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Results for “Task Shifting”

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PubMed1993

Effects of a visual task with cognitive demand on dynamic and steady-state accommodation.

Dynamic accommodative response before and after, and steady-state accommodation during, a visual task were measured using an infrared optometer to investigate the effects of psychological stress on accommodative facility. Increase in the post-task dynamic accommodation response time (for a near-to-far condition) was greater for a group of subjects given a mental task at a higher presentation speed. In addition the steady-state accommodation showed an inward shift under a closed-loop condition which was enhanced when computation time was decreased. However, an inward shift was not evident when the performance level of subjects increased following training. The relationship between psychological stress, cognitive demand and accommodative function is discussed.

Accommodation, Ocular↗

PubMed1999

Scopolamine slows the orienting of attention in primates to cued visual targets.

The cholinergic agonist nicotine facilitates visuospatial attention shifting, but the role of muscarinic cholinergic drugs in this behavior is unclear. In order to establish the generality of cholinergic action in attention shifting, we administered the muscarinic antagonist scopolamine to two rhesus monkeys trained to perform a cued target detection (Posner) task. In this task, monkeys signaled the detection of a peripheral visual target by releasing a switch and their reaction times were measured. The location of the target's appearance was preceded by a cue that was either valid (target and cue in the same spatial location), invalid (target and cue to opposite hemifields), spatially uninformative (cues in both hemifields, target to one hemifield), or omitted altogether. Scopolamine produced a dose-dependent increase in all reaction times and a decrease in accuracy. The slowing was most prominent for valid cues in either visual field. However, slowing did not occur in trials whose cues lacked spatial information, or in tasks in which attention was directed to events at the fixation point, whether or not peripheral distractors were present. These results provide additional support for the hypothesis that acetylcholine plays a key role in reflexive attention shifting to peripheral visual targets.

Analysis of Variance↗

PubMed2005

[Visual search in Alzheimer disease--an functional magnetic resonance imaging study].

OBJECTIVE: To investigate the functional activation patterns during two types of visual search tasks in Alzheimer's disease (AD) with functional MRI, and probe the neuro-anatomic basis of visual attention. METHODS: 13 patients with AD and 13 sex and age-matched healthy subjects participated in the experiment designed with two visual search tasks. The first was a "pop-out" single feature task, detecting a vertical target among horizontal distractors, and the second was a conjunction task where the target was defined by conjunction of feature (color and orientation) and the performance depended on some shifting of attention. The fMRI data were collected by Siemens 1.5 T Sonata magnetic resonance imaging (MRI) system and analyzed by Statistical Parametric Mapping software (SPM 99) to generate the activation map. RESULTS: AD patients had a particular impairment in the conjunction task but not in the single-feature task. Although both groups revealed overlapping networks engaged in the conjunction tasks including the superior parietal lobule (SPL), frontal and occipitotemporal cortical regions (OTC), primary visual cortex and some subcortical structures, the most pronounced difference between them was found in bilateral SPL (more activities in the controls) and right OTC (more activities in the patients). The difference between the 2 groups was small in the pop-out condition. CONCLUSION: AD particularly affects those mechanisms controlling spatial shifts of attention. Some additional remote activation (ventral visual stream and temporal lobe) can be interpreted as dynamic reallocating of brain functional resource.

Aged↗

PubMed1981

Changes in cognitive task performance across the menstrual cycle.

