Contingent adaptation in masking and surround suppression.

Area of Science:

• Neuroscience
• Computational Neuroscience
• Psychophysics

Background:

• Neural adaptation modifies neuronal responses based on recent activity.
• Traditional models attribute adaptation to individual neuron input.
• Hebbian normalization proposes adaptation depends on correlated neural firing patterns.

Purpose of the Study:

• To test the psychophysical prediction that neural adaptation depends on second-order statistics of input stimuli.
• To investigate if simultaneous stimulus presentation strengthens mutual suppression between neuronal subpopulations.

Main Methods:

• Two psychophysical experiments were conducted.
• Experiment 1: Assessed the effectiveness of one grating pattern for masking another after synchronous (plaid) versus asynchronous (interleaved) adaptation.
• Experiment 2: Measured apparent contrast of a central grating under different surround conditions after adaptation.

Main Results:

• Synchronous adaptation (plaid) led to increased masking effectiveness compared to asynchronous adaptation.
• Adaptation with a consistent surround (center-surround configuration) reduced apparent contrast more than adaptation with a changing surround.
• These findings support the model where increased response covariance enhances mutual suppression between neurons.

Conclusions:

• Neural adaptation is influenced by the statistical structure of correlated neural activity.
• Mutual suppression between neuronal populations increases with response covariance.
• This effect of correlated firing on adaptation is observable in perceptual tasks both at and above sensory threshold.