<p>The research studies presented as this dissertation constitute a methodologically diverse and conceptually integrative approach to understanding impulsiveness in the context of cognitive control and decision making. Broadly, these findings address the validity of current conceptions of trait impulsiveness, relationships between those traits and brain or laboratory measures of cognitive control, and links between impulsive traits and economic decisions under conditions of delay or uncertainty. The findings presented in this thesis affirm the multidimensional nature of impulsiveness as a construct, and link individual differences in specific impulsive types to behavioral and neurobiological measures of control function. The nature of motor, attentional, and nonplanning impulsive types are contextualized by reference to evidence supporting a broad theory of behavioral control based on hierarchical organization of action, ranging from concrete acts to abstract plans and strategies. We provide evidence linking concrete forms of urgent/motor impulsiveness to behavior and brain activation during response-related control, and more abstract and future-oriented premedititative/nonplanning impulsiveness to strategic control signals in more rostral PFC. Finally, these findings are complemented by causal evidence from a neurostimulation study linking a contextual control network to risky decision making and attentional impulsiveness.</p> / Dissertation

The DSM-IV characterizes dissociation as “disruption in the usually integrated functions of consciousness, memory, identity, or perception of the environment” (American Psychiatric Association, 1994, p. 477) and it has been tenuously linked with trauma, but “lacks a single, coherent referent … that all investigators in the field embrace” (Cardena, 1994). It is known that dissociation is a spectrum (Bernstein and Putnam, 1986; Shor, Orne, and O’Connell, 1962; Spiegel, 1963; Tellegen and Atkinson, 1974), and low levels of dissociation can be a part of normal functioning, allowing us to do two things at once (Butler, Duran and Jasiukitis, 1996), but higher levels can interfere with daily functioning. The present study used survey techniques to investigate the link between dissociation and trauma. Survey results showed a significant correlation between trauma and dissociation. The current investigation also used the high temporal and spatial resolution of electroencephalographic techniques to identify the neurophysiological correlates of dissociation. Specifically, the current investigation recorded early and late event-related potentials in participants who rated high and low in dissociation while they viewed affective pictures in order to determine if there were electrophysiological differences in responses to emotional stimuli. Electroencephalographic results were nonsignificant, but trends indicated that high dissociators showed a heightened response to affective photos at P1 and the late positive potential compared with low dissociators. If the results are thought to be reliable, the trends may indicate that high dissociators were not actively dissociating during the task, and because high dissociators have usually experienced trauma, they are more sensitive to emotional stimuli. Further research is needed to support these theories.

This thesis considers the phenomenological experience of e-reading (reading on an electronic screen) as a way-in to discussing wider issues of technology and our encounter with objects in our environments. By considering the resistance shown toward reading on iPads and Kindles in popular and academic discourse as a source of valuable “folk phenomenological” report, this thesis hopes to shed light on both the particular engagement of portable e-reading and the general experience of embodied encounters with artefacts. The first chapter will consider the shortcomings of contemporary definitions of technology and aims to provide its own definition commensurate to the task of describing the intimate and very human encounter with equipment, an encounter which will be described as “technological.” In the second chapter an ontology (begun in the background of the first) will be developed which primarily considers our encounter with things that are as embodied as ourselves. This ontology sees evolution as an epistemological concern, with every evolutionary act occurring as a response to environmental pressures and producing a knowledge of that environment. This knowledge, it will be argued, in light of conclusions drawn from an engagement with Object Oriented Ontology, can be tested only via repeatable successful action with that which might be known. Such evolutionary concerns, it will be further argued, are equally applicable to our artefacts. The third chapter will focus on metaphor and critical theory to consider how e-reading in particular might function as a material metaphor, enabling productive thought. It will conclude with readings of three texts which put the language of all three chapters to work. This thesis draws on several fields, including Critical Theory, Cognitive Neuroscience, Evolutionary Epistemology, and Philosophy, the bringing together of which is intended to be of use to the still emerging Digital Humanities and the work's home discipline of English Studies as it gets used to the substantial alterations in the substrate of its object of study.

