Investigating the Time-Course of Task-Dependent Perceptual Grouping

Perception ◽  
1997 ◽  
Vol 26 (1_suppl) ◽  
pp. 148-148
Author(s):  
E D Freeman
Keyword(s):  
Perceptual Grouping ◽  
Time Course ◽  
Shape Matching ◽  
Early Stage ◽  
Backward Masking ◽  
Task Context ◽  
Visual Processes ◽  
Task Experience ◽  
Selection Of ◽  
And Task

At what stage do factors such as task experience and expectation interact with the perception of whole objects? Recent work (Freeman, 1995 Perception24 Supplement, 134; 1996 Perception25 Supplement, 51) suggests that perceptual grouping of ambiguous 1-Whole/2-Wholes stimuli is dependent upon learning and task predictability, as inferred from changes in performance in a Whole - Whole/Whole - Part shape matching paradigm. Thus, subjects seemed able to offset the effect of a stimulus parameter known to influence perceived grouping, in order to see the grouping they had been trained to see or were expecting to see. In the present research the timing of these interactive processes was investigated, with the use of backward masking to take a snapshot of visual processes at different stages in their development. Stimulus and task-context factors were found to interact even at the shortest masking interval (50 ms), suggesting that top - down knowledge constrains perceptual grouping processes from an early stage onwards. A simple model of the development of 1-Whole and 2-Whole percepts implies two further conclusions. First, task and stimulus factors both seem to work by modifying the rate of development of the alternative percepts. Second, and counter-intuitively, it appears that, given the appropriate task-context and stimuli, it is possible to group the stimulus in several different ways at once. These results shed light on issues concerning the nature of perceptual grouping, and the process by which our experience of objects is brought to bear on our selection of functional perceptual groups.

scholarly journals COVID-19 DYNAMICS: A HETEROGENEOUS MODEL

2020 ◽  
Author(s):  
Andrey Gerasimov ◽  
Georgy Lebedev ◽  
Mikhail Lebedev ◽  
Irina Semenycheva
Keyword(s):  
Time Course ◽  
Early Stage ◽  
Risk Control ◽  
Basic Reproductive Number ◽  
Reproductive Number ◽  
High Likelihood ◽  
Rigorous Analysis ◽  
Homogeneous Case ◽  
Heterogeneous Model ◽  
Selection Of

AbstractThe ongoing Coronavirus disease 2019 (COVID-19) epidemic is different from the previous epidemic of severe acute respiratory syndrome (SARS), which demands a rigorous analysis for the selection of anti-epidemic measures and their lifting when the epidemic subsides. Here we estimate the basic reproductive number for COVID-19 and propose a dynamical model for the time course of infection number. With this model, we assessed the effects of different measures for infection risk control. The model is different from the previous ones as it models the population as heterogeneous, with subpopulations having different infection risks. Our analyses showed that after this heterogeneity is incorporated in the model, several characteristics of the epidemic are estimated more accurately: the total number of cases and peak number of cases are lower compared to the homogeneous case, the early-stage growth rate in the number of infection cases is little affected, and the decrease in the number of infections slows down during the epidemic late stage. The comparison of our model results with the available data for COVID-19 indicates that the anti-epidemic measures undertaken in China and the rest of the world managed to decrease the basic reproductive number but did not assure an accumulation of sufficient collective immunity. Thus, the epidemic has a high likelihood to restart, which necessitates a careful approach to lifting the quarantine measures.

scholarly journals Cognitive dysfunction in amyotrophic lateral sclerosis: can we predict it?

2021 ◽  
Author(s):  
Fabiola De Marchi ◽  
◽  
Claudia Carrarini ◽  
Antonio De Martino ◽  
Luca Diamanti ◽  
...  
Keyword(s):  
Amyotrophic Lateral Sclerosis ◽  
Time Course ◽  
Neurodegenerative Disorder ◽  
Early Stage ◽  
Multisystem Disorder ◽  
Behavioral Impairment ◽  
Behavioral Impairments ◽  
Als Patients ◽  
Disease Stages ◽  
Lateral Sclerosis

