Nancy Niccum

A longitudinal study of speech fluency in aphasia: CT correlates of recovery and persistent nonfluency

The anatomic correlates of speech fluency were studied in 54 right-handed patients with aphasia due to stroke. Speech fluency was assessed at 1 month postonset and then monthly for 5 months. CTs obtained at 5 months postonset were used for lesion localization and volume determination. Persistent nonfluency was associated with lesions in the rolandic cortical region and underlying white matter. Recovery from nonfluency occurred in 6 of 27 patients. Lesions in these six patients were less extensive than lesions in patients with persistent nonfluency. Patients who were fluent by 1 month lacked extensive rolandic lesions.

Recovery of naming in aphasia: Relationship to fluency, comprehension and CT findings

We assessed oral naming skill after left hemisphere ischemic stroke in 54 right-handed aphasics. Initially, almost all had moderate to severe disability in oral naming. After 6 months, normal scores were achieved by one-third of the patients, all with lesions less than 60 cm? in volume. Only 2 of 18 patients who were nonfluent at 6 months had normal naming then. Among patients with lesions less than 60 cm3 and persistently poor naming, there were two discrete lesion sites: posterior superior temporal-inferior parietal (semantic paraphasic errors) and insula-putamen (phonologic paraphasic errors). Individual variability was notable, with several patients regaining normal naming ability despite posterior temporal or insula-putamen lesions.

Statistical properties of responses to dichotic listening with CV nonsense syllables

Twenty-four listeners received 20 dichotic listening runs of 30 pairs of natural CV nonsense syllables per run. Left- and eight-ear responses are represented by two partially overlapping normal distributions with equal variance. Observed ear advantages across listening runs are also distributed normally. The means of the distribution of ear advantage are listener specific, but the standard deviations are 10.8% +/- 2.5. The origin of reversals in direction of ear advantage among listening runs is statistical--a small mean/sigma ratio--and approximately six listening runs (180 listening trials) are required to achieve a split-half reliability coefficient of + 0.90.

Regional cerebral blood flow patterns during verbal and nonverbal auditory activation

Abstract Current views of the relationship between audition and cerebral function suggest that increases in regional cerebral blood flow (rCBF) would occur in the superior, mid, and posterior portions of the temporal lobes, and that these changes would be more lateralized to the left hemisphere for a verbal than a nonverbal auditory task. We measured rCBF using the xenon inhalation technique in a group of healthy subjects during three conditions: (1) resting baseline, (2) auditory verbal activation (listening for word meaning), and (3) auditory nonverbal activation (listening for reduction of intensity in a series of noise bursts). Both verbal and nonverbal conditions produced highly significant increases in rCBF over the left posterior Sylvian region with a trend for verbal activation to evoke a wider area of flow increase than the nonverbal task.

“Late” recovery of the right ear dichotic score following cerebrovascular accident: A case report

Late recovery of the right ear score on a digit dichotic listening test was observed in a 45-yr-old female patient. The right ear score was at chance levels of accuracy through the ninth month post-onset of a cerebrovascular accident and then improved dramatically to 67% correct by month 12. Possible bases for this pattern of performance are discussed.

Comparison of target monitoring and two‐ear monitoring dichotic listening procedures

The dichotic listening performance of 40 listeners was assessed for consonant-vowel (CV) nonsense syllables with two procedures. One was a conventional two-ear monitoring task in which listeners attended to both ears and provided two responses for each pair of syllables. The ear advantage was described by % RE-% LE. The second was target monitoring, a yes/no task in which listeners attended to only one ear and listened for the presence of a target syllable. That procedure provided both hit and false alarm rates for each ear, and the ear advantage was described by P(C)maxRE-P(C)maxLE, which is insensitive to decision variables. Although both procedures yielded mean right-ear advantages (REA), the mean REA of +7.5% with two-ear monitoring was significantly different from the mean REA of +2.6% with target monitoring. In addition, although 62% of the listeners had a significant REA with the conventional procedure, only 40% had a significant REA with target monitoring. Decision variables, which are not controlled with conventional dichotic testing methods, may contribute to the ear advantage as it is described frequently in the literature.

