Increase in US medication-error deaths between 1983 and 1993.
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Continuity of Patient Care↗
Biomedical subjects
D P Phillips
Publications and source records attributed to D P Phillips.
Detection of silent intervals between noises activating different perceptual channels: some properties of "central" auditory gap detection.
This article describes four experiments on gap detection by normal listeners, with the general goal being to examine the consequences of using noises in different perceptual channels to delimit a silent temporal gap to be detected. In experiment 1, subjects were presented with pairs of narrow-band noise sequences. The leading element in each pair had a center frequency of 2 kHz and the trailing element's center frequency was parametrically varied. Gap detection thresholds became increasingly poor, sometimes by up to an order of magnitude, as the spectral disparity was increased between the noise bursts that marked the gap. These data suggested that gap-detection performance is impoverished when the underlying perceptual timing operation requires a comparison of activity in different perceptual channels rather than a discontinuity detection within a given channel. In experiment 2, we assessed the effect of leading-element duration in within-channel and between-channel gap detection tasks. Gap detection thresholds rose when the duration of the leading element was less than about 30 ms, but only in the between-channel case. In experiment 3, the gap-detection stimulus was redesigned so that we could probe the perceptual mechanisms that might be involved in stop consonant discrimination. The leading element was a wideband noise burst, and the trailing element was a 300-ms bandpassed noise centered on 1.0 kHz. The independent variable was the duration of the leading element, and the dependent variable was the smallest detectable gap between the elements. When the leading element was short in duration (5-10 ms), gap thresholds were close to 30 ms, which is close to the voice onset time that parses some voiced from unvoiced stop consonants. In experiment 4, the generality of the leading-element duration effect in between-channel gap detection was examined. Spectrally identical noises defining the leading and trailing edges of the gap were presented to the same or to different ears. There was a leading-element duration effect only for the between channel case. The mean gap threshold was again close to 30 ms for short leading-element durations. Taken together, the data suggest that gap detection requiring a temporal correlation of activity in different perceptual channels is a fundamentally different task to the discontinuity detection used to execute gap detection performance in the traditional, within-channel paradigm.
Adult↗
Word recognition in continuous noise, interrupted noise, and in quiet by normal-hearing listeners at two sensation levels.
The effect of presentation level on word recognition performance-intensity functions in continuous and interrupted broadband noise and in quiet was explored. Normal-hearing participants were tested at 30 and 50 dB sensation levels (SLs). Performance-intensity functions in both noises were determined at signal-to-noise ratios (S/Ns) of 10, 5, 0, -5, -10, -15, and -20 dB. There was no effect of SL presentation on word recognition performance in quiet (p = 0.136). A significant main effect was observed for S/N in both continuous and interrupted broadband noise conditions (p < 0.0001). Performance increased with increases in S/N regardless of the competing noise condition. A significant main effect for SL presentation was only observed in the interrupted noise condition (p = 0.0019). That is, performance was higher for the 50 SL for the interrupted noise condition only. It is suggested that the observed difference in performance in interrupted noise at different SLs offers additional evidence for level-dependent, temporal masking phenomena.
Hearing↗
Elevated suicide levels associated with legalized gambling.
There has been no systematic, large-scale statistical investigation of the link between gambling and suicide, despite the suggestion of such a link from small-scale case studies. This article examines whether gamblers or those associated with them are prone to suicide and whether gaming communities experience atypically high suicide rates. Las Vegas, the premier U.S. gambling setting, displays the highest levels of suicide in the nation, both for residents of Las Vegas and for visitors to that setting. In general, visitors to and residents of major gaming communities experience significantly elevated suicide levels. In Atlantic City, abnormally high suicide levels for visitors and residents appeared only after gambling casinos were opened. The findings do not seem to result merely because gaming settings attract suicidal individuals.
Adult↗
Effects of bilateral auditory cortical lesions on gap-detection thresholds in the ferret (Mustela putorius).
