Healthy aging impairs face discrimination ability.

Face images enable individual identities to be discriminated from one another. We aimed to quantify age-related changes in different aspects of face identity discrimination. Face discrimination sensitivity was measured with a memory-free "odd-one-out" task. Five age groups (N = 15) of healthy adults with normal vision were tested: 20, 50-59, 60-69, 70-79, and 80-89. Sensitivity was measured for full-face images (all features visible), external features (head-shape, hairline), internal features (nose, mouth, eyes, and eyebrows) and closed-contour shapes (control object). Sensitivity to full-faces continuously declined by approximately 13% per decade, after 50 years of age. When age-related differences in visual acuity were controlled, the effect of age on face discrimination sensitivity remained. Sensitivity to face features also deteriorated with age. Although the effect for external features was similar to full-faces, the rate of decline was considerably steeper (approximately 3.7 times) for internal, relative to external, features. In contrast, there was no effect of age on sensitivity to shapes. All age groups demonstrated the same overall pattern of sensitivity to different types of face information. Healthy aging was associated with a continuous decline in sensitivity to both full-faces and face features, although encoding of internal features was disproportionately impaired. This age-related deficit was independent of differences in low-level vision. That sensitivity to shapes was unaffected by age suggests these results cannot be explained by general cognitive decline or lower-level visual deficits. Instead, healthy aging is associated with a specific decline in the mechanisms that underlie face discrimination.

In the Blink of an Eye: Reading Mental States From Briefly Presented Eye Regions.

Faces provide not only cues to an individual's identity, age, gender, and ethnicity but also insight into their mental states. The aim was to investigate the temporal aspects of processing of facial expressions of complex mental states for very short presentation times ranging from 12.5 to 100 ms in a four-alternative forced choice paradigm based on Reading the Mind in the Eyes test. Results show that participants are able to recognise very subtle differences between facial expressions; performance is better than chance, even for the shortest presentation time. Importantly, we show for the first time that observers can recognise these expressions based on information contained in the eye region only. These results support the hypothesis that the eye region plays a particularly important role in social interactions and that the expressions in the eyes are a rich source of information about other peoples' mental states. When asked to what extent the observers guessed during the task, they significantly underestimated their ability to make correct decisions, yet perform better than chance, even for very brief presentation times. These results are particularly relevant in the light of the current COVID-19 pandemic and the associated wearing of face coverings.

The Effect of Age-Related Macular Degeneration on Components of Face Perception.

Purpose: Patients with age-related macular degeneration (AMD) experience difficulty with discriminating between faces. We aimed to use a new clinical test to quantify the impact of AMD on face perception and to determine the specific aspects that are affected. Methods: The Caledonian face test uses an adaptive procedure to measure face discrimination thresholds: the minimum difference required between faces for reliable discrimination. Discrimination thresholds were measured for full-faces, external features (head-shape and hairline), internal features (nose, mouth, eyes, and eyebrows) and shapes (non-face task). Participants were 20 patients with dry AMD (logMAR VA = 0.14 to 0.62), 20 patients with wet AMD (0.10 to 0.60), and 20 age-matched control subjects (-0.18 to +0.06). Results: Relative to controls, full-face discrimination thresholds were, on average, 1.76 and 1.73 times poorer in participants with dry and wet AMD, respectively. AMD also reduced sensitivity to face features, but discrimination of the internal, relative to external, features was disproportionately impaired. Both distance VA and contrast sensitivity were significant independent predictors of full-face discrimination thresholds (R2 = 0.66). Sensitivity to full-faces declined by a factor of approximately 1.19 per 0.1 logMAR reduction in VA. Conclusions: Both dry and wet AMD significantly reduce sensitivity to full-faces and their component parts to similar extents. Distance VA and contrast sensitivity are closely associated with face discrimination sensitivity. These results quantify the extent of sensitivity impairment in patients with AMD and predict particular difficulty in everyday tasks that rely on internal feature information, including recognition of familiar faces and facial expressions.

Quantifying the effect of viewpoint changes on sensitivity to face identity.

Although faces can be recognized from different viewpoints, variations in viewpoint impair face identification ability. The present study quantified the effect of changes in viewpoint on sensitivity to face identity. We measured discrimination thresholds for synthetic faces presented from several viewpoints (same viewpoint condition) and the same faces shown with a change in viewpoint (5°, 10° or 20°) between viewing and test. We investigated three types of viewpoint change: (i) front-to-side (front-view matched to 20°° side-view), (ii) side-to-front (20° side-view matched to front) and (iii) symmetrical (10° left to 10° right). In the same viewpoint condition, discrimination thresholds were lowest for faces presented from 0° and increased linearly as the viewing angle was increased (threshold elevations: 0°â€¯= 1.00×, 5°â€¯= 1.11×, 10°â€¯= 1.22×, 20°â€¯= 1.69×). Changes in viewpoint between viewing and test led to further reductions in discrimination sensitivity, which depended upon the magnitude of viewpoint change (5°â€¯= 1.38×, 10°â€¯= 1.75×, 20°â€¯= 2.07×). Sensitivity also depended upon the type of viewpoint change: while a 20° front-to-side viewpoint change increased discrimination thresholds by a factor of 2.09×, a symmetrical change in viewpoint, of the same magnitude, did not significantly reduce sensitivity (1.26×). Sensitivity to face identity is significantly reduced by changes in viewpoint. Factors which determine the extent of this reduction include the magnitude of viewpoint change and symmetry. Our results support the premise of viewpoint-dependent encoding of unfamiliar face identities, and suggest that symmetry may be used to recognize identities across different viewpoints.

