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PubMed1996

Involvement of the olivocochlear bundle in the detection of tones in noise.

To investigate the involvement of auditory efferents in hearing-in-noise in humans, olivocochlear bundle (OCB) functioning and detection-in-noise abilities were compared in 30 subjects. OCB function was assessed in terms of contralateral attenuation of evoked otoacoustic emissions (EOAE): i.e., the reduction in EOAE amplitude elicited by a 30-dB SL contralateral broadband noise. Correspondingly, the detection thresholds for 1- and 2-kHz tone pips embedded in 50-dB SPL broadband noise were measured in the same ear as the EOAEs, successively in the presence and in the absence of a 30-dB SL broadband noise in the opposite ear. The shifts in detection threshold induced by the contralateral stimulation could thus be compared to those in EOAEs. The results indicated significant statistical correlations between the contralateral attenuation of EOAEs and (1) the detection threshold of the 2-kHz signal and (2) the contralaterally induced shift in the 1- and 2-kHz thresholds. Furthermore, the correlation between contralaterally induced reduction of EOAE amplitude and contralaterally induced threshold shift was observed only in the group of subjects who had first performed the detection task in the presence of contralateral stimulation. These results, which suggest that OCB is involved in detection of tones in noise in humans, are discussed in relation to previous physiological and behavioral studies of OCB function.

Acoustic Stimulation↗

PubMed1981

Electrical potentials in human brain during cognition: new method reveals dynamic patterns of correlation.

A new technique has been developed for identifying, in humans, dynamic spatiotemporal electrical patterns of the brain during purposive behaviors. In this method, single-trial time-series correlations between brain macropotentials recorded from different scalp sites are analyzed by distribution-independent mathematical pattern recognition. Dynamic patterns of correlation clearly distinguished two brief visuomotor tasks differing only in type of mental judgement required (spatial or numeric). These complex patterns shifted in the anterior-posterior and left-right axes between successive 175-millisecond intervals, indicating that many areas in both cerebral hemispheres were involved even in these simple judgements. These patterns were not obtainable by conventional analysis of averaged evoked potentials or by linear analysis of correlations, suggesting that the new technique will advance the study of human brain activity related to cognition and goal-directed behaviors.

Adult↗

PubMed1997

Neuropsychological findings in a sample of Operation Desert Storm veterans.

In response to ongoing complaints of memory, attention, and problem-solving difficulties among veterans of Operation Desert Storm and Shield (ODSS), a sample of 44 male veterans of ODSS underwent a comprehensive neuropsychological evaluation. Deficits relative to normative data were observed only on finger dexterity (Grooved Pegboard, bilaterally) and the Stroop Color and Word Test. Those with impaired Pegboard performance had lower performance on other tasks requiring psychomotor speed. Those with impaired Stroop had significantly lower motor and set-shifting performance. Scores of both impaired groups were higher on many clinical and supplemental scales of the MMPI. Despite subjective cognitive complaints reported in 39% of the overall sample, veterans with cognitive complaints differed from their peers primarily in greater psychological distress as depicted on the MMPI. The data are presented as preliminary clinical findings.

Adult↗

PubMed1996

Effect of window size on detection acuity and resolution acuity for sinusoidal gratings in central and peripheral vision.

Detection and resolution of square patches of sinusoidal gratings were measured in central and peripheral vision (30 degrees horizontal temporal visual field) for high-contrast gratings as a function of the number of cycles in the stimulus. We determined performance in a forced-choice paradigm for a fixed number of stimulus cycles by arranging for stimulus diameter to vary inversely with spatial frequency. For both psychophysical tasks and for both target locations, the psychometric function relating performance to log spatial frequency shifted to higher frequencies without changing slope significantly as the number of cycles in the stimulus was increased. Thus the entire effect could be captured by an analysis of spatial acuity, which increased with increasing number of grating cycles over the range 0.5-6 cycles but remained constant over the range 6-14 cycles. In the central field, resolution acuity and detection acuity were equal regardless of the number of cycles in the stimulus. In the peripheral field, detection acuity exceeded resolution acuity and perceptual aliasing occurred for stimuli in the range 1-14 cycles. From this result we conclude that resolution acuity is sampling limited in the periphery, provided that the stimulus contains at least one full cycle of the grating. Essential features of the results could be accounted for by Fourier analysis of the stimulus.

