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PubMed1990

Effects of redundancy in the comparison of speech and pictorial displays in the cockpit environment.

Synthesised speech and pictorial displays were compared in a spatially compatible simulated cockpit environment. Messages of high or low levels of redundancy were presented to subjects in both modality conditions. Subjects responded to warnings presented in a warning-only condition and in a dual-task condition, in which a simulated flight task was performed with visual and manual input/output modalities. Because the amount of information presented in most real-world applications and experimental paradigms is quantifiably large with respect to present guidelines for the use of synthesised speech warnings, the low-redundancy condition was hypothesised to allow for better performance. Results showed that subjects respond quicker to messages of low redundancy in both modalities. It is suggested that speech messages with low-redundancy levels were effective in minimising message length and ensuring that messages did not overload the short-term memory required to process and maintain speech in memory. Manipulation of phrase structure was used to optimise message redundancy and enhance the conceptual compatibility of the message without increasing message length or imposing a perceptual cost or memory overload. The results also suggest that system response times were quicker when synthesised speech warnings were used. This result is consistent with predictions from multiple resource theory which states that the resources required for the perception of verbal warnings are different from those for the flight task. It is also suggested that the perception of a pictorial display requires the same resources used for the perception of the primary flight task. An alternative explanation is that pictorial displays impose a visual scanning cost which is responsible for decreased performance. Based on the findings reported here, it is suggested that speech displays be incorporated in a spatially compatible cockpit environment because they allow equal or better performance when compared with pictorial displays. More importantly, the amount of time that the operator must direct his vision away from information vital to the flight task is decreased.

Journal Article↗
PubMed1993

Thinking about genetic redundancy.

Partial functional redundancy among genes is frequently observed in a wide range of organisms and processes, but the selective value of such redundancy is not immediately apparent. Any fully redundant function should be evolutionarily unstable: unless selection acts to maintain the redundancy it will tend to be lost by mutational drift. I discuss four possible mechanisms by which selection might act to maintain genetic redundancy.

Animals↗
PubMed2004

Redundancy gain in simple reaction time following partial and complete callosotomy.

Four subjects with partial or complete section of the corpus callosum were tested on simple reaction time (RT) to visual stimuli presented either singly in one or other visual field, or simultaneously in both visual fields. The subject with posterior callosal section showed evidence of redundancy gain with bilateral stimuli beyond that attributable to probability summation ("enhanced" redundancy gain), and prolonged interhemispheric transfer. One of the two subjects with anterior section, like normals, showed little evidence of enhanced redundancy gain, and no evidence of prolonged interhemispheric transfer. The other did show some enhanced redundancy gain at the fast end of the RT distribution. These and other results suggest that the posterior corpus callosum provides the principal route or routes of interhemispheric transfer of the information required for simple visuomotor responses, and is also responsible for the much reduced redundancy gain in normal subjects relative to that in split-brained subjects. The subject with complete callosal section was unusual in that he responded only very rarely to stimuli in the left visual field (LVF), yet he showed markedly reduced RTs to bilateral relative to right visual field (RVF) stimuli.

Adult↗
PubMed2002

A new redundant variable pruning approach--minor latent variable perturbation-PLS used for QSAR studies on anti-HIV drugs.

A new approach for eliminating the redundant variables in the multivariable data matrix encountered in QSAR studies, minor latent variable perturbation (MLVP)-PLS method has been proposed. In the latent variable (LV) space, the minor latent variables (LVs) with small covariances are mainly formulated by linear combinations of the redundant variables including information-deficient and highly correlative ones, while the major LVs with large covariances are mainly contributed by the informative variables. Deleting a minor LV, which is equivalent to a perturbation for LV space, could make the redundant variables not well be represented in LV subspace, leading to strong variation of their PLS regression coefficients. The informative variables could still be normally represented in LV subspace with the PLS regression coefficients remaining relatively stable. MLVP-PLS utilizes this fact to discriminate the informative and redundant variables. It gradually identifies and eliminates the redundant variables according to the relative variation of PLS regression coefficients after perturbations are given. The elimination process is terminated according to some proposed criteria. Applying the method to the quantitative structure-activity relationship (QSAR) studies on TIBO derivatives as potential anti-HIV drugs has demonstrated the feasibility and robustness of the proposed approach. A deeper insight into the effect of different structural parameters on the bio-activity of TIBO derivatives has been reached.

