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Biomedical subjects

H R Lieberman

Publications and source records attributed to H R Lieberman.

52 records · Page 3Linked to original sources
PubMed1986

Behavior, sleep and melatonin.

The focus of most behavioral studies on melatonin relate to sleep, arousal levels and circadian rhythms of alertness. It has also been suggested that melatonin administration can reduce anxiety (Golus and King, 1981), affect learning (Datta and King, 1980), and exacerbate symptoms in patients suffering from severe depression (Carman et al., 1976). For a variety of reasons the effects of exogenous melatonin on sleep and circadian rhythms seem most likely to reflect the actual physiological functions of the endogenous hormone; however, definitive relationships between melatonin secretion and these effects have not yet been established. Administration of melatonin to humans in pharmacologic doses produces acute hypnotic-like effects (Vollrath et al., 1981; Lieberman et al., 1984). Available evidence suggests that melatonin may participate in the physiological regulation of sleep, particularly in determining the phase of circadian rhythms of sleep and sleepiness (Redman et al., 1983; Wurtman and Lieberman, 1985).

Animals↗
PubMed1985

The effects of dietary neurotransmitter precursors on human behavior.

The neurotransmitter precursors tryptophan and tyrosine are present in a variety of foods. In order to document possible effects of tryptophan and tyrosine on human behavior, single oral doses of these substances and matched placebos were administered to 20 men in a double-blind, crossover study. Various tests of mood state and performance were then administered. Tryptophan increased subjective fatigue and decreased self-ratings of vigor and alertness, but did not impair performance on any of the tests. Tyrosine produced no effects in our young population compared with placebo, but did decrease reaction time relative to tryptophan. It may be concluded that tryptophan has significant sedative-like properties, but unlike other sedatives may not impair performance.

Adult↗
PubMed1985

Correlation between stereo ability and the recovery of structure-from-motion.

Many dynamic graphics displays appear three-dimensional (3D) because of our ability to reconstruct a rotating 3D configuration from its two-dimensional (2D) projection. This ability to infer 3D shape from 2D motion might be considered to be independent of stereopsis because only one eye's view is necessary. On the contrary, however, our data suggest that the mechanisms for both stereopsis and depth-from-motion are not independent but rather must share some components.

Biomechanical Phenomena↗
PubMed1985

Possible behavioral consequences of light-induced changes in melatonin availability.

Melatonin is a hormone secreted at night, in the dark, by the human pineal organ. This nocturnal release of melatonin, in humans and other species, is rapidly suppressed by exposure to sufficiently bright light. In humans, the function, if any, of this circadian pattern of melatonin release has not been determined. In fact, no function has been definitively attributed to the hormone melatonin in humans. In one study, conducted in our laboratory, pharmacologic doses of oral melatonin (240 mg over two hours) were administered to volunteers, and various behavioral parameters were assessed. Melatonin had substantial, but brief, sedative-like effects on mood and performance. Thus it appears that a mechanism exists, whereby light, of sufficient intensity to affect melatonin release in humans, can affect behavior. It can be hypothesized that sufficiently bright light, acting by way of the suppression of melatonin release, can acutely increase alertness or act as a zeitgeber (synchronizer of circadian cycles). The light intensity necessary to suppress melatonin secretion in humans is well above typical indoor lighting conditions, but well below normal outdoor daytime levels of illumination. Therefore, the hypothesis that light may affect behavior or circadian patterns of sleep and waking, if found to be true, could have considerable impact on the design of interior lighting.

Double-Blind Method↗
PubMed1984

Effects of melatonin on human mood and performance.

The function of melatonin, a hormone secreted by the pineal gland primarily at night, has not been definitively established in humans. To determine if pharmacologic doses of melatonin had any behavioral effects it was administered acutely to 14 healthy men. Their mood, performance, memory and visual sensitivity were assessed. Plasma melatonin concentration was assayed as well. Melatonin significantly decreased self-reported alertness and increased sleepiness as measured by the Profile of Mood States and the Stanford Sleepiness Scale self-report mood questionnaires. The effects were brief. Melatonin also affected performance, slowing choice-reaction time but concurrently decreasing errors of commission. Sustained fine motor performance was not impaired after melatonin administration nor were the tests of memory and visual sensitivity that were administered. It is concluded that melatonin, administered orally in pharmacological quantities, has significant but short acting sedative-like properties.

Adolescent↗
PubMed1984

Bioavailability of oral melatonin in humans.

We administered crystalline melatonin (80 mg) in gelatin capsules to 5 young male volunteers and measured serum and urinary melatonin levels at intervals. Changes in serum melatonin levels were best described by a biexponential equation with an absorption constant (ka) of 1.72 h-1 (half-life = 0.40 h) and an elimination constant (ke1) of 0.87 h-1 (half-life = 0.80 h). Peak serum melatonin levels, ranging from 350 to 10,000 times those occurring physiologically at nighttime, were observed 60-150 min after its administration, remaining stable for approximately 1.5 h. The fraction of ingested melatonin that was absorbed, estimated from the area under the curve describing serum melatonin concentrations as a function of time after melatonin administration (the concentration-time curve), varied by 25-fold among subjects. 3 additional volunteers received three melatonin-containing capsules (80 mg each) at 60-min intervals. This regimen extended the duration of elevated serum melatonin levels to 4-6 h. Melatonin excretion closely paralleled serum melatonin levels until 9 h after the hormone's administration, after which urinary levels tended to be higher than those predicted from serum levels. However, the area under the concentration-time curve for serum melatonin correlated well (r = 0.96) with the cumulative melatonin excretion during the initial 15 h after melatonin's administration, indicating that either approach can be used to estimate the absorption of orally administered melatonin.