Abstract Background and aim Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disorder characterized by the degeneration of both upper and lower motoneurons in the brain and spinal cord leading to motor and extra-motor symptoms. Although traditionally considered a pure motor disease, recent evidences suggest that ALS is a multisystem disorder. Neuropsychological alterations, in fact, are observed in more than 50% of patients: while executive dysfunctions have been firstly identified, alterations in verbal fluency, behavior, and pragmatic and social cognition have also been described. Detecting and monitoring ALS cognitive and behavioral impairment even at early disease stages is likely to have staging and prognostic implications, and it may impact the enrollment in future clinical trials. During the last 10 years, humoral, radiological, neurophysiological, and genetic biomarkers have been reported in ALS, and some of them seem to potentially correlate to cognitive and behavioral impairment of patients. In this review, we sought to give an up-to-date state of the art of neuropsychological alterations in ALS: we will describe tests used to detect cognitive and behavioral impairment, and we will focus on promising non-invasive biomarkers to detect pre-clinical cognitive decline. Conclusions To date, the research on humoral, radiological, neurophysiological, and genetic correlates of neuropsychological alterations is at the early stage, and no conclusive longitudinal data have been published. Further and longitudinal studies on easily accessible and quantifiable biomarkers are needed to clarify the time course and the evolution of cognitive and behavioral impairments of ALS patients.

Current Task Activation Predicts General Effects of Advance Preparation in Task Switching

2006 ◽  
Vol 53 (4) ◽  
pp. 260-267 ◽  
Author(s):  
Edita Poljac ◽  
Ab de Haan ◽  
Gerard P. van Galen
Keyword(s):  
Task Performance ◽  
Task Switching ◽  
Shape Matching ◽  
Response Times ◽  
Error Rates ◽  
Matching Task ◽  
Task Switch ◽  
Current Task ◽  
Within Subjects ◽  
And Task

Two experiments investigated the way that beforehand preparation influences general task execution in reaction-time matching tasks. Response times (RTs) and error rates were measured for switching and nonswitching conditions in a color- and shape-matching task. The task blocks could repeat (task repetition) or alternate (task switch), and the preparation interval (PI) was manipulated within-subjects (Experiment 1) and between-subjects (Experiment 2). The study illustrated a comparable general task performance after a long PI for both experiments, within and between PI manipulations. After a short PI, however, the general task performance increased significantly for the between-subjects manipulation of the PI. Furthermore, both experiments demonstrated an analogous preparation effect for both task switching and task repetitions. Next, a consistent switch cost throughout the whole run of trials and a within-run slowing effect were observed in both experiments. Altogether, the present study implies that the effects of the advance preparation go beyond the first trials and confirms different points of the activation approach ( Altmann, 2002) to task switching.

Dynamic coupling among neocortical neurons during evoked and spontaneous spike-wave seizure activity

1994 ◽  
Vol 72 (5) ◽  
pp. 2051-2069 ◽  
Author(s):  
M. Steriade ◽  
F. Amzica
Keyword(s):  
Cortical Neurons ◽  
Time Course ◽  
Early Stage ◽  
Field Potential ◽  
Time Lags ◽  
Temporal Relations ◽  
Intracellular Recordings ◽  
Field Potentials ◽  
Thalamic Nuclei ◽  
Spike Wave

1. We investigated the development from patterns of electroencephalogram (EEG) synchronization to paroxysms consisting of spike-wave (SW) complexes at 2–4 Hz or to seizures at higher frequencies (7–15 Hz). We used multisite, simultaneous EEG, extracellular, and intracellular recordings from various neocortical areas and thalamic nuclei of anesthetized cats. 2. The seizures were observed in 25% of experimental animals, all maintained under ketamine and xylazine anesthesia, and were either induced by thalamocortical volleys and photic stimulation or occurred spontaneously. Out of unit and field potential recordings within 370 cortical and 65 thalamic sites, paroxysmal events occurred in 70 cortical and 8 thalamic sites (approximately 18% and 12%, respectively), within which a total of 181 neurons (143 extracellular and 38 intracellular) were simultaneously recorded in various combinations of cell groups. 3. Stimulus-elicited and spontaneous SW seizures at 2–4 Hz lasted for 15–35 s and consisted of barrages of action potentials related to the spiky depth-negative (surface-positive) field potentials, followed by neuronal silence during the depth-positive wave component of SW complexes. The duration of inhibitory periods progressively increased during the seizure, at the expense of the phasic excitatory phases. 4. Intracellular recordings showed that, during such paroxysms, cortical neurons displayed a tonic depolarization (approximately 10–20 mV), sculptured by rhythmic hyperpolarizations. 5. In all cases, measures of synchrony demonstrated time lags between discharges of simultaneously recorded cortical neurons, from as short as 3–10 ms up to 50 ms or even longer intervals. Synchrony was assessed by cross-correlograms, by a method termed first-spike-analysis designed to detect dynamic temporal relations between neurons and relying on the detection of the first action potential in a spike train, and by a method termed sequential-field-correlation that analyzed the time course of field potentials simultaneously recorded from different cortical areas. 6. The degree of synchrony progressively increased from preseizure sleep patterns to the early stage of the SW seizure and, further, to its late stage. In some cases the time relation between neurons during the early stages of seizures was inversed during late stages. 7. These data show that, although the common definition of SW seizures, regarded as suddenly generalized and bilaterally synchronous activities, may be valid at the macroscopic EEG level, cortical neurons display time lags between their rhythmic spike trains, progressively increased synchrony, and changes in the temporal relations between their discharges during the paroxysms.(ABSTRACT TRUNCATED AT 400 WORDS)