Anti-HIV Agents↗
PubMed1987

An hypothesis about redundancy and reliability in the brains of higher species: analogies with genes, internal organs, and engineering systems.

The phenomena of behavioral resistance to massive brain damage and behavioral recovery from brain damage suggest there is redundancy in neural tissue. This paper uses basic concepts from probability theory and reliability engineering, as a first step toward more rigorously establishing the plausibility of the redundancy hypothesis. Exponential effects in the relevant formulas lead to results that are intuitively surprising. Thus, within a broad range of parametric assumptions related to lifespan and number of neurons or neural subsystems, it appears that the human brain may be at least twice as large as it would have to be for short-term survival. Simple reliability models suggest that redundancies are in parallel connections of smallest subsystems, such as individual neurons. Other implications of the basic formulas concern the relation between backed-up subsystem reliability and lifetime usage frequency for each subsystem, and the evolution of approximately equal allocation of lifetime reliability among components of a system. In addition, the paper briefly reviews more complex reliability engineering approaches. Redundancy as a reason for neural mass action is compared to other theoretical reasons for mass action in sensorimotor function and learning. Relationships of the present hypothesis to other theories of recovery from brain damage and to theories of regressive trophic phenomena in ontogeny are briefly discussed; it is suggested that as stages of ontogeny progress, both redundancy and flexibility in simpler behavioral functions are traded away for a larger, more differentiated repertoire of complex functions and memories.

Animals↗
PubMed1997

Non-linear Feature Extraction by Redundancy Reduction in an Unsupervised Stochastic Neural Network.

Unsupervised feature extraction by a stochastic neural network can be defined as a minimization of the redundancy between the elements of the output layer, given complete information transfer from input to output. Redundancy minimization can be achieved by minimization of the mutual information between the units of the output layer. Complete information transfer is enforced by maximizing the mutual information of the input and output. With these two conditions we define a novel learning algorithm for stochastic recurrent networks. The minimum of redundancy corresponds to the extraction of statistically independent features, leading to a factorial representation of the environment. The resulting learning rule includes Hebbian and anti-Hebbian learning terms. These two terms are weighted by the amount of information transmitted in the learning synapse minus the grade of redundant information in the corresponding output neuron, giving thus, an information-theoretic interpretation of the proportionality constant of Hebb's biological rule. Simulations demonstrate the performance of this method. When a retina is simulated, the learning algorithm forms decorrelated receptive fields. This represents the first experiment that extends the results of the linear principle component analysis to the nonlinear case by a direct implementation of Barlow's principle of redundancy reduction for unsupervised features extraction by receptive fields formation in a retina model. Copyright 1997 Elsevier Science Ltd.

Journal Article↗
PubMed1985

Depression among men made involuntarily redundant.

Ninety-eight men aged 25-50, who were unemployed because of involuntary redundancy and out of work for 2-18 months, completed the Beck Depression Inventory (BDI) and the General Health Questionnaire (GHQ-30). Their scores were compared with those of a group of employed men matched for age and social class. The mean GHQ score for the redundant men was 13.0, compared with 4.0 for the employed group. The mean BDI score was 11.1 for the redundant group and 5.6 for the employed group. Eighteen per cent of the redundant men, compared with 6% of the employed group, scored 18 or more which are scores corresponding to those in depressive illness. We conclude that the prevalence of depressive illness may be increased among redundant men.

Adult↗
PubMedDate not supplied

Spatial coding and response redundancy in parallel visual pathways of the marmoset Callithrix jacchus.

