PT  - JOURNAL ARTICLE
AU  - Shreesh P. Mysore
AU  - Eric I. Knudsen
TI  - Flexible Categorization of Relative Stimulus Strength by the Optic Tectum
AID  - 10.1523/JNEUROSCI.5425-10.2011
DP  - 2011 May 25
TA  - The Journal of Neuroscience
PG  - 7745--7752
VI  - 31
IP  - 21
4099  - http://www.jneurosci.org/content/31/21/7745.short
4100  - http://www.jneurosci.org/content/31/21/7745.full
SO  - J. Neurosci.2011 May 25; 31
AB  - Categorization is the process by which the brain segregates continuously variable stimuli into discrete groups. We report that patterns of neural population activity in the owl optic tectum (OT) categorize stimuli based on their relative strengths into “strongest” versus “other.” The category boundary shifts adaptively to track changes in the absolute strength of the strongest stimulus. This population-wide categorization is mediated by the responses of a small subset of neurons. Our data constitute the first direct demonstration of explicit categorization of stimuli by a neural network based on relative stimulus strength or salience. The finding of categorization by the population code relaxes constraints on the properties of downstream decoders that might read out the location of the strongest stimulus. These results indicate that the ensemble neural code in the OT could mediate bottom-up stimulus selection for gaze and attention, a form of stimulus categorization in which the category boundary often shifts within hundreds of milliseconds.