Browsing by Author "Solms, Mark"

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    Active Inference in Multi-Objective Dynamic Environments
    (2022) Hodson, Rowan; Shock, Jonathan; Smith, Ryan; Solms, Mark
    Artificial Intelligence holds the promise of not only creating intelligent entities, but also unlocking the mysteries of our brains, and the nature of the subjective consciousness that accompanies them. Many paradigms of artificial intelligence are attempting to push the boundaries of the field, in order to catch a glimpse of the secrets behind general intelligence and the nature of the human mind. A less explored, yet promising paradigm is that of Active Inference - a theory which details a first-principled explanation of how agents use action and perception to successfully operate within an external environment. Much work has been done to explore the framework's viability in modelling scenarios both related to neural process theory and more classical agent-based machine learning. However, due to the relative recency of the theory, there are still many areas of comparison and evaluation to explore. This dissertation aims to investigate Active Inference's algorithmic capacity to solve more complex decision-based environments. Specifically, with varying degrees of complexity, I make use of a dynamic environment with a multi-objective reward function to investigate the Active Inference agent's ability to learn and plan while balancing exploration and exploitation, and compare this to other Bayesian Machine Learning algorithms. In doing so, I investigate some novel approaches and additions to Active Inference's algorithmic structure which include a dynamic preference distribution, a two-tiered hierarchical approach to the state space (using model-free Reinforcement Learning to solve the lower level), and the introduction of the Propagated Parameter Belief Search algorithm - a modification to Active Inference which allows the agent to perform more complex counterfactual reasoning.
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    Affective agnosia: a core affective processing deficit in the alexithymia spectrum
    (2020-09-04) Lane, Richard D; Solms, Mark; Weihs, Karen L; Hishaw, Alex; Smith, Ryan
    Abstract Affective agnosia, an impairment in knowing how one feels emotionally, has been described as an extreme deficit in the experience and expression of emotion that may confer heightened risk for adverse medical outcomes. Alexithymia, by contrast, has been proposed as an over-arching construct that includes a spectrum of deficits of varying severity, including affective agnosia at the more severe end. This perspective has been challenged by Taylor and colleagues, who argue that the concept of affective agnosia is unnecessary. We compare these two perspectives by highlighting areas of agreement, reasons for asserting the importance of the affective agnosia concept, errors in Taylor and colleagues’ critique, and measurement issues. The need for performance-based measures of the ability to mentally represent emotional states in addition to metacognitive measures is emphasized. We then draw on a previously proposed three-process model of emotional awareness that distinguishes affective response generation, conceptualization and cognitive control processes which interact to produce a variety of emotional awareness and alexithymia phenotypes - including affective agnosia. The tools for measuring these three processes, their neural substrates, the mechanisms of brain-body interactions that confer heightened risk for adverse medical outcomes, and the differential treatment implications for different kinds of deficits are described. By conceptualizing alexithymia as a spectrum of deficits, the opportunity to match specific deficit mechanisms with personalized treatment for patients will be enhanced.
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    Assessing the effect of Addison's disease on patient quality of life within the South African context
    (2008) Madadi, Nazanin; Solms, Mark
    This study finds that our patients do indeed have the same QOL, and that we should therefore be able to apply the European findings here. Measuring QOL alone, however, gives us very general information which is not sufficient for our study. The second aim of this research is to compare different aspects of QOL in AD, as this has not been researched before. This knowledge should help clinicians to recognise QOL impairment better, which will enable modifiable risk factors to be adjusted with early intervention. (For example, psychological impairment can be reduced with counselling.) This study also finds that some AD patients who suffer a combination of other autoimmune diseases have a lower QOL. The main instrument used for this research was the Rotterdam QOL questionnaire.
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    Brain mechanisms of dreaming
    (2007) Yu, Calvin Kai-Ching; Solms, Mark
    This thesis comprises a series of six studies, aiming at clarifying some controversies surrounding the neuropsychological understanding of dreaming and the methodological issues of neuroanatomical investigation.
