Figure 2.

Stimulus set and imaging paradigm. Top: a sample stimulus set. The checkerboard patterns were typically counterflickering at 5 Hz in a 50% duty cycle. In addition to this set, an identical set of static, solid bar stimuli were used. The stimulated field was matched with the imaged field of view (i.e., condition b stimulated 26° height by 35° across). Stimuli were filtered with a 540 × 30 nm band-pass filter, unless otherwise noted. Stimulus conditions were presented in a random sequence. Middle: stimulus presentation sequence and functional image development progression. Bottom: a representation of the stimulus presentation sequence with each frame showing 500 ms stimulus time interval. Most of the data presented in this article were generated from the following sequence: 2 seconds, stimulus off; 3 seconds, stimulus on; 5 seconds, stimulus off. Below the stimulus presentation frames is an image-development sequence. Each frame was generated by Fr_n − Fr₀. Baseline signal (0–2 seconds) shows minimal optical change from Fr₀. The signal developed and grew in intensity from 2 to 5 seconds (stimulus ON time). The recovery phase shows a slow decay of the signal back toward the baseline reflectance after the stimulus was turned off (5–10 seconds).