<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

Abstract In the 1990s researchers discovered task-deactivated regions in the human brain. Together, these areas make up the default mode network (DMN). It was originally proposed to act as a balancing mechanism between different brain systems, explaining the deactivations, but is now mostly studied with regards to internal awareness, such as daydreaming and mental imagery. The purpose of this thesis is to present a summary of DMN research, focusing on the network’s suggested role in internal awareness. This will be done by reviewing a wide variety of research that either explicitly or indirectly correlate default mode network features with aspects of consciousness and internal awareness. The subjective experience of being conscious have been a source of argument primarily among philosophers, but the qualities we feel are intimately linked to cognitive functions that are supported by the regions found in the DMN. Cognitive neuroscience may therefore be able to contribute to the concept of internal awareness and consciousness.

It is well documented that adolescent substance use is associated with deficits in brain function and behavior. However, possible deficits that predate substance use initiation remain poorly characterized in preadolescents at-risk for developing substance use disorder (SUD). To characterize potential brain and behavioral differences that predate substance use, substance naïve preadolescents, ages 11–12, were recruited into three groups to complete functional magnetic resonance imaging delay discounting: (1) High-risk youth (n=35) with a family history of SUD and externalizing psychiatric disorders, (2) psychiatric controls (n=35) with no family history of SUD, but equivalent externalizing psychiatric disorders as high-risk youth, and (3) healthy controls (n=29) with no family history of SUD and minimal psychopathology. While no behavioral differences between groups were identified, there were group differences in posterior cingulate cortex (PCC) function during decision making. Specifically, the high-risk group showed stronger deactivation of the PCC than healthy controls. These results suggest that high-risk preadolescents may need to suppress activity of key nodes of the default mode network (a task negative network) to a greater extent to properly allocate attention to the task.

Indiana University-Purdue University Indianapolis (IUPUI) / It is well documented that adolescent substance use is associated with deficits in brain function and behavior. However, possible deficits that predate substance use initiation remain poorly characterized in preadolescents at-risk for developing substance use disorder (SUD). To characterize potential brain and behavioral differences that predate substance use, substance naïve preadolescents, ages 11–12, were recruited into three groups to complete functional magnetic resonance imaging delay discounting: (1) High-risk youth (n=35) with a family history of SUD and externalizing psychiatric disorders, (2) psychiatric controls (n=35) with no family history of SUD, but equivalent externalizing psychiatric disorders as high-risk youth, and (3) healthy controls (n=29) with no family history of SUD and minimal psychopathology. While no behavioral differences between groups were identified, there were group differences in posterior cingulate cortex (PCC) function during decision making. Specifically, the high-risk group showed stronger deactivation of the PCC than healthy controls. These results suggest that high-risk preadolescents may need to suppress activity of key nodes of the default mode network (a task negative network) to a greater extent to properly allocate attention to the task.

Contexte : Jusqu’à 90% des fumeurs qui tentent d’arrêter de fumer vont rechuter dans l’année suivant la date d’arrêt. L’impulsivité, au même titre que le « craving », a démontré être un bon facteur de prédiction de la rechute tabagique. Ainsi, la présente étude visait à évaluer, à l’aide de la neuroimagerie fonctionnelle, l’influence de l’impulsivité sur les mécanismes neuronaux du « craving » de la cigarette. Parmi les régions cérébrales impliquées dans le « craving » de la nicotine, les cortex préfrontal dorsolatéral, orbitofrontal et cingulaire sont d’importantes structures dans les processus de contrôle de soi. Méthodes : 31 fumeurs chroniques ont passé une session de neuroimagerie durant laquelle ils devaient regarder des images appétitives de cigarettes et des images neutres. Ils ont ensuite dû inscrire le « craving » ressenti à la vue des images et répondre à un questionnaire portant sur les traits de personnalité de l’impulsivité (BIS-11). Résultats : Tel qu’attendu, le score d’impulsivité était positivement corrélé au « craving » rapporté par les participants à la vue d’images de cigarettes. Au niveau cérébral, plus les fumeurs présentaient de forts traits d’impulsivité, moins grande était l’activité du cortex cingulaire postérieur (CCP) durant le « craving ». Enfin, l’activité du CCP présentait une connectivité fonctionnelle négative avec l’insula, le cortex préfrontal dorsolatéral et le cortex cingulaire antérieur. Conclusions : Comme le CCP est le siège des processus de mentalisation et de référence à soi, nous suggérons que plus les fumeurs étaient impulsifs, moins ils prenaient conscience de leur état et moins ils en exerçaient un contrôle, donc plus ils ressentaient de forts « cravings ». En poussant plus loin, nos résultats mettent l’accent sur l’aspect identitaire (le soi, les mémoires autobiographiques) et l’aspect d’introspection en toxicomanie : deux avenues à explorer. / Background: 90% of cigarette smokers attempting to quit smoking relapse by one-year following their quit date. Impulsivity, as well as cue-induced cravings, have been shown to be good predictors of relapse for tobacco smoking; however, no study to date has examined their interaction and its neural substrates. The goal of this study was to determine the neural influence of trait impulsivity during functional imaging of cue-induced cigarette cravings. Among the brain regions involved in nicotine craving, the dorsolateral prefrontal cortex, the orbitofrontal as well as the cingulate cortex all play a significant role in self-control processes. Methods: Thirty-one chronic smokers passively viewed appetitive smoking-related and neutral images while being scanned. Participants also reported their level of craving and completed the BIS-11, a measure of trait impulsivity. Results: As hypothesized, we observed a significant positive relationship between impulsivity scores and reported craving. Impulsivity scores were negatively correlated with activity in the posterior cingulate cortex (PCC). The insula, dorsal anterior cingulate cortex and dorsolateral prefrontal cortex presented a negative connectivity with the PCC. Conclusions: Given that the PCC is involved in mentalization and self-relevant processing, it is possible that greater trait impulsivity in smokers is associated to a lower tendency to understand and use one’s mental and physical state to guide behavior. This may weaken their capacity for self-control and consequently, promotes more automatic and stronger cue-elicited smoking urges. Furthermore, our results highlight the important but undervalued role of identity (the self and autobiographic memories) and mindfulness in addiction.