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    The causal role of mood in confabulation
    (2003) Williams, Cara; Solms, Mark
    Following a presumed haemorrhage in the hyplthalamic area during an operation to remove a tumour from the diencephalon and frontal lobes, a man (CA) presented with confabulatory amnesia. Previous research papers have shown that confabulations (CA's included) have a positive emotional bias and Turnbull et al. (in press) have demonstrated that low mood appears to co-occur with confabulation. This paper explores the mood of CA across time.
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    Cerebral Arterial Asymmetries in the Neonate: Insight into the Pathogenesis of Stroke
    (Multidisciplinary Digital Publishing Institute, 2022-02-24) van Vuuren, Anica Jansen; Saling, Michael; Rogerson, Sheryle; Anderson, Peter; Cheong, Jeanie; Solms, Mark
    Neonatal and adult strokes are more common in the left than in the right cerebral hemisphere in the middle cerebral arterial territory, and adult extracranial and intracranial vessels are systematically left-dominant. The aim of the research reported here was to determine whether the asymmetric vascular ground plan found in adults was present in healthy term neonates (n = 97). A new transcranial Doppler ultrasonography dual-view scanning protocol, with concurrent B-flow and pulsed wave imaging, acquired multivariate data on the neonatal middle cerebral arterial structure and function. This study documents for the first-time systematic asymmetries in the middle cerebral artery origin and distal trunk of healthy term neonates and identifies commensurately asymmetric hemodynamic vulnerabilities. A systematic leftward arterial dominance was found in the arterial caliber and cortically directed blood flow. The endothelial wall shear stress was also asymmetric across the midline and varied according to vessels’ geometry. We conclude that the arterial structure and blood supply in the brain are laterally asymmetric in newborns. Unfavorable shearing forces, which are a by-product of the arterial asymmetries described here, might contribute to a greater risk of cerebrovascular pathology in the left hemisphere.
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    Changes in dream frequency, vividness and intensity in subjects taking selective serotonin reuptake inhibitors
    (2005) Kinnear, Helen; Solms, Mark
    Various sources of evidence suggest that dream frequency, intensity and vividness are increased with the use of selective serotonin reuptake inhibitors (SSRJ's) commonly prescribed for depression and anxiety. In this study the effects ofSSRI use on dream frequency, intensity and vividness in psychiatric patients was examined through a comparision of the dream characteristics of an SSRI- medicated patient group vs. an unmedicated patient control group. Each group comprised 20 patients recruited through state psychiatric outpatient facilities affiliated with two research universities. Age and gender were evenly spread across the two groups. Psychiatric disorders represented were generalised an.xiety disorder, panic disorder, obsessive-compulsive disorder and social phobia. Patients completed a questionnaire consisting of a most recent dream report and self-report likert-scaled questions regarding dream frequency, intensity, vividness and memorability. Two independent raters rated the dream reports for intensity on a likert scale. Self-reported visual vividness was significantly higher (p=0.027, effect size .86) among SSRI users compared with controls, whereas selJreported dream frequency and emotional intensity as well as independent raters assessment of dream intensity were not significantly different across the two groups. Findings of increased dream vividness without increases in dream frequency complement the results of an earlier study. Since serotonin is suppressed during REM sleep, these findings cast further doubt upon the notion of an isomorphic link between REM sleep and dreaming and argue for the searchfor a more sophisticated model of neurotransmitter modulation of sleep-cognition.
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    The cognitive effects of Obstructive Sleep Apnoea Syndrome (OSAS) : a comparison between untreated patients and patients on at least 3 months Continuous Positive Airway Pressure (CPAP) treatment
    (2006) Wong, Andrea Jane; Ameen, Ozayr; Solms, Mark
    Objectives: To investigate whether or not OSAS patients from the South African population showed any cognitive impairment relative to healthy individuals from the same population, and to assess whether or not untreated OSAS patients and patients on CPAP treatment differed in their cognitive functioning.
