Is recurrent perseveration a product of deafferented functional systems with otherwise normal post-activation decay rates?

Recent work in neuropsychology, clinical aphasiology and neuropharmacology have presented evidence that the causative substrates of recurrent perseveration in adults with aphasia are more recondite and subject to distinct interpretations than originally thought. This article will discuss and evaluate how various proposals from theory, from the clinic and from drug therapy interact and compete in the search for a cause or causes of recurrent perseveration.

Neurogenic stuttering: its reticular modulation.

Emerging neurologic evidence has suggested that developmental and acquired stuttering may have a cerebral base. Investigations have revealed compensatory activation in the right cortical motor areas and deactivation in the left perisylvian region in subjects with persistent developmental stuttering. The evidence has also implicated limbic (cingulate)-basal ganglia regions. Increased speech fluency with treatment in such subjects eliminated compensatory brain activity and shifted activation back to the left hemisphere. We assess the neurology of stuttering and then present our own observations of deep brain stimulation of the thalamus with some ameliorating effect on the encompassing syndrome with speech dysfluency.

Charles Darwin and the evolution of human grammatical systems.

Charles Darwin's evolutionary theories of animal communication were deeply embedded in a centuries-old model of association psychology, whose prodromes have most often been traced to the writings of Aristotle. His notions of frequency of occurrence of pairings have been passed down through the centuries and were a major ontological feature in the formation of associative connectivity. He focused on the associations of cause and effect, contiguity of sequential occurrence, and similarity among items. Cause and effect were often reduced to another type of contiguity relation, so that Aristotle is most often evoked as the originator of the associative bondings through similarity and contiguity, contiguity being the most powerful and frequent means of association. Contiguity eventually became the overriding mechanism for serial ordering of mental events in both perception and action. The notions of concatenation throughout the association psychology took the form of "trains" of events, both sensory and motor, in such a way that serial ordering came to be viewed as an item-by-item string of locally contiguous events. Modern developments in the mathematics of serial ordering have advanced in sophistication since the early and middle twentieth century, and new computational methods have allowed us to reevaluate the serial concatenative theories of Darwin and the associationists. These new models of serial order permit a closer comparative scrutiny between human and nonhuman. The present study considers Darwin's insistence on a "degree" continuity between human and nonhuman animal serial ordering. We will consider a study of starling birdsongs and whether the serial ordering of those songs provides evidence that they have a syntax that at best differs only in degree and not in kind with the computations of human grammatical structures. We will argue that they, in fact, show no such thing.

Walter Moxon, MD, FCRP (1836-1886): the cerebro-vascular system and the syndrome of "congestion of the brain": an analysis of his 1881 Croonian Lectures.

Walter Moxon, MD, FRCP lived, practiced medicine, taught and wrote in the mid- to late- nineteenth-century Victorian England, mostly at Guy's Hospital, London. He was widely informed in the "Art of Physic," writing on a range of issues from cerebral lateralization of articulate speech to angina pectoris. The present paper will trace briefly his contributions to the newly discovered asymmetry of articulate speech in the left frontal lobe (1866) and will in more detail trace and analyze his 1881 Croonian Lectures at the Royal College of Physicians on a medical shibboleth referred to as "congestion of the brain." In a series of ingenious and rhetorically creative arguments with imaginative tropes, demonstrations, evolutionary accounts of cognition and blood metabolism for human/biped cognition, and cogent citations from the medical literature of the day, Moxon skillfully instructs his medical audience against the misleading notion of cerebral "congestion" as an underlying pathology for cognitive, motor, and sensory deficits seen in the clinic. In so doing, he provides the medical community with an in-depth glimpse at the circulatory system, its flow dynamics, and how they serve to meet the cognitive, motor, and sensory demands of upright bipedal man.

Contextual variability in American English dark-l.

This paper presents a four-subject study that examines the relative influence of syllable position and stress, together with vowel context on the colouring of the dark-l characteristic of speakers of General American English. Most investigators report lighter /l/ tokens in syllable onsets and darker tokens in coda positions. The present study demonstrates that when dark-l serves as an onset in iambic intervocalic context with tautosyllabic high front vowels, it is fully dark as a result of domain-initial strengthening. By contrast, when dark-l is abutted across a word boundary to word-final or word-initial consonants, or when it is contained in a foot-internal context (preboundary intervocalic rime with trochaic stress) its dorsal gesture is constrained, resulting in less dark tokens. In the case of dark-l, articulatory undershoot must be understood not only in terms of the alveolar gesture, but also the dorsal gesture.

The Marc Dax (1770-1837)/Paul Broca (1824-1880) controversy over priority in science: left hemisphere specificity for seat of articulate language and for lesions that cause aphemia.

One of the most fascinating and frustrating issues in the priority of discovery in science is over just who, for the first time, went on record in the public forum, either orally at a conference or through a published communication, proclaiming that the faculty of articulate human speech was located in the left, not the right, cortical hemisphere. The disputed paper was purportedly written in 1836 by Marc Dax, who died subsequently in 1837. He was a physician in southern France in the city of Montpellier--far from the medical center of Paris. Little note was made of the presumed paper until the early and mid-1860s, when the issue of language localization in the human brain took on increased activity, as the clinico-pathological method of explanation continued to flourish in the "Art of Physick." Marc Dax's son, Gustave, happened to be studying medicine in Paris in the 1860s, and, as most of the neuroscientific and anthropological researchers, came to know of Broca's published work, which in 1861, agreed with phrenological theory that this faculty was, indeed, in the anterior lobes, but further claimed, de novo, that the region in the anterior lobe was more precisely focused at the foot of the 3rd frontal convolution in that lobe, still assuming with phrenological theory and the "Law of Symmetry" that the faculty was bilaterally located. It was not until 1865 that Broca clearly, non-hesitatingly, and unambiguously claimed that the faculty was in the left hemisphere. As it turned out, Gustave, six weeks before Broca's paper appeared, had published the paper he said his father had written in 1836. In 1863, in fact, Gustave had submitted his (Gustave's) long monograph on aphemia, integrating what he claimed to be his father's 1836 pronouncement along with his own data. He sent this communication to the French Academy of Sciences and to the French Academy of Medicine; he heard nothing back from either academy. After waiting two years, he managed to publish his material. Gustave's valiant move to promote his father's priority for one of the most significant conclusions in the history of the neurosciences is a lesson in frustration. Broca's attitude towards Gustave's case was disarmingly nonchalant; the issue deserves further historical inquiry.

Metrical/syllabic factors in English allophony: dark /l/.

This paper presents a single-subject case study illustrating the need to closely examine effects of dialect from syllable position on l-colouring, and the effects of domain-initial strengthening in General American English. Most investigators report lighter /l/ tokens in syllable onsets and darker tokens in coda positions in isolated words. The present study demonstrates an enhanced darkened onset /l/ in front vowel prosodic word (PW) boundaries, but lighter codas at PW-internