Genome Sequencing and Transcriptome Analysis of the Hop Downy Mildew Pathogen Pseudoperonospora humuli Reveal Species-Specific Genes for Molecular Detection

Pseudoperonospora humuli is an obligate oomycete pathogen of hop (Humulus lupulus) that causes downy mildew, an important disease in most production regions in the Northern Hemisphere. The pathogen can cause a systemic infection in hop, overwinter in the root system, and infect propagation material. Substantial yield loss may occur owing to P. humuli infection of strobiles (seed cones), shoots, and cone-bearing branches. Fungicide application and cultural practices are the primary methods to manage hop downy mildew. However, effective, sustainable, and cost-effective management of downy mildew can be improved by developing early detection systems to inform on disease risk and timely fungicide application. However, no species-specific diagnostic assays or genomic resources are available for P. humuli. The genome of the P. humuli OR502AA isolate was partially sequenced using Illumina technology and assembled with ABySS. The assembly had a minimum scaffold length of 500 bp and an N50 (median scaffold length of the assembled genome) of 19.2 kbp. A total number of 18,656 genes were identified using MAKER standard gene predictions. Additionally, transcriptome assemblies were generated using RNA-seq and Trinity for seven additional P. humuli isolates. Bioinformatics analyses of next generation sequencing reads of P. humuli and P. cubensis (a closely related sister species) identified 242 candidate species-specific P. humuli genes that could be used as diagnostic molecular markers. These candidate genes were validated using polymerase chain reaction against a diverse collection of isolates from P. humuli, P. cubensis, and other oomycetes. Overall, four diagnostic markers were found to be uniquely present in P. humuli. These candidate markers identified through comparative genomics can be used for pathogen diagnostics in propagation material, such as rhizomes and vegetative cuttings, or adapted for biosurveillance of airborne sporangia, an important source of inoculum in hop downy mildew epidemics.

Mitochondrial haplotype analysis for differentiation of isolates of Phytophthora cinnamomi

Although Phytophthora cinnamomi is heterothallic, there are few instances of successful crossing in laboratory experiments, and analysis of field populations indicates a clonally reproducing population. In the absence of sexual recombination, the ability to monitor mitochondrial haplotypes may provide an additional tool for identification of clonal isolates and analysis of population structure. To determine mitochondrial haplotypes for this species, seven mitochondrial loci spanning a total of 6,961 bp were sequenced for 62 isolates representing a geographically diverse collection of isolates with A1 and A2 mating type. Three of the regions were primarily intergenic regions between trnG and rns, rns and nad3, and nad6 and cox1, while the remaining loci spanned cox2, nad9, rps10, and secY coding regions and some of the flanking spacer regions. In total, 45 mitochondrial haplotypes were identified (75% of the total isolates examined) with differences due to single-nucleotide polymorphisms (SNPs, totaling 152 bp) and length mutations (17 indels >2 bp representing a total of 910 bp in length). SNPs were the predominate mutation in the four coding regions and their flanking intergenic regions, while both SNPs and length mutations were observed in the three primarily intergenic regions. Some of the length mutations in these regions were due to addition or loss of unique sequences while others were due to variable numbers of subrepeats (in the trnG-rns region, there were 3 to 12 copies of a 24-bp subrepeat sequence that differentiated 17 haplotypes). Network analysis of the haplotypes identified eight primary clades, with the most divergent clade representing primarily A1 isolates collected from Papua New Guinea. The isolate grouping in the network corresponded to mating type and previously published isozyme classifications, with three exceptions: a haplotype representing an A1 mating type (H29) was placed well within the A2 mating type haplotype grouping, one haplotype (H26) had isolates with two isozyme classifications, and one isozyme group was represented on separate network clades, suggesting that recombination has occurred in the past. Among the 62 isolates examined, several examples were identified of isolates recovered from different geographic regions having the same mitochondrial haplotype, suggesting movement of isolates via plant material. Analysis of the data set to determine whether fewer loci could be sequenced to classify haplotypes indicated that the trnG-rns and rns-nad6 loci would classify 87% of the haplotypes identified in this study, while additional sequencing of the nad9 or secY loci would further differentiate the remaining six haplotypes. Based on conservation of gene order in Phytophthora spp., the trnG-rns locus should be useful for mitochondrial haplotype classification in other species, as should the cox2, nad9, rps10, and secY loci. However, the rns-nad3 and nad6-cox1 loci span regions that can have a different gene order in some Phytophthora spp.