Menstrual-cycle-related changes in estrogen were expected to differentially affect various cognitive tests. Specifically, the estrogen peak occurring at midcycle in ovulatory women was expected to facilitate performance of highly practiced "automatized" tasks and to impair performance of "perceptual-restructuring" tasks, compared with performance of these tasks in the postovulatory phase of the cycle when progesterone is thought to counteract the action of estrogen. Perceptual-restructuring tasks are defined as tasks in which the initial percepts to obvious stimulus attributes are wrong and must be set aside in favor of percepts to less obvious stimulus attributes. Eight-seven regularly menstruating undergraduate women were studied. Odd-numbered subjects were tested first on or about Day 10 of their cycle and then again on Day 20; even-numbered subjects, in the reverse sequence. Daily basal body temperature records were obtained. These temperature records suggested that 21, or 24%, of the subjects did not ovulate in the cycle(s) studied. No main effect of Day 10 versus Day 20 occurred for any task in the 66 women who did appear to ovulate. However, the magnitude of predicted shifts in performance was significantly correlated with proximity of the "Day 10" testing day to the thermal nadir of the basal body temperature record, the presumed preovulatory estrogen peak; and to the "Day 20" proximity to the basal body temperature thermal peak, the presumed progesterone peak. Subjects tested 3 or fewer days before the thermal nadir and on or after the thermal peak had the predicted significant changes on three of the four administered tasks. No other temporally defined group produced significant changes. The results of the study support the experimental hypotheses and also indicate that precise timing is essential to demonstrate the phenomena.

Adult↗

PubMed2006

Identification of simulated microcalcifications in white noise and mammographic backgrounds.

This work investigates human performance in discriminating between differently shaped simulated microcalcifications embedded in white noise or mammographic backgrounds. Human performance was determined through two alternative forced-choice (2-AFC) experiments. The signals used were computer-generated simple shapes that were designed such that they had equal signal energy. This assured equal detectability. For experiments involving mammographic backgrounds, signals were blurred to account for the imaging system modulation transfer function (MTF). White noise backgrounds were computer generated; anatomic background patches were extracted from normal mammograms. We compared human performance levels as a function of signal energy in the expected difference template. In the discrimination task, the expected difference template is the difference between the two signals shown. In white noise backgrounds, human performance in the discrimination task was degraded compared to the detection task. In mammographic backgrounds, human performance in the discrimination task exceeded that of the detection task. This indicates that human observers do not follow the optimum decision strategy of correlating the expected signal template with the image. Human observer performance was qualitatively reproduced by non-prewhitening with eye filter (NPWE) model observer calculations, in which spatial uncertainty was explicitly included by shifting the locations of the expected difference templates. The results indicate that human strategy in the discrimination task may be to match individual signal templates with the image individually, rather than to perform template matching between the expected difference template and the image.

Artifacts↗

PubMed1991

Lingual vibrotactile threshold shift during magnitude-estimation scaling: effects on magnitude-estimation responses and scaling behavior across age.

The purpose of this study was to investigate the effects of age on tactile threshold shifts occurring during magnitude-estimation scaling of vibratory stimuli presented to the dorsal surface of the tongue. Relationships of the lingual vibrotactile threshold shifts to suprathreshold stimulus intensity, magnitude-estimation responses, and over-all scaling behavior were explored. Three groups differing in mean age participated in this study (Group 1 8.05 yr., Group 2 19.46 yr., and Group 3 56.2 yr.). Each subject performed two magnitude-estimation tasks. In one task, threshold of sensitivity was measured after every suprathreshold numerical response to the subject. If a threshold shift was recorded, threshold was allowed to return to the pretest baseline level continuing to the next suprathreshold stimulus presentation. The results showed that threshold shift during magnitude-estimation scaling took place for all three age groups and that the shift was related to the intensity of the suprathreshold vibratory stimulus being applied to the tongue. They also showed that Group 2 (young adults) performed magnitude-estimation scaling differently when threshold shift was controlled than when it was not. The other two groups of subjects were not similarly affected.

Adolescent↗

PubMed1999

A cognitive activation study of memory for spatial relationships.

Twelve neurologically normal right-handed subjects were asked to remember the locations of eight representational drawings, presented one at a time, together with two landmarks (white squares), on a computer screen. Subjects were then scanned using positron emission tomography (PET) while performing forced-choice recognition of object location in four conditions, using either the original landmarks or two of the other objects as cues. In two conditions, the absolute location of the objects was unchanged from the time of encoding (fixed-array conditions), whereas in the other two, the location of the objects was shifted, although the spatial relationship among the objects and landmarks was maintained (shifted-array conditions). Subjects were also scanned in a control condition that made the same perceptual and motor demands as the recognition tasks but that had no mnemonic component. Compared to the control condition, all of the recognition tasks activated both the dorsal and ventral visual pathways bilaterally, but with notable asymmetries. In particular, activation in the right, but not left, inferior temporal gyrus (area 37) was observed when both shifted-array conditions were compared to their respective cue-matched fixed-array conditions. The recognition conditions with landmark cues were associated with focal increases in regional cerebral blood flow (rCBF) in the region of the right parahippocampal gyrus. The results support previous reports of involvement of the right mesial temporal region in object-location memory tasks, and suggest that right inferotemporal cortex is involved in extracting the invariant relational features of a visual scene.

