Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1993. / Vita. Abstract. Includes bibliographical references (leaves 89-106). Also available via the Internet.

In the theory of the Behavioral Inhibition System (BIS), Gray and McNaughton (2000) classified events that produce or inhibit goal-directed behaviour into two affective categories: approach versus avoidance. We experience goal-conflict when approximately equal but incompatible approach and avoidance tendencies are concurrently activated. Gray and McNaughton (2000) proposed goal-conflict as a class of mechanisms separable from "simple" mechanisms: Goal-conflict effects are maximal when incompatible approach and avoidance tendencies are balanced, simple effects are maximal when either approach or avoidance tendencies predominate. Gray and McNaughton (2000) saw the hippocampus as a key nexus for resolving goal conflict by recursive amplification of the subjective value of punishment, thereby increasing avoidance tendencies. Rodent hippocampal theta (4-12 Hz) is necessary (but not sufficient) for correct and efficient transmission of hipppocampal outputs. The BIS theory is fundamentally an animal model. It is not clear if a human BIS exists in the same form. Record human hippocampal (4-12 Hz) activity from the scalp is unlikely. However, during goal-conflict resolution, cortically generated theta recorded from the scalp could be modulated by human hippocampal theta. Therefore, superficially recorded 4-12 Hz theta spectra power was used to assess if specific goal-conflict processing activity could be detected in humans. Human goal-conflict processing was assessed in four experiments: the Stop-Signal Task (SST), an existing experimental task, and three variations of a task termed "Choice", created for this thesis. Across experiments, three key conditions were created. Approach and avoidance were balanced in the intermediate condition (maximal goal-conflict). Net approach and avoidance predominated in the adjacent conditions respectively (minimal goal-conflict). Goal-conflict was assessed as the difference between activity in the intermediate condition and the average activity across the adjacent conditions (via extraction of the orthogonal quadratic trend for significance testing). Goal-conflict increased activations consistently at F8, above the right frontal cortex. Increase in task dependent goal-conflict activations were also observed at F7, Fz and F4 above the frontal cortex, and T3, T4, T5 and T6 above the temporal cortex. Activations within the human theta frequency range (4-7 Hz) were consistently detected in the Choice tasks. In the SST, activations spanned the conventional human theta (4-7 Hz) and alpha (8-12 Hz) frequencies. In the Choice tasks, higher conflict theta at T3, T5 and F8 predicted increased avoidance. Taken together, the findings support Gray and McNaugthon�s (2000) views that a) goal-conflict is a class of mechanism separable from simple approach and avoidance; b) goal-conflict processing recruits and increases cortical rhythmic activity within the same frequency range as rodent hippocampal theta (4-12 Hz); and goal-conflict is resolved by increasing the subjective value of punishment, thereby increasing avoidance tendencies. Although speculative, the current work identified a right inferior frontal gyrus neural circuit for slower, and a presupplementary motor area circuit for faster behavioral inhibition during goal-conflict resolution. These circuits are not explicit in the current BIS model.

