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PubMed1979

Cerebral potentials during smooth goal-directed hand movements in right-handed and left-handed subjects.

During smooth goal-directed hand movements a negative potential shift can be recorded from the human scalp. This goal-directed movement potential (GDMP) is preponderant over central areas with a maximum at the vertex and, over the motor cortex, contralaterally larger than ipsilaterally to the moving hand. In 11 right-handed and 6 left-handed subjects, the morphology and distribution of these potential shifts were studied in relation to task differences, moving hand and handedness. The results show a functional differentiation of two components of the GDMP: (1), a lateralized, slow negative wave, restricted to the precentral area and selectively varying with the hand used, and (2), a widespread, bilateral symmetrical component, selectively influenced by task-specific and individual factors. Two effects reflect an influence of the subject's handedness on the GDMP: (A) averaged for both hand conditions, there are larger amplitudes over the hemisphere contralateral to the dominant hand, and (b), averaged for both hemispheres, larger amplitudes result from using the non-dominant hand.

Adolescent↗

PubMed1992

Late cognitive event-related potentials in adult Down's syndrome.

Event-related electroencephalogram (EEG) potentials (ERPs) using two different tasks were measured in 14 adults with Down's syndrome (DS; mean age 32 years) without clinically detectable cognitive decline. Two groups, young healthy (YH) and old healthy (OH) adults, served as controls. In the oddball task, DS had prolonged N1 and earlier P2 latencies than the control groups. P3 latency was delayed in comparison to YH. In the PushWait task, P3 latency was later in DS than in YH and OH. In both tasks, DS showed a marked amplitude shift towards positivity overlapping the N1-P2 complex and seemingly also P3: The P3 amplitude evoked by target tones and by "Push" was shifted towards anterior sites resulting in a Cz maximum. Changes of the N1 latency and amplitude in DS may be related to enhanced arousal during stimulus processing, indicating a possible defect of central inhibitory mechanisms. The study suggests that differentiated ERP procedures provide information on adult DS cognition exceeding those given by mere P3 latency measurements. Such procedures may be useful in the evaluation of the cognitive decline due to precocious aging or Alzheimer-type dementia in DS.

Adult↗

PubMed1992

EEG spectra in dyslexic and normal readers during oral and silent reading.

EEGs of extensively screened dyslexics and normal readers were recorded while they read easy and difficult texts silently and orally, and during two other verbal tasks which also differed in overt speaking but had no reading component: narrative speaking and listening to a story. Mid-temporal, central and parietal leads were referenced to linked ears and to Cz. Large differences between tasks and between groups were found. With the linked ears reference, power was higher in all bands in oral reading than in silent reading, with the largest change occurring in the temporal leads. In the theta and low beta bands the difference between oral and silent reading was greater for controls than for dyslexics. These effects were not accounted for by differences in reading speed or in difficulty. Similar results were found in two cohorts of subjects. The difference between groups in theta was found only in the reading tasks. In contrast, the group difference in low beta was also found in the change from listening to speaking. This implies that the oral-silent group difference in theta is related to some aspect of the reading tasks other than the presence or absence of overt speaking, and that the low beta group difference is related to some aspect of overt speaking rather than to reading per se. With the Cz reference no group differences were found. It is suggested that the groups differ in the reading strategies they use, and the degree to which they shift strategy between the silent and oral tasks. We hypothesize that these cognitive differences are reflected in the theta activity from the temporal lobe. While there were many differences between the tasks in alpha power and asymmetry, no group differences involving alpha were found.

Adolescent↗

PubMed1978

The central tendency effect in stimulus generalization: the effect of sex of subject.

Eighty male and 80 female college students were shown a stimulus light of 525 nm, following instructions to remember it, and then were immediately tested for generalization (recognition) with a successively presented set of stimuli including 525 nm and six longer wavelength values. Subjects rated each test stimulus on a 6-point scale ranging from "surely same" as the original stimulus to "surely different." Both men and women showed a central tendency shift. Although the stimulus perceived as most likely to be the original (the mode) shifted to 545 nm in both groups, the men showed a greater mean shift than the women. Shifting was nearly complete in both groups within the first series of test stimuli with the men shifting faster. These findings replicate a 1972 report by Giurintano of greater central tendency shift in men than in women in a line angle generalization task, challenging an assumed analogy between our generalization task and the rod-and-frame test, in which women typically show the greater distortion. The analysis of central tendency shift within the first test series reveals that it occurs much earlier than previously believed.

Discrimination, Psychological↗

PubMed1975

Some effects of alcohol on various aspects of oculomotor control.

