Friday, January 14, 2011

Modeling the World in the Brain

Berkes et al. show that spontaneous activity in the visual brain adapts during development to resemble the activity generated by external natural scenes. Here is background from the Science summary:
There is a wide consensus in neuroscience that the brain uses internal models to interpret external stimuli and to make predictions about future events. Despite this consensus and a rich history of studies providing ample behavioral evidence about optimal internal models in the brain, it has been difficult to identify the neural signatures of these internal models. Using statistical methods to analyze recordings from the visual cortex of ferrets, Berkes et al. found that neuronal firing patterns during spontaneous activity were similar to those during evoked activity. During development, it seems that the internal model in the visual cortex gradually adapts to the properties of natural visual scenes.
And the abstract:
The brain maintains internal models of its environment to interpret sensory inputs and to prepare actions. Although behavioral studies have demonstrated that these internal models are optimally adapted to the statistics of the environment, the neural underpinning of this adaptation is unknown. Using a Bayesian model of sensory cortical processing, we related stimulus-evoked and spontaneous neural activities to inferences and prior expectations in an internal model and predicted that they should match if the model is statistically optimal. To test this prediction, we analyzed visual cortical activity of awake ferrets during development. Similarity between spontaneous and evoked activities increased with age and was specific to responses evoked by natural scenes. This demonstrates the progressive adaptation of internal models to the statistics of natural stimuli at the neural level.

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