Ferrets were tested for their ability to detect temporal gaps in noise before and after bilateral lesions of the primary auditory cortex. Thresholds for gap detection were determined first for normal animals with band-pass noises at various center frequencies (0.5 to 32 kHz) and at 8 kHz with various sound pressure levels (-10-70 dB). Gap-detection ability improved steadily as sound pressure increased up to 70 dB. No systematic relation was found between threshold and center frequency. To determine the effects of brain damage, ferrets were tested with 8-kHz band-pass noise at 70 dBSPL. After bilateral lesions of auditory cortex, ferrets were still capable of detecting gaps, but the mean threshold was elevated from 10.1 to 20.1 ms. The data demonstrate that auditory cortex is important for perceptual tasks requiring fine temporal resolution.
Animals↗
Word recognition in continuous and interrupted broadband noise by young normal-hearing, older normal-hearing, and presbyacusic listeners.
OBJECTIVE: Word recognition performance in continuous and interrupted broadband noise was examined in young normal-hearing (YNH), older normal-hearing (ONH), and presbyacusic (older hearing-impaired [OHI]) listeners. DESIGN: Participants (N = 36) were presented with identical Northwestern University Auditory Test No. 6 stimuli at 30 dB sensation level re their respective speech reception thresholds. The speech stimuli were presented in quiet and in both competing noise conditions with signal to noise ratios (S/Ns) of 10, 5, 0, -5, -10, -15, and -20 dB. RESULTS: In general performance was superior in quiet, improved with increasing S/N, and was greater in the interrupted broadband noise than in the continuous broadband noise. Significant main effects of group and S/N were found in both competing noises (p < 0.0001). Post hoc pairwise comparisons revealed all groups performed differently, with superior performance being displayed by the YNH group followed by the ONH and OHI groups, respectively (p < 0.05). A significant group by S/N interaction was observed in only the interrupted noise condition (p = 0.019). The degree of change in word recognition performance as a function of S/N was greatest in the OHI group followed by the ONH group and the YNH group. CONCLUSIONS: Group effects observed in the interrupted noise would imply that the two older groups of listeners had an auditory temporal deficit relative to the YNH listeners. The paradigm reveals the patency of the temporal processes that are responsible for the perceptual advantage (i.e., a release from masking) a listener has in interrupted competing stimulus.
Adult↗
Stimulus-induced spike bursts in two fields of cat auditory cortex.
The sound-evoked responses of extracellularly recorded cat primary auditory cortical neurons usually consist of a single spike or a short-term burst of 2-4 spikes, irrespective of the nature of the acoustic signal. In the cat's auditory cortex, the properties of such responses have to date been described only for cells in the primary field (AI). The purpose of the present study was to describe the properties of stimulus-evoked spike-burst responses seen in neurons of the posterior auditory field (P) and to compare those properties with those of a sample of AI neurons studied under similar conditions. The data come from 80 field P and 31 AI neurons studied with tonal and noise-burst stimuli in barbiturate-anesthetized cats, using calibrated, sealed stimulus delivery systems and conventional extracellular recording techniques. The mean inter-spike intervals (ISI) seen in the transient burst responses of posterior field cells were typically short (2-5 ms) and, where it was possible to test them, independent of the rise time of tonal signals, suggesting that they were also independent of the onset spectrum of the stimulus. The mean ISIs were often independent of the stimulus amplitude, even though the signal level had profound effects on the number of spikes evoked and the latency and regularity with which the responses were initiated. Each neuron was assigned a 'characteristic ISI', i.e., the mean ISI seen in the most vigorous responses. The distribution of characteristic ISIs for AI and P neurons overlapped, but were significantly different, with the characteristic ISIs of field P neurons being longer. In both AI and P populations, characteristic ISI was significantly correlated with minimal first-spike latency. The slopes of the regression lines of characteristic ISI on minimal latency for AI and for P cells were not significantly different from each other. Since the minimal latencies of AI neurons were usually shorter than those of field P neurons, the shorter characteristic ISIs of AI cells may thus be interpreted as secondary to their shorter latent periods. The general properties of stimulus-evoked spike bursts seen in field P neurons were thus very similar those previously described for AI cells. These data are consistent with the view that the majority of extracellular recordings in the cat's auditory cortex come from pyramidal neurons and are appropriate as a specialization for transfer of information to nonpyramidal, inhibitory interneurons.