Evaluation of molecular markers for Phytophthora ramorum detection and identification: testing for specificity using a standardized library of isolates

Given the importance of Phytophthora ramorum from a regulatory standpoint, it is imperative that molecular markers for pathogen detection are fully tested to evaluate their specificity in detection of the pathogen. In an effort to evaluate 11 reported diagnostic techniques, we assembled a standardized DNA library using accessions from the World Phytophthora Genetic Resource Collection for 315 isolates representing 60 described Phytophthora spp. as well as 11 taxonomically unclassified isolates. These were sent blind to collaborators in seven laboratories to evaluate published diagnostic procedures using conventional (based on internal transcribed spacer [ITS] and cytochrome oxidase gene [cox]1 and 2 spacer regions) and real-time polymerase chain reaction (based on ITS and cox1 and 2 spacer regions as well as beta-tubulin and elicitin genes). Single-strand conformation polymorphism (SSCP) analysis using an automated sequencer for data collection was also evaluated for identification of all species tested. In general, the procedures worked well, with varying levels of specificity observed among the different techniques. With few exceptions, all assays correctly identified all isolates of P. ramorum and low levels of false positives were observed for the mitochondrial cox spacer markers and most of the real-time assays based on nuclear markers (diagnostic specificity between 96.9 and 100%). The highest level of false positives was obtained with the conventional nested ITS procedure; however, this technique is not stand-alone and is used in conjunction with two other assays for diagnostic purposes. The results indicated that using multiple assays improved the accuracy of the results compared with looking at a single assay alone, in particular when the markers represented different genetic loci. The SSCP procedure accurately identified P. ramorum and was helpful in classification of a number of isolates to a species level. With one exception, all procedures accurately identified P. ramorum in blind evaluations of 60 field samples that included examples of plant infection by 11 other Phytophthora spp. The SSCP analysis identified eight of these species, with three identified to a species group.

Management of Soilborne Diseases in Strawberry Using Vegetable Rotations

The influence of crop rotation on soilborne diseases and yield of strawberry (Fragaria × ananassa) was determined at a site infested with Verticillium dahliae microsclerotia and at another with no known history of V. dahliae infestation during 1997 to 2000. The rotations studied at the V. dahliae-infested site were (i) broccoli-broccoli-strawberry, (ii) Brussels sprouts-strawberry, and (iii) lettuce-lettuce-strawberry; the treatments at the site with no history of V. dahliae were (i) broccoli-broccoli-strawberry, (ii) cauliflower-cauliflower-strawberry, and (iii) lettuce-lettuce-strawberry. The effects of rotation on V. dahliae and Pythium populations, strawberry vigor, Verticillium wilt severity, and strawberry fruit yield were compared with a standard methyl bromide + chloropicrin fumigated control treatment at both sites. Rotations did not alter total population levels of Pythium spp. at either study site. However, V. dahliae microsclerotia were significantly reduced with br occoli and Brussels sprouts rotations compared with lettuce rotations at the V. dahliae-infested site. Reduced propagules led to lower Verticillium wilt severity on strawberry plants in the broccoli and Brussels sprouts rotations than in lettuce-rotated plots. Strawberry vigor and fruit yield were significantly lower in lettuce-rotated plots than in broccoli- and Brussels sprouts-rotated plots. Despite no detectable microsclerotia at the other site, strawberry vigor and fruit yield were greatest in plots rotated with broccoli, intermediate with cauliflower, and lowest with lettuce. None of the rotation treatments were better than the fumigated control for all variables measured. In the absence of fumigation, rotation with broccoli and Brussels sprouts is an effective cultural practice for managing Verticillium wilt in strawberry production; whereas, in fields with no detectable V. dahliae, broccoli is also a feasible rotational crop that enhances strawberry growth and yield. According to a cost-benefit analysis, the broccoli-strawberry rotation system could be an economically viable option provided growers are able to alternate years for strawberry cultivation.

Molecular Detection of Phytophthora ramorum by Real-Time Polymerase Chain Reaction Using TaqMan, SYBR Green, and Molecular Beacons

ABSTRACT Sudden oak death, caused by Phytophthora ramorum, is a severe disease that affects many species of trees and shrubs. This pathogen is spreading rapidly and quarantine measures are currently in place to prevent dissemination to areas that were previously free of the pathogen. Molecular assays that rapidly detect and identify P. ramorum frequently fail to reliably distinguish between P. ramorum and closely related species. To overcome this problem and to provide additional assays to increase confidence, internal transcribed spacer (ITS), beta-tubulin, and elicitin gene regions were sequenced and searched for polymorphisms in a collection of Phytophthora spp. Three different reporter technologies were compared: molecular beacons, TaqMan, and SYBR Green. The assays differentiated P. ramorum from the 65 species of Phytophthora tested. The assays developed were also used with DNA extracts from 48 infected and uninfected plant samples. All environmental samples from which P. ramorum was isolated by PARP-V8 were detected using all three real-time PCR assays. However, 24% of the samples yielded positive real-time PCR assays but no P. ramorum cultures, but sequence analysis of the coxI and II spacer region confirmed the presence of the pathogen in most samples. The assays based on detection of the ITS and elicitin regions using TaqMan tended to have lower cycle threshold values than those using beta-tubulin and seemed to be more sensitive.

