David B. Rosenfield

The Role of Electromyography in Clinical Laryngology

Laryngeal electromyography (EMG) has been used primarily as a research tool with only limited application to clinical practice. We have performed laryngeal EMG in a clinical research setting for over 2 years and have found it a valuable adjunct in selected situations. The electrophysiology and technique of laryngeal EMG are reviewed. Laryngeal EMG is the most accurate method of determining compromise of the superior laryngeal nerve. It is valuable in evaluating patients with mechanical fixation of the vocal cords. The eventual outcome of recurrent laryngeal nerve paralysis may also be predicted in certain patients. Laryngeal EMG is safe, easy to perform, and should be considered when evaluating the patient with laryngeal dysfunction.

A neuroscience model of stuttering

Abstract Using motor control systems analysis and a reductionist approach, we provide a unified model of stuttering. This model views stuttering as a momentary instability in a complex multiloop control system. The model predicts the temporal conditions under which this instability will occur. Furthermore, these temporal conditions account for the efficacy of fluency-evoking maneuvers, therapy, and the variability of speech output in stutterers.

Development and adult phase plasticity of syllable repetitions in the birdsong of captive zebra finches (Taeniopygia guttata)

Oscines learn their birdsongs from tutors. The authors found that a small fraction (approximately 7%) of captive male zebra finches (Taeniopygia guttata) produce variant acoustic birdsong profiles consisting of repetitions of single song syllables at high frequencies. Juvenile offspring of nonrepeaters can selectively learn the syntactic rule or habit of repeating syllables from repeaters. Adult tutored syllable repeaters, unlike spontaneous repeaters, undergo a form of song plasticity involving progressive reduction of the mean number and variance of repeated syllables as a function of long-term exposure to nonrepeater songs without altering the number or sequence of syllables within motifs. These findings suggest that aspects of song syntax or temporal frame can be acquired independently of song syllable or spectral content, and plasticity involving restorative alteration of acquired variant temporal frames can occur after the closure of the critical period for song learning.

Acoustic pattern variations in the female-directed birdsongs of a colony of laboratory-bred zebra finches.

The acoustic profile of the zebra finch song is characterized by a series of identical repeating units, each comprising a distinctive sequence of acoustic elements, called syllables. Here, we perform an analysis of song pattern deviations caused by variabilities in the production of song syllables. Zebra finches produce four different kinds of syllable variabilities-syllable deletions, single or double syllable insertions, syllable alterations, and syllable repetitions. All these variabilities, with the exception of repetitions, are present in songs of more than two-thirds of the normal adult birds; repetitions are present in less than one-fifth of birds. The frequency of occurrence of these variabilities is independent of the amount of singing, suggesting that they are unlikely to result simply from singing-induced physiological changes such as fatigue. Their frequencies in tutor-deprived birds are not significantly different from those in normal birds, indicating that they are unlikely to be acquired due to deficiencies in tutor-dependent learning. The types, patterns of occurrence and relative frequencies of these song syllable variabilities might reveal insights into the functioning of the song motor control pathway.

Nicotine-mediated plasticity in robust nucleus of the archistriatum of the adult zebra finch

Activation of neuronal nicotinic acetylcholine receptors (nAChRs) modulates the induction of long-term potentiation (LTP), a possible cellular mechanism for learning. This study was undertaken to determine the effects of activation of nAChRs by nicotine on long-term plasticity in the songbird zebra finch, which is a valuable model to study synaptic plasticity and its implications to behavioral learning. Electrophysiological recordings in the robust nucleus of the archistriatum (RA) in adult zebra finch brain slices reveal that tetanic stimulation alone does not produce LTP. However, LTP is induced by such stimulation in the presence of nicotine. The nicotine-mediated LTP is blocked by dihydro-beta-erythroidine (DHbetaE, 1 microM), an antagonist having a greater effect against nAChRs containing the alpha 4 subunit. In the presence of methyllcaconitine (MLA, 10 nM), an antagonist of nAChRs containing the alpha 7 subunit, a long-term depression (LTD) is unmasked, implicating a bi-directional type of plasticity in the zebra finch RA, which is modulated by differential activation of nAChR subtypes. Intracellular recordings from single neurons show a depression of the afterhyperpolarization (AHP) and an increase in frequency of evoked and spontaneous action potentials in the presence of nicotine. These results suggest that nicotinic cholinergic mechanisms may play a critical role in synaptic plasticity in the zebra finch song system and thereby influence song learning and plasticity.