Recent studies have shown that alcohol interferes with visual control of vestibular nystagmus. The present study was designed to assess three partially independent systems of oculomotor control. Performance on three tasks was measured before and after mild alcohol dosage. One task involved visual suppression of vestibular nystagmus; a second involved smooth oculomotor tracking of a moving target; and a third required repetitive rapid voluntary shifts in gaze. Oculomotor control was degraded on the first two tasks with recovery toward the initial performance level 4 h after drinking. Performance on the third task was not obviously degraded, although it is possible that improvement with practice was retarded. Results are discussed in terms of neurological systems involved and kinds of flight tasks potentially affected.

Aerospace Medicine↗

PubMed1976

Effects of industrialization on working schedules.

Recent increase in industrialization has resulted in attention being drawn to diversity of working schedules and their interrelation with content of work. The results of joint research revealed that adaptation to industrial jobs is made difficult because of urban conditions and modern work-control systems, such as workers in flexible-working-time systems who apparently favored regular daily working cycles. Long overtime work in smaller undertakings and the spread of shift systems are two important features of industrial work schedules, each being dominant among skilled and non-skilled jobs. Another important facet is the problem of intra-shift work-rest schedules significant for machine operations and vigilance tasks. It is suggested that phases of work that become intolerable are correlated with unnatural work rhythms. More emphasis should thus be laid on both phase-shifted work and non-self-governing work, the key factor being the relevance of attained data to real work in the whole course of schedules of work and rest.

Accidents, Occupational↗

PubMed1975

Jamestown Medical Clinic System.

Comprehensive health care can be provided in rural and poor areas despite a decreasing number of physicians in those areas. A single physician increased his productivity by 300% to 400% by combining already available resources: specially trained and supervised nurse-practitioners, problem-oriented charting, and multiphasic screening. With emphasis on the nurse-practitioner as the main "person of contact" for the patient, the physician is able to shift from 50% to 75% of his usual tasks to these specially trained personnel. Patients have come to regard the physician as a "consultant" to the nurse-practitioner.

Community Health Services↗

PubMed1992

Aging and shifts of visual spatial attention.

Three experiments examined adult age differences in the efficiency of endogenous (voluntary) and exogenous (involuntary) attention shifts. Younger and older subjects performed a spatial cuing task in which abruptly onset peripheral cues (Experiment 1) or central, symbolic cues (Experiments 2 and 3) were presented before a target stimulus at intervals ranging from 50 to 250 ms. With peripheral cues, the magnitude of cuing effects was at least as great for older as for younger adults and followed a similar time course. Similar results were obtained with symbolic cues, although cuing effects for older adults varied with cue difficulty. The results suggest that cue encoding may decline with advancing age but that the efficiency of the shift process is preserved.

Adolescent↗

PubMed1979

Information processing in the cerebral hemispheres: selective hemispheric activation and capacity limitations.

Several previous experiments have found that concurrently maintaining verbal information in memory influences visual laterality patterns (e.g., Hellige & Cox, 1976; Kinsbourne, 1975). The present article critically reviews existing experiments and reports five additional experiments designed to identify the mechanisms responsible for such effects. Experiment 1 demonstrates that laterality patterns are not influenced by a concurrent memory task that does not require verbal processing. (The verbal nature of the concurrent task was an important aspect of previous experiments.) Experiments 2 and 3 were designed to determined whether concurrent verbal memory primarily influences very early visuospatial processes or later processes such as those involved in visuospatial memory. In Experiment 2, observers indicated whether two simulteneously presented nonsense forms had the same shape. Observers held 0, 2, 4, or 6 words in memory during each shape judgment trial. Responses were faster when the forms were presented to the left visual field--right hemisphere (LVF-RH) than to the right visual field--left hemisphere (RVF-LH). This effect did not interact with memory set size. In Experiment 3, observers indicated whether either of two simultaneously presented forms was identical to a target form held in memory. Observers held 0, 2, or 6 words in memory on each trial. On same-as-target trials, responses were faster on LVF-RH trials than on RVF-LH trials in the no-word memory condition; this difference was reversed in the two-word and six-word conditions. The combined results of Experiments 2 and 3 suggest that concurrent verbal memory influences stages of processing beyond the initial registration of visuospatial information. Experiments 4 and 5 examined the influence of concurrent verbal memory on verbal laterality tasks. Observers indicated whether two simultaneously presented letters of different cases had the same name. In Experiment 4, different groups of observers held 0, 2, 4, or 6 words in memory on each letter-pair trial. In Experiment 5, memory set size was manipulated within subjects. On the same-pair trials of Experiment 4 and the first session of Experiment 5, responses in the no-memory condition were faster on RVF-LH trials than on LVF-RH trials; this difference was reversed in all of the work memory conditions. This shift is opposite to that found when the laterality task does not require verbal processing and further indicates that concurrent verbal memory influences processing stages beyond those that are common to the form-pair and letter-pair tasks. Neither directness-of-pathway nor attention-gradient laterality models can explain the entire pattern of results from the present experiments. Rather, the results suggest that the left hemisphere functions as a typical limited-capacity information processing system that can be influenced somewhat separately from the right hemisphere system.