Genetic and Morphological Diversity of Temperate and Tropical Isolates of Phytophthora capsici

ABSTRACT Phytophthora capsici is a diverse species causing disease on a broad range of both temperate and tropical plants. In this study, we used cultural characteristics, amplified fragment length polymorphism (AFLP), and DNA sequence analyses of the ribosomal internal transcribed spacer (ITS) region and mitochondrial cytochrome oxidase II (cox II) genes to characterize temperate and tropical isolates from a wide range of host species. All but one temperate isolate grew at 35 degrees C, while all tropical isolates did not. All but two tropical isolates formed chlamydospores, while temperate isolates did not. There was strong bootstrap support for separation of temperate and tropical isolates using AFLP analysis; however, the temperate isolates appeared as a subgroup within the observed variation of the tropical isolates. The majority of temperate isolates clustered within a single clade with low variation regardless of host or geographical origin, while the tropical isolates were more variable and grouped into three distinct clades. Two clades of tropical isolates grouped together and were affiliated closely with the temperate isolates, while the third tropical clade was more distantly related. Phylogenetic analysis of the ITS regions resulted in similar groupings and variation within and between the temperate and tropical isolates as with the AFLP results. Sequence divergence among isolates and clades was low, with more variation within the tropical isolates than within the temperate isolates. Analysis of other species revealed shorter branch lengths separating temperate and tropical isolates than were observed in comparisons among other phylogenetically closely related species in the genus. Analysis of cox II sequence data was less clear. Although the temperate and tropical isolates grouped together apart from other species, there was no bootstrap support for separating these isolates. Restriction fragment length polymorphism (RFLP) analysis of the ITS regions separated the temperate and tropical isolates, as in the AFLP and ITS phylogenetic analyses. However, RFLP analysis of the cox I and II gene cluster did not distinguish between temperate and tropical isolates. The differences in grouping of isolates in these two RFLP studies should be helpful in identifying isolate subgroups. Our data do not fully clarify whether or not temperate and tropical isolates should be separated into different species. The available worldwide data are incomplete and the full range of variation in the species is not yet known. We suggest refraining from using the epithet P. tropicalis until more data are available.

Biological approaches for control of root pathogens of strawberry

ABSTRACT Soil fumigation with methyl bromide plus chloropicrin is used as a preplant treatment to control a broad range of pathogens in high-value annual crop production systems. In California, fumigation is used on approximately 10,125 ha of strawberry production to control pathogens ranging from Verticillium dahliae to root pruning pathogens such as Pythium, Rhizoctonia, or Cylindrocarpon spp. In addition to pathogen control, fumigation also causes an enhanced growth response of the plant and reduces weed pressure. The development of successful, long-term cost effective biocontrol strategies most likely will require the development of an integrated systems approach that incorporates diverse aspects of the crop production system. Although application of single microbial inoculants may provide some level of control for specific production problems, it will be a challenge to provide the broad spectrum of activity needed in production fields.

Strategies used in feigning hearing loss

Thirty unsophisticated participants with normal hearing were paid to simulate a hearing loss according to their success in "deceiving" the examiner. The behaviors that these "malingerers" manifested are described. A post-examination interview revealed the strategies used by these participants, which may reflect those strategies used by patients who truly attempt to feign a hearing loss.

Insert earphone depth and the occlusion effect

Twenty individuals were tested to determine the occlusion effect caused by supraaural earphones and by insert earphones with shallow and deep insertion of its foam eartip. The bone-conduction oscillator was placed both on the forehead and the mastoid. It was concluded that using deeply inserted earphones is the most practical way in which to carry out clinical bone-conduction measurements.

The question of phonetic balance in word recognition testing

Twenty subjects with normal hearing and 15 subjects with mild-to-moderate sensorineural hearing losses were tested with eight lists of words using monosyllabic pronunciation to determine word recognition scores. Four of the lists were taken from Northwestern University Test No. 6 and four were simply made up by randomly selecting words from a dictionary. All of the word lists were used to determine performance-intensity functions. No clinically meaningful differences were observed among the lists.

