Open Access. Powered by Scholars. Published by Universities.®

Life Sciences Commons

Open Access. Powered by Scholars. Published by Universities.®

Articles 1 - 7 of 7

Full-Text Articles in Life Sciences

Clustering Neural Spike Trains With Transient Responses, John D. Hunter, Jianhong Wu, John Milton Dec 2008

Clustering Neural Spike Trains With Transient Responses, John D. Hunter, Jianhong Wu, John Milton

WM Keck Science Faculty Papers

The detection of transient responses, i.e. nonstationarities, that arise in a varying and small fraction of the total number of neural spike trains recorded from chronically implanted multielectrode grids becomes increasingly difficult as the number of electrodes grows. This paper presents a novel application of an unsupervised neural network for clustering neural spike trains with transient responses. This network is constructed by incorporating projective clustering into an adaptive resonance type neural network (ART) architecture resulting in a PART neural network. Since comparisons are made between inputs and learned patterns using only a subset of the total number of available dimensions, …


Human Stick Balancing: Tuning Lèvy Flights To Improve Balance Control, Juan Luis Cabrera, John Milton Sep 2004

Human Stick Balancing: Tuning Lèvy Flights To Improve Balance Control, Juan Luis Cabrera, John Milton

WM Keck Science Faculty Papers

State-dependent, or parametric, noise is an essential component of the neural control mechanism for stick balancing at the fingertip. High-speed motion analysis in three dimensions demonstrates that the controlling movements made by the fingertip during stick balancing can be described by a Lévy flight. The Lévy index, , is approximately 0.9; a value close to optimal for a random search. With increased skill, the index does not change. However, the tails of the Lévy distribution become broader. These observations suggest a Lévy flight that is truncated by the properties of the nervous and musculoskeletal system; the truncation decreasing as skill …


Synaptic Transformations Underlying Highly Selective Auditory Representations Of Learned Birdsong, Melissa J. Coleman, Richard Mooney Aug 2004

Synaptic Transformations Underlying Highly Selective Auditory Representations Of Learned Birdsong, Melissa J. Coleman, Richard Mooney

WM Keck Science Faculty Papers

Stimulus-specific neuronal responses are a striking characteristic of several sensory systems, although the synaptic mechanisms underlying their generation are not well understood. The songbird nucleus HVC (used here as a proper name) contains projection neurons (PNs) that fire temporally sparse bursts of action potentials to playback of the bird's own song (BOS) but are essentially silent when presented with other acoustical stimuli. To understand how such remarkable stimulus specificity emerges, it is necessary to compare the auditory-evoked responsiveness of the afferents of HVC with synaptic responses in identified HVC neurons. We found that inactivating the interfacial nucleus of the nidopallium …


Synaptic Heterogeneity And Stimulus-Induced Modulation Of Depression In Central Synapses, John D. Hunter, John Milton Aug 2001

Synaptic Heterogeneity And Stimulus-Induced Modulation Of Depression In Central Synapses, John D. Hunter, John Milton

WM Keck Science Faculty Papers

Short-term plasticity is a pervasive feature of synapses. Synapses exhibit many forms of plasticity operating over a range of time scales. We develop an optimization method that allows rapid characterization of synapses with multiple time scales of facilitation and depression. Investigation of paired neurons that are postsynaptic to the same identified interneuron in the buccal ganglion of Aplysia reveals that the responses of the two neurons differ in the magnitude of synaptic depression. Also, for single neurons, prolonged stimulation of the presynaptic neuron causes stimulus-induced increases in the early phase of synaptic depression. These observations can be described by a …


Dynamic Diseases In Neurology And Psychiatry, John Milton, Deborah Black Mar 1995

Dynamic Diseases In Neurology And Psychiatry, John Milton, Deborah Black

WM Keck Science Faculty Papers

Thirty-two (32) periodic diseases of the nervous system are identified in which symptoms and/or signs recur. In 10/32, the recurrence of a symptom complex is one of the defining features of the illness, whereas in 22/32 oscillatory signs occur in the setting of an ongoing nervous system disorder. We discuss the possibility that these disorders may be dynamic diseases.


Functional Consequences Of Compartmentalization Of Synaptic Input, Melissa J. Coleman, Michael P. Nusbaum Nov 1994

Functional Consequences Of Compartmentalization Of Synaptic Input, Melissa J. Coleman, Michael P. Nusbaum

WM Keck Science Faculty Papers

Intra-axonal recordings of stomatogastric nerve axon 1 (SNAX1) indicate that there are synaptic inputs onto the SNAX1 terminals in the stomatogastric ganglion (STG) of the crab Cancer borealis (Nusbaum et al., 1992b). To determine whether this synaptic input only influenced SNAX1 activity within the STG, we identified the SNAX1 soma in the commissural ganglion (CoG). We found that this neuron has a neuropilar arborization in the CoG and also receives synaptic inputs in this ganglion. Based on its soma location, we have renamed this neuron modulatory commissural neuron 1 (MCN1). While intracellular stimulation of MCN1soma and MCN1SNAX has the same …


Complex Motor Dynamics And Control In Multi-Looped Negative Feedback Systems, Anne Beuter, John Milton, Christiane Labrie, Leon Glass Nov 1989

Complex Motor Dynamics And Control In Multi-Looped Negative Feedback Systems, Anne Beuter, John Milton, Christiane Labrie, Leon Glass

WM Keck Science Faculty Papers

Experiments were performed in normal and Parkinsonian subjects who were asked to maintain a constant finger position using time-delayed visual feedback. The finger position showed complex dynamics, with characteristic differences between normal and Parkinosonian subjects. Here we discuss some of the theoretical issues that must be resolved in order to understand the mechanisms that underlie the generation of these complex signals.