Neocortical connections in fetal cats

doi:10.1016/0168-0102(88)90040-5

Neuroscience Research

Volume 5, Issue 6, August 1988, Pages 513-543

https://doi.org/10.1016/0168-0102(88)90040-5 Get rights and content

Abstract

The major extrinsic projections to and from visual and auditory areas of cerebral cortex were examined in fetal cats between 46 and 60 days of gestation (E46–E60) using axonal transport of horseradish peroxidase either alone or in combination with tritiated proline. Projections to visual cortex from the dorsal lateral geniculate nucleus and lateral-posterior/pulvinar complex exist by E46, and those from the contralateral hemisphere, claustrum, putamen, and central lateral nucleus of the thalamus are present by E54–E56. In addition, cells in the medial geniculate nucleus project to auditory cortex by E55. At E54–E56 efferent cortical projections reach the contralateral hemisphere, claustrum, putamen, lateral-posterior/pulvinar complex and reticular nucleus of the thalamus. Cells in visual cortex also project to the dorsal and ventral lateral geniculate nuclei, pretectum, superior colliculus and pontine nuclei, and cells in auditory cortex project to the medial geniculate nucleus. Except for interhemispheric projections, all pathways demonstrated are ipsilateral, and projections linking cerebral cortex with claustrum, dorsal lateral geniculate nucleus and lateral-posterior/pulvinar complex are reciprocal. The reciprocal projections formed with the dorsal lateral geniculate nucleus, lateral-posterior/pulvinar complex and the claustrum show a greater degree of topological organization compared to the projections formed with the contralateral hemisphere and superior colliculus, which show little or no topological order. Therefore, the results of the present study show that the major extrinsic projections of the cat's visual and auditory cortical areas with subcortical structures are present by the eighth week of gestation, and that the origins and terminations of many of these projections are arranged topologically.

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Groups of young adult cats with a left hemineodecortication at postnatal (P) ages (in days) 5–15 (P10), 30 (P30), 60 (P60), 90 (P90), 120 (P120) and in adulthood, were used to measure the volume of the thalamus, bilaterally, and of the remaining neocortex (right hemisphere). The same subjects were employed for the behavioral studies reported in the preceding paper. There was a bilateral, age-dependent, thalamic volume decrease. Ipsilateral to the resection, the thalamic shrinkage was the largest for the adult-lesioned cats (by 56.7%) and it was the smallest for the P30 group (43.3%), with a tendency towards a greater atrophy as the age at lesion increased. A similar pattern of atrophy was seen for the contralateral thalamus but the volume reduction was much less pronounced such that it was significant only for the four older age-at-lesion groups (ranging from 18.2% to 11.2% for the P120 and P90 groups respectively). Once again, the shrinkage was the smallest for the P30 group (5.3%). The remaining neocortex also shrunk in these animals, but the volume decrease was significant only for the adult-lesioned (17.8%) and the P120 group (15.4%), while the P30 group had practically no shrinkage (2.4%). The frontal cortex had no atrophy or it was minimal but the shrinkage gradually increased caudally such that all lesioned groups had some size reduction of the occipital cortex. The present results, together with the main conclusion of the preceding paper, indicate that there is a critical maturation period (CMP) of reduced forebrain vulnerability to neocortical injury which, in cats, tends to end between 30 to 60 days postnatally. The implications for developmental brain damage in other higher mammal species as well as the possible morphological ontogenetical underpinnings of this period are discussed.
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Research reportNeocortical connections in fetal cats

Abstract

Brain Res.

Neurosci. Res.

Neurosci. Lett.

Neuroscience

Brain Res.

Dev. Brain Res.

Brain Res.

Neuroscience

Brain Res.

Technical considerations on the use of horseradish-peroxidase as a neuronal marker

Neuroscience

The prenatal development of some of the visual pathways in the cat

J. Comp. Neurol.

Development and plasticity of visual interhemispheric connections

Organization of immature intrahemispheric connections

J. Comp. Neurol.

Extrinsic visual and auditory cortical connections in the four-day-old kitten

J. Comp. Neurol.

The development of synapses in the visual system of the cat

J. Comp. Neurol.

Transient projections from the fronto-parietal and temporal cortex to areas 17, 18 and 19 in the kitten

Exp. Brain Res.

Autoradiographic tracing of developing subcortical projections of occipital region in fetal rabbits

J. Comp. Neurol.

Postnatal development of auditory callosal connections in the kitten

J. Comp. Neurol.

Development of neuronal selectivity in primary visual cortex of cat

Physiol. Rev.

Development and plasticity of primate frontal association cortex

Cell migrations to the isocortex in the rat

Anat. Rec.

An autoradiographic study of the subcortical projections of the rabbit striate cortex in the adult and during postnatal development

J. Comp. Neurol.

General organization of callosal connections in the cerebral cortex

Postnatal shaping of callosal connections from sensory areas

Exp. Brain Res.

The organization of immature callosal connections

J. Comp. Neurol.

Maturation of visual callosal connections in visually deprived kittens: a challenging critical period

J. Neurosci.

The ontogeny of the distribution of callosal projection in rat parietal cortex

J. Comp. Neurol.

Ontogenetic changes in the projections of neocortical neurons

J. Neurosci.

Retrograde axonal transport and the demonstration of non-specific projections to the cerebral cortex and striatum from thalamic intralaminar nuclei in the rat, cat and monkey

J. Comp. Neurol.

Distribution of the neurons of origin of the great cerebral commissures in the cat

Anat. Embryol.

Development of the dorsal lateral geniculate nucleus of the cat

J. Comp. Neurol.

Postnatal development of the geniculocortical projection in the cat: electrophysiological and morphological studies

Exp. Brain Res.

Research report
Neocortical connections in fetal cats