Individuals diagnosed with schizotypal personality disorder (SPD) exhibit patterns of cognitive deficits in (1) attention (Lees-Roitman, Cornblatt, Bergman, Obuchowski, Mitropoulou, Keefe, Silverman, & Siever, 1997), (2) memory (Bergman, Harvey, Lees-Roitman, Mohs, Margerm, Silverman, & Siever, 1998), (3) executive functioning (Cadenhead, Perry, Shafer, & Braff, 1999), and recently (4) neuromotor functioning (Neumann & Walker, 1999), similar to individuals with a diagnosis of schizophrenia. Furthermore, recent research suggests a link between neuromotor and cognitive functioning in schizophrenia spectrum disorders (SSDs) (Neumann & Walker, 2003). The current study is an extension of research on non-drug-induced neuromotor disturbances in individuals with SPD and examines how such disturbances covary with neurocognitive measures. Approximately thirty-three adults (18-65) were rated for SPD symptoms. Motor assessments included a computerized motor task and finger tapping test. Cognitive assessments included measures of attention, verbal and visual memory, and executive functioning. Consistent with previous research, the SPD group displayed significant right hand (left hemisphere) motor disturbances (i.e., increased force and force variability) compared to healthy controls after excluding all cases reporting a history of head injury. In addition, results indicate significant associations between motor, cognitive, and symptom variables. Consistent with previous research, neuromotor functioning and the relationships between motor and cognitive functioning varied as a function of Time of Day (TOD) of testing. Understanding the relationship between neuromotor and neurocognitive functioning may help elucidate the neural systems that contribute the symptoms characteristic of SSDs.

The main aim of the experiments reported in this thesis was to explore the neural mechanisms underlying the temporal orienting of attention. In Chapter 3, I explored the possible dissociation between exogenous and endogenous temporal orienting by comparing reaction times to targets appearing after rhythmic or symbolic cues. Behavioural results provided evidence for the existence of dissociable exogenous and endogenous types of temporal orienting of attention. The experiment in Chapter 4 combined spatiotemporal expectations using rhythmic moving cues to test the modulatory effect of exogenous temporal orienting in the brain. Specifically, I used EEG to test the effect of temporal orienting on perceptual and motor stages of target analysis, as well as on anticipatory oscillatory brain activity. The time-frequency analysis revealed that rhythmic cues can entrain slow brains oscillations, providing a putative mechanism for enhancing the perceptual processing of expected events. Spatiotemporal expectations also modulated the amplitude of visual responses and the timing and amount of preparatory motor activity. In Chapter 5, I used a novel task to explore the neural modulatory effects of spatial and temporal expectations acting in isolation or in coordination. For the first time, the analysis of early visual responses demonstrated that temporal expectations alone, independently of spatial orienting, can enhance early visual perceptual processes. The time-frequency analysis in this experiment showed a desynchronisation of alpha oscillations focused over central-parietal electrodes induced by rhythmic cues that were independent of spatial expectations. When rhythmic cues carried spatiotemporal information, the alpha desynchronisation also spread over contralateral occipital electrodes. In Chapter 6, fMRI was used to test the possible neural dissociation between motor and temporal orienting. The results confirmed the large overlap between these two processes, but also indicated independent behavioural and neural effects of temporal orienting. Temporal orienting activated the left IPS across motor conditions, further implicating the left IPS in temporal orienting. Based on the results of these experiments, directions for future studies are discussed.

The electroencephalogram (EEG) reflects summated, slow post-synaptic potentials of cortical neurons. Sensory, motor or cognitive events (such as a fast-rising sensory stimulus, a brisk self-paced movement or a stimulus-triggered cognitive task) can elicit transient changes in the ongoing human EEG, called event-related potentials (ERPs). ERPs are widely used in clinical practice, and believed to reflect the activity of the sensory system activated by the stimulus (for example, laser-evoked potentials are used to substantiate the neuropathic nature of clinical pain conditions). When ERPs are elicited by pairs or trains of stimuli delivered at short inter-stimulus intervals (ISIs), the magnitude of the ERP elicited by the repeated stimuli is markedly reduced, a phenomenon known as response decrement. While the interval between two consecutive stimuli becomes longer, the reduced response is recovered. Thus, this phenomenon has been traditionally interpreted in terms of neural refractoriness of generators of ERPs ("neural refractoriness hypothesis"). This thesis, however, challenges this neural refractoriness hypothesis by describing the results of manipulating the preceding events of the eliciting stimulus. The first study examined the effect of variable and short ISIs on sensory ERPs, delivering trains of auditory and electrical stimuli with random ISIs ranging from 100 to 1000ms. In the second study, pairs of laser stimuli were presented in two comparable conditions. In the constant condition, the ISI was identical across trials in each block, while in the variable condition, the ISI was variable across trials. By directly comparing ERPs elicited by laser stimulation, this study aimed to explore whether lack of saliency in the eliciting stimulus could explain the response decrement during stimulus repetition. Finally, the third study tested the hypothesis that the reduced eliciting ERPs would recover if saliency were introduced by changing the modality of the preceding event. Thus, trains of three stimuli (S1-S2-S3) with 1s ISI were presented; S2 was either same or different in modality as S1 and S3 in each block. Results from these three experiments demonstrate that this "refractoriness hypothesis" does not hold, and suggest that the magnitude of ERPs is only partly related to the magnitude of the incoming sensory input, and instead largely reflects neural activities triggered by salient events in the sensory environment. These results are important for the correct interpretation of ERPs in both physiological and clinical studies.

