Anorexia Nervosa (AN) has the highest mortality rate of any psychiatric condition, and despite its recognition for centuries, remains a significant treatment challenge. Marked by firmly entrenched maladaptive beliefs about body, weight and food, as well as high rates of psychiatric comorbidity, AN is a chronic illness in a large proportion of patients. The neural substrates of AN are now beginning to emerge, and appear to be related to dysfunctional, primarily limbic, circuits driving pathological thoughts and behaviours. Deep Brain Stimulation (DBS) is a neurosurgical procedure where implanted electrodes are used to regulate activity in critical nodes comprising such aberrant circuits. The promise of DBS in motor-circuit conditions, such as Parkinson’s Disease, has driven it’s investigation in other circuit-based disorders, including some psychiatric conditions. Converging evidence from clinical and imaging literatures suggests that AN is in large part a disorder of emotional processing, wherein disordered mood, anxiety, and affective dysregulation contribute to disease maintenance and are obstacles to effective treatment. The subcallosal cingulate (SCC), a key medial frontal structure involved in affective processing, has further been directly implicated in AN relevant pathways. As such, this work had three broad objectives: i) to establish the safety and initial efficacy of SCC DBS in a group of chronic and highly-refractory AN patients; ii) to show that SCC DBS can have network wide cerebral metabolic influence, on AN-relevant circuits and structures; and, iii) to investigate whether structural brain features, including hippocampal volume changes, are correlated with clinical outcomes of DBS. Our results showed that DBS is safe in AN, and associated in some patients with significant improvements in mood, anxiety and, over time, weight and treatment-response. Imaging results further showed DBS to be associated with substantial changes in glucose utilization in disease-relevant circuits, with preliminary evidence supporting a relationship between hippocampal volume changes and clinical improvements. In the context of highly refractory disease, these promising results suggest that DBS can inform AN circuit models, and be explored as a novel therapeutic option for treatment-resistant patients.

This research examines the summation characteristics of the neural network subserving self-stimulation reward. The data show that the neural network has two integrators that sum the signals produced by brain stimulation. The time constant of the first integrator is approximately 450 msec, whereas that of the second integrator is approximately 6.5 sec. Furthermore, these integrators are sensitive to the spatiotemporal arrival of the signals. / When prolonged stimulation is delivered at a high pulse frequency, the initial pulses contribute the most to the rewarding effect. Later pulses are affected by the reduced ability of the neurons or synapses to transmit signals along the neural network due to fatigue. / A fatigue effect may be dissipated by splitting a pulse train into two parts by an interval of no stimulation. This should increase the rewarding effectiveness of the pulse train. However, the rewarding effectiveness is dependent upon the duration of the interval of no stimulation and the magnitude of the two pulse-train halves. A long interval of no stimulation combined with a low stimulation magnitude may cause a frustration response and a decay in memory of the associations between the response, first pulse-train half, and second pulse-train half. These would make the rewarding effectiveness of the two pulse-train halves lower than that of a continuous pulse train. / Previous models of summation are unable to predict the present results. The data are explained in terms of a newly developed model of summation involving two central integrators and fatigue.

Functional electrical stimulation (FES) systems have been developed to help restore various neuromuscular functions in individuals with neurological disorders leading to paralysis. Most of the current FES systems are designed for specific neuroprosthesis applications (i.e., walking, grasping, bladder voiding, coughing, etc.) and when one intends to use them in other custom made applications they are very limited due to a lack of functionality and flexibility in hardware and programmability. This prevents effective and efficient development of customized neuroprostheses. Research and development efforts at the Rehabilitation Engineering Laboratory at the University of Toronto were being carried out with an objective to produce a new, fully programmable and portable FES system. This thesis presents a novel proof-of-concept prototype controller for use in the new FES system. The controller subsystem manages and controls the overall FES system including the real-time decoding and execution of stimulation, data acquisition, external systems interfaces and user interface.

Recovery of the ability to maintain balance during standing is one of the primary and essential goals of rehabilitation programs for individuals with Spinal Cord Injury (SCI). Regaining functionality during standing by means of a neuroprosthesis would decrease secondary complications and increase independence, and would consequently improve the quality of life of these individuals. However, the development of a standing neuro- prosthesis requires techniques to generate reliable and predictable torque vectors in the lower limbs. We proposed and tested a method based on surface Functional Electrical Stimulation (FES) and the idea that three independent muscles can form a basis that would span the joint torque vector space. We tested the proposed stimulation technique on the quadriceps muscles that produce knee extension. The results of this study suggest that the quadriceps muscle basis vectors are insufficient to cover the knee joint vector space.

Vagus nerve stimulation (VNS) is an approved therapy for patients suffering from refractory epilepsy. While VNS is currently an open loop system, making the system closed loop can improve the therapeutic efficacy. Electrical recording of peripheral nerve activity using a nerve cuff electrode is a potential long-term solution for implementing a closed-loop controlled VNS system. However, the clinical utility of this approach is significantly limited by various factors, such as poor signal-to-noise ratio (SNR) of the recorded electroneurogram (ENG). In this study, we investigated the effects of (1) modifying the electrode contact dimensions, (2) implementing an external shielding layer on the nerve cuff electrode and (3) exploring shielded bipolar nerve cuff designs on the recorded ENG. Findings from both computer simulations and animal experiments suggest that significant improvements in peripheral nerve recordings can be achieved.