From individual features to full faces: Combining aspects of face information.

We investigated how information from face features is combined by comparing sensitivity to individual features with that for external (head shape, hairline) and internal (nose, mouth, eyes, eyebrows) feature compounds. Discrimination thresholds were measured for synthetic faces under the following conditions: (a) full-faces; (b) individual features (e.g., nose); and (c) feature compounds (either external or internal). Individual features and feature compounds were presented both in isolation and embedded within a fixed, task irrelevant face context. Relative to the full-face baseline, threshold elevations for the internal feature compound (2.41x) were comparable to those for the most sensitive individual feature (nose = 2.12x). External features demonstrated the same pattern. A model that incorporated all available feature information within a single channel in an efficient way overestimated sensitivity to feature compounds. Embedding individual features within a task-irrelevant context reduced discrimination sensitivity, relative to isolated presentation. Sensitivity to feature compounds, however, was unaffected by embedding. A loss of sensitivity when embedding features within a fixed-face context is consistent with holistic processing, which limits access to information about individual features. However, holistic combination of information across face features is not efficient: Sensitivity to feature compounds is no better than sensitivity to the best individual feature. No effect of embedding internal feature compounds within task-irrelevant external face features (or vice versa) suggests that external and internal features are processed independently.

Contributions of individual face features to face discrimination.

Faces are highly complex stimuli that contain a host of information. Such complexity poses the following questions: (a) do observers exhibit preferences for specific information? (b) how does sensitivity to individual face parts compare? These questions were addressed by quantifying sensitivity to different face features. Discrimination thresholds were determined for synthetic faces under the following conditions: (i) 'full face': all face features visible; (ii) 'isolated feature': single feature presented in isolation; (iii) 'embedded feature': all features visible, but only one feature modified. Mean threshold elevations for isolated features, relative to full-faces, were 0.84x, 1.08, 2.12, 3.34, 4.07 and 4.47 for head-shape, hairline, nose, mouth, eyes and eyebrows respectively. Hence, when two full faces can be discriminated at threshold, the difference between the eyes is about four times less than what is required when discriminating between isolated eyes. In all cases, sensitivity was higher when features were presented in isolation than when they were embedded within a face context (threshold elevations of 0.94x, 1.74, 2.67, 2.90, 5.94 and 9.94). This reveals a specific pattern of sensitivity to face information. Observers are between two and four times more sensitive to external than internal features. The pattern for internal features (higher sensitivity for the nose, compared to mouth, eyes and eyebrows) is consistent with lower sensitivity for those parts affected by facial dynamics (e.g. facial expressions). That isolated features are easier to discriminate than embedded features supports a holistic face processing mechanism which impedes extraction of information about individual features from full faces.

The Caledonian face test: A new test of face discrimination.

This study aimed to develop a clinical test of face perception which is applicable to a wide range of patients and can capture normal variability. The Caledonian face test utilises synthetic faces which combine simplicity with sufficient realism to permit individual identification. Face discrimination thresholds (i.e. minimum difference between faces required for accurate discrimination) were determined in an "odd-one-out" task. The difference between faces was controlled by an adaptive QUEST procedure. A broad range of face discrimination sensitivity was determined from a group (N=52) of young adults (mean 5.75%; SD 1.18; range 3.33-8.84%). The test is fast (3-4 min), repeatable (test-re-test r(2)=0.795) and demonstrates a significant inversion effect. The potential to identify impairments of face discrimination was evaluated by testing LM who reported a lifelong difficulty with face perception. While LM's impairment for two established face tests was close to the criterion for significance (Z-scores of -2.20 and -2.27) for the Caledonian face test, her Z-score was -7.26, implying a more than threefold higher sensitivity. The new face test provides a quantifiable and repeatable assessment of face discrimination ability. The enhanced sensitivity suggests that the Caledonian face test may be capable of detecting more subtle impairments of face perception than available tests.

Ulna Nerve Decompression at the Elbow in Patients with Normal Nerve Conduction Tests.

BACKGROUND: Ulna nerve compression at the elbow is the second most common neuropathy of the upper limb. It has been suggested that nerve conduction tests are required to correctly make the diagnosis. The aim of this study was to assess whether patients with normal nerve conduction testing benefitted from surgical release of the ulna nerve. METHODS: 56 patients with symptoms of ulna nerve compression at the elbow were evaluated prospectively. All patients underwent electrophysiology testing followed by ulna nerve decompression irrespective of the results of the electrophysiology testing. Functional scores using the QuickDASH and PEM score were collected up to 12 months post-surgery. RESULTS: No difference was found between the group with normal and the group with abnormal electrophysiology studies. CONCLUSIONS: We conclude that patients who clinically have ulna nerve compression still benefit from ulna nerve decompression despite normal nerve conduction tests.

