Fred H. Previc

The University of Texas at San Antonio | UTSA

A fundamental feature of the human brain is the substantial inhibition it normally experiences from different sources. One of the most important of these is callosal inhibition, most prominently manifested in the inhibition of the right hemisphere by the left one. Such inhibition may be especially prevalent during the preparation and execution of s...

The relationship between topographical and non-topographical cognitive measures was studied for 25 elderly participants. The topographical measures were the Camden Topographical Recognition Memory Test (CTRMT), a Topographical Mental Rotation Test (TMRT), and a Virtual Pond Maze (VPM). The non-topographical tests were the Montreal Cognitive Assessm...

Introduction: A theory is presented to explain the major findings regarding motion sickness and to synthetize current theories concerning its etiology. The theory proposes that an imbalance in the output of the two major organs of the labyrinth-favoring the semicircular canals over the otolith organs-is responsible for most instances of motion sic...

Research during the past two decades has demonstrated an important role of the vestibular system in topographical orientation and memory and the network of neural structures associated with them. Almost all of the supporting data have come from animal or human clinical studies, however. The purpose of the present study was to investigate the link b...

This study examined the effects of 35 h of continuous sleep deprivation on performance in a variety of cognitive tasks as well as simulated flight. Ten United States Air Force pilots completed the Multi-Attribute Task Battery (MATB), Psychomotor Vigilance Task (PVT), and Operation Span Task (OSPAN), as well as simulated flight at 3 h intervals over...

Functional specialization in the lower and upper visual fields in humans is analyzed in relation to the origins of the primate visual system. Processing differences between the vertical hemifields are related to the distinction between near (peripersonal) and far (extrapersonal) space, which are biased toward the lower and upper visual fields, resp...

A new laser signal for communicating with aircraft is being developed to warn aircraft against entering metropolitan area air defense identification zones. The purpose of this experiment was to determine the irradiance and laser characteristics (color and frequency) of effective warning signals in simulated day and night scenes. Ten subjects, half...

Optical radiation sources represent effective means of communicating warning information to travelers entering restricted areas in vehicles or on foot. Warnings can be communicated independent of language barriers to travelers not equipped with radio or satellite communication devices. The objective of this research is to document what qualities of...

The effects of 34 hr of continuous wakefulness on flight performance, instrument scanning, subjective fatigue, and EEG activity were measured. Ten fixed-wing military pilots flew a series of 10 simulator profiles, and root mean squared error was calculated for various flight parameters. Ocular scan patterns were obtained by magnetic head tracking a...

What does it mean to be human? There are many theories of the evolution of human behavior which seek to explain how our brains evolved to support our unique abilities and personalities. Most of these have focused on the role of brain size or specific genetic adaptations of the brain. In contrast, Fred Previc presents a provocative theory that high...

Spatial disorientation mishaps are greater at night and with greater time on task, and sleep deprivation is known to decrease cognitive and overall flight performance. However, the ability to perceive and to be influenced by physiologically appropriate simulated SD conflicts has not previously been studied in an automated simulator flight profile....

The incidence of autism has risen 10-fold since the early 1980s, with most of this rise not explainable by changing diagnostic criteria. The rise in autism is paradoxical in that autism is considered to be one of the most genetically determined of the major neurodevelopmental disorders and should accordingly either be stable or even declining. Beca...

The neuropsychology of religious activity in normal and selected clinical populations is reviewed. Religious activity includes beliefs, experiences, and practice. Neuropsychological and functional imaging findings, many of which have derived from studies of experienced meditators, point to a ventral cortical axis for religious behavior, involving p...

Irradiation of the ocular lens of numerous species by near-UV or short-visible wavelengths induces a blue-green fluorescence, which can be a source of intraocular veiling glare. Wavelengths longer than the approximately 365-nm lens absorption peak induce progressively weaker but also progressively more red-shifted fluorescence emission. The more re...

Previous research suggests that the visual impairment of a violet laser is not highly localized on the retina, because the lens absorbs most short-wavelength visible light and partly retransmits it as a diffuse fluorescence at approximately 500 nm. The present study investigated whether a 405 nm violet diode laser more greatly impairs visual search...

Irradiation of the ocular lens of numerous species by near-UV or short-visible wavelengths induces a blue-green fluorescence, which can be a source of intraocular veiling glare. Wavelengths longer than the ~365-nm lens absorption peak induce progressively weaker but also progressively more red-shifted fluorescence emission. The more red-shifted emi...

