Development of the 24-h rest-activity pattern in human infants

The development of the 24-h rest-activity pattern was investigated in human infants under naturalistic conditions as assessed by continuous actigraphy. Seven infants and their mothers were recorded for 4 (n=1), 6 (n=5) and 12 months (n=1) after birth. Periodogram analysis of rest-activity data was performed over consecutive 10-day intervals. A weak 24-h rest-activity pattern was already present in some infants during the newborn period. The magnitude of the 24-h component in individual periodograms increased across the first months following a saturating function. The time constants of fitted saturating exponential functions--reflecting the rate of development of the 24-h pattern--ranged from 49 to 110 days (n=6) indicating a large interindividual variability. Furthermore, intraindividual variation was observed; the magnitude of the 24-h rest-activity component showed fluctuations around the trend. Miniaturized actigraphs are ideal tools for long-term longitudinal monitoring of rest-activity behavior in infants.     

New methods in ambulatory blood pressure monitoring: Interactive monitoring and detection of posture and movement patterns

Psychophysiological monitoring can be used to assess emotional reactivity in cardiovascular measures. Since blood pressure (BP) variability in daily life is primarily caused by physical activity, metabolic and nonmetabolic effects are confounded. A newly developed method of multiple accelerometry allows for the control of such unwanted variances by continuously detecting posture, general activity, and distinct movement patterns. Contingent on episodes of additional heart rate (AHR), an indicator of emotional reactivity, BP measurements can be triggered and participants prompted to enter their current mood in a handheld PC. To evaluate both new methods for BP research, we performed 24-h ambulatory monitoring with 40 normotensive student participants, an evaluation designed to include standard settings for a controlled comparison (library vs. cinema). Findings indicated that the group at the cinema showed higher values of AHR, but group differences in BP were not observed. On the whole, such multiple accelerometry and interactive monitoring appear to be useful methods in behavior research.     

Risk assessment behaviors associated with corticosterone trigger the defense reaction to social isolation in rats: role of the anterior cingulate cortex

The extent to which the hypothalamic-pituitary-adrenal axis is activated by short-term and long-term consequences of stress is still open to investigation. This study aimed to determine (i) the correlation between plasma corticosterone and exploratory behavior exhibited by rats subjected to the elevated plus maze (EPM) following different periods of social isolation, (ii) the effects of the corticosterone synthesis blocker, metyrapone, on the behavioral consequences of isolation, and (iii) whether corticosterone produces its effects through an action on the anterior cingulate cortex, area 1 (Cg1). Rats were subjected to 30-min, 2-h, 24-h, or 7-day isolation periods before EPM exposure and plasma corticosterone assessments. Isolation for longer periods of time produced greater anxiogenic-like effects on the EPM. However, stretched attend posture (SAP) and plasma corticosterone concentrations were increased significantly after 30?min of isolation. Among all of the behavioral categories measured in the EPM, only SAP positively correlated with plasma corticosterone. Metyrapone injected prior to the 24?h isolation period reversed the anxiogenic effects of isolation. Moreover, corticosterone injected into the Cg1 produced a selective increase in SAP. These findings indicate that risk assessment behavior induced by the action of corticosterone on Cg1 neurons initiates a cascade of defensive responses during exposure to stressors.     

Exclusive breastfeeding at three months and infant sleep-wake behaviors at two weeks,three and six months

This study assessed infant sleep-wake behavior at two weeks, three and six months as function of feeding method at three months (exclusively breastfed, partially breastfed, and exclusively formula fed infants). Mothers of 163 first-born, full-term, normal birth weight, healthy infants completed socio-demographic, depression, anxiety, and infant sleep-wake behavior measures. No effects were found for sleep arrangements, depression or anxiety, on feeding methods and sleep-wake behavior at three months. At two weeks exclusively breastfed infants at three months spent more hours sleeping and less hours awake during the 24-h period than partially breastfed infants. At three months, exclusively breastfed infants had a shorter of the longest sleep period at night than exclusively formula fed infants. At six months, exclusively breastfed infants at three months spent more hours awake at night than partially breastfed infants, awake more at night than exclusively formula fed infants, and had a shorter sleep period at night than partially breastfed and exclusively formula fed infants. This study showed differences in sleep-wake behaviors at two weeks, three and six months, when exclusively breastfed infants are compared with partially breastfed and exclusively formula fed infants at three months, while no effects were found for sleep arrangements, depression or anxiety.     

