Biomedical subjects

I Pollack

Publications and source records attributed to I Pollack.

18 recordsLinked to original sources

PubMed1991

Histamine-like immunoreactivity in the visual system and brain of Drosophila melanogaster.

In this study, immunohistochemistry on cryostat sections is used to demonstrate anti-histamine immunoreactivity in the Drosophila brain. The results support earlier findings that histamine is probably a transmitter of insect photoreceptors. It is further shown that, in Drosophila, all imaginal photoreceptors including receptor type R7 are anti-histamine immunoreactive, whereas the larval photoreceptors do not seem to contain histamine. In addition to the photoreceptors, fibres in the antennal nerve and approximately 12 neurons in each brain hemisphere show strong histamine-like immunoreactivity. These cells arborize extensively in large parts of the central brain.

Animals↗

PubMed1991

Herniated L4-L5 disc after placement of Harrington instrumentation for a fracture of the thoracolumbar spine.

The authors report a case in which L5 radiculopathy developed acutely after surgery for placement of Harrington rod instrumentation for an L1 body fracture. Computed tomographic myelography demonstrated a large L4-L5 herniated disc that had not been present in preoperative studies. An emergency laminectomy was performed, and a large, free, subligamentous disc fragment was removed. The patient subsequently regained L5 sensorimotor function. The postoperative development of lumbar radiculopathy is an uncommon complication of Harrington rod instrumentation that may result from several biomechanical features of the instrumentation. These injuries may not be detected by intraoperative monitoring of somatosensory evoked potentials, and therefore, the postoperative neurological examination assumes a crucial role in the early diagnosis of these lesions. As our case demonstrates, these radicular deficits may be reversible if their cause is promptly recognized and treated.

Aged↗

PubMed1990

Detection and discrimination thresholds for auditory periodicity.

Complex periodic auditory signals, produced by the Guttman-Julesz procedure of repeating segments of random noise, were employed to address the low region of auditory periodicity. Periodicity detection and discrimination tasks were examined with a common experimental procedure and a common measure of thresholds. Typically, detection and discrimination performance suffer at extremely low periodicities, presumably because of the extremely close spacing of harmonics throughout the auditory spectrum. Interaural phase effects are extremely weak for these signals, being largely confined to threshold-detection tasks. Despite qualitative phenomenological differences for different periodicity regions, detection and discrimination functions show no sharp discontinuities over a wide range of periodicities.

Adult↗

PubMed1989

Physiological response patterns to cognitive testing in adults with closed head injuries.

Physiological measures were taken from 7 closed-head-injured patients and 7 control subjects while they took a series of cognitive tests: the finger tapping test from the Halstead Reitan battery, the Digit Symbol test from the WAIS-R, a test of logical memory, and a paced arithmetic test. Physiological reactivity was assessed relative to rest periods, which occurred at the beginning and end of each session. The tests and physiological assessment were administered twice, approximately one month apart. The patient group performed more poorly on the cognitive tests, and showed less physiological reactivity during them than did the control group. This pattern was statistically significant for heart rate, frequency of electrodermal responses, and, during the initial session, respiration rate. The control group also showed greater finger pulse amplitude during the first posttest rest period in the first session, and greater constriction during a logical memory task in the second session. No significant between-groups differences emerged for state or trait anxiety. The patients showed higher frontalis EMG and respiration rate during rest. These results suggest a pattern of poor physiological modulation for task performance in the patients with closed head injuries. The therapeutic implications are discussed.

Adolescent↗

PubMed1979

Optic disc parameters and onset of glaucomatous field loss. I. Methods and progressive changes in disc morphology.

Serial stereoscopic fundus photographs taken in known relationship to the onset of glaucomatous visual field loss on 12 eyes were intermixed with those from 206 age- and race-matched controls and analyzed in randomized masked fashion. Progressive changes in the size, shape, or contour of the disc, and a newly described parameter, thickness of the nerve fiber layer as it crosses the disc rim, were readily apparent by the time of onset of glaucomatous field loss in all but two abnormal eyes (one case). In the latter instance, direct comparison of stereophotos indicated progressive pallor of the remaining disc tissue. Serial stereophotographs appear superior to fundus drawings for anticipating glaucomatous field loss.

Glaucoma↗

PubMed1979

Optic disc parameters and onset of glaucomatous field loss. II. Static screening criteria.

