Stimulus-choice (mis)alignment in primate area MT

Area of Science:

• Neuroscience
• Computational Neuroscience
• Sensory Perception

Background:

• Neural activity in sensory areas often correlates with an animal's perceptual report, especially near the perceptual threshold.
• This phenomenon is typically explained by feedforward readout of neural activity by downstream decision-making circuits.
• However, the interpretation of choice-correlated activity is ambiguous and requires understanding population-wide neural correlations.

Purpose of the Study:

• To investigate the nature of choice-correlated activity in the middle temporal (MT) area during perceptual decision-making.
• To differentiate between sensory-driven and choice-correlated activity within the population code.
• To understand how neural population activity relates to stimulus information and decision outcomes.

Main Methods:

• Utilized a statistical nonlinear dimensionality reduction technique on single-trial ensemble recordings from the MT area.
• Extracted low-dimensional latent factors representing population-wide neural fluctuations.
• Analyzed the alignment of choice-correlated signals with stimulus encoding dimensions.

Main Results:

• Extracted latent factors strongly encoded stimulus direction with a temporal signature similar to single MT neurons.
• Found a significant component of choice information residing in a subspace orthogonal to the stimulus representation.
• Observed that this misaligned choice information is inconsistent with an optimal feedforward readout model.

Conclusions:

• The misaligned choice information suggests a mechanism where feedforward sensory information coexists with decision-making processes.
• The temporal dynamics of these signals indicate potential feedback from downstream areas to the sensory population.
• Hypothesize that this non-corrupting choice-correlated feedback may play a role in learning or reinforcing sensory-motor relationships.