Functional connectivity in auditory cortex using chronic, multichannel unit recordings.
ABSTRACT Chronic, multichannel recordings provide a method for reliable detection and determination of long-term dynamic functional connectivity. Using chronically implanted multichannel electrode arrays, we simultaneously recorded 30–70 units in guinea pig auditory cortex in daily recording sessions for implant durations of six months. We examined stimulus response properties and correlation strengths in neuron pairs in four animals. Preliminary results from these `snapshots’ of functional connectivity suggest sparse functional connections among widely distributed neurons. Some of these functional connections were found to persist for several days. These results provide a framework upon which further investigations of functional dynamic connectivity can be developed.
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ABSTRACT: A new method for encoding speech signals in automatic voice recognition is proposed. To represent speech signals with minimum redundancy we use independent component analysis to adapt features (basis functions) that efficiently encode the speech signals. The learned basis functions are localized in time and frequency and resemble Gabor-like filters. In encoding the speech signals, the ICA features capture the statistical essence of speech signals with fewer basis functions than traditional methods such as Gabor filters and the Fourier basis. A speech recognizer can be trained based on those features and the recognition rate is improved and better than the recognition rates obtained by the conventional mel-frequency cepstral features. Our results suggest that the obtained higher-order structure of speech signals plays an important role in efficient speech coding. Index Terms Gabor filter, independent component analysis, speech signal processing, feature extraction. I. Introd...Neural Processing Letters 01/2002; 15:235-245. · 1.24 Impact Factor
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ABSTRACT: The Korean Brain Neuroinformatics Research Program has dual goals, i.e., to understand the information processing mechanism in the brain and to develop intelligent machine based on the mechanism. The basic form of the intelligent machine is called Artificial Brain, which is capable of conducting essential human functions such as vision, auditory, inference, and emergent behavior. By the proactive learning from human and environments the Artificial Brain may develop oneself to become more sophisticated entity. The OfficeMate will be the first demonstration of these intelligent entities, and will help human workers at offices for scheduling, telephone reception, document preparation, etc. The research scopes for the Artificial Brain and OfficeMate are presented with some recent results.05/2007: pages 123-143;
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ABSTRACT: This paper describes a detailed protocol for obtaining chronic, multi-site unit recordings in cerebral cortex of awake animals for periods of three months or more. The protocol includes details for making relatively simple and inexpensive implantable multichannel electrodes that consist of arrays of separate microwires. The results reported in this paper suggest that a viable implant will have discriminable unit activity on about 80% of the electrodes, resulting in, on average, the simultaneous unit recording of upwards of 60 units during a daily recording session. The active electrodes during one recording session tend to remain active in subsequent recording sessions for several weeks. Using the methods described here, implants have been constructed which incorporate several different electrode materials, coatings, sizes, and electrode separation within a single array. These microwire electrode arrays provide the basic technology for obtaining unit recordings for several months. This provides a model system for studying biocompatibility of neural implants, which is a critical component for the development of neural implants that have an indefinite working span.Themes: Sensory SystemsTopics: Auditory systems: central physiologyBrain Research Protocols 01/2000; · 1.82 Impact Factor