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Biomedical subjects

M Hershenson

Publications and source records attributed to M Hershenson.

At least 19 recordsLinked to original sources
PubMed2000

Perceptual organization in schizophrenia: the processing of symmetrical configurations.

The hypothesis that the perceptual organization dysfunction of patients with poor premorbid schizophrenia is due to a deficit in global visual sensory store processing was tested by assessing their ability to process symmetrical configurations that develop early and have strong prepotent structures. Two same-different judgment tasks in which performance varies as a function of the symmetrical organization and task demands were administered to participants with good and poor premorbid schizophrenia, those with mood disorders, and normal controls. Like the other groups, poor premorbid schizophrenics' latency and error response patterns closely paralled the a priori model of adequate processing. The results support their competence in perceptually processing symmetrical configurations and disconfirm the hypothesis that their input deficiencies represent a general deficiency in all forms of perceptual organization. The implications for specifying their early input dysfunction are discussed.

Adolescent↗
PubMed1999

An airplane illusion: apparent velocity determined by apparent distance.

When a small drone plane appears to be a normal-sized airplane, it appears to be very far away and moving too fast. This is the airplane illusion. In the illusory situation, familiar size determines the apparent size and distance of the plane. It sets the depth for the frontal-plane component of the perceived motion and the relative depth difference for the motion-in-depth component. Because these perceived distances are very large, the perceived velocities are very large in the respective directions. Cognition can override familiarity and produce a veridical perception of the drone.

Aircraft↗
PubMed1993

Linear and rotation motion aftereffects as a function of inspection duration.

Subjects rated the strength of linear and rotary motion aftereffects (MAEs) on an eleven point scale. Inspection durations ranged from 30 to 180 sec in 30 sec steps. In Expt 1, trials using a single inspection duration were spaced at least 22 hr apart to minimize the possibility of interactions between adapting stimuli and long lasting aftereffects. In Expt 2, a counterbalanced sequence of inspection durations was completed in a single session. Total duration of the MAE and durations of the decay phase and tail were measured directly. The decay time constant (DTC), the time it takes for rated strength of the MAE to drop to 1/e of its initial value, was calculated from a line fit to a semilog plot of the ratings during the decay phase. The DTC is inversely related to the decay rate which is indexed by the slope of this line. In both experiments, the duration and DTC increased, and decay rate decreased, with increasing inspection duration for both rotary and linear MAEs. This finding replicates the results for linear MAEs and extends them to rotation MAEs. There were no discernible differences between the two types of MAEs. When the trials were spaced, the total duration increased with the square root of inspection duration. The DTC did not follow the square root rule over the entire range but appeared to approximate it for inspection durations of 90 sec and above. When trials were massed, the square root rule did not appear to apply at all.

Adaptation, Ocular↗
PubMed1993

Structural constraints: further evidence from apparent motion in depth.

The three-dimensional (3-D) apparent motion of lines, outline triangles, and light points was studied in four experiments. The stimulus sequences were beginning and end patterns of 3-D motions of a line and a triangle. Light-point patterns corresponded to the ends of the lines and the vertices of the triangles. Perceived motion of lines and light-point pairs resembled the distal motions that were used to construct the proximal patterns. The correspondence was striking for configurations that appeared to move in depth. Outline triangles and light-point triplets produced a strong correspondence between distal and perceived motions when the three sides appeared to be translating in depth. The correspondence was reasonably good for the other motion patterns when scoring included an appropriate second category. The results support the conception of structural or internalized constraints: light points were processed as if they were connected (unity constraint) and proximal change in linear size (or distance between light points) was perceived as rigid 3-D motion (rigidity constraint).

Adult↗
PubMed1992

Size-distance invariance: kinetic invariance is different from static invariance.

The static form of the size-distance invariance hypothesis asserts that a given proximal stimulus size (visual angle) determines a unique and constant ratio of perceived object size to perceived object distance. A proposed kinetic invariance hypothesis asserts that a changing proximal stimulus size (an expanding or contracting solid visual angle) produces a constant perceived size and a changing perceived distance such that the instantaneous ratio of perceived size to perceived distance is determined by the instantaneous value of visual angle. The kinetic invariance hypothesis requires a new concept, an operating constraint, to mediate between the proximal expansion or contraction pattern and the perception of rigid object motion in depth. As a consequence of the operating constraint, expansion and contraction patterns are automatically represented in consciousness as rigid objects. In certain static situations, the operation of this constraint produces the anomalous perceived-size-perceived-distance relations called the size-distance paradox.

