Psychological models of judgment and decision-making that focus on dual processes distinguish between two modes of judgment. One mode of judgment uses incomplete, probabilistic associations that lead to good-enough judgments for most situations. A second mode of judgment uses more complete information and applies deterministic decision rules to reason through a decision. The two modes operate in parallel but they can also interact and may be viewed as ends of a continuum. Although some psychology researchers have hypothesized that the two modes of information processing are carried out by distinct neural systems, neural research has not fully tested the distinctions that psychological research has drawn between the two modes. Three studies aim to address the gap between psychological and neural models of judgment and decision-making. Study 1 addresses the lack of neural research comparing judgments based on probabilistic information (characteristic of the first mode of judgment in dual-process models) with judgments based on deterministic rules (characteristic of the second mode of judgment in dual-process models). Specifically, Study 1 compares basic probabilistic judgments and deterministic rule-based judgments to identify neural regions that are preferentially associated with one mode of judgment. Study 2 moves toward a more ecologically valid investigation of neural systems associated with judgments based on probabilistic associations. That is, Study 2 examines a probabilistic cue that is used in real-world judgments: affect. Study 3 examines neural regions associated with the interaction of the two modes of judgment in the underexplored domain of social evaluation. Modes of judgment may interact when the second mode of judgment uses new information to adjust a judgment previously driven by the first mode of judgment, as when a hiring manager uses information about a job candidate to adjust a first impression initially based on appearance. Study 3 examines the neural systems involved when people use newly available information to adjust a previously made affectively-driven judgment. Findings in the three studies contribute to scientific understanding of how neural regions support judgment, but do not definitively identify separable neural systems for dual-process modes of judgment. / text

Functional magnetic resonance imaging (fMRI) is a non-invasive technique that allows for visualization of active brain regions. Although white matter (WM) constitutes approximately 50% of brain tissue, fMRI activation in WM has conventionally been dismissed. There are two main reasons WM fMRI remains controversial: 1) the blood oxygen level dependent (BOLD) fMRI signal depends on cerebral blood flow and volume, which are lower in WM than gray matter and 2) fMRI signal has been associated with post-synaptic potentials as opposed to action potentials. Despite these observations, there is no direct evidence against measuring fMRI activation in WM. This thesis is comprised of four manuscripts that investigate fMRI activation in WM at 4T. The first study evaluated whether it was possible to detect WM activation using an interhemispheric transfer task and examined whether certain MRI contrast mechanisms were more sensitive to activation in WM. Activation was detected in the anterior corpus callosum at the individual and group level and we discovered that T2 weighted imaging may provide increased sensitivity to activation in WM. The second study used two established interhemispheric transfer tasks to examine whether callosal activation could be experimentally manipulated using a within subjects design. The results replicated previous findings and demonstrated an ability to map functional activation in the corpus callosum that was task dependent. The third study examined WM fMRI activation in a different structure and focused on the posterior limb of the internal capsule using a motor task; activation was elicited at both individual and group levels. The fourth study linked advances in the ability to detect WM fMRI activation to current clinical approaches to the assessment of WM dysfunction. An adapted Symbol Digit Modalities Test was used to evaluate WM activation in healthy controls. The results revealed individual level activation in both the corpus callosum and internal capsule. Taken together this stream of research represents a major advance in the methods used to non-invasively study brain function. Future applications may include improved assessment methods for patients with WM dysfunction.

