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Changes in shock-evoked response complex /SERC/ RECORDED from visual cortexes of cats after retinal illumination, noting enhancement of waveform after photic stimulation and role of barbiturate anesthetization
Electroencephalogram reactivity and reactivity and reaction time of subjects to photic stimulation
A subpopulation of neurons in the suprachiasmatic nucleus (SCN) is shown here to exhibit isoperiodic bursting activity. The period of discharge in these cells may be lengthened or the periodicity may be transiently disrupted by photic stimulation. It is suggested that many, if not all, of these cells are vasoactive intestinal polypeptide (VIP) neurons. It is shown that the ultradian periodicity of these cells, estimates of the VIP neuron population size in the SCN, effects of partial lesions on tau (period), and estimates of the phase stability of SCN-driven circadian rhythms are consistent with a strongly coupled, multioscillator model of circadian rhythmicity, in which the oscillator population constitutes a restricted subset of the SCN neuronal population.
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Several levels of photosynthetic photon flux density (PPFD) were tested for effects on growth of 4 cultivars of lettuce (Lactuca sativa L.) under controlled-environment conditions. Growth of 'Salad Bowl', 'Bibb', and 'Ruby' was greater at 932 micromoles s-1 m-2 than at < or = 644 micromoles s-1 m-2 under a 16-hour photoperiod. Thirty mM NO3- or 5 mM NH4+ + 25 mM NO3- increased leaf dry weight while reducing leaf chlorosis in 'Salad Bowl' and 'Grand Rapids' relative to that with 15 mM NO3-, and reduced leaf purpling in 'Bibb' and 'Ruby' with little or no effect on yield. Continuous illumination with 455 or 918 micromoles s-1 m-2 stimulated yield of 'Salad Bowl' and 'Bibb' when 30 mM N as NH4+ + NO3- was used relative to that with 15 mM NO3-.
This study examined the effect of optokinetic stimulation on objective sleepiness, as measured by the Multiple Sleep Latency Test (MSLT). The Nightcap, a portable sleep monitor, was used in a novel way to perform MSLTs, as well as record sleep in the home. Subjects wore the Nightcap for seven consecutive nights. On days 3 and 5 of the protocol, subjects came into the lab for an MSLT. On the experimental day, subjects underwent 10 minutes optokinetic stimulation (OKS), resulting in moderate motion sickness prior to each MSLT trial. Although subjects in the OKS condition reported significantly more drowsiness than controls, this did not result in significantly reduced sleep latencies.
The eye movement response to earth vertical axis rotation in the dark, a semicircular canal stimulus, can be altered by prior exposure to combined visual-vestibular stimuli. Such plasticity of the vestibulo-ocular reflex has not been described for earth horizontal axis rotation, a dynamic otolith stimulus. Twenty normal human subjects underwent one of two types of adaptation paradigms designed either to attenuate or enhance the gain of the semicircular canal-ocular reflex prior to undergoing otolith-ocular reflex testing with horizontal axis rotation. The adaptation paradigm paired a 0.2 Hz sinusoidal rotation about a vertical axis with a 0.2 Hz optokinetic stripe pattern that was deliberately mismatched in peak velocity. Pre- and post-adaptation horizontal axis rotations were at 60 degrees/s in the dark and produced a modulation in the slow component velocity of nystagmus having a frequency of 0.17 Hz due to putative stimulation of the otolith organs. Results showed that the magnitude of this modulation component response was altered in a manner similar to the alteration in semicircular canal-ocular responses. These results suggest that physiologic alteration of the vestibulo-ocular reflex using deliberately mismatched visual and semicircular canal stimuli induces changes in both canal-ocular and otolith-ocular responses. We postulate, therefore, that central nervous system pathways responsible for controlling the gains of canal-ocular and otolith-ocular reflexes are shared.
Head and eye movements in the yaw plane were recorded during and after optokinetic stimulation in squirrel monkeys. 1) Phasic or tonic head deviations to the side of the ocular quick phase occurred in 94% of total recordings (n = 50) during the perstimulus period, and in 75% of recordings (n = 49) during the poststimulus period. Magnitude of mean head deviation was significantly different between perstimulus and poststimulus periods. 2) Head nystagmus associated with eye nystagmus was consistently observed in seven of nine squirrel monkeys during optokinetic stimulation. Squirrel monkeys are thereby less prone to display head nystagmus than either guinea pigs, pigeons or chickens. 3) Slow phase speeds of coupled head and eye nystagmus were subjected to statistical analysis. A highly significant negative correlation was found between slow phase head and eye speeds. The correlation coefficient was - 0.81 at 60 degrees / sec stimulus (n = 119) and -0.72 at 100 degrees / sec stimulus (n = 131). The gaze speed, calculated by summing the head and eye speeds, was 59.1 plus or minus 6.8 / sec at 60 degrees / sec and 92.2 plus or minus 11.4 at 100 degrees / sec stimulus. There was no significant difference between the gaze speed in a free head condition and the eye speed when the head was fixed.
