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PubMed1999

Functional magnetic resonance imaging of neural activity related to orthographic, phonological, and lexico-semantic judgments of visually presented characters and words.

Functional magnetic resonance imaging was used to investigate neural activity during the judgment of visual stimuli in two groups of experiments using seven and five normal subjects. The subjects were given tasks designed differentially to involve orthographic (more generally, visual form), phonological, and lexico-semantic processes. These tasks included the judgments of whether a line was horizontal, whether a pseudocharacter or pseudocharacter string included a horizontal line, whether a Japanese katakana (phonogram) character or character string included a certain vowel, or whether a character string was meaningful (noun or verb) or meaningless. Neural activity related to the visual form process was commonly observed during judgments of both single real-characters and single pseudocharacters in lateral extrastriate visual cortex, the posterior ventral or medial occipito-temporal area, and the posterior inferior temporal area of both hemispheres. In contrast, left-lateralized activation was observed in the latter two areas during judgments of real- and pseudo-character strings. These results show that there is no katakana "word form center" whose activity is specific to real words. Activation related to the phonological process was observed, in Broca's area, the insula, the supramarginal gyrus, and the posterior superior temporal area, with greater activation in the left hemisphere. These activation foci for visual form and phonological processes of katakana also were reported for the English alphabet in previous studies. The present activation showed no additional areas for contrasts of noun judgment with other conditions and was similar between noun and verb judgment tasks, suggesting two possibilities: no strong semantic activation was produced, or the semantic process shared activation foci with the phonological process.

Adult↗

PubMed2000

Genotype, phenotype, and developmental biology of molar tooth characters.

Primate molar shapes reflect developmental and ecological processes. Development may constrain as well as facilitate evolution of new tooth shapes, affecting how reliable dental characters are in phylogenetic studies. Much of the genetic machinery of development uses the same genes among different organs, including teeth, limbs, and feathers. Furthermore, within a tooth, the development of individual cusps repeatedly uses the same set of developmental genes, forming a "developmental module." The repeated activation of the developmental module can explain the cumulative variation in later-developing cusps. Therefore short, later-developing cusps may be evolvable but also more homoplastic. This patterning cascade mode of cusp development can be used to explain the variational properties of dental characters and character states related to cusp initiation. The developmental basis and variational properties of crown termination, cusp shape, and cusp configuration characters are currently less well understood. It is unlikely that there is a simple "gene to phenotype" map for dental characters. Rather, the whole cusp pattern is a product of a dynamic developmental program manifested in the activation of the developmental modules.

Animals↗

PubMed2000

Testing character correlation using pairwise comparisons on a phylogeny.

In comparative biology, pairwise comparisons of species or genes (terminal taxa) are used to detect character associations. For instance, if pairs of species contrasting in the state of a particular character are examined, the member of a pair with a particular state might be more likely than the other member to show a particular state in a second character. Pairs are chosen so as to be phylogenetically separate, that is, the path between members of a pair, along the branches of the tree, does not touch the path of any other pair. On a given phylogenetic tree, pairs must be chosen carefully to achieve the maximum possible number of pairs while maintaining phylogenetic separation. Many alternative sets of pairs may have this maximum number. Algorithms are developed that find all taxon pairings that maximize the number of pairs without constraint, or with the constraint that members of each pair have contrasting states in a binary character, or that they have contrasting states in two binary characters. The comparisons chosen by these algorithms, although phylogenetically separate on the tree, are not necessarily statistically independent.

Anatomy, Comparative↗

PubMed1994

Multiple origins of colonial green flagellates from unicells: evidence from molecular and organismal characters.

