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Biomedical subjects

R L Freedland

Publications and source records attributed to R L Freedland.

6 recordsLinked to original sources
PubMed1996

Arousal-modulated attention at four months as a function of intrauterine cocaine exposure and central nervous system injury.

CNS-compromised neonates are poor modulators tending to prefer less stimulation in all arousal conditions. Cocaine-exposed neonates also are poor modulators but tend to prefer more stimulation in all arousal conditions. Infants (N = 359, M = 4 months) were divided into 6 CNS injury groups and 1 cocaine-exposed, non-CNS-injured group and tested in three arousal conditions: less aroused (after feeding), more around-endogenous (before feeding), and more aroused-exogenous (after feeding with additional stimulation prior to each trial). Infants with CNS injuries still showed some degree of influence of arousal on attention that was now similar to that seen in normal neonates and 1-month-olds, while cocaine-exposed infants, 4-month-old normal and mild or moderate CNS-injury infants did not.

Arousal↗
PubMed1989

The detection of slow stimulus movement in 2- to 5-month-olds.

Preferences for moving over static bars were assessed in 8-, 16-, and 20-week-old human infants. The display consisted of two adjacent horizontal bars one of which moved with one of four velocities (0.70, 1.4, 2.8 or 5.6 degrees/s) through one of four distances (11, 22, 44, or 88 arcmin) before reversing and traveling in the other direction at the same velocity. No significant preferences for motion were obtained at 8 weeks. At both 16 and 20 weeks of age, however, preferences for motion were determined exclusively by the velocity of the movement and were unaffected by the excursion of the bar. The minimum velocities that elicited significant preferences for motion were 5.08 degrees/s and 2.32 degrees/s at 16 and 20 weeks of age, respectively. The more attentive 20-week-olds, however, showed significant preferences for motion above a velocity of approximately 1.8 degrees/s. The addition of static reference bars had little influence on these preferences for motion in 20-week-olds; preferences were again related exclusively to the velocity of the bar's movement. The results are discussed in terms of the development of motion-sensitive mechanisms within the visual system.

Acceleration↗
PubMed1987

Detection of stimulus motion in 5-month-old infants.

Five-month-old infants were tested by the method of preferential looking for discrimination between a pattern undergoing oscillating apparent motion and an identical static pattern. Sensitivity to small spatial displacements was evident at temporal frequencies of 8 and 16 Hz. Preference for the moving display was related independently to the temporal frequency of oscillation and the magnitude of the spatial displacement. Preferences for the moving display increased asymptotically across spatial displacements from 11 to 89 arc min. Preferences peaked between temporal oscillation frequencies of 8 and 16 Hz. Preference was not related to the ratio of these two variables--velocity. The minimum displacement threshold of 7.36 arc min was found to depend on the size of the elements in the pattern and on the temporal frequency of oscillation. The results demonstrate that motion-sensitive mechanisms responsive to small spatial displacements are present at 5 months of age.

Attention↗
PubMedDate not supplied

Motion-based detection by 14-week-old infants.

Three experiments using standing wave stimuli with 14-week-old human infants are reported. Two competing hypotheses regarding the detection of these standing wave line stimuli were tested in these studies. Amplitude-based (positional) detection was contrasted with speed-based (motion) detection. Temporal oscillation frequencies of 0.15, 0.30, 0.60 and 1.20 Hz were used. The detectability of a standing wave of fixed amplitude was influenced significantly by the temporal frequency of the oscillation. By inference, the results of the three experiments supported the motion-based detection hypothesis.

Humans↗