Cerebral Cortex↗

PubMed1976

Influence of three short-chain peptides (alpha-MSH, MSH/ACTH 4-10, MIF-I on) dimensional attention.

Male, albino rats were treated with alpha-MSH, MSH/ACTH 4-10, MIF-I or a diluent control solution and then tested on a visual discrimination problem. Immediately after acquistion of the visual task the animals were tested with a spatial extradimensional shift problem. The animals treated with the MSH/ACTH 4-10 and MIF-I acquired the discrimination nonsignificantly faster than animals treated with alpha-MSH or a placebo. A subproblem analysis of the EDS behavior indicated that the peptides significantly improved performance probably by affecting attention.

Adrenocorticotropic Hormone↗

PubMed1992

Structural comparison of apomyoglobin and metaquomyoglobin: pH titration of histidines by NMR spectroscopy.

Proton NMR spectroscopy was applied to myoglobin in the ferric, water-liganded form (metMbH2O) and the apo form (apoMb) to probe the structure and stability of the latter. Proteins from sperm whale and horse skeletal muscles were studied to simplify the spectral assignment task. Nuclear Overhauser effects and the response of chemical shifts to variations of pH were used as indicators of residual native holoprotein structure in the apoprotein. The investigation was focused in the histidine side chains and their environment. In metMbH2O, the resonances of all imidazole rings not interacting with the heme were assigned by applying standard two-dimensional methods. These assignments were found to differ from those reported elsewhere [Carver, J. A., & Bradbury, J. H. (1984) Biochemistry 23, 4890-4905] except for His-12, -113, and -116. Only one histidine (His-36) has a pK(a) higher than 7, two (His-48 and His-113) have a pK(a) lower than 5.5, and two (His-24 and His-82) appear not to titrate between pH 5.5 and pH 10. In the apoproteins, the signals of His-113 and His-116, as well as those of His-24, -36, -48, and -119 previously assigned in the horse globin [Cocco, M. J.. & Lecomte, J. T. J. (1990) Biochemistry 29, 11067-11072], could be followed between pH 5 and pH 10. A comparison to the holoprotein data indicated that heme removal has limited effect on the pK(a) and the surroundings of these residues. Five additional histidines which occur in the two helices and connecting loops forming the heme binding site were identified in the horse apoprotein. Four of these were found to have pK(a) values lower than that expected of an exposed residue. The NOE and titration data were proposed to reflect the fact that several holoprotein structural elements, in particular outside the heme binding site, are maintained in the apoprotein. In the heme binding region of the apoprotein structure, the low pK(a)'s suggest local environments which are resistant to protonation.

Amino Acid Sequence↗

PubMed1992

Persistence and problem-solving skills in young male alcoholics.

This study compares the level of persistence between 31 inpatient alcoholic males and 31 abstinent or light social drinking males matched on age, education, socioeconomic status and estimated premorbid IQ. An unsolvable anagram and diagram were selected as measures of persistence. Results indicated that alcoholics persisted for significantly shorter periods of time on both measures than their matched controls. However, there were no significant group differences on two measures from the Wisconsin Card Sorting Test (set shifting and set maintenance). Persistence measures from the unsolvable tasks were not significantly correlated with the set maintenance score of the Wisconsin Card Sorting Test. Possible explanations are considered for these findings of persistence deficits without problem-solving impairments among young alcoholics.

Adult↗

PubMed1975

The effects of stimulus complexity and sensory modality on reaction time in normal and retarded readers.

Intra- and crossmodal performance of normal and retarded readers was compared in a reaction-time task. Both reading groups showed slower crossmodal than intramodal shifting. This effect occurred equally for both reading groups. Differences between the two groups occurred, however, when a complex visual stimulus was present. The complex stimulus resulted in the retarded readers showing slower reaction times to other stimuli in that setting. This effect occurred for stimuli both within and across modalities. The results suggested that the demands of stimulus complexity within the visual modality rather than the demands of crossmodal shifting were related to reading ability.

Achievement↗

PubMed1992

Immediate colour constancy.

Colour constancy is traditionally interpreted as the stable appearance of the colour of a surface despite changes in the spectral composition of the illumination. When colour constancy has been assessed quantitatively, however, by observers making matches between surfaces illuminated by different sources, its completeness has been found to be poor. An alternative operational approach to colour constancy may be taken which concentrates instead on detecting the underlying chromatic relationship between the parts of a surface under changes in the illuminant. Experimentally the observer's task was to determine whether a change in the appearance of a surface was due to a change in its reflecting properties or to a change in the incident light. Observers viewed computer simulations of a row of three Mondrian patterns of Munsell chips. The centre pattern was a reference pattern illuminated by a simulated, spatially uniform daylight; one of the outer patterns was identical but illuminated by a different daylight; and the other outer pattern was equivalent but not obtainable from the centre pattern by such a change in illuminant. Different patterns and different shifts in daylight were generated in each experimental trial. The task of the observer was to identify which of the outer patterns was the result of an illuminant change. Observers made reliable discriminations of the patterns with displays of durations from several seconds to less than 200 ms, and, for one observer, with displays of 1 ms. By these measures, human observers appear capable of colour constancy that is extremely rapid, and probably preattentive in origin.