Adult↗

PubMed1995

Electrophysiologic correlates of age effects on visuospatial attention shift.

The effects of age on the neural processes underlying shifts in visuospatial attention were studied by non-invasive recording of brain electrical activity. Event-related evoked potentials (ERPs) were recorded in young (age 28-36 years old) and elderly (59-74 years old) subjects during a target detection task. Targets were preceded by central or peripheral informative cues, which are hypothesized to provoke voluntary and reflexive shifts of spatial attention, respectively. There were no age-related differences in the effects of cue validity on reaction times. Elderly subjects had longer reaction times to both the valid and invalid targets. The ERP recordings demonstrated that attention shift-related negativities (ARNs) were generated over the hemisphere contralateral to the central cue direction with the same amplitude in young and elderly subjects. However, the onset latency was delayed for the elderly at anterior scalp sites. Peripheral cues enhanced the N1 component (140-200 ms post-cue) over the contralateral hemisphere comparably in the two age groups. The ARNs following N1 enhancement demonstrated delayed onset and restricted scalp distributions in the elderly group compared with the young group. These results suggest that resistance of cue validity effects to aging is consistent with existence of the N1 enhancement and ARNs, even in elderly subjects. Different age effects on ERPs generated by central and peripheral cues support the notion that voluntary and reflexive mechanisms of attention shift involve distinct neural systems with different vulnerability to aging.

Adult↗

PubMed2006

Impaired cognition and decision-making in bipolar depression but no 'affective bias' evident.

BACKGROUND: Depression is usually the predominant affective state in bipolar disorder. There are few studies, with discrepant views, examining the extent of cognitive impairment in patients with bipolar depression. To our knowledge, there are no previous studies examining decision-making ability or whether there is an affective attentional bias in bipolar depression. METHOD: We ascertained 24 depressed bipolar I patients from acute psychiatric hospital wards and out-patient clinics and 26 age- and IQ-matched healthy controls. Using computerized tests we evaluated their performance on 'neutral' (non-emotional) cognitive tasks (i.e. memory, attention and executive function) and on novel tasks of emotional cognition (i.e. the decision-making task and the affective go/no-go task). RESULTS: Accuracy measures were significantly impaired on tests of visual and spatial recognition and attentional set-shifting in bipolar depression compared with age- and IQ-matched controls. The quality of decision-making was also significantly impaired in the patients. A mood-congruent attentional bias for 'sad' targets was not evident on the affective go/no-go task. CONCLUSIONS: We found widespread evidence of significant cognitive impairment and impaired quality of decision-making in symptomatically severe depressed bipolar patients. This cognitive impairment may contribute to difficulties with daily living, decision-making and the ability to engage and comply with psychological and drug treatments.

Adolescent↗

PubMed2005

Posterior parietal cortex and developmental dyslexia.

Dyslexia is defined as a specific reading disorder despite normal intelligence and conventional teaching. One of the most influential theories attempting to explain problems suffered by dyslexics assumes that dyslexia is caused by deficits of the magnocellular system. This system, generally responsible for processing fast sensory information, projects mostly to the parietal cortex. Consistent with this theory, dyslexics should have problems with tasks which specifically involve parietal cortex. In the article, we review data and show that, indeed, dyslexics have problems with fast attention shifts, show some symptoms of mild unilateral neglect syndrome and have abnormal saccadic and pursuit eye movements. Little is known about visuo-motor coordination and mental rotation, the tasks in which the parietal cortex is thought to play important roles.

Dyslexia↗

PubMed2005

Spatial attention triggered by eye gaze enhances and speeds up visual processing in upper and lower visual fields beyond early striate visual processing.

