Early prenatal development of cortical surface responses to visual stimuli in sheep

摘要: Abstract Cortical surface responses to electrical stimulation of the optic nerve were recorded in sheep fetuses between 55 and 124 days gestation (term 145 days). The cortical response obtained youngest was a long-latency surface-positive wave, followed by small negativity. Later during development negativity increased amplitude dominated response. This early developmental pattern visual similar that somesthetic On basis findings on maturation structure function cortex genesis is discussed. hypothesis put forward that, at its earliest appearance, positive wave predominantly reflecting synchronous depolarization developing corticopetal terminals later arises from summation excitatory postsynaptic potentials deep-seated neurons. considered reflect activation neural elements superficial neocortex. At about 98 fetal age short-latency component appeared It suggested this mediated through specific pathways, whereas earlier-appearing be via unspecific projection. During succeeding two components apparently coalesced build up positive-negative containing all adult form.