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Biomedical subjects

J Pola

Publications and source records attributed to J Pola.

At least 37 records · Page 2Linked to original sources
PubMed1988

"Passive suppression" of optokinesis by stabilized targets.

Subjects gazed passively at a sinusoidally oscillating optokinetic stimulus. They made no attempt to look at a target which appeared, stabilized on the retina at one of several locations, yet the appearance of the target caused rapid and prolonged suppression of optokinesis. Suppression declined (optokinesis increased) as target eccentricity increased, but could be observed for eccentricities up to 15-20 deg. We propose that a target moving relative to a background is a stimulus for suppression of optokinesis, depending substantially on the visual properties of the target and not the act of attending to it.

Adult↗
PubMed1988

Farm animal feeders: another group affected by cereal flour asthma.

Asthma induced by cereal flour is a long recognized entity. We present studies of three patients affected by asthma related to exposure to cereal flour contained in animal formula feeds. Skin prick test performed with the formula feed components showed positive reactions to cereal flours (wheat, rye and barley) and negative to the other substances in these formulas. Specific anti-wheat, rye and barley flour IgE antibodies were found by RAST. Bronchial provocation tests (BPT) with wheat flour (patients 1 and 2) and barley flour (patient 3) all showed immediate responses. These findings suggest that our patients' symptoms were caused by an IgE-mediated hypersensitivity to cereal flours from animal formula feeds. We call attention to the importance of cereal flours in animal formula feeds as a cause of occupational asthma in farm and animal feeders.

Adolescent↗
PubMed1988

Severe anaphylactoid reaction to nalidixic acid.

We present the case of a 58-year-old non-atopic woman who suffered an adverse reaction to orally administered nalidixic acid, which had been prescribed for the treatment of a urinary tract infection. The single-blind oral provocation test was positive; the patient presented the clinical features of an anaphylactoid reaction 3 min after administration of nalidixic acid. Both the skin test and the histamine release test were negative. These results suggest that we are dealing with an anaphylactoid reaction not described before with this drug.

Anaphylaxis↗
PubMed1987

Dioptric and non-dioptric stimuli for accommodation: target size alone and with blur and chromatic aberration.

The frequency response of the accommodative system (0.05-1 Hz) was determined for various combinations of stimuli: changing target size was presented alone, together with defocus blur, and with both defocus blur and chromatic aberration. A high-speed infrared optometer monitored accommodation while the subject viewed the target in a Badal optometer. Target size was varied sinusoidally and blur was provided by moving the target towards and away from the subject at the same frequency. Chromatic aberration was controlled by using either monochromatic (590 nm) or white (3300 K) light. The target was presented under open-loop conditions when size was the only stimulus. We find that besides the conventional dioptric stimuli, changes in target size that result in changes in apparent distance can have substantial effects on accommodation.

Accommodation, Ocular↗
PubMed1987

Smooth eye movements with step-ramp stimuli: the influence of attention and stimulus extent.

Subjects regarded targets which executed step-ramp motion in one of two conditions, either active (looking at the target) or passive (similar to the subject condition in passive or stare optokinetic nystagmus). The targets jumped 2 deg to one side and returned at a constant velocity. Targets were single round targets or extended targets with a high edge content. Many subjects showed substantial smooth eye movement responses in the passive condition, suggesting that a substantial component of initial smooth movement responses can occur independent of attention. Additional features of the smooth eye movement responses included (i) oculomotor "twitches" (brief, short-latency smooth eye movements in the step direction), (ii) overshoots (eye velocity greater than target velocity), and (iii) oscillations. Most of the response features can be accounted for by a model with a gain that is dependent on the subject's attentional level and on stimulus parameters.

Adult↗
PubMed1986

Stimuli for accommodation: blur, chromatic aberration and size.

We investigated the frequency response of the accommodative system (0.05-1 Hz) using three stimuli: defocus blur, the effects of the chromatic aberration of the eye, and changing target size. A high-speed infrared optometer monitored accommodation while the subject viewed a target in a Badal optometer. Blur was provided by moving the target sinusoidally towards and away from the subject (1-3 D) and the size of the target was varied at the same frequency. Chromatic aberration was controlled by using either monochromatic (590 nm) or white light (3300 K). Gain and phase plots changed systematically as we varied the number of stimuli presented together. This suggests that besides defocus blur both chromatic aberration and changing size are involved in accommodative control.

Accommodation, Ocular↗
PubMed1985

Active and passive smooth eye movements: effects of stimulus size and location.

We measured active smooth pursuit eye movements and passive smooth eye movements in the open-loop condition as subjects viewed moving stimuli of different sizes and at various retinal loci. Active movements have high gain and relatively large phase lag. Passive movements have lower gain and smaller phase lag, and occur with either foveal or eccentric stimuli. They appear to be similar or identical to optokinetic movements. Although different, active and passive movements show a similar increase in amplitude and phase lag as the size of the stimulus was increased. From these findings we suggest that: (1) The stimuli for the active movements are target position and velocity; (2) the stimulus for passive movements is target velocity; and (3) the active response to target velocity is related, in part, to the passive response and thus is related to optokinesis.

Adult↗
PubMed1985

Changing target size is a stimulus for accommodation.

Accommodation was monitored by using a high-speed infrared optometer while subjects viewed a target that appeared to approach and recede in a sinusoidal manner. The target was presented under open-loop conditions to prevent blurring because of accommodation. The experiments suggest that changing target size can be an effective stimulus on its own. This supports the view that accommodation responds to both dioptric and nondioptric stimuli.

Accommodation, Ocular↗
PubMed1984

A mechanism for suppression of optokinesis.

We have studied optokinetic responses to oscillating patterns of dots, and the suppression of these responses by a foveally stabilized target. Such a target suppressed most of the optokinetic response, although the target provided neither retinal target motion nor target offset from the fovea. This indicates that suppression of OKN can occur by other means than smooth pursuit eye movements to traditional stimuli. We studied the form of the suppression for different optokinetic stimulus strengths and stimulus frequencies (0.25-1.0 Hz). The results show that over this frequency range the optokinetic response is substantial, and also that the suppression continues to operate. We also examined the time-course of suppression: it begins to appear within 150-200 msec of the appearance of a fixation target in motion relative to the optokinetic stimulus field.

Adult↗
PubMed1983

Smooth pursuit eye movements under open-loop and closed-loop conditions.

We measured smooth pursuit eye movement responses to sinusoidal target motion in the open-loop condition (target motion stabilized on the retina) and the closed-loop condition (target motion fixed in space). We also predicted the closed-loop response for each subject from the open-loop data, using the relationship for a linear system. Predictions made in this way were very accurate, for both gain and phase lag, even though responses of a given subject usually differed idiosyncratically from those of another. The accuracy of prediction was observed over a broad frequency range (0.5-3Hz) and a moderate range of target amplitudes (2-6 deg, peak-to-peak).

Eye Movements↗
PubMed1978

Pontomedullary reticular projections into the region of the ascending medial longitudinal fasciculus in cat.

The medial longitudinal fasciculus (MLF) and immediately adjacent reticular formation were stimulated electrically just caudal to the trochlear nucleus in the cat. In the pontomedullary reticular formation within 1.5 mm of the midline, antidromically excited neurons were detected in (1) the contralateral abducens nucleus, (2) the contralateral reticular formation just caudal and caudoventral to the abducens nucleus, and (3) the ipsilateral nucleus reticularis pontis caudalis beneath and rostral to the abducens nucleus. The possible involvement of these neurons in eye or body movements is discussed.

Abducens Nerve↗