Measuring the Impact of Visual Impairment on Face Perception: A Combined Behavioural and Haemodynamic Approach

Ref: SHLS20025

Faces contain a wealth of information: a brief glimpse is typically sufficient to recognise a familiar face or interpret a facial expression. To process this information, humans have evolved several, high-level brain regions which are specialised for face perception.1

Due to the hierarchical nature of human vision, however, face perception also requires input from lower-level visual areas (e.g. retina, visual cortex). For example, optical blur reduces sensitivity to face identity, even when face-specific brain regions are intact.2 Further, patients with retinal diseases, such as age-related macular degeneration (AMD), report difficulty with recognising faces and interpreting facial expressions.3

This project aims to investigate the effect of visual impairment on face perception and establish the relationship between this functional deficit and modified patterns of neural activity.

We will employ novel, computer-based tests, recently developed in our lab, which accurately measure both face identity discrimination and facial expression recognition ability.4 Simultaneously, we will use functional near infrared spectroscopy (fNIRS) to obtain measurements of blood oxygenation across the occipital, temporal and parietal cortices. fNIRS facilitates measurement of a haemodynamic response to visual stimulation which provides insight into neural activity.5
We will first obtain measurements of face perception (computer-based tests) and associated patterns of cortical oxygenation (fNIRS) in participants with healthy vision. This will reveal the typical haemodynamic response associated with face perception.

We will then investigate the effect of systematic degradation of low-level vision on both face perception (measured behaviourally) and the associated haemodynamic response. Simulating visual impairment in participants with healthy vision will provide insight into the impact of visual impairment when patients are unadapted to this deficit.

Finally, we will measure face perception ability and linked cortical blood flow in patients with long-standing AMD. This will determine if the visual system demonstrates adaptation to the impoverished visual input associated with ocular disease.