1,855 research outputs found

    Inferring human intentions from the brain data

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    Progress toward an understanding of cortical computation

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    The additional data, perspectives, questions, and criticisms contributed by the commentaries strengthen our view that local cortical processors coordinate their activity with the context in which it occurs using contextual fields and synchronized population codes. We therefore predict that whereas the specialization of function has been the keynote of this century the coordination of function will be the keynote of the next

    Cholinergic modulation of auditory and prefrontal cortical interactions

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    Much of the previous work investigating the influence of cholinergic tone on cortical circuits has emphasized global states of arousal and local circuit dynamics; however the cholinergic system is well-suited to coordinate large-scale cortical interactions due to its diffuse cortically projecting arborization and diverse influence on the various cell types within the cortical microcircuit. In this thesis I examined the function of cortical cholinergic tone in supporting long-range cortical interactions, feed-forward sensory signaling, and active processing of behaviorally relevant stimuli. I utilized optogenetic stimulation and silencing of the cholinergic nucleus basalis while recording from the auditory-prefrontal cortical circuit as well as performing local drug infusions in awake mice. I demonstrate that prefrontal cortex actively responds to cortico-cortical sensory input in animals passively presented with acoustic stimuli and that muscarinic receptor binding within auditory cortex is essential for feedforward pathways from auditory cortex to transmit sensory related neural signals. Specifically, muscarinic antagonists applied to the auditory cortex disrupt sensory signaling within auditory cortex as well as bottom up signaling to prefrontal cortex. Furthermore, muscarinic antagonists attenuated the influence of cortical cholinergic release on recording channels closest to drug infusion, confirming the efficacy of muscarinic antagonism, and demonstrating that aspects of cholinergic modulation are locally generated within cortical circuits, while others are globally generated in large networks. In task performing animals, I observed that optogenetic silencing of cholinergic nucleus basalis neurons attenuates the magnitude of prefrontal cortex alpha power following correct behavioral choice and that alpha in prefrontal and auditory cortical local field potentials are actively involved in behavioral learning during extinction, suggesting that cholinergic tone is involved in maintaining and updating the value of stimuli across behavioral trials. In summary, my thesis supports a model where endogenous cholinergic signaling is an essential component of normal auditory processing during low attentive states, contributes to circuit activation through local and large network mechanisms, and supports essential cortical dynamics that contribute to active behavioral processing of stimuli

    ERP Markers of Auditory Go/NoGo Processing

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    The Sequential Processing Schema is a data-driven model that uses event-related potential (ERP) components to chart the important psychophysiological processes activated when completing auditory equiprobable Go/NoGo tasks. This model is useful for measuring experimental effects on basic cognitive processes and provides a valuable framework to synthesise and test ERP component theories. Determining the cognitive and behavioural correlates of ERP components is critical for understanding their functional significance and utility in psychology. Additional research is also needed to refine the conceptualisation of the ERP components and cognitive processing requirements in equiprobable Go/NoGo tasks, which are commonly used in psychophysiological research. To do that, robust data-driven methods such as temporal Principal Components Analysis (PCA) are needed for effective ERP component quantification and analyses of the Go/NoGo ERP component ‘processing’ series. This doctoral thesis aimed to clarify ERP component functionality and refine our understanding of equiprobable Go/NoGo tasks by developing the Sequential Processing Schema and exploring how ERP/PCA components relate to cognitive and behavioural processing under different Go/NoGo task conditions. Study 1 compared the ERP component processing series associated with auditory equiprobable and oddball variants of the Go/NoGo task. The manipulation of probability and the relevant modulation of the ERP component series reflected a shift in particular cognitive demands or task requirements, which promoted the conceptual development of component functionality and the generalisability of the Schema. The results of Study 1 questioned the identity of a core ERP component (i.e., Processing Negativity) previously linked to auditory Go/NoGo processing; this was pursued in detail in Study 2, which aimed to clarify the ERP components associated with early information processing in auditory equiprobable and ‘frequent Go’ variants of the Go/NoGo task. Stimulus probability differences (this time the inverse of Study 1) were again used to elucidate component functionality and provide insight into the cognitive task demands. Study 3 and 4 explored ERP component functionality by examining Go stimulus- and response-locked ERP averaging effects, and the link between the equiprobable NoGo P3a and motor response inhibition. Studies 1–4 provided insight into the sequential processing requirements in auditory equiprobable Go/NoGo tasks, and the associated ERP/PCA components, promoting the development of common ERP components as indices of cognitive processes. These outcomes clarified the utility of the equiprobable Go/NoGo task, and highlight important similarities and differences between Go/NoGo and oddball processing, encouraging ERP theory development and integration between those common research paradigms. An update to the Schema was proposed to accommodate the ERP findings and reflect the refined interpretation of equiprobable Go/NoGo processing developed in this thesis, including a shift in the conceptualisation of the sensory processing and inhibitory requirements in the equiprobable task. This was considered to improve the conceptual framework of the Schema and its utility for charting the cognitive and behavioural processing in different task conditions. The outcomes also provide novel insight into how healthy young adults process information and encourage further studies of sequential processing to help delineate abnormalities in cognitive processing related to different psychopathologie