Phylogenetic hypotheses generated from cladistic analysis of organismal and molecular data are shown to be generally congruent and/or complementary for comparisons of unicellular and colonial green algae in the Chlorophyceae. Cladistic analysis of organismal character data corroborates the alliance of colonial Stephanosphaera with unicellular Haematococcus (Haematococcaceae sensu Smith), inferred from previous studies of nuclear-encoded rRNA sequence data. The organismal data also support monophyly of the colonial Volvocaceae (sensu Smith). Alliances of other unicellular taxa, including those ascribed to the "Euchlamydomonas" Hauptgruppe (sensu Ettl), are not resolved by organismal characters principally because the structure of the data is skewed to shared ancestral characters (symplesiomorphies) and unique characters (autapomorphies) which define individual taxa only. Reanalysis of rRNA sequence data, with additional sequence data for critical taxa, does not support monophyly of the colonial Volvocaceae (sensu Smith). However, these data are weak in the support of the alternate hypothesis of nonmonophyly. In contrast, relationships among most unicellular flagellates are unambiguously resolved by the molecular data. Although the failure of the sequence data to resolve relationships among colonial flagellates appears to be due to a sampling of conservative sequences, an ancient, rapid radiation event or taxon sampling bias may also be contributing to the ambiguity problem. Results from analysis of a combined data set (organismal and molecular) are generally consistent with the inferences of the organismal character data regarding the colonial flagellates and are also consistent with the inferences of the sequence data regarding the unicellular taxa.

Animals↗

PubMed1984

Coevolution of functionally constrained characters: prerequisites for adaptive versatility.

One of the major problems of organismic evolution theory is to explain how complex organisms were able to evolve by random mutations in spite of the severe functional constraints that canalize their route of change. The problem is discussed on the basis of a quantitative genetic model. How the degree of genetic variation influences the adaptation speed of functionally coupled but genetically uncorrelated characters is examined. It was found, that if more than three independent characters contribute to the variation of a functionally constrained system, optimal degrees of genetic variation exist. Higher degrees of variation lead to decreasing adaptation rates. Conversely, functional constraints do not limit the degree of adaptely reasonable genetic variability as long as the number of independent characters is not higher than three. The conclusion is drawn that there is no need to develop a genetic correlation between functionally coupled characters as long as not many more than three characters are integrated into a functional system. This explains the fact that there is no genetic coupling between the inherited signal sender and receiver mechanisms in orthopterians, even though there is a strong functional coupling between them.

Adaptation, Biological↗

PubMed2004

Orthographic and phonological processing of Chinese characters: an fMRI study.

The present study used functional magnetic resonance imaging (fMRI) to investigate the neural mechanisms underlying the orthographic and phonological processing of Chinese characters. Four tasks were devised, including one homophone judgment and three physical judgments of characters, pseudo-characters, and Korean-like nonsense figures. While the left occipitotemporal region, left dorsal processing stream, and right middle frontal gyrus constitute a network for orthographic processing, the left premotor gyrus, left middle/inferior frontal gyrus, supplementary motor area (SMA), and the left temporoparietal region work in concert for phonological processing. The ventral part of the left inferior frontal cortex responds specifically to the character stimuli, suggesting a general lexical processing role for this region for linguistic material. The stronger activation of the dorsal visual stream by Chinese homophone judgment pinpoints a tight coupling between phonological representation of Chinese characters and corresponding orthographic percepts. The concomitant engagement of sets of regions for different levels of Chinese orthographic and phonological processing is consistent with the notion of distributed parallel processing.

Adult↗

PubMed2005

Phylogeny of the ectomycorrhizal mushroom genus Alnicola (Basidiomycota, Cortinariaceae) based on rDNA sequences with special emphasis on host specificity and morphological characters.

