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Biomedical subjects

D A Robin

Publications and source records attributed to D A Robin.

At least 37 records · Page 2Linked to original sources
PubMed1996

Speech timing in apraxia of speech versus conduction aphasia.

This study examined temporal parameters of speech in subjects with apraxia of speech, conduction aphasia, and normal speech. They were asked to repeat target words in a carrier phrase 10 times. Acoustic analyses involved measurement of stop gap duration, voice onset time, vowel nucleus duration, and consonant-vowel (CV) duration. Speakers with apraxia of speech had longer and more variable stop gap, vowel, and CV durations than did subjects with aphasia or normal speech. Speakers with conduction aphasia had longer vowel durations and CV durations than subjects with normal speech. Also, subjects with apraxia of speech showed greater token-to-token variability than the other subject groups. The variability shown by subjects with apraxia of speech was significantly correlated with perceptual judgments of their speech. The significance of these results is discussed in the context of motoric and phonological explanations for apraxia of speech and conduction aphasia.

Adult↗
PubMed1996

Bilateral effects of unilateral visual cortex lesions in human.

We studied the vision of 12 patients with unilateral lesions of the visual cortex. All had a VI-type scotoma located in the contralateral visual fields, as expected, and visual acuity of 20/30 or better. Our aim was to test the hypothesis that they also had a visual deficit in their ipsilesional or 'good' visual fields. The first experiment tested the subjects' ability to respond to transient signals presented at unpredictable temporal intervals and spatial locations amongst many spatially random and identical distracter elements. The results showed that, compared with controls, the lesion group had a significantly reduced sensitivity to signal and increased response times affecting both hemifields. In a second experiment, we tested the useful field of view (UFOV) in two of the patients under conditions of differing attention demand. Both showed bilateral constriction, compatible with the results of the first experiment. One possible explanation for the bilateral effects of unilateral occipital lobe lesions is damage to interhemispheric connections along their presplenial course, affecting the synthesis of visual information from both hemifields (i.e. the interhemispheric diaschisis effects put forth by von Monakow). The trouble is task dependent and can be construed as a global reduction in visual attention capacity. It is subtle in comparison with the contralesional V1-type scotoma that Holmes measured, yet may account for unexplained complaints of reduced performance in some patients, particularly in tasks with high visual information processing demands, such as reading and automobile driving.

Adult↗
PubMed1996

Endogenous visuospatial precuing effects as a function of age and task demands.

This experiment examined the effects of age on processing resource capacity using an endogenous visuospatial precuing task and four levels of resource demands. Younger and older adults made speeded two-choice responses to dim and bright targets that required a line-orientation or a lexical decision. An arrow preceding target onset served as an attentional cue to affect the spatial distribution of resources. It provided accurate information about the target's location on most trials and inaccurate or neutral information on the remaining trials. Although older adults were slower than younger adults under all conditions and were more affected by the resource demand manipulations, they exhibited a pattern of precuing effects across conditions that was similar to that of the younger adults. Results are consistent with the idea that the visuospatial attention system remains relatively unaffected by aging. However, the data speak against the idea that capacity reduction is the primary contributor to age-related slowing.

Adult↗
PubMed1995

A model of "sense of effort" during maximal and submaximal contractions of the tongue.

Fatigue in the oral motor system may be accompanied by the perception of an increased "sense of effort." Awareness of centrally generated motor commands that result in synaptic inputs to motoneuron pools are thought to be responsible for these perceptions of effort (e.g., Muller, 1840; McCloskey, 1981). Few studies of the perceptual phenomenon of sense of effort exist, particularly of the oral motor system. The present study required 20 normal adults to push on a fluid-filled bulb using their tongue and hand. Subjects repeatedly exerted from 10 to 100% of the maximal effort, in random order, in 10% increments. The pressure produced by pushing on fluid-filled bulbs was compared to the effort level attempted. Subjects produced consistent, reliable pressures related to effort level. The best mathematical model for both the tongue and hand data was third-order polynomial. It is hypothesized that the perception of effort derives from a central source that operates across various motor systems.

Adolescent↗
PubMed1995

Case study: obsessive-compulsive disorder after severe traumatic brain injury in an adolescent.

The neurological underpinnings of obsessive-compulsive disorder (OCD) are still largely undetermined. We report a prospective case study of a young subject who developed OCD and impulsive aggression after traumatic brain injury. The implications are that frontal and temporal lobe lesions may be sufficient to precipitate OCD in the absence of clear striatal injury and that compulsivity and impulsivity may represent different psychophysiological states.

Brain↗
PubMed1993

Visuomotor tracking ability of young adult speakers.