Higher-order cognition in humans has not generally been viewed as closely entwined with the brain mechanisms mediating more basic perceptual-motor interactions in 3-D space. However, recent findings suggest that perceptual and oculomotor mechanisms that are biased toward the upper field (which disproportionately represents radially distant space) a...

On Sept 11, 2001, it became evident that protecting military and other high value assets from airborne attack was critical to national security. One of the challenges associated with this task is determining if approaching aircraft have friendly or unfriendly intent. The ability to warn and ward-off general aviation and commercial pilots not mainta...

Human performance, particularly that of the warfighter, has been the subject of a large amount of research during the past few decades. For example, in the Medline database of medical and psychological research, 1,061 papers had been published on the topic of “military performance” as of October 2003. Because warfighters are often pushed to physiol...

In a positron emission tomography (PET) study, a very large visual display was used to simulate continuous observer roll, yaw, and linear movement in depth. A global analysis based on all three experiments identified brain areas that responded to the three conditions' shared characteristic of coherent, wide-field motion versus incoherent motion. Se...

Previous studies have indicated that, compared with nonpilots, pilots rely more on vision than "seat-of-the-pants" sensations when presented with visual-vestibular conflict. The objective of this study was to evaluate whether pilots and nonpilots differ in their thresholds for tilt perception while viewing visual scenes depicting simulated flight....

This study examined the effects of background field-of-view and depth plane on the oculogyral illusion. Seven subjects viewed a stationary fixation stimulus during the postrotatory interval following a 45-sec constant-velocity chair rotation. The duration of the illusory movement of the fixation stimulus during the postrotatory interval was measure...

The evolutionary origin of bipolar disorder (EOBD) proposed by Dr. J. A. Sherman is intuitively appealing but lacking in two important respects: 1) epidemiological evidence does not provide clear support for it; and 2) it is lacking a neural foundation. The latter problem may be corrected by assuming that seasonal fluctuations in dopamine partly un...

Trends in spatial disorientation (SD) research over the past six decades were assessed by means of a literature review using four databases and three SD-related search terms. 347 SD-related papers were identified, 37% of which were in three categories: attitude displays, SD training, and SD incidence. The most dramatic trend was a marked upswing in...

The realism of reflection holographic stereograms was evaluated to determine how acceptable they are to a non-technical audience. The stereograms were rated for realism by comparing them to photographic images and real objects. Although the ratings were favorable, they did not quite achieve the realism of photographic images, but 3D cues of depth a...

In this study, asymmetries in finding pictorial 3-D targets defined by their tilt and rotation in space were investigated by means of a free-scan search task. In Experiment 1, feature search for cube tilt and rotation, as assessed by a spatial forced-choice task, was slow but still exhibited a characteristic "flat" slope; it was also much faster to...

Pilots employing helmet-mounted displays spend sustained periods of time looking off-axis, necessitating the inclusion of attitude symbology on the helmet to maintain spatial awareness. We examined how fundamentally different attitude references, a moving-horizon ("inside-out") or a moving-aircraft ("outside-in"), affected pilot and nonpilot attitu...

In this study, asymmetries in finding pictorial 3-D targets defined by their tilt and rotation in space were investigated by means of a free-scan search task. In Experiment 1, feature search for cube tilt and rotation, as assessed by a spatial forced-choice task, was slow but still exhibited a characteristic “flat” slope; it was also much faster to...

Ambient vision comprises the visual functions that are associated with the maintenance of spatial orientation and that depend on peripheral, preconscious visual inputs. Although a limited number of brain areas appear to be activated by coherent wide-field-of-view (WFOV) motion in more than one axis, a diffuse pattern of lateralized brain activity o...

The brain areas involved in processing wide field-of-view (FOV) coherent and incoherent visual stimuli were studied using positron emission tomography (PET). The brains of nine subjects were scanned as they viewed texture patterns moving in the roll plane. Five visual conditions were used: (1) coherent clockwise (CW) wide-FOV (>100°) roll motion; (...

Despite the rigorous process for selecting and training military pilots, they all too often succumb to spatial disorientation (SD) and loss of situation awareness (LSA) in flight. It is estimated that SD mishaps occur once every 300,000 hours and that an LSA mishap occurs about three times as often. Hence, an experienced pilot with 3,000 hours of f...

