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PubMed1977

Temporal patterns, their distribution and redundancy in trains of spontaneous neuronal spike intervals of the feline hippocampus studied with a non-parametric technique.

A modification of the non-parametric technique for the analysis of temporal patterns in long trains of single neuronal spike intervals has been described and tested empiracally. The technique is based on inequality testing of sequential pairs of intervals. If the second interval in a pair is longer or shorter than or equal to the first interval, a(+), a(-), and a (0) is recorded respectively in sequential bins of the computer memory. Subsequently, the long sequences of signs are arranged into transition frequency matrices which are then converted into transition probability matrices of various complexity. In this manner, the sign permutations composed of 4, 5, 6, etc. signs were studied. First of all, the theoretical distribution of various sign permutations was derived, assuming that the arrangement of intervals that generate the signs is totally independent. The theoretical distribution of signs permutations in tetragrams, pentagrams and hexagrams constitute the 'controls' with which the empirical data can be compared. In this manner, using the chi-square test, the total deviation of a studied neuronal output from an independent state can be quantified. The empirical data showed a consistent deviation from the theoretical distribution of sign permutations during REM sleep, as compared to slow wave sleep which was characterized by an almost perfect theoretical distribution of sign permutations. This indicates that slow wave sleep is associated with relaxation of constraints that are responsible for the emergence of specific patterns. In addition, redundancies in the occurrence of sign permutations, and the linear relationships between them, have been defined and tested empirically. The apparent discrepancies between the redundancies, based on theoretical symmetry in sign distribution and the linear redundancy that fits the empirical data, have been defined and discussed.

Action Potentials↗
PubMed1991

Facial muscle activity and EEG recordings: redundancy analysis.

The present study explored the use of redundancy analysis, a multivariate technique for assessment of interset association, to examine facial muscle contamination of EEG recordings in studies involving covert levels of emotional expression. Redundancy analyses were performed on simultaneously recorded EEG and facial EMG data obtained in an emotion induction paradigm. Redundancy indices obtained suggest that (1) the amount of variance in EEG activity that can be explained by facial muscle activity under such conditions is minimal, and (2) the EEG alpha band may be at least as or even more susceptible to muscle contamination as the beta band.

Adult↗
PubMed1994

Redundant parasympathetic and sympathoadrenal mediation of increased glucagon secretion during insulin-induced hypoglycemia in conscious rats.

Both the parasympathetic and sympathoadrenal inputs to the pancreas can stimulate glucagon release and are activated during hypoglycemia. However, blockade of only one branch of the autonomic nervous system may not reduce hypoglycemia-induced glucagon secretion, because the unblocked neural input is sufficient to mediate the glucagon response, ie, the neural inputs are redundant. Therefore, to determine if parasympathetic and sympathoadrenal activation redundantly mediate increased glucagon secretion during hypoglycemia, insulin was administered to conscious rats pretreated with a muscarinic antagonist (methylatropine, n = 7), combined alpha- and beta-adrenergic receptor blockade (tolazoline + propranolol, n = 5) or adrenergic blockade + methylatropine (n = 7). Insulin administration produced similar hypoglycemia in control and antagonist-treated rats (25 to 32 mg/dL). In control rats (n = 9), plasma immunoreactive glucagon (IRG) increased from a baseline level of 125 +/- 11 to 1,102 +/- 102 pg/mL during hypoglycemia (delta IRG = +977 +/- 98 pg/mL, P < .0005). The plasma IRG response was not significantly altered either by methylatropine (delta IRG = +677 +/- 141 pg/mL) or by adrenergic blockade (delta IRG = +1,374 +/- 314 pg/mL). However, the IRG response to hypoglycemia was reduced to 25% of the control value by the combination of adrenergic blockade + methylatropine (delta IRG = +250 +/- 83 pg/mL, P < .01 v control rats). These results suggest that the plasma glucagon response to hypoglycemia in conscious rats is predominantly the result of autonomic neural activation, and is redundantly mediated by the parasympathetic and sympathoadrenal divisions of the autonomic nervous system.

