Building a Spiking Neural Network Model of the Basal Ganglia on SpiNNaker

We present a biologically-inspired and scalable model of the Basal Ganglia (BG) simulated on the SpiNNaker machine, a biologically-inspired low-power hardware platform allowing parallel, asynchronous computing. Our BG model consists of six cell populations, where the neuro-computational unit is a conductance-based Izhikevich spiking neuron; the number of neurons in each population is proportional to that reported in anatomical literature. This model is treated as a single-channel of action-selection in the BG, and is scaled-up to three channels with lateral cross-channel connections. When tested with two competing inputs, this three-channel model demonstrates action-selection behaviour. The SpiNNaker-based model is mapped exactly on to SpineML running on a conventional computer; both model responses show functional and qualitative similarity, thus validating the usability of SpiNNaker for simulating biologically-plausible networks. Furthermore, the SpiNNaker-based model simulates in real time for time-steps 1 ms; power dissipated during model execution is & #x2248;1.8 W

Layered control architectures in robots and vertebrates

We revieiv recent research in robotics, neuroscience, evolutionary neurobiology, and ethology with the aim of highlighting some points of agreement and convergence. Specifically, we com pare Brooks' (1986) subsumption architecture for robot control with research in neuroscience demonstrating layered control systems in vertebrate brains, and with research in ethology that emphasizes the decomposition of control into multiple, intertwined behavior systems. From this perspective we then describe interesting parallels between the subsumption architecture and the natural layered behavior system that determines defense reactions in the rat. We then consider the action selection problem for robots and vertebrates and argue that, in addition to subsumption- like conflict resolution mechanisms, the vertebrate nervous system employs specialized selection mechanisms located in a group of central brain structures termed the basal ganglia. We suggest that similar specialized switching mechanisms might be employed in layered robot control archi tectures to provide effective and flexible action selection

A review of symptomatic leg length inequality following total hip arthroplasty

Leg length inequality (LLI) following total hip replacement is a complication which features increasingly in the recent literature. The definition of LLI is complicated by lack of consensus regarding radiological measurement, clinical measurement and the incomplete relationship between LLI and associated symptoms. This paper reviews 79 reports relating to LLI post hip replacement, detailing definitions and classification and highlighting patient populations prone to symptomatic LLI. While there is no universal definition of LLI, there is a broad consensus that less than 10 mm of difference on AP view plain radiographs is clinically acceptable. There are few techniques described that consistently produce a postoperative LLI of less than this magnitude. Where postoperative LLI exists, lengthening appears to cause more problems than shortening. In cases of mild LLI, non-surgical management produces adequate outcomes in the majority of cases, with functional LLI cases doing better than those with true LLI. Operative correction is effective in half of cases, even where nerve palsy is present, and remains an important option of last resort. Poor outcomes in patients with LLI may be minimised if individuals at risk are identified and counselled appropriately

Detraining from total body exercise ergometry in individuals with spinal cord injury

This study was designed to investigate the effects of detraining that occurred during an 8 week period of muscular inactivity following a 12 week training program of artificial computerized functional electrical stimulation cycle ergometry (CFES LE) and arm ergometry. Six spinal cord injured male individuals were followed through an 8 week detraining period that was preceded by a 12 week exercise program including CFES LE and arm ergometry. Maximal graded exercise tests were completed and measurements of peak oxygen consumption (VO2), heart rate (HR), ventilation (V(E)) workload, and creatine kinase were taken. Testing occurred at initial training (OT), after 12 weeks of training (12T), and after 8 weeks of detraining (DT). After the training program, peak VO2 increased significantly from 0.562 ± 0.126 (OT) to 1.021 ± 0.247 l/min (12T, P 2 decreased to 0.791 ≠ 0.216 l/min, which was lower than 12T (P 2 and HR with workload, which were retained after DT. These increases did not reach statistical significance, however. No apparent relationship existed between these values at baseline. There were no significant differences in submaximal or peak HR of V(E) between the three testing periods. The results indicate that both peripheral muscular adaptations and central distribution adaptations in SCI individuals are partially maintained following 8 weeks of DT from CFES LE and arm ergometry