Acoustic Stimulation↗
An acoustic basis for maternal recognition in timber wolves (Canis lupus)?
An in-den recording system was used to monitor the vocalizations and behavior of adult wolves tending to a litter of pups during the first five postnatal weeks. Two female adults, one of them the mother, tended to the pups on nonoverlapping schedules. The distributions of the fundamental frequencies of the adults' squeak vocalizations were largely nonoverlapping, suggesting that this feature may be available as an acoustic cue to individual recognition. Squeaks emitted outside the den, and which were associated with pup exit responses, had fundamental frequencies wholly within the range of the mother's, raising the possibility that the pups used this as a cue for maternal recognition.
Acoustics↗
Factors shaping the tone level sensitivity of single neurons in posterior field of cat auditory cortex.
1. The posterior field (field P) of the cat's auditory cortex contains a higher proportion of neurons whose response/level functions for characteristic frequency (CF) tones are nonmonotonic than does the primary field (AI). The general purpose of the present study is to assess whether the response/level functions of field P neurons are generated by the same mechanisms as those of cells in AI. All of the data came from single neurons in the cortices of barbiturate-anesthetized cats, to which we presented tonal stimuli through sealed, calibrated stimulating systems. 2. We obtained quantitative data from 123 neurons, of which 108 were located in field P. Of the 108 field P cells, 70% had nonmonotonic response/level functions for 5-ms rise time tones of CF. For cells of any given CF, both CF thresholds and best SPLs (i.e., SPLs associated with maximal responses) varied widely. A correlation analysis revealed that a linear relation between best SPL and CF threshold accounted for 73% of the data variance in the association between those response variables. An analysis of data from 83 nonmonotonic cells in AI revealed a similar relation. 3. Field P neurons whose response/level functions were non-monotonic for 5-ms rise time CF tones became even more narrowly tuned to SPL when the rise time of the tone bursts was reduced to 1 ms. Lengthening the rise time to 20 ms reduced or eliminated the SPL tuning in almost all of these neurons. The general form of monotonic tone response/level functions was commonly unaffected by variation in signal rise time. In a few instances, cells with monotonic response/level functions for 5- and 20-ms rise time tones developed nonmonotonic functions for 1-ms rise time tones. 4. Field P neurons with nonmonotonic response/level functions for CF tones usually failed to respond to wideband noise pulses, or, less commonly, responded to noise only at low SPLs. In contrast, field P cells with a monotonic response to CF tones usually responded monotonically to noise. 5. The minimal mean first-spike latencies of field P neurons were generally longer than those of AI cells studied under similar conditions. The precision of first-spike timing, measured using the SD of the mean first-spike latency, was commonly poorer than that of AI cells. 6. The properties of field P cells followed the same rules as those seen in AI.(ABSTRACT TRUNCATED AT 400 WORDS)
Action Potentials↗
Central auditory processing: a view from auditory neuroscience.
The purpose of this report is to overview some recent advances in basic science that help us understand the roles of the central auditory nervous system in hearing. Particularly at rostral levels, neural representations of the acoustic signal are shaped by convergent inputs and show some degree of plasticity, even in adults. The fidelity with which brain regions represent a stimulus dimension is heterogeneous, and this has demonstrable implications for the perceptual consequences of damage to those regions. So-called higher-level disorders (e.g., phonologic ones) have become increasingly understandable, largely through work in cognitive neuroscience, which has begun to describe the functional architecture of the processes mediating sound recognition and comprehension.
Animals↗
Word recognition performance in continuous and interrupted broad-band noise by normal-hearing and simulated hearing-impaired listeners.
