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PubMed2001

Attentional capture by color without any relevant attentional set.

The aim of the present study was to investigate mechanisms underlying attentional capture by color. Previous work has shown that a color singleton is able to summon attention only in the presence of a relevant attentional set, whereas when a color singleton is not useful for a task, evidence for purely stimulus-driven attentional capture is controversial. Three visual search experiments (T-L task) were conducted using a method different from that based on set sizes, consisting of monitoring target-singleton distance in a unique display size. In Experiment 1, we demonstrated that attention can be summoned in a real stimulus-driven manner by an irrelevant color singleton. Experiment 2A extended this observation, showing that the color singleton attracted attention even when capture was detrimental. However, Experiment 2B showed that such capture can be strategically prevented. Finally, in Experiment 3, we examined whether such a capture was due to a spatial shift or to a filtering cost, providing evidence supporting the shift hypothesis. Stimulus-driven capture was observed when color was neither the defining nor the reported target attribute (Yantis, 1993) and when subjects naive of visual search tasks were used. The present results give experimental support to many contemporary models of visual attention.

Adult↗
PubMed2003

Anterior and posterior attentional control systems use different spatial reference frames: ERP evidence from covert tactile-spatial orienting.

To investigate whether processes controlling preparatory covert shifts of spatial attention operate within external and anatomically defined spatial coordinates, lateralized event-related potentials components sensitive to the direction of attentional shifts were measured in response to visual precues directing attention to the relevant location of tactile events. Participants had to detect infrequent tactile targets delivered to the hand located on the cued side. In different blocks, hands were uncrossed or crossed, so that external and anatomical codes specifying task-relevant locations were either congruent or incongruent. With uncrossed hands, an anterior directing attention negativity and a posterior directing attention positivity were elicited in the cue-target interval contralateral to the side of a cued attentional shift. Although the posterior effect was unaffected by hand posture, the anterior effect was delayed and reversed polarity with crossed relative to uncrossed hands. This pattern of results provides new evidence that different spatial coordinate systems may be used by separable attentional control processes. It is suggested that a posterior process operates on the basis of external spatial coordinates, whereas an anterior process is based primarily on anatomically defined spatial codes.

Adult↗
PubMed1979

The monkey's prefrontal cortex functions in motor programming.

A new experimental approach is presented which resulted in clarification of the specific functions of the monkey’s prefrontal cortex. Monkeys with chronically implanted transcortical nonpolarizable electrodes were trained on delayed response (DR) and visual delayed matching-to-sample (DMS) tasks. The onset of the trial for each group depended upon on-line computer detection of one of the specified events: FN – surface-negative steady potential shifts (SPS) from principalis cortex; MN – a similar SPS from precentral cortex; FB – near baseline SP from principalis cortex; LEM – rightward eye deviations; and YC – controls, with intertrial intervals yoked to those of other monkeys. Monkeys were trained with 1-s cue presentations. on successive delays of 2 to 12 s. The DR acquisition rate by the FN group was substantially faster than that of any other group, as indicated by its mean error that was only 17.24 percent the YC group’s error. The MN and LEM monkeys acquired the task at the same rates as the YCs, while the FB monkeys were the slowest learners. The correct DR performance transferred to testing with constant intertrial intervals (without preconditions). Subsequent on-line tests with brief (0.1 s) cue duration showed high DR performance by the FN, but not by other groups. No similar rapid learning was found with the DMS task. The findings from this, and other experiments, suggest that the major function of principalis cortex is the selection, or programming of delayed spatial choice responses. The view seems consonant with interpretations for the role of the human prefrontal cortex.

Animals↗
PubMed2005

"Phase capture" in amblyopia: the influence function for sampled shape.

