63 research outputs found
A Kernel-Based Calculation of Information on a Metric Space
Kernel density estimation is a technique for approximating probability
distributions. Here, it is applied to the calculation of mutual information on
a metric space. This is motivated by the problem in neuroscience of calculating
the mutual information between stimuli and spiking responses; the space of
these responses is a metric space. It is shown that kernel density estimation
on a metric space resembles the k-nearest-neighbor approach. This approach is
applied to a toy dataset designed to mimic electrophysiological data
Two monopoles of one type and one of another
The metric on the moduli space of charge (2,1) SU(3)
Bogomolny-Prasad-Sommerfield monopoles is calculated and investigated. The
hyperKahler quotient construction is used to provide an alternative derivation
of the metric. Various properties of the metric are derived using the
hyperKahler quotient construction and the correspondence between BPS monopoles
and rational maps. Several interesting limits of the metric are also
considered.Comment: 48 pages, LaTeX, 2 figures. Typos corrected. Version in JHE
Parameter estimation of neuron models using <i>in-vitro </i>and<i> in-vivo </i>electrophysiological data
Spiking neuron models can accurately predict the response of neurons to somatically injected currents if the model parameters are carefully tuned. Predicting the response of in-vivo neurons responding to natural stimuli presents a far more challenging modeling problem. In this study, an algorithm is presented for parameter estimation of spiking neuron models. The algorithm is a hybrid evolutionary algorithm which uses a spike train metric as a fitness function. We apply this to parameter discovery in modeling two experimental data sets with spiking neurons; in-vitro current injection responses from a regular spiking pyramidal neuron are modeled using spiking neurons and in-vivo extracellular auditory data is modeled using a two stage model consisting of a stimulus filter and spiking neuron model
Dentate gyrus and hilar region revisited
AbstractIt is suggested that the dentate gyrus and hilar region in the hippocampus perform memory selection and that the selectivity of the gating of memory by this circuit is modulated by the norepinephrine–glutamate loop described by Mather et al.</jats:p
Diffusion Modelling Reveals the Decision Making Processes Underlying Negative Judgement Bias in Rats:Modelling Decision Making during Negative Affect
Human decision making is modified by emotional state. Rodents exhibit similar biases during interpretation of ambiguous cues that can be altered by affective state manipulations. In this study, the impact of negative affective state on judgement bias in rats was measured using an ambiguous-cue interpretation task. Acute treatment with an anxiogenic drug (FG7142), and chronic restraint stress and social isolation both induced a bias towards more negative interpretation of the ambiguous cue. The diffusion model was fit to behavioural data to allow further analysis of the underlying decision making processes. To uncover the way in which parameters vary together in relation to affective state manipulations, independent component analysis was conducted on rate of information accumulation and distances to decision threshold parameters for control data. Results from this analysis were applied to parameters from negative affective state manipulations. These projected components were compared to control components to reveal the changes in decision making processes that are due to affective state manipulations. Negative affective bias in rodents induced by either FG7142 or chronic stress is due to a combination of more negative interpretation of the ambiguous cue, reduced anticipation of the high reward and increased anticipation of the low reward
Instanton vibrations of the 3-Skyrmion
The Atiyah-Drinfeld-Hitchin-Manin matrix corresponding to a tetrahedrally
symmetric 3-instanton is calculated. Some small variations of the matrix
correspond to vibrations of the instanton-generated 3-Skyrmion. These
vibrations are decomposed under tetrahedral symmetry and this decomposition is
compared to previous knowledge of the 3-Skyrmion vibration spectrum.Comment: 10 pages, LaTeX, no figures, PRD version with longer introduction and
minor change
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