Ambient vision comprises the visual functions that are associated with the maintenance of spatial orientation and that depend on peripheral, preconscious visual inputs. Although a limited number of brain areas appear to be activated by coherent wide-field-of-view (WFOV) motion in more than one axis, a diffuse pattern of lateralized brain activity o...

This commentary focuses on the larger implications of Grodzinsky's hypothesis. Although Grodzinsky argues persuasively that the syntactic comprehension deficits in Broca's aphasia involve mainly an inability to comprehend sentences requiring a transformational movement of phrasal constituents, his larger claim for a distinct and dedicated “language...

A general theory is proposed that attributes the origins of human intelligence to an expansion of dopaminergic systems in human cognition. Dopamine is postulated to be the key neurotransmitter regulating six predominantly left-hemispheric cognitive skills critical to human language and thought: motor planning, working memory, cognitive flexibility,...

The "outside-in" attitude display concept, which includes a moving-aircraft (as opposed to a moving-horizon) attitude reference, dates back to the early days of flying. The majority of the laboratory and in-flight studies that have evaluated the outside-in format over the years have found it to be superior at preventing roll-reversal errors during...

The neuropsychological literature on 3-D spatial interactions is integrated using a model of 4 major behavioral realms: (a) peripersonal (visuomotor operations in near-body space), (b) focal extrapersonal (visual search and object recognition), (c) action extrapersonal (orienting in topographically defined space), and (d) ambient extrapersonal (ori...

In a recent theoretical paper (Behavioral and Brain Sciences, 1990, 13, 519-542), Previc argued that vertical asymmetries in perception may largely result from the biases of the lower and upper visual fields toward proximal and distal space, respectively. The present study examined whether this same relationship may exist for visual scene memory, b...

Twelve healthy men underwent measurement of their carotid-cardiac baroreflex response during varying conditions of vestibulo-oculomotor stimulation to test the hypothesis that vestibular and/or oculomotor stimulation associated with head movements in the yaw plane inhibit baroreflex control of heart rate. We assessed the carotid-cardiac baroreflex...

Previous research has shown that both vertical and lateral eye movements occur during mental tasks, although the neuropsychological basis for such movements remains unclear. Vertical and lateral eye movements were recorded from 24 right-dominant subjects as they performed three different mental tasks: a mental arithmetic task, a visuospatial imager...

Two experiments were performed to assess the influence of attentional and oculomotor factors on the advantage of the upper-right visual field in visual search for shape targets (Previc & Blume, 1993). In Experiment 1, attention was manipulated by varying the number of distractors in a standard conjunction-search task (subjects had to find a target...

Two experiments tested near-threshold recognition performance throughout the visual field, examined the effect of the recognition task on a concurrent attitude tracking task, and tested whether individuals' near-threshold performance would predict their dual-task performance. In Experiment 1, an adaptive procedure measured the minimum viewing durat...

Several recent studies suggest that left-handers have higher susceptibility to accidental injury. Two studies investigated the suggested link between sinistrality and accidental injury by assessing the prevalence of joint problems, bone breaks, and fractures, which may be the sequelae of such mishaps. Study 1 used retrospective responses on medical...

It has been proposed that asymmetry in the inner ear underlies various manifestations of brain-behaviour asymmetry in the human. Specifically, Previc (1991) argued that an otolith imbalance manifests itself in an asymmetrical head posture, and later (1994) suggested that head tilt may be consonant with other measures of human laterality. The presen...

An automated bisection device (ABD) is described that is designed for use in assessing the direction of three-dimensional neglect in various clinical populations. This device features an apparatus containing two base sections and a connecting rod, on which is located a bisection indicator assemblage that can be moved either by hand or by a calibrat...

A theoretical analysis of the associations between nonright‐handedness (NRH) and various neurodevelopmental disorders, psychopathology, and related medical conditions is presented. Fourteen disorders and conditions are reviewed in which elevated NRH has been alleged. Impaired noradrenergic activity and, to a lesser extent, serotonergic dysfunction...

In a recent article in Aviation, Space, and Environmental Medicine, Navathe and Singh proposed new "operational" definitions for spatial disorientation (SD) and loss of situation(al) awareness (LSA). The major feature of their new scheme was to treat the two phenomena as distinct, with SD attributable to physiologically based (peripheral) illusions...

