One and done. The use of biometrics and authentication technologies can help healthcare organizations reduce workflow costs while safeguarding access to patient data.
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Authorship↗
Biomedical subjects
M Kuperstein
Publications and source records attributed to M Kuperstein.
Neural model of adaptive hand-eye coordination for single postures.
A neural network model has been developed that achieves adaptive visual-motor coordination of a multijoint arm, without a teacher. The model learns to position an arm so that it reaches a cylinder arbitrarily positioned in space. The model uses a new neural architecture and a new algorithm for modifying neural-connection strengths. Computer simulations show that the model performs with an average position error of 4% of the arm's length and with an average orientation error of 4 degrees. The model is designed to be generalized for coordinating any number of topographic sensory inputs with limbs of any number of joints.
Humans↗
An adaptive neural model for mapping invariant target position.
We perceive a constant target in space as constant even though the registration of that target on our senses is continuously shifting. This article derives and stimulates a neural network model that represents visual spot targets, invariant with respect to any combination of egocentric target measures. The model represents space in terms of signals used to move in that space. The model learns and maintains precise sensory-motor calibrations starting with only loosely defined relations. It is adaptive to physical changes of the eye and muscles as well as internal system parameters. Its performance is noise and fault tolerant. Computer simulations show that the average error in target orientation after learning is about 1% of the total visual field extent. The model maintains good accuracy with many different parameter choices. Its performance is most related to the function of the posterior parietal cortex. Testable predictions are made for the columnar topography and learning in that brain structure.
Animals↗
Cue-sampling and goal-approach correlates of hippocampal unit activity in rats performing an odor-discrimination task.
Several techniques previously used to describe behavioral correlates of hippocampal unit and slow-wave activity are combined in a single odor-discrimination paradigm. Rats repetitively performed a sequence of behaviors during each trial: approach to a stimulus-sampling port, investigatory sniffing of the odor cue, orientation and approach toward a separate reward location, and water reward consumption. In a series of post hoc analyses, spike activity was time-locked to variations of each task event to uncover behavioral and physiological parameters that best synchronized unit firing. Three major categories of cells were identified: (1) "Cue-sampling" cells fired after onset of odor-cue sampling. Response magnitude was related to cue valence on both the current and past trials. (2) "Goal-approach" cells fired prior to arrival at either the odor-sampling port or reward cup. A number of sampling and approach cells also had place correlates. However, detailed analyses indicated that specific behaviors associated with increased firing reliably occurred at the same place. Unit activity was at least as well described by behavioral as spatial parameters. (3) "Theta" cells fired at high rates in strict relation to the ongoing limbic theta rhythm. This categorization suggests a functional organization of the hippocampus in which different cell types play complementary roles. Cue-sampling cells activated by discriminative stimuli during attentive fixations may be involved in comparing relative cue valence. Goal-approach cells may be involved in orientation movements for successive cue-sampling periods. Theta cells may provide synchronization of sensory acquisition during sampling, as well as in orientation movements during approach.
Animals↗
Neural group properties in the rat hippocampus during the theta rhythm.
The ensemble properties of unit activity in the rat hippocampus were studied during different behavioral states defined by the presence or absence of the theta rhythm. A 24-channel microelectrode was used to monitor the parallel activity of several single neurons simultaneously. Individual units were characterized by waveform, firing repertoire and firing relation to theta phase. Group patterns were characterized by multiple cross-correlations at different temporal resolutions during the presence and absence of the theta rhythm. Coactivation of units was frequently observed at a fine temporal resolution under both theta and non-theta states. In addition rhythmic synchronization of units was observed at a broader temporal resolution and was selective to the theta state. The combined findings suggest that the theta rhythm signifies a powerful patterning of group activity imposed upon a fixed connectivity of neighboring neurons.
Animals↗
Unit activity, evoked potentials and slow waves in the rat hippocampus and olfactory bulb recorded with a 24-channel microelectrode.
Activity from a number of neighboring neurons can be recorded simultaneously with multichannel microelectrodes. A new version of a 24-channel microelectrode system has been fabricated and used to record different types of neurophysiological data in the rat brain. The system called PRONG (Parallel Recording Of Neural Groups) includes a microelectrode, a lightweight reusable connector, a 24-channel FET-hybrid preamplifier, a 3-band 24-channel amplifier, a 24-channel spike monitor, high-speed digital and analog interfaces and a computer. The electrode-recording locations are arranged in 2 arrays of 12 sites. The arrays are spaced 100 micron apart along either edge of the recording section and the sites within each array are spaced 120 micron apart. The electrodes are fabricated using photolithography in patterned layers totaling 17 micron thick and 114 micron wide in the recording section. The recording sites are 20 micron2 and are plated with platinum black. Performance of the PRONG was compared with that of conventional single microelectrodes and with results in the literature on three kinds of extracellular activity in the rat hippocampal formation and olfactory bulb: action potentials, evoked field potentials and slow-wave activity. The selectivity and sensitivity of the PRONG compared favorably with characteristics of conventional electrodes. Background noise averaged 15 microV and no signal cross talk was observed between neighboring channels. Discriminable action potentials (signal-to-noise ratios of 2:1 to 15:1) were observed at 37-95% of the viable recording sites with a maximum of 19 units in one recording. Units were observed in waking animals for up to 4 days. The waveforms, firing repertoires and laminar distribution of units were the same as those recorded with conventional microelectrodes. This indicates that penetration by the PRONG spares tissue from functional damage. "Instant" laminar profiles were created for commissural and perforant path evoked potentials in the hippocampal formation. These profiles were nearly identical with those created by successive recordings made with conventional microelectrodes. Laminar profiles and behavioral activity appeared to be "normal" as collected with this electrode. These results set the foundation for use of the PRONG as a tool for the study of local neural interactions.
Animals↗
A practical 24 channel microelectrode for neural recording in vivo.
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Animals↗