Anxiety disorder is prevalent and costly. But its diagnosis is underdeveloped and treatment ad hoc. This could be corrected if the neural mechanisms of anxiety were known. All anxiolytic medications produce a decrease in rodent hippocampal theta rhythm - so hippocampal theta could underlie some types of anxiety. But, a review (Chapter 2) showed that ethanol and other anxiolytics increase FM-theta in the human scalp EEG and have other properties unlike hippocampal theta. The experiments in this thesis, therefore, tested for other potential homologues (Chapter 3) of hippocampal theta in the human EEG. The phase of hippocampal theta activity is reset in a working memory task and not an equivalent reference memory task in rats. Furthermore, low doses ethanol increases and high dose ethanol (and other anxiolytics) decrease theta activity. So, EEG was recorded from 15 scalp sites while participants performed non-verbal working memory and reference memory tasks before and after ethanol administration and assessed for the presence of phase-reset and ethanol-related changes in 5-7Hz and 8-11Hz spectral power (chapter 4 and 5). There was little general evidence for stimulus-induced phase-resetting of the ongoing EEG activity (Chapter 6). Increased post-stimulus synchronization in the theta frequency range was accompanied by increases in post-stimulus spectral power - suggesting that the synchronised activity was evoked rather than reset. Across 3 experiments (Chapter 7), low dose ethanol (54.5-146.6[mu]g/l) increased 5-7Hz theta, while the highest dose (307[mu]g/l) reduced task-related-increases in 5-7Hz activity. These effects were noted across electrode locations including frontal-midline sites and particularly at the beginning of the delay period. The suppression of 5-7Hz activity also coincided with an impairment in working memory performance. The dose-response curve for 5-7Hz theta was as predicted from rat hippocampal work. This particular component, linked to high working memory load or task difficulty, is a potential of homologue hippocampal theta. A clear decrease in theta with high dose ethanol, of this type, has not been reported previously. Activity in the 8-11Hz range typically increased with all doses of ethanol. It is clearly not a homologue of hippocampal theta. This is consistent with previous reports of increased alpha with high doses of ethanol - although these have been accompanied by increased, not decreased, theta. There is a potential homologue of hippocampal theta that can be detected in the human EEG (chapter 8); but the observed changes in 5-7Hz activity cannot be localised and may not be related to the hippocampus. It is clear there is more than one type of theta within the human EEG - with opposing sensitivities to ethanol. Critically, these types were detected at a single site and apparently in phase with one another. The current data, together with the previous literature, suggest that theta can be generated concurrently in distinct networks that, under specific task demands, can become coherent and so produce synchonised activity. Future studies need to test higher doses of ethanol and other anxiolytics and use different experimental paradigms to further differentiate the theta systems in the human EEG. Human EEG could be useful for differentiating sub-types of anxiety, and the choice and effectiveness of interventions delivered.

In the theory of the Behavioral Inhibition System (BIS), Gray and McNaughton (2000) classified events that produce or inhibit goal-directed behaviour into two affective categories: approach versus avoidance. We experience goal-conflict when approximately equal but incompatible approach and avoidance tendencies are concurrently activated. Gray and McNaughton (2000) proposed goal-conflict as a class of mechanisms separable from "simple" mechanisms: Goal-conflict effects are maximal when incompatible approach and avoidance tendencies are balanced, simple effects are maximal when either approach or avoidance tendencies predominate. Gray and McNaughton (2000) saw the hippocampus as a key nexus for resolving goal conflict by recursive amplification of the subjective value of punishment, thereby increasing avoidance tendencies. Rodent hippocampal theta (4-12 Hz) is necessary (but not sufficient) for correct and efficient transmission of hipppocampal outputs. The BIS theory is fundamentally an animal model. It is not clear if a human BIS exists in the same form. Record human hippocampal (4-12 Hz) activity from the scalp is unlikely. However, during goal-conflict resolution, cortically generated theta recorded from the scalp could be modulated by human hippocampal theta. Therefore, superficially recorded 4-12 Hz theta spectra power was used to assess if specific goal-conflict processing activity could be detected in humans. Human goal-conflict processing was assessed in four experiments: the Stop-Signal Task (SST), an existing experimental task, and three variations of a task termed "Choice", created for this thesis. Across experiments, three key conditions were created. Approach and avoidance were balanced in the intermediate condition (maximal goal-conflict). Net approach and avoidance predominated in the adjacent conditions respectively (minimal goal-conflict). Goal-conflict was assessed as the difference between activity in the intermediate condition and the average activity across the adjacent conditions (via extraction of the orthogonal quadratic trend for significance testing). Goal-conflict increased activations consistently at F8, above the right frontal cortex. Increase in task dependent goal-conflict activations were also observed at F7, Fz and F4 above the frontal cortex, and T3, T4, T5 and T6 above the temporal cortex. Activations within the human theta frequency range (4-7 Hz) were consistently detected in the Choice tasks. In the SST, activations spanned the conventional human theta (4-7 Hz) and alpha (8-12 Hz) frequencies. In the Choice tasks, higher conflict theta at T3, T5 and F8 predicted increased avoidance. Taken together, the findings support Gray and McNaugthon�s (2000) views that a) goal-conflict is a class of mechanism separable from simple approach and avoidance; b) goal-conflict processing recruits and increases cortical rhythmic activity within the same frequency range as rodent hippocampal theta (4-12 Hz); and goal-conflict is resolved by increasing the subjective value of punishment, thereby increasing avoidance tendencies. Although speculative, the current work identified a right inferior frontal gyrus neural circuit for slower, and a presupplementary motor area circuit for faster behavioral inhibition during goal-conflict resolution. These circuits are not explicit in the current BIS model.