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    Cognitive outcome of aneurysmal subarachnoid haemorrhage after clipping or coiling : a comparative post intervention study in a hospital population
    (2005) Pantelis, Eleni; Solms, Mark
    Subarachnoid haemorrhage secondary to ruptured cerebral aneurysm and clipping are associated with substantial morbidity and mortality. Despite favourable neurological outcomes, many patients report persistent cognitive and emotional deficits post intervention. To compare cognitive and quality of life outcomes in patients with ruptured aneurysmal subarachnoid haemorrhage treated with surgical clipping or endovascular coiling. Twenty-four patients with aneurysmal subarachnoid haemorrhage treated by clipping or coiling were retrospectively assessed by use of a battery of cognitive tests and a quality of life questionnaire. All patients had favourable grades on admission, that is, WFNS <= 2 and favourable neurological grades on discharge, that is, GOS <=2. treated with surgical clipping or endovascular coiling. Patients in the two treatment groups were matched on age, years of education and on premorbid IQ. The two groups were further matched on time from intervention to assessment and number of treatments. The cognitive performance of the treatment groups was compared to hospitalised controls, matched for age, years of education and premorbid IQ. Comparison of cognitive outcome between the two groups indicated a trend towards poorer outcome in the surgical group which achieved significance on six test measures. There were no significant differences with respect to the quality of life measure. Patients surviving aneurysmal subarachnoid haemorrhage are likely to suffer from a 'subarachnoid-induced encephalopathy' which appears to be more aggravated by the invasive nature of surgery, compared to endovascular coiling, as demonstrated by the poorer cognitive performance ofthe clipping patients.
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    Cognitive outcomes in adults with HIV-associated Tuberculous Meningitis
    (2017) Albertyn, Christine Herculine; Solms, Mark; Marais, Suzaan; Gouse, Theta; Bateman, Kathleen
    Tuberculous meningitis (TBM) is a common cause of meningitis in adults in South Africa (1-3), second only to cryptococcal meningitis in studies of microbiologically confirmed meningitis, and accounting for 28% of cases in one (1). Conventional diagnostic tests for TBM are, however, relatively insensitive, and the true incidence is likely to be underreported. When both microbiological and clinical diagnostic criteria (4) are used in the same setting, the incidence of TBM rose to 57% (3), emerging as the most common cause of meningitis in adults in a district level hospital in the Western Cape. In the setting of high human immunodeficiency virus (HIV) and tuberculosis (TB) prevalence, approximately 88% of patients with definite or probable TBM are co-infected with HIV (3, 5) and six-month mortality in this group approaches 50% (3). Survivors may be left with long-term disability secondary to hydrocephalus, cranial neuropathies, seizures and strokes (6).
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    Cognitive, social and emotional processes in unawareness of illness following stroke
    (2015) Besharati, Sahba; Solms, Mark; Fotopoulou, Aikaterini
    Disturbances in unawareness can offer an important avenue to investigate the neurocognitive processes involved in the construction of the bodily self. The general aim of the present thesis was to advance the current state of knowledge on a prototypical disorder of self-awareness, anosognosia for hemiplegia (AHP): unawareness of motor deficits contralateral to a brain lesion. Based on insights gained from both clinical and experimental research on anosognosia, it is argued that purely sensorimotor accounts do not explain several features of the syndrome, such as the delusional and emotional aspects. Therefore a revision of prevailing, modular theories of anosognosia is proposed that take into account the involvement of affective and so cial processes. Accordingly, the thesis aimed to: (1) investig ate the emotional and social factors that underlie motor unawareness; (2) identify the neurocognitive factors and neuroanatomical correlate that underlie such factors; and (3) develop potential, bedside rehabilitation interventions for AHP that are informed by the above investigations. These aims were achieved using an integrative methodological approach, which combined neuropsychological testing, psychophysiological experiments and neuroimaging methods. A series of experiment al group investigations and clinical case studies were conducted in 53 adult patients with right-hemisphere strokes. The main results of these studies showed that: (i) motor awareness is modulated by negative, but not positive emotion in a social context; (ii) anosognosia is associated with specific deficits in 3rd person perspective taking in visual-spatial and mentalising tasks; (iii) anosognosia is modulated by 'other' referent and 3rd person verbal and visual perspective taking. These experimental findings on the role of emotion and social processes in AHP were in turn used to develop a rehabilitation intervention applied in two case studies that showed promising results. Additionally, converging neuroimaging evidence provided support for the unique involvement of the inferior frontal gyrus, insula ribbon, supramarginal and superior temporal gyrus, and dorsal frontal white matter in anosognosia, which have well-established links to motor monitoring, subjecting feelings and self-awareness, and the proposed 'mentalising network'. These finding are in support of a proposed new account of AHP, which move s away from traditional modular theories of anosognosia, towards a dynamic model of the construction of the bodily self.