Is the contribution of the amygdala to the sex- and enhancement-related effects of emotional memory time-dependent?

A new focus in the field of emotional memory is the study of sex-related differences. Whether the sex-related lateralization of amygdala function (i.e., the female-left/male-right effect) in the emotional enhancement of memory (EEM) is time-dependent remains unclear. To evaluate this phenomenon, we conducted a two time-point study (20 min vs. 24 h) using fMRI and behavioral paradigms. We found that the right amygdala predicted 20-min EEM, while the left amygdala predicted 24-h EEM. The sex-related lateralization of amygdala function was not detected in either the 20-min or the 24-h EEM. Our results further confirm and extend the idea that the amygdala exhibits a lateralized and time-dependent dissociation, occurring even in the 24-h EEM relative to the 20-min EEM. The present and previous studies indicate that sex-related lateralization of amygdala function occurs in the 2- to 3-week EEM, but it does not occur in the 1-week, 24-h, or less than 30-min EEM, suggesting that this effect on emotional memory may also be time-dependent.     

Age differences in sleep-wake behavior under natural conditions.

Differences in lifestyle may account for a considerable portion of the reported age-related changes in overt circadian rhythmicity. By instructing a group of healthy, noninstitutionalized, elderly subjects and a group of young adults to keep a sleep-wake log for a period of two weeks, and to wear an activity monitor for an overlapping period of 11 days, we attempted to assess age-related differences in the habitual sleep-wake behavior, in particular its day-to-day variability. Four clusters of coherent variables were constructed, reflecting (1) circadian phase, (2) variability of sleep-wake behavior, (3) sleep-wake continuity and (4) subjective sleep-wake quality. The results showed that, in comparison with the young subjects, the elderly had a relatively advanced and more regular sleep-wake pattern, reported more midnight awakening and did not differ in their subjective sleep evaluation. In spite of a greater regularity in their lifestyle (which would favor a larger amplitude of the overt circadian rhythmicity) oral temperature measurements showed some evidence of a weakened 24-h periodicity in the elderly.     

Circadian rhythms determined by cosine curve fitting: Analysis of continuous work and sleep-loss data

In this study, we report the effects of sleep loss upon circadian rhythm parameters analyzed by the cosine curve fitting (cosinor) method. Rhythm alterations are described as reductions in rhythm strength, increases in individual variations producing an increase in the 95% confidence limits, and reductions in rhythm amplitude. Subjects worked continuously at tasks for 45 h with time-of-day cues. Circadian cycles in physiological and mood variables remained intact, but rhythms in some task performance measures no longer showed significant 24-h/cycle activities. The relationship between oral temperature, mood, and pulse rhythms continued undisturbed during the continuous work period; however, the performance linkage to oral temperature was lost. These findings direct attention to individual difference in susceptibility to continuous work periods and suggest that 24-h rhythms in some performance and physiological measures perhaps are more readily responsive to an altered wake/sleep cycle than other circadian rhythms.     

Sleep deprivation and naps

It is important for military commanders to know the likely effects of a small amount of sleep under conditions of sustained operations. To this end, two laboratory-based experiments on naps were carried out. The first examined the effect of 2 h of sleep following 90 h of wakefulness. Ten infantrymen subjects were not told the scheduled length of their vigil, or that they would be allowed a nap at some stage, until a few hours before the 2-h nap. After 3 nights without sleep, the subjects’ average cognitive performance was 55% of the control values. During a test session immediately before the 2-h nap, performance improved by 30%, to 85% of control values, indicating the considerable effect that the incentive of knowing that a nap is imminent can have on even severely sleep-deprived subjects. In the second experiment, two groups, each of six infantrymen, took part in a 5-day trial; for one group, 4 h of uninterrupted sleep was scheduled and for the other, four l-h naps in each 24-h period. There were no significant differences in cognitive test scores or mood between the two groups. On the last experimental day, cognitive test and mood scores were not significantly different from baseline values for either group, indicating the utility of 4 h of sleep, either in one uninterrupted block or in four scheduled 1-h naps per 24 h.     