Clinical and behavioural evidence has shown that the threat value of pain biases decisions about whether a stimulus is perceived as painful or not, and if yes, how intense is the sensation. This thesis aims to investigate the neural mechanisms underlying the effect of perceived threat on perceptual decisions about pain. The first study investigates the neural mechanisms underlying the effect of threat on the decision about the quality of the sensation, i.e., whether it is perceived as painful or not. The perception of pain (relative to no pain) was associated with activation in the anterior insula as well as an increased connectivity between this region and the mid-cingulate cortex (MCC). Activity in the MCC was correlated with the threat-related bias to perceived pain. In the second study, probabilistic tractography was performed with diffusion tensor imaging to investigate the structural connectivity between subdivisions of the insula and other pain-related regions. Additional analyses revealed that the structural connectivity between the anterior insula and the MCC, and between the posterior insula and somatosensory cortices, is positively correlated with the threat-related bias toward pain. In the third study, a multivariate pattern analysis (MVPA) was performed to investigate whether pain can be decoded from functional neuroimaging data acquired during the anticipation and during the receipt of pain. The results show that pain can be predicted by the pattern of neural activity in the right anterior insula during anticipation and stimulation. The fourth study investigated the effect of uncertainty about the stimulation intensity as a form of threat on the perceived intensity of pain. Uncertainty was found to be associated with an increased activation in the anterior insula. Overall, these findings suggest that a neural network consisting of the anterior insula and the MCC plays a key role in decisions about the quality and the quantity of nociceptive sensation. Results from the MVPA analysis support the notion that perceptual decisions are encoded by a distributed network of brain regions. The variability in anatomical connections between these regions may account for the individual differences in the susceptibility to a threat-mediated bias toward pain.

The aim of this thesis was to understand the function of the frontal lobes during different types of decisions thusfar mostly neglected in cognitive neuroscience. Namely, I sought to understand how decisions are made when comparisons are not about a simple set of concrete options presented, but rather require a comparison with one specific encounter and a sense of the value of the current environment <b>(Chapter 2-3)</b>. Additionally, I wanted to understand how decisions between concrete options can be contextualized by the current environment to allow considerations about changing environmental constraints to factor into the decision making process <b>(Chapter 4-5)</b>. At last, I wanted to test how the potential for future behaviours within an environment has an effect on peoples decisions <b>(Chapter 6)</b>. In other words, how do people construct prospective value when it requires a sense of own future behaviours? All this work was informed by concepts and models originating from optimal foraging theory, which seeks to understand animal behaviours using computational models for different ecological types of choices. Thus, this thesis offers a perspective on the neural mechanisms underlying human decision making capacities that relates them to common problems faced by animals and presumably humans in ecological environments <b>(Chapter 1 and 7)</b>. As optimal foraging theory assumes that solving these problems efficiently is highly relevant for survival, it is possible that neural structures evolved in ways to particularly accommodate for the solution of those problems. Therefore, different prefrontal structures might be dedicated to unique ways of solving ecological kinds of decision problems. My thesis as a whole gives some evidence for such a perspective, as dACC and vmPFC were repeatedly identified as constituting unique systems for evaluation according to different reference frames. Their competition within a wider network of areas appeared to ultimately drive decisions under changing contexts. In the future, a better understanding of those changing interactions between these prefrontal areas which generate more complex and adaptive behaviours, will be crucial for understanding more natural choice behaviours. For this temporally resolved neural measurements as well as causal interference will be essential.

