http://hdl.handle.net/1974/803 Thu, 20 Jun 2013 05:12:20 GMT 2013-06-20T05:12:20Z http://hdl.handle.net/1974/8083 Title: EFFECTS OF MUSIC ON THE PAIN RESPONSE IN THE CENTRAL NERVOUS SYSTEM USING FUNCTIONAL MAGNETIC RESONANCE IMAGING Authors: Dobek, CHRISTINE ELIZABETH Abstract: The oldest procedure for pain relief has been music. There is abundant behavioural evidence to support music’s pain relieving properties, however, studies to date have yet to investigate music-induced analgesia via imaging. Our first imaging study used thermal stimulation just below pain threshold in combination with various music stimuli, to determine whether music can affect neural activity in response to heat stimuli within brainstem and spinal cord regions. Differential responses to music stimuli were found within regions known for descending modulation, and familiar classical music had a unique effect on neural activity in these regions compared to unpleasant music, reverse music, and no music. This study confirmed that the emotional valence of music affects neural activity in the brainstem and spinal cord. The second study used a well-defined pain paradigm applied with or without favorite music to study the neural activity responses in the brain, brainstem, and spinal cord using imaging. Subjective pain ratings were significantly lower when painful stimuli were administered with music than without music. The pain condition alone elicited neural activity in brain regions consistently activated during similar pain studies. Brain regions associated with pleasurable music listening were activated including limbic, frontal, and auditory regions when comparing music to non-music pain conditions. In addition, neural regions showed activity responses indicative of descending modulation when contrasting the two conditions. These regions include the spinothalamic tract, dorsolateral prefrontal cortex (DLPFC), periaqueductal grey (PAG), rostral ventromedial medulla (RVM), and the dorsal gray matter of the spinal cord. The data suggest that music seems to engage mesolimbic and mesocortical brain regions to activate the descending pain modulation pathway. Lower subjective pain ratings corresponded to a greater suppression in the dorsal gray matter when listening to music. This is the first imaging study to characterize the neural response of pain and how it is mitigated by music listening, and brain and spinal fMRI are appropriate means to study pain processing and its modulation in the central nervous system. Description: Thesis (Master, Neuroscience Studies) -- Queen's University, 2013-06-18 11:33:32.818 Tue, 18 Jun 2013 04:00:00 GMT http://hdl.handle.net/1974/8083 2013-06-18T04:00:00Z http://hdl.handle.net/1974/8032 Title: A study of predicitive capacity and working memory in mild Alzheimer's disease and normal controls using saccadic eye movements Authors: Ruthirakuhan, MYURI Abstract: Alzheimer’s disease (AD) is a neurodegenerative disorder with no existing cure. Since cognitive control influences saccade behaviour, saccades provide a valuable tool when studying cognitive changes in healthy and pathological aging. This thesis aims to evaluate differences in predictive capacity and working memory between cognitively normal older adults (NC) and mild AD patients using customized saccade paradigms and a battery of neuropsychological tests. In the predictive paradigm, we hypothesize that AD participants would display a decreased level of prediction, predictive capacity and learning capacity. In the memory-guided paradigm, we hypothesize that AD participants would have a decreased ability to maintain fixation and capacity to retain information and reproduce it correctly. Overall, we found that in the predictive paradigm, NC displayed a greater degree of prediction than AD participants. However, both groups had an optimal level of prediction at intermediate inter-stimulus intervals (ISI) (750 and 1000 ms). As ISI increased, both groups, although more so in AD, elicited a greater proportion of SRTs below -200 ms and -400 ms. This may suggest that as ISI increased, participants switched from a predictive to an anticipatory/guessing strategy. At an ISI of 500 ms, NC’s learning capacity was greater than AD participants. Cognitive scores of neuropsychological tests did not correlate with learning capacity in NC. However, learning capacity in AD participants was positively correlated with working memory capacity and attentional control. The memory-guided paradigm revealed AD participants completed less viable trials, less correct trials, and had more combined directional and timing errors than NC. Cognitive correlations showed that NC’s working memory capacity positively correlated with the frequency of correct trials, whilst negatively correlating with saccade errors. Since AD participants completed 10% of viable trials correctly, the task may have been too difficult for AD participants to comprehend, rendering correlations invalid. These findings suggest that although the predictive paradigm does not solely assess for prediction, it may provide a measure to cognitively differentiate NC from AD patients, and detect AD severity. Since the memory-guided paradigm may be too difficult for AD participants, it may provide a better indicator of cognitive changes associated with healthy