neural prediction challenge
DESCRIPTION
Neural Prediction Challenge. - Gaurav Mishra - Pulkit Agrawal. How do neurons work. Stimuli Neurons respond (Excite/Inhibit) ‘Electrical Signals’ called Spikes Spikes encode information !! (Many Models). Our Case…. Stimuli Video of Natural Images - PowerPoint PPT PresentationTRANSCRIPT
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Neural Prediction Challenge
-Gaurav Mishra-Pulkit Agrawal
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How do neurons workStimuli Neurons respond (Excite/Inhibit)
‘Electrical Signals’ called Spikes
Spikes encode information !! (Many Models)
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Our Case…Stimuli Video of Natural Images
Response of 12 V1 neurons #Spikes
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Our Data…A movie for each neuron
Frames Down sampled images (16x16)
Each frame Image spans twice the receptive field diameter16ms in duration
Known: #Spikes/frame
To build a model correlating stimulus and spike count.
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Method 1: RNNsRecursive neural networks
Composed of feed forward and feed back subnets.Were initially designed for the purpose of
controlling nonlinear dynamical systems
Source: Hush et al. The Recursive Neural Network and its Application in Control Theory. Computers Elect. Engng. Vol. 19, No. 4, pp. 333-341, 1993
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An exemplary recursive multi-layer perceptron:
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Echo State NetworksDynamic neural networksThe hidden layer of ESN consists of a
single large reservoir with neurons connected to each other randomly.
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Using RNNsRNNs have been used for inverse modeling
purposesCan handle time series data because of the
presence of feed back and delay mechanismsMay need to down sample data even further
to keep network size manageable.
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ResultsAccuracy:
Average: around 50 percentBest Case: 89 percent
But does percentage error give the correct picture?No.
The correlation coefficient gives a more accurate picture of the performance of the network.
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Results
Average CC: 0.15
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STRFProblem: Stimulus
Black Box
Spike Rate
Concept of ‘Filter’
Space and Time both !Latency !
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Phase Invariance..
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The Math of Estimation..
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Current ResultsUsing ADABOOST:
Accuracy: 34 percentCC: 0.1543
SRTFCC: 0.1526
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ReferencesPredicting neural responses during natural vision, S. David,
J.Gallant, Computation in neural systems 2005Wikipedia article on neural coding (
http://en.wikipedia.org/wiki/Neural_coding)Theunissen et al., Estimating spatial temporal receptive field of
auditory and visual neurons from their responses to natural stimuli .Network: Comp Neural Systems 12:289–316.
Hush et al. The Recursive Neural Network and its Application in Control Theory. Computers Elect. Engng. Vol. 19, No. 4, pp. 333-341, 1993
Le Yang, Yanbo Xue. Development of A New Recurrent Neural Network Toolbox (RNN-Tool) (http://soma.mcmaster.ca/~yxue/papers/RMLP_ESN_Report_Yang_Xue.pdf)