Depth Perception↗
PubMed1992

The perception of shrinking in apparent motion.

Apparent motion was produced using two triangular patterns of different sizes, each exposed for 100 msec, with a 50-msec interstimulus interval and 200-msec recycle interval. The triangles were aligned either on center or on the midpoints of the bases. In Experiment 1, filled, outline, and three-dot triangles were viewed over four backgrounds: a blank illuminated field, and texture gradients constructed from horizontal lines, perspective lines, or a combination of these (full texture). In Experiment 2, outline and dot triangles were presented in one of three orientations: base down, base right, and base up over a blank background. Subjects made two forced-choice responses: apparent size was categorized as shrinking or not shrinking, and apparent motion was categorized as motion in depth or motion in a fixed frontal plane. The type of alignment was the major determiner of responses. When the midpoints of the base were aligned, the predominant response described a shrinking object in a fixed position in depth. When the centers were aligned, the predominant response described an object of constant size moving in depth.

Adult↗
PubMed1989

Duration, time constant, and decay of the linear motion aftereffect as a function of inspection duration.

Subjects rated the strength of the motion aftereffect (MAE) produced by the upward motion of a horizontal grating in two experiments. Inspection periods ranged from 30 to 900 sec in Experiment 1 and from 20 to 120 sec in Experiment 2. A minimum of 22 h elapsed between trials. The decay time constant increased as the square root of the inspection duration for values between 1 min and 15 min of inspection. The ratings suggested that the MAEs consisted of three phases: an initial maximum-strength phase, a decay phase, and a tail. The duration of all three phases increased and the decay rate decreased with increasing inspection duration over the entire range. The results indicate that duration, time constant, and decay rate are not fixed properties of the motion-processing channels in the visual system.

Adult↗
PubMed1984

The effect of chloral hydrate on genioglossus and diaphragmatic activity.

A child presented with obstructive sleep apnea (OSA) and a near-fatal airway obstruction and respiratory arrest shortly after receiving chloral hydrate (CH). We, therefore, hypothesize that CH might selectively depress upper airway maintaining muscles such as the genioglossus and so predispose to airway obstruction. Genioglossus (GG) and diaphragmatic (DIA) integrated electromyograms (I EMGs) were recorded in four cats and four rabbits before and after hypnotic doses of CH ranging from 200-1000 mg/kg. Results were similar in both species. Peak GG I EMG decreased within 10-20 min after CH in seven of eight animals. Average peak GG I EMGs were decreased from 100% before CH to as low as 37.0 +/- 27.2% (SD) after CH (P less than 0.001). Minimum GG I EMGs fell from 47.2 +/- 27.2% of peak values before CH to as low as 16.0 +/- 9.7% after CH (P less than 0.01). Phasic GG I EMGs decreased from 53.8 +/- 25.1% of peak control activity to as low as 20.6 +/- 24.6% after CH (P less than 0.05). By contrast, peak and phasic DIA I EMGs after CH were not significantly different from those before CH administration. We conclude that hypnotic doses of CH may preferentially depress GG activity as compared with DIA activity. Selective depression of airway-maintaining muscular contraction by CH may place susceptible patients at risk for life-threatening airway obstruction and may preclude the use of CH to facilitate sleep for polygraphic evaluations in patients suspected of having OSA.

Animals↗
PubMed1983

Tests of a two-stage model of visual matching.