This study investigated how the size and eccentricity of a moving visual surround influence manual and postural control. Twelve subjects performed a manual control task (keep an unstable central display level) and a postural control task (maintain an upright stance) while viewing a visual surround that rotated continuously at 25 degrees C/s. The vi...

The discriminability of crossed-disparity (near) and uncrossed-disparity as a function of their location in the upper-left, upper-right, lower-left, and lower-right quadrants of the visual field. Discriminability was assessed using choice reaction-time (RT) and accuracy measures. While near targets were recognized equally well in the upper and lowe...

A critique of the article by Bryden, McManus, and Bulman-Fleming ("Evaluating the empirical support for the Geschwind-Behan-Galaburda model of cerebral lateralization") is presented. Bryden et al. expose some of the principal weaknesses of the cerebral lateralization model put forth by Geschwind and colleagues and contribute an important meta-analy...

Previous data suggest that vertical imbalances between the eyes produced by lateral head tilt are linked to ocular dominance, but no studies have heretofore objectively measured head tilt in addressing this relationship. Photographic measurements of the head tilt of 70 subjects were made, along with measures of sighting dominance and vertical misal...

Feature-conjunction search performance was investigated as a function of the target's location in three-dimensional (3-D) space. Ten subjects viewed a display that contained 36 shapes, one of which was the target. The targets were presented in one of four quadrants, three depths, and three eccentricities. On a given trial, nontarget distractor shap...

Human spatial orientational mechanisms, and how those mechanisms fail in flight, are discussed in detail in this comprehensive review. Specific topics include: mechanics and associated physiologic nomenclature; visual orientation; vestibular function and information processing; other orientational senses; spatial disorientation, including definitio...

The effects of background visual roll stimulation on postural control, manual control, and self-motion perception were investigated in this study. In the main experiment, 8 subjects were exposed to wide field-of-view background scenes that were tilted and static, continuously rotating, or sinusoidally rotating at frequencies between 0.03 and 0.50 H...

It has long been recognized that the vestibular system plays a major role in autonomic control. The nature of this control remains in dispute, however, as some evidence points to a vestibularly mediated parasympathetic activation, whereas other evidence points to a sympatho-excitatory role for labyrinthine outputs. A theoretical explanation is offe...

The relationship between the effects of visual-surround roll motion on compensatory manual tracking of a central display and the perceptual phenomena of induced motion and vection were investigated. To determine if manual-control biases generated in the direction of surround rotation compensate primarily for the perceived counterrotation of the cen...

A survey of the literature concerning motoric laterality in strabismus was undertaken. The assessment of manual and ocular dominance was based on a total of eleven studies conducted between 1934 and 1986. The average percentage of right-handedness in strabismics was 73.8%, whereas the average percentage of right-eyedness was 46.9%. Both figures are...

This study attempted to determine which visual scene cues are most effective in overcoming the somatogravic illusion (SGI), a form of spatial disorientation that occurs when a shift in the resultant gravitoinertial force vector created by a sustained linear acceleration is misinterpreted as a change in pitch or bank attitude. Nine subjects were exp...

This study attempted to correlate turning direction on the stepping test with three measures of motoric dominance--handedness, footedness, and eyedness. 111 high school students performed the stepping test while deprived of visual and auditory cues during a 1-min. interval. Although only slightly more than half of the subjects rotated rightward, th...

The effects of background visual roll stimulation on postural control, manual controlf andselfmotion perception were investigated in this study. In the main experiment, 8 subjects were exposed to wide field-of-view background scenes that were tilted and static, continuously rotating, or sinusoidally rotating at frequencies between 0.03 and 0.50 Hz,...

A set of research findings is described that deals with three principal laboratory measures of visual orientation (vection and postural and manual control). Two studies are highlighted, one of which compared the latencies of vection and visually induced postural change and the other of which investigated manual tracking under visually disorienting...

The effects of shifting attention to targets in 3-dimensional (3-D) visual space were investigated. The perceptibility of crossed-disparity (near) and uncrossed-disparity (far) targets located in the upper-left, upper-right, lower-left, and lower-right visual quadrants was measured during attention shifts that were directed by means of centrally pr...