Alnicola (=Naucoria, pro parte) is a mushroom genus of strictly temperate, obligately ectomycorrhizal species, traditionally included in the family Cortinariaceae. Most Alnicola spp. are primarily host specific on Alnus, although a few are mycobionts of Salix or other hosts. The different species of Alnicola exhibit unique morphological (cystidia, pileipellis) and cytological (dikaryotic or monokaryotic hyphae) characters. This makes the genus Alnicola of particular interest for studying the evolution of host specificity and morphological characters in ectomycorrhizal basidiomycetes. We used a combination of classical morphological and phylogenetic methods (rDNA ITS and LSU sequences) to address the following questions: (i) Is Alnicola monophyletic? And (ii) Are characters like host specificity or microscopical structures synapomorphic for certain clades? The study included nearly all currently known European Alnicola sp. Our results demonstrated that, on one hand, the genus Alnicola is polyphyletic, with sistergroup relationships to Hebeloma, Anamika or the clades /Hymenogaster I and /Hymenogaster II. On the other hand, Alnicola splits into three well-supported clades corresponding to the sections Alnicola, Submelinoides, and Salicicolae. The strict host-specificity to Alnus is a derived character and has occurred at least twice. The following morphological characters are synapomorphic for defined clades: the spindle-shaped hymenial cystidia for sect. Alnicola, the hymeniform pileipellis for sect. Submelinoides, and monocaryotic/clampless hyphae for sect. Salicicolae and its sistergroup /Hymenogaster II. As a taxonomical consequence, polyphyly of Alnicola implies that the sects. Submelinoides and Salicicolae need to be segregated from Alnicola.

Basidiomycota↗

PubMed1997

Mirror writing in right-handers and in left-handers: a study using Chinese characters.

The mechanism of mirror writing was investigated using legal Chinese characters and illegal pseudocharacters. It was found from the results of right-handers in experiment 1 that the performance of normal writing and mirror writing for legal characters was better than that of normal writing and mirror writing for pseudocharacters. A reasonable explanation for this character-superiority effect is that normal engrams and mirror engrams exist only for legal characters but not for pseudocharacters. Further analysis revealed that the character-superiority effect took place in normal writing only when the right hand was used and the same effect was observed in mirror writing only when the left hand was used. It seemed that the normal engrams used in normal writing were stored in the left hemisphere while the mirror engrams used in mirror writing were stored in the right hemisphere. The results in experiment 2 from the left-handers showed the similar pattern as that of the right-handers. The mirror-engram hypothesis seems to be the best mechanism to account for the performance difference of right hand and left hand in mirror writing.

Adult↗

PubMed1998

Functional magnetic resonance imaging during recognition of written words: Chinese characters for concrete objects versus abstract concepts.

An attempt was made to apply functional magnetic resonance imaging (fMRI) to reveal cortical areas activated upon presentation of two groups of Chinese characters in six normal right-handed, male, Japanese subjects. Presentation of the characters representing 'abstract concepts' activated the bilateral occipital region without a significant difference between the bilateral occipital and temporal regions. Presentation of the characters representing 'concrete objects' resulted in significantly stronger activation in the left occipital and temporal regions. These results suggest that recognition of concrete characters involves a stronger initial process in the left occipital temporal cortices than recognition of abstract characters.

Adult↗

PubMed1998

Functional magnetic resonance imaging during recognition of written words: Chinese characters for concrete objects versus abstract concepts.

Adult↗

PubMed2002

Amino acid vs. nucleotide characters: challenging preconceived notions.

The 567-terminal analysis of atpB, rbcL, and 18S rDNA was used as an empirical example to test the use of amino acid vs. nucleotide characters for protein-coding genes at deeper taxonomic levels. Nucleotides for atpB and rbcL had 6.5 times the amount of possible synapomorphy as amino acids. Based on parsimony analyses with unordered character states, nucleotides outperformed amino acids for all three measures of phylogenetic signal used (resolution, branch support, and congruence with independent evidence). The nucleotide tree was much more resolved than the amino acid tree, for both large and small clades. Nearly twice the percentage of well-supported clades resolved in the 18S rDNA tree were resolved using nucleotides (91.8%) relative to amino acids (49.2%). The well-supported clades resolved by both character types were much better supported by nucleotides (98.7% vs. 83.8% average jackknife support). The faster evolving nucleotides with a smaller average character-state space outperformed the slower evolving amino acids with a larger average character-state space. Nucleotides outperformed amino acids even with 90% of the terminals deleted. The lack of resolution on the amino acid trees appears to be caused by a lack of congruence among the amino acids, not a lack of replacement substitutions.