Fovea Centralis↗

PubMed1996

An effect of alcohol on the distribution of spatial attention.

OBJECTIVE: Previous research on the effects of alcohol on visual performance led us to the prediction that alcohol should interfere with the distribution of visual spatial attention. This prediction was examined in two experiments that measured the effect of alcohol on reaction time (RT) for tasks that differed in visual spatial attention requirements. METHOD: In the first experiment, 48 adult volunteers (33 female) responded to either the onset or offset of one of five potential targets without alcohol to determine the relative demands on attention of stimulus onset and offset. The spatial extent of the five-target display was also varied. In the second experiment, the effect of alcohol was determined for both the onset and the offset tasks in 12 adult volunteers (nine female). RESULTS: The offset task was found to place greater demands on spatial attention as the increase in display area result in relatively greater increases in RT. Alcohol increased RT in the offset task for the larger, but not the smaller, display, and there were no significant effects of alcohol for the onset task. CONCLUSIONS: The results indicate that alcohol impairs performance on tasks that place greater demands on visual spatial attention and likely disrupts the ability to shift attention from one spatial locus to another during serial search.

Adolescent↗

PubMed2005

Multiplex approaches in protein microarray technology.

The success of genome sequencing projects has provided the basis for systematic analysis of protein function and has led to a shift from the description of single molecules to the characterization of complex samples. Such a task would not be possible without the provision of appropriate high-throughput technologies, such as protein microarray technology. In addition, the increasing number of samples necessitates the adaptation of such technologies to a multiplex format. This review will discuss protein microarray technology in the context of multiplex analysis and highlight its current prospects and limitations.

Animals↗

PubMedDate not supplied

Advances in anterior cruciate ligament surgery.

The anterior cruciate ligament is the most frequently torn ligament in the knee. Diagnosis of cruciate ligament tears is often a difficult task. Tests typically used in diagnosis are the anterior drawer test, Lachman's test, pivot shift test, and the flexion rotation drawer. Arthroscopy has increasingly become the standard for the diagnosis of anterior cruciate ligament tears. Management of these tears has been controversial. The diagnostic techniques are discussed and a surgical technique is described for anterior cruciate ligament reconstruction as an outpatient procedure. The middle one-third of the patellar tendon is used as a graft, harvested subcutaneously, and fixed with interference fit screws. The postoperative function of anterior cruciate ligament deficient knees has been quite satisfactory. Morbidity is decreased relative to open surgical inpatient procedures. Finally, overall cost to the patient has been significantly reduced.

Anterior Cruciate Ligament↗

PubMed1995

[Evaluation of the health status of stonemasons].

Thorough study of work conditions and health state of stone masons proved physical overload to be a principal factor in charge of the occupational diseases. The physical overload is associated with prevalent manual tasks, frequent monotonous movements, lifting and manual carriage of heavy net weight during the working shift, uncomfortable working postures, unfavorable climate conditions. Nearly half (55.9%) of the examinees were diagnosed as having peripheral neurologic disorders and locomotion diseases--autonomous and sensory polyneuropathy, "frozen shoulder" syndrome, shoulder epicondylitis.

Adult↗

PubMed2006

How attention enhances spatial resolution: evidence from selective adaptation to spatial frequency.

In this study, we investigated how spatial resolution and covert attention affect performance in a texture segmentation task in which performance peaks at midperiphery and drops at peripheral and central retinal locations. The central impairment is called the central performance drop (CPD; Kehrer, 1989). It has been established that attending to the target location improves performance in the periphery where resolution is too low for the task, but impairs it at central locations where resolution is too high. This is called the central attention impairment (CAI; Yeshurun & Carrasco, 1998, 2000). We employed a cuing procedure in conjunction with selective adaptation to explore (1) whether the CPD is due to the inhibition of low spatial frequency responses by high spatial frequency responses in central locations, and (2) whether the CAI is due to attention's shifting sensitivity to higher spatial frequencies. We found that adaptation to low spatial frequencies does not change performance in this texture segmentation task. However, adaptation to high spatial frequencies diminishes the CPD and eliminates the CAI. These results indicate that the CPD is primarily due to the dominance of high spatial frequency responses and that covert attention enhances spatial resolution by shifting sensitivity to higher spatial frequencies.

