Overlap of retinal and prestriate cortical pathways in the primate pretectum.

Connections between the pretectum and prestriate visual cortex were examined following injection of HRP into area V4 of Macaca nemestrina monkeys. Orthograde label was found in nucleus olivarius (NO) and the sublenticular (SL) regions while retrogradely labeled neurons were present in the nucleus of the optic tract (NOT). Following injection of [3H]proline into one eye, 3 pretectal zones of retinal input were seen: NO, SL and the posterior pretectal region (PPR). These results indicate that NO and SL may be sites for retinal and cortical pathway interaction in primate pretectum.

Hypertrophy of neurons in dorsal lateral geniculate nucleus following striate cortex lesions in infant monkeys.

Monkeys whose left striate cortex had been removed in infancy received bilateral injections of horseradish peroxidase (HRP) into the prelunate gyrus (PLG) prestriate cortex. Scattered large neurons in the dorsal lateral geniculate nucleus were retrogradely labeled in both hemispheres. On the lesioned side, the HRP-labeled cell bodies were 58% larger in area, showing an overall increase in soma size and complexity of dendritic field, suggesting a hypertrophy of the geniculate-PLG pathway following a neonatal striate cortex lesion.

Age correlated differences in the amount of retinal degeneration after striate cortex lesions in monkeys.

We have studied transneuronal retrograde cell degeneration in the monkey retina after striate cortex removal. We find that the amount of ganglion cell degeneration depends on the age of the monkey at the time of lesion when the survival period is held constant. Monkeys lesioned between 2 and 15 months of age showed up to 80% ganglion cell loss after a 1 year survival period, whereas adults surviving for 1 year showed only a 15% loss.

Developmental changes in visual orienting behavior to featural versus structural information in the human infant.

Ten male infants, 3--4 months old, and 10 male infants, 6--7 months old, were habituated to a visual stimulus composed of both specific featural and structural information. After habituation, orienting magnitude (dishabituation) to changes in feature with structure controlled versus changes in structure with feature controlled was used as a means of measuring the infant's processing capacity. Results indicate that younger and older infants were habituated over the habituation trials but that younger and older infants differed significantly in dishabituation to changes in structure and feature information. The present findings support the hypothesis that feature and structure information are both independently important to visual processing in the human infant.

WAIS performance for different age groups of hypertensive and control subjects during the administration of a diuretic.

This study examined the effects of age and hypertension on WAIS performance. Previous studies have reported that hypertension adversely affects cognitive functioning, but few have considered the influence of hypertension on discrete age groups. Hypertension was found to be negatively associated with WAIS Verbal scores for younger (21 to 39 years) but not older (45 to 65 years) subjects. Further, younger subjects attained higher WAIS Performance scores than did older subjects. Medication history was not associated with performance levels for hypertensives, nor was performance of controls influenced by whether or not they were tested while on a diuretic. When WAIS Performance scores were analyzed for subjects matched on WAIS Verbal scores across age (21 to 39 vs 45 to 65 years) and blood pressure (normotensive vs hypertensive), a significant age by blood pressure interaction was found. The effect of blood pressure on Performance scores was found to be greater for younger than for older subjects. The association between plasma renin activity (PRA) level and WAIS Performance scores was also examined. Contrary to previous findings PRA was not related to Performance scores. The results are discussed in the context of previous hypertension research and their implications for comparisons across age levels.