Developmental visual perception deficits with no indications of prosopagnosia in a child with abnormal eye movements

Abstract

Visual categories are associated with eccentricity biases in high-order visual cortex: Faces and reading with foveally-biased regions, while common objects and space with mid- and peripherally-biased regions. As face perception and reading are among the most challenging human visual skills, and are often regarded as the peak achievements of a distributed neural network supporting common objects perception, it is unclear why objects, which also rely on foveal vision to be processed, are associated with mid-peripheral rather than with a foveal bias. Here, we studied BN, a 9 y.o. boy who has normal basic-level vision, abnormal (limited) oculomotor pursuit and saccades, and shows developmental object and contour integration deficits but with no indication of prosopagnosia. Although we cannot infer causation from the data presented here, we suggest that normal pursuit and saccades could be critical for the development of contour integration and object perception. While faces and perhaps reading, when fixated upon, take up a small portion of central visual field and require only small eye movements to be properly processed, common objects typically prevail in mid-peripheral visual field and rely on longer-distance voluntary eye movements as saccades to be brought to fixation. While retinal information feeds into early visual cortex in an eccentricity orderly manner, we hypothesize that propagation of non-foveal information to mid and high-order visual cortex critically relies on circuitry involving eye movements. Limited or atypical eye movements, as in the case of BN, may hinder normal information flow to mid-eccentricity biased high-order visual cortex, adversely affecting its development and consequently inducing visual perceptual deficits predominantly for categories associated with these regions.

Differentiation of Types of Visual Agnosia Using EEG

“…Visual agnosia (‘agnosia’ for short hereafter) is a highly heterogenous disorder that results from damage to a premorbidly normal region or regions of the cortical visual system, and is often referred to as ‘acquired’ visual agnosia. Agnosia can also result from brain damage that occurs in young children and is termed acquired ‘developmental’ agnosia (for review, see [3,4]) and can even be present in cases of ‘congenital’ agnosia in which behavior is impaired presumably from birth but without obvious neurological damage (for example, see [5]). The manifestation of deficits in acquired agnosia in adults (and perhaps in the other variants too) varies depending on the size and location of the lesion [6].…”

Positive and negative facial valence perception are modulated differently by eccentricity in the parafovea: Replication from KDEF to NimStim

“…Specifically, while the only inclusion criteria were age range (18-35 years) and normative or corrected to normative vision, as in our pervious study, here too our cohort was limited to young adults from middle-to-high socioeconomic background, mostly educated (see demographics) and in a western industrialized democratic society since these are the only people that enrolled. Therefore, generalization to other populations is yet to be established 14,52,62,[74][75][76][77][78] . However, even given all these potential limitations and possibly additional ones, we were able to successfully replicate our earlier findings that eccentricity modulates valence perception and affects negative and positive valence in a differential manner.…”