OBJECTIVE: The detection of a lateralized visual target is faster when preceded by a face gazing to the location of this stimulus. Here we aimed to clarify the time-course of the visual processing modulated by these reflexive shifts of attention. METHODS: ERPs were measured on 16 subjects performing a speeded location task on a circular checkerboard. The checkerboard target appeared either on the left or right of the upper or lower visual field, and was preceded by a central face orienting its gaze obliquely to one of the four possible corner locations for the target to appear. RESULTS: Congruently cued targets were located faster than incongruently cued targets and were associated with larger and earlier occipital P1 (approximately 110 ms) and occipito-parieto-temporal N1 (approximately 150 ms) components. However, no such attentional modulations were found on the earlier C1 visual component, best observed with a negative polarity for upper visual field stimulations, and thought to originate largely from primary visual cortex. CONCLUSIONS AND SIGNIFICANCE: These results show that reflexive shifts of attention following oblique eye gaze to upper and lower visual fields increase and speed up the processing of visual information beyond the feedforward flow of information in primary visual cortex.

Adult↗

PubMed1983

Effects of lateral suprasylvian visual cortex lesions on visual localization, discrimination, and attention in cats.

Experiments were carried out to begin to define the behavioral functions of the lateral suprasylvian (LS) visual area of the cat's cortex. Behavioral tasks were chosen for analysis on the basis of previous suggestions in the literature concerning possible functions of LS cortex and its afferent pathways. These tasks included the ability of cats to orient the head and eyes to a stimulus presented in particular locations in the visual field, the ability to learn successive reversals of a two-choice visual pattern discrimination, and the ability to maintain or shift attention between relevant or irrelevant visual form and brightness cues. Eight cats were trained on each of these tasks. Four of the cats then received bilateral lesions of LS cortex, including the AMLS and PMLS regions, and the remaining 4 cats were used to assess normal retention. The LS cortex lesions had no significant effect upon performance of any of the behaviors tested. Thus, this region of cortex appears to play no essential role in simple brightness, form, and pattern discrimination performance, visual reversal learning, maintaining and shifting visual attention, or orienting the head and eyes to stimuli in the visual field. These results are discussed in relation to previous lesion studies involving large regions of the cat's extrastriate cortex and studies in other species. Possible functions of LS cortex, based upon recent electrophysiological studies, are suggested.

Animals↗

PubMed2006

Describing nurses' work: combining quantitative and qualitative analysis.

OBJECTIVE: To better understand nursing activities and working conditions. BACKGROUND: Nursing practice involves astute clinical decision making and the competent delivery of nursing care procedures. To complete nursing procedures, nurses must simultaneously organize and reorganize priorities and manage changing clinical information for multiple patients. Few researchers have examined the specific nature of nurses' activities and the effect of the environment on their work. METHODS: Quantitative and qualitative methods were used to collect data on 7 nurses engaged in nursing activities. Examples of methods include link analysis, subject matter expert, task analysis, cognitive pathway, and "stacking." Data collection focused on how nurses managed priorities, changing clinical information, and interruptions. RESULTS: The "cognitive pathway" graphically depicts the nature of nurses' work. Specifically, it reveals the shifting of the nurse's attention from patient to patient and the occurrence of interruptions. "Stacking" shows the number of tasks a nurse must balance at any one time. On average, nurses had 10 or more activities waiting to be performed and experienced 3.4 interruptions/hr. CONCLUSION: These methods provide unique insight into the dynamic nature of patient care and nursing work. APPLICATION: Extension of the methods demonstrated here may be useful in guiding efforts to change the work of nursing to better provide quality care and less stressful work environments.

Evaluation Studies as Topic↗

PubMed2004

Learning to read without a left occipital lobe: right-hemispheric shift of visual word form area.

Using anatomical and functional magnetic resonance imaging, we studied the pattern of brain lateralization during spoken and written language tasks, in an 11-year-old girl who underwent a left occipitotemporal resection for a Sturge-Weber angioma at the age of 4 years, that is, after the development of speech but before the acquisition of reading. We observed a selective and successful shift to the right hemisphere of the visual component of reading, particularly the Visual Word Form Area, whereas the verbal components remained strongly left-lateralized. This emphasizes the potential utility of a precise functional and developmental cartography of language for the surgical treatment of focal brain lesions in children.