Many neurons in the primary visual cortex (area V1) show pronounced selectivity for the orientation and spatial frequency of visual stimuli, whereas most neurons in subcortical afferent streams show little selectivity for these stimulus attributes. It has been suggested that this transformation is a functional sign of increased coding efficiency, whereby the redundancy (or overlap in response properties) is reduced at consecutive levels of visual processing. Here we compared experimentally the response redundancy in area V1 with that in the three main dorsal thalamic afferent streams, the parvocellular (PC), koniocellular (KC), and magnocellular (MC) divisions of the dorsal lateral geniculate nucleus (LGN) in marmosets. The spatial frequency and orientation tuning of single cells in the LGN and area V1 were measured, using luminance contrast sine-wave gratings. A joint spatial frequency-orientation response selectivity profile was calculated for each cell. Response redundancy for each population was estimated by cross-multiplication of the joint selectivity profiles for pairs of cells. We show that when estimated in this way, redundancy in LGN neurons is approximately double that of neurons in cortical area V1. However, there are differences between LGN subdivisions, such that the KC pathway has a spatial representation that lies between the redundant code of the PC and MC pathways and the more efficient sparse spatial code of area V1.

Action Potentials↗
PubMed1999

Redundancy gains for visual search after complete commissurotomy.

Redundant-targets effects (RTE) for visual search were investigated in 2 commissurotomy patients (L.B., N.G.). L.B., who showed no evidence of visual interhemispheric transfer, exhibited a paradoxical enhancement of the redundancy gain in the bilateral compared with the within-hemifield redundant-targets conditions, whereas N.G., who showed evidence of interhemispheric transfer of visual information, exhibited no enhancement of the bilateral redundancy gain. When only uncrossed responses were considered, both bilateral and within-field RTE were evident only when attentional demands were high. Bilateral redundant targets led to stronger gains, some indicative of coactivation, in the slower response hand. The authors suggest that the enhancement of the bilateral RTE comes about by neural coactivation, which is especially pronounced when the slower hemisphere elicits the response.

Adult↗
PubMed2004

Redundant data and exact helical cone-beam reconstruction.

This paper is about helical cone-beam reconstruction and the use of redundant data in the framework of two reconstruction methods. The first method is the approximate wedge reconstruction formula introduced by Tuy at the 3D meeting in 1999. The second method is a (exact) hybrid implementation of the exact filtered backprojection formula of Katsevich (2004 Adv. Appl. Math. at press) that combines filtering in the native cone-beam geometry with backprojection in the wedge geometry. The similarity of the two methods is explored and their image quality performance is compared for geometries with up to 112 detector rows. Furthermore, the concept of aperture weighting is introduced to allow the handling of variable amounts of redundant data. A reduction of motion artefacts using redundant data is demonstrated for geometries with 16, 32 and 112 detector rows using a pitch factor of 1.25. For scans with up to 100 rows, utilizing 50% of the redundant data provided excellent results without any introduction of cone-beam artefacts. For larger cone angles, an alternative approach that utilizes all available redundant data, even at reduced pitch factors, is suggested.

Algorithms↗
PubMed2005

A comprehensive and non-redundant database of protein domain movements.

MOTIVATION: The current DynDom database of protein domain motions is a user-created database that suffers from selectivity and redundancy. The aim of the analysis presented here was to overcome both these limitations and to produce both a comprehensive and a non-redundant description of domain movements from structures stored in the current protein data bank. RESULTS: A multi-step procedure is applied that starts with grouping proteins in the structural databank into families based on sequence similarity. Multiple sequence alignment, conformational clustering and a dimensional clustering method based on the Gram-Schmidt algorithm are applied to members of each family to remove dynamic redundancy in their domain movements. Representative domain movements are described in terms of domains, hinge axes and hinge-bending residues using the DynDom program. The results show that within an average family of 11.5 members, there are on average only 1.31 different domain movements indicating a high redundancy in the movements these structures represent. This verifies earlier findings that domain movements are usually highly controlled. Despite the removal of this considerable redundancy, the process has resulted in double the number of domain movements stored in the user-created database. The data are organized in a relational database with a web-interface. AVAILABILITY: The database can be browsed and searched at http://www.cmp.uea.ac.uk/dyndom CONTACT: sjh@cmp.uea.ac.uk.

Algorithms↗
PubMed1993

Influence of response selection and noise similarity on age differences in the redundancy gain.