This work proposes to survey new chemical knowledge, developed since 1984, on fluid additives used in matrix stimulation treatments of carbonate and sandstone petroleum reservoirs and describes one method of organizing this new knowledge in a software program using the Visual Basic for Applications programming language. While matrix stimulation treatments have been used in the petroleum industry for over 100 years, the last major review of the technical literature addressing this process occurred in 1984. Currently though, the petroleum industry better understands formation damage; uses different and more chemical additives in matrix stimulation treatments; and understands how some additives interact with one another affecting well performance. As a result, a new and thorough review of the literature regarding chemical additive choices for matrix stimulation treatments will help practicing engineers achieve better results worldwide. Moreover, organizing this chemical knowledge in a software program using VBA allows an engineer to access the information through Microsoft's widely available spreadsheet program, Microsoft Excel.

The upper extremity is often left with permanent disability following stroke and therapeutic techniques used at present have had limited success. This prospective clinical trial evaluated the effectiveness of mental practice (MP) through motor imagery (MI) a therapy technique to enhance upper extremity motor recovery after stroke. MI ability, upper extremity hand function, finger strength, and motor cortical output were examined in 18 stroke subjects (mean 67.5 years). Subjects were randomly allocated to the MP treatment group or the control group which received cognitive therapy. Both groups received their respective treatment daily for 30 minutes for a 3 week period. Assessments were performed prior to treatment, post treatment and at 3 months post treatment. Imagery ability was measured using the Kinesthetic and Visual Imagery Questionnaire (KVIQ) and mental chronometric testing. Hand function was assessed with the box and block test (BBT) and finger strength with maximum voluntary contraction (MVC). To determine the effect of MI on neural excitability, focal transcranial magnetic stimulation was applied over the primary motor cortex while participants were at rest and while they imagined themselves performing abduction of the index finger. Motor evoked potentials were recorded from the contralateral first dorsal interosseous (FDI), abductor digiti minimi (ADM) and abductor pollicis brevis (APB) muscles. Data were analyzed using multifactor and repeated measures ANOVAs with the significance level set to p < 0.05. Results showed no significant difference between groups on any of the outcome measures (p > 0.05) although all subjects improved their hand function over the study period (p < 0.05). In addition, motor threshold was found to decrease over time (p < 0.001) in all subjects demonstrating improvement in cortical motor excitability and output. Motor evoked potentials (MEPs) elicited during MI were significantly larger compared to those evoked at rest (p < 0.022). MEP amplitudes from FDI, the muscle targeted with MP, showed a significant interaction effect between time and group (p = 0.021) which reflected an increase in MEPs in the MP group over time whereas a decline occurred in the cognitive group. These findings indicate that MI enhances motor cortical output in stroke and that MP using MI appears to increase corticospinal output to the target FDI muscle. No differential effects of MP and cognitive therapy interventions were evident in terms of hand function and finger muscle strength. / Thesis (Master, Rehabilitation Science) -- Queen's University, 2008-04-25 16:23:51.775 / Heart and Stroke Foundation

No description available.

The phenomenon of self-stimulation has been used to map the neural circuitry of reinforcement and determine its neurophysiological and neurochemical characteristics. More recently, it has been proposed that drugs of abuse control behavior by their effects on the same neural systems. However, drug effects rise and fall over minutes or hours while conventional brain stimulation trains have abrupt onset and offset and last less than one second. Possibly because of this, the pattern of responding produced by drug reinforcers is different from the pattern produced by conventional brain stimulation. Furthermore, pharmacological antagonists of drug reinforcement increase the rate of drug self-administration while antagonists of brain stimulation reinforcement depress self-stimulation. To test the hypothesis that the differences in the characteristics of brain stimulation and drugs as reinforcers are due to differences in the kinetics of drugs and brain stimulation, we have modelled drug kinetics with frequency modulated brain stimulation trains. It is reported that animals will self-administer such brain stimulation and that, under these conditions, dopamine antagonists can induce an increase in the rate of self-administration.

Parkinson’s disease (PD) is a neurodegenerative movement disorder and a leading cause of neurological disability in the older adult population. Historically, the research and treatment of PD has focused on the associated motor symptoms. Now the non-motor symptoms such as sleep disturbance are becoming an increased focus for researchers. Deep brain stimulation (DBS) is a surgical intervention that has proven to be beneficial for PD motor symptom management. There are claims from the literature that DBS may assist with the phenomenon of sleep disturbance. A case study analysis was done to explore this concept in the DBS-PD patient population using the framework of the Symptom Management Theory. From the analysis of the subjective and objective data gathered it is clear that the phenomenon of sleep disturbance in this population is multifaceted and that DBS may play a role in managing the phenomenon of sleep disturbance for this population.