The purpose of this thesis was to investigate a proposed neurophysiological model for Necker cube reversals by using electroencephalography. It is suggested that Necker cube reversals are mediated by sustained focused attention to the overall drawing with visual selective attention to vertices of the cube. The main hypotheses were that deliberate attention would increase Necker cube reversals over passive attention, there would be greater high theta power during the deliberate focusing of attention than during passive attentional processing, and there would be greater theta power in the right hemisphere. Thirty undergraduate psychology students had monopolar EEG recorded bilaterally from frontal and parietal electrode sites. The subjects viewed computer presentations of the Necker cube under two different experimental conditions: a passive condition in which they were not instructed to influence reversals, and an active condition in which subjects deliberately shifted their focus of attention. / Master of Science

Introduction: The present study aims to understand how the absence of food security and breastfeeding in children at one year of age, which can be considered as adverse childhood experiences, may be associated with brain function as measured by the relative and absolute power spectral density of four frequency bands of brain waves (theta, alpha, beta, and gamma) among a sample of infants from low-socioeconomic (SES) backgrounds at age 12 months old. Methods: A cross-sectional survey was used by the parent study, Baby’s First Years (BFY), to collect quantitative data to understand the associations between breastfeeding, food insecurity, and brain function in a sample of 243 low-SES mothers and their infants at age 12 months old. Breastfeeding was measured as ever breastfed, to understand if a mother had ever initiated breastfeeding of their infant, and breastfeeding duration, measured in months. Household food insecurity (HFI) was measured using the U.S. Household Food Security Survey Module Short Form devised by the USDA. Electroencephalography (EEG) data was collected to assess brain function. Data Analysis: Data was analyzed to determine associations between being ever breastfed, breastfeeding duration, and the presence of HFI and EEG measured relative and absolute theta, alpha, beta, and gamma power in infants at 12 months of age using multiple linear regression (MLR) models based on ordinary least squares (OLS). Results: 77% (n=187) of mothers reported breastfeeding their child at least one time. The mean breastfeeding duration (including the mothers that never breastfed) was 3.6 months (SD=4.12). 27.6% (n=67) of mothers were found to be food insecure. Ever breastfeeding an infant during the first year of life was found to be associated with higher absolute theta power (p<0.05), and higher relative and absolute alpha power (p<0.01). Breastfeeding duration was not found to be associated with relative and absolute theta, alpha, beta or gamma power. Finally, the presence of food insecurity was not found to be associated with relative and absolute theta, alpha, beta or gamma power. Discussion: Differences in brain function may be adaptive for children experiencing adversity because of their lower SES, amongst other factors (Ellis et al., 2020). Ever breastfeeding an infant was associated with higher absolute theta power, which was an unexpected finding. However, relative theta power was not associated with ever breastfeeding, and therefore this finding must cautiously be interpreted. Ever breastfeeding an infant was associated with higher relative and absolute alpha power. It is possible that the increases in relative and absolute alpha power within the sample of infants who were ever breastfed are in part due to the emotional connection that breastfeeding elicits and the characteristics of mothers that decide to initiate breastfeeding as compared to those that do not initiate breastfeeding. This research demonstrates significant associations between ever breastfeeding an infant with brain function in a population of infants from diverse, low SES backgrounds. In contextualizing these changes in brain function as plausible adaptations that infants are developing due to their experiences, an opportunity exists to further explore these associations with brain function to understand the skills that low SES infants are developing during the first year of life.

No description available.

