MIT 9 02 - Lecture Notes (11 pages)

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Lecture Notes



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Lecture Notes

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Pages:
11
School:
Massachusetts Institute of Technology
Course:
9 02 - Brain Laboratory

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The simultaneous coding of orientation and contrast in the responses of V1 complex cells Timothy J Gawne University of Alabama at Birmingham presented by Drew Altschul Background Major questions in this field Previous research V1 cells can encode information in temporal codes A single neuron s output is ambiguous Ambiguity reduced by temporal coding Recently found correlations How much can a single cell tell us How can we reduce the ambiguity of a single cell response strength to stimulus orientation response latency to stimulus contrast Temporal coding Has been seen in these cells Exact meaning is unclear in this context Focus of this Study Purpose to determine how effective responses of individual and groups of V1 complex cells are at representing stimulus orientation and contrast when both factors are allowed to vary Main findings Contrast is related to latency and temporal modulation Power of a single neuron Multiple cells multivariate Pooling improves spike code responses Methods One of the stimulus sets presented to the monkey subject Data Collection Data was taken from individual complex cells in V1 of two rhesus monkeys The monkeys viewed bars with varying uniformly distributed orientations and contrasts to the background The first monkey viewed sets of 12 differently oriented bars The second monkey viewed sets of 8 bars Each monkey viewed 8 sets 4 black and 4 white sets The individual spikes of individual cells were measured via extracellular methods and further analyzed Methods Data Analysis Quantification Methods Spike count after stimulus Replace each spike with Gaussians and summed Principle Component Analysis Simplifies data into a few coefficients of waves Neural Network Combining multiple neuron signals Synthetic data set of group responses Plot of the average responses of the neurons to different stimuli Results Latency reflected stimulus contrast better than stimulus orientation not an explicit function of the strength of the response Contrast



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