This study was concerned with what stimulus information humans with amblyopia use to judge the shape of simple objects. We used a string of four Gabor patches to define a contour. A fifth, center patch served as the test pattern. The observers' task was to judge the location of the test pattern relative to the contour. The contour was either a straight line, or an arc with positive or negative curvature. We asked whether phase shifts in the inner or outer pairs of patches distributed along the contour influence the perceived shape. That is, we measured the phase shift influence function. Our results, consistent with previous studies, show that amblyopes are imprecise in shape discrimination, showing elevated thresholds for both lines and curves. We found that amblyopes often make much larger perceptual errors (biases) than do normal observers in the absence of phase shifts. These errors tend to be largest for curved shapes and at large separations. In normal observers, shifting the phase of inner patches of the string by 0.25 cycle results in almost complete phase capture (attraction) at the smallest separation (2 lambda), and the capture effect falls off rapidly with separation. A 0.25 cycle shift of the outer pair of patches has a much smaller effect, in the opposite direction (repulsion). While several amblyopic observers showed reduced capture by the phase of the inner patches, to our surprise, several of the amblyopes were sensitive to the phase of the outer patches. We used linear multiple regression to determine the weights of all cues to the task: the carrier phase of the inner patches, carrier phase of the outer patches and the envelope of the outer patches. Compared to normal observers, some amblyopes show a weaker influence of the phase of the inner patches, and a stronger influence of both the phase and envelope of the outer patches. We speculate that this may be a consequence of abnormal "crowding" of the inner patches by the outer ones.

Adult↗
PubMed2000

Synchronizing effect of clock rhythm on the 'when to move' decision in repeated voluntary movements.

In 13 volunteers, surface EEGs from F(z), C(z), C(3), C(4), and P(z) electrodes and EMG from the flexor digitorum communis were recorded during an experimental task in which the performance of wrist flexion was linked with the selection of a clock sound. In the epoch from 4 to 1 s before movement, more than 95% of the records exhibited a small negative shift from the baseline. The position of these shifts on the time axis made it possible to create groups of time trials. The average EEG curves from these groups showed one prominent negative shift from the baseline, which could be related to the position of particular clock sounds. The slope values of these shifts were highest under the F(z) and C(z) electrodes. We suggested that these negative shifts coincided with 'when to move' decisions, which preceded the execution of the movement at varying intervals.

Adult↗
PubMed1997

Decreased attentional responsivity during sleep deprivation: orienting response latency, amplitude, and habituation.

Ever increasing societal demands for uninterrupted work are causing unparalleled amounts of sleep deprivation among workers. Sleep deprivation has been linked to safety problems ranging from medical misdiagnosis to industrial and vehicular accidents. Microsleeps (very brief intrusions of sleep into wakefulness) are usually cited as the cause of the performance decrements during sleep deprivation. Changes in a more basic physiological phenomenon, attentional shift, were hypothesized to be additional factors in performance declines. The current study examined the effects of 36 hours of sleep deprivation on the electrodermal-orienting response (OR), a measure of attentional shift or capture. Subjects were 71 male undergraduate students, who were divided into sleep deprivation and control (non-sleep deprivation) groups. The expected negative effects of sleep deprivation on performance were noted in increased reaction times and increased variability in the sleep-deprived group on attention-demanding cognitive tasks. OR latency was found to be significantly delayed after sleep deprivation, OR amplitude was significantly decreased, and habituation of the OR was significantly faster during sleep deprivation. These findings indicate impaired attention, the first revealing slowed shift of attention to novel stimuli, the second indicating decreased attentional allocation to stimuli, and the third revealing more rapid loss of attention to repeated stimuli. These phenomena may be factors in the impaired cognitive performance seen during sleep deprivation.

Attention↗
PubMedDate not supplied

Job evaluation in worker fitness determination.

To assess work fitness on a placement exam requires detailed assessment of repetitive manual capabilities specific for the job, ability to withstand static loading of the back and other muscle groups in the working position, and tolerance of the heat and humidity conditions of the work environment. Less specific tests, such as aerobic capacity stress tests, grip strength, and back examination may not accurately reflect the demands of repetitive job activities and, therefore, may not satisfy the legal requirements of Title VII. Only occasionally will a job analysis lead to the establishment of a concrete capacity standard against which a potential worker's fitness or risk for injury can be measured in the physician's office. The most valuable contributions of a careful, quantitative job analysis are likely to be the identification of particular anatomic structures (e.g., joints and muscles) that will be subjected to high stress and a clear understanding of the job so that reasonable accommodation of the worker or modifications of the job and workplace can be considered. In summary, the following observations can be made: 1. Intensity of effort, continuous duration of effort, and frequency of repetition are the key factors for evaluating the physical demands on muscle groups during work. 2. Intensity of effort can be estimated by using psychophysical scaling techniques and by obtaining ratings from several people. 3. Timing the effort and recovery times for specific muscle groups during a task of interest can be used to quantify the possible fatigue. It will also provide information about ways to improve the task to bring it within the capabilities of more people. 4. Total workload is most easily evaluated by using estimation methods or lists of comparable jobs and then performing a time-weighted calculation of the full shift's work requirements. The workload should be related to the aerobic capacities of the active muscles. 5. Environmental heat and humidity reduce work capacity and must be factored into any assessment of job suitability. 6. Psychological and perceptual job demands should be assessed by defining the requirements for multiple-task performance or monitoring and by evaluating the environment for visual or auditory work. Accountability without control in the job should also be identified. 7. Many of the factors that make jobs difficult can be remedied without extensive cost to the employer. The job-evaluation techniques given in this chapter can help to identify the most effective ways to make changes in the job requirements.(ABSTRACT TRUNCATED AT 400 WORDS)

