Abstract
After been exposed to the visual input, in the first year of life, the brain experiences subtle but massive changes apparently crucial for communicative/emotional and social human development. Its lack could be the explanation of the very high prevalence of autism in children with total congenital blindness. The present theory postulates that the superior colliculus is the key structure for such changes for several reasons: it dominates visual behavior during the first months of life; it is ready at birth for complex visual tasks; it has a significant influence on several hemispheric regions; it is the main brain hub that permanently integrates visual and non-visual, external and internal information (bottom–up and top–down respectively); and it owns the enigmatic ability to take non-conscious decisions about where to focus attention. It is also a sentinel that triggers the subcortical mechanisms which drive social motivation to follow faces from birth and to react automatically to emotional stimuli. Through indirect connections it also activates simultaneously several cortical structures necessary to develop social cognition and to accomplish the multiattentional task required for conscious social interaction in real life settings. Genetic or non-genetic prenatal or early postnatal factors could disrupt the SC functions resulting in autism. The timing of postnatal biological disruption matches the timing of clinical autism manifestations. Astonishing coincidences between etiologies, clinical manifestations, cognitive and pathogenic autism theories on one side and SC functions on the other are disclosed in this review. Although the visual system dependent of the SC is usually considered as accessory of the LGN canonical pathway, its imprinting gives the brain a qualitatively specific functions not supplied by any other brain structure.
Highlights
Autism spectrum disorder (ASD) is not a disease; it is a syndrome with hundreds of genetics and non-genetics etiologies and with broad clinical manifestations
Relevant to ASD theories is the finding in mammals of several groups of specialized superior colliculus (SC) cells, for example, neurons in visual layers with the shortest latencies throughout the brain to respond to faces (25-ms) (Nguyen et al, 2014); Visuomotor neurons in intermediary layers (Krauzlis et al, 2013) that allow the enigmatic transformation of visual images into motor commands; Multisensory neurons, specially trained to respond to space-temporal congruent stimuli (Stein et al, 2009); and Disengagement neurons, essential to change focus (Ngan et al, 2015). These findings strongly suggest that the SC is highly involved in pivotal operations of attention orienting: recognition of a new relevant clue, disengagement, visuomotor transformation for shifting, and new engagement
The timing of postnatal biological disruption parallels the timing of clinical manifestation
Summary
Centro Privado de Neurología y Neuropsicología Infanto Juvenil WERNICKE, Córdoba, Argentina. It is a sentinel that triggers the subcortical mechanisms which drive social motivation to follow faces from birth and to react automatically to emotional stimuli. Through indirect connections it activates simultaneously several cortical structures necessary to develop social cognition and to accomplish the multiattentional task required for conscious social interaction in real life settings. Genetic or non-genetic prenatal or early postnatal factors could disrupt the SC functions resulting in autism. The timing of postnatal biological disruption matches the timing of clinical autism manifestations. Astonishing coincidences between etiologies, clinical manifestations, cognitive and pathogenic autism theories on one side and SC functions on the other are disclosed in this review.
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