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.

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The anterior cingulate has been implicated in a number of cognitive processes that are at risk following traumatic brain injury (TBI), such as executive function and emotional processing. While the cingulate is believed to play a role in the above-mentioned cognitive processes, the relative roles of gray and white matter in functional outcomes post-TBI are not fully understood. The current study investigated various quantifiable brain properties (e.g., cortical thickness and volume, volume of underlying white matter, and white matter integrity) of the caudal anterior cingulate (CAC) gyrus and their relationships with behavioral measures of cognitive control following pediatric TBI. Parent ratings at three months post-injury indicated that TBI children demonstrated greater difficulty inhibiting inappropriate behavior and effectively transitioning between tasks. Reductions of CAC white matter integrity were observed in TBI participants, in the absence of significant morphometric group differences in this region. Neither CAC morphometrics nor fractional anisotropy (FA) were associated with experimental measures of cognitive control. The current findings indicate that DTI metrics may be more sensitive to brain changes in the region of the CAC following TBI. While strong relationships were not observed between CAC properties and measures of cognitive control, it is possible that study limitations may have obscured potential findings.

Att utvärdera samband mellan subjektivt skattad smärta och transmittorsubstanser med magnetresonansspektroskopi Bakgrund: Smärta är en komplex upplevelse, som involverar olika delar av hjärnan. Regionen anterior cingulate cortex (ACC) är kopplad till upplevelsen av smärta och delas in i ett flertal mindre regioner, till exempel den pregenuala regionen (pgACC) och dorsala regionen (dACC). För att studera olika metaboliter och transmittorsubstanser kan magnetresonansspektroskopi (MRS) användas. MRS och sekvensen MEGA-PRESS kan mäta specifika transmittorsubstanser såsom Gamma-AminoButyric Acid (GABA) och glutamin-glutamat (Glx).  Motiv: Det finns kunskapsluckor kring hur individens subjektiva smärtupplevelse i relation till transmittorsubstanser objektivt kan mätas och utvärderas.  Syfte: Att med MRS och MEGA-PRESS undersöka GABA+ och Glx-nivåer i hjärnområdena pgACC och dACC samt undersöka samband mellan smärtkänslighet och GABA+ och Glx i pgACC och dACC.  Metod: En kvantitativ, experimentell pilotstudie genomfördes med tio friska deltagare. Initialt skannades deltagarna i MRT och smärtstimulerades, sedan skattade de den upplevda smärtan med hjälp av Numeric Rating Scale. MRS och tekniken MEGA-PRESS användes för att mäta transmittorsubstansnivåerna.   Resultat: Studien visade att det fanns en statistiskt signifikant negativ korrelation mellan skattad smärtintensitet och uppmätta nivåer av GABA+ i pgACC (Spearman´s rho = -0,67; p = 0,04). Det fanns även ett statistiskt signifikant positivt samband mellan skattad smärtintensitet och uppmätta nivåer av Glx i dACC (Spearman´s rho =0,73; p=0,02). Vidare fanns signifikant skillnad i Glx mellan pgACC och dACC och en icke signifikant skillnad i GABA+.  Konklusion: Sammanfattningsvis visar resultatet att MRS och MEGA-PRESS kan kvantifiera transmittorsubstanser vid utvärdering av smärtkänslighet och att det finns en positiv korrelation mellan Glx och skattad smärtintensitet, samt en negativ korrelation mellan GABA+ och skattad smärtintensitet. Detta kan ge fördjupad insikt i individens smärtupplevelse och kan främja den individuella behandlingen. Genom att ta hänsyn till sambandet mellan smärta och transmittorsubstanser kan det bidra till ökad förståelse kring individens smärtupplevelse. / To evaluate the relation between subjectively estimated pain and neurotransmitters using magnetic resonance spectroscopy  Background: Pain is a complex experience that involves different parts of the brain. The region anterior cingulate cortex (ACC) is connected to the experience of pain and can be divided into several smaller areas, such as the pregenual region (pgACC) and the dorsal region (dACC). To study different metabolites and neurotransmitters, magnetic resonance spectroscopy (MRS) can be used. MRS and the sequence (MEGA-PRESS) can measure specific neurotransmitters such as Gamma-AminoButyric Acid (GABA) and glutamin-glutamate (Glx).  Motive: There are knowledge gaps about how the individual's subjective pain experience in relation to neurotransmitters can be objectively measured and evaluated.  Aim: Using MRS and MEGA-PRESS to examine levels of GABA+ and Glx in the brain regions pgACC and dACC and to examine the relationship between pain sensitivity and GABA+ and Glx in pgACC and dACC.  Methods: A quantitative, experimental pilot study was conducted which included ten healthy participants. The participants were initially scanned in the MRI and subjected to pain-stimulation, thereafter the participants rated the perceived pain using Numeric Rating Scale. MRS and the sequence MEGA-PRESS were used to quantify the neurotransmitters of interest.  Result: There was a significant, negative correlation between rated pain intensity and measured GABA+ levels in pgACC (Spearman´s rho = -0,67; p = 0,04). There was also a significant, positive correlation between rated pain intensity and measured levels of Glx in dACC (Spearman´s rho =0,73; p=0,02). Furthermore, there was a significant difference in Glx between pgACC and dACC as well as a non-significant difference in GABA+ between regions.  Conclusion: In summary, the result shows that MRS and MEGA-PRESS can quantify neurotransmitters when evaluating pain sensitivity and that there is a positive correlation between Glx and estimated pain intensity, and also a negative correlation between GABA+ and estimated pain intensity. This can provide a deeper insight into the individual’s pain experience and promote individual treatment. Further research regarding the meaning of the different brain regions when measuring neurotransmitters is recommended.