Cerebral dominance and stuttering

The purpose of this paper is to review some of the salient aspects of cerebral dominance vis-a-vis stuttering. It is not my intention to profess knowing why people stutter or to claim any particular truthfinding mechanism. I present data pertaining to cerebral laterality in stutterers and conclude with how an altered state of cerebral laterality may contribute further understanding to some existing models of stuttering. The two hemispheres of the human brain are connected through interhemispheric pathways. They also receive information from, and send information to, the brainstem. Most of the programming and processing of language is done in the hemispheres. Almost all right-handed individuals have the majority of their language in their left hemisphere. A lesion in the left hemisphere of 99% of right-handed individuals results in aphasia; disease in the right hemisphere does not (with few exceptions). Individuals who are not right-handed probably have language in both hemispheres, the major component being in the left (reviewed in Benson and Geschwind, 1977; Goodglass and Quadfasel, 1964). It is not known how language comes to reside primarily in one hemisphere. Although morphology does not necessarily impute function, there are anatomical differences between the two hemispheres, especially in areas subserving language function (reviewed in Geschwind, Galaburda, and LeMay, 1979). Language is usually fairly well lateralized by the age of 8 yr (reviewed in Satz et al., 1975). It seems that the process of lateralization is still active at the time that a child is learning how to speak. At an early age, in fact through most of

Evaluation of the speech motor control system in amyotrophic lateral sclerosis

Summary We examined 162 amyotrophic lateral sclerosis patients and a subsequent group of 81 patients, addressing clinical aspects of bulbar dysfunction. All patients with deglutition complaints also had speech symptoms. The jaw jerk reflex and gag reflex had no relation to speech symptoms. Fundamental frequency ( F 0 ) range for /i/ failed to predict longevity. Patients without speech symptoms all spanned at least one octave in F 0 output. Tongue denervation on electromyography testing was not related to speech symptoms. Repetitive output of /pa/, /ta/, and /ka/, when performed at slow and fast rates, sometimes revealed substitution of voiced cognates as well as nasal consonants with the same place of articulation as for the voiceless stops, suggesting velopharyngeal dysfunction.

Disorders with Excessive Muscle Contraction: Candidates for Treatment with Intramuscular Botulinum Toxin (“Botox”)

The initial clinical use of local injections of type A botulinum toxin (botox) was for the treatment of strabismus.1 The intended goal was to block acetylcholinergic neuromuscular junctions and rebalance neural input to the extraocular rectus muscles; this enhanced convergence.2 Several drugs, including alpha-bungarotoxin, had been considered prior to botox, but each had limitations. These included lack of selectivity, undesired side effects, short duration of action, and substantial antigenicity. Botox has the advantage of being apotent neuromuscular blocking agent while not suffering as many limitations as other putative therapeutic agents.

Dynamic Characteristics of Vocal Frequency Tracking in Stutterers and Nonstutterers

The production of speech requires delicate coordination between laryngeal, articulatory and respiratory systems. Neurophysiology suggests that this coordination is achieved through the use of negative feedback control systems. That is, the central nervous system monitors proprioceptive feedback from these systems while it also monitors speech output through the auditory system. Actual speech output is compared to desired output, and corrective adjustments are made. Systems that use feedback (closed looped systems), like the CNS, are capable of much finer control than those that do not (open loop systems) because of their ability to monitor performance and make adjustments in their output. The price paid for this increase in performance is the possibility of the system becoming unstable, i.e., the adjustments that are made tend to degrade the performance rather than improve it. It is proposed to model stuttering as such an instability in the speech motor system. By studying the causes of these instabilities, we can understand the conditions leading to the production of a stuttered disfluency.

Modulation of θ/α frequency profiles of slow auditory-evoked responses in the songbird zebra finch

Abstract Spatiotemporal patterns of forebrain neural activity associated with auditory perception of biologically relevant complex acoustic stimuli can be conveniently studied in the songbird zebra finch. Here we present a time-frequency analysis of averaged slow auditory-evoked potentials (sAEPs) obtained at electrode locations overlying the main song control nucleus, high vocal center. Gabor spectrograms of these sAEPs show a prolonged response time course consisting of unimodal frequency peaks in the θ/α range (4–17 Hz). There is a stimulus-dependent modulation of the duration of the response and of the total number of its constituent frequency peaks, an effect that is bilateral in 75% of the birds and lateralized to the left side in the remaining 25%. Since the state of alertness of birds modulates these parameters along a similar continuum, these findings suggest that modulation of sAEP frequency profile may be dependent on attentional mechanisms. The presence and modulation of neurobiologically ubiquitous dominant frequency components also implicate the possible role of induced cerebral neuronal circuit oscillations in songbird auditory perception.