Biomedical subjects

T R Marshall

Publications and source records attributed to T R Marshall.

16 recordsLinked to original sources

PubMed1995

Effects of rearing condition on activity-induced weight loss.

This study evaluated the effects of differential rearing conditions on a rat protocol for various human syndromes. Subjects were 26 male Sprague-Dawley rats, 24 days old at the start of the experiment, matched according to weight, and randomly assigned to an isolation- or group-reared (4 rats/cage) condition. At 60 days of age (273 +/- 13 g), subjects were individually housed in cages allowing access to running wheels. Weight loss was produced through voluntary exercise and restricted food access. Animals in the isolation-reared condition lost weight at a faster rate and had heavier relative thymus weights than those in the group-reared condition. Animals in both conditions ran equivalent distances and ate equivalent amounts of food. The data show that postweaning rearing conditions impact the interpretation of behavioral and physiological outcomes of animal models. The results implicate a shift from maternal regulation of pup physiological and behavioral systems to the broader social niche.

Aging↗

PubMed1995

Frontal activation asymmetry and social competence at four years of age.

The pattern of frontal activation as measured by the ongoing electroencephalogram (EEG) may be a marker for individual differences in infant and adult disposition to respond with either positive or negative affect. We studied 48 4-year-old children who were first observed in same-sex quartets during free-play sessions, while making speeches, and during a ticket-sorting task. Social and interactive behaviors were coded from these sessions. Each child was subsequently seen 2 weeks later when EEG was recorded while the child attended to a visual stimulus. The pattern of EEG activation computed from the session was significantly related to the child's behavior in the quartet session. Children who displayed social competence (high degree of social initiations and positive affect) exhibited greater relative left frontal activation, while children who displayed social withdrawal (isolated, onlooking, and unoccupied behavior) during the play session exhibited greater relative right frontal activation. Differences among children in frontal asymmetry were a function of power in the left frontal region. These EEG/behavior findings suggest that resting frontal asymmetry may be a marker for certain temperamental dispositions.

Affect↗

PubMed1991

Rhythmic organization of neonatal heart rate and its relation to atypical fetal growth.

The rhythmic organization underlying long-term heart rate variability was examined in 36 newborn infants. Heart rate was registered every 30 s for 2 continuous hr while infants rested in a temperature-controlled isolette. Spectrum analysis of the time-series of the 240 observations detected rhythmically organized changes in the heart rates of 33 of the 36 infants. Thirty of the 33 infants showed a basic rhythm at 1.5 +/- .5 cycles per hr (one cycle every 30 to 60 min). While 9 infants showed this single cycle in behavioral activity, 24 infants showed additional cycles at a wide range of faster frequencies. Infants with signs of atypical fetal growth less often showed evidence of these multiple cycles, had reliably fewer cycles in heart rate, and had a marginally lower power in their basic cycle than infants with typical patterns of fetal growth. Infants with multiple cycles in the power spectra, independent of fetal growth group, were more often observed in Alert and Active Alert behavioral states and less often in Active Sleep than comparison infants. Results indicate that 1) heart rates of newborn infants show evidence of the 30- to 60-min cycle characteristic of the Basic Rest-Activity Cycle found in other behaviors, and 2) the complexity of behavioral rhythms may be affected by prenatal malnutrition. Viewed within a dynamical systems approach to development, results suggest that the complexity of rhythms in behavior may reflect the complexity of behavioral organization.

Adult↗

PubMed1976