    Therapeutic Induction of Altered States of Consciousness: Investigation of 1-20Hz Neurofeedback

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    Positive outcomes linked to experiences of altered states of consciousness (ASC) have been linked to various brain wave patterns, as well as both positive and negative personality traits and affective disorders. Various innovative neurofeedback (NFB) technologies are being developed in an attempt to create adjunctive therapeutic treatments. The current study investigated 1-20 Hz NFB to induce ASC and examine associations between NFB, ASC, mood changes, and trait predictors. 23 students completed trait measures of emotionality, openness and extroversion from the HEXACO test of personality and a measure of trait absorption. Participants then completed 15min of NFB. The Profile of Mood States (POMS) was administered before and after the NFB session and the Altered States of Consciousness Questionnaire (OAV) at the end of session. Elevated levels of trait emotionality and absorption were associated with the subscale of disembodiment on the OAV. POMS scores indicated significant reductions in vigor and a significant increase in fatigue and confusion from pre-to post NFB. An overall decrease in 1-20Hz was seen pre-vs post intervention globally, with an increase in 1-20Hz during the intervention as measured at the NFB training site. Positive correlations were seen between EEG and OAV scores for the subscale disembodiment, with global changes between time one and time five during the intervention. EEG readings taken at the active training site demonstrated a positive correlation with trait emotionality and with the subscale spirituality. Qualitative feedback indicated that 70% of participants reported a positive response to neurofeedback, with 17% reporting negative effects, including feeling tired; often associated with over training, 14% reported having no response. 1-20Hz evidenced potentially therapeutic effects and warrants further investigation

    Micro-, Meso- and Macro-Dynamics of the Brain

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    Neurosciences, Neurology, Psychiatr

    The Role of Unimodal and Transmodal Cortex in Perceptually-Coupled and Decoupled Semantic Cognition: Evidence from fMRI

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    Semantic retrieval extends beyond the here-and-now, to draw on abstract knowledge that has been extracted across multiple experiences; for instance, we can easily bring to mind what a dog looks and sounds like, even when a dog is not present in our environment. However, a clear understanding of the neural substrates that support patterns of semantic retrieval that are not immediately driven by stimuli in the environment is lacking. This thesis sought to investigate the neural basis of semantic retrieval within unimodal and heteromodal networks, whilst manipulating the availability of information in the environment. Much of the empirical work takes inspiration from modern accounts of transmodal regions (Lambon Ralph et al. 2017; Margulies et al. 2016), which suggest the anterior temporal lobe (ATL) and default mode network (DMN) support both abstraction and perceptual decoupling. The first empirical chapter examines whether words and experiences activate common neural substrates in sensory regions and where, within the ATLs, representations are transmodal. The second empirical chapter investigates how perceptually-decoupled forms of semantic retrieval in imagination are represented across unimodal and transmodal regions. The third empirical chapter interrogates whether transmodal regions respond in a similar manner to conceptually-guided and perceptually-decoupled cognition, and whether these two factors interact. The data suggests ventrolateral ATL processes both abstract modality-invariant semantic representations (Chapter 3) and decoupled semantic processing during imagination (Chapter 4). In addition, this thesis found comparable networks recruited for both conceptual processing and perceptually-decoupled retrieval corresponding to the broader DMN (Chapter 5). Further interrogation of these sites confirmed lateral MTG and bilateral angular gyrus were pivotal in the combination of conceptual retrieval from memory. Collectively, this data suggests that brain regions situated farthest from sensory input systems in both functional and connectivity space are required for the most abstract forms of cognition

    Investigating the dynamic role of fluctuations in ongoing activity in the human brain

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    Traditionally, the focus in cognitive neuroscience has been on so-called evoked neural activity in response to certain stimuli or experiences. However, most of the brain’s activity is actually spontaneous and therefore not ascribed to the processing of a certain task or stimulus – or in other words, uncoupled to overt stimuli or motor outputs. In this thesis I investigated the functional role of spontaneous activity with a focus on its role in contextual changes ranging from recent experiences of individuals to trial-by-trial variability in a certain task. I studied the nature of ongoing activity from two perspectives: One looking at changes in the ongoing activity due to learning, and the other one looking at the predictive role of prestimulus activity using different methodologies, i.e. EEG and fMRI. Finally, I ventured into the realm of inter-individual differences and mind-wandering to investigate the relationship between ongoing activity, certain behavioural traits and neuronal connectivity
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