The lateral prefrontal cortex (LPFC) and the anterior cingulate cortex (ACC) are two key regions of the frontal executive control network. Ascending cholinergic pathways differentially innervate these two functionally distinct cortices to modulate arousal and motivational signaling for higher-order functions. The action of acetylcholine (ACh) in sensory cortices is constrained by layer, anatomical cell type, and subcellular localization of distinct receptors, but little is known about the nature and organization of frontal-cholinergic circuitry in primates. In this dissertation, we characterized the anatomical localization of muscarinic acetylcholine receptors (mAChRs), m1 and m2–the predominant subtypes in the cortex–and their expression profiles on distinct cell types and pathways in ACC and LPFC of the rhesus monkey, using immunohistochemistry, anatomical tract-tracing, whole cell patch-clamp recordings, and single nucleus RNA sequencing. In the first series of studies (Chapter 2), we used immunohistochemistry and high-resolution confocal microscopy to reveal regional differences in m1 and m2 receptor localization on excitatory pyramidal and inhibitory neuron subpopulations and subcellular compartments in ACC (A24) versus LPFC (A46) of adult rhesus monkeys (Macaca mulatta; aged 7-11 yrs; 4 males and 2 females). The ACC exhibited a greater proportion of m2+ inhibitory neurons and a greater density of presynaptic m2+ receptors localized on inhibitory (VGAT+) terminations on pyramidal neurons compared to the LPFC. This result suggests a greater cholinergic suppression of GABAergic neurotransmission in ACC. In a second set of experiments (Chapter 3), we examined the heterogeneity of m1 and m2 laminar expression in functionally distinct ACC areas A24, A25, and A32. These differ in their connections with higher order cortical areas and limbic structures, such as the amygdala (AMY). The density of m1+ and/or m2 expressing (m1+/m2+) pyramidal neurons was significantly greater in A24 compared to A25 and to A32, while A25 exhibited a significantly greater density of m2+VGAT+ terminals. In addition, we examined the substrates for cholinergic modulation of long-range cortico-limbic processing using bidirectional neural tracers to label one specific subtype, the AMY-targeting projection neurons in these ACC areas. Compared to A24 and A32, the limbic ventral A25 had a greater density of m1+/m2+ AMY-targeting pyramidal neurons across upper layers 2-3 and deep layers 5-6, suggesting stronger cholinergic modulation of amygdalar outputs. Lastly (Chapter 4), we assessed the functional effects of cholinergic modulation on excitatory and inhibitory synaptic activity as well as the molecular signatures related to m1 and m2 receptor expression. In experiments using in vitro whole-cell patch-clamp recordings of layer 3 pyramidal neurons in ACC and LPFC, we found that application of the cholinergic agonist carbachol (CCh) significantly decreased the frequency of excitatory postsynaptic currents (EPSCs) to a greater extent in ACC A24 than in LPFC A46. Using single nucleus RNA sequencing, we found that enriched m1 and m2 transcriptional profiles in distinct cell-types and frontal areas (ACC A24 and LPFC A46) had differentially expressed genes associated with down-stream signaling cascades related to synaptic signaling and plasticity. Together, these data reveal the anatomical, functional, and transcriptomic neural substrates of diverse cholinergic modulation of local excitatory and inhibitory circuits and long-range cortico-limbic pathways in functionally-distinct ACC and LPFC frontal areas that are important for cognitive-emotional integration.

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No description available.

京都大学 / 新制・課程博士 / 博士(医学) / 甲第24088号 / 医博第4864号 / 新制||医||1059(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 林 康紀, 教授 渡邉 大, 教授 髙橋 良輔 / 学位規則第4条第1項該当 / Doctor of Medical Science / Kyoto University / DFAM

<p>Conversational code-switching is common among bilingual speakers, in fact, we consider this routine; however, the reasons for switching and the location of this mechanism in the brain remain largely unknown. There is much to be discovered about bilingual code-switching especially in relation to autobiographical memories shared between immigrants. This study investigates the two phenomena: code-switching and autobiographical memories. The research is based on the following major theories: 1) Schrauf (2009) who said that one’s “…particular personal memories are associated with one or the other of the bilingual’s languages” (p. 26), which he called the language-specificity effect; 2) Marian & Neisser (2000) who proposed that “…memories become more accessible when language at retrieval matches language at encoding…any increase in the similarity between the linguistic environments at encoding and at retrieval should facilitate recall” (p. 361); 3) Marian & Kaushanskaya (2005), who found that “…bilinguals are more likely to code-switch to the other language when the language of encoding does not match the language of retrieval” (p. 1483). The results of this study both supported and disproved the above mentioned research, which indicate that language alone may not be the only influence on autobiographical memory recall or code-switching in elderly bilinguals. It is my belief that both phenomena stem from a higher process that is involved with cognitive control and located in the cingulate gyrus, one part of the limbic system.</p> / Master of Science (MSc)