Adrenal Glands↗
PubMed1983

On the terminally redundant sequences of bacteriophage T3 DNA.

The nucleotide sequences of the termini of mature DNA from T3 phage were determined. A directly repeated sequence of 230 base pairs, corresponding to the terminal redundancy of T3 DNA, was found in the left and right end of the genome. The sequence of the terminal regions of T3 DNA was compared with that of T7 DNA. There are discrete sequences with significant homology, specifically in the regions around the two ends of the terminally redundant sequences. 5'-CCTAAAG and its variants appear frequently in both ends of the genome. T3 DNA fragments carrying the terminally redundant sequences were isolated from concatemeric DNA and analyzed by restriction enzymes.

Base Sequence↗
PubMed1983

Positional variability in redundant lumbar nerve-root syndrome.

A case of redundant lumbar nerve roots associated with lumbar canal stenosis is described. At myelography, the redundant nerve roots proximal to a site of blockage were noted to disappear on flexion and extension while similar redundancy developed distally. The etiology of this condition is discussed along with the differential diagnosis.

Female↗
PubMed1995

Efficient low redundancy large-scale DNA sequencing at EMBL.

An efficient low redundancy DNA sequencing strategy should allow high accuracy determination of the consensus sequence on both strands of a DNA fragment from a minimal number of sequencing reactions with minimal overlap. At EMBL we developed a directed strategy for cosmid-scale sequencing based on primer walking, whereas most other sequencing projects of this scale rely on the random 'shotgun' strategy. In our strategy, highly accurate raw data are obtained from automated double-stranded Sanger dideoxy sequencing with inexpensive walking primers (8 to 10 $ per primer), T7 DNA polymerase and internal labelling by fluorescein-15- dATP on A.L.F. DNA sequencers (Pharmacia Biotech). The use of 60-cm long glass plates enables reading length of up to 1000 bases. Comparing various random and directed sequencing strategies in the course of the European Community yeast genome sequencing project on cosmids from chromosomes IX, XI and XV, primer walking was found to be the strategy resulting in the lowest possible redundancy of 2.6 to 2.8. Future development of the sequencing strategy is based on the new EMBL 2-dye sequencing device for simultaneous sequencing on both strands, and implementation of an initial limited random sequencing phase to reduce the number of walking primers required by a factor of 3, while still maintaining a low redundancy of approx. 3.

Animals↗
PubMed1993

Evolution of genetic redundancy for advanced players.

An ever expanding database on the sequence organization and repetition of genic and non-genic components of nuclear and organelle genomes reveals that the vast majority of sequences are subject to one or other mechanism of DNA turnover (gene conversion, unequal crossing over, slippage, retrotransposition, transposition and others). Detailed studies, using novel methods of experimental detection and analytical procedures, show that such mechanisms can operate one on top of another and that wide variations in their unit lengths, biases, polarities and rates create bizarre and complex patterns of genetic redundancy. The ability of these mechanisms to operate both within and between chromosomes implies that realistic models of the evolutionary dynamics of redundancy, and of the potential interaction with natural selection in a sexual species, need to consider the diffusion of variant repeats across multiple chromosome lineages, in a population context. Recently, important advances in both experimental and analytical approaches have been made along these lines. There is increasing awareness that genetic redundancy and turnover induces a molecular co-evolution between functionally interacting genetic systems in order to maintain essential functions.

Animals↗
PubMed2004

Exaggerated redundancy gain in the split brain: a hemispheric coactivation account.

Recent studies of redundancy gain indicate that it is especially large when redundant stimuli are presented to different hemispheres of an individual without a functioning corpus callosum. This suggests the hypothesis that responses to redundant stimuli are speeded partly because both hemispheres are involved in the activation of the response. A simple formal model incorporating this idea is developed and then elaborated to account for additional related findings. Predictions of the latter model are in good qualitative agreement with data from a number of sources, and there is neuroanatomic and psychophysiological support for its underlying structure.