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    Colorectal cancer : a neuropsychological approach to non-adherence to screening guidelines of individuals with Lynch syndrome in the Western Cape
    (2010) Northam, Amy; Solms, Mark
    Lynch syndrome (LS), the most common form of inherited colorectal cancer (CRC), carries with it a lifetime risk of approximately 80% of developing CRC. This study identified unexpected findings with regard to the relationships between neuropsychological functioning, knowledge and non-adherence within the context of LS, and highlights ways in which this might be investigated in the future.
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    Do dreams protect sleep? Testing the Freudian hypothesis of the function of dreams
    (2012) Cameron-Dow, Catherine; Solms, Mark
    A review of the literature indicates that a physiological function for dreaming has not yet been empirically established. Based on recent findings regarding the neural correlates of dreaming, this study tested the Freudian hypothesis that dreams protect sleep. In order to do this, sleep architecture in patients who had experienced dream loss as a result of thrombotic stroke in the region of the posterior cerebral arteries was compared with that of patients with the same pathology who had not experienced dream loss. Using medical records, structural neuro-imaging, clinical interviews, neuropsychological testing, analysis of subjective sleep quality, and polysomnographic data collected over two consecutive nights in the sleep laboratory, two non-dreaming and three dreaming cases were studied. Analysis of the individual case studies indicates that sleep was disrupted in both non-dreaming cases.
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    Dreaming and the dorsolateral frontal lobes : towards a better understanding of the mechanism of dreaming
    (2006) Badenhorst, Tania; Solms, Mark
    The exact mechanism of dream production is still poorly understood. Based on exploratory findings that damage to the dorsolateral prefrontal cortex does not cause changes in these patients subjective experience of their dreams (Solms, 1997), a study was conducted in order to investigate the role of this area in dream production. The dreams of seven patients with damage to tile dorsolateral prefrontal cortex were compared with those of normal participants. A content analysis found no significant quantitative differences between the dreams of dorsolateral prefrontal patients and normal controls. In addition, none of the patients with damage to the dorsolateral prefrontal cortex reported any subjective changes in their dreams since falling ill. These findings are congruent with those or numerous neuro-imaging studies, which indicate that the dorsolateral prefrontal cortex is deactivated during dreaming, and provide support for the theory that deactivation of the dorsolateral prefrontal cortex during sleep accounts for many of the formal features of dreams.
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    Dreaming in Urbach-Wiethe patients the effect of amygdala damage on dreaming
    (2012) Koopowitz, Sheri; Solms, Mark
    As it stands, there is a paucity of literature looking at the effect of damaged amygdalae on dreaming and dream content. Of the many functions, the amygdala is heavily involved in processing emotional stimuli and fear conditioning. In Revonsuo’s threat simulation theory (TST), the amygdala plays an important role in the threat simulation mechanism. This mechanism evaluates the threatening situation, then chooses and executes the avoidant type behaviour to successfully avoid the potential threat. All of this is done in the dream world to ensure that humans have a safe virtual environment in which to practice these responses. To test this theory, a sample of people without a functioning amygdala was needed. Unfortunately, bilateral amygdala lesions are extremely rare in the human population. Urbach-Wiethe disease (UWD) is a rare, autosomal recessive disorder that presents with characteristic amygdala calcifications. A sample of 8 UWD patients and 8 matched controls (all females) from the Northern Cape in South Africa were used.
