most implicated in this crucial process: the anterior cingulate cortex (ACC). The importance of this region is highlighted by lesion studies demonstrating diminished self-initiated behavior, or apathy, following ACC damage, the most severe form of which results in the near complete absence of speech production and willed actions in the presence of intact motor ability. Despite decades of research, however, its precise function is still highly debated, due particularly to ACC’s observed involvement in multiple aspects of cognition. In my dissertation I examine ACC function according to recent developments in reinforcement learning theory that posit a key role for ACC in motivating extended behavior. According to this theory, ACC is responsible for learning task values and motivating effortful control over extended behaviors based on those learned task values. The aim of my dissertation is two-fold: 1) to improve understanding of ACC function, and 2) to elucidate the contribution of ACC to depression, as revealed by individual differences in several personality traits related to motivation and reward sensitivity in a population of healthy college students. It was hypothesized that these different personality traits express, to greater or lesser degrees across individuals, ACC function, and that their abnormal expression (in particular, atypically low motivation and reward sensitivity) constitute hallmark characteristics of depression. First, this dissertation reveals that reward positivity (RewP), a key electrophysiological signature of reward processing that is believed to index the impact of reinforcement learning signals carried by the midbrain dopamine system on to ACC, is sensitive to individual differences in reward valuation, being larger for those high in reward sensitivity and smaller for those high in depression scores. Second, consistent with a previous suggestion that people high in depression or depression scores have difficulty using reward information to motivate behavior, I find these individuals to exhibit relatively poor prolonged task performance despite an apparently greater investment of cognitive control, and a reduced willingness to expend effort to obtain probable rewards, a behavior that was stable with time on task. In contrast, individuals characterized by high persistence, which is indicative of good ACC function, exhibited high self-reported task engagement and increasing effortful behaviors with time on task, particularly for trials in which reward receipt was unlikely, suggesting increased motivational control. In sum, this dissertation emphasizes the importance of understanding the basic function of ACC as assessed by individual differences in personality, which is then used to understand the impact of its dysfunction in relation to mental illnesses. / Graduate

The aims of the thesis were to examine i) whether the endogenous opioid system (EOS) is lateralized in human brain areas involved in processing of emotions and pain; ii) whether EOS responses to unilateral brain injury depend on side of lesion, and iii) whether in human alcoholics, this system is involved in molecular adaptations in brain areas relevant for cognitive control of addictive behavior and habit formation. The main findings were that (1) opioid peptides but not opioid receptors and classic neurotransmitters are markedly lateralized in the anterior cingulate cortex involved in processing of  positive and negative emotions and affective component of pain. The region-specific lateralization of neuronal networks expressing opioid peptides may underlie in part lateralization of higher functions in the human brain including emotions and pain. (2) Analysis of the effects of traumatic brain injury (TBI) demonstrated predominant alteration of dynorphin levels in the hippocampus ipsilateral to the injury, while injury to the right hemisphere affected dynorphin levels in the striatum and frontal cortex to a greater extent than that to the left hemisphere. Thus, trauma reveals a lateralization in the mechanisms mediating the response of dynorphin expressing neuronal networks in the brain. These networks may differentially mediate effects of left or right brain injury on lateralized brain functions. (3) In human alcoholics, the enkephalin and dynorphin systems were found to be downregulated in the caudate nucleus and / or putamen that may underlie in part changes in goal directed behavior and formation of a compulsive habit in alcoholics. In contrast to downregulation in these areas, PDYN mRNA and dynorphins in dorsolateral prefrontal cortex, k-opioid receptor mRNA in orbitofrontal cortex, and dynorphins in hippocampus were upregulated in alcoholics. Activation of the k-opioid receptor by upregulated dynorphins may underlie in part neurocognitive dysfunctions relevant for addiction and disrupted inhibitory control. We conclude that the EOS exhibits region-specific lateralization in human brain and brain-area specific lateralized response after unilateral TBI in mice; and that the EOS is involved in adaptive processes associated with specific aspects of alcohol dependence.

A dor é um fenômeno multidimensional, que geralmente desencadeia reações emocionais desconfortáveis quando identificada. Sua relação com injúria tecidual pode ser interpretado como um mecanismo adaptativo de defesa à integridade do organismo, tendo em vista sua preservação evolutiva. Porém, o substrato neurobiológico do organismo parece determinar a complexificação do repertório comportamental em diferentes espécies. Nesse sentido, o córtex cingulado anterior (CCA) tem sido amplamente descrito em mamíferos modulando diferentes aspectos da dor. O presente trabalho utilizou os testes algesimétricos de vocalização e da formalina em cobaias, para se avaliar o decurso temporal do efeito da microinjeção de agonistas e antagonistas GABAérgico (muscimol e bicuculina); colinérgico (carbacol e atropina) e opioidérgico (morfina e naloxona). A microinjeção de bicuculina (1 nmol / 0,2 µl) exacerbou as respostas nociceptivas em ambos os testes, porém diferentes doses de muscimol (0,5, 1 e 2 nmol / 0,2 µl), não modificaram as respostas. O efeito da bicuculina foi bloqueado em ambos os testes pela microinjeção prévia de muscimol (1 nmol/ 0,2 µl) no CCA. A microinjeção de carbacol (2,7 nmol /0,2 µl) neste substrato promoveu antinocicepção, evidenciada por meio da atenuação da amplitude das vocalizações, mas não pelo teste da formalina. Esse efeito foi bloqueado pela administração prévia de atropina (0,7 nmol /0,2 µl) e de naloxona (2,7 nmol /0,2 µl). A microinjeção de morfina (4,4 nmol /0,2 µl) promoveu antinocicepção em ambos os testes. Concluímos que a inibição do tônus GABAérgico no CCA exacerba os comportamentos nociceptivos e que a antinocicepção promovida por carbacol pode ter sido mediada pelo sistema de opióides endógenos, tendo em 9 vista o bloqueio do seu efeito com naloxona. Além disso, a estimulação opióide promove uma contundente antinocicepção. / Pain is a multidimensional phenomenon which usually triggers uncomfortable emotional reactions when identified. Its relation injury can be interpreted as an adaptive mechanism to defend the integrity of the body given its evolutionary conservation. However the neurobiological substrate of the body seems to determine the complexification of behavioral repertoire in different species. Thus, the anterior cingulated cortex (ACC) has been widely described in mammals by modulating different cognitive aspects of pain. This study used algesimetric tests of vocalization and formalin in guinea pigs to evaluate the time course of the effect of microinjection of GABA agonists and antagonists (bicuculline and muscimol) and cholinergic (carbachol and atropine) beyond the opioid antagonist naloxone. The microinjection of bicuculline (1 nmol / 0,2 µl) exacerbated the nociceptive behavior in both tests but different doses of muscimol (0,5; 1 e 2 nmol / 0,2 µl) did not change the responses. The effect of bicuculline was blocked in both tests by prior microinjection of muscimol (1 nmol / 0,2 µl) in the ACC. The microinjection of carbachol (2,7 nmol / 0,2 µl) on this substrate promoted antinociception as evidenced by attenuation of the amplitude of the vocalizations, but not by the formalin test. This effect was blocked by prior administration of atropine (0,7 / 0,2 µl) and naloxone (0,7 nmol / 0, 2 µl). The microinjection of morphine (4,4 nmol / 0,2 µl) promoted antinociception in both tests. We conclude that inhibition of GABAergic tone in the ACC exacerbates nociceptive behaviors and that the antinociception promoted by carbachol may 11 have been mediated by endogenous opioid system in order blocking its effect with naloxone. In addition opioid stimulation promotes a striking antinociception.