Child↗

PubMed1991

Further evidence for a time-independent shift of the focus of attention.

The separation between stimuli was manipulated in a same-different matching task. In Experiment 1, stimuli were upright Ts and/or Ls, whereas in Experiment 2, they were rotated Ts and/or Ls. In both experiments, mean reaction time (RT) for the same-different judgment did not increase as a function of interletter separation, suggesting either that the time needed to relocate attention was independent of distance, or that the stimuli were processed in parallel. These alternatives were tested in a third experiment, with a diagnostic for parallel processing proposed by Egeth and Dagenbach (1991). The diagnostic indicated that the rotated Ts and Ls in Experiment 2 were processed serially. If serial processing implies the utilization of attention, then the results of Experiment 2 suggest that relocation of attention is time-invariant with respect to distance.

Adult↗

PubMed1998

Depolarizing the perceptual magnet effect.

In recent years there has been a great deal of interest in demonstrations of the so-called "Perceptual-Magnet Effect" (PME). In these studies, AX-discrimination tasks purportedly reveal that discriminability of speech sounds from a single category varies with judged phonetic "goodness" of the sounds. However, one possible confound is that category membership is determined by identification of sounds in isolation, whereas, discrimination tasks include pairs of stimuli. In the first experiment of the current study, identification and goodness judgments were obtained for vowels (/i/-/e/) presented in pairs. A substantial shift in phonetic identity was evidenced with changes in the context vowel. In a second experiment, listeners participated in an AX-discrimination task with the vowel pairs from the first experiment. Using the contextual identification functions from the first experiment, predictions of discriminability were calculated using the classic tenets of Categorical Perception. Obtained discriminability functions were well accounted for by predictions from identification. There was no additional unexplained variance that required the proposal of "perceptual magnets." These results suggest that PME may be nothing more than further demonstration that general discriminability is greater for cross-category stimulus pairs than for within-category pairs.

Humans↗

PubMed1999

Age, gender, and education may have little influence on error patterns in the assessment of set-shifting and rule induction among normal elderly.

Error patterns have been found to be sensitive to cognitive status, but the relationship between aging and error patterns remains unclear, and may differ as a function of gender, education, and whether a task is verbal or nonverbal. The present study examined the error patterns of normal elderly individuals on a verbal measure of set-shifting and rule induction to determine whether demographic variables, that is, age, gender, and education, influenced test performance. The sample of 109 individuals, 38 males and 71 females, ranging in age from 54 to 89 years with 6 to 19 years of education, was assessed on the Classification subtest of the Test of Verbal Conceptualization and Fluency, a verbal measure of set-shifting and rule induction. Subjects' protocols were scored for perseverative, nonperseverative, and random errors, tabulated, and analyzed. Multivariate analysis of covariance with education as the covariate as well as other statistical tests revealed nonsignificant relationships between error scores and age, gender, and education. Years of education, however, showed a significant correlation with a reduction in random responses. Results are interpreted based on Horn's (1978) fluid-crystallized explanations of changes in intelligence with advancing age.

Journal Article↗

PubMed2003

Irrelevant auditory attention shifts prime corresponding responses.

In this paper we investigate whether an attention shift towards an auditory signal, while performing a two-choice serial reaction time task, primes responses in the direction of the auditory signal. In Experiment 1, subjects had to react to the pitch of the signal, which was randomly presented to the left or right ear. A short (50-ms) and a long (1000-ms) response-stimulus interval (RSI) was used. In Experiment 2 with an RSI of 2000 ms, subjects had to respond to the color of a centrally presented visual stimulus, while a sound was presented to one of the ears. In the short RSI condition of Experiment 1, there was a Simon effect for location alternations only. In the long RSI condition, there was a Simon effect for location repetitions and alternations. Experiment 2 showed a Simon effect in relation to the accessory sound. The results of this study suggest that an attention shift is a sufficient and necessary condition in order to observe a Simon effect.

Adolescent↗