The following is a summary of “Role of lateral modulation in orientation-specific adaptation effect,” published in the February 2022 issue of Ophthalmology by Lin, et al.

The normalization process of contrast gain control in responsive neurons is reflected in center-surround modulation in visual processing. When prior adaptation to a clockwise (CW) tilted grating occurs, a counterclockwise tilt is perceived in a vertical grating, known as the tilt-aftereffect (TAE). Adding a same-orientation annular surround to an adapter modulates the magnitude of the TAE, suggesting lateral inhibitory modulation. 

To further examine the lateral modulation effect, center-surround sinusoidal patterns were used as adapters, and the adapter surround and center orientations were varied independently. The target had the same spatial extent as the adapter center, with no physical overlap with the adapter surround. Participants judged the target orientation as tilted either CW or counterclockwise from vertical after adaptation. 

Results showed that the adapter center determined the TAE magnitude when the surround orientation was constant, peaking between 10° and 20° of tilt. Additionally, the adapter surround orientation modulated the adaptation effect. The TAE magnitude first decreased and then increased as the surround orientation became increasingly different from the center’s, indicating that the surround modulation effect was orientation-specific. 

A divisive inhibition model explained these data, where the adaptation effect is represented by increasing the normalizing constant, and the surround modulation is captured by two multiplicative sensitivity parameters determined by the adapter surround orientation.

Source: jov.arvojournals.org/article.aspx?articleid=2778591