Hypothalamic control of food intake may be overridden by cortical and limbic brain regions that process reward and the hedonic aspect of food, affecting the ability to discriminate between homeostatic and hedonic feeding. Women, in particular may be affected since cognition and perception of reward change during the menstrual cycle. Changes in estrogen and progesterone levels during the menstrual cycle induce changes in appetite and eating behavior. Food intake declines in the peri-ovulatory period when estrogen levels peak, but increases in the luteal phase when progesterone levels increase. In this novel study we introduce a different context in which to study appetite regulation; the menstrual cycle. The two main study objectives were: 1) to compare the BOLD response between the peri-ovulatory and luteal phases of the menstrual cycle and 2) to compare the BOLD response between women in a negative and positive affect state in response to visual food stimuli using functional magnetic resonance imaging. Pictures of food, regardless of their caloric content stimulated greater activation during the follicular phase compared to the luteal phase in the orbitofrontal cortex, fusiform, amygdala and inferior operculum. Activity was present in the hippocampus, ventral tegmental area and nucleus accumbens in response to high calorie images but not low calorie images during the follicular phase. The insula showed selective activity responding to high calorie pictures in the luteal phase and low calorie pictures in the follicular phase. High calorie food cues elicited greater BOLD signal for women reporting negative affect in the putamen, amygdala, pulvinar, prefrontal cortex, pallidum, fusiform and ventral tegmental area. In summary, visual food cues produced a more robust response during the follicular phase of the menstrual cycle and during a negative mood state in brain regions modulating the rewarding and motivational effects of food images. An increased understanding of how appetite-regulating brain regions respond during the menstrual cycle and in different mood states may facilitate the development of new therapies to reduce the incidence of obesity. / Thesis (Master, Physiology) -- Queen's University, 2009-09-25 15:35:15.609

Improving stroke recovery is a topic of considerable interest in the developed world. Motor deficits following stroke can significantly impact quality of life, and motor rehabilitation strategies are urgently needed to promote brain recovery. One technique that has had therapeutic success in other domains is neurofeedback (NF), a strategy whereby a person is trained to gain volitional control of their neurological activity. The NF technique has proven efficacious in disorders ranging from epilepsy to attention deficit disorders based on feedback of electroencephalography (EEG) signals, and the potential exists for NF applications in the recovery of motor function following stroke. Using functional magnetic resonance imaging (fMRI), NF can be applied to precisely defined regions of interest (ROIs), facilitating the targeted treatment of affected functional areas. The combination of fMRI and NF is still relatively new, and much work remains in the characterization and optimization of fMRI NF strategies. In a two-pronged approach, this thesis focuses on the application of ROI-based NF to the motor system using traditional fMRI measurements and also the development and analysis of acquisition strategies intended for use in ROI-based NF. First, a study of the mechanisms governing the successful application of NF in primary motor cortex ROIs is presented, using kinaesthetic motor imagery (imagining the sensation and execution of movement) to engage the motor system. Second, an investigation of fMRI signal contrast enhancement properties using multi-echo fMRI acquisition methods in dense sampling regimes is considered. Third, a novel acquisition method is introduced, designed using parallel MRI principles to provide fast and detailed sampling of fMRI signals in selected ROIs, called Constrained Source Space Imaging (CSSI). To conclude, the potential future directions for fMRI NF research and the CSSI technique are discussed, including thoughts toward the continued development of NF as a potential motor therapy for stroke patients.

Improving stroke recovery is a topic of considerable interest in the developed world. Motor deficits following stroke can significantly impact quality of life, and motor rehabilitation strategies are urgently needed to promote brain recovery. One technique that has had therapeutic success in other domains is neurofeedback (NF), a strategy whereby a person is trained to gain volitional control of their neurological activity. The NF technique has proven efficacious in disorders ranging from epilepsy to attention deficit disorders based on feedback of electroencephalography (EEG) signals, and the potential exists for NF applications in the recovery of motor function following stroke. Using functional magnetic resonance imaging (fMRI), NF can be applied to precisely defined regions of interest (ROIs), facilitating the targeted treatment of affected functional areas. The combination of fMRI and NF is still relatively new, and much work remains in the characterization and optimization of fMRI NF strategies. In a two-pronged approach, this thesis focuses on the application of ROI-based NF to the motor system using traditional fMRI measurements and also the development and analysis of acquisition strategies intended for use in ROI-based NF. First, a study of the mechanisms governing the successful application of NF in primary motor cortex ROIs is presented, using kinaesthetic motor imagery (imagining the sensation and execution of movement) to engage the motor system. Second, an investigation of fMRI signal contrast enhancement properties using multi-echo fMRI acquisition methods in dense sampling regimes is considered. Third, a novel acquisition method is introduced, designed using parallel MRI principles to provide fast and detailed sampling of fMRI signals in selected ROIs, called Constrained Source Space Imaging (CSSI). To conclude, the potential future directions for fMRI NF research and the CSSI technique are discussed, including thoughts toward the continued development of NF as a potential motor therapy for stroke patients.