Brain↗
PubMed2006

Neural basis of redundancy effects in visual object categorization.

Bilateral redundant information often leads to improved detection performance compared to only unilateral input. This experiment investigates redundancy effects at the level of object processing in behavioral and functional imaging data. Subjects received different combinations of categorical information presented to both visual hemifields simultaneously. For pictures of faces as well as for pictures of buildings, response latencies were faster when two pictures from the same object category were presented compared to two pictures from different categories. This behavioral advantage was accompanied by increased activation in the respective object-selective areas, i.e. in the Fusiform Face Area (FFA) for pictures of faces and in the Parahippocampal Place Areas (PPAs) for pictures of buildings. These results suggest an involvement of visual object-selective areas in the behavioral redundancy gain.

Adult↗
PubMed2005

Redundancy in the population code of the retina.

We have explored the manner in which the population of retinal ganglion cells collectively represent the visual world. Ganglion cells in the salamander were recorded simultaneously with a multielectrode array during stimulation with both artificial and natural visual stimuli, and the mutual information that single cells and pairs of cells conveyed about the stimulus was estimated. We found significant redundancy between cells spaced as far as 500 mum apart. When we used standard methods for defining functional types, only ON-type and OFF-type cells emerged as truly independent information channels. Although the average redundancy between nearby cell pairs was moderate, each ganglion cell shared information with many neighbors, so that visual information was represented approximately 10-fold within the ganglion cell population. This high degree of retinal redundancy suggests that design principles beyond coding efficiency may be important at the population level.

Animals↗
PubMed2005

The effects of redundant stimuli on visuospatial processing in developmental dyslexia.

The interhemispheric deficit theory of dyslexia postulates that reading difficulties can arise from abnormal communication/collaboration between the cerebral hemispheres. A currently popular way to gather information about interhemispheric processing and integration is with the redundant stimuli task, where participants respond to stimuli presented to the left visual field, right visual field, or both visual fields simultaneously. In neurologically normal individuals, response times to bilateral simple stimulus presentations are faster than response times to a single stimulus in either visual field alone (referred to as redundancy gain). In contrast, individuals with no corpus callosum exhibit greater redundancy gains than would be expected by probability summation. In the present study, 11 children with phonological dyslexia showed a similar "over violation" of the probability (race) model when responding with the left but not the right hand. This asymmetry was not found in age- and IQ-matched control children. The results are at least partially consistent with the notion of phonological dyslexia involving deficits in the transfer of information across the corpus callosum.

Articulation Disorders↗
PubMed2005

Evidence of functional redundancy between MID proteins: implications for the presentation of Opitz syndrome.

Opitz G/BBB syndrome (OS) is a congenital defect characterized by hypertelorism and hypospadias, but additional midline malformations are also common in OS patients. X-linked OS is caused by mutations in the ubiquitin ligase MID1. In chick, MID1 is involved in left-right determination: a mutually repressive relationship between Shh and cMid1 in Hensen's node plays a key role in establishing the avian left-right axis. We have utilized our existing knowledge of the molecular basis of avian L/R determination to investigate the possible existence of functional redundancy between MID1 and its close homologue MID2. The expression of cMid2 overlaps with that of cMid1 in the node, and we demonstrate that MID2 can both mimic MID1 function as a right side determinant and rescue the laterality defects caused by knocking down endogenous MID proteins in the node. Our results show that MID2 is able to compensate for an absence in MID1 during chick left-right determination and may explain why OS patients do not suffer laterality defects despite the association between midline and L/R development. The demonstration of functional redundancy between MID1 and MID2 in the node provides supports for the hypothesis that partial functional redundancy between MID proteins in other developing structures contributes to the wide variability of OS phenotype.