The regulatory pigment phytochrome induces rapid and opposite growth changes in different regions of etiolated maize seedlings: it stimulates the elongation rate of coleoptiles and inhibits that of mesocotyls. As measured by a quantitative immunoassay, phytochrome also promotes rapid and opposite changes in the extractable content of a Mr 98,000 anionic isoperoxidase in the cell walls of these same organs: it induces a decrease of this peroxidase in coleoptiles and an increase in mesocotyls. The peroxidase changes precede the growth changes. As measured by video stereomicroscopy or a position transducer, red light (R), which photoactivates phytochrome, stimulates coleoptile elongation with a lag of about 15-20 min and suppresses mesocotyl growth with a lag of 45-50 min. R also induces a 50% reduction in the extractable level of the anionic peroxidase in coleoptile walls in less than 10 min and a 40% increase in the level of this peroxidase in mesocotyl walls within 30 min. Ascorbic acid, an inhibitor of peroxidase activity, blocks the effects of R on mesocotyl section growth. These results are relevant to hypotheses that postulate that certain wall peroxidases can participate in light-induced changes in growth rate by their effects on wall extensibility.
Optokinetic nystagmus (OKN) was induced by having subjects watch a moving display in a binocular, head-fixed apparatus. The display was composed of 3.3 degrees stripes moving at 35 degrees/s for 45 s. It subtended 88 degrees horizontally by 72 degrees vertically of the central visual field and could be oriented to rotate about axes that were upright or tilted 45 degrees or 90 degrees. The head was held upright or was tilted 45 degrees left or right on the body during stimulation. Head-horizontal (yaw axis) and head-vertical (pitch axis) components of OKN were recorded with electro-oculography (EOG). Slow phase velocity vectors were determined and compared with the axis of stimulation and the spatial vertical (gravity axis). With the head upright, the axis of eye rotation during yaw axis OKN was coincident with the stimulus axis and the spatial vertical. With the head tilted, a significant vertical component of eye velocity appeared during yaw axis stimulation. As a result the axis of eye rotation shifted from the stimulus axis toward the spatial vertical. Vertical components developed within 1-2 s of stimulus onset and persisted until the end of stimulation. In the six subjects there was a mean shift of the axis of eye rotation during yaw axis stimulation of approximately 18 degrees with the head tilted 45 degrees on the body. Oblique optokinetic stimulation with the head upright was associated with a mean shift of the axis of eye rotation toward the spatial vertical of 9.2 degrees. When the head was tilted and the same oblique stimulation was given, the axis of eye rotation rotated to the other side of the spatial vertical by 5.4 degrees. This counterrotation of the axis of eye rotation is similar to the "Muller (E) effect," in which the perception of the upright is counterrotated to the opposite side of the spatial vertical when subjects are tilted in darkness. The data were simulated by a model of OKN with a "direct" and "indirect" pathway. It was assumed that the direct visual pathway is oriented in a body, not a spatial frame of reference. Despite the short optokinetic after-nystagmus time constants, strong horizontal to vertical cross-coupling could be produced if the horizontal and vertical time constants were in proper ratio and there were no suppression of nystagmus in directions orthogonal to the stimulus direction. The model demonstrates that the spatial orientation of OKN can be achieved by restructuring the system matrix of velocity storage. We conclude that an important function of velocity storage is to orient slow-phase velocity toward the spatial vertical during movement in a terrestrial environment.
Stimulus intensity and photically evoked cerebral response as possible objective index of brightness perception for man
Temperature and preconditioning effect on photoperiodic response of Pharbitis nil, strain Violet short-day plant
Visual effects produced by factors of so-called glare from stationary and moving targets
Visually evoked cortical response correlates of perceptual masking and enhancement
Sequential analysis of electroencephalogram frequency and reaction time in vigilance task
Statistical analysis of average evoked visual potential induced by light stimulus of varying intensity and duration
Intra-individual variability of evoked potential and reaction time to photic stimulus