Rhizoctonia spp. Recovered from Strawberry Roots in Central Coastal California

ABSTRACT Rhizoctonia spp. were commonly recovered from the roots of strawberry plants growing in nonfumigated soil in the central coastal region of California. With the exception of one multinucleate isolate of R. solani (frequency of recovery of 0.8%), all other isolates were binucleate and were in anastomosis groups (AG) A, G, or I. AGs-A and -I were recovered from all five collection sites, whereas AG-G was recovered from only two sites. AG-A was the most commonly isolated AG, followed by AGs-I and -G. Similar levels of virulence were observed among the different AGs, but differences in virulence were observed among isolates in the same AG. Evaluating anastomosis grouping by pairing isolates recovered from strawberry with known tester isolates did not always yield a positive anastomosis reaction, even though both isolates anastomosed with other members of the same AG. Subsequent investigations with multiple isolates in the same AG from the same collection location confirmed that there was a lack of anastomosis or weak anastomosis reactions for some combinations of pairings, highlighting the need for to use multiple tester isolates or molecular techniques for AG determination. Restriction fragment length polymorphism (RFLP) analysis of a polymerase chain reaction-amplified region of the rDNA was effective for differentiating AGs. Sixteen RFLP groups were observed after cluster analysis with data for the size of the amplified products and fragment sizes after digestion with four restriction enzymes. Although each AG had isolates in multiple RFLP groups, any one individual RFLP group contained isolates of only a single AG. There was no consistent correlation between RFLP group and location of isolate collection.

Reconsidering the limits of normal hearing

A proposal is made that 15 dB HL, rather than 25 dB HL, be considered the upper limit of normal hearing sensitivity. This recommendation is based on an explanation of the change from an earlier philosophy and the fact that so many people with hearing levels that average less than 25 dB HL consider themselves to have hearing difficulty. Such reclassification of people with slight to mild hearing losses would dignify their clinical complaints and aid in counseling that would assist them with their hearing difficulties.

The CON-SOT-LOT test for nonorganic hearing loss

The efficacy of a screening procedure for detecting nonorganic hearing loss using standard audiometric instrumentation was examined. Thirty normal-hearing subjects' responses to continuous and standard and lengthened off-time pulsed tones, using an ascending-descending method, were compared. Subjects were asked to respond to test stimuli in normal-hearing and simulated hearing loss conditions. Data show that there are clinical and statistical differences between subjects' response patterns in the normal-hearing condition as compared to the feigned hearing loss condition. The procedure is offered as a simple method of screening for nonorganic hearing loss.

Quantifying air-conducted acoustic radiation from the bone-conduction vibrator

Sound pressure levels in the external auditory canals of 50 subjects were measured at 2000 and 4000 Hz with a bone-conduction vibrator on the forehead, the mastoid ipsilateral to the probe microphone, and the mastoid contralateral to the probe microphone. A plug was placed in the external auditory canal to minimize sound pressure levels in the external auditory canal produced by the osseotympanic mode of bone conduction. Results suggest that clinically significant false air-bone gaps (greater than 10 dB) due to acoustic radiation into the concha from the bone-conduction vibrator are most likely to occur at 4000 Hz when the bone-conduction vibrator is placed on the mastoid of the test ear. To minimize the possible confounding effects of acoustic radiation, the bone-conduction vibrator may be placed on the forehead or the mastoid contralateral to the test ear while masking the nontest ear.

Seventh survey of audiometric practices in the United States

A 5-page questionnaire was sent to 500 audiologists who were randomly selected from the directory of members of the American Academy of Audiology to assess the clinical practices most commonly used by certified audiologists in the United States. Survey content was limited to only those practices and procedures routinely used by audiologists across the nation. The current results were then compared to those obtained in similar studies conducted in 1971, 1972, 1978, 1985, 1989, and 1994 to determine which clinical procedures are being retained, modified, or replaced.

Auditory and tactile bone-conduction thresholds using three different oscillators

Determination of tactile bone-conduction (BC) thresholds is essential to provide proper diagnosis of individuals with profound hearing loss. In this study, auditory and tactile BC thresholds were compared using three oscillators: the Radioear B-70-A, B-71, and B-72 with mastoid and forehead placement. Subjects included 12 adults with normal hearing (to establish auditory thresholds) and 12 adults with profound sensorineural hearing loss (to establish tactile thresholds). All 24 subjects were tested at octave intervals from 250 through 4000 Hz. As demonstrated in previous studies, tactile thresholds were lower for the low frequencies. Some differences in tactile thresholds were evinced as a function of different oscillators. One fact that emerged from this study is the lower tactile threshold with forehead placement as compared to the mastoid. While ostensibly a disadvantage to forehead BC testing, there are some clinical advantages to be gleaned from this discovery.

