Self-injurious behavior: gene-brain-behavior relationships

This paper summarizes a conference held at the National Institute of Child Health and Human Development on December 6-7, 1999, on self-injurious behavior [SIB] in developmental disabilities. Twenty-six of the top researchers in the U.S. from this field representing 13 different disciplines discussed environmental mechanisms, epidemiology, behavioral and pharmacological intervention strategies, neurochemical substrates, genetic syndromes in which SIB is a prominent behavioral phenotype, neurobiological and neurodevelopmental factors affecting SIB in humans as well as a variety of animal models of SIB. Findings over the last decade, especially new discoveries since 1995, were emphasized. SIB is a rapidly growing area of scientific interest to both basic and applied researchers. In many respects it is a model for the study of gene-brain-behavior relationships in developmental disabilities.     

Time perspective, depression, and substance misuse among the homeless

Using the Zimbardo Time Perspective Inventory (ZTPI; P. G. Zimbardo & J. N. Boyd, 1999), the authors found that homeless people, in comparison with a control group, had a significantly more negative outlook concerning their past and present as evinced by high Past-Negative and Present-Fatalistic scores and low Past-Positive scores on the ZTPI. However, the homeless individuals were almost indistinguishable from control participants on measures of Present-Hedonism and Future thinking. The homeless individuals had significantly higher levels of depression, with 31 out of 50 (62%) reaching criteria for probable depression. However, this finding was unrelated to their atypical time perspective. There was no significant relation between substance misuse and time perspective. Despite their current difficulties, including depression and drug abuse, the homeless individuals maintained a propensity toward future thinking characterized by striving to achieve their goals.     

Inhibitory tagging at subsequently fixated locations: Generation of “inhibition of return” without saccade inhibition

In two experiments, an inhibitory tag was activated by a peripheral cue after which a saccade was made to either the cued or, with equal probability, the uncued location. Key press RTs were measured for detecting a target that then appeared, with equal probability, either at fixation or at an eccentric location. In Experiment 1, the peripheral cue onset 400 ms before the saccade instruction, and participants therefore were obliged to inhibit a saccade towards the cue. Detection was slower at the cued location whether it appeared at, or eccentric from, fixation. In Experiment 2, the peripheral cue onset after the instruction to make the saccade but before the eyes had moved. Inhibitory tagging was again observed for targets at fixation, but the effect was smaller than for eccentric targets. These findings confirm that withdrawal of attention from a cued location is not required to generate an inhibitory tag, and that the cued locus remains inhibited even if it is subsequently attended and a saccade made to fixate it. Moreover, saccade inhibition is not sufficient to account for inhibitory tagging, although it may also engender an independent inhibitory effect.     

A comparison of health behaviours in lonely and non-lonely populations

Loneliness can be defined as perceived social isolation and appears to be a relatively common experience in adults. It carries a significant health risk and has been associated with heart disease, depression and poor recovery after coronary heart surgery. The mechanisms that link loneliness and morbidity are unclear but one of the mechanisms may be through poor health beliefs and behaviours. The aims of this cross-sectional survey of 1289 adults were to investigate differences in health behaviours (smoking, overweight, BMI, sedentary, attitudes towards physical activity) in lonely and non-lonely groups. Lonely individuals were more likely to be smokers and more likely to be overweight - obese. The lonely group had higher body mass index scores controlling for age, annual income, gender, employment and marital status. Logistic regression revealed no differences in sedentary lifestyles. Lonely individuals were significantly less likely to believe it was desirable for them to lose weight by walking for recreation, leisure or transportation. The findings provide support for an association between health behaviours, loneliness and excess morbidity reported in previous studies.     

Changes in Behaviour and Body Weight Following a Single or Double Social Defeat in Rats

In a series of experiments, the consequences of a single and double social conflict on various behaviours and body weight in rats were studied. Animals were subjected to social defeat by placing them into the territory of an aggressive male conspecific for one hour, either once, or twice at the same time on two consecutive days. To assess the consequences of social defeat, three experiments were performed with independent groups of rats. In the first experiment, an open field test was performed two days after the last conflict. Locomotor activity was strongly reduced after social defeat. There were no differences between the single and double defeat group. To assess the effects of social defeat on subsequent social behaviour, a second experiment was performed in which experimental animals were confronted with an unfamiliar non-aggressive rat two days after a single or double conflict. Social defeat resulted in a reduction of social contact with the unfamiliar conspecific. There was no difference between the single and double conflict group. In the third experiment, the effects of social conflict on food intake, body weight and saccharine preference were measured. Food intake was not affected after a single conflict, but in the double conflict group food intake was decreased for several days. Body weight gain was decreased after both single and double social defeat. The decrease was stronger in the double conflict group. Water intake and saccharine preference were not significantly affected. This study revealed that social defeat in rats causes pronounced changes in various behaviours and body weight. Different aspects of behaviour are differentially affected by defeat with respect to the magnitude and time course of the changes induced. Moreover, different behavioural parameters are differentially sensitive to repetition of the stressor.