Inspection of cluster centroids (the average VRV of cells within the cluster) revealed that clusters respond differentially across the panel of 16 moving spot stimuli and show direction, size, and polarity selectivity.
To examine the stimulus tuning of hunting responses, we presented a panel of moving spot stimuli that differed in terms of four stimulus features: direction, size, speed, and contrast polarity.
Cathine appeared purple, while cathinone was a burnt orange moving spot.
However, the majority of PVNs were sensitive to spots in the visual field, with optimal responses to either stationary flashing spots, moving spots regardless of their size or direction, or small spots moving in particular directions.
Specifically, moving spots could differ in direction (left-right or right-left motion), speed (fast 30°/s or slow 15°/s), size (small 3.5°, large 13.2°), or contrast polarity (a bright spot on a dark background, or a dark spot on a bright background) (see the Experimental Procedures).
Correlations from small moving spots were relatively weak.
Clusters 10 and 11 form a second pair tuned to nose-tail-moving spots.
However, don't move spots; it's against the rules.
In this setup, the sample can be moved as close as 0.7 mm to the window, enabling a beam spot size of 7 × 6 μm2 to be achieved.
The spot size is 20 μm diameter.