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    Emotional biases in confabulation : the role of the frontal lobes
    (2004) Balchin, Ross; Solms, Mark
    The neuropsychological understanding of confabulation has recently been enriched by the finding that confabulating patients present positive emotional biases in their false recollections. The exact mechanisms of this motivational phenomenon have been heuristically linked to the frontal lobe impairment accompanying confabulation. The present study aims at providing direct support for this claim. A patient with damage to the prefrontal cortex is examined and his performance is contrasted with two confabulating patients, a patient with non-frontal neurological damage and twenty matched controls on a number of tests of emotional processing.
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    Euphoria in multiple sclerosis: an investigation of constructs and symptons
    (2014) Duncan, Amy Louise; Solms, Mark; Malcolm-Smith, Susan
    In multiple sclerosis (MS), some patients are said to present with unawareness of deficit, and positive mood and optimism that is out of place or incongruous given the patient's circumstances. The history of these symptoms, collectively known as euphoria, however, is characterised by marked inconsistencies regarding a number of aspects of these symptoms. This research attempted to investigate both the constructs, and the symptoms themselves, with the aim of better defining and broadening our understanding of euphoria. Results revealed that a change in the definition of euphoria appears to have occurred since the concept was introduced by Cottrell and Wilson. Different operational definitions appear to be partly responsible for the very different incidence rates reported throughout the literature. Instead of the classical three types of euphoria identified by the classical authors, or the single type utilised in the contemporary literature, the current research revealed two types of euphoria in MS (viz. positivity and unawareness). Positivity appears to be a subjective mood/outlook experienced by the patient and not an outward façade projected by the euphoric individual, and was defined in fairly subtle terms. Unawareness appears to relate to a number of domains (including physical, cognitive and mood or behavioural deficits), and was measured via participant/informant discrepancies on self-report questionnaires. Both positivity and unawareness were represented on a continuum and appeared to have different demographic, disease and cognitive correlates. Positivity was significantly predicted by a medical history of conditions that can affect neuropsychological functioning. Unawareness of physical deficits was associated with a female gender, a younger age, a lower income, relapsing-remitting course, a current disease state of relapse or exacerbation, a shorter disease duration, but a greater disease severity in terms of physical disability. Severity of the disease and the cognitive composite representing cognitive functions sub-served by the orbitobasal frontal cortex were also significant individual predictors of unawareness of physical deficits. Visuospatial ability significantly predicted unawareness of cognitive deficits. No demographic, disease or cognitive correlates of unawareness of mood or behavioural deficits were identified. Finally, no indisputable single cause underlying the two types of euphoria in MS identified by this research was isolated by the exploratory investigations undertaken; however interesting preliminary findings that may tentatively implicate executive dysfunction as well as, possibly, immunological disease processes in the etiology of euphoria in MS were revealed. These results have broadened our understanding of euphoria in MS and may shape both the research and clinical work with euphoric patients going forward.
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    Exploring the utility of pupillometry as a biomarker for relationships between early life stress, emotion regulation, and cognition
    (2024) Buenk, Caitlin; Solms, Mark
    While the negative effects of early life stress (ELS) are well-documented, non-invasive biomarkers that can be used to aid early detection of vulnerable groups and overcome some of the limitations of self-report tools are not readily available. Recently, pupillometry has been recognised as a novel, non-invasive approach to identify potential abnormalities in cognitive and emotional functioning linked to ELS and stress-induced alterations in the locus coeruleus-norepinephrine (LC-NE) pathway. However, to date, no studies have investigated the relationship between pupil dilation (PD) and blink rate (EBR), and ELS. In this study, we therefore explored the utility of pupillometry for distinguishing between groups of participants with histories of high versus low ELS. We investigated to what extent ELS predicts PD during cognitive processing in adulthood and the potential roles of cognitive ability, mood, and emotion regulation style in these relationships. Participants (N = 94) completed the Traumatic Antecedents Questionnaire, Emotion Regulation Questionnaire, and Beck Depression and Anxiety Inventories. PD in response to a challenging cognitive task was used as a proxy for active coping or cognitive effort. Heart rate variability served as a physiological biomarker of emotional regulation. A battery of cognitive tests were utilised to assess core domains of cognition. We hypothesised that PD responses would differ between ELS groups under the baseline and cognitive conditions and depression would be associated with a reduced EBR. Our results indicated that the high ELS group had more depressive symptoms, lower levels of dopamine, and poorer cognitive outcomes, irrespective of education and age. There was evidence to suggest that emotional disturbance may be linked to alterations in the LC-NE pathway as a more rapid decline in pupil size was observed in participants with more depressive symptoms during the memory recall task condition. However, contrary to our hypothesis, there were no anomalies in PD directly related to ELS. While self-report tools that assess mood disturbances appear to offer more predictive power, the clinical utility of pupillometry as a biomarker of the effects of ELS is still under debate due to methodological limitations.