Selection of Drug-Tolerant Strains of Pythium sylvaticum Using Sublethal Enrichment

ABSTRACT Sublethal enrichment was used to generate mutants of Pythium sylvaticum tolerant to kanamycin and tetracycline. Kanamycin tolerance was readily generated, and mutants had growth rates similar to wild-type isolates at antibiotic concentrations lethal to wild-type isolates. Based on crosses between wild-type and mutant isolates, two types of inheritance of tolerance were identified. A high level of kanamycin tolerance was inherited in progeny only when the maternal parent was drug tolerant and was correlated with the inheritance of maternal mitochondrial DNA. A lower level of tolerance was observed in some progeny when the paternal parent was tolerant to the antibiotic and, based on the lack of inheritance of paternal mitochondrial DNA, was presumably nuclear-encoded. Selection of mutants tolerant to tetracycline took longer to generate than kanamycin-tolerant mutants. Based on crosses between tolerant and wild-type parents, tolerance to tetracycline was nuclear-encoded. Tolerance to both antibiotics was stable, with cultures retaining tolerance following repeated transfers on nonamended medium and after storage for 7 years.

Audiologists' professional satisfaction

This study was primarily designed to explore the job satisfaction of audiologists in the United States. A total of 285 audiologists completed background questions, rated statements, and answered questions about their job satisfaction. Through the use of multiple regression analyses, six statements were identified as being statistically significant in predicting job satisfaction. The most important factor was in the category of challenge.

Linear mitochondrial genome organization in vivo in the genus Pythium

Pulsed-field gel electrophoresis (PFGE) of isolates of Pythium oligandrum with linear mitochondrial genomes revealed a distinct band in ethidium bromide-stained gels similar in size to values estimated by restriction mapping of mitochondrial DNA (mtDNA). Southern analysis confirmed that these bands were mtDNA and indicated that linear genomes were present in unit-length size as well as multimers. Isolates of this species with circular mtDNA restriction maps also had low levels of linear mono- and multimers visualized by Southern analysis of PFGE gels. Examination of 17 additional species revealed similar results; three species had distinct linear mtDNA bands in ethidium bromide-stained gels while the remainder had linear mono- and multi-mers in lower amounts detected only by Southern analysis. Sequence analysis of an isolate of P. oligandrum with a primarily circular mitochondrial genomic map and a low amount of linear molecules revealed that the small unique region of the circular map (which corresponded to the terminal region of linear genomes) was flanked by palindromic intrastrand complementary sequences separated by a unique 194-bp sequence. Sequences with similarity to ATPase9 coding regions from other organisms were located adjacent to this region. Sequences with similarity to mitochondrial origins of replication and autonomously replicating sequences were also located in this region: their potential involvement in the generation of linear molecules is discussed.

Sound pressure in the external auditory canal during bone-conduction testing

Sound pressure levels (SPLs) were measured in the external auditory canals (EACs) of 16 subjects with normal hearing and normal middle ear immittance. SPLs were the result of bone-conduction (BC) stimulation at 500, 1000, 2000, and 4000 Hz, with the oscillator placed either on the forehead or on the mastoid process. At 1000, 2000, and 4000 Hz, significantly higher SPLs were measured when the head was stimulated from the mastoid than from the forehead. When SPLs were compared between right and left EACs, forehead placement of the oscillator produced no interaural differences, while mastoid placement resulted in significantly greater EAC SPLs ipsilateral to the oscillator at 2000 and 4000 Hz. We conclude that forehead placement of a BC vibrator may help to lessen the (unwanted) contribution of the EAC to measurements of hearing sensitivity by BC.

Professional attitudes regarding counseling of hearing-impaired adults

To determine contemporary thinking regarding initial counseling of hearing-impaired adults 500 questionnaires were mailed to otologists and otolaryngologists and 500 to clinical audiologists. Usable questionnaires total 136 for the former group and 266 for the latter. Some significant differences were found in the ways clinicians saw themselves as counselors and in the needs they perceived their patients as having. Respondents reported experiencing various methods of training and possessing diverse attitudes about the effectiveness of their preparation as counselors during their professional training.