The current study examined the relation of impulsivity and obesity in three neuroimaging studies using MRI techniques to test the hypothesis that deficits in brain regions responsible for inhibitory control are associated with obesity. The first study used voxel-based morphometry (VBM) to explore volumetric differences in lean, overweight, and obese women (N=83) and found that BMI was negatively correlated with grey matter (GM) in the insula, frontal operculum, and inferior frontal gyrus. BMI was positively correlated with white matter (WM) in the fusiform gyrus, parahippocampal gyrus, Rolandic operculum, and dorsal striatum. Genetic alleles for dopamine expression moderated these relations. Additionally, less GM in the superior frontal gyrus predicted future increases in BMI. The second study used VBM to examine differences between lean adolescents at risk versus not at risk for obesity (N=54). There were no regional GM or WM differences based on risk status. There were also no regional differences that predicted weight gain over 1-year follow-up. Additionally, genetic alleles for dopamine expression did not moderate any of these regions. These findings suggest that volumetric differences may emerge after excessive weight gain. Finally, the third study used a psychophysiological interaction analysis to test functional connectivity between prefrontal and limbic regions as a function of BMI in lean, overweight, and obese women (N=37) during a go/no-go task. There was no functional connectivity found in seed regions in relation to BMI. Implications for intervention and future research are discussed.

Previous fMRI studies have demonstrated that older adults who perform as well as young adults on certain cognitive tasks recruit additional brain regions relative to younger adults while performing these tasks. This phenomenon has been interpreted as a compensatory response and may reflect an effort to maintain performance in the face of increasing changes in cognitive difficulty or age-related brain changes in structure and/or function. Whether the compensatory response is specific to older adults or represents a more general response of any individual to increasing task difficulty is unclear. The present fMRI experiment explored age differences in brain activity associated with increases in task difficulty in two tasks, an episodic-retrieval task that is expected to be difficult for older compared to young adults, and a lexical-semantic task that is expected to be more difficult for young compared to older adults. In the lexical-semantic task, participants judged whether pairs of words were synonyms or antonyms. In the episodic task that followed, participants made yes/no memory judgments for the word pairs previously presented. Difficulty was manipulated using word frequency -low frequency words are more difficult in the lexical-semantic judgment task and easier in the episodic task. Young (ages 18-24) and older healthy adults (ages 60-83) were scanned on a 3T GE magnet using a single-shot spiral pulse sequence. Behavioral results showed a double dissociation – older adults were adversely affected by word frequency in the episodic but not the semantic task, while young adults were adversely affected by word frequency in the semantic but not the episodic task. Both groups showed activation in similar task-related and task-general regions regardless of difficulty level). Age-related differences were observed for task-specific and linear increases due to difficulty. Linear increases in fMRI activation were associated with younger adults showing increased task difficulty in bilateral task-related regions during the lexical semantic task, whereas in the episodic retrieval task only activating bilateral posterior cortices. As difficulty increased, older adults showed unilateral brain activations: left regions for the lexical-semantic task and medial and right hemisphere regions for the episodic retrieval task. Most importantly, difficulty load increases paralleled the groups' behavioral results: younger adults showed greater increases in activity in the lexical-semantic task compared to older adults, but not in the episodic retrieval task, whereas older adults showed the opposite pattern, with greater increases in activation only in the episodic task when compared to younger adults. Thus, younger and older adults recruit regions differently in response to increases in difficulty. Our results suggest that increases in fMRI activation as difficulty increases occur as an interaction to deal with task difficulty and the inherent abilities of the individuals, rather than occurring only in older adults, or in older adults across all tasks, regardless of their abilities in that domain.