Abnormalities, Multiple↗
PubMed2006

Unique and redundant functions of C. elegans HP1 proteins in post-embryonic development.

HP1 proteins are essential components of heterochromatin and contribute to the transcriptional repression of euchromatic genes. Although most species contain more than one HP1 family member which differ in their chromosomal distribution, it is not known to what extent the activity of these different family members is redundant or specific in a developmental context. C. elegans has two HP1 homologues, HPL-1 and HPL-2. While HPL-2 functions in vulval and germline development, no function has so far been attributed to HPL-1. Here we report the characterization of an hpl-1 null allele. We show that while the absence of hpl-1 alone results in no obvious phenotype, hpl-1;hpl-2 double mutants show synthetic, temperature sensitive phenotypes including larval lethality and severe defects in the development of the somatic gonad. Furthermore, we find that hpl-1 has an unexpected role in vulval development by acting redundantly with hpl-2, but not other genes previously implicated in vulval development. Localization studies show that like HPL-2, HPL-1 is a ubiquitously expressed nuclear protein. However, HPL-1 and HPL-2 localization does not completely overlap. Our results show that HPL-1 and HPL-2 play both unique and redundant functions in post-embryonic development.

Alleles↗
PubMed1998

What proportion of common diagnostic tests appear redundant?

PURPOSE: To identify ancillary tests for which there are criteria defining the earliest interval at which a repeat test might be indicated, to determine how often each test is repeated earlier than these intervals and, if repeated, provides useful information. SUBJECTS AND METHODS: We performed a retrospective cohort study of 6,007 adults discharged from a large teaching hospital during a 3-month period in 1991. We measured the proportion of commonly performed diagnostic tests that were redundant, and their associated charges. RESULTS: Of the 6,007 patients discharged, 5,289 (88%) had at least one of 12 target tests performed. Overall, 78,798 of the target tests were performed during the study period, of which 22,237 (28%) were repeated earlier than test-specific predefined intervals. This percentage varied substantially by test (range, 2% to 62%). To assess how many early repeats were justified, we performed chart reviews in a random sample stratified by test. For two tests, nearly all the initial results in the sample were abnormal, and all repeats were considered justified. Of early repeats following a normal initial result for the remaining 10 tests, chart review found no clinical indication for 92%, and a weighted mean of 40% appeared redundant. Overall, 8.6% of these 10 tests appeared redundant; if these were not performed, the annual charge reductions would be $930,000 at our hospital, although the impact on costs would be much smaller. CONCLUSIONS: For some tests, an important proportion are repeated too early to provide useful clinical information. Most such tests might be eliminated using computerized reminder systems.

Adult↗
PubMed1975

Comprehending a word: the influence of speed and redundancy on auditory comprehension in aphasia.

To assess the contribution of various factors to comprehension of a target word, an auditory comprehension test was devised and administered to a series of aphasic patients. Patients were required to select from an array that picture which corresponded to a spoken target word. Each patient heard the target word under five conditions: (1) target spoken alone; (2) target embedded in a neutral (low redundancy) sentence enunciated at a normal rate of speaking; (3) target in a neutral sentence enunciated at a slow rate of speaking; (4) target embedded in a sentence containing semantic support (high redundancy); (5) target embedded in a sentence containing a semantically-deceptive element. Semantic redundancy and rate of presentation made contributions to comprehensibility. Semantic confusions were prevalent among all aphasics but, contrary to earlier reports, posterior patients were especially prone to acoustic confusions. Except for conduction aphasics, patients were more likely to confuse words which began with the same sounds than words which ended with the same sounds. Patients with adequate comprehension at the start of the testing displayed a uniform tendency to improve on the conditions administered later, while those with impaired comprehension at the start usually did not.

Aphasia↗
PubMed2003

Removing the redundancy from randomised gene libraries.