Amino Acids↗

PubMed2002

Levels of processing and phonological priming in Chinese character completion tests.

This study investigated the level of processing (LoP) effect in the Chinese character completion task. Stem cues, either graphemically or phonetically related to a target character, were used to generate two different kinds of perceptual tests. By giving participants either direct or indirect instructions, the character completion tests could be either an explicit or an implicit memory test. For the implicit test, LoP effects were not found between Read and Generation conditions, whereas the Physical conditioni did not produce priming. In addition, no priming was found when participants received graphemic cues during the test. For the explicit test, on the other hand, a standard pattern of LoP effects was found between the Physical, Read, and Generation conditions. Results are discussed in terms of the importance of lexical access for character completion tests and the role of phonology in processing Chinese characters.

Cognition↗

PubMed1989

Illusory conjunctions in the perception of Chinese characters.

A Chinese compound character consists of a radical component and a stem component. When compound characters were presented briefly, Ss often reported seeing illusory recombinations of radicals and stems. A series of 5 experiments suggested that the probability of seeing illusory characters is not under the direct influence of lexicality, pronounceability, or character frequency, but depends on 2 factors: (1) familiarity defined in terms of unit frequency, i.e., the frequency of occurrence of a unit either by itself or as part of a larger unit, and (2) the context-dependent perceptual distinctiveness of the components of a given character. It is suggested that the seemingly unreliable lexicality effect obtained in English studies may be reduced to a familiarity effect, and that what McClelland and Mozer (1986) referred to as the surround-similarity effect may be better characterized as an effect of perceptual distinctiveness.

Adult↗

PubMed1997

The role of component function in visual recognition of Chinese characters.

M. Taft and X. Zhu (1997) reported that character decision latencies to real Chinese characters containing components that entered into many combinations were faster than decision latencies to characters with components that entered into only a small number of combinations. However, this effect was restricted to components that appeared on the right side of Chinese characters. In written Chinese, phonetic components tend to appear on the right, and semantic components tend to appear on the left. Therefore, in Taft and Zhu's study, there was the possibility of a confound between position (left vs. right) and function (semantic vs. phonetic). Results of the present experiment show combinability effects for components with semantic and with phonetic functions. Counter to the claim by Taft and Zhu that component frequency effects are constrained by position, when component function was considered, character decision latencies varied with component frequency but not reliably with position.

Adult↗

PubMed1993

Laboratory and natural heritabilities of male courtship song characters in Drosophila montana and D. littoralis.

We estimated heritabilities for several male courtship song characters in two Drosophila species using father-son regression under conditions where both fathers and sons had been raised in the laboratory. In D. montana the heritabilities of song characters were rather high (-0.23 to 0.80) and in most cases significant. In D. littoralis the heritabilities of song characters were generally lower (-0.33 to 0.18), and none of them was significantly larger than zero. We also estimated heritabilities regressing characters of wild-caught fathers with those of their laboratory reared sons, and used the method employed by Riska et al. to estimate the lower bound of heritabilities in nature. In D. montana most and in D. littoralis all of the across-environment heritabilities were non-significant (-0.15 to 0.43 and -0.04 to 0.15, respectively), and in some cases the across-environment heritabilities were significantly lower than the heritabilities measured under laboratory conditions. The low across-environment heritabilities appeared to be due to larger phenotypic variability of song characters in the field and in some cases also due to genotype-environment interactions.

Animals↗

PubMed2004

Nonindependence of mammalian dental characters.