Contexte : Jusqu’à 90% des fumeurs qui tentent d’arrêter de fumer vont rechuter dans l’année suivant la date d’arrêt. L’impulsivité, au même titre que le « craving », a démontré être un bon facteur de prédiction de la rechute tabagique. Ainsi, la présente étude visait à évaluer, à l’aide de la neuroimagerie fonctionnelle, l’influence de l’impulsivité sur les mécanismes neuronaux du « craving » de la cigarette. Parmi les régions cérébrales impliquées dans le « craving » de la nicotine, les cortex préfrontal dorsolatéral, orbitofrontal et cingulaire sont d’importantes structures dans les processus de contrôle de soi. Méthodes : 31 fumeurs chroniques ont passé une session de neuroimagerie durant laquelle ils devaient regarder des images appétitives de cigarettes et des images neutres. Ils ont ensuite dû inscrire le « craving » ressenti à la vue des images et répondre à un questionnaire portant sur les traits de personnalité de l’impulsivité (BIS-11). Résultats : Tel qu’attendu, le score d’impulsivité était positivement corrélé au « craving » rapporté par les participants à la vue d’images de cigarettes. Au niveau cérébral, plus les fumeurs présentaient de forts traits d’impulsivité, moins grande était l’activité du cortex cingulaire postérieur (CCP) durant le « craving ». Enfin, l’activité du CCP présentait une connectivité fonctionnelle négative avec l’insula, le cortex préfrontal dorsolatéral et le cortex cingulaire antérieur. Conclusions : Comme le CCP est le siège des processus de mentalisation et de référence à soi, nous suggérons que plus les fumeurs étaient impulsifs, moins ils prenaient conscience de leur état et moins ils en exerçaient un contrôle, donc plus ils ressentaient de forts « cravings ». En poussant plus loin, nos résultats mettent l’accent sur l’aspect identitaire (le soi, les mémoires autobiographiques) et l’aspect d’introspection en toxicomanie : deux avenues à explorer. / Background: 90% of cigarette smokers attempting to quit smoking relapse by one-year following their quit date. Impulsivity, as well as cue-induced cravings, have been shown to be good predictors of relapse for tobacco smoking; however, no study to date has examined their interaction and its neural substrates. The goal of this study was to determine the neural influence of trait impulsivity during functional imaging of cue-induced cigarette cravings. Among the brain regions involved in nicotine craving, the dorsolateral prefrontal cortex, the orbitofrontal as well as the cingulate cortex all play a significant role in self-control processes. Methods: Thirty-one chronic smokers passively viewed appetitive smoking-related and neutral images while being scanned. Participants also reported their level of craving and completed the BIS-11, a measure of trait impulsivity. Results: As hypothesized, we observed a significant positive relationship between impulsivity scores and reported craving. Impulsivity scores were negatively correlated with activity in the posterior cingulate cortex (PCC). The insula, dorsal anterior cingulate cortex and dorsolateral prefrontal cortex presented a negative connectivity with the PCC. Conclusions: Given that the PCC is involved in mentalization and self-relevant processing, it is possible that greater trait impulsivity in smokers is associated to a lower tendency to understand and use one’s mental and physical state to guide behavior. This may weaken their capacity for self-control and consequently, promotes more automatic and stronger cue-elicited smoking urges. Furthermore, our results highlight the important but undervalued role of identity (the self and autobiographic memories) and mindfulness in addiction.