Word recognition performance was investigated in 12 normal-hearing young adults in continuous and interrupted broad-band noise as a function of signal-to-noise ratio (S:N) with and without a simulated high frequency hearing loss (i.e., low-pass filtered at 2000 Hz). Subjects exhibited conventional sigmoid performance-intensity functions in continuous noise, for both unfiltered and filtered conditions. In contrast, subjects demonstrated shallower performance-intensity functions in the interrupted noise conditions with overall superior performance under adverse signal-to-noise ratios relative to the continuous noise conditions. Separate two-way analyses of variances investigating mean word recognition performance differences as a function of normal listening (unfiltered) versus the simulated hearing loss (filtered). Signal-to-noise ratio for both continuous and interrupted noise conditions revealed a significant main effects for S:N with both noise conditions (p < .05) and a significant main effect for the simulated hearing loss only in the interrupted noise condition (p < .05). It was hypothesized that subjects' diminished performance in the interrupted noise condition with the stimulated high frequency hearing loss reflected a reduced ability to temporally resolve auditory information between the gaps of noise.
Adult↗
Compressive stress-relaxation behavior of bovine growth plate may be described by the nonlinear biphasic theory.
The compressive behavior of the bovine distal femoral growth plate was studied in vitro. Strain-rate controlled, compression stress-relaxation experiments were performed on cylindrical bone-growth plate-bone specimens from the interior and periphery of the growth plate. The questions addressed in this study were (a) Can the nonlinear biphasic theory, one with strain-dependent permeability, be used to represent the compressive stress-relaxation behavior of bovine growth plate? (b) How do different assumptions concerning the permeabilities of the chondro-osseous interfaces influence the inferred material properties of the growth plate? and (c) Are there any differences in these properties between the periphery and the interior of the growth plate? Intrinsic biphasic material properties--aggregate modulus (HA), Poisson's ratio (v), and nonlinear strain-dependent permeability coefficients (ko and M)--were calculated from the compression stress-relaxation data with use of a finite element model and a least squares curve-fitting procedure. To verify this constitutive model for the growth plate, an independent set of finite element analyses was performed with use of the determined intrinsic biphasic properties, and comparisons were made between these finite element predictions and two additional sets of experimental data subsequently obtained for the same specimens with use of two slower rates of compression. Excellent agreement was achieved between these finite element predictions and the latter two sets of data. The aggregate modulus was found to be insensitive to the permeability of the chondro-osseous interface. The permeability coefficients were very sensitive to, and the Poisson's ratio was only slightly sensitive to the interface permeability condition. Therefore, the periphery of the growth plate is more compliant and permeable than the interior.
Animals↗
Level-dependent representation of stimulus frequency in cat primary auditory cortex.
The tonotopicity of the cat's primary auditory cortex (AI) is thought to provide the framework for frequency-specific processing in that field. This study was designed to assess this postulate by examining the spatial distribution of neurons within AI that are activated by a single tonal frequency delivered to the contralateral ear. Distributions obtained at each of several stimulus levels were then compared to assess the influence of stimulus amplitude on the spatial representation of a given stimulus frequency in AI. Data were obtained from 308 single units in AI of four adult, barbiturate-anesthetized cats, using extracellular recording methods. Stimuli were 40-ms tone pulses presented through calibrated, sealed stimulating systems. In each animal, the CF (stimulus frequency to which the unit is most sensitive), threshold at CF, response/level function at CF, and binaural interactions were determined for isolated neurons (usually one per track) in 60-90 electrode tracks. For each unit, regardless of its CF, responses to 40 repetitions of contralateral tones of a single frequency, presented at each of four or five sound pressure levels (SPLs) in the range from 10 to 80 dB were obtained. Different test frequencies were used in each of four cats (1.6, 8.0, 11.0, and 16.0 kHz). For tones of each SPL, we generated maps of the response rates across the cortical surface. These maps were then superimposed on the more traditional maps of threshold CF. All units whose CF was equal to the test frequency could be driven at some SPL, given an appropriate monaural or binaural configuration of the stimulus. There was a clear spatial segregation of neurons according to the shapes of their CF tone response/level functions. Patches of cortex, often occupying more than 2 mm2, seemed to contain only monotonic or only nonmonotonic units. In three cortices, a patch of nonmonotonic cells was bounded ventrally by a patch of monotonic cells, and in one of these cases, a second patch of monotonic cells was found dorsal to the nonmonotonic patch. Contralateral tones of any given SPL evoked excitatory responses in discontinuous cortical territories. At low SPLs (10, 20 dB), small foci of activity occurred along the isofrequency line representing the test frequency. Many of these cells had nonmonotonic response/level functions. (ABSTRACT TRUNCATED AT 400 WORDS)
Animals↗
Auditory temporal resolution in multiple sclerosis.