Characterization of circular mitochondrial plasmids in three Pythium species

Four circular plasmids, with a monomer size ranging from 3.2 to 4.94 kb, have been identified in isolates of P. aphanidermatum (two different plasmids), P. torulosum, and an unidentified echinulate isolate. The mitochondrial location has been confirmed for three of the plasmids. Each fungal isolate contained a single plasmid, present in both monomeric and oligomeric forms; plasmid monomers were present as open circles and as supercoiled forms. Restriction maps of the plasmids were dissimilar. Hybridization studies using cloned plasmids revealed no DNA sequence similarity among the different plasmids or between the plasmids and the nuclear or mitochondrial genome of the isolates from which they were recovered. Hybridization of labeled plasmid DNA to Northern transfers of mitochondrial RNA for two isolates indicate that what appears to be the predominant RNA transcript is unit length in size. For three isolates, the plasmid was retained following subculturing and was present in all asexual and sexual single-spore progeny evaluated. For one isolate of P. aphanidermatum the plasmid was unstable and was lost during subculturing.

Insert earphones for speech recognition testing

Performance-intensity functions for PB word lists were run on 19 normal-hearing subjects and 15 subjects with sensorineural hearing losses. Comparisons were made between standard supra-aural earphones (TDH-49P) and insert phones (ER-3A). Results showed that, at least for the higher sensation levels where word recognition tests are usually performed, the phones may be used interchangeably. Using insert earphones for word recognition tests can have several beneficial effects with respect to cross hearing and masking.

Vegetative compatibility within Fusarium oxysporum f.sp. niveum and its relationship to virulence, aggressiveness, and race

Over 250 isolates of Fusarium oxysporum collected from infected watermelon plants and soil samples from a pathogen-infested field, as well as known isolates of F. oxysporum f. sp. niveum imported from various locations around the world, were tested for pathogenicity on watermelon and used to determine vegetative compatibility groups (VCGs) within F. oxysporum f. sp. niveum. Vegetative compatibility was assessed on the basis of heterokaryon formation among nitrate-nonutilizing mutants. Race determinations were made by screening isolates on six different watermelon cultivars of varying resistance. All isolates of F. oxysporum f. sp. niveum belonged to one of three distinct VCGs, and were incompatible with isolates that were not pathogenic on watermelon. Isolates of F. oxysporum f. sp. niveum were subdivided into two races and there was a direct relationship between VCG and race. VCG 0080 consisted of race 1 isolates from five states of the United States, Taiwan, and Australia. VCG 0081 consisted solely of race 1 isolates from Florida. VCG 0082 was comprised solely of race 2 isolates, all of which were capable of causing severe wilt on all cultivars tested. Numerous Florida isolates were compatible with race 2 isolates from Texas and demonstrated comparable virulence on all cultivars, confirming the presence of race 2 in Florida. With F. oxysporum f. sp. niveum, vegetative compatibility can be utilized as an alternative or collaborative method to distinguish pathogenic from nonpathogenic strains of F. oxysporum and to differentiate subforma specialis virulence characteristics. Key words: fusarium wilt, nit mutants, watermelon.

Speech reception thresholds using conventional vs high-frequency spondees in normals and in subjects with marked high-frequency sensorineural loss

Spondee threshold (ST) estimates were obtained on 20 normal-hearing adults and 15 adults with high-frequency sensorineural hearing losses sloping off above 500 c/s at about 15-20 db/oct. Stimuli consisted of tapes of a woman's voice speaking permuted lists of 9 conventional (broadband) spondees and of 10 high-frequency-emphasis spondees developed especially for this research using a discrete-frequency analysis. For normals, the correspondence was good between the 3-frequency (.5, 1, 2 kc/s) PTA vs either list. However, for the sensorineural Ss, the mean ST for the conventional spondees was better matched to the 2-frequency PTA (av. of 2 best of .5, 1, 2 kc/s), while the high-frequency-emphasis list STs were better matched to the 3-frequency PTA. It was suggested that high-frequency-emphasis STs be used with such sloping losses and that ST-PTA reliability checks for such Ss be comparisons using a +/- 5-db criterion comparing high-frequency-emphasis STs with 3-frequency PTA. If conventional STs are collected, they should with such Ss be compared to the individual's 2-frequency PTA.

A children's Spanish word discrimination test for non-Spanish-speaking clinicians

A picture-pointing speech discrimination test which can be efficiently administered by English-speaking clinicians to Spanish-speaking children was developed. The test consists of four lists of 25 bisyllabic words. Two syllable words were chosen as stimuli instead of the traditional monosyllabic words because of the limited number of concrete monosyllabic words in Spanish. These words were recorded in Spanish on the first channel of an audio tape and in English on the second channel. The purpose of this dual recording was to present the Spanish stimuli to the subjects at the same time the clinicians monitored the appropriateness of responses in English.