Performance Evaluation Tests for Environmental Research (Peter): Evaluation of 114 Measures

1986 ◽  
Vol 63 (2) ◽  
pp. 683-708 ◽  
Author(s):  
Alvah C. Bittner ◽  
Robert C. Carter ◽  
Robert S. Kennedy ◽  
Mary M. Harbeson ◽  
Michele Krause
Keyword(s):  
Performance Evaluation ◽  
Repeated Measures ◽  
Time Course ◽  
Environmental Studies ◽  
Acceptable Level ◽  
Environmental Research ◽  
Human Capabilities ◽  
Task Definition ◽  
And Task

The goal of the Performance Evaluation Tests for Environmental Research (PETER) Program was to identify a set of measures of human capabilities for use in the study of environmental and other time-course effects. 114 measures studied in the PETER Program were evaluated and categorized into four groups based upon task stability and task definition. The Recommended category contained 30 measures that clearly obtained total stabilization and had an acceptable level of reliability efficiency. The Acceptable-But-Redundant category contained 15 measures. The 37 measures in the Marginal category, which included an inordinate number of slope and other derived measures, usually had desirable features which were outweighed by faults. The 32 measures in the Unacceptable category had either differential instability or weak reliability efficiency. It is our opinion that the 30 measures in the Recommended category should be given first consideration for environmental research applications. Further, it is recommended that information pertaining to preexperimental practice requirements and stabilized reliabilities should be utilized in repeated-measures environmental studies.

Recovery of subjective visual horizontal after unilateral vestibular deafferentation by intratympanic instillation of gentamicin

2006 ◽  
Vol 16 (1-2) ◽  
pp. 69-73 ◽  
Author(s):  
Yoshinari Takai ◽  
Toshihisa Murofushi ◽  
Munetaka Ushio ◽  
Shinichi Iwasaki
Keyword(s):  
Healthy Subjects ◽  
Time Course ◽  
Early Stage ◽  
Ccd Camera ◽  
The Other ◽  
Spontaneous Nystagmus ◽  
Vestibular Evoked Myogenic Potentials ◽  
Normal Range ◽  
Intratympanic Gentamicin ◽  
Unilateral Vestibular Deafferentation

The time course of the recovery of subjective visual horizontal (SVH) after unilateral vestibular deafferentation by intratympanic instillation of gentamicin was studied. Six patients who underwent intratympanic gentamicin instillation therapy for Meniere's disease (1 man and 5 women, 32 to 69 years of age) were enrolled in this study. For comparison, SVH in 23 healthy subjects (12 men and 11 woman, 23 to 48 years of age) was also measured. The mean ± SD of SVH in healthy subjects was 0.0 ± 1.1 deg. All of the 6 patients showed significantly deviated SVH toward the injected side-down at the early stage after the therapy. Although one patient showed recovery of SVH to the normal range 25 days after the injection, the other patients required more time for recovery. Three patients did not show recovery to the normal range after 1 year. On the other hand, spontaneous nystagmus observed using an infrared CCD camera in total dark disappeared after 35 days (median). Patients who had normal vestibular evoked myogenic potentials before the therapy showed a tendency of delay of recovery of SVH. The reasons why the recovery of SVH took longer than the disappearance of spontaneous nystagmus are discussed in this report.

In progressive nephropathies, overload of tubular cells with filtered proteins translates glomerular permeability dysfunction into cellular signals of interstitial inflammation.