The origins of cerebral lateralization in humans are traced to the asymmetric prenatal development of the ear and labyrinth. Aural lateralization is hypothesized to result from an asymmetry in craniofacial development, whereas vestibular dominance is traced to the position of the fetus during the final trimester. A right-ear sensitivity advantage m...

The origins of cerebral lateralization in humans are traced to the asymmetric prenatal development of the ear and labyrinth. Aural lateralization is hypothesized to result from an asymmetry in craniofacial development, whereas vestibular dominance is traced to the position of the fetus during the final trimester. A right-ear sensitivity advantage m...

Anecdotal evidence suggests that a thumb and index finger grip might facilitate recovery from the manifestation of spatial disorientation known as the giant hand phenomenon. Sixteen pilots volunteered as subjects in an experiment that compared the effectiveness of the thumb and index finger versus the whole hand technique to overcome a visually-ind...

This study compared the latencies of visually induced postural change and self-motion perception under identical visual conditions. The results showed that a visual roll stimulus elicits postural tilt in the direction of scene motion and an increase in postural instability several seconds before the subject begins to perceive illusory self-motion (...

Functional specialization in the lower and upper visual fields in humans is analyzed in relation to the origins of the primate visual system. Processing differences between the vertical hemifields are related to the distinction between near (peripersonal) and far (extrapersonal) space, which are biased toward the lower and upper visual fields, resp...

Head-up display (HUD) research has centered on modifications to the basic aircraft control symbology—the pitch-ladder lines. Although some of these modifications have led to minor improvements in attitude recognition, major problems still exist: pilots continue to experience spatial disorientation and to complain of occlusion due to the HUD symbols...

New concepts in HUD symbology, based on an understanding of the physiological mechanisms and ecological origins of the human visual system are described which may enable future HUD displays to serve as primary flight directors in addition to their current roles. The four key elements of this new symbology are: a) prioritization of space according t...

Color-specific visual impairments following exposure to intense laser flashes were investigated using visual evoked potentials (VEPs) recorded from four anesthetized rhesus monkeys. Steady-state VEPs were recorded from the primary visual cortex in response to counterphasing high-contrast sine-wave gratings composed of either luminance contrast (red...

The origins and implications of frequency-doubling (i.e., the dominance of the 4th-harmonic response instead of the reversal response) in the visual evoked potential (VEP) were investigated. Previous research demonstrated that frequency-doubling occurs in humans when sinusoidal but not square-wave luminance modulation is used to elicit the VEP, but...

A comparison between the effects of single and multiple laser pulse-trains of equivalent energy was performed. Visual evoked potentials (VEPS) recorded bipolarly from the visual cortex of two rhesus monkeys in response to a counterphasing grating were used to assess the magnitude of the visual loss following four types of exposures: single and mult...

Several investigators have noted that the suprathreshold visual evoked potential (VEP) characterizes spatiotemporal tuning in primates in different ways than do psychophysical measures. In particular, narrow spatial and temporal tuning (often surrounding multiple peaks) have frequently been observed (1), and in many cases, the peak of the spatial t...

The spatial and temporal tuning of the luminance and chromatic systems were investigated using visual evoked potentials (VEPs) recorded from rhesus monkeys. VEPs were recorded from eight bipolar electrodes which were chronically implanted in the foveal projection region of area 17 in two monkeys. They were elicited by luminance (yellow-black) and c...

The effects of Q-switched (20-ns) doubled-neodymium (Nd-2) laser flashes upon the visual evoked potential (VEP) of two rhesus monkeys were studied and compared with the effects of 100-ms argon laser flashes described previously. VEP's were recorded under barbiturate anesthesia using bipolar electrodes chronically implanted in foveal striate cortex,...

The visual evoked potential (VEP) in four rhesus monkeys was used to assess the transient loss of visual function resulting from single 100-ms argon laser flashes (476.5 and 514.5 nm) whose energy levels did not exceed the maximum permissible exposure (MPE). VEP's were elicited by high-contrast square-wave test gratings which were phase-reversed at...

A technique was designed to align the rhesus monkey visual axis with a predetermined fixation point on a visual stimulus screen using a helium-neon laser and funduscope.

The differences between the left and right cerebral hemispheres in terms of visual pattern recognition were examined within the context of the spatial filtering model of visual perception. On the basis of a wide range of evidence, it was hypothesized that the right hemisphere's predominant role in Gestalt perception may be related to its superiorit...