Administration, Oral↗
PubMed1982

Velocity blindness during shearing motion.

When two subjects lie at different distances from a moving observer, there is a velocity step at the occluding boundary of the nearer object. When the differential motion is tangential to the boundary, the effect is as if a shearing is taking place. If all texture cues are removed by using similar random dot patterns on each side of the boundary, then 20% of the population cannot use this differential motion to locate the boundary when it is presented to the parafovea. These observers are thus abnormally insensitive to the differential rate of texture flow at boundaries undergoing shearing motion. As no such population differences were observed for differential motion perpendicular to the occluding boundary (occluding motion), we infer that independent mechanisms process shearing and occluding motion.

Adolescent↗
PubMedDate not supplied

Mood, performance, and pain sensitivity: changes induced by food constituents.

We examined the behavioral effects of the dietary constituents tryptophan and tyrosine on human mood, sensorimotor performance and pain sensitivity. Tryptophan and tyrosine are neurotransmitter precursors present in varying amount in protein-containing foods. Tryptophan (50 mg/kg) increased subjective drowsiness and fatigue but unlike many hypnotics did not impair sensorimotor performance. Tryptophan also decreased human pain sensitivity in a manner that was more specific than certain analgesic drugs.

Adolescent↗
PubMedDate not supplied

Tyrosine administration prevents hypoxia-induced decrements in learning and memory.

Exposure to hypobaric hypoxia rapidly produces decrements in learning and memory. Tyrosine, a neurotransmitter precursor, has beneficial behavioral effects when administered to animals and humans exposed to various acute stressors. To determine whether tyrosine would protect rats from the adverse effects of hypobaric hypoxia on spatial reference and working memory, it was administered to 27 male Fischer 344 rats tested in the Morris water maze. Rats were tested starting at 2 and 6 h of an 8 h exposure to a simulated altitude of 5950 m (19,500 ft) or sea level. Tyrosine or placebo was administered 1/2 h prior to each testing session (400 mg/kg, IP). Altitude exposure significantly increased working memory escape latency; treatment with tyrosine reversed this decrement. There was no effect of altitude or tyrosine on reference memory. There were also no treatment-related differences in performance when animals were tested the next day at sea level. The beneficial effects of tyrosine on working memory performance may be due to a direct effect of tyrosine on memory, alleviation of a hypoxia-induced retardation of learning, or to other central or peripheral effects of this dietary catecholamine precursor.

Altitude↗
PubMedDate not supplied

Circadian rhythms of activity in healthy young and elderly humans.

Patterns of activity of healthy adult humans were monitored in a controlled environment for several days using a wrist-mounted ambulatory activity meter. Subjects were 15 young males, 14 young females, 17 elderly males and 23 elderly females. Substantial differences in the absolute levels and patterns of daily rest and activity across age groups were observed. The elderly subjects were somewhat more active than the young subjects overall, especially in the early morning. Consistent with their increased levels of daytime activity the elderly subjects reported less sleepiness, especially in the morning, than the young volunteers. The age groups also differed significantly on all circadian parameters. The mean acrophase (peak of a sinusoid fitted to the activity rhythms) of the elderly group occurred at 1326 hr, significantly earlier than in the young group (1513 hr). The amplitude and the mesor (mean level) of the rhythms were both greater in the elderly group. It is uncertain whether these differences reflect changes in behavior that occur as a consequence of the aging process, previously-established differences in the life styles of the different populations studied, or some other factor. These findings suggest that levels and rhythms of daily activity in healthy elderly people are often well preserved and may not deteriorate as readily as had been assumed.

Adult↗
PubMedDate not supplied

Antisense oligonucleotide sequences targeting the muscarinic type 2 acetylcholine receptor enhance performance in the Morris water maze.

Blocking autoinhibitory muscarinic type 2 (m2) acetylcholine receptors in the central nervous system may increase the release of acetylcholine and improve learning and memory. Antisense oligonucleotides (OGNs) complementary to m2 receptor mRNA were synthesized and evaluated for their efficacy at decreasing receptor number and reversing deficits in a cognitive task. Three antisense OGNs, which decreased m2 receptor binding in NG108-15 cells, were continuously infused into the lateral cerebral ventricle of rats for 6 days at a rate of 0.5 micro1/h and a daily dose of 72 microg. Performance in the Morris water maze was compared to groups receiving control OGNs or vehicle alone. Decrements induced by 0.2 mg/kg of scopolamine i.p. were significantly reversed by 2 of the 3 antisense OGNs. Use of antisense OGNs targeting the m2 receptor may be a new strategy to increase cholinergic neurotransmission and improve learning and memory.

Animals↗