Masking, Information Integration, and Tactile Pattern Perception: A Comparison of the Isolation and Integration Hypotheses

Two competing models of the effects of pattern element proximity, masking, and perceptual integration on the discriminability of spatiotemporal vibrotactile patterns are compared. Kirman's ‘integration hypothesis' predicts that pattern perception is facilitated by a process of perceptual integration which requires that pattern elements be presented in close spatial and temporal proximity. Conversely, the ‘isolation hypothesis' predicts that the strong masking effects which occur when pattern elements are presented in close proximity impede the perception of patterns. Traditional masking studies do not provide a fair test of these two hypotheses because they rely on methods that measure the subject's ability to identify the target when the target is presented in conjunction with the mask, rather than the discriminability of the complex percept resulting from the integration of the target and mask. To account for this, a new procedure was devised where the amount of interelement masking and the discriminability of the pattern as a whole were measured independently as the spatial and temporal separation of the pattern elements were varied. As expected under both hypotheses, masking between pattern elements increased as either the spatial or the temporal separation between them was decreased. The pattern discrimination data also support the isolation hypothesis in that the patterns were discriminated less well with increasing temporal element separation with a similar but nonsignificant trend in the case of spatial separation. It is concluded that this new methodology should be applied to a wider range of tactile pattern processing situations in order to assess the generality of the results obtained.

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Tactile Pattern Discrimination at Adjacent Locations along the Proximal — Distal Axis of the Index Finger

Perception ◽

10.1068/p5385 ◽

2006 ◽

Vol 35 (1) ◽

pp. 125-136 ◽

Cited By ~ 1

Author(s):

David T Horner

Keyword(s):

Index Finger ◽

Pattern Discrimination ◽

Tactile Pattern

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Latent likelihood ratio tests for assessing spatial kernels in epidemic models

Journal of Mathematical Biology ◽

10.1007/s00285-020-01529-3 ◽

2020 ◽

Vol 81 (3) ◽

pp. 853-873

Author(s):

David Thong ◽

George Streftaris ◽

Gavin J. Gibson

Keyword(s):

Likelihood Ratio ◽

Kernel Function ◽

Control Strategies ◽

Spatial Separation ◽

Likelihood Ratio Tests ◽

New Approach ◽

Competing Models ◽

Spatio Temporal ◽

Fully Bayesian ◽

The Relationship

Abstract One of the most important issues in the critical assessment of spatio-temporal stochastic models for epidemics is the selection of the transmission kernel used to represent the relationship between infectious challenge and spatial separation of infected and susceptible hosts. As the design of control strategies is often based on an assessment of the distance over which transmission can realistically occur and estimation of this distance is very sensitive to the choice of kernel function, it is important that models used to inform control strategies can be scrutinised in the light of observation in order to elicit possible evidence against the selected kernel function. While a range of approaches to model criticism is in existence, the field remains one in which the need for further research is recognised. In this paper, building on earlier contributions by the authors, we introduce a new approach to assessing the validity of spatial kernels—the latent likelihood ratio tests—which use likelihood-based discrepancy variables that can be used to compare the fit of competing models, and compare the capacity of this approach to detect model mis-specification with that of tests based on the use of infection-link residuals. We demonstrate that the new approach can be used to formulate tests with greater power than infection-link residuals to detect kernel mis-specification particularly when the degree of mis-specification is modest. This new tests avoid the use of a fully Bayesian approach which may introduce undesirable complications related to computational complexity and prior sensitivity.

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Comparison of the Spatial Limits on Direction Selectivity in Visual Areas MT and V1

Journal of Neurophysiology ◽

10.1152/jn.00767.2004 ◽

2005 ◽

Vol 93 (3) ◽

pp. 1235-1245 ◽

Cited By ~ 25

Author(s):

Mark M. Churchland ◽

Nicholas J. Priebe ◽

Stephen G. Lisberger

Keyword(s):

Apparent Motion ◽

Great Majority ◽

Spatial Separation ◽

Direction Selectivity ◽

Temporal Separation ◽

Temporal Area ◽

Mean Values ◽

V1 Neurons ◽

Preferred Direction ◽

The Difference

We recorded responses to apparent motion from directionally selective neurons in primary visual cortex (V1) of anesthetized monkeys and middle temporal area (MT) of awake monkeys. Apparent motion consisted of multiple stationary stimulus flashes presented in sequence, characterized by their temporal separation (Δ t) and spatial separation (Δ x). Stimuli were 8° square patterns of 100% correlated random dots that moved at apparent speeds of 16 or 32°/s. For both V1 and MT, the difference between the response to the preferred and null directions declined with increasing flash separation. For each neuron, we estimated the maximum flash separation for which directionally selective responses were observed. For the range of speeds we used, Δ x provided a better description of the limitation on directional responses than did Δ t. When comparing MT and V1 neurons of similar preferred speed, there was no difference in the maximum Δ x between our samples from the two areas. In both V1 and MT, the great majority of neurons had maximal values of Δ x in the 0.25–1° range. Mean values were almost identical between the two areas. For most neurons, larger flash separations led to both weaker responses to the preferred direction and increased responses to the opposite direction. The former mechanism was slightly more dominant in MT and the latter slightly more dominant in V1. We conclude that V1 and MT neurons lose direction selectivity for similar values of Δ x, supporting the hypothesis that basic direction selectivity in MT is inherited from V1, at least over the range of stimulus speeds represented by both areas.