Predictions from a model of visual matching were tested in two experiments. The model consists of a wholistic comparison process followed by an element-by-element comparison process. All stimuli are processed by the first stage but only those that permit a decision based on a wholistic comparison produce responses. When discrimination is difficult and a decision cannot be reached by a wholistic comparison, the second stage of processing is initiated. Degree of discriminability and stimulus duration (100 and 1000 msec.) were varied in both experiments. In Exp. 1, the stimulus elements were arranged in a square configuration to facilitate a wholistic comparison. As predicted, the hard-different stimuli took longer to match than the same or easy-different stimuli. The hard-different stimuli presented for 1000 msec. took longer to match than those presented for 100 msec. There was no difference in accuracy between responses to hard-different pairs at the two durations. In Exp. 2, the stimulus elements were arranged in a horizontal row and placed one above the other to facilitate element-by-element comparison. As predicted, these stimuli produced slower and more accurate responses for same and hard-different stimulus pairs only when they were exposed for 1000 msec. Responses to easy-different stimulus pairs were made quickly and accurately.

Adult↗
PubMed1982

Moon illusion and spiral aftereffect: illusions due to the loom-zoom system?

The moon illusion and the spiral aftereffect are illusions in which apparent size and apparent distance vary inversely. Because this relationship is exactly opposite to that predicted by the static size--distance invariance hypothesis, the illusions have been called "paradoxical." The illusions may be understood as products of a loom-zoom system, a hypothetical visual subsystem that, in its normal operation, acts according to its structural constraint, the constancy axiom, to produce perceptions that satisfy the constraints of stimulation, the kinetic size--distance invariance hypothesis. When stimulated by its characteristic stimulus of symmetrical expansion or contraction, the loom-zoom system produces the perception of a rigid object moving in depth. If this system is stimulated by a rotating spiral, a negative motion-aftereffect is produced when rotation ceases. If fixation is then shifted to a fixed-sized disc, the aftereffect process alters perceived distance and the loom-zoom system alters perceived size such that the disc appears to expand and approach or to contract and recede, depending on the direction of rotation of the spiral. If the loom-zoom system is stimulated by a moon-terrain configuration, the equidistance tendency produces a foreshortened perceived distance for the moon as an inverse function of elevation and acts in conjunction with the loom-zoom system to produce the increased perceived size of the moon.

Astronomical Phenomena↗
PubMed1982

Orthographic regularity, lexical status, and letter-identification acuity.

Hershenson reported in 1980 that accuracy for identifying letters from seven-letter strings was not affected by the orthographic regularity or the lexical status of the strings when the letter to be reported was indicated by a vertical bar marker that appeared simultaneously with the string or immediately after it. Since the initial visual representation begins to fade soon after stimulus offset and lasts for about 250 msec., stimulus structure may affect the extraction and storage processes necessary to produce a correct response if the indicator is delayed. Two experiments explored this region by sampling seven retinal locations within the central 2.6 degrees of the visual field. The indicator was delayed for 100, 200, and 300 msec. in Exp. 1 and 0, 25, 50, and 75 msec. in Exp. 2. Stimulus structure did not affect accuracy of identification when subjects were equally familiar with the letter strings (memorization group) but had a strong effect for the group instructed to guess (forced-guess group). The group unfamiliar with the strings but instructed not to guess (no-guess group) showed effects of stimulus structure only at delays of the indicator longer than 100 msec. These data support a model of visual processing that includes an initial representation unaffected by orthographic regularity or lexical status, variables that determine the availability of information only when it must be retained before it is used.

Discrimination Learning↗
PubMed1982

Perceived symmetry and visual matching.

The effects of perceived symmetry on physical-matching latency was evaluated. The stimuli were letter pairs made from the letters F, G, J, L. and R in either normal, reversed, or inverted orientations. When the same letter was used twice to form a pair, the different orientation-combinations produced four types of symmetry: rotational, vertical-axis bilateral, and translational symmetry, as well as a distorted version of horizontal-axis bilateral symmetry. Perceptual organization in the form of symmetry inhibited physical matching.

Discrimination Learning↗
PubMed1980

Guessing instructions, experience with stimuli, and array structure in tachistoscopic letter identification.

The roles of guessing instructions, familiarity with the stimuli, and array structure were assessed in a letter identification task. Seven retinal locations were sampled within the central 2.6 degrees of the visual field using an indicator that appeared either simultaneously with the array or immediately after it. Retinal locus was the major determiner of letter-recognition accuracy, producing W-shaped functions regardless of instructions, or degree of familiarity with the stimuli. Stimulus structure did not produce a systematic effect.

Discrimination Learning↗