Οι in vivo θ και γ ρυθμοί στον ιππόκαμπο συνυπάρχουν και θεωρείται ότι συμμετέχουν στην διαδικασία δημιουργίας και ανάκλησης των μνημονικών αναπαραστάσεων. Σε τομές ιπποκάμπου in vitro, βρήκαμε όμως ότι διαφοροποιείται η ικανότητα επαγωγής αυτών των ρυθμών στο κοιλιακό σε σχέση με το ραχιαίο άκρο του. Συγκεκριμένα, η καρβαχόλη σε συγκεντρώσεις 5-50μΜ προκάλεσε την εμφάνιση κυρίως γ ρυθμού στις κοιλιακές τομές (35/38 τομές), ενώ οι ραχιαίες τομές είτε έμειναν ρυθμικά σιωπηλές (26/48 τομές) είτε εμφάνισαν θ ρυθμική δραστηριότητα (17/48 τομές) ενώ γ δραστηριότητα εμφάνισαν σπάνια (9/48 τομές) και μόνο σε συγκεντρώσεις > 20 μΜ καρβαχόλης. Τα δεδομένα αυτά δείχνουν ότι οι τομές από κοιλιακό ιππόκαμπο συγκριτικά με αυτές από τον ραχιαίο παράγουν γ ρυθμό, πολύ πιο εύκολα, (με μικρότερη συγκέντρωση αγωνιστή) και με μεγαλύτερη συνέπεια. Αντίθετα οι ραχιαίες τομές οργανώνονται σε ρυθμική δραστηριότητα δυσκολότερα από τις κοιλιακές κι όταν το κάνουν, προτιμούν ρυθμική δραστηριότητα μικρότερης συχνότητας θ ή δ. Επίσης, δείχνουν ότι ο θ-ρυθμός δεν είναι γενικά η προτιμώμενη δραστηριότητα του ιπποκάμπου in vitro αλλά ότι η προτίμηση σε μια ρυθμική δραστηριότητα εξαρτάται από το μέρος του επιμήκη άξονα του ιπποκάμπου στο οποίο αναφερόμαστε. Η ισχύς των ρυθμικών ταλαντώσεων που οργανώθηκαν μετά τη χορήγηση καρβαχόλης στις κοιλιακές τομές, συσχετίζονταν με το βαθμό ανάπτυξης της αυθόρμητης δραστηριότητας από οξέα κύματα (SPWs) στις τομές αυτές και ήταν ανάλογη. Επιπλέον, τα δεδομένα μας δείχνουν ότι οι κοιλιακές τομές είναι ρυθμογενητικά ικανότερες συγκριτικά με τις ραχιαίες αφού η πλειοψηφία τους εμφάνισε τουλάχιστον μία ρυθμική δραστηριότητα (γ, 34/38 τομές) ενώ 17/34 τομές οργάνωσαν ταυτόχρονα διαφορετικές ρυθμικές ταλαντώσεις σε συχνότητες δ, θ ή/και β. Οι ταλαντώσεις αυτές ήταν παροδικές, ακολουθούσαν ένα ορισμένο χρονικό πρότυπο εμφάνισης και η εμφάνισή τους ήταν συσχετισμένη: η μία αποτελούσε μεταβατικό στάδιο στην εμφάνιση της επόμενης. Επειδή όλες οι ρυθμικές δραστηριότητες που οργανώθηκαν στις κοιλιακές τομές εκτός της γ, δεν συνυπήρχαν μεταξύ τους και η εμφάνισή τους ήταν εξαρτημένη, ενώ αντίθετα η γ δραστηριότητα μπορούσε να συνυπάρχει ταυτόχρονα με κάποια από αυτές, θεωρούμε ότι στις κοιλιακές τομές υπάρχουν τουλάχιστον δύο ανεξάρτητοι ταλαντωτές: ένας που παράγει ρυθμική δραστηριότητα γ και ακόμα ένας τουλάχιστον που παράγει τις άλλες δραστηριότητες. / Theta and gamma rhythms coexist and are believed they participate in the formation and recall of mnemonic representations. In hippocampal slices in vitro we found different ability of carbachol to induce rhythmic activity in slices from the ventral compared to the dorsal part. Carbachol in concentrations from 5 to 50μM induced mainly gamma oscillations in ventral slices (35/38) and no oscillations (26/48) or theta oscillations in dorsal slices (17/48). Gamma oscillations in dorsal slices where induced only in concentrations grater than 20μM Carbachol and in only 9/48 slices. These data show that ventral slices organize robust gamma oscillations much easier (at a smaller agonist concentration) and with a greater incidence. In contrast dorsal slices organize more rarely oscillatory activity and when they manage to they prefer activity of a lower frequency (at theta or delta band). Our data show that theta activity is not the preferred activity of hippocampus but its preference in a certain rhythmic activity depends on the part of its longitudinal axis that we refer to. The power of oscillations in ventral hippocampus was reciprocally correlated to the degree of spontaneously organized sharp wave activity under control conditions. Ventral slices are capable of organizing a variety of oscillatory activities: they mainly organize gamma oscillations (34/38 slices), but 17/34 slices produced oscillations in delta, theta and/or beta bands. These later oscillations were transient and correlated and followed a specific temporal pattern of appearance. Because all rhythmic activities encountered in ventral slices except for gamma oscillations, were dependent but not coinciding and gamma oscillations were independent from the later but could also coincide with them, we propose that in ventral slices there exist at least two independent oscillators: one capable of producing gamma activity and at least one more capable of producing the remaining ones.