aging. Description: Thesis (Master, Neuroscience Studies) -- Queen's University, 2013-05-21 18:54:19.492 Wed, 22 May 2013 04:00:00 GMT http://hdl.handle.net/1974/8032 2013-05-22T04:00:00Z http://hdl.handle.net/1974/7802 Title: RAPID ADAPTATION OF REACTIVE FORCE CONTROL WHEN LIFTING OBJECTS Authors: Markovik, SIMONA Abstract: The control of object manipulation tasks involves the close interplay of predictive and reactive control mechanisms. For example, when lifting an object, people typically predict the weight based on object size and material as well as sensorimotor memory obtained from previous lifts of the object. When lifting objects with a precision grip, people increase vertical load force to a target level that slightly exceeds the predicted weight. When the object is heavier than expected, the mismatch between expected and actual tactile signals associated with lift-off triggers a corrective action within ~100 ms, that involves probing increases in load force that continue until the object is lifted. Here we investigated whether this correction action can be adaptively influenced by experience. Participants repeatedly lifted an object that was instrumented with force sensors to measure the forces applied by the fingertips, with weight that could be varied without the knowledge of the participant. In 80% of trials, the weight was set to 2 N and, in different blocks of 110 trials, the remaining 20 % of trials (2 trials randomly selected from each successive 10 trials) was set to either 4 or 6 N. We found that the rate of change of the reflexively triggered increase in load force that occurred in the 4 or 6 N trials, scaled with the additional weight. That is, following the initial increase in load force to ~2 N, the subsequent increase in load force was more rapid for the 6 N object than the 4 N object. In contrast, the onset time of the reactive increase in load force was independent of the additional weight. Finally, this adaptation of reactive load force control took place quickly and was evident after only a few lifts of the heavier weight. These results indicate that the reactive increases in load force that occur when a lifted object is heavier than expected can be adapted and tuned, to refine behavior. This further suggests that multiple predictions can be generated about object weight when lifting. Description: Thesis (Master, Neuroscience Studies) -- Queen's University, 2013-02-02 13:34:20.533 Mon, 04 Feb 2013 05:00:00 GMT http://hdl.handle.net/1974/7802 2013-02-04T05:00:00Z http://hdl.handle.net/1974/7626 Title: RODENT MODELS OF SCHIZOPHRENIA-LIKE SYMPTOMS INCREASE POLYDIPSIA Authors: Hawken, EMILY Abstract: Primary polydipsia, excessive drinking without known medical cause, continues to occur with a significant prevalence in psychiatric populations. While the etiology of polydipsia remains unknown, the fact that it is significantly associated with a diagnosis of schizophrenia has led some to postulate that the two may share common neurological pathophysiologies. Animal models of schizophrenia-like symptoms have focused on modeling the core behavioral and neurochemical features of the illness, like cognitive deficits and enhanced dopamine transmission. Here, we used three well-established models, including repeated amphetamine treatment, subchronic MK-801 (an N-methyl-D-aspartate [NMDA]-receptor antagonist), and post-weaning social isolation. We also examined a “double-hit” model, combining NMDA-receptor antagonism and social isolation. We paired these models to test the hypothesis that drinking will be enhanced in a paradigm of excessive drinking in the rat. In rodents, non-physiologic drinking can be induced by intermittent presentation of food (e.g., one sugar-pellet a minute) in the presence of a drinking spout to a hungry animal, termed schedule-induced polydipsia (SIP). Animals pretreated with pharmacological or non-pharmacological models of schizophrenia-like symptoms showed significantly increased SIP, The “double hit” model did not further increase drinking above that of either social isolation or MK-801 treatment alone. A moderate amount of spontaneous polydipsia in the homecage of MK-801-treated rats was also observed and resulted in one death secondary to excessive drinking, a phenomenon also found in inpatients with schizophrenia. Following repeated treatment with AMPH, there was some evidence that over time, animals learned to drink increased amounts independently of the scheduled food presentation. This evidence suggests that the excessive drinking behavior observed in polydipsia associated with schizophrenia may have a learned component. In summary, animal models of schizophrenia-like symptoms augmented SIP behavior, showing that polydipsia associated with schizophrenia may be modeled in rodents. As each model has been shown to modify dopamine transmission to some degree, the evidence suggests augmented SIP may reflect changes in dopamine transmission and dopamine may be the common link between polydipsia and schizophrenia. Further research is necessary to fully elucidate the mechanisms underlying SIP, polydipsia and schizophrenia. Description: Thesis (Ph.D, Neuroscience Studies) -- Queen's University, 2012-10-31 17:43:18.34 Wed, 31 Oct 2012 04:00:00 GMT http://hdl.handle.net/1974/7626 2012-10-31T04:00:00Z