Linking brain to mind in normal behavior and schizophrenia

In order to understand schizophrenia, a linking hypothesis is needed that shows how brain mechanisms lead to behavioral functions in normals, and also how breakdown in these mechanisms lead to behavioral symptoms in schizophrenia. Such a linking hypothesis is now available that complements the discussion offered by Phillips and Silverstein.

Linking Visual Development and Learning to Information Processing: Preattentive and Attentive Brain Dynamics

National Science Foundation (SBE-0354378); Office of Naval Research (N00014-95-1-0657)

Consciousness CLEARS the Mind

A full understanding of consciouness requires that we identify the brain processes from which conscious experiences emerge. What are these processes, and what is their utility in supporting successful adaptive behaviors? Adaptive Resonance Theory (ART) predicted a functional link between processes of Consciousness, Learning, Expectation, Attention, Resonance, and Synchrony (CLEARS), includes the prediction that "all conscious states are resonant states." This connection clarifies how brain dynamics enable a behaving individual to autonomously adapt in real time to a rapidly changing world. The present article reviews theoretical considerations that predicted these functional links, how they work, and some of the rapidly growing body of behavioral and brain data that have provided support for these predictions. The article also summarizes ART models that predict functional roles for identified cells in laminar thalamocortical circuits, including the six layered neocortical circuits and their interactions with specific primary and higher-order specific thalamic nuclei and nonspecific nuclei. These prediction include explanations of how slow perceptual learning can occur more frequently in superficial cortical layers. ART traces these properties to the existence of intracortical feedback loops, and to reset mechanisms whereby thalamocortical mismatches use circuits such as the one from specific thalamic nuclei to nonspecific thalamic nuclei and then to layer 4 of neocortical areas via layers 1-to-5-to-6-to-4.

Spikes, Synchrony, and Attentive Learning by Laminar Thalamocortical Circuits

This article develops the Synchronous Matching Adaptive Resonance Theory (SMART) neural model to explain how the brain may coordinate multiple levels of thalamocortical and corticocortical processing to rapidly learn, and stably remember, important information about a changing world. The model clarifies how bottom-up and top-down processes work together to realize this goal, notably how processes of learning, expectation, attention, resonance, and synchrony are coordinated. The model hereby clarifies, for the first time, how the following levels of brain organization coexist to realize cognitive processing properties that regulate fast learning and stable memory of brain representations: single cell properties, such as spiking dynamics, spike-timing-dependent plasticity (STDP), and acetylcholine modulation; detailed laminar thalamic and cortical circuit designs and their interactions; aggregate cell recordings, such as current-source densities and local field potentials; and single cell and large-scale inter-areal oscillations in the gamma and beta frequency domains. In particular, the model predicts how laminar circuits of multiple cortical areas interact with primary and higher-order specific thalamic nuclei and nonspecific thalamic nuclei to carry out attentive visual learning and information processing. The model simulates how synchronization of neuronal spiking occurs within and across brain regions, and triggers STDP. Matches between bottom-up adaptively filtered input patterns and learned top-down expectations cause gamma oscillations that support attention, resonance, and learning. Mismatches inhibit learning while causing beta oscillations during reset and hypothesis testing operations that are initiated in the deeper cortical layers. The generality of learned recognition codes is controlled by a vigilance process mediated by acetylcholine.

Brain Learning and Recognition: The Large and the Small of It in Inferotemporal Cortex

Anterior inferotemporal cortex (ITa) plays a key role in visual object recognition. Recognition is tolerant to object position, size, and view changes, yet recent neurophysiological data show ITa cells with high object selectivity often have low position tolerance, and vice versa. A neural model learns to simulate both this tradeoff and ITa responses to image morphs using large-scale and small-scale IT cells whose population properties may support invariant recognition.