京都大学 / 新制・課程博士 / 博士(人間健康科学) / 甲第23128号 / 人健博第90号 / 新制||人健||6(附属図書館) / 京都大学大学院医学研究科人間健康科学系専攻 / (主査)教授 稲富 宏之, 教授 精山 明敏, 教授 村井 俊哉 / 学位規則第4条第1項該当 / Doctor of Human Health Sciences / Kyoto University / DFAM

Les mécanismes cellulaires et moléculaires qui sous-tendent la mémoire et l’apprentissage chez les mammifères sont incomplètement compris. Le rythme thêta de l’hippocampe constitue l’état « en ligne » de cette structure qui est cruciale pour la mémoire déclarative. Dans la région CA1 de l’hippocampe, les interneurones inhibiteurs LM/RAD démontrent des oscillations de potentiel membranaire (OPM) intrinsèques qui pourraient se révéler importantes pour la génération du rythme thêta. Des travaux préliminaires ont suggéré que le courant K+ I(A) pourrait être impliqué dans la génération de ces oscillations. Néanmoins, peu de choses sont connues au sujet de l’identité des sous-unités protéiques principales et auxiliaires qui soutiennent le courant I(A) ainsi que l’ampleur de la contribution fonctionnelle de ce courant K+ dans les interneurones. Ainsi, cette thèse de doctorat démontre que le courant I(A) soutient la génération des OPM dans les interneurones LM/RAD et que des protéines Kv4.3 forment des canaux qui contribuent à ce courant. De plus, elle approfondit les connaissances sur les mécanismes qui régissent les interactions entre les sous-unités principales de canaux Kv4.3 et les protéines accessoires KChIP1. Finalement, elle révèle que la protéine KChIP1 module le courant I(A)-Kv4.3 natif et la fréquence de décharge des potentiels d’action dans les interneurones. Nos travaux contribuent à l’avancement des connaissances dans le domaine de la modulation de l’excitabilité des interneurones inhibiteurs de l’hippocampe et permettent ainsi de mieux saisir les mécanismes qui soutiennent la fonction de l’hippocampe et possiblement la mémoire chez les mammifères. / Cellular and molecular mechanisms underlying learning and memory in mammals are incompletely understood. The theta rhythm in the hippocampus constitutes the « on-line » state of this structure which is crucial for declarative memory. In the CA1 hippocampal area, LM/RAD inhibitory interneurons exhibit intrinsic membrane potential oscillations (MPOs) that could be important for the generation of theta rhythm. Preliminary work suggested that K+ current I(A) could be involved in the generation of these oscillations. Nevertheless, little is known about the identity of the principal and auxiliary protein subunits underlying I(A) current and the extent of the functional contribution of this K+ current in hippocampal interneurons. Thus, this Ph.D. thesis shows that I(A) current underlies MPO generation in LM/RAD interneurons and that Kv4.3 proteins form channels that contribute to this current. Also, it deepens the knowledge on the mechanism controlling the interactions between Kv4.3 channel-forming principal subunits and KChIP1 auxiliary proteins. Finally, it reveals that KChIP1 modulates native I(A)-Kv4.3 current and the action potential discharge frequency in interneurons. Our work takes part in advancing the knowledge on the field of modulation of excitability in hippocampal inhibitory interneurons and allows a better understanding of the mechanisms underlying the function of the hippocampus and possibly memory in mammals.