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Dissociable Neural Information Dynamics of Perceptual Integration and Differentiation during Bistable Perception

Cerebral Cortex ◽

10.1093/cercor/bhaa058 ◽

2020 ◽

Vol 30 (8) ◽

pp. 4563-4580 ◽

Cited By ~ 5

Author(s):

Andrés Canales-Johnson ◽

Alexander J Billig ◽

Francisco Olivares ◽

Andrés Gonzalez ◽

María del Carmen Garcia ◽

...

Keyword(s):

Information Integration ◽

Information Dynamics ◽

Opposite Pattern ◽

Perceptual Integration ◽

Information Measures ◽

Bistable Perception ◽

Neural Information ◽

Oscillatory Power ◽

Parallel Streams ◽

Perceptual Differentiation

Abstract At any given moment, we experience a perceptual scene as a single whole and yet we may distinguish a variety of objects within it. This phenomenon instantiates two properties of conscious perception: integration and differentiation. Integration is the property of experiencing a collection of objects as a unitary percept and differentiation is the property of experiencing these objects as distinct from each other. Here, we evaluated the neural information dynamics underlying integration and differentiation of perceptual contents during bistable perception. Participants listened to a sequence of tones (auditory bistable stimuli) experienced either as a single stream (perceptual integration) or as two parallel streams (perceptual differentiation) of sounds. We computed neurophysiological indices of information integration and information differentiation with electroencephalographic and intracranial recordings. When perceptual alternations were endogenously driven, the integrated percept was associated with an increase in neural information integration and a decrease in neural differentiation across frontoparietal regions, whereas the opposite pattern was observed for the differentiated percept. However, when perception was exogenously driven by a change in the sound stream (no bistability), neural oscillatory power distinguished between percepts but information measures did not. We demonstrate that perceptual integration and differentiation can be mapped to theoretically motivated neural information signatures, suggesting a direct relationship between phenomenology and neurophysiology.

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Size Distortions: Space-Time Interaction

Perception ◽

10.1068/v970102 ◽

1997 ◽

Vol 26 (1_suppl) ◽

pp. 114-114

Author(s):

S Chukova ◽

V E Gauzelman

Keyword(s):

Random Order ◽

Spatial Separation ◽

Experimental Session ◽

Reference Stimulus ◽

Temporal Separation ◽

Memory Processing ◽

Modified Method ◽

Time Interaction ◽

Modular Model ◽

Size Distortions

We used a modified method of constant stimuli to measure spatial interval discrimination thresholds. Horizontal intervals were indicated by a pair of dark vertical lines on a bright background. In each experimental session, thresholds were measured for seven reference stimuli, presented in random order. Reference stimulus separations varied from 9.52 to 16.66 min−1 in increments of 1.95 min−1. The interstimulus interval (ISI) was varied (50, 200, 500, and 1000 ms) between experimental sessions. Stimulus duration was constant at 500 ms. For all ISI durations, the point of subjective equality (PSE) for small spatial separation references was less than physical equality, the PSE for larger separations was greater, and the PSE was close to physical equality for reference stimuli in the centre of the range. This result is consistent with the modular model [V D Glezer, 1995 Vision and Mind (Mahwah, NJ: Lawrence Erlbaum)]. However, the magnitude of the PSE shifts was affected by the ISI duration: at 50 and 1000 ms, the small spatial intervals were more underestimated and the large ones were more overestimated than at 200 or 500 ms. The discriminability thresholds based on the slopes of the psychometric functions varied inversely with the ISI duration, but at the ISI of 1000 ms increased again. These findings demonstrate that in the sequential mode of presentation the temporal separation can be as important as the spatial separation distribution in determining the PSE. This suggests that these size distortions result more from memory processing than from spatial processing.