Distinct lower visual field preference for object shape.

Humans manipulate objects chiefly within their lower visual field, a consequence of upright posture and the anatomical position of hands and arms.This study tested the hypothesis of enhanced sensitivity to a range of stimuli within the lower visual field. Following current models of hierarchical processing within the ventral steam, discrimination sensitivity was measured for orientation, curvature, shape (radial frequency patterns), and faces at various para-central locations (horizontal, vertical, and main diagonal meridians) and eccentricities (5° and 10°). Peripheral sensitivity was isotropic for orientation and curvature. By contrast, observers were significantly better at discriminating shapes throughout the lower visual field compared to elsewhere. For faces, however, peak sensitivity was found in the left visual field, corresponding to the right hemispheric localization of human face processing. Presenting head outlines without any internal features (e.g., eyes, mouth) recovered the lower visual field advantage found for simple shapes. A lower visual field preference for the shape of an object, which is absent for more localized information (orientation and curvature) but also for more complex objects (faces), is inconsistent with a strictly feed-forward model and poses a challenge for multistage models of object perception. The distinct lower visual field preference for contour shapes is, however, consistent with an asymmetry at intermediate stages of visual processing, which may play a key role in representing object characteristics that are particularly relevant to visually guided actions.

Comparison of fibrin glue with sutures for pterygium excision surgery with conjunctival autografts.

PURPOSE: To compare pterygium excision conjunctival autograft surgery using Tisseel fibrin glue versus Vicryl sutures. METHOD: Prospective randomized clinical trial. Fifty patients were randomized into either sutured graft or glued graft groups. Twenty-five received standard conjunctival autograft sutured with Vicryl and 25 received surgery with the autograft placed with Tisseel fibrin glue. Outcome measures include surgical time, patient discomfort, pathology, complications and recurrence rates at 3, 6 and 12 months. Patients were followed up at days 1, 7, 14, 30, 90, 180 and 365. RESULTS: The mean surgical time for the glue group was significantly shorter at 12 min compared with the suture group at 26 min (P < 0.001). Postoperative pain was significantly less at day 1 (P < 0.001) and day 2 (P < 0.05) but was not significantly different following these visits. Complications in the glue group included one patient with an absent graft at week 1 that required revision of the graft. At 3 months there were no recurrences in the glue group and two recurrences in the suture group. The 6- and 12-month recurrence rate was unchanged and not significantly different between the glue and suture groups (both 0/24 and 2/23, respectively). CONCLUSION: Both glued and sutured conjunctival autografting procedures are safe and effective methods for pterygium surgery. The glued autograft recurrence rate at 12 months was similar to that of sutured grafts. Conjunctival autograft with fibrin glue in pterygium surgery decreased surgical time and resulted in less postoperative pain in the first 48 hours but had a higher complication rate.

Upper gastrointestinal complications after renal transplantation: a 3-yr sequential study.

BACKGROUND: Upper gastrointestinal complications have historically resulted in considerable morbidity and mortality to renal transplant recipients. Over the last decade, antiulcer prophylaxis with proton-pump inhibitors and immunosuppression with tacrolimus-based regimes have been introduced. Little has been written about foregut complications after renal transplantation since the use of these agents. The aim of this study was to compare the frequency of upper gastrointestinal complications after renal transplantation in patients treated with (i) omeprazole vs. ranitidine, and (ii) tacrolimus vs. cyclosporin based immunosuppression. METHODS: Information on 236 patients undergoing renal transplantation between January 1996 and December 1998 was collected prospectively onto a computerized database. RESULTS: Overall, 20 patients (8%) developed upper gastrointestinal complications, opportunistic infections accounted for 9/20 (45%). No patient developed gastroduodenal ulceration, required laparotomy, suffered graft loss or died. There was no significant difference in the frequency of complications between patients that received antisecretory therapy with omeprazole (9/118, 8%) and those that received ranitidine (11/118, 9%), nor between those that were on tacrolimus (7/101, 7%) and those on cyclosporin (13/135, 10%) based immunosuppression regimes. Patients that developed foregut complications were significantly older than those not developing complications (mean age 50 vs. 43 yrs, p=0.05). Further, patients that developed opportunistic infections were more frequently diabetic than those in whom opportunistic infections were not seen (4/31, 13% vs. 5/205, 2%), p=0.02. CONCLUSIONS: We observed a low frequency (8%) of upper gastrointestinal tract complications after renal transplantation. There was no difference in the frequency of complications between patients on tacrolimus and those on cyclosporin based immunosuppression. Furthermore, the complication rates were similar in those that received omeprazole and those that received ranitidine as antiulcer prophylaxis, indicating the equivalence of these two agents in this setting.