Ergonomics↗
PubMed2006

Subjective somatosensory vertical during dynamic tilt is dependent on task, inertial condition, and multisensory concordance.

To investigate how visual and vestibular cues are integrated for the perception of gravity during passive self-motion, we measured the ability to maintain a handheld object vertical relative to gravity without visual feedback during sinusoidal roll-tilt stimulation. Visual input, either concordant or discordant with actual dynamic roll-tilt, was delivered by a head-mounted display showing the laboratory. The four visual conditions were darkness, visual-vestibular concordance, stationary visual scene, and a visual scene 180 degrees phase-shifted relative to actual tilt. Tilt-indication performance using a solid, cylindrical joystick was better in the presence of concordant visual input relative to the other visual conditions. In addition, we compared performance when indicating the vertical by the joystick or a full glass of water. Subjects indicated the direction of gravity significantly better when holding the full glass of water than the joystick. Matching the inertial characteristics, including fluid properties, of the handheld object to the glass of water did not improve performance. There was no effect of visual input on tilt performance when using the glass of water to indicate gravitational vertical. The gain of object tilt motion did not change with roll-tilt amplitude and frequency (+/-7.5 degrees at 0.25 Hz, +/-10 degrees at 0.16 Hz, and +/-20 degrees at 0.08 Hz), however, the phase of object tilt relative to subject tilt showed significant phase-leads at the highest frequency tested (0.25 Hz). Comparison of the object and visual effects observed suggest that the task-dependent behavior change may be due to an attentional shift and/or shift in strategy.

Attention↗
PubMed1978

Shifts in attention demands and motor program utilization during motor learning.

The relationship between changes in the level of motor program utilization and attention demand during the learning of a motor task was examined. The primary task involved an 86-cm horizontal arm movement which subjects attempted to complete coincident with the end of a 360 degrees sweep of a clock hand. A secondary task performed with the opposite limb required a rapid button press to an auditory probe stimulus presented at various temporal locations within each trial. Control subjects performed either the primary task or the secondary task alone, while experimental subjects performed both tasks in combination. Schmidt's (1972) index of preprogramming was used to measure the level of motor program utilization, while probe reaction time reflected the attention demand of the primary task. There was a stable level of motor programming over four consecutive days of practice (100 trials a day), but a general decrease in attention demand. Implications for an expansion of the concept of the motor program were discussed.

Journal Article↗
PubMed2005

Attentional shifts towards an expected visual target alter the level of alpha-band oscillatory activity in the human calcarine cortex.

Neuronal operations associated with the top-down control process of shifting attention from one locus to another involve a network of cortical regions, and their influence is deemed fundamental to visual perception. However, the extent and nature of these operations within primary visual areas are unknown. In this paper, we used magnetoencephalography (MEG) in combination with magnetic resonance imaging (MRI) to determine whether, prior to the onset of a visual stimulus, neuronal activity within early visual cortex is affected by covert attentional shifts. Time/frequency analyses were used to identify the nature of this activity. Our results show that shifting attention towards an expected visual target results in a late-onset (600 ms postcue onset) depression of alpha activity which persists until the appearance of the target. Independent component analysis (ICA) and dipolar source modeling confirmed that the neuronal changes we observed originated from within the calcarine cortex. Our results further show that the amplitude changes in alpha activity were induced not evoked (i.e., not phase-locked to the cued attentional task). We argue that the decrease in alpha prior to the onset of the target may serve to prime the early visual cortex for incoming sensory information. We conclude that attentional shifts affect activity within the human calcarine cortex by altering the amplitude of spontaneous alpha rhythms and that subsequent modulation of visual input with attentional engagement follows as a consequence of these localized changes in oscillatory activity.