Studies of mammalian evolution frequently use data derived from the dentition. Dental characters are particularly central for inferring phylogenetic relationships of fossil taxa, of which teeth are often the only recovered part. The use of different aspects of dental morphology as phylogenetic signals implies the independence of dental characters from each other. Here we report, however, that, at least developmentally, most dental characters may be nonindependent. We investigated how three different levels of the cell signalling protein ectodysplasin (Eda) changed dental characters in mouse. We found that with increasing expression levels of this one gene, the number of cusps increases, cusp shapes and positions change, longitudinal crests form, and number of teeth increases. The consistent modification of characters related to lateral placement of cusps can be traced to a small difference in the formation of an early signalling centre at the onset of tooth crown formation. Our results suggest that most aspects of tooth shape have the developmental potential for correlated changes during evolution which may, if not taken into account, obscure phylogenetic history.

Animals↗

PubMed1998

Intraspecific variation in sperm size characters.

Interspecific variation in quantitative characters of sperm is considerable and can sometimes be related to aspects of sperm competition. In contrast, continuous intraspecific variation is often ignored; for example, many studies concentrate on measuring a species-typical sperm size. However, statistically significant variation amongst males in a variety of sperm size characters, particularly total length and a number of head characters, has been reported in at least 13 species. Furthermore, sperm size has been shown to influence the outcomes of processes involved in sperm competition in two species, with larger sperm being more successful in both cases. It is suggested here that intraspecific variation may be a widespread phenomena, further examination of which could contribute considerably to our understanding of sperm evolution. Size differences between the sperm of competing males could be used in controlled matings to investigate the fates of sperm within female tracts and storage organs, but care should be taken that size characters may not be neutral markers. Furthermore, the genetic determination of sperm size is considerable (h2 = 0.56-0.92 for total length and a number of head characters) and determinants are at least sometimes sex-linked, with the result that particular care must go into experimental design if genetic effects are to be fully elucidated. Studies combining genetical and behavioural effects of intraspecific variation in sperm morphology should be particularly rewarding.

Animals↗

PubMed2005

Integration of morphological data sets for phylogenetic analysis of Amniota: the importance of integumentary characters and increased taxonomic sampling.

Several mutually exclusive hypotheses have been advanced to explain the phylogenetic position of turtles among amniotes. Traditional morphology-based analyses place turtles among extinct anapsids (reptiles with a solid skull roof), whereas more recent studies of both morphological and molecular data support an origin of turtles from within Diapsida (reptiles with a doubly fenestrated skull roof). Evaluation of these conflicting hypotheses has been hampered by nonoverlapping taxonomic samples and the exclusion of significant taxa from published analyses. Furthermore, although data from soft tissues and anatomical systems such as the integument may be particularly relevant to this problem, they are often excluded from large-scale analyses of morphological systematics. Here, conflicting hypotheses of turtle relationships are tested by (1) combining published data into a supermatrix of morphological characters to address issues of character conflict and missing data; (2) increasing taxonomic sampling by more than doubling the number of operational taxonomic units to test internal relationships within suprageneric ingroup taxa; and (3) increasing character sampling by approximately 25% by adding new data on the osteology and histology of the integument, an anatomical system that has been historically underrepresented in morphological systematics. The morphological data set assembled here represents the largest yet compiled for Amniota. Reevaluation of character data from prior studies of amniote phylogeny favors the hypothesis that turtles indeed have diapsid affinities. Addition of new ingroup taxa alone leads to a decrease in overall phylogenetic resolution, indicating that existing characters used for amniote phylogeny are insufficient to explain the evolution of more highly nested taxa. Incorporation of new data from the soft and osseous components of the integument, however, helps resolve relationships among both basal and highly nested amniote taxa. Analysis of a data set compiled from published sources and data original to this study supports monophyly of Amniota, Synapsida, Reptilia, Parareptilia, Eureptilia, Eosuchia, Diapsida, Neodiapsida, Sauria, Lepidosauria, and Archosauriformes, as well as several more highly nested divisions within the latter two clades. Turtles are here resolved as the sister taxon to a monophyletic Lepidosauria (squamates + Sphenodon), a novel phylogenetic position that nevertheless is consistent with recent molecular and morphological studies that have hypothesized diapsid affinities for this clade.

Animals↗