Stimulation of hippocampal adenylyl cyclase activity dissociates memory consolidation processes for response and place learning

Procedural and declarative memory systems are postulated to interact in either a synergistic or a competitive manner, and memory consolidation appears to be a highly critical stage for this process. However, the precise cellular mechanisms subserving these interactions remain unknown. To investigate this issue, 24-h retention performances were examined in mice given post-training intrahippocampal injections of forskolin (FK) aiming at stimulating hippocampal adenylyl cyclases (ACs). The injection was given at different time points over a period of 9 h following acquisition in either an appetitive bar-pressing task or water-maze tasks challenging respectively "response memory" and "place memory." Retention testing (24 h) showed that FK injection altered memory formation only when given within a 3- to 6-h time window after acquisition but yielded opposite memory effects as a function of task demands. Retention of the spatial task was impaired, whereas retention of both the cued-response in the water maze and the rewarded bar-press response were improved. Intrahippocampal injections of FK produced an increase in pCREB immunoreactivity, which was strictly limited to the hippocampus and lasted less than 2 h, suggesting that early effects (0-2 h) of FK-induced cAMP/CREB activation can be distinguished from late effects (3-6 h). These results delineate a consolidation period during which specific cAMP levels in the hippocampus play a crucial role in enhancing memory processes mediated by other brain regions (e.g., dorsal or ventral striatum) while eliminating interference by the formation of hippocampus-dependent memory.     

Effects of parafascicular excitotoxic lesions on two-way active avoidance and odor-discrimination

To investigate whether the parafascicular (PF) nucleus of the thalamus is involved in different learning and memory tasks, two experiments were carried out in adult male Wistar rats that were submitted to pre-training bilateral N-methyl-d-aspartate PF infusions (0.15M, pH 7.4; 1.2 microl/side, 0.2 microl/min). In Experiment 1, we evaluated the effects of PF lesions in two identical 30-trial training sessions, separated by a 24-h interval, of a two-way active avoidance conditioning. PF-lesioned rats exhibited impaired performance in both sessions, measured by number of avoidance responses. In Experiment 2, the effects of PF lesions were assessed in a training session (5 trials) and a 24-h retention test (2 retention trials and 2 relearning trials) of an odor-discrimination task. PF lesions did not significantly disrupt the acquisition or the first retention trial, which was not rewarded. However, lesioned animals' performance was clearly affected in subsequent trials, following the introduction of the single non-rewarded trial. Current data are discussed considering evidence that lesions of the PF nucleus affect learning and memory functions mediated by anatomically related areas of the frontal cortex and striatum.     

东莨菪碱对吗啡诱导的大鼠行为敏感化的影响

药物重复处理导致的行为敏感化与成瘾过程密切相关。本实验检验东莨菪碱对吗啡诱导的大鼠行为敏感化发展和转化的影响。实验一动物分为3组,分别进行生理盐水（对照组）、吗啡（10mg/kg,吗啡组）、吗啡（10mg/kg）＋东莨菪碱（3mg/kg,吗啡-东莨菪碱组）前处理,36小时腹腔注射4次（第1~2天）。自然戒断7天（第3~9天）。第10天,所有动物均使用吗啡（4mg/kg）激发,记录动物的自发活动量;第24天,吗啡组和吗啡-东莨菪碱组动物重复第10天的操作。实验二动物分为3组,分别接受生理盐水（对照组）、吗啡（10mg/kg,吗啡组）、吗啡（10mg/kg,吗啡-东莨菪碱组）处理,36小时腹腔注射4次（第1~3天）;间隔12小时后,3组动物分别接受生理盐水、生理盐水和东莨菪碱（3mg/kg）处理,仍为36小时腹腔注射4次（第3 ~5天）。第6~9天不进行药物处理。第10天和第17天,分别使用吗啡（4mg/kg）激发,记录动物的活动量。记录时间均为两小时(10分钟为一个记录单元)。结果表明,东莨菪碱能够抑制吗啡诱导的行为敏感化的发展,一定程度上也能够延缓行为敏感化的转化但没有阻断这种转化     

Sexual experience effects are blocked both by the protein-synthesis inhibitor, cycloheximide, and by the noncompetitive NMDA antagonist, MK-801.

