Chapter IV: Task-dependent Modulation Of Face Gaze
4.3 Don’t Look Study in Amygdala Lesion Patients
4.3.2 Results
rather than total gaze on-screen. This analysis would indicate whether the distribution of gaze among the three eye-related ROIs differed between groups.
Finally, for the analysis of center bias, we analyzed the two ROIs defining the socially salient regions of the face (Eye Region Total and Mouth). For the Eye and Mouth ROIs, we calculated the Euclidean distance for each point within the ROI to the vertical and horizontal midlines of the ROI, weighting each distance by gaze duration (i.e., the heatmap value for the point). Next, we summed these values, then divided by the sum of gaze in the ROI to obtain the average gaze distance to the horizontal and vertical midlines.
Statistical analyses were conducted by carrying out repeated-measures ANOVAs for each ROI in the analysis subset, with a between-subjects factor of group (amygdala, Control) and within- subjects factors of condition (Free View, Avoid Eyes, Avoid Mouth) and stimulus type (Open Eyes, Closed Eyes). In order to investigate the relationship of the two restricted conditions (Avoid Eyes, Avoid Mouth) against the unrestricted condition (“Free View”), appropriate contrasts were also conducted for gaze to the Right Eye, Left Eye, Eye Region Total, and Mouth.
A Control Amygdala
Op en e ye s Cl os ed e ye s
B
Op en e ye s Cl os ed e ye s
C
Op en e ye s Cl os ed e ye s
FREE
Figure 4.12. Heat maps for the amygdala and control groups, and conditions with Open Eyes and Closed Eyes stimuli. Maps were generated by using a Gaussian kernel function to spatially smooth each duration-weighted fixation point, then maps were averaged across trials and subjects. Warmer colors represent longer total fixation time.
4.3.2.1 Gaze Proportions in all regions of interest
The first set of analyses focused on gaze to the different regions of interest (see Figure 4.10-A for ROIs). A repeated-measures ANOVA with between-subjects factor of group and within- subjects factors of condition and stimulus was conducted for each of the seven ROIs (see Figure 4.13).
Figure 4.13. Proportion of fixation time in the ROIs in the amygdala (red) and control (blue) subjects. Error bars denote standard error.
Right Eye
The ANOVA for the right eye indicated there were no significant interactions involving group (all ps > .211), and no main effect of group (p = .578). Neither of the planned contrasts comparing the unrestricted condition to the two restricted conditions was significant (ps >
Open Eyes Closed Eyes 0
0.05 0.1 0.15 0.2
Proportion of Time (%)
Stimulus Type Off−Head
Open Eyes Closed Eyes 0
0.2 0.4 0.6 0.8 1
Proportion of Time (%)
Stimulus Type Head Remainder
Open Eyes Closed Eyes 0
0.05 0.1 0.15 0.2
Proportion of Time (%)
Stimulus Type Nose
Open Eyes Closed Eyes 0
0.2 0.4 0.6 0.8
Proportion of Time (%)
Stimulus Type Eye Region Total
Open Eyes Closed Eyes 0
0.1 0.2 0.3 0.4
Proportion of Time (%)
Stimulus Type Left Eye
Open Eyes Closed Eyes 0
0.1 0.2 0.3 0.4
Proportion of Time (%)
Stimulus Type Right Eye
Open Eyes Closed Eyes 0
0.2 0.4 0.6 0.8 1
Proportion of Time (%)
Stimulus Type Mouth
Open Eyes Closed Eyes 0
0.05 0.1 0.15 0.2
Proportion of Time (%)
Stimulus Type
Open Eyes Closed Eyes 0
0.2 0.4 0.6 0.8 1
Proportion of Time (%)
Stimulus Type
Open Eyes Closed Eyes 0
0.05 0.1 0.15 0.2
Proportion of Time (%)
Stimulus Type
Open Eyes Closed Eyes 0
0.2 0.4 0.6 0.8
Proportion of Time (%)
Stimulus Type
Open Eyes Closed Eyes 0
0.1 0.2 0.3 0.4
Proportion of Time (%)
Stimulus Type
Open Eyes Closed Eyes 0
0.1 0.2 0.3 0.4
Proportion of Time (%)
Stimulus Type
Open Eyes Closed Eyes 0
0.2 0.4 0.6 0.8 1
Proportion of Time (%)
Stimulus Type
Open Eyes Closed Eyes 0
0.05 0.1 0.15 0.2
Proportion of Time (%)
Stimulus Type 0Open Eyes Closed Eyes 0.2
0.4 0.6 0.8 1
Proportion of Time (%)
Stimulus Type 0Open Eyes Closed Eyes 0.05
0.1 0.15 0.2
Proportion of Time (%)
Stimulus Type 0Open Eyes Closed Eyes 0.2
0.4 0.6 0.8
Proportion of Time (%)
Stimulus Type 0Open Eyes Closed Eyes 0.1
0.2 0.3 0.4
Proportion of Time (%)
Stimulus Type 0Open Eyes Closed Eyes 0.1
0.2 0.3 0.4
Proportion of Time (%)
Stimulus Type 0Open Eyes Closed Eyes 0.2
0.4 0.6 0.8 1
Proportion of Time (%)
Stimulus Type Control Amygdala
Free View
Avoid Eyes
Avoid Mouth
FREE
.216). There was, however, a main effect of stimulus type, F(1,4) = 18.77, p = .012, η2 = .892, indicating that regardless of group, participants looked more at the right eye for Open Eyes stimuli than Closed Eyes stimuli (Open eyes: M = 13.4%, SD = 1.7; Closed eyes: M = 10.7%, SD = 1.1).