Background: Alzheimer’s disease (AD) is a neurodegenerative disorder for which there is presently no cure. As a result, there is a critical need to improve upon early detection methods through the identification of ideally non-invasive biomarkers, such as functional magnetic resonance imaging (fMRI). Recently, novel approaches to the analysis of resting-state fMRI data have been developed that focus on the moment-to-moment variability in the blood oxygen level dependent (BOLD) signal. However, the findings on BOLD signal variability have thus far been equivocal, with some findings showing decreased BOLD variability with age and cognitive decline, and others suggesting that increased BOLD fluctuations may serve as a physiological signal reflecting underlying cerebrovascular challenges. Given the paucity of research in this area, the objective of the current study was to investigate BOLD variability as a novel early biomarker of AD and its associated psychophysiological correlates. Method: Neuroimaging and cognitive data were obtained from the Alzheimer's Disease Neuroimaging Initiative (ADNI) 2 database from 19 participants with AD (mean age = 72.7 ± 6.5) and 19 similarly-aged controls (mean age = 74.7 ± 6.9). All analysis steps were performed using tools within the Functional MRI of the Brain Software Library (FSL). For each participant, a map of BOLD signal variability (SDBOLD) was computed as the standard deviation of the BOLD timeseries at each voxel within both grey and white matter regions. Firstly, group comparisons were performed to examine global differences in resting state SDBOLD in AD versus healthy controls. Correlations were then examined between participant SDBOLD maps and (1) ADNI-derived composite scores of memory and executive function and (2) neuroimaging markers of cerebrovascular status (total white matter hyperintensity [WMH] burden, as computed from FLAIR scans). Results: Between-group comparisons revealed significant (p < 0.05) increases in SDBOLD in patients with AD relative to healthy controls in right-lateralized grey and white matter frontal regions, including the superior frontal and precentral gyri, and widespread regions of the corona radiata. Due to the novelty of the current study, secondary analyses investigating the association between SDBOLD and psychophysiological correlates were examined with a more liberal threshold (p < 0.1). Results revealed that lower memory scores were associated with greater SDBOLD in the medial temporal lobe and adjacent structures in the healthy control group. Conversely, higher total WMH burden was associated with greater SDBOLD in highly localized grey and white matter regions in the healthy control group. No association between SDBOLD and cognitive or cerebrovascular measures was identified in the AD group. Conclusion: The current study provides proof of concept that a novel resting state fMRI analysis technique that is non-invasive, easily accessible, and clinically compatible, can differentiate patients with AD from healthy controls. To further explore the potential of SDBOLD as a biomarker of AD, additional studies in larger, longitudinal samples are needed to better understand the changes in SDBOLD that characterize earlier stages of disease progression and their underlying psychophysiological correlates. / Graduate / 2018-08-21

The purpose of the present dissertation was to shed light on the neurophysiological effect of regular consumption of low amounts of alcohol on two important aspects of executive functions, cognitive interference and response inhibition, using functional magnetic resonance imaging (fMRI) in a sample of young adults. Participants were recruited from the Ottawa Prenatal Prospective Study (OPPS), a longitudinal study that has collected data from participants from infancy to young adulthood, which permitted control of a number of potentially confounding drug and lifestyle variables. This allowed for investigation of the unique effect of alcohol use on executive functions. The dissertation itself is comprised of two original manuscripts: the first study compared low-level alcohol users to controls on performance of the Counting Stroop, a task of cognitive interference; and the second study compared users to controls on performance of the Go/No-Go, a task of response inhibition.Although the results of both studies found no performance differences between groups, low-level alcohol users had significantly more brain activation in several regions, including areas not typically associated with task processing, compared to irregular or non-drinker controls. This difference in neurophysiology may be reflective of compensatory strategies within the brain, whereby the recruitment of additional regions may be attempting to compensate for potential underlying deficits that occur with increasing cognitive demand. While further research is needed to validate this hypothesis, the present findings highlight the vulnerability of the developing brain.

This thesis investigates the utility of using the Compound Remote Associate (CRA) problem, developed by Bowden and Jung-Beeman (2003), in investigating the neural correlates insight. It is uncertain to what extent CRA problems are insight problems. In Experiment 1, I performed a protocol analysis of people solving CRA problems and found that CRA problems can and should be used to investigate insight. However, certain considerations should be taken. Particularly, researchers should separate problems solved with insight when the solution is the first thing considered (immediate-insight) from problems solved with insight when the solution is obtained after at least some deliberation (delayed-insight). Parsing insight solutions into separate categories, I performed a functional Magnetic Resonance Imaging (fMRI) experiment. The results suggest a distinct difference in processing between delayed and immediate insight solutions. The results shed light into possible irregularities in prior studies and provide important considerations for future research on insight problem solving.