PT  - JOURNAL ARTICLE
AU  - Paul M Bays
TI  - A Signature of Neural Coding at Human Perceptual Limits
AID  - 10.1101/051714
DP  - 2016 Jan 01
TA  - bioRxiv
PG  - 051714
4099  - http://biorxiv.org/content/early/2016/05/25/051714.short
4100  - http://biorxiv.org/content/early/2016/05/25/051714.full
AB  - Simple visual features, such as orientation, are thought to be represented in the spiking of visual neurons using population codes. I show that optimal decoding of such activity predicts characteristic deviations from the normal distribution of errors at low gains. Examining human perception of orientation stimuli, I show that these predicted deviations are present at near-threshold levels of contrast. The findings may provide a neural-level explanation for the appearance of a threshold in perceptual awareness, whereby stimuli are categorized as seen or unseen. As well as varying in error magnitude, perceptual judgments differ in certainty about what was observed. I demonstrate that variations in the total spiking activity of a neural population can account for the empirical relationship between subjective confidence and precision. These results establish population coding and decoding as the neural basis of perception and perceptual confidence.