The Effect of Perceptual Learning on Face Recognition in Individuals with Central Vision Loss

Abstract

Purpose: To examine whether perceptual learning can improve face discrimination and recognition in older adults with central vision loss.

Methods: Ten participants with age-related macular degeneration (ARMD) received 5 days of training on a face discrimination task (mean age, 78 ± 10 years). We measured the magnitude of improvements (i.e., a reduction in threshold size at which faces were able to be discriminated) and whether they generalized to an untrained face recognition task. Measurements of visual acuity, fixation stability, and preferred retinal locus were taken before and after training to contextualize learning-related effects. The performance of the ARMD training group was compared to nine untrained age-matched controls (8 = ARMD, 1 = juvenile macular degeneration; mean age, 77 ± 10 years).

Results: Perceptual learning on the face discrimination task reduced the threshold size for face discrimination performance in the trained group, with a mean change (SD) of -32.7% (+15.9%). The threshold for performance on the face recognition task was also reduced, with a mean change (SD) of -22.4% (+2.31%). These changes were independent of changes in visual acuity, fixation stability, or preferred retinal locus. Untrained participants showed no statistically significant reduction in threshold size for face discrimination, with a mean change (SD) of -8.3% (+10.1%), or face recognition, with a mean change (SD) of +2.36% (-5.12%).

Conclusions: This study shows that face discrimination and recognition can be reliably improved in ARMD using perceptual learning. The benefits point to considerable perceptual plasticity in higher-level cortical areas involved in face-processing. This novel finding highlights that a key visual difficulty in those suffering from ARMD is readily amenable to rehabilitation.

Figure 1.

Experimental design including pre- and post-test measurements and face discrimination task training (days 2–6).

Figure 2.

Left retina (A) and visual fixation area (B) of trained participant SC during microperimetry assessment. The cyan dots in B indicate fixation locations throughout the test, with the smaller purple ellipse signifying retinal stability for 63% of the test. (C) The participant's PRL; the pink dot illustrates the average retinal fixation locations during the first 10 seconds of the test, and the cyan dot illustrates the average PRL based on average fixations throughout the test. (D) The participant's retinal sensitivity map and the center of the optic nerve (the green dot on the left). The orange dots illustrate the least sensitive retinal areas, and the green dots illustrate the most sensitive regions.

Figure 3.

An example of a single XAB discrimination task trial. Participants fixated their PRL on the center of the fixation cross, present at the beginning of the trial and between stimuli. Participants were required to judge which of the last two images matched the first image they saw. When participants verbally expressed their choice (“A” or “B”), the experimenter pressed the corresponding button to elicit auditory feedback (correct responses, high-pitched tone; incorrect responses, low-pitched tone) and the next trial. The original face stimuli are available online at https://iuvislab.sitehost.iu.edu/IUVISIONLAB/publications.html.

Figure 4.

(A) An individual learning function for the discrimination task for participant SC, demonstrating typical improvement in performance across session and from pre- to post training. (B) Learning data illustrating the mean face size that was able to be discriminated by participants in each group over the training sessions. (C) Normalized pre- and post-training threshold learning data for each group. A decreasing face size/threshold indicates improved performance. Error bars represent ±1 SE.

Figure 5.

Average size at which participants were able to recognize famous faces with which they were already familiar, shown for both groups in pre- and post-training sessions. Error bars represent ±1 SE.

Figure 6.

(A) Pre- and post-training average fixation areas for each participant measured using the MAIA. Three participants were excluded from this analysis due to problems imaging their optic disc. Most participants showed no change from pre- to post-training; those who did showed no systematic pattern (trained: MV, WB, RT), indicating some individual variability. (B) Pre- and post-training average eccentricity of the PRL for each participant relative to the anatomical fovea. Two participants (trained: DB; control: AS) showed a relatively large shift in PRL. The 1:1 line is plotted in both figures. Retinal maps for individual participants’ fixation stability and PRL are provided in Supplementary Figure S2.

Figure 7.

Average logMAR visual acuity measured at pre- and post-training sessions. Acuity estimates were stable for both training and control groups. Error bars represent ±1 SE.