1998 ◽  
Vol 9 (7) ◽  
pp. 1213-1224 ◽  
Author(s):  
M Abbate ◽  
C Zoja ◽  
D Corna ◽  
M Capitanio ◽  
T Bertani ◽  
...  
Keyword(s):  
Time Course ◽  
Early Stage ◽  
Protein Accumulation ◽  
Glomerular Injury ◽  
Cellular Mechanisms ◽  
Proinflammatory Response ◽  
Glomerular Permeability ◽  
Tubular Cells ◽  
Interstitial Inflammation ◽  
Tubulointerstitial Lesions

Progression to end-stage renal failure is the final common pathway of many forms of glomerular disease, independent of the type of initial insult. Progressive glomerulopathies have in common persistently high levels of urinary protein excretion and tubulointerstitial lesions at biopsy. Among the cellular mechanisms that may determine progression regardless of etiology, the traffic of excess proteins filtered from glomerulus in renal tubule may have functional importance by initiating interstitial inflammation in the early phase of parenchymal injury. This study analyzes the time course and sites of protein accumulation and interstitial cellular infiltration in two different models of proteinuric nephropathies. In remnant kidneys after 5/6 renal mass ablation, albumin and IgG accumulation by proximal tubular cells was visualized in the early stage, preceding interstitial infiltration of MHC-II-positive cells and macrophages. By double-staining, infiltrates developed at or near tubules containing intracellular IgG or luminal casts. This relationship persisted thereafter despite more irregular distribution of infiltrate. Similar patterns were found in an immune model (passive Heymann nephritis), indicating that the interstitial inflammatory reaction develops at the sites of protein overload, regardless of the type of glomerular injury. Osteopontin was detectable in cells of proximal tubules congested with protein in both models at sites of interstitial infiltration, and by virtue of its chemoattractive action this is likely mediator of a proximal tubule-dependent inflammatory pathway in response to protein load. Protein overload of tubules is a key candidate process translating glomerular protein leakage into cellular signals of interstitial inflammation. Mechanisms underlying the proinflammatory response of tubular cells to protein challenge in diseased kidney should be explored, as well as ways of limiting protein reabsorption/deposition to prevent consequent inflammation and progressive disease.

scholarly journals The roles of mask luminance and perceptual grouping in visual backward masking

2009 ◽  
Vol 9 (11) ◽  
pp. 22-22 ◽  
Author(s):  
I. Dombrowe ◽  
F. Hermens ◽  
G. Francis ◽  
M. H. Herzog
Keyword(s):  
Perceptual Grouping ◽  
Backward Masking ◽  
Visual Backward Masking

Assessing Product Lifecycle Sustainability Using Uncertain Design Information at Conceptual Stage

2008 ◽  
Author(s):  
Q. Z. Yang ◽  
B. Song
Keyword(s):  
Conceptual Design ◽  
Product Information ◽  
Sustainability Assessment ◽  
Early Stage ◽  
Evaluation Model ◽  
Evaluation Criteria ◽  
Design Decision ◽  
Fuzzy Evaluation ◽  
Product Lifecycle ◽  
Selection Of

This paper presents a hierarchical fuzzy evaluation approach to product lifecycle sustainability assessment at conceptual design stages. The purpose is to advocate the emerging use of lifecycle engineering methods in support of evaluation and selection of design alternatives for sustainable product development. A fuzzy evaluation model is developed with a hierarchical criteria structure to represent different sustainability considerations in the technical, economic and environmental dimensions. Using the imprecise and uncertain early-stage product information, each design option is assessed by the model with respect to the hierarchical evaluation criteria. Lifecycle engineering methods, such as lifecycle assessment and lifecycle costing analysis, are applied to the generation of the evaluation criteria. This would provide designers with a more complete lifecycle view about the product’s sustainability potentials to support decision-making in evaluation and selection of conceptual designs. The proposed approach has been implemented in a sustainable design decision-support software prototype. Illustrative examples are discussed in the paper to demonstrate the use of the approach and the prototype in conceptual design selection of a consumer product.

Effects of payoff and task context on academic risk taking.

1991 ◽  
Vol 83 (4) ◽  
pp. 499-507 ◽  
Author(s):  
Margaret M. Clifford ◽  
Fen-chang Chou
Keyword(s):  
Risk Taking ◽  
Task Context ◽  
Academic Risk ◽  
And Task
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