The role of attention in developmental plasticity.

The development of suppression amblyopia in strabismic humans suggests that experience-dependent maturation of sensory functions is gated by attentional mechanisms. Evidence from animal experiments is in favour of this interpretation. Retinal signals support the development of normal receptive fields in the visual cortex of kittens only when the kittens are alert and attend to these signals. Lesion and stimulation studies in kittens suggest that ascending projections from the mesencephalic reticular formation and from the medial thalamic nuclei contribute to the gating of developmental plasticity. It is proposed that this gating is achieved through modulatory control of dendritic depolarization. Disfacilitation of those cortical neurones, which relay activity from the deviated eye could thus effectively block experience-dependent modifications in the respective circuits and lead to the amblyopic deficits.