ABSTRACT
It has been proposed that newborns' preferential orienting to faces is primarily controlled by a subcortical mechanism. As an index of subcortical, extrageniculate mediation, the asymmetry between the temporal and nasal hemifields was exploited. In Experiment 1, under monocular viewing conditions, newborns were presented with a pattern that had 3 blobs in the appropriate locations for the eyes and the mouth or a pattern that had an inverted position of the blobs. Results showed that newborns preferentially oriented to the facelike pattern only when it was presented in the temporal hemifield. In Experiment 2, both patterns had the blobs in the inverted position. For one pattern the blobs were black, and for the other they were striped. Newborns preferentially oriented to the striped blobs in either hemifield. The results support the hypothesis that in newborns, preference for facelike patterns reflects the activity of a subcortical mechanism.
Subject(s)
Attention/physiology , Discrimination, Psychological/physiology , Face , Pattern Recognition, Visual/physiology , Visual Pathways/growth & development , Analysis of Variance , Brain/growth & development , Fixation, Ocular/physiology , Humans , Infant, Newborn , Mesencephalon/growth & development , Models, Neurological , Neural Analyzers/growth & development , Retina/growth & development , Visual Fields/physiologyABSTRACT
The authors used the interferometrical method to determine the content and concentration of the proteins in the neuron cytoplasma of the III and V layer in the motor and visual areas of the brain cortex in rabbits in normal conditions and prolonged light deprivation (from the moment of birth up to 2 1/2 months). These data were accompanied by measurements of the neuron area. It was demonstrated that the absence of visual impulses leads to a morphochemical underdevelopment of the neurons in the visual cortex layers. Such underdevelopment was expressed in a decrease in the size of the neurons and protein content in the cytoplasma compared to the control group. In the neurons of the III and V layer of the motor cortex of the same animals there were changes of a compensatory character (an increase in the size of the neurons, content and concentration of proteins in the cytoplasma). In this respect the authors discuss the question of the influence of specific visual and other forms of impulsation on the morphochemical differentiation of neurons in the studied brain cortex.
Subject(s)
Nerve Tissue Proteins/metabolism , Neural Analyzers/metabolism , Sensory Deprivation , Vision, Ocular , Animals , Histocytochemistry , Motor Cortex/growth & development , Motor Cortex/metabolism , Neural Analyzers/growth & development , Rabbits , Visual Cortex/growth & development , Visual Cortex/metabolismABSTRACT
The influence of a corticofugal volley produced by single electrical stimulation of the visual projection cortical zone on the neuronal activity of LGB was studied in non-anaesthetized rabbits aged from three to thirty-five days. A coincidence was found between the time of appearance of nonspecific inhibitory corticofugal influences on the spontaneous activity of LGB neurons and the emergence of the first phasic-specific responses of the neurones of this level to a visual stimulus. It has been shown that the sensory flow at the LGB level can be controlled by non-specific inhibitory corticofugal influences at early periods of postnatal development. The appearance from the 15th day of life of specific responses to a corticofugal volley, including activation phases, leads to a greater complexity of the regulating Cortical influences on conduction of the afferent signal at the thalamic level. The data obtained are considered from the standpoint of integration of various levels of the visual analyser at different stages of ontogenesis.
