Table 2.
Parameter sets used across protocols and species
| Primate |
Cat | |||
|---|---|---|---|---|
| Default parameter set 1 Single peak, low speeds | Parameter set 2 Double peak, mid speeds | Parameter set 3 Single peak, high speeds | Parameter set 4 Single peak, smaller eye range | |
| *tv(x) | sign(x)(0.1|x|2 + 1.2|x|) | sign(x)(0.6|x|2 + 0.5|x|) | sign(x)(0.01|x|2 + 6|x|) | sign(x)(0.01|x|2 + 4|x|) |
| *SAT | 40 | 40 | 100 | 35 |
| *P | Fast phase: 2 | Fast phase: 2.3 | Fast phase: 2.7 | Fast phase: 2 |
| Slow phase: 0.28 | Slow phase: 0.25 | Slow phase: 0.27 | Slow phase: 0.22 | |
| *vnb | 0.02 | 0.05 | 0.02 | 0.02 |
| Kept constant in all cases: | ||||
| sg(x) | 2.2(3.31 × 10−7|x|3 + 2.65 × 10−4|x|2 + 8.4 × 10−3|x|) | −3.17 × 10−5|x|3 + 2.9 × 10−3|x|2 + 7.1 × 10−3|x| | ||
| tvn | 0.4 | |||
| gb | 1 | |||
| th | 0.05 | |||
| SCTc | 10 ms | |||
| vog | Type I: 0.1 inhibitory; Type II: 0.6 excitatory | |||
| vob | 0.35 | |||
| ep | Fast phase: 11; Slow phase: 1.31 | |||
| eg | Fast phase: 0.09; Slow phase: 0.759 | |||
The first four parameters (marked with an asterisk) vary mildly to generate different characteristics between the given parameter sets. Parameter set 1 provides slower single-peak velocity profiles during gaze shifts, typically seen in humans or untrained monkey, in the presence of head restraints and/or random perturbations (Boulanger et al. 2012; Goossens and Van Opstal 1997; Guitton and Volle 1987). In this case, large targets cause a soft saturation plateau for eye position (typical monkey or human trajectories). Parameter set 2 results in double peaks in velocity for larger target eccentricities in both gaze and eye trajectories (Freedman 2001; Freedman and Sparks 1997; Roy and Cullen 1998). Parameter set 3 replicates single-peak gaze velocities with high speeds reported by Gandhi (2012). Parameter set 4 provides an example of species-specific trends: it is similar to the default except that the forward gain tv is enhanced for faster gaze shifts and the head gain field sg is increased to emphasize the head and limit eye deviations (as in the cat; Guitton et al. 1984, 1990). Refer to the model in Fig. 3, to the glossary in the Introduction for definitions and to the appendix for the role of parameters in controller signals.