This study was conducted to (a) study the ability of young adult subjects to track target signals with the lower lip, jaw, or larynx, (b) examine subjects' abilities to track different sinusoidal frequencies and unpredictable target signals, and (c) test notions of response mode and predictive mode tracking reported for nonspeech structures by previous authors (e.g., Noble, Fitts, & Warren, 1955; Flowers, 1978). Twenty-five normal speakers tracked sinusoidal and unpredictable target signals using lower lip and jaw movement and fundamental frequency modulation. Tracking accuracy varied as a function of target frequency and articulator used to track. The results quantify the visuomotor tracking abilities of normal speakers using speech musculature and show the potential of visuomotor tracking tasks in the assessment of speech articulatory control.

Adult↗
PubMed1992

Orienting attention in audition and between audition and vision: young and elderly subjects.

This study examined 30 young and 10 elderly subjects to test whether orienting of attention could be measured in audition. Orienting in a mixed-modal condition in which stimuli were either auditory or visual was also tested. The dependent measure was the reaction time (RT) to lateralized targets when the locations were predicted by antecedent arrow cues that were correct (valid), were incorrect (invalid), or provided no lateralizing information (neutral). A comparison between the two groups among the different conditions showed that elderly subjects had longer RTs than the younger participants, but the pattern of results was similar in both groups. In addition, a similar RT pattern was found for each modal condition: Valid trials elicited the fastest responses and invalid trials the slowest. These findings suggest that the mechanisms involved in orienting attention operate in audition and that individuals may allocate their processing resources among multiple sensory pools. Moreover, effects seen in orienting attention in audition were similar to those found in vision and are interpretable with the same types of models. Orienting attention appears to be relatively resistant to the aging process in the sample of subjects tested in this study.

Acoustic Stimulation↗
PubMed1992

Tongue strength and endurance: relation to highly skilled movements.

Tongue strength and endurance (fatigue) were examined in subjects who have acquired high skill levels with their tongues (supranormal) and in subjects who use the tongue normally. The supranormal groups were trumpet players and high school debaters who were able to speak intelligibly at rates much faster than normal. Hand strength and fatigue were also assessed. Maximal strength was measured by recording how much pressure an individual could exert on an air-filled bulb. Endurance was measured by determining how long subjects could sustain 50% of their maximal pressure. Results showed that maximal strength of the tongue and hand did not differentiate the supranormal subjects from the normal subjects. Hand endurance did not differentiate the subjects either. However, the supranormal groups had significantly longer tongue endurance times than did the normal subjects.

Adult↗
PubMed1990

Auditory perception of temporal and spectral events in patients with focal left and right cerebral lesions.

The auditory perception of temporal and spectral information was studied in subjects with lesions in the temporoparietal region of the left (LH group), or right (RH group) hemisphere (n = 5 in each group) and in five normal controls. The temporal tasks included gap detection and two complex pattern perception tasks in which subjects had to identify the placement of the two closest tones (separated by the shortest interval) within a sequence of six tones. The spectral tasks involved pitch matching and frequency discrimination. The results showed a "double dissociation": (1) the LH group was impaired in their ability to perceive temporal information, but the perception of spectral information was normal, and (2) the RH group was impaired in their ability to perceive spectral information, but the perception of temporal information was normal. The findings are consistent with the notion that temporal processing is a function of left-hemisphere structures and that spectral processing is a function of right-hemisphere structures.

Adult↗
PubMed1990

Subcortical lesions and aphasia.

Recent evidence suggests that subcortical lesions can give rise to aphasic symptoms. Two subcortical structures thought to participate in the pathogenesis of aphasia are the basal ganglia and the thalamus. This paper reports on 3 patients with lesions of the thalamus and 10 patients with lesions of the basal ganglia, most of whom had persistent aphasias. The role of subcortical structures in aphasia and the importance of subcortical structures in neural models of language are discussed.

Adult↗
PubMed1990

Neural responses to auditory temporal patterns.

Sets of regularly repeating auditory stimuli elicit unique perceptions; listeners are able to identify specific temporal patterns. Some temporal patterns are unambiguous (only one pattern can be perceived), while others are ambiguous (numerous patterns can be detected). While the psychophysical properties of such percepts have been well studied, little is known about the underlying neurological bases of temporal pattern perception. In this experiment, the role of adaptation in temporal pattern perception is examined by studying neural responses in four cats to a temporal pattern that is perceptually unambiguous and one that is perceptually ambiguous. Measurements were made of the whole-nerve action potential, the auditory brainstem response, and potentials from the surface of the primary auditory cortex. The adaptation patterns corresponded with the perceptual organization of temporal patterns in humans at all levels of the nervous system studied.

Animals↗
PubMed1990

Simultanagnosia: a defect of sustained attention yields insights on visual information processing.

Simultanagnosia, in which subjects report a piecemeal visual experience, offers an important probe of human attention. We studied 2 subjects with simultanagnosia following bilateral superior occipital strokes. Compared with controls, they could orient attention to spatial targets in visual, auditory, and mixed-modal conditions. A different task required immediate response to the appearance or disappearance at unpredictable intervals of any element in a random-dot CRT display. The subject tested could detect less than 50% of 1,600 events, and had increased "mirages" and prolonged reaction times. Undetected events occurred anywhere and formed temporal clusters. Application of signal-detection theory confirmed abnormal sensitivity and response bias (d' and beta). Yet performance improved when a valid cue introduced events in the random display. Our results suggest that simultanagnosia was related to an inability to sustain visuospatial attention across an array, corresponding to processing failure at a level of long-range (global) spatiotemporal interactions among converging inputs from early vision. The operations for orienting and sustaining attention may be dissociable at visual association cortex levels.