Left Eye
The ANOVA for the left eye indicated there were no significant interactions involving group (all ps > .225), and no main effect of group (p = .148). Neither of the planned contrasts comparing the unrestricted condition to the two restricted conditions was significant (ps >
.218).
Eye Region Total
The ANOVA for the total eye region revealed no significant interactions involving group (all ps > .189), nor a main effect of group (p = .228). Neither of the planned contrasts was significant (ps > .375).
Mouth
The ANOVA for the mouth indicated there were no significant interactions involving group (all ps > .253), and no main effect of group (p = .141). Neither of the planned contrasts was significant (ps > .213).
Nose
The ANOVA for gaze to the nose revealed a marginally significant main effect of group, F(1,4) = 4.40, p = .104, η2 = .524, suggesting greater gaze to the nose region in the amygdala group relative to controls (Amygdala: M = 9.4%, SD = 1.4; Controls: M = 5.4%, SD = 1.4).
There were no significant interactions involving group (all ps > .691).
Head Remainder
The ANOVA for gaze to the head remainder revealed no significant interactions involving group (all ps > .200), nor a main effect of group (p = .109).
Off-Head
The ANOVA for gaze off-head revealed no significant interaction effects involving group (all ps > .145), but a marginally significant main effect of group, F(1,4) = 4.38, p = .104, η2 = .523, suggesting there was less gaze to off the head regions in the amygdala group than in the control group (Amygdala: M = 1.0%, SD = 0.7; Controls: M = 3.2%, SD = 0.7).
4.3.2.2 Gaze distribution in eye region
To examine the distribution of gaze in the eye region, we calculated the proportion of gaze time in each eye ROI relative to the total gaze time spent in the entire eye region (see Figure 4.11-B for ROIs). Results are summarized below in Figure 4.14.
Figure 4.14. Gaze proportions in the eye region in the amygdala (red) and control (blue) groups. Error bars denote standard error.
Right Eye
The ANOVA for the right eye indicated there were no significant interactions involving group (all ps > .315), and no main effect of group (p = .594). Neither of the planned contrasts comparing the unrestricted condition to the two restricted conditions was significant (ps >
Open Eyes Closed Eyes
0 0.2 0.4 0.6 0.8 1
Proportion of Time (%)
Stimulus Type Eye Region Remainder/Total Eye Region
Open Eyes Closed Eyes
0 0.1 0.2 0.3 0.4
Proportion of Time (%)
Stimulus Type Left Eye/Total Eye Region
Open Eyes Closed Eyes
0 0.1 0.2 0.3 0.4
Proportion of Time (%)
Stimulus Type Right Eye/Total Eye Region
Open Eyes Closed Eyes
0 0.2 0.4 0.6 0.8 1
Proportion of Time (%)
Stimulus Type 0 Open Eyes Closed Eyes
0.1 0.2 0.3 0.4
Proportion of Time (%)
Stimulus Type 0 Open Eyes Closed Eyes
0.1 0.2 0.3 0.4
Proportion of Time (%)
Stimulus Type
Open Eyes Closed Eyes
0 0.2 0.4 0.6 0.8 1
Proportion of Time (%)
Stimulus Type 0 Open Eyes Closed Eyes
0.1 0.2 0.3 0.4
Proportion of Time (%)
Stimulus Type 0 Open Eyes Closed Eyes
0.1 0.2 0.3 0.4
Proportion of Time (%)
Stimulus Type Control Amygdala
Free View
Avoid Eyes
Avoid Mouth
FREE
.390). There was, however, a significant main effect of stimulus type, F(1,4) = 30.77, p = .005, η2 = .980, again indicating that regardless of group, participants spent a greater proportion of gaze in the eye region looking at the right eye for Open Eyes stimuli compared to Closed Eyes stimuli (Open eyes: M = 26.4%, SD = 2.8; Closed eyes: M = 21.8%, SD = 2.3). Neither of the planned contrasts was significant (ps > .390).
Left Eye
The ANOVA for the left eye revealed no significant interactions involving group (all ps > .124) and no main effect of group (p = .448).
Eye Region Remainder
The ANOVA for the remainder of the eye region revealed no significant interactions involving group (all ps > .255) and no main effect of group (p = .354). Neither of the planned contrasts was significant (ps > .710).
4.3.2.3 Center bias to horizontal and vertical midlines
To compare average gaze distance (measured in degrees of visual angle) from the vertical and horizontal midlines in the socially salient regions of the face, a two repeated-measures ANOVAs for the Eye Region and Mouth ROIs was conducted (see Figure 3.3-C for ROIs).
Eye Region
The ANOVA for the eye region indicated there were no interactions involving group (all ps
>.557) and no main effect of group (p = .403) for distance to the vertical midline. There were also no interactions involving group for distance to the horizontal midline (all ps >.157), and no main effect of group for distance to the horizontal midline (p = .581).
Mouth
The ANOVA for the mouth did not reveal any significant interactions involving group for distance to the vertical midline (all ps > .291), nor a main effect of group (p = .799). There were also no significant interactions involving group for distance to the horizontal midline (all ps >
.737), nor a main effect of group (p = .970).