We examined the impact of target redundancy for target-plus-noise (TPN) and target-only (TO) trials. Experiment 1 manipulated response selection load (two-choice vs go/no-go) and Experiment 2 (all two-choice) varied noise redundancy (single or cumulative noise letters) on a visual search, divided attention task in which target letters were presented in one, two, or three corners of a four-corner display. Half of the trials also included noise letters. For Experiment 1, there was a definite redundancy gain for TO trials. Furthermore, older adults, relative to young adults, evidenced an even larger redundancy gain for TO trials than for TPN trials, although response selection load did not interact with age. These results are consistent with the notion that older adults exhibit a processing resources decrement. For Experiment 2, older adults evidenced a relatively larger redundancy gain for TPN trials than for TO trials, and this was especially the case for TPN trials in which all nontarget locations were filled with noise letters. Experiment 2 results are consistent with the notion that older adults also exhibit a selective attention decrement.

Adolescent↗
PubMed1980

Intensity of imperative signal influences on redundancy deficit and latency in process schizophrenics.

The resilience of the redundancy deficit pattern of schizophrenic reaction time performance was explored by examining the resistance of redundancy deficit to an experimental manipulation of imperative signal intensity. Aversive levels of stimulation have been used to alter motivation and shown to normalize schizophrenic performance in other research. In this study, 20 schizophrenic patients were administered a reaction time task under conditions of usual motivation and, 1 day later, under conditions of aversive motivation induced by high decibel levels of stimulation. The redundancy deficit pattern was observed with usual motivation but not with so-called biological motivation. The results are discussed from the points of view of the utility of redundancy deficit as an index of vulnerability to schizophrenia, implications for attentional and motivational theories of schizophrenia, and finally, in terms of the more general role of aversive stimulation in schizophrenic deficit. The finding that redundancy deficit is ameliorated by aversive motivation is consistent with theories suggesting that schizophrenics respond primarily to negative motivation. Garmezy's suggestion that the common denominator of the multiplicity of schizophrenic deficits may lie in motivational factors, particularly the prepotent avoidance motive, is supported by these results.

Adult↗
PubMed1980

The value of redundancy in chronic bipolar pacemaker electrode systems.

Bipolar pacing systems, because of the presence of two intracardiac electrodes, provide lead redundancy. This allows conversion of bipolar to unipolar pacing or the reversal of lead polarity. During a 3-year period, this redundancy was utilized in 34 (13.7%) of 248 patients with chronic bipolar lead systems during follow-up pacemaker surgery. Of the 34 patients, elective pulse generator change was the most frequent indication for surgery (23 patients) and in this group redundancy was used most often to select the lead configuration with the highest R-wave amplitude and lowest stimulation threshold, or to solve the problem of weld defects of the connector pins or frayed insulation. The remaining 11 patients underwent surgery for pacemaker system malfunction and in this group redundancy was used to avoid the need for lead repositioning or placement of a new catheter system. Lead redundancy in those patients in whom bipolar pacing has been selected provides flexibility at the time of additional pacemaker surgery, and its use may obviate the need for a change in catheter system when stimulation thresholds are excessive, wire fraction is irreparable, or bipolar sensing signals are inadequate.

Electrodes, Implanted↗
PubMed1985

Mapping the genes in the terminal redundancy of bacteriophage SPO1 with restriction endonucleases.

Although most early transcription from SPO1, a lytic DNA bacteriophage of Bacillus subtilis, is specified by the 12.6-kilobase region of the terminal redundancy, early genes from this region have not been identified by standard genetic means. We mapped genes to DNA regions of the SPO1 terminal redundancy by analyzing in vitro protein synthesis from isolated SPO1 restriction fragments in an Escherichia coli-coupled transcription-translation cell-free system. DNA from the terminal redundancy directs the synthesis in vitro of eleven proteins, e3, e4, e6, e7, e9, e12, e15, e16, e18, e20, and e21, which correspond in mobility on sodium dodecyl sulfate-polyacrylamide gels with authentic SPO1 early proteins. From their mapped positions on the DNA, genes were positioned downstream from most, but not all, of the twelve early promoter regions identified in vitro in the terminal redundancy. The temporal patterns of early protein synthesis in vivo suggest a differential turning on and off of early promoters in the terminal redundancy. Both in vivo and in vitro evidence suggests the existence of previously unidentified early promoter regions upstream from the genes for e6 and e4 as well as a middle promoter region upstream from the gene for e16.