Syllabic stress (trochaic vs. spondaic) and speech thresholds in normal and hearing-impaired children

Speech thresholds for 6 common two-syllable words on tape with either trochaic (natural) or spondaic stress were collected from children aged 3.5-6.5 yrs, audiometrically grouped as normal-hearing (N:8), conductive (N:8) or sensorineural (N:6). Ss were further grouped as younger and older. No significant differences in mean threshold, nor in time to reach threshold, were observed for either pattern of stress or age, suggesting that audiologists may interchange spondaic with trochaic stress when measuring speech thresholds in young children, with no effect on the mean value or the efficiency of the threshold (mn of .5, 1, and 2 kc/s) or on its correlation with the pure-tone HTL.

The effects of sophistication on three threshold tests for subjects with simulated hearing loss

Forty-five normal-hearing subjects were divided into three groups to determine the effects of listener sophistication on threshold estimates obtained with three commonly used tests for pseudohypacusis. A pure-tone Stenger test, speech Stenger test, and pure-tone delayed auditory feedback test were performed on each subject. The results indicate that increased sophistication levels allow subjects to simulate larger hearing losses on the two Stenger procedures. Sophistication level did not play a significant role in threshold determination with the delayed auditory feedback procedure, which was also found to be the closest indicator of true threshold.

The influence of syllabic stress on children's speech reception thresholds

One tape exemplar of each words cowboy, baseball, airplane, cupcake, popcorn, and hotdog spoken with natural (trochaic) and again with unnatural (spondaic) stress were selected from a pool to collect monaural SRTs by earphone in children. There were no significant differences due to type of stress, nor between boys and girls. Older children (N: 16, aged 5.0--6.0 yrs; SRT = --0.2 db HL) exhibited lower SRTs than younger (N: 16, aged 3.0--4.0 yrs; SRT = 3.2 db HL). It was informally observed that response, especially in younger Ss, tended (even when correct) to be at a slower rate, a condition to which the clinician should be alert.

On the relationship of stapedial contraction to central masking

The auditory masked threshold of a 1-kc/s pure tone was determined in quiet and with levels of white noise at 50-80 db SL in the non-test ear. Two groups of normal-hearing adults were tested, one (N:14, mn age = 27.4 yrs) with no history of middle-ear pathology, and another (N:12, mn age = 44.7 yrs) with the stapedial tendon severed. Significant differences in the amount of masked-threshold shift were observed, greater shifts being seen for the normal Ss, additional shifts ranging from 0.8-4.3 db as masking increased from 50-80 db SL. These differences were judged to be at least partly the result of stapedial contraction rather than having their origin entirely in central masking as often assumed.

Loudness and the acoustic reflex

Fifteen subjects with unilateral sensorineural hypacusis were tested to determine the sound intensity eliciting the acoustic reflex in normal and impaired ears and the sound intensity in the normal ear which is equal in loudness to the intensity eliciting the acoustic reflex in the abnormal ear. Results suggest that loudness is not the mediating factor in the acoustic reflex, justifying the suggestion that low sensation level reflexes observed in hearing-impaired patients should not be considered an unequivocal indicant of recruitment.

The masking plateau revisited

The masking plateau is defined in terms of effective masking. Formulas are advanced to indicate conditions of under-masking, minimum masking, the plateau, maximum masking, and overmasking.

The influence of pauses in the competing signal on synthetic sentence identification scores

Thirty normal-hearing subjects participated in an experiment testing the effects of pauses in the competing discourse on the synthetic sentence identification (SSI) task. When speech noise was added to the continuous discourse used for competition, subjects found it more difficult to identify the key words in the synthetic sentences.

Comparison of tangibly reinforced speech-reception and pure-tone thresholds of mentally retarded children

Sixteen mentally retarded children who had normal hearing were examined with two tests of auditory sensitivity. One procedure employed a tangibly reinforced operant-conditioning paradigm for pure tones, and the other test was based on a modification of operant conditioning for obtaining speech-reception thresholds. The speech procedure, utilizing an attractive mechanical device in the form of a clown, proved to be effective and efficient for use with retarded children.

Central masking effects on spondee threshold as a function of masker sensation level and masker sound pressure level

Thirteen subjects with normal hearing and thirteen with sensorineural hearing loss were tested with spondaic words to determine their spondee thresholds in the presence of several levels of contralateral noise. Results indicate that the threshold shift ascribed to central masking is a function of the sensation level of the noise. Recommendations for clinical application are made.

