Functional maturation of the visual cortex during prenatal development of the cat

Conclusions

• 1. The first electrical responses to stimulation of the optic nerve arise in the occipital region of the contralateral cortex at the beginning of the second half of intrauterine development. At this period the EP have the appearance of slow triphasic waves of low amplitude.

• 2. In the later stages of development the EP become more stable and the amplitude of the negative phase rises sharply. The configuration of EP in the striate cortex 10–12 days before birth becomes more complex on account of the appearance of an initial short-latency negative wave, which develops against the background of the primary positive wave.

• 3. In the last week of intrauterine development and in kittens during the first days of life, EP in the specific visual area of the cortex (the lateral gyrus) consist of two negative waves, separated by a positive wave.

• 4. EP at all stages of ontogeny studied were recorded over almost the whole surface of the cortex of the contralateral hemisphere. From 7 to 10 days before birth two foci of maximal activity could be clearly distinguished. The first covered the central and caudal parts of the lateral gyrus, the second the central and more lateral part of the suprasylvian gyrus.