Table 1.
Baseline of saccade duration and peak velocity (pre-adaptation phase).
Figure 1.
Protocol of reactive and voluntary saccade adaptation in the mask condition (only rightward trials represented).
Vertical and long horizontal arrows indicate primary saccades and short horizontal arrows indicate corrective saccades. When a horizontal primary saccade is detected (threshold of 70–90°/sec) the target or the display jumped, respectively in the reactive and voluntary saccade adaptation. Fifteen, 50, 100 or 800 ms after saccade offset, the visual display is replaced by a mask in the mask condition. In the no-mask condition, 15 or 50 ms after saccade termination, a blank screen replaced the visual display.
Figure 2.
Time-course of the adaptation of reactive and voluntary saccades.
Mean gain change is represented as a function of the blocks of trials and superimposed for the different post-saccadic durations of jumped target in the mask condition (grey background – A, B) and no-mask condition (white background – C, D), for reactive (A, C) and voluntary (B, D) saccades adaptation. Mean gain change was calculated across the 5 subjects of each experimental session. Gray lines indicate the gain changes for the shortest target durations (dashed lines: 15 ms – solid lines: 50 ms) and black lines indicate the gain changes for the longest target durations (dashed lines: 100 ms – solid lines: 800 ms). The blocks of trials are: pre-adaptation (pre), adaptation blocks with an intra-saccadic step of 25% of initial target eccentricity (a25, b25) or of 40% (c40, d40) and post-adaptation (post). Error bars are SEMs. Significant differences of gain changes between the target durations are indicated by * (p<0.05), ** (p<0.01) and *** (p<0.001).
Figure 3.
Adaptation after-effect for the different target durations and mask conditions.
Mean gain changes for reactive saccades (black bars) and voluntary saccades (grey bars) calculated between the pre-adaptation and post-adaptation blocks. These gain changes are plotted as a function of target durations in the mask condition (grey background) and in the no-mask condition (white background). Error bars are SEMs. Significant differences of gain changes between the saccade categories, target durations and masking conditions are indicated by * (p<0.05), ** (p<0.01) and *** (p<0.001).
Figure 4.
Latencies of secondary saccades in adaptation sessions of reactive saccades.
Latency distribution of secondary saccades (first saccades following primary saccades, whether corrective or not) measured in the adaptation sessions of reactive saccades. Different target durations (15, 50, 100 and 800 ms) are shown in the different plots for the mask condition (grey background) and the no-mask condition (white background). Note a dip in distributions (arrow and dotted lines) around 100 ms (mask condition) or 125–135 ms (no-mask condition) after the disappearance of the stepped target (vertical dashed line).
Figure 5.
Accuracy of secondary saccades and rate of corrective saccades in adaptation sessions.
(A) Amplitude of secondary saccades represented as a function of distance from primary saccade endpoint to jumped target. In this example, the secondary saccades were measured in the adaptation sessions of reactive (▪) and of voluntary (o) saccades in the mask condition, for the target duration of 15 ms. Secondary corrective saccades are located in quadrants I and III, corresponding to secondary saccades with positive (negative) amplitude when the jumped target was located in the right (left) visual field. (B) Rate of corrective saccades relative to the total number of secondary saccades measured during the adaptation sessions of reactive (black bars) and voluntary (grey bars) saccades. The mean rate of corrective saccades was calculated across the 5 subjects of each experimental session and is represented as a function of the target durations (15, 50, 100 and 800 ms) for the mask (grey background) and the no-mask (white background) conditions. Error bars are SEMs. Significant differences of gain changes between the saccade categories and target durations are indicated by * (p<0.05), ** (p<0.01).
Figure 6.
Schematic representation of the results.
This schema represents the differences in error signal processing between saccade categories and between adaptation and corrective saccade generation. Each square indicates the minimal target duration leading to optimal adaptation or to optimal generation of corrective saccades, for both saccade categories. The shading of the square represents the masking condition in which this target duration is required: grey square for the mask condition and black square for the no-mask condition (bicolour square when the same target duration is required in both masking conditions). The grey rectangles “Mask” symbolise the fact that when the mask is presented, a longer duration of stepped target is necessary to induce optimal adaptation and corrective saccade generation.