Adult↗
PubMed1997

Frontal interhemispheric asymmetry: self regulation and individual differences in humans.

Sixteen subjects naive to biofeedback learned lateralised interhemispheric control of slow cortical potentials (SCPs) across electrode sites F3-F4 during three sessions of visual electroencephalograph (EEG) biofeedback. Subjects were required to generate slow negativity shifts either towards the left or the right hemisphere in sixty pseudorandomly ordered trials per session. Group 1 (n = 8) were told to use emotional strategies in the task (positive emotions for left hemisphere activation, negative emotion for right hemisphere activation), group 2 received no guidance. Both groups received feedback in the form of an on-screen rocket-ship, initially centrally placed, which rose to indicate an increase in left hemisphere negativity (relative to the right hemisphere) and fell to indicate an increase in right hemisphere negativity (relative to the left hemisphere). A 2 x 3 x 3 x 2 ANOVA (group x session x block x trial) showed no performance differences between the strategy and no strategy groups. Both groups learned to produce correct direction shifts in the final third of each session during both trial types (P < 0.001). The no strategy group showed a particularly strong within session learning effect (P < 0.0037) with poor performance in the early part of the sessions, and strong shifts at the end. Subjects high on withdrawal showed stronger rightward shifts in keeping with right hemisphere involvement in behavioural withdrawal. This is the first demonstration of self regulation of interhemispheric frontal asymmetry.

Adult↗
PubMed2006

Rightward shift of the auditory subjective straight ahead in right- and left-handed subjects.

While spatial asymmetries have been extensively investigated in the visual modality and to a lesser degree in the tactile modality, there are no reports on auditory spatial asymmetries in neurologically normal subjects. The subjects in this study performed an auditory midline task in which they had to adjust the level of two sounds that were presented simultaneously in different hemispaces so as to make the perceived fused sound appear to emanate from the midsagittal plane. The results showed that subjects reported a sound to be central when it was lateralized to the left (i.e., more intense at the left ear), as if there were a rightward shift in the perceived location. This rightward shift was more pronounced in left-handed than in right-handed subjects, even though all the subjects had to use both hands to adjust the sound level. Gaze direction significantly modulated the shift of the perceived auditory midline: the rightward shift was maximal when the subjects' gaze direction was central and 30 degrees to the right, while it disappeared when the gaze was directed 30 degrees to the left side. These results are compared with data obtained from neglect patients in previous studies and are discussed in terms of the interaction between asymmetrical hemispheric activations in auditory spatial tasks and an asymmetrical allocation of attention between the left and right hemispaces.

Acoustic Stimulation↗
PubMedDate not supplied

Persisting and unaltered circadian rhythms of six healthy young men with a night-work shift every 48 hrs and a 2% CO2 atmosphere during a 4-week span.

Six apparently healthy young males (20 +/- 0.5 years of age) lived in a specially designed laboratory for a 1-week span in normal air, followed by 4 weeks in a 2% CO2 atmosphere and thereafter 1 week again in normal air. Room temperature was 24 degrees C. +/- 1 degrees C.; relative hygrometry 75% +/- 5%. With respect to socio-ecologic time clues and cues, the subjects were not isolated. The subjects' social synchronization was altered only by the shift-work schedule (light-on, 07(00); light-off, 22(30) on normal days). Every other day each subject had a 3-h night task, located between 23(00) and 07(00). Once a week, during 48 hrs (Saturday and Sunday) a set of physiologic variables was documented every 4 hrs in order to study their circadian changes: oral temperature, peak expiratory flow, grip strength, arterial blood pressure, tempo, and urinary pH, volume and potassium excretion. As far as rhythms are detectable (cosinor method) the most striking result is that both rhythm acrophases and amplitudes do not show any statistically significant changes when comparing either night-work versus day-work and/or normal air versus air with 2% CO2. Both 3 hrs of night-work every other day and an unusual amount of CO2 do not alter the parameters characterizing the circadian rhythms considered. The absence of desynchronization during night-work could be related to: 1) the speed of rotation in the shift-work; 2) the short duration of night-work; and 3) the youth of the subjects.