Three studies were done to determine the effects of a brief 2-h sexual experience on the maintenance of sexual behavior in male rats; the effects on the experience-based maintenance of sexual behavior of gonadal hormones (study 1), a protein-synthesis inhibitor (study 2), and an N-methyl-D-aspartate receptor blocker (study 3) were determined. Naive male rats were provided with a 2-h sexual experience with sexually receptive hormonally "primed" females or they received no experience. In the first study animals under each of these conditions then underwent castration or sham surgery. In the second study animals under each of the experience conditions received either cycloheximide (CYX) or saline (SAL; 1.5 or 3.0 mg/kg CYX or SAL sc, 10 min after the experience). In study 3 experienced and inexperienced animals received either 0.07 or 0.10 mg/kg MK-801 ip (15 min before the experience). In all studies animals were tested for sexual behavior 3, 6, and 9 days after surgery or injection. These studies showed that the most consistent effect of a 2-h sexual experience was to facilitate the initiation of mounting, especially on the first test; they show, further, that most experience effects were reduced or eliminated if animals were castrated between experience and test, if they received a drug (CYX) at the time of the experience that blocks the synthesis of proteins, or if they received an NMDA receptor antagonist prior to the experience.     

Cycloheximide blocks the retention of maternal experience in postpartum rats

Two studies were done to determine the effects of cycloheximide (CYX), a protein synthesis inhibitor, on maternal experience effects in rats. In the first study eight groups received a 2-h maternal experience 36 h after cesarean (c)-section and two groups received no post c-section experience. Among the experienced groups, two received icv injections of CYX or saline (SAL) 30 min before the maternal experience, two received CYX or SAL 10 min after the experience, and two received the injections 24 h after the experience. One inexperienced group received CYX and the other received SAL 36 h after c-section. Tests for maternal behavior occurred 10 days after c-section. CYX was not able to block or disrupt the "acquisition" or expression of ongoing maternal behavior during the 2-h experience phase. However, CYX was able to block the long-term "retention" of a 2-h maternal experience if the drug was present during or immediately after the experience, prior to "consolidation." The second study investigated the effects of CYX administered immediately after the maternal experience on the expression and retention of maternal behavior 4 and 6 days after c-section, to determine whether the hormonally mediated short-onset latencies of the 4-day group would be blocked by CYX. Eight groups of animals were tested for maternal behavior. Four were tested 4 days after c-section and four were tested 6 days after c-section. Within each of these groups two were experienced and two inexperienced; within each experience condition one group received CYX and one received SAL. Day 4 groups exhibited shorter onset latencies than Day 6 groups. There was also a CYX-SAL difference in maternal onset latencies among experienced Day 6 groups but not among Day 4 groups. These data indicate that the blocking effects of CYX can be seen only when hormonal priming of maternal behavior is no longer in evidence.     

Modeling the body temperature throughout the day with a two-term function

A two-term function with potential and exponential terms is proposed to model the body temperature throughout the day. These terms can be related to thermogenic and thermolytic processes that are opposite but simultaneous. The first term, a potential function, reflects that the heat gain process is predominant; the second term is a negative exponential function and reflects the predominance of heat dissipation. The function also provides the time of the inflection between thermal opposite processes. The proposed two-term function and a cosine function were fitted to 335 temperature series of 24-h duration recorded in humans and animals. The percentage of variance accounted for by the two-term function was higher than that for the cosine approximation for the total sample and for those series whose shape was asymmetrical (n=75). Nevertheless, no significant differences between the percentage of variance accounted for by the two functions were found for those series whose shape was symmetrical (n=260). The results of different subgroups that differed in experimental conditions are discussed.     