Abstract Neuropsychiatric illnesses usually become overtly manifest in adolescence and early adulthood. A critical long-term aim is to be able to prevent the development of such illnesses, which requires instruments to identify subjects at high risk of illness and to offer them effective interventions. There is an indisputable need for more sophisticated methods to enable more precise detection of adolescents and young adults who are at high risk of developing psychosis. Abnormal function in brain networks has been reported in people with schizophrenia and other psychotic disorders. Similar abnormalities have been found also in people at risk for developing psychosis, but it is not known whether this applies also to spontaneous resting state activity in young people with a familial risk for psychosis. We conducted resting-state functional MRI (R-fMRI) in 72 (29 male) young adults with a history of psychosis in one or both parents (FR) but without psychosis themselves, and 72 (29 male) similarly healthy control subjects without familial risk for psychosis. Both groups in the Oulu Brain and Mind study were drawn from the Northern Finland Birth Cohort 1986. All volunteers were 20–25 years old. Parental psychosis was established using the Care Register for Health Care. R-fMRI data was pre-processed using independent component analysis (ICA). A dual regression technique was used to detect between-group differences with p &lt; 0.05 threshold corrected for multiple comparisons at voxel level. FR subjects demonstrated significantly decreased activity compared to control subjects in the default mode network and in the central executive network and increased activity in the cerebellum. The findings clarify previously controversial literature on the subject. The finding suggests that abnormal activity in these brain networks in rest may be associated with increased vulnerability to psychosis. The findings maybe helpful in developing more precise methods for detecting young people at highest risk for developing psychosis. / Tiivistelmä Psykoottisiin häiriöihin sairastutaan yleensä nuoruudessa tai varhaisaikuisuudessa. Psykoositutkimuksen tavoitteena on löytää uusia menetelmiä, joiden avulla kyettäisiin tunnistamaan suurimmassa psykoosiriskissä olevat nuoret, jotta heille voitaisiin tarjota sairautta ennaltaehkäiseviä hoitokeinoja. Skitsofreniaan ja muihin psykoottisiin häiriöihin sairastuneilla on havaittu aivotoiminnan poikkeavuuksia. Samankaltaisia aivotoiminnan poikkeavuuksia on havaittu myös nuorilla, jotka ovat vaarassa sairastua psykoosiin. Toistaiseksi on ollut epäselvää, onko psykoosiin sairastuneiden henkilöiden lapsilla aivohermoverkkojen toiminnan poikkeavuuksia lepotilassa. Suoritimme aivojen lepotilan MRI-tutkimuksen (R-fMRI) 72:lle (29 miestä) nuorelle aikuiselle, joiden jompikumpi vanhempi oli sairastunut psykoosin sekä 72:lle (29 miestä) nuorelle aikuiselle, joiden vanhemmat eivät olleet sairastaneet psykoosia. Molemmat tutkimusryhmät tässä Oulu Brain and Mind -tutkimuksessa olivat Pohjois-Suomen 1986 syntymäkohortin jäseniä. Tutkittavat olivat 20–25 vuoden iässä. Lepotilan toiminnallinen magneettikuvaus suoritettiin 1.5 Teslan Siemensin magneettikuvantamislaitteella. Tutkimuskohteiksi valittiin lepotilan toiminnallinen aivohermoverkko, toiminnan ohjauksesta vastaava aivohermoverkko ja pikkuaivot. Kuvantamisdataan sovellettiin itsenäisten komponenttien analyysia aivohermoverkkojen määrittämistä varten. Ryhmien välisen eron havaitsemiseen käytettiin ei-parametristä permutaatiotestiä, joka kynnystettiin tilastollisesti merkitsevään tasoon (p &lt; 0.05). Lepotilan oletushermoverkossa ja toiminnanohjauksesta vastaavassa aivohermoverkoissa havaittiin vähäisempää aktiivisuutta ja pikkuaivoissa kohonnutta aktiivisuutta perinnöllisessä psykoosiriskissä olevilla nuorilla aikuisilla verrattuna verrokkeihin. Tutkimustulokset selkeyttivät aiempaa ristiriitaista kirjallisuutta tutkimusaiheesta. Tutkimuksessa havaittujen aivoalueiden poikkeava toiminta lepotilassa voi liittyä kohonneeseen psykoosin puhkeamisriskiin. Tutkimuslöydösten avulla voidaan todennäköisesti edesauttaa parempien kuvantamismenetelmien kehittämistä suurimmassa psykoosiriskissä olevien nuorten tunnistamiseen.