Attention↗

PubMed1998

Vernier and letter acuities for low-pass filtered moving stimuli.

Vernier and letter acuities are both susceptible to degradation by image motion. In a previous study, we showed that the worsening of Vernier acuity for stimuli moving up to 4 degrees/s is accounted for primarily by a shift of visual sensitivity to mechanisms of lower spatial frequency. The purposes of this study were to extend the previous results for Vernier acuity to higher stimulus contrast and velocities, and to determine if a shift in spatial scale can similarly explain the degradation of letter acuity for moving stimuli. We measured Vernier discrimination for a pair of vertical abutting thin lines and letter resolution for a four-orientation letter 'T' as a function of stimulus velocity ranging from 0 to 12 degrees/s. Stimuli were presented at 20 times the detection threshold, determined for each velocity. To determine the spatial-frequency mechanism that mediates each task at each velocity, we measured Vernier and letter acuities with low-pass filtered stimuli (cut-off spatial-frequency: 17.1-1.67 c/deg) and analyzed the data using an equivalent blur analysis. Our results show that the empirically determined, equivalent intrinsic blur associated with both tasks increases as a function of stimulus velocity, suggesting corresponding increases in the size of optimally responding mechanisms. This progressive increase in mechanism size can account for the worsening of Vernier and letter acuities with velocity. Vernier discrimination is found to be more susceptible to degradation by various stimulus parameters than letter resolution, suggesting that different mechanisms are involved in the two tasks. We conclude that the elevations in Vernier and letter acuities for moving stimuli are the consequence of a shift of visual sensitivity toward mechanisms of lower spatial frequencies.

Female↗

PubMed2003

Identifying dead regions in the cochlea: psychophysical tuning curves and tone detection in threshold-equalizing noise.

OBJECTIVE: Recent studies indicate that high-frequency amplification may provide little benefit for listeners with moderate-to-severe high-frequency hearing loss, and may even reduce speech recognition. Moore and colleagues have proposed a direct link between this lack of benefit and the presence of regions of nonfunctioning inner hair cells (dead regions) in the basal cochlea and have suggested that psychophysical tuning curves (PTCs) and tone detection thresholds in threshold-equalizing noise (TEN) are psychoacoustic measures that allow detection of dead regions ([Moore, Huss, Vickers, Glasberg, & Alcántara, 2000]; [Vickers, Moore, & Baer, 2001]). The experiments reported here examine the consistency of TEN and PTC tasks in identifying dead regions in listeners with high-frequency hearing loss. DESIGN: Seventeen listeners (18 ears) with steeply sloping moderate-to-severe high-frequency hearing loss were tested in PTC and TEN tasks intended to identify ears with high-frequency dead regions. In the PTC task, pure-tone signals of fixed level were masked by narrowband noise that slowly increased in center frequency. For a range of signal frequencies, noise levels at masked threshold were determined as a function of masker frequency. In the TEN task, masked thresholds for pure-tone signals were determined for a fixed-level, 70 dB/ERB TEN masker (for some listeners, 85 or 90 dB/ERB TEN was also tested at selected probe frequencies). RESULTS: TEN and PTC results agreed on the presence or absence of dead regions at all tested frequencies in 10 of 18 cases (approximately 56% agreement rate). Six ears showed results consistent with either mid- or high-frequency dead regions in both tasks, and four ears did not show evidence of dead regions in either task. In eight ears, the TEN and PTC tasks produced conflicting results at one or more frequencies. In instances where the TEN and PTC results disagreed, the TEN results suggested the presence of dead regions whereas the PTC results did not. CONCLUSIONS: The 56% agreement rate between the TEN and PTC tasks indicates that at least one of these tasks was only partially reliable as a diagnostic tool. Factors unrelated to the presence of dead regions may contribute to excess masking in TEN without producing tip shifts in PTCs. Thus it may be appropriate to view tuning curve results as more reliable in cases where TEN and PTC results disagree. The current results do not provide support for the TEN task as a reliable diagnostic tool for identification of dead regions.

Aged↗

PubMed1995

[Static characteristics of accommodation on the relationship between accommodative resting position and viewing distance].