Disturbances of hearing in multiple sclerosis patients have been variably reported, likely because standard audiologic testing emphasizes assessment of peripheral, rather than central, auditory function. This study investigated a group of patients with multiple sclerosis (MS), prospectively selected on the basis of magnetic resonance imaging (MRI) scans. Five of these patients had demyelinating lesions that included the rostral auditory fibre tracts, while another seven patients had lesions restricted to brainstem auditory sites. A further four had no lesions in the distribution of their auditory pathways. A comprehensive battery of audiometric tests, including standard audiometry and retrocochlear testing, was performed. In addition, their findings on electrophysiologic testing, including auditory brainstem responses (ABR) and middle latency responses (MLR), were studied. Finally, their performances in gap detection and speech recognition in continuous and interrupted background noise were examined to assess their auditory temporal resolution. The MS patients were found to be selectively impaired under the interrupted masker of this speech-in-noise paradigm, confirming a temporal processing defect. Furthermore, these patients' performances suggested a predominant role of forebrain pathways in mediating auditory temporal resolution.
Adult↗
Impaired word recognition in noise by patients with noise-induced cochlear hearing loss: contribution of temporal resolution defect.
Fifteen patients with mild noise-induced cochlear hearing loss reported a selective difficulty in understanding speech in noisy settings. To examine the hypothesis that a temporal resolution defect was responsible for this difficulty, the patients were tested for their recognition of monosyllabic words presented against continuous and interrupted wide-band noise backgrounds, at each of seven signal-to-noise ratios. Their recognition performance was compared with that of normal listeners studied with the same paradigms. By comparison with the controls, the group with cochlear hearing loss showed a significant recognition impairment only for words presented against the interrupted masker. This finding was in keeping with the existence of a temporal resolution defect in cochlear disease, though it need not indicate a stimulus timing defect at the level of individual cochlear neurons.
Adult↗
Psychology and survival.
We examined the deaths of 28,169 adult Chinese-Americans, and 412,632 randomly selected, matched controls coded "white" on the death certificate. Chinese-Americans, but not whites, die significantly earlier than normal (1.3-4.9 yr) if they have a combination of disease and birthyear which Chinese astrology and medicine consider ill-fated. The more strongly a group is attached to Chinese traditions, the more years of life are lost. Our results hold for nearly all major causes of death studied. The reduction in survival cannot be completely explained by a change in the behaviour of the Chinese patient, doctor, or death-registrar, but seems to result at least partly from psychosomatic processes.
Astrology↗
Neural representation of stimulus times in the primary auditory cortex.
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Auditory Cortex↗
Representation of acoustic events in the primary auditory cortex.
One approach to the problem of specifying the contribution of the primary auditory cortex to auditory perception has been based on single-neuron recording techniques in animals. These experiments measure the response rates of individual neural elements to parametric variations in 1 or more stimulus dimensions. The patterns of response rates and response failures revealed by these manipulations are quantitative descriptions of the form and fidelity of the cortex's representation of those stimulus dimensions. This strategy has been used to advantage in studies of the cortical representation of the spectral content of auditory events, the spatial location of a sound, and the time structure of sounds. The data constitute new links between neural coding and behavioral performance in normal and impaired listeners.
Animals↗