Reinterpretation of the “lag effect” in dichotic listening

CV syllables were presented dichotically and with the left‐ear (LE) syllables delayed by intervals ranging from 20 to 150 msec. The “lag effect,” where scores for the lagging LE exceed those for the leading RE, occurred only with voiced stops in RE, and mainly when voiced stops in RE were paired with voiceless stops in LE. For all types of CV pairs, LE scores increased linearly beyond 20‐msec delay and were asymptotic by 80 msec. RE scores, however, did not decrease with LE lag unless voiceless stops in LE were paired with voiced stops in RE. There was no evidence that the later‐arriving LE syllable interrupted processing of the RE syllable [M. Studdert‐Kennedy et al., J. Acoust. Soc. Am. 48, 599–602 (1970); C.I. Berlin et al., J. Acoust. Soc. Am. 53, 699–709 (1973)] or that backward masking was involved [Pisoni and McNabb, Brain and Language 1, 351–362 (1974)]. We believe that the “lag effect” has an acoustic origin, and that it exists mainly because crucial formant‐transition cues in the LE syllable are...

Relative ear advantage and element duration

Lauter [J. Acoust. Soc. Am. 71, 701-707 (1982)] reported that although the magnitude and direction of the absolute ear advantage for speech and nonspeech sound sets presented dichotically varies considerably among listeners, consistent patterns of a relative ear advantage (EArel) across sound sets are preserved from listener to listener. She further claimed that EArel appeared to be related to the duration of elements that composed a sequence. The existence of EArel is investigated for four sound sets: CV nonsense syllables and pitch patterns that were composed of 50-, 80-, or 120-ms tones. The paradigm was target monitoring, a Yes/No task in which listeners attended to only one ear and listened for the presence of a target signal. The results failed to confirm that listeners have a consistent relative ear advantage related to element duration for nonspeech sound sets.

Locua of adaptation effects for the voicing feature

Eight listeners participated in two experiments. The first tested for simultaneous dichotic adaptation by obtaining monaural identification functions before and after adaptation with /ba/ and /pa/ presented dichotically. The difference between the number of/ba/responses for left‐ and right‐ear postadaptation identification was significant. The second experiment assessed the magnitude of interaural transfer. Adaptation and identification stimuli were presented monaurally and identification shifts for the unadapted ear were compared with those for the adapted ear. When /ba/ was the adapting stimulus, only 62%–65% transfer was obtained, but the difference between ears was nonsignificant. When /pa/ was the adapting stimulus, 51%–52% transfer was obtained and the difference between ears was significant. The failure to each significance for the /ba/ conditions may relate to the smaller absolute size of shifts in identification. In general, the results of both experiments provided evidence for a bilateral compon...

Noninvariance of the ear advantage in dichotic listening

Listeners received 50 dichotic trials of both natural and synthetic CV syllables, and marked two responses for each of 30 syllables pairs per trial. The paired responses were distributed as a bivariate normal; left and right‐ear scores had equal variance (σ=8%) and were uncorrelated (r=−0.02 for synthetic; +0.15 for natural). Percent ear advantage also was distributed normally with a standard deviation about equal to the mean (synthetic, X=12.9%, σ=11%; natural, X=9%, σ=10%). Thus, listeners with a mean REA evidenced many trials with either no ear advantage or an LEA (29% natural; 19% synthetic). Variability in left and right‐ear scores is assumed to arise from random, uncorrelated, time‐varying “noise” in pathways from each ear. The ear advantage, left or right, is modeled as a function of the S/N ratio in the respective pathways. The ear advantage is not invariant and, by this account, may not always be indicative of unilateral hemispheric specialization for speech processing. [Supported by PHS Grant No. NS‐12125.]