The steady-state accommodation of subjects during a 15 min visual task was measured in real time by an infrared optometer to investigate the relationship between accommodative resting position and the effect of viewing distance. When the subjects were loaded at 50 cm (closer than their resting state), the steady-state accommodation showed an inward shift which was enhanced when computation was done. On the contrary, when they worked outside their resting position-2m viewing distance-, an outward shift of steady-state accommodation was seen in the control group who reacted only to the visual objects displayed. For the mental task group this was not evident. It appears that the steady-state accommodation is different between the cases of visual stimuli given inside and outside the resting position.

Accommodation, Ocular↗

PubMed2003

Inhibition of return with rapid serial shifts of attention: implications for memory and visual search.

Horowitz and Wolfe (2001) suggested that inhibition of return (IOR) should not be observed in tasks that involve rapid deployments of attention. To examine this issue, five of six possible locations were sequentially cued with either short-duration peripheral cues (50 msec) or long-duration peripheral cues (500 msec). As was expected, IOR was observed in the first two experiments at every cued location with the long-duration cues, with the magnitude of IOR decreasing for earlier cued locations relative to later cued locations. In the short-cue condition, IOR was observed at only one cued location (the second to last). The pattern of results for the short-duration cues was found regardless of whether the fixation cue was of a short (Experiment 1) or a long (Experiment 2) duration. In Experiment 3, the final fixation cue was removed, and IOR was again observed at virtually all locations in both the short- and the long-cue conditions. These findings indicate that IOR can be observed at multiple locations when attention is shifted rapidly between locations.

Attention↗

PubMed1999

Frontal midline theta rhythms reflect alternative activation of prefrontal cortex and anterior cingulate cortex in humans.

Frontal midline theta rhythm (Fm theta) often appears on electroencephalogram (EEG) during consecutive mental tasks. To clarify the source of rhythmic activity, magnetoencephalogram (MEG) and EEG were simultaneously measured in six healthy volunteers during different mental tasks using whole head MEG system. MEG records were averaged every one cycle of Fm theta rhythms using individual positive peaks of Fm theta waves in Fz EEG as a trigger. Averaged theta components of MEG signals were analyzed with a multi-dipole model. Two sources were estimated to the regions both of the prefrontal-medial superficial cortex and anterior cingulate cortex (ACC). These regions were alternatively activated in about 40 to 120 degrees phase shift during one Fm theta cycle. From above results, we hypothesize that appearance of Fm theta during consecutive mental tasks reflects alternative activities of the medial prefrontal cortex and ACC.

Adult↗

PubMedDate not supplied

Mapping study of somatosensory evoked potentials during selective spatial attention.

We have investigated the effects of selective spatial attention on early and middle-latency SEPs. Baseline control responses to electrical stimulation of 2 digits of the hand were recorded first in conditions of mental relaxation, in the absence of any cognitive task, to obtain truly 'neutral' responses uncontaminated by cognitive components. Then, during a 'task condition,' identical stimuli were applied to the same two fingers, but the subject's attention was driven towards the stimulated territory by the bias of mechanical taps delivered to the same digits. The earliest effect of directing attention towards the territory stimulated was a positive shift on contralateral somatosensory responses, with onset at 27.4 +/- 4 msec post stimulus. This SEP modification: (a) did not entail any change in the scalp distribution of components, as assessed by topographic mapping, and (b) was not present when attention was directed towards the hand contralateral to that receiving electrical stimuli. A second effect was represented by a parieto-central negativity in the 60-80 msec latency range; this feature could also be observed during contralaterally driven attention and was associated with topographical changes in SEP scalp distribution. Finally, a late centro-frontal negativity beginning at 90-100 msec (N140) appeared during ipsilateral attention, while P100 was not enhanced. Subcortical P14 and primary cortical N20 were not significantly affected by the tasks. We conclude that the 'early positive shift' is linked to the spatial aspects of selective attention and represents in part modulation of obligatory components (P25 through P45) existing in control SEPs; it probably corresponds with the deflections with similar polarity and time-course that have been described by others in response to somatosensory target stimuli. Conversely, 60-80 msec negative enhancement is less spatially selective and may represent non-specific arousal effects. The late negative component (N140) shares several features with the 'processing negativity' described in auditory paradigms and could represent the equivalent of this effect in the somatosensory system.

Adult↗

PubMed2004

Effects of the length and timing of nighttime naps on task performance and physiological function.

