This allows us to generate repeated stochastic point process realizations, i.e. single trial spike trains, as shown for the example unit in Fig. 6D2. Clearly, the repeated simulation trials based on the dynamic RF activation (green) exhibit a spiking pattern, which is temporally sparser than the spiking pattern that stems from the static RF activation (blue). This also finds expression in the time histogram of the trial-averaged firing rate shown in Fig. 6D3. The firing rate is more peaked in the case of the dynamic RF, resembling the deterministic activation curve in Fig. 6D1. Spatial sparseness (also

termed population sparseness) refers to the situation where only a small number of units are significantly activated by a given stimulus. In the natural case of time-varying stimuli this implies a small number of active selleck neurons in any small time window while the rest of the neuron population expresses a low baseline activity. Again, we use S   (Eq. (2)) to quantify spatial sparseness from the population activation hh of hidden neurons and for each time step separately. The results depicted in Fig. 6B show a significantly higher spatial sparseness when the dynamic RF was applied with a mean (median) of 0.92 (0.93) as compared to the static RF with a mean (median) of 0.74 (0.74). We demonstrate

how the spatial sparseness for the static and the dynamic RF model in the population of hidden units affects spiking activity using our cascade point process model. http://www.selleckchem.com/products/PLX-4032.html Fig. 6E2 shows the simulated spiking activity of all 400 neurons based on the activation h(t)h(t) of the hidden neurons during 8 s of recording. Overall the static RF (blue) results in higher firing rates. The stimulus representation in the ensemble spike train appears more dense for the static RF (blue) than in the case of a dynamic RF (green). As shown in Fig. 6E3, fewer neurons were active at any

given Leukotriene-A4 hydrolase point in time when they were driven by the dynamic RF model. We suggested a novel approach to unsupervised learning of spatio-temporal structure in multi-dimensional time-varying data. We first define the general topology of an artificial neural network (ANN) as our model class. Through a number of structural constraints and a machine learning approach to train the model parameters from the data, we arrive at a specific ANN which is biologically relevant and is able to produce activations for any given temporal input (Section 2.1). We then extend this ANN with a Computational Neuroscience based cascade model and use this to generate trial variable spike trains (Section 2.3). The proposed aTRBM model integrates the recent input history over a small number of discrete time steps. This model showed superior performance to other models on a recognized benchmark dataset.