Adult↗
PubMed1987

'Mental' in 'Southie': individual, family, and community responses to psychosis in South Boston.

The deinstitutionalization of psychiatric patients is a deeply cultural as well as political task. It entails the sharing of responsibility for human distress with family and community. Consequently, the locus of social control has also shifted from psychiatric and medical expertise to community and legal institutions. Diagnosis and treatment models must be more compatible with lay explanatory models. This paper explores the various meanings of "going 'mental"' and "being 'mental"' in the white, working class, ethnic neighborhood of South Boston. The data are extracted from a study of the impact of deinstitutionalization on a cohort of middle-aged, psychiatric patients discharged from Boston State Hospital in the attempt to return them to community living. Individual, family, and community responses to, and interpretations of, the symptoms of mental distress are discussed. The study indicates that even seriously disturbed individuals are sensitive to cultural meanings and social cues regarding the perception, expression, and content of psychiatric episodes. While madness invariably disenfranchises, it does not necessarily deculturate the individual.

Alcoholism↗
PubMed1993

The role of compensatory eye and head movements in the rat for image stabilization and gaze orientation.

Compensatory horizontal eye movements of head restrained rats were compared with compensatory horizontal eye-head movements of partially restrained rats (head movements limited to the horizontal plane). Responses were evoked by constant velocity optokinetic and vestibular stimuli (10-60 degrees/s) and recorded with search coils in a rotating magnetic field. Velocity and position components of eye and head responses were analysed. The velocity gains of optokinetic and vestibular responses of partially restrained and of head restrained rats were similarly high (between 0.8 and 1.0). Eye movements in partially restrained rats also contributed most (about 80%) to the velocity components of the responses. At stimulus velocities above 10 degrees/s, the "beating field" of the evoked optokinetic and vestibular nystagmus was shifted transiently in the direction of ocular quick phases. The amplitude of this shift of the line of sight was about 3-10 degrees in head restrained and about 20-30 degrees in partially head restrained rats. Most of this large, transient gaze shift (about 80%) was accomplished by head movements. We interpret this gaze shift as an orienting response, and conclude that the recruitment of the ocular and the neck motor systems can be independent and task specific: head movements are primarily used to orient eye, ear and nose towards a sector of particular relevance, whereas eye movements provide the higher frequency dynamics for image stabilization and vergence movements.

Animals↗
PubMed1982

Arm trajectory formation in monkeys.

The formation of forearm trajectories of moderate velocities (0.3-1.3 rad/s) was studied in monkeys performing a simple visuomotor task. The experiments were designed to test the hypothesis that the transition from one position to another is subserved by a rapid shift to a final equilibrium of forces in agonist and antagonist muscles. This idea is attractive because it suggests the possibility that in simple movements the trajectory is determined by the inherent inertial and viscoelastic properties of the limb and muscles around a joint. The results indicate that these moderate speed movements are controlled by a gradual, and not a step-like, shift to the final equilibrium position.

Afferent Pathways↗
PubMed1991

Paternal alcohol consumption in the rat impairs spatial learning performance in male offspring.

Pubescent (30 day old) male rats were maintained on an alcohol liquid diet containing 35% ethanol-derived calories (ALC) for 39 days or were pairfed an isocaloric control diet (PF). The concentration of alcohol in the diet was gradually increased to permit adaptation, then stabilized and then gradually tapered to prevent an alcohol withdrawal syndrome. Following a drug-free period (2 weeks), the males were mated with nontreated females. Offspring were evaluated on several developmental indices and on various learning/memory tasks to assess functional deficits in adulthood. Offspring sired by ALC-treated males did not differ from the offspring of PF males on several developmental parameters including body weights, when developmental landmarks appeared, or on tests of sensorimotor development. As adults, male offspring groups did not differ on tests of activity or on an object exploration/recognition task. However, male offspring of ALC-treated males demonstrated impaired acquisition performance (days and errors to criterion) on a win-shift spatial discrimination in an eight-arm radial maze and on a win-stay discrimination (days to criterion) conducted in a T-maze at a later age. The radial maze results were replicated in a subsequent experiment using different groups of rats.

Alcohol Drinking↗