Bacillus subtilis↗
PubMed2006

Yeast UBL-UBA proteins have partially redundant functions in cell cycle control.

BACKGROUND: Proteins containing ubiquitin-like (UBL) and ubiquitin associated (UBA) domains have been suggested to shuttle ubiquitinated substrates to the proteasome for degradation. There are three UBL-UBA containing proteins in budding yeast: Ddi1, Dsk2 and Rad23, which have been demonstrated to play regulatory roles in targeting ubiquitinated substrates to the proteasome for degradation. An involvement of these proteins in cell cycle related events has also been reported. We tested whether these three proteins act redundantly in the cell cycle. RESULTS: Here we show that the UBL-UBA proteins are partially redundant for cell cycle related roles. RAD23 is redundant with DDI1 and DSK2, but DDI1 and DSK2 are not redundant with each other and the triple deletion shows a synthetic effect, suggesting the existence of at least two roles for RAD23 in cell cycle control. The rad23Deltaddi1Deltadsk2Delta triple deletion strain delays both in G2/M-phase and in mid-anaphase at high temperatures with duplicated spindle pole bodies. Cell cycle progression in the triple deletion strain can only be partially rescued by a rad23 allele lacking the c-terminal UBA domain, suggesting that RAD23 requires its c-terminal UBA domain for full function. In addition to their ability to bind ubiquitin and the proteasome, the UBL-UBA proteins also share the ability to homodimerize. Rad23 and Dsk2 dimerization requires their UBL and/or UBA domains whereas Ddi1 dimerization does not. Here we show that Ddi1 homodimerization is necessary for its cell cycle related functions. CONCLUSION: The three yeast UBL-UBA proteins have partially redundant roles required for progression through mitosis.

Journal Article↗
PubMed1996

Redundant control of Ultrabithorax by zeste involves functional levels of zeste protein binding at the Ultrabithorax promoter.

Many biological processes appear to be controlled by functionally redundant genes or pathways, but it has proven difficult to understand the nature of this redundancy. Here, we have analyzed a redundant regulatory interaction between the Drosophila transcription factor zeste and the homeotic gene Ultrabithorax. Mutations in zeste do not affect the cis-regulation of the endogenous Ultrabithorax gene; however, the expression of small Ultrabithorax promoter constructs is strongly dependent upon zeste. We show that this difference is due to redundant cis-regulatory elements in the Ultrabithorax gene, which presumably contain binding sites for factors that share the function of zeste. We also provide evidence suggesting that zeste and the gene encoding the GAGA factor have an overlapping function in regulating Ultrabithorax. Furthermore, we show that the zeste protein is bound at equal levels in vivo to a Ultrabithorax promoter construct, which zeste strongly activates, and to the identical promoter region in the endogenous Ultrabithorax gene, which zeste redundantly regulates. These results suggest that zeste is significantly active in the wild-type animal and not simply a factor that is induced as a back-up when other activators fail.

Animals↗
PubMed2005

Redundancy and synergy of neuronal ensembles in motor cortex.

We examined the ability of neuronal ensembles from rat motor cortex to predict behavioral performance during a reaction time task. We found that neurons that were the best individual predictors of task performance were not necessarily the neurons that contributed the most predictive information to an ensemble of neurons. To understand this result, we applied a framework for quantifying statistical relationships between neurons (Schneidman et al., 2003) to all possible combinations of neurons within our ensembles. We found that almost all neurons (96%) contributed redundant predictive information to the ensembles. This redundancy resulted in the maintenance of predictive information despite the removal of many neurons from each ensemble. Moreover, the balance of synergistic and redundant interactions depended on the number of neurons in the ensemble. Small ensembles could exhibit synergistic interactions (e.g., 23 +/- 9% of ensembles with two neurons were synergistic). In contrast, larger ensembles exhibited mostly redundant interactions (e.g., 99 +/- 0.1% of ensembles with eight neurons were redundant). We discuss these results with regard to constraints on interpreting neuronal ensemble data and with respect to motor cortex involvement in reaction time performance.

Action Potentials↗