Facial blindsight

Abstract

Blindsight denotes unconscious residual visual capacities in the context of an inability to consciously recollect or identify visual information. It has been described for color and shape discrimination, movement or facial emotion recognition. The present study investigates a patient suffering from cortical blindness whilst maintaining select residual abilities in face detection. Our patient presented the capacity to distinguish between jumbled/normal faces, known/unknown faces or famous people's categories although he failed to explicitly recognize or describe them. Conversely, performance was at chance level when asked to categorize non-facial stimuli. Our results provide clinical evidence for the notion that some aspects of facial processing can occur without perceptual awareness, possibly using direct tracts from the thalamus to associative visual cortex, bypassing the primary visual cortex.

Keywords: anton’s syndrome; blindsight; consciousness; face; self recognition.

Figure 1

Axial CT scan performed 6 weeks after stroke reveals right parieto-occipital and left occipital lesions.

Figure 2

Visual assessment Showed impaired abilities in (A) shape and (B) object discrimination. (C) In contrast, A.M. was able to distinguish between jumbled and normal faces. (D) He was also able to distinguish between photographs of sportsmen, politicians, famous actors or unknown people and (E) to differentiate “known/unknown” faces of therapists from his and other medical departments. (F) He was also able to discriminate between fearful and neutral faces but (G) not when emotions were presented in other contexts.

Figure 3

Results of visual assessment. The results of all tasks involving faces were significantly above chance whereas those without faces were at chance level. *p < 0.05.