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The incidence of killer activity and extracellular proteases in tropical yeast communities

Canadian Journal of Microbiology ◽

10.1139/m97-046 ◽

1997 ◽

Vol 43 (4) ◽

pp. 328-336 ◽

Cited By ~ 41

Author(s):

Jacqueline Abranches ◽

Leda C. Mendonça-Hagler ◽

Allen N. Hagler ◽

Paula B. Morais ◽

Carlos A. Rosa

Keyword(s):

Killer Toxin ◽

Spatial Separation ◽

Extracellular Proteases ◽

Temporal Separation ◽

Killer Activity ◽

Killer Yeasts ◽

Sporobolomyces Roseus ◽

Nitrogen Nutrients ◽

Pichia Kluyveri ◽

Ascomycetous Yeasts

The presence of killer and proteolytic yeasts was studied among 944 isolates representing 105 species from tropical yeast communities. We found 13 killer toxin producing species, with Pichia kluyveri being the most frequent. Other killer yeast isolates were Candida apis, Candida bombicola, Candida fructus, Candida krusei, Candida sorbosa, Hanseniaspora uvarum, Issatchenkia occidentalis, Kloeckera apis, Kluyveromyces marxianus, Pichia membranaefaciens, Pichia ohmeri-like, and Sporobolomyces roseus. The communities from which killer yeasts were isolated had strains sensitive to them, and there were interspecific and intraspecific differences in the spectra of their killer activities. Pichia kluyveri had the broadest spectra of activity against sensitive isolates, and it apparently produced different toxins. The coexistence of sensitive and killer yeasts using the same substrate suggests that there is spatial separation in microhabitats or temporal separation in different stages of successions. Basidiomycetous yeasts were more frequently proteolytic than ascomycetous yeasts. Extracellular proteases could be important for the yeasts to have access to more nitrogen nutrients and obtain a better balance with available carbon sources.Key words: killer yeasts, extracellular proteases, tropical yeast communities.

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Divergence Thresholds as Functions of Temporal Separation, Spatial Separation, and Retinal Locus

Perceptual and Motor Skills ◽

10.2466/pms.1983.56.2.459 ◽

1983 ◽

Vol 56 (2) ◽

pp. 459-468 ◽

Cited By ~ 1

Author(s):

Marjorie J. Di Orio ◽

Thomas L. Harrington

Keyword(s):

Spatial Separation ◽

Retinal Locus ◽

Line Density ◽

Information Analysis ◽

Angular Divergence ◽

Temporal Separation ◽

Line Segments ◽

Fast Motion ◽

Straight Lines ◽

Form Information

Human thresholds were measured for the detection of angular divergence between straight lines using pairs of line segments. The dependence of these thresholds on temporal separation between the two lines, spatial separation, and retinal locus was assessed. Results were comparable to prior divergence thresholds obtained by Harrington and Harrington in their study of “blur patterns.” In blur patterns motion parameters may be processed partly or wholly as form information rather than as motion information per se. Harrington and Harrington had used moderate blurring velocities, for which information on both motion and form were present. Observers may have been responding either to motion or to form. The study reported here used briefly presented two-line “blur patterns” with only form information. Analysis suggested that the form components of fast motion-produced blur patterns could be processed by the human visual system. Neither temporal nor spatial separation was a significant determiner of thresholds in accordance with Harrington and Harrington who found no effect of blur-line density in the range studied. Retinal locus was a factor as it was with blur patterns. Some possible mechanisms for the detection of divergence indicated by these results are discussed.

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Resource partitioning between two species of Ceutorhynchus (Coleoptera: Curculionidae) on Echium plantagineum in a Mediterranean habitat

Bulletin of Entomological Research ◽

10.1017/s0007485300029230 ◽

1993 ◽

Vol 83 (3) ◽

pp. 345-351 ◽

Cited By ~ 9

Author(s):

Guy J. Forrester

Keyword(s):

Biological Control ◽

Resource Partitioning ◽

Spatial Separation ◽

Temporal Separation ◽

Southern France ◽

Early Larval Stage ◽

Tap Root ◽

Mediterranean Habitat ◽

Different Parts ◽

Original Index

AbstractTwo weevil species, Ceutorhynchus geographicus (Goeze) and C. larvatus Schultze, feed on Echium plantagineum (Boraginaceae) in southern France. This paper shows that they do not compete for resources in the host's native environment. Niche overlaps of the two weevils were measured using the proportional overlap measure and Morisita's original index. The two species showed significant overlap in niche requirements during the egg and early larval stage. During the final two larval instars, larvae feed on different parts of the plant, C. geographicus in the tap root and C. larvatus in the root crown. Spatial separation in niche requirements is augmented by a temporal separation, C. larvatus emerging in the field about one month earlier than C. geographicus. In Europe and in Australia, to which E. plantagineum has been introduced and has become a serious weed, the host-plant has an extended germination period during the autumn. The differences in emergence times of the two species mean that their niches are separated both in time and in space. Should the two species be released into Australia they would not compete for resources. They may, however, be able to displace other species of the stemfeeding guild that are also proposed as candidates for the biological control of E. plantagineum.

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