Results

The magnitudes of movement generated during anterior temporalis and medial pterygoid stimulation in Otolemur are presented in Table 2 and shown schematically in Figure 3. For Otolemur, movements detected by the orbital view camera were recorded for simultaneous anterior temporalis and medial pterygoid stimulation, and for anterior temporalis stimulation alone. For Otolemur, mediolateral eye movements caused by medial pterygoid alone are unavailable for the orbital view camera. The magnitudes of mediolateral eye movements generated during anterior temporalis stimulation in general exceed the diplopia arc length computed for Otolemur (see Table 1; Table 2, Orbital View Camera; Figure 3A, left). The average eye movements resulting from the simultaneous stimulation of the anterior temporalis and medial pterygoid do not exceed the estimated linear value of the disparity threshold value of Otolemur with the exception of one movement, which was the first muscle stimulation of the entire experiment. There was also variation in the directions of movements during these simultaneous stimulations: four made the eye translate medially, two laterally. Movements generated by isolated medial pterygoid stimulation were captured with the superior view camera

Table 2. Descriptive statistics for ocular kinematic data in Otolemur ┬┐arnettii and Felts catus

Otolemur Anterior temporalis Medial pterygoid AT+MP"

Cat 1 Anterior temporalis Medial pterygoid

Cat 2 Medial pterygoid

Cat 3 Anterior temporalis Medial pteryoid

Superior view camera Orbital view camera

N Mean SD Max Min Direction N Mean SD Max Min Direction

No data from this camera view 9.6 x 10-2 5.1 x 10-2 0.18 4.0 x lO"2 Protrude No data from this camera view

No data from this camera view

Medial

Protrude Protrude

10 10

Lateral Lateral

No data from this camera view

Protrude Protrude

10 10

Lateral Lateral

Data are in millimeters.

"AT + MP is a series of simultaneous stimulations of the anterior temporalis and medial pterygoid muscles.

Anterior temporalis stimulation

Otolemur

Medial pterygoid stimulation

Felis subject 3

Anterior temporalis stimulation

Felis subject 3

Medial pterygoid stimulation

Figure 3. Eye movements during anterior temporalis and medial pterygoid stimulation. Schematics for the movements generated during anterior temporalis stimulation (A) in the Otolemur (left) and Felis subject 3 (right), and the medial pterygoid stimulation (B). The arrows indicate the directions of eye movements, the numbers are magnitudes (mean and, in parentheses, standard deviations).

Figure 3. Eye movements during anterior temporalis and medial pterygoid stimulation. Schematics for the movements generated during anterior temporalis stimulation (A) in the Otolemur (left) and Felis subject 3 (right), and the medial pterygoid stimulation (B). The arrows indicate the directions of eye movements, the numbers are magnitudes (mean and, in parentheses, standard deviations).

(Table 2). When the medial pterygoid was stimulated in isolation, the mean amount of protrusion was nearly 0.1 mm (Figure 3B, left).

In Felis, anterior temporalis stimulation caused both protrusion and lateral displacement of the eye in subjects 1 and 3 (we do not have anterior temporalis data for subject 2) (Table 2, Figure 3A, right). The mean lateral displacement substantially exceeds the magnitude required to cause diplopia in Felis (see Table 1). Medial pterygoid stimulation caused both protrusion in subjects 1 and 3 (no data from the superior view camera for subject 2) and lateral displacement in all three subjects (Table 2). The mean lateral displacement for subject 2 was below the diplopia threshold, but the maximum displacement in this subject did exceed the estimated linear disparity threshold (Table 2). The mean lateral displacement exceeds the magnitude required to cause diplopia in two Felis subjects by nearly an order of magnitude. Displacement due to anterior temporalis stimulation as well as displacement and protrusion due to medial pterygoid are both responsible for disruptive-level eye movement magnitudes.

Data for simultaneous anterior temporalis and medial pterygoid stimulations were not recorded in the cats. As these two muscles in isolation cause similar eye movements, it is unlikely that synchronous effects would cancel each other out.

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