Adult↗
PubMed1989

Auditory temporal pattern learning in children with speech and language impairments.

Four children demonstrating speech and language impairments were examined with respect to their ability to learn to identify certain auditory temporal perceptual information. These children listened to six-element temporal patterns and made judgments about the temporal proximity of two of the elements. Subjects listened to the patterns over a number of exposures ranging from 6 to 14, depending on the subject. Performance on the task improved significantly with repeated exposures. However, the disordered subjects' best performance was still significantly poorer than normal children who had only 1 exposure to the task. These results suggest that, in part, performance differences on temporal perceptual tasks between speech and language disordered children and normal children can be accounted for by differences in perceptual learning. However, because the disordered children never reached normal levels, learning differences may be associated with a fundamental deficit in temporal processing or some other mechanism such as impaired attention.

Attention↗
PubMed1989

Age-related changes in auditory temporal processing.

Two tone bursts separated by a silent interval and imbedded in a background white noise were presented to elderly subjects (M age = 71.3 years) and young subjects (M age = 22.2 years). Subjects were required to judge when the two tone bursts fused perceptually by adjusting the duration of tone-one. The bursts were separated by six discrete interstimulus intervals of 4, 8, 16, 24, 32, or 40 ms. The tone-two burst was held constant at 100 ms. Fusion point was defined as that critical tone-one duration at which the two tones fused (were perceived as one). Elderly subjects reached fusion point at longer critical tone-one durations than young subjects at each interval tested. The function relating tone-one duration and interval conformed to an exponential curve and is discussed with respect to an exponential decay model of the inhibitory interactions of neural systems responding to onsets and offsets of sensory events.

Adolescent↗
PubMed1989

Lip movement in apraxia of speech.

Peak articulatory velocity of the lower lip and temporal coordination between the upper and lower lips were studied in 5 neurologically impaired subjects with speech behaviors consistent with a diagnosis of apraxia of speech. Differences in velocity and the timing between the movement onset of the two lips were compared for accurate and inaccurate productions of words. Peak articulatory velocity also was measured during the productions of the syllable [pae] and during a nonverbal movement. There were no systematic differences across accurate and inaccurate productions of words in peak articulatory velocity or movement onsets of the two lips. Furthermore, there were no systematic changes in movement velocity related to speech rate. We conclude that some apraxic speakers do not have a defect in the ability to produce high movement velocities.

Adult↗
PubMed1988

The role of callosal connections in speech prosody.

A 39-year-old right-handed woman suffered an aneurysmal hemorrhage damaging the anterior four-fifths of the corpus callosum as shown on MRI. Computer-aided acoustical analyses of fundamental frequency (Fo) contours and durational patterns were performed on emotive and nonemotive utterances at 4 weeks, 4 months, and 1 year postsurgery. The patient read sentences in each of five tones (happy, sad, angry, neutral, questioning) or with emphasis on certain words. She showed little Fo distinction with intended mood at 4 weeks, but her performance improved over time. This improvement in speech production was accompanied by an improvement in perceptual judgments of her intended tone by six normal listeners. Fo patterns characteristic of emphatic stress and question forms were found at all test periods, but again improved with time. Durationally, the patient showed appropriate emotive and nonemotive distinctions on most sentences. These results provide acoustic evidence that interhemispheric connections via the corpus callosum are important to proper Fo programming, especially emotive distinctions. The results suggest that the right hemisphere contributes to Fo programming but, following callosal damage, such programming can later be performed by the left hemisphere.

Adult↗
PubMed1987

Auditory temporal processing: two-tone flutter fusion and a model of temporal integration.

Auditory temporal processing was examined using a flutter-fusion paradigm in which two tones were separated by a silent interval. The listener's task was to judge when the two tones, presented in a background noise, fused perceptually. The fusion point was studied in a series of six experiments. In the first five experiments, the duration of the first stimulus (T1) was the dependent variable. In the last experiment, the duration of the second stimulus (T2) was the dependent variable. An inverse relationship was found between T1 duration and the interstimulus interval (ISI) such that, when ISI was decreased, T1 duration had to be increased to maintain fusion. When ISI was plotted as a function of T1 duration, the data were represented by a negative exponential equation. Increasing the level of the tones, increasing the bandwidth of the background noise, or presenting the stimuli dichotically lowered the duration of T1 necessary for fusion. Changing the frequency of the tones had no effect on fusion. Decreasing the duration of T2 and holding T1 constant also resulted in fusion. A neurophysiological model implicating ON and OFF neural response interactions is postulated to account for the data.

Adult↗