Early-Life Polysensorial Stimulation and Nutrition: Topographic Levels of Susceptibility in the Rat Visual Cortex

Abstract

The effects of environmental-nutritional interactions upon the development of the visual cortex were studied in Sprague-Dawley albino rats during lactation (5–22 postnatal days). Morphometric evaluations were assessed by measuring layer V pyramidal neurons, under camera lucida. The Golgi-Cox-Sholl technique permits quantitative studies of neurons by the precipitation of metallic mercury at random, without any selectivity. Length and frequency of dendritic segments showed significant differences due to rearing, nutrition, and topographic localization. Early environmental enrichment exerted its maximal benefits in undernourished pups, the influences being highly prominent in the lateroventral sector of the cortical plate that receives conspicuous inputs during development. These findings may provide bases for the design of clinical strategies to palliate the adverse effects of undernourishment and sensory deprivation on brain development, since their effects seem to follow pari passu the topographic sequences of cortical morphogenesis.

Effects of Preweaning Polysensorial Enrichment upon Development of the Parietal Cortical Plate of Undernourished Rats: A Stereological Study

“…Such effect on neuronal development seems, however, to be relatively independent from corporal dimensions, as can be established by comparing data obtained in both parameters (independently) in Table I. Thus, pups that were reared in enriched environmental conditions displayed decreased corporal averages with increased geometrical arrangements and noteworthy territorial expansions of dendrites (Fernández et al, 1997.…”

“…In fact, previous studies have shown that animals submitted to undernutrition during the critical period of brain growth experienced a reduction of neuronal cytodifferentiation (Leuba & Rabinowicz, 1979;Cordero et al, 1993;Noback & Eisenman, 1981), while early polysensorial stimulation generated opposite effects to that induced by undernutrition: growth of the basal dendritic tree and increases in neuronal geometric complexity (Fernández et al, 1997, thereby reducing the neuronal density (Beaulieu & Colonnier, 1989). In particular, environmental enrichment accelerated the neuronal cytodifferentiation in sectors of high sensibility such as the lateral parietal cortex Inzunza et al), a feature that may be related to the early arrival of afferent signals coming from the enriched environment to the lateral sector that contains the representation of the face and vibrissae.…”

“…From day 2nd to 21st, pups in the enriched environment were exposed, without the mother, to three 20-min sessions per day of exploration in a 70x70x40 cm wire mesh cage provided with a large variety of objects for play and exploration, which were changed or rearranged daily (Fernández et al, 1997). These included running wheels, tunnels, ladders, sand boxes, balls, rattle, leafy plants, long grass, tree branches, sawdust, furry and rough surfaces, toys of different sizes and textures (wood, metals or plastic) and two elevated platforms along opposite sides of the cage, 16 cm above the level of the floor.…”

Densidad Neuronal en La Corteza Visual Primaria (Área 17), De Dos Especies De Roedores Silvestres

“…Evaluaciones morfométricas en las neuronas piramidales de la capa V, en ratas en período de lactancia (5-22 días postnatal), mostraron que el enriquecimiento del medioambiente y de las condiciones nutricionales, dió como resultado un aumento en el número de ramificaciones dendríticas. Este resultado fue más evidente en la porción latero-ventral de la corteza visual (Fernández et al, 1997). Estos autores, en últimos trabajos, encontraron una expansión territorial del campo dendrítico en neuronas observadas en la región lateral de la corteza parieto-occipital, de ratas sometidas a un enriquecimiento polisensorial temprano (2-22 días de edad) (Fernández et al, 2003).…”

Enduring behavioral effects of weaning-through-puberty cocaine dosing in the rat

“…have investigated possible lasting effects of cocaine administered during a period corresponding to human childhood and early adolescence. The central nervous system (CNS) retains developmental plasticity during this period, however; many reports indicate that a well-studied manipulation, environmental enrichment, produces changes in fine neuromorphology (e.g., Greenough, 1987), especially of systems developing at the time of enrichment (Fernandez, Adaro, Sanhueza-Tsusumi, Inzunza, & Bravo, 1997). This continued plasticity is part of the rationale for Witt's (1994) recommendation of assessing an animal model of adolescent use of another addictive drug, alcohol.…”