Measurement of speech thresholds of Spanish-speaking children by non-Spanish speaking clinicians

This study investigated the feasibility of a prerecorded speech threshold procedure that was used in a picture-pointing format, and was administered to Spanish-speaking children by non-Spanish-speaking clinicians. The derived Spanish word list was compared for equivalency to English spondees on a group of bilingual adults. The test, administered to 16 children ages three to six years, resulted in good agreement between SRT and pure-tone average. The test was found to be feasible, rapid, and reliable.

Audiologic detection of auditory processing disorders in children

A group of 11 normal children was compared to a group of language learning-disabled children on two auditory discrimination tasks. The word intelligibility by picture identification test was distorted by low pass filtering and bandpass filtering to be used as distorted monaural discrimination tasks and as tests of binaural fusion. Results revealed that the two groups could not be differentiated on the basis of distorted speech presented monaurally in diotic over dichotic scores than did the normal group. A procedure for audiologic screening for language learning-disabled children with normal hearing sensitivity is suggested.

Effects of sophistication on four tests for nonorganic hearing loss

Three groups of 15 normal-hearing subjects were asked to simulate a hearing loss in one ear. Each subject was then tested on four measurements often used in determining the presence of pseudohypacusis (a comparison of the SRT to the pure-tone average, ascending vs descending pure-tone tests, the Stenger test, and pure-tone delayed auditory feedback). Results showed that as practice and sophistication on each of the procedures increased, there tended to be more improvement in the subjects' ability to "beat" some of the tests than others.

On the cross hearing of spondaic words

Twelve adults with unilateral hearing losses were tested to determine interaural attenuation for spondaic words. Low-pass and band-pass filters were used to simulate hearing loss at the normal ear. Results suggest that in deciding on the possibility of cross hearing, the spondee threshold at the test ear should be compared to the most sensitive bone-conduction threshold at the nontest ear, excluding .25 kc/s.

A tangibly reinforced speech reception threshold procedure for use with small children

Forty normal-hearing children between 17 and 56 months were tested using a new method for determining speech reception thresholds. The words employed were names for parts of a device that was in the form of a colorful clown. The device automatically rewarded the child with a small piece of candy each time he pressed the part of the clown that had been announced through the sound field system of a speech audiometer. Results showed that operant conditioning speech audiometry using tangible reinforcers is feasible for small children. Both boys and girls can be tested accurately by this method down to age two and one-half years.

The effects of sophistication on Type V Bekesy patterns in simulated hearing loss

Forty-five normal hearing subjects were divided into three groups according to sophistication regarding Bekesy audiometry in simulated hearing loss. Both standard pulsed (200 msec on/200 msec off) and lengthened off-time (200 msec on/800 msec off) were compared with a continuous tone tracing at 1000 Hz. Data revealed a general decrease in the number of Type V patterns observed as sophistication increased.

A modification of the Tillman-Olsen method for obtaining the speech reception threshold

Twenty normal-hearing subjects were tested to determine their speech reception thresholds (SRTs) using the Tillman-Olsen method and a modification of their method requiring no knowledge of the pure-tone audiogram from which to estimate the SRT. Varying amounts of attenuation were added to the line leading to the test earphone to minimize experimenter bias. The data revealed no significant differences between the two methods in either the SRTs themselves or the amount of time required to obtain them. A procedure is therefore advanced for clinicians wishing to measure SRTs without prior knowledge of pure-tone thresholds.

Effects of external ear canal pressure on the middle-ear muscle reflex threshold

Twenty normal-hearing individuals served as subjects in an experiment designed to determine the relationships between positive and negative air pressure in the external auditory canal and the intensity required to elicit the acoustic reflex. Pressure was varied from +240 to −240 mm H 2 O. Changes in the magnitude of acoustic impedance were measured on an acoustic impedance meter and displayed graphically on a Y-T recorder. As air pressure was varied in the canal and the tympanic membrane was displaced from its position of greatest compliance, systematic increases in the intensity required to elicit the reflexes were noted. The magnitude of the differences was smaller than might have been anticipated, not exceeding a mean of 5.1 dB at −240 mm H 2 O.

Minimum effective masking levels in threshold audiometry

A procedure is described for masking during threshold audiometry. Illustrations are provided which show that use of an effective masking level equal to the threshold of the masked ear results in noise levels identical to those derived by the use of more complicated formulas.

Audiometric Bing test for determination of minimum masking levels for bone-conduction tests

Occlusion effects were determined and compared on three groups of subjects (20 normal hearers, 20 with conductive hearing loss, and 20 with sensorineural hearing loss). As in previous studies, the occlusion effects of the conductive group were clearly different from those of the other two groups, especially at 250 Hz. Two procedures are discussed which use the principle of the Bing test to determine when and how to compensate for the occlusion effect while masking for bone conduction.