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    The functional neurophysiological sequelae associated with high frequency dream recallers
    (2018) van Wyk, Mariza; Solms, Mark; Lipinska, Malgorzata
    Background: Dreaming is a universal experience, yet there is considerable inter-individual variability with regard to dream recall frequency (DRF). Research on DRF has been prolific leading to the development of various models delineating possible processes involved in dream recall. One such model is the 'arousal-retrieval' model positing that intra-sleep wakefulness is required for dream traces to be encoded into long-term storage, essentially proposing increased DRF as a product of a better memory for dreams. Results from recent studies support this model by demonstrating longer periods of intra-sleep wakefulness in high frequency recallers (HFRs) compared to low frequency recallers (LFRs). Furthermore, results showed heightened brain reactivity, as well as increased regional cerebral blood flow in areas in the brain associated with dream production. These results are indicative of the existence of a functional neurophysiological trait innate to HRs, while also supporting the premise that apart from a better memory for dreams, HRs also may produce more dreams. Awakenings from rapid eye movement (REM) sleep yield the highest dream recall rates, rendering REM sleep as a reasonable starting point for studying rates of dream production. Furthermore, increased dream production during REM sleep might also affect related processes, for example, leading to enhanced overnight emotional memory consolidation and emotion regulation. Hypotheses: The current study investigated the functional neurophysiological sequelae associated with HFRs in a design where HFRs are compared to LFRs. Hypotheses include: (1) HFRs will score significantly higher on certain personality dimensions; (2) HFRs will experience significantly more awakenings, as well as longer periods of intra-sleep wakefulness; (3) HFRs will have significantly higher rates of dream production as measured by the frequency of eye movements (REM density) during REM sleep; and (4) increased dream production during REM sleep will lead to enhanced overnight emotional memory consolidation and emotion regulation in HFRs. Methods: The study consisted of two groups of healthy young adults: high frequency recallers (n = 19) and low frequency recallers (n = 17) who underwent polysomnographic recordings on two non-consecutive nights. Memory tasks and affective questionnaires were completed before and after a night of sleep. Results: (1) HFRs scored significantly higher on the 'agreeableness' personality dimension and on the Boundary Questionnaire; (2) HFRs experienced significantly more awakenings, especially from stage 2 non-rem (NREM) sleep, as well as significantly longer periods of intra-sleep wakefulness; (3) no significant between-group differences with regard to REM density, nor (4) overnight emotional memory consolidation and emotion regulation were found. Conclusion: Results support, firstly, the proposition that certain personality traits, differences in sleep architecture, and increased DRF are an expression of a functional neurophysiological arrangement innate to HFRs. Secondly, the findings suggest that NREM sleep, as opposed to REM sleep, is important in relation to DRF in this specific population. This is the first study to not only replicate existing findings, but to also contribute to the extant literature by illuminating additional characteristics and features associated with HFRs.
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    The genesis and development of the Groote Schuur neurocognitive screening battery : a neurocognitive screening tool for the South African context
    (2008) Balchin, Ross; Solms, Mark
    This study sought to address this need by developing and validating the Groote Schuur Neurocognitive Screening Battery Prototype, a theory-driven tool created in response to requests by Groote Schuur Hospital neurologists for a suitable replacement for the Mini-Mental State Examination. The design of this battery constitutes a "middle ground" between the hypothetico-deductive and psychometric approaches to neurocognitive assessment. However, the Prototype had a number of limitations: it was not available in languages other than English, it contained many culturally biased tests and its validity and reliability had yet to be formally established.