Design of a data-acquisition system for monitoring sleep organization in preterm infants.

A portable data-acquisition system suitable for long-term noninvasive monitoring of physiologic and behavioral variables in preterm infants is described. The system includes two video cameras, a video screen-splitter and amplifier, a time-lapse video recorder, a microphone, a force-responsive transducer, an analog signal conditioner, and two microcomputers. One microcomputer, located in the neonatal intensive care unit (NICU) acquires electrophysiologic signals and preprocesses data in real time, during a continuous 48-hour session. After each session, the data file is transferred by telephone line to the other microcomputer, located in a laboratory, for editing, reduction, display, and final analysis. This arrangement enables noninvasive and nonintrusive monitoring, which is crucial for long-term recording of sleep-wake state organization of preterm infants.

Lateralization of spatial preference in the female rat.

Female rat pups were either left undisturbed in infancy and raised in lab cages or were handled in infancy and raised in enriched environments. In adulthood, animals underwent brain surgery consisting of: 1) a right neocortical ablation, 2) a left neocortical ablation, 3) a sham operation, or 4) no surgery. After recovering, they were tested for the initial direction of movement (left or right) in the open field. Nonhandled intact females were biased to move leftward indicating an asymmetrical brain organization. The intact handled-enriched group was unbiased. The right and left lesions caused the animals to move ipsilateral to the lesion, but there was no difference in the magnitude or response in either early experience group. Thus, early experience in the female rat has a different effect then in the male, and the nature of the brain organization in the two sexes is markedly different.

Handling in infancy, brain laterality and muricide in rats.

Rats were handled for the first 20 days of life or were not disturbed. Between 21 and 50 days approximately half of each group was reared in enriched environments while the remainder was group reared in laboratory cages. When adult, four males from each litter received a right neocortical ablation, a left ablation, a sham operation, or no surgery. They were tested for mouse killing between 9-12 months of age. Intact non-handled controls without enrichment experience had a 96% incidence of muricide. Handling and enrichment treatments independently and additively reduced the rate of mouse killing in animals with intact brains. There was no evidence of brain laterality for animals which received no extra stimulation in early life. In contrast, the brains of handled animals were lateralized, with the left lesion group having a higher killing response than the right. Non-lesioned handled rats had approximately the same level of muricide as those with a right hemisphere lesion, leading to the inference that in the intact brain the left hemisphere inhibits the killing response of the right.

Stimulation in infancy facilitates interhemispheric communication in the rabbit.

Experimental rabbits were stimulated in infancy by being handled, while controls were undisturbed. After reaching adulthood, the animals were tested for activity in an open field with: (i) the right eye occluded; (ii) the left eye occluded; and (iii) neither eye occluded. For rabbits not stimulated in infancy, the correlation between activity scores for the left eye and right eye occlusion conditions was not significant (r = 0.115). In contrast, the correlation was highly significant for handled animals (r = 0.829). The results of the nonhandled group are consistent with other research which has failed to find interocular transfer of visual information, while the significant interhemispheric correlations within the handled group are consistent with prior findings obtained with rats. The results suggest that stimulation in infancy may act to facilitate the functional competence of the corpus callosum.

Handling in infancy, taste aversion, and brain laterality in rats.

Rats were handled for the first 20 days of life or were not disturbed. When adults, they were trained to approach and drink from a bottle containing sweetened milk and were then given an injection of lithium chloride to induce a taste aversion conditioned emotional response. Others were injected with physiological saline. Rats within each of the treatment groups were then randomly assigned to 4 surgical procedures: removal of the right or left neocortex; sham surgery; or no surgery. Postoperatively, they were tested for retention of taste aversion by presenting the sweetened milk and recording the amount consumed. The initial consummatory behavior was very low (showing retention of the aversion) and increased over time. There were no differences in the reacquisition curves of the non-handled groups which had received lithium chloride. The curves of the handled groups did differ: thos with an intact right hemisphere (left neocortical lesion) had the lowest asymptote, followed by the group with an intact left brain, while those with intact whole brains consumed the greatest amount of milk. In the groups given an injection of physiological saline, those with a left hemisphere lesion consumed less milk than the other groups, regardless of their early handling experience. The data show: (1) that the rat's brain is lateralized, with the right hemisphere being preferentially involved in conditioned emotional behavior; and (2) that handling in infancy makes the left hemisphere less suceptible to conditioned fear.

Brain and behavioral asymmetries for spatial preference in rats.

Rats were handled daily for 3 min between birth and weaning, or were nonhandled controls. When adult, 4 males from each litter received a right neocortical ablation, a left ablation, a sham operation, or no surgery. A month later all animals were tested in the open field for 4 days, and their initial direction of movement from the starting square (whether right or left) was recorded. Non-handled rats with intact brains (sham-operated and no-surgery groups pooled) had a mean directionality score near zero, thus indicating no right-left spatial preference. However, non-handled animals without a left hemisphere were significantly more biased in going to the ipsilateral side than were their siblings with right-brain ablations. Thus, in non-handled animals behavioral symmetry in making spatial choices is due to balanced brain asymmetry, in which the right hemisphere biases the animal to move leftward while the left hemisphere acts to inhibit this response. In contrast, intact handled rats had a significant preference to go to the left, thus suggesting that in handled animals the right hemisphere controls spatial preference.