From Stereograms to Surface: How the Brain Sees the World in Depth

When we look at a scene, how do we consciously see surfaces infused with lightness and color at the correct depths? Random Dot Stereograms (RDS) probe how binocular disparity between the two eyes can generate such conscious surface percepts. Dense RDS do so despite the fact that they include multiple false binocular matches. Sparse stereograms do so even across large contrast-free regions with no binocular matches. Stereograms that define occluding and occluded surfaces lead to surface percepts wherein partially occluded textured surfaces are completed behind occluding textured surfaces at a spatial scale much larger than that of the texture elements themselves. Earlier models suggest how the brain detects binocular disparity, but not how RDS generate conscious percepts of 3D surfaces. A neural model predicts how the layered circuits of visual cortex generate these 3D surface percepts using interactions between visual boundary and surface representations that obey complementary computational rules.

Distributed Hypothesis Testing, Attention Shifts and Transmitter Dynatmics During the Self-Organization of Brain Recognition Codes

BP (89-A-1204); Defense Advanced Research Projects Agency (90-0083); National Science Foundation (IRI-90-00530); Air Force Office of Scientific Research (90-0175, 90-0128); Army Research Office (DAAL-03-88-K0088)

A Recurrent Cooperative/Competitive Field for Segmentation of Magnetic Resonance Brain Imagery

The Grey-White Decision Network is introduced as an application of an on-center, off-surround recurrent cooperative/competitive network for segmentation of magnetic resonance imaging (MRI) brain images. The three layer dynamical system relaxes into a solution where each pixel is labeled as either grey matter, white matter, or "other" matter by considering raw input intensity, edge information, and neighbor interactions. This network is presented as an example of applying a recurrent cooperative/competitive field (RCCF) to a problem with multiple conflicting constraints. Simulations of the network and its phase plane analysis are presented.

Living long-term with acquired brain injury in Ireland: towards a counter discourse

Irish literature on Acquired Brain Injury (ABI) is very scant and is mainly deficits and/or needs based. The focus is generally on how to manage the short term needs of the younger population with ABI. The starting position of my thesis is that people living long-term with ABI are important participants in developing knowledge about this social phenomenon, living with ABI while accepting that their brain injury does not determine them. Six mature adults with ABI and their six significant others participated in this longitudinal study. Using a narrative approach in interviews, over twenty months, five repeat individual interviews with each of the twelve participants was held. From this I gained an understanding of their lived experiences, their life-world and their experiences of our local public ABI/disability services, systems and discourse. Along with this new empirical data, theoretical developments from occupational therapy, occupational science, sociology, and disability studies were also used within a meta-narrative informed by critical theory and critical realism to develop a synthesis of this study. Social analysis of their narratives co-constructed with me, allowed me generate nuanced insights into tendencies and social processes that impacted and continues to impact on their everyday-everynight living. I discuss in some depth here, the relational attitudinal, structural, occupational and environmental supports, barriers or discrimination that they face(d) in their search for social participation and community inclusion. Personal recognition of the disabled participants by their family, friends and/or local community, was generally enhanced after much suffering, social supports, slow recovery, and with some form of meaningful occupational engagement. This engagement was generally linked with pre-injury interests or habits, while Time itself became both a major aid and a need. The present local ABI discourse seldom includes advocacy and inclusion in everyday/every night local events, yet most participants sought both peer-support or collective recognition, and social/community inclusion to help develop their own counter-discourse to the dominant ABI discourse. This thesis aims to give a broad social explanation on aspects of their social becoming, 'self-sameness' and social participation, and the status of the disabled participants wanting to live 'the slow life'. Tensions and dialectical issues involved in moving from the category of a person in coma, to person with a disability, to being a citizen should not demote the need for special services. While individualized short-term neuro-rehabilitation is necessary, it is not sufficient. Along with the participants, this researcher asks that community health and/or social care planners and service-providers rethink how ABI is understood and represented, and how people with ABI are included in their local communities

Role of KLF4 in regulation of myocardin induced SMC differentiation in human smooth muscle stem progenitor cells (hSMSPC)