Amino acid substitution plays a vital role in both the molecular engineering of proteins and analysis of structure-activity relationships. High-throughput substitution is achieved by codon randomisation, which generates a library of mutants (a randomised gene library) in a single experiment. For full randomisation, key codons are typically replaced with NNN (64 sequences) or NN(G)(CorT) (32 sequences). This obligates cloning of redundant codons alongside those required to encode the 20 amino acids. As the number of randomised codons increases, there is therefore a progressive loss of randomisation efficiency; the number of genes required per protein rises exponentially. The redundant codons cause amino acids to be represented unevenly; for example, methionine is encoded just once within NNN, whilst arginine is encoded six times. Finally, the organisation of the genetic code makes it impossible to encode functional subsets of amino acids (e.g. polar residues only) in a single experiment. Here, we present a novel solution to randomisation where genetic redundancy is eliminated; the number of different genes equals the number of encoded proteins, regardless of codon number. There is no inherent amino acid bias and any required subset of amino acids may be encoded in one experiment. This generic approach should be widely applicable in studies involving randomisation of proteins.

Amino Acid Substitution↗
PubMed1999

Choosing negative symptom instruments: issues of representation and redundancy.

Assuming that the negative syndrome in schizophrenia may be multidimensional, this study examines how conclusions about the structure of negative symptoms may be influenced by the particular rating scale used, the level of data reduction used (such as total, subscale and individual item scores), and also the type of data analyses used to compare scales. Forty-seven subjects with RDC schizophrenia were rated on three instruments: the negative symptom subscale of the BPRS (BPRS-WR); the negative symptom subscale of the PANSS (PANSS-NS); and the SANS. Comparisons were made of different levels of data reduction and different methods of analysis, which included bivariate correlation, bi-multivariate canonical correlation and redundancy analysis. We found that while the total scores from all three scales were highly correlated and therefore highly redundant, both the individual items and subscale scores from the SANS contained information independent of the BPRS-WR, and also, to a lesser extent, of the PANSS-NS. When the BPRS-WR was correlated with either the SANS or the PANSS-NS, one strong canonical variate (CV) emerged, on which all or most items loaded, particularly the affective items. When the SANS and PANSS-NS were correlated, this component again emerged along with three less strong but interpretable components. When examining the non-symmetrical redundancy, we found that the BPRS-WR variates explained 40% of the SANS variance, while conversely the SANS variates explained 80% of the BPRS-WR variance. The PANSS-NS variates were found to explain 58% of the SANS variance, while the SANS variates explained 85% of the PANSS-NS variance. Finally, the PANSS-NS variates explained 79% of the BPRS-WR variance, while conversely the BPRS-WR variates explained 54% of the PANSS-NS variance. AH three scales appear to measure a single general 'affective' component of the negative syndrome, while the PANSS-NS and the SANS also cover additional components which identify cognitive, anergic and social dimensions. This extra information is lost, however, if inappropriate data reduction and/or statistical analyses are used. The fact that the three instruments predicted the various dimensions of the negative syndrome to different degrees suggests that the best choice of a negative scale depends on the type of information required. Nevertheless, further examination of how negative symptom scales cover the multi-dimensional nature of the negative syndrome is required.

Adult↗
PubMed1999

Chromatin assembly: biochemical identities and genetic redundancy.

Investigations on chromatin assembly in vitro implicate chromatin assembly factor 1 (CAF1) as a chaperone for histones H3/H4 and nucleosome assembly protein 1 (NAP1) as a chaperone for histones H2A/H2B. Deletion analysis of CAF1 in vivo suggests multiple redundant pathways for deposition of the histones. Histone deposition requires acetylation of the amino-terminal tails and analysis of mutants suggests a specific but redundant role for acetylation of the tails in assembly. Furthermore, studies on the HAT1 acetyltransferase raise the possibility that acetylation of histones occurs following their transport into the nucleus but prior to their deposition onto DNA. Identification of the factors involved in the redundant pathways of assembly is awaited.

Acetylation↗