To align the neuropsychological functioning of our adult euthymic patient group with that reported in previous studies on euthymic bipolar disorder (BD), we used a neuropsychological battery that examined sustained attention (Rapid Visual Information Processing Task), verbal memory (California Verbal Learning Task), executive functioning (Intradimensional-Extradimensional Shift Task, Barrett Impulsivity Task, and Framing Task), and emotion responsiveness/regulation (Positive Affect/Negative Affect Scales, Behavioral Inhibition/Behavioral Activation Scale, and Affective Lability/Affective Intensity Scales) in patients versus healthy volunteers (HV). Our results corroborated existing evidence of reduced sustained attention, impaired verbal memory and executive functioning, and abnormal emotional responsiveness and regulation in euthymic BD relative to healthy controls (Chapter 2). To investigate how abnormal development of brain function in BD leads to deficits in decision-making, motor inhibition, and response flexibility, we examined child and adult BD using a novel risky decision-making task, and used cross-sectional (age x diagnosis) functional magnetic resonance (fMRI) designs to examine neural activation associated with motor inhibition and response flexibility in BD relative to HV. During the risky decision-making task, adult euthymic BD patients were no different from healthy controls in their proportion of risky lottery choices over a range of competing lotteries. This matched behavioral performance was associated with similar prefrontal and striatal brain activation between the patient and control groups during response, anticipation, and outcome phases of decision-making (Chapter 3). These results are different from previous studies that have shown increased risk taking during decision-making in euthymic BD. Similarly, young BD patients were no different from age-matched healthy and patient controls in their pattern of decision making during the risky choice task. This was evidenced by a similar number of risky lottery selections over the range of changing expected values between the young BD group and control groups (Chapter 4). Using a cross-sectional, fMRI analytic design during the stop signal task, we found that child and adult BD showed similar behavioral performance to child and adult HV during motor inhibition. However, this matched behavioral performance was associated with abnormal neural activation in patients relative to controls. Specifically, during unsuccessful motor inhibition, there was an age group x diagnosis interaction, with BD youth showing reduced activity in left and right ACC compared to both age-matched HV and adult BD, and adult BD showing increased activation in left ACC compared to healthy adults. During successful motor inhibition there was a main effect of diagnosis, with HV showing greater activity in left VPFC and right NAc compared to BD (Chapter 5). These neuroimaging data support existing laboratory-based evidence of motor inhibition impairments in BD relative to HV, and indicate brain dysregulation during motor control is important to BD pathophysiology. A previous behavioral study showed impaired response flexibility in young BD patients relative to age-matched controls when using the change task. Here, we used the change task during fMRI to examine response flexibility in child and adult BD compared to child and adult HV. We found that patient and control groups showed similar change signal reaction times in response to change cues. However, this matched behavioral performance was associated with abnormal age group x diagnosis activations in brain regions important in signal detection, response conflict, response inhibition, and sustained attention. Specifically, during successful change trials, child BD participants showed frontal, parietal, and temporal hyperactivation relative to healthy children and adult BD, while adult BD showed hypoactivation in these regions relative to healthy adults. These novel fMRI findings during the change task indicate impaired neural activation during response flexibility may be important to the pathophysiology of BD development.

The hippocampus plays an important role in the processing of spatial memory. During exploration, theta oscillations (4-12 Hz) are prominent in the hippocampus, whereas during sleep and rest irregular sharp wave/ripple (SWR) events occur spontaneously in the hippocampus and may support memory consolidation. To date, the ventral sub-region of the rodents hippocampus, has received less attention relative to the more accessible dorsal part. It has been suggested that spatial information decreases along the septo-temporal axis in favour of coding salient features and coordinated oscillatory activity might enable the binding of spatial and nonspatial information. The first goal of my research was to investigate how the spatial representation by dorsal and ventral neurons is organised by theta oscillations in the hippocampal network. The second goal was to investigate the role of the ventral hippocampus in spatial learning. Finally, the third goal examined to what extent the firing relationships established during spatial learning are replayed during subsequent sleep in the ventral CA1. I recorded the network activity of dorsal and ventral CA1 in rats performing a spatial memory task on the cheese board maze (Dupret et al., 2010). By using parallel multi-channel extracellular recordings in the dorsal and ventral portions of the hippocampus in behaving rats, I found that dorsal and ventral CA1 were theta coupled at particular times of the spatial learning. High coherence periods across the two regions were characterized by a strong speed-modulation of ventral theta oscillations, which was absent in other conditions. During sleep, it was found that SWR-related activity was presented in the ventral hippocampus as well, when the coordinated population activity established in spatial learning was reactivated within the two sub-regions. By contrast, reactivation across the two regions was observed outside the SWRs epochs. Overall, the data suggests that the ventral hippocampus might be involved in the processing of salient features of the environment such as rewards. On a temporal scale, this non-spatial information might be integrated to the spatial information provided by the dorsal hippocampus during theta oscillation. During sleep/rest periods, the coordinated communication of learned information might underlie the consolidation of memory traces.