Automatic testing of cognitive performance in baboons maintained in social groups

Laboratory procedures used to study the cognitive functions of primates traditionally have involved removal of the subjects from their living quarters to be tested singly in a remote experimental room. This article presents an alternative research strategy favoring testing primates while they are maintained in their social group. The automatic learning device for monkeys (ALDM) is a computerized test system controlled by an automatic radio frequency identification of subjects. It is provided ad lib inside the social group of monkeys, for voluntary self-testing on a 24-h schedule. Nine baboons were tested with ALDM during a 7-month period. Experiments were performed to assess learning in motor control and abstract reasoning tasks. The results revealed high trial frequencies and excellent learning performance, even in tasks involving the highest cognitive complexities. A different study using ALDM with a group of 3 rhesus monkeys revealed social influences on learning. Beyond its interest for cognitive psychologists, ALDM is of interest for pharmacologists and cognitive neuroscientists working with nonhuman primates. ALDM also can serve as an enrichment tool for captive animals and may be used to study a variety of species other than primates.     

Effects of various hippocampal lesions on monkey plasma cortisol levels in two experimental conditions

The plasma cortisol levels of Rhesus monkeys with anterior, posterior, or near-total hippocampal lesions were compared to controls during two separate stressful conditions. In the first condition, each monkey was placed for the first time in a primate restraint chair for 72 h. In the second condition each monkey performed a complex behavioral task (titrating shock avoidance) to control the intensity of frequent footshock for a 24-h period. Control subjects had either no surgical operation or else surgical exposure of the hippocampus with no hippocampal lesion. They manifested lower plasma cortisol levels during shock avoidance compared with during the chair condition. Subjects with posterior hippocampal lesions manifested the same pattern but near-totally hippocampectomized subjects showed an opposite pattern with cortisol levels higher in the shock avoidance condition compared with the chair condition. Subjects with anterior hippocampal lesions had similar cortisol levels in both conditions. Thus hippocampal modulation of corticosteroid levels may depend on the specific condition under which such levels are measured, and may be relatively more subserved by anterior compared with posterior hippocampus in the monkey.     

Evolution of an Inpatient Pediatric Psychology Consultation Service: Issues Related to Reimbursement and the Use of Health and Behavior Codes

The purpose of this study was to evaluate an inpatient pediatric psychology consultation service, with particular focus on issues related to financial reimbursement for services. Information was gathered over a four year period (2001–2005) regarding number of consults, referral source and referral question, type of insurance, and reimbursement rates for health and behavior codes versus mental health codes. The financial impact of hiring an insurance verification specialist was also explored. Results indicated that reimbursement rates for health and behavior codes were higher than reimbursement rates for mental health codes. Health and behavior codes were rejected in 31% of cases that they were billed; the primary reason for rejection was that these codes were not a covered service by Medicaid. Hiring an insurance verification specialist was found to be a cost-effective method for improving the financial “bottom-line” for psychology services. Implications for practice are discussed.     

Effects of acute and chronic stress and of genotype on oxotremorine-induced locomotor depression of mice

The locomotor behavior of unstressed and stressed mice of two inbred strains, DBA/2 and C57/BL6, was investigated. Animals were tested in a toggle-floor box apparatus, 30 min after saline or oxotremorine treatment (ip). A dose of oxotremorine that did not depress the activity of na?ve mice (0.01 mg/kg) was chosen. Stressed mice were injected 24 h after either a single 2-h stress session (acute stress) or the last of 14 daily stress sessions of tube restraining (chronic stress). Acute stress did not modify the depressant effect of oxotremorine on locomotor behavior in either strain. On the contrary, chronic stress induced a clear sensitization of DBA but not C57 mice to the depressant effect of oxotremorine. These findings show that chronic stress may result in modifications of the cholinergic function, and its behavioral correlates, and that these changes are modulated by the genetic makeup.     

Preliminary evidence of diurnal rhythms in everyday behaviors associated with positive affect

The authors used the Electronically Activated Recorder (EAR) to track within-day variability in everyday behaviors associated with positive and negative affect across two samples. The EAR is a portable audio recorder that periodically samples snippets of ambient sounds from participants’ momentary environments. The recorded sounds are then coded for different behaviors. The study tested whether previous findings regarding diurnal patterns in self-reported mood extend to naturalistically observed behavior. Across both samples, behavior associated with positive affect (i.e., socializing, laughing, and singing) varied according to a sinusoidal 24-h rhythm centered around participants’ average waketime while behavior associated with negative affect (i.e., arguing and sighing) did not. Further, there was preliminary evidence that personality traits can moderate these rhythms (e.g., their amplitude).