OBJECTIVE: To examine the effects of the length and timing of nighttime naps on performance and physiological functions, an experimental study was carried out under simulated night shift schedules. METHODS: Six students were recruited for this study that was composed of 5 experiments. Each experiment involved 3 consecutive days with one night shift (22:00-8:00) followed by daytime sleep and night sleep. The experiments had 5 conditions in which the length and timing of naps were manipulated: 0:00-1:00 (E60), 0:00-2:00 (E120), 4:00-5:00 (L60), 4:00-6:00 (L120), and no nap (No-nap). During the night shifts, participants underwent performance tests. A questionnaire on subjective fatigue and a critical flicker fusion frequency test were administered after the performance tests. Heart rate variability and rectal temperature were recorded continuously during the experiments. Polysomnography was also recorded during the nap. RESULTS: Sleep latency was shorter and sleep efficiency was higher in the nap in L60 and L120 than that in E60 and E120. Slow wave sleep in the naps in E120 and L120 was longer than that in E60 and L60. The mean reaction time in L60 became longer after the nap, and faster in E60 and E120. Earlier naps serve to counteract the decrement in performance and physiological functions during night shifts. Performance was somewhat improved by taking a 2-hour nap later in the shift, but deteriorated after a one-hour nap. CONCLUSIONS: Naps in the latter half of the night shift were superior to earlier naps in terms of sleep quality. However performance declined after a 1-hour nap taken later in the night shift due to sleep inertia. This study suggests that appropriate timing of a short nap must be carefully considered, such as a 60-min nap during the night shift.

Adult↗

PubMed1981

Slow potential shifts of human brain during forewarned reaction.

The slow brain potentials observed during the 4 sec interstimulus interval (ISI) of a CNV paradigm were investigated by a factorial manipulation of the parameters that have been identified as affecting the CNV at ISIs of 1 or 2 sec. Subjects performed choice and simple reaction time (RT) tasks under all possible combinations of auditory and visual warning (S1) and imperative (S2) stimuli. The choice task involved easy or difficult intensity discriminations at S2, which were forewarned by S1s that cued the subject as to the level of difficulty for that trial. Principal components analysis (PCA) of the data revealed two negative afterwave factors and a late positive component (LPC) related to warning stimulus variables, and a late negative shift preceding S2 that was related to motor preparation. The negative afterwave components were enhanced in the choice RT task, and the earlier of the two components showed a modality-specific distribution. The LPC factor was also enhanced in the choice task and was further enhanced by S1s signaling difficult discriminations. Additionally, the LPC was larger for visual S1s. The S1-related components are interpreted in terms of orienting, while the later shift is identified with the readiness potential and motor preparation. The results support the notion that the conventionally recorded CNV consists of S1 evoked and response-related potentials rather than non-specific and modality-specific anticipatory potentials.

Action Potentials↗

PubMed1998

Industrial hygiene aspects of a sampling survey at a bleached-kraft pulp mill in British Columbia.

To validate exposure estimates used to investigate correlations between exposure and cancer risk, 1678 personal measurements were collected for 46 job titles during 73 day shifts at a bleached-kraft pulp mill. Measurements included shift-long average and short-term exposures to carbon monoxide, chlorine dioxide (ClO2), and hydrogen sulfide; and shift-long average exposures to calcium oxide and wood dust (WD). Overall results indicate low levels of exposure with a few noteworthy exceptions. Although ClO2 was the exclusive bleaching agent, 77 area samples indicated that chlorine (Cl2), not ClO2 was present in all areas apart from the chemical preparation area (chem-prep) and during a pulp spill. The highest shift-long exposures to Cl2 were measured in the chip yard and are attributed to uncontrolled stack emissions. Finally, WD samples collected from several laborers significantly exceeded regulatory limits, with the highest exposures measured in the steam and recovery area. For short-term exposures to ClO2 in chem-prep, 12 of 17 data-logging electro-chemical sensor sample results showed at least one peak that exceeded the short-term exposure limit of 0.3 ppm. The use of data-logging equipment quantified short-term exposures that previously had been characterized only anecdotally. The peaks were correlated with tasks and upset conditions and, given their transient nature, these exceedances could not have been detected using shift-long average-based sampling devices. Since the respiratory effects of significant short-term exposures to irritant gases such as Cl2 and ClO2 are well-documented, data-logging instruments are necessary to characterize exposures in the pulp and paper industry.

Air Pollutants, Occupational↗