In summary, although actigraphy is not as accurate as PSG for determining some sleep measurements, studies are in general agreement that actigraphy, with its ability to record continuously for long time periods, is more reliable than sleep logs which rely on the patients' recall of how many times they woke up or how long they slept during the night and is more reliable than observations which only capture short time periods. Actigraphy can provide information obtainable in no other practical way. It can also have a role in the medical care of patients with sleep disorders. However, it should not be held to the same expectations as polysomnography. Actigraphy is one-dimensional, whereas polysomnography comprises at least 3 distinct types of data (EEG, EOG, EMG), which jointly determine whether a person is asleep or awake. It is therefore doubtful whether actigraphic data will ever be informationally equivalent to the PSG, although progress on hardware and data processing software is continuously being made. Although the 1995 practice parameters paper determined that actigraphy was not appropriate for the diagnosis of sleep disorders, more recent studies suggest that for some disorders, actigraphy may be more practical than PSG. While actigraphy is still not appropriate for the diagnosis of sleep disordered breathing or of periodic limb movements in sleep, it is highly appropriate for examining the sleep variability (i.e., night-to-night variability) in patients with insomnia. Actigraphy is also appropriate for the assessment of and stability of treatment effects of anything from hypnotic drugs to light treatment to CPAP, particularly if assessments are done before and after the start of treatment. A recent independent review of the actigraphy literature by Sadeh and Acebo reached many of these same conclusions. Some of the research studies failed to find relationships between sleep measures and health-related symptoms. The interpretation of these data is also not clear-cut. Is it that the actigraph is not reliable enough to the access the relationship between sleep changes and quality of life measures, or, is it that, in fact, there is no relationship between sleep in that population and quality of life measures? Other studies of sleep disordered breathing, where actigraphy was not used and was not an outcome measure also failed to find any relationship with quality of life. Is it then the actigraph that is not reliable or that the associations just do not exist? The one area where actigraphy can be used for clinical diagnosis is in the evaluation of circadian rhythm disorders. Actigraphy has been shown to be very good for identifying rhythms. Results of actigraphic recordings correlate well with measurements of melatonin and of core body temperature rhythms. Activity records also show sleep disturbance when sleep is attempted at an unfavorable phase of the circadian cycle. Actigraphy therefore would be particularly good for aiding in the diagnosis of delayed or advanced sleep phase syndrome, non-24-hour-sleep syn...

Spontaneous locomotor activity of neonatal and weanling rats was measured in stabilimeter activity cages scaled to the size of the animals under a wide range of temperature and food-deprivation conditions. Activity was low for the first 10 days of life and then increased sharply, reaching a peak nearly 10 times that of normal adult animals 16-20 days postpartum. Activity then declined rapidly to near-adult levels by 28 days of age. This dramatic change in the activity levels of the developing rat is correlated with major ontogenetic changes in the structure and functioning of the central nervous system. These changes may reflect a caudal-rostral sequence of development, in which brainstem excitatory centers and their afferent inputs mature earlier than do the more phylogenetically advanced telencephalic inhibitory centers.In a classic series of papers, Hughlings-Jackson (collected in Taylor, 1931, 1932 proposed that the development of the central nervous system proceeds in a caudalcranial direction with later maturing higher systems acquiring control over early maturing more primitive systems. Numerous studies examining the morphological, electrophysiological, and biochemical maturation of the central nervous system support this general principle of development. Thus, the rate of myelin formation (Jacobson, 1963), increases in neurotransmitter levels and their metabolizing enzymes (Robinson, 1967(Robinson, ,1968, and many other indices of functional and morphological maturity appear first in the spinal cord, then in the brainstem, and finally in the diencephalon and telencephalon. In a like fashion, considerable evidence suggests that the later maturing centers act to modulate or control early developing structures. Simple motor reflexes that are present early in infancy, for example, disappear as telencephalic structures reach

The ability to awaken oneself from sleep at a preselected time without external means (such as alarm clocks) was studied using, first, subjective and, second, objective methods. First, in a telephone survey of 269 unselected adults, over one-half said that they never use an alarm clock (or other external means) or always awaken before it. Another 24% said that they sometimes awaken before the alarm. Furthermore, this ability positively correlated with age and was related to consistency in the amount of nightly sleep but not consistency in wake-up time. Second, 15 people who said they regularly self-awaken were objectively tested for this ability in their own beds using actigraphy for three consecutive nights while choosing their own wake-up times. Five awoke within 10 minutes of their target time (mostly before) on each night, five did so on two of the three nights, and of the remaining five, four did so on one night. Choice of target times varied considerably within subjects but more so for those who were more successful. Taken together these results show that many people have the ability to regularly awaken themselves from sleep at a desired time and that such an ability is of practicable utility.

The effects of amphetamine and insulin on food intake were studied in neonatal and weanling rats. Amphetamine did not produce anorexia prior to 15 days of age and insulin did not produce hyperphagia until 25 days of age. Functional immaturity of the hypothalamus, a change in constituents monitored by the hypothalamus, or maturation of other structures may account for this developmental sequence.