Operant serial feature-positive conditional discrimination with composite features and different topography responses

In a serial feature-positive conditional discrimination procedure the properties of a target stimulus A are defined by the presence or not of a feature stimulus X preceding it. In the present experiment, composite features preceded targets associated with two different topography operant responses (right and left bar pressing); matching and non-matching-to-sample arrangements were also used. Five water-deprived Wistar rats were trained in 6 different trials: X-R®Ar and X-L®Al, in which X and A were same modality visual stimuli and the reinforcement was contingent to pressing either the right (r) or left (l) bar that had the light on during the feature (matching-to-sample); Y-R®Bl and Y-L®Br, in which Y and B were same modality auditory stimuli and the reinforcement was contingent to pressing the bar that had the light off during the feature (non-matching-to-sample); A- and B- alone. After 100 training sessions, the animals were submitted to transfer tests with the targets used plus a new one (auditory click). Average percentages of stimuli with a response were measured. Acquisition occurred completely only for Y-L®Br+; however, complex associations were established along training. Transfer was not complete during the tests since concurrent effects of extinction and response generalization also occurred. Results suggest the use of both simple conditioning and configurational strategies, favoring the most recent theories of conditional discrimination learning. The implications of the use of complex arrangements for discussing these theories are considered.

Nasal CPAP in the delivery room for newborns with extremely low birth weight in a hospital in a developing country

The objective of this study was to determine the feasibility of the use of continuous positive airway pressure installed prophylactically in the delivery room (DR-CPAP), for infants with a birth weight between 500 and 1000 g in settings with limited resources. During 23 months, infants with a birth weight between 500 and 1000 g consecutively received DR-CPAP. A total of 33 infants with low birth weight were enrolled, 16 (48.5%) were females. Only 14 (42.4%) received antenatal corticosteroids and only 2 of those 14 (14.3%) infants weighing 500-750 g were not intubated in the delivery room, and apnea was given as the reason for intubation of these patients. Of the 19 infants in the 751-1000 g weight range, 9 (47.4%) were intubated in the delivery room, 6 due to apnea and 3 due to respiratory discomfort. For DR-CPAP to be successful, it is probably necessary for preterm babies to be more prepared at birth to withstand the respiratory effort without the need for intubation. Antenatal corticosteroids and better prenatal monitoring are fundamental for success of DR-CPAP.