Deep brain stimulation (DBS) is a methodology wherein therapeutic electrodes are implanted within the brain to deliver timed impulses to desired nerve centers, and can be used to treat a variety of disorders, in particular movement disorders such as Parkinson's disease and dystonia. A major challenge with DBS relates to determination of where to place therapeutic electrodes: while medical imaging (e.g., magnetic resonance imaging) can provide a starting point for identification of placement locations, since the therapeutic electrodes must be precisely placed (e.g., in those regions of the brain giving rise to muscle tremors), it is necessary to obtain a more detailed map of brain structures. A common technique is to advance a needle-like probe (or multiple such probes) into the brain, with each probe bearing one or more reading microelectrodes. The reading microelectrodes measure neuronal activity, as indicated by extracellular action potentials, which are in essence voltage spikes caused by neuronal firings. As readings are taken, the patient—who is generally awake during the procedure—may be requested to perform some action (e.g., move an arm or leg), thereby provoking neuronal firings. By looking at the location of the probe (i.e., probe location and depth) and the characteristics of the measured neuronal spikes (e.g., shape, frequency, etc.), the regions of the brain traversed by the probe can be mapped: spike characteristics can be correlated with those known to exist in certain portions of the brain, changes in spike characteristics can indicate interfaces between different regions of the brain, and so forth. Additionally, stimulating input (voltage) pulses can simultaneously be delivered to regions of the brain which are candidates for electrode implantation to determine their physiological effect (e.g., whether tremors are reduced, whether the patient experiences some change in feeling, etc.), with such stimulating input pulses being delivered via an input point on the probe or via a separate electrode spaced from the probe. Once the map of the brain is generated and candidate locations for implantation of therapeutic electrodes are identified, therapeutic electrodes may be permanently implanted, with the therapeutic electrodes being connected to a power supply which delivers an input signal suitable to reduce or eliminate tremors, or to attain some other desired effect.
However, the process of mapping the brain can be a difficult one. It can be extremely difficult to discern neuronal spikes from background noise (and from any stimulating input pulses) within these data, particularly owing to the wide variety of characteristics neuronal spikes may have; spikes can vary widely in their shape, amplitude, period, frequency, and so forth. The same neuron can even generate different spike readings over time, both owing to variability in the neuron itself and owing to factors such as nearby pulsing blood vessels creating small changes in neuron-to-probe spacing. Experienced neurologists and others can over time gain skill in identifying the neuronal spikes of individual neurons from probe readings, but since probes may contain large arrays of reading microelectrodes, thereby generating multiple streams of reading data, it is virtually impossible for human operators to successfully process all of the generated data. It would therefore be useful to have improved methods available for identifying neuronal spikes, in particular methods which require minimal human review and supervision, and which might therefore be suitable for use in expert systems and other automated or semi-automated systems for probe data review.