Stereoscopic fundus photographs of 17 abnormal eyes, taken in known temporal relationship to the onset of glaucomatous visual field loss, and 206 eyes of age- and race-matched controls were examined in randomized masked fashion. Width of the narrowest remaining disc rim, size of the vertical and horizontal physical cups, contour of the temporal and nasal slopes (vertical ovalness), and a newly described parameter, thickness of the nerve fiber layer as it crosses the disc rim, were all useful for distinguishing patients with impending or established visual field loss. None, however, was as effective as defects in the nerve fiber layer, the only parameter displaying sufficient promise as a clinical screening tool to warrant initiation of large-scale prospective evaluation.

Glaucoma↗

PubMed1979

Discrimination of uniform spectrum pulse sequences.

Random polarity-modulated sequences were produced with a uniform short-term spectrum over defined sampling intervals by a method described by Pierce, Lipes, and Cheetham [J. Acoust. Soc. Am. 61, 1609-1621 (1977)]. These are identified as PLC sequences. By contrast, unconstrained random polarity-modulated pulse trains with a constant interpulse interval may depart from a short-term uniform spectrum. It is shown that listeners can clearly discriminate between PLC sequences and unconstrained random sequences, and can discriminate among different PLC sequences. This discrimination is more nearly related to the statistical redundancy of the PLC sequences. This discrimination is more nearly related to the statistical redundancy of the PLC sequences than to their run-length distribution. Such discrimination is relatively resistant to moderate degrees of temporal jitter and is obtained with other forms of information coding. Discrimination of PLC sequences is presumably based upon phase information.

Acoustic Stimulation↗

PubMed1978

Decoupling of auditory pitch and stimulus frequency: the Shepard demonstration revisited.

With ten successive octave tones, Shepard demonstrated that upward shifts in frequency might be heard as downward shifts in pitch. This decoupling of auditory pitch and frequency has important consequences for any representational theory of pitch. Experiments are reported that attempt to identify the crucial features of Shepard's demonstration.

Acoustic Stimulation↗

PubMed1978

Temporal switching between binaural information sources.

An estimate of the rate of perceptual switching between two binaural information sources was sought by a procedure which employed an emergent perceptual property--the shape of the binaural sound image. Random polarity-modulated pulse trains were delivered to the two ears with controlled periods of interaural phase agreement and of phase disagreement. As the rate of alternation between the two interaural states is increased, discrimination suffers. With equal periods of phase agreement and disagreement, threshold periods of 2.2-3.4 ms, or about 300-450 alternations per second, are obtained. Such rates far exceed estimates of the rate of interaural switching obtained by other experimental paradigms. With unequal periods of agreements and disagreements, a minimum threshold period of 1.5 ms is the limiting factor. Large individual differences were noted. Other procedures for coding binary information yielded similar results. Rapid switching rate thresholds are obtained for narrow-band signals over a wide frequency range. A "central integration time" is identified with the threshold interaural switching period, and appears to be identical with the minimum integration time for monaural tasks.

Acoustic Stimulation↗

PubMed1978

Periodicity measures for repeated random auditory patterns.

Random auditory patterns were repliated according to defined rules, converted toauditory pulse trains, and presented to listeners. Three ined: the threshold fraction of repeated elements necessary for a fixed level of discrimination from a nonrepeated pattern; the accuracy of periodicity matching; and periodicity magnitude ratings. A short-term periodicity analysis over successive replications appears to be more representative of the behavioral measures than a long-term periodicity analysis. Of the signal measures of periodicity examined, the maximum autocorrelation, irrespective of delay, most closely reflects behavioral measures of periodicity strength.

Auditory Perception↗

PubMed1977

The nerve fiber layer in the diagnosis of glaucoma.

Serial fundus photographs of 14 eyes that eventually developed glaucomatous visual field defects and 110 slides from 76 eyes of race- and age-matched controls were reviewed in randomized masked fashion. Each eye that lost visual field demonstrated consistent abnormalities of the nerve fiber layer, beginning as early as 5 years (mean, 1 1/2 years) before it developed glaucomatous visual field defects on routine Goldmann perimetry. Preliminary estimates, based on regression analysis of this small series, suggest that half of these eyes (median) might demonstrate such reproducible abnormalities between four and six years before onset of their visual field defects. Only 9% of the matched controls showed similar nerve fiber layer changes, and in the one instance where analysis was possible, these were inconsistent and nonreproducible. Nerve fiber layer assessment by means of fundus photographs may be the earliest, surest means of distinguishing ocular hypertension from true glaucoma.

Adult↗

PubMed1977

Pitch ratings of harmonic series.

When the components of a harmonic series are of equal amplitude, pitch ratings are determined almost exclusively by the fundamental frequency of the series. Only by extreme modification of the amplitudes of the several components was it possible to modify the pitch ratings assigned to the harmonic series in a direction opposite to that determined by the fundamental frequency.

Auditory Perception↗

PubMed1976