The differentiation of stem cells into multiple lineages has been explored in vascular regenerative medicine. However, in the case of smooth muscle cells (SMC), issues exist concerning inefficient rates of differentiation. In stem cells, multiple repressors potentially downregulate myocardin, the potent SRF coactivator induced SMC transcription including Krüppel like zinc finger transcription factor-4 (KLF4). This thesis aimed to explore the role of KLF4 in the regulation of myocardin gene expression in human smooth muscle stem/progenitor cells (hSMSPC), a novel circulating stem cell identified in our laboratory which expresses low levels of myocardin and higher levels of KLF4. hSMSPC cells cultured in SmGM2 1% FBS with TGF-β1 (5 ng/ml “differentiation media”) show limited SMC cell differentiation potential. Furthermore, myocardin transduced hSMSPC cells cultured in differentiation media induced myofilamentous SMC like cells with expression of SM markers. Five potential KLF4 binding sites were identified in silico within 3.9Kb upstream of the translational start site of the human myocardin promoter. Chromatin immunoprecipitation assays verified that endogenous KLF4 binds the human myocardin promoter at -3702bp with Respect to the translation start site (-1). Transduction of lentiviral vectors encoding either myocardin cDNA (LV_myocardin) or KLF4 targeting shRNA (LV_shKLF4 B) induced human myocardin promoter activity in hSMSPCs. Silencing of KLF4 expression in differentiation media induced smooth muscle like morphology by day 5 in culture and increased overtime with expression of SMC markers in hSMSPCs. Implantation of silastic tubes into the rat peritoneal cavity induces formation of a tissue capsule structure which may be used as vascular grafts. Rat SMSPCs integrate into, strengthen and enhance the SMC component of such tubular capsules. These data demonstrate that KLF4 directly represses myocardin gene expression in hSMSPCs, which when differentiated, provide a potential source of SMCs in the development of autologous vascular grafts in regenerative medicine.

P-glycoprotein inhibition as a strategy to increase drug delivery across the blood-brain barrier: focus on antidepressants

Depression is among the leading causes of disability worldwide. Currently available antidepressant drugs have unsatisfactory efficacy, with up to 60% of depressed patients failing to respond adequately to treatment. Emerging evidence has highlighted a potential role for the efflux transporter P-glycoprotein (P-gp), expressed at the blood-brain barrier (BBB), in the aetiology of treatment-resistant depression. In this thesis, the potential of P-gp inhibition as a strategy to enhance the brain distribution and pharmacodynamic effects of antidepressant drugs was investigated. Pharmacokinetic studies demonstrated that administration of the P-gp inhibitors verapamil or cyclosporin A (CsA) enhanced the BBB transport of the antidepressants imipramine and escitalopram in vivo. Furthermore, both imipramine and escitalopram were identified as transported substrates of human P-gp in vitro. Contrastingly, human P-gp exerted no effect on the transport of four other antidepressants (amitriptyline, duloxetine, fluoxetine and mirtazapine) in vitro. Pharmacodynamic studies revealed that pre-treatment with verapamil augmented the behavioural effects of escitalopram in the tail suspension test (TST) of antidepressant-like activity in mice. Moreover, pre-treatment with CsA exacerbated the behavioural manifestation of an escitalopram-induced mouse model of serotonin syndrome, a serious adverse reaction associated with serotonergic drugs. This finding highlights the potential for unwanted side-effects which may occur due to increasing brain levels of antidepressants by P-gp inhibition, although further studies are needed to fully elucidate the mechanism(s) at play. Taken together, the research outlined in this thesis indicates that P-gp may restrict brain concentrations of escitalopram and imipramine in patients. Moreover, we show that increasing the brain distribution of an antidepressant by P-gp inhibition can result in an augmentation of antidepressant-like activity in vivo. These findings raise the possibility that P-gp inhibition may represent a potentially beneficial strategy to augment antidepressant treatment in clinical practice. Further studies are now warranted to evaluate the safety and efficacy of this approach.