Color Perception↗

PubMed1991

Characteristic distribution of alpha 2 wave in electroencephalograms of schizophrenic patients during discriminative tasks: support for the hypofrontality hypothesis of schizophrenia.

In a preliminary study, we noticed that alpha 2 activity in the frontal regions was suppressed less in schizophrenic patients than in other patients during the discriminative tasks. This was confirmed with 37 schizophrenic and 16 nonschizophrenic patients under the treatment of neuroleptics, 15 nonmedicated schizophrenic patients and 32 normal controls. The EEGs in eye-closed resting and during the auditory and visual discriminative tasks were recorded. Alpha 2 power values of the frontal, central, parietal, occipital and temporal regions in every subject group were processed by cluster analysis. During the discriminative tasks, the frontal regions were the most isolated cluster in schizophrenic patients and, in the normal and medicated nonschizophrenic groups, the frontal regions were incorporated in a different cluster. The same result was obtained by different statistical analyses of F-alpha 2 power ratio. The relative abundance of alpha 2 power value shifts from the occipital to the frontal regions during the discriminative tasks in schizophrenic patients. The weakened suppression of alpha 2 waves in the frontal regions by the discriminative tasks in schizophrenic patients supports the hypofrontal hypothesis of schizophrenia.

Adolescent↗

PubMed1992

Neuropsychological aspects of dementia of motor neuron disease: a report of two cases.

We describe the neuropsychological data from two cases of dementia of motor neuron disease. In both cases, a gradually progressive presenile dementia began prior to the development of motor neuron disease involving predominantly bulbar musculature. These data, along with the neuropathologic findings available in one case, suggest that dementia of motor neuron disease differs from that of Alzheimer's disease (AD). Both patients displayed major alterations of personality and comportment. Neuropsychological test results revealed marked attention deficits, particularly on tasks requiring sustained effort and on those requiring ability to shift from one line of thinking to another. Confrontation naming, verbal fluency, insight, and judgment also showed extensive impairment. By contrast, verbal and nonverbal memory remained intact after several years of illness. This pattern is quite different from that seen in AD, where memory deficits are salient.

Aged↗

PubMed1992

How fast should the night shift rotate? A rejoinder.

The argument for greater use of permanent night shift does not match the three times greater use of rotating three-shift systems in Britain. Studies of industrial production show very slight differences between output on different shifts, unlike laboratory studies, suggesting that it is almost impossible to reproduce the practice, motivation, and real consequences of work in laboratory settings. People who prefer permanent night shift often prefer to avoid management, and few managements welcome this; or have important tasks to perform at home in the day-time. Some studies of adaptation have defined inversion of temperature curves poorly, and most night-workers never completely adapt. Social flexibility, which has been the main attraction of rapidly rotating shifts, can be reproduced on permanent night shifts, but then loses the possibility of adaptation.

Circadian Rhythm↗

PubMed1992

Visuospatial attention in dementia of the Alzheimer type.

Cue-directed shifts of spatial attention were examined for a letter-discrimination task in 15 patients with mild to moderate dementia of the Alzheimer type (DAT) and 15 healthy, age-matched controls. Spatial cues were valid, invalid or neutral in indicating probable target location and were presented either centrally at fixation or peripherally 6.7 degrees to the left or right of fixation. Stimulus-onset asynchrony (SOA) between cue and target was varied between 200 ms and 2000 ms. Reaction time (RT) benefits conferred by valid cues did not differ between the DAT group and the controls. However, RT costs incurred by invalid cues were significantly greater in the DAT group than in the control group. Group differences in RT costs plus benefits occurred at short SOAs (less than 500 ms) for peripheral cues and at long SOAs (greater than 500 ms) for central cues. Reaction time costs plus benefits were correlated with right-left asymmetry in resting levels of cerebral glucose metabolism in the superior parietal lobe for DAT patients but not for controls. The results indicate that focusing of attention to spatial location is intact in early DAT, whereas the disengagement of visuospatial attention is impaired. Automatic attention shifts elicited by peripheral cues reveal abnormalities earlier than attention shifts initiated 'effortfully' by central cues. Intact focusing and impaired disengagement of visuospatial attention may be linked to dysfunction in early DAT of cortico-cortical networks linking the posterior parietal and frontal lobes.

Aged↗