Isolation, characterization, and functional assessment of novel smooth muscle like stem progenitors

Vascular smooth muscle cells (VSMC) are one of the key players in the pathogenesis of cardiovascular diseases. The origin of neointimal VSMC has thus become a prime focus of research. VSMC originate from multiple progenitors cell types. In embryo the well-defined sources of VSMC include; neural crest cells, proepicardial cells and EPC. In adults, though progenitor cells from bone marrow (BM), circulation and tissues giving rise to SMC have been identified, no progress has been made in terms of isolating highly proliferative clonal population of adult stem cells with potential to differentiate into SMC. Smooth muscle like stem progenitor cells (SMSPC) were isolated from cardiopulmonary bypass filters of adult patients undergoing CABG. Rat SMSPC have previously been isolated by our group from the bone marrow of Fischer rats and also from the peripheral blood of monocrotaline induced pulmonary hypertension (MCT-PHTN) animal model. Characterization of novel SMSPC exhibited stem cell characteristics and machinery for differentiation into SMC. The expression of Isl-1 on SMSPC provided unique molecular identity to these circulating stem progenitor cells. The functional potential of SMSPC was determined by monitoring adoptive transfer of GFP+ SMSPC in rodent models of vascular injury; carotid injury and MCT-PHTN. The participation of SMSPC in vascular pathology was confirmed by quantifying the peripheral blood, and engrafted levels of SMSPC using RT-PCR. In terms of translating into clinical practice, SMSPC could be a good tool for detecting the atherosclerotic plaque burden. The current study demonstrates the existence of novel adult stem progenitor cells in circulation, with the potential role in vascular pathology.

Towards a cognitive neurobiology of brain-gut axis disorders

The past two decades have seen substantial gains in our understanding of the complex processes underlying disturbed brain-gut communication in disorders such as irritable bowel syndrome (IBS) and inflammatory bowel disease (IBD). Despite a growing understanding of the neurobiology of brain-gut axis dysfunction, there is a relative paucity of investigations into how the various factors involved in dysregulating the brain-gut axis, including stress, immune activation and pain, could impact on fundamental brain processes such as cognitive performance. To this end, we proposed a cognitive neurobiology of brain-gut axis dysfunction and took a novel approach to examine how disturbed brain-gut interactions may manifest as altered cognitive performance in IBS and IBD, both cross-sectionally and prospectively. We have demonstrated that, disorders of the brain-gut axis are characterised by stable deficits in specific cognitive domains. Specifically, patients with IBS exhibit a consistent hippocampal mediated visuospatial memory impairment. In addition we have found evidence to suggest a similar visuospatial impairment in IBD. However, our most consistent finding within this population was that patients with Crohn’s disease exhibit impaired selective attention/ response inhibition on the classic Stroop interference test. These cognitive deficits may serve to perpetuate and sustain brain-gut axis dysfunction. Furthermore, this research has shed light on some of the underlying neurobiological mechanisms that may be mediating cognitive dysfunction in IBS. Our findings may have significant implications for the individual who suffers from a brain-gut axis disorder and may also inform future treatment strategies. Taken together, these findings can be incorporated into existing neurobiological models of brain-gut axis dysfunction, to develop a more comprehensive model accounting for the cognitive-neurobiology of brain-gut axis disorders. This has furthered our understanding of disease pathophysiology and may ultimately aid in both the diagnosis and treatment of these highly prevalent, but poorly understood disorders.

Mesenchymal stem cell therapy for the treatment of myocardial infarction

Mesenchymal stem cells (MSCs) are currently under investigation as repair agents in the preservation of cardiac function following myocardial infarction (MI). However concerns have emerged regarding the safety of acute intracoronary (IC) MSC delivery specifically related to mortality, micro-infarction and microvascular flow restriction post cell therapy in animal models. This thesis aimed to firstly identify an optimal dose of MSC that could be tolerated when delivered via the coronary artery in a porcine model of acute MI (AMI). Initial dosing studies identified 25x106 MSC to be a safe MSC cell dose, however, angiographic observations from these studies recognised that on delivery of MSC there was a significant adverse decrease in distal blood flow within the artery. This observation along with additional supportive data in the literature (published during the course of this thesis) suggested MSC may be contributing to such adverse events through the propagation of thrombosis. Therefore further studies aimed to investigate the innate prothrombotic activity of MSC. Expression of the initiator of the coagulation cascade initiator tissue factor (TF) on MSC was detected in high levels on the surface of these cells. MSC-derived TF antigen was catalytically active, capable of supporting thrombin generation in vitro and enhancing platelet-driven thrombus deposition on collagen under flow. Infusion of MSC via IC route was associated with a decreased coronary flow reserve when delivered but not when coadministered with an antithrombin agent heparin. Heparin also reduced MSC-associated in situ thrombosis incorporating platelets and VWF in the microvasculature. Heparin-assisted MSC delivery reduced acute apoptosis and significantly improved infarct size, left ventricular ejection fraction, LV volumes, wall motion and scar formation at 6 weeks post AMI. In addition, this thesis investigated the paracrine factors secreted by MSC, in particular focusing on the effect on cardiac repair of a novel MSC-paracrine factor SPARCL1. In summary this work provides new insight into the mechanism by which MSC may be deleterious when delivered by an IC route and a means of abrogating this effect. Moreover we present new data on the MSC secretome with elucidation of the challenges encountered using a single paracrine factor cardiac repair strategy.

Living with acquired brain injury

This study found that natural community supports were comprised of two distinct groupings; firstly immediate families, friends and peer support groups; secondly neighbours and local community groups such as sporting and activity- based organisations and groups. The findings of this study indicate that living with acquired brain injury involves a process where the person moves from acute high intensity health services onto rehabilitative services and then onto re-establishing independent lives. It is evident that smooth transitions and interconnectivity of services are essential in facilitating this recovery process. Instrumental to the recovery is the support of immediate family and close friends, who form people’s immediate natural support network and go a long way towards facilitating individuals in rebuilding their lives. A key finding of this study is that broader natural community supports do not appear to play as central a role in supporting individuals to live independent lives when compared to the role of family and friends. The lack of involvement of broader community groups, in many ways, prompted individuals to contact formal support services. For the majority of participants, independence is facilitated through the combination of immediate natural community supports and formal services. The role of formal support services is key to developing broader community support networks. This study found a blurred division between formal services and broader community support networks. The authors recommended that the role of formal supports services in acting as a bridge between the needs of the individual and the development of meaningful community networks, be formally recognised and further developed. Additionally, they argued that the importance of the role of broader natural community, supports such as those provided by community and sporting groups must be enhanced. Greater awareness of the issues faced by people living with acquired brain injury and its often invisible nature is necessary in this endeavour. The authors stated it is important to recognise that there are multiple issues impacting on independent living and these issues intersect, for instance with age, gender, employment, qualifications and so on. A lack of public awareness of acquired brain injury was found to be a key barrier to independent living, along with issues relating to socialising, access to employment and finances. The findings of this study reflect the complexities of living with acquired brain injury and the need for holistic support that is cognisant of the factors which impact on integration. It is vital that flexible, personalised services are developed which are fit for purpose and meet the needs of not only people with acquired brain injury but also their immediate natural community support network. Recognition of the intersection between immediate/ broader natural community supports and formal services is also key to developing the comprehensive and practical supports required to achieve an independent life. This was a qualitative study and all participants were sourced through Headway, a community based service provider for people with ABI. Data collection was divided into two stages: firstly focus groups, followed by individual interviews. Four focus groups were convened in Cork (2), Dublin (1) and Limerick (1). Each focus group was facilitated by at least two members of the research team and a total of twenty-six individuals participated in the focus groups. Thematic analysis of the data was undertaken to guide and inform the second stage of the study; the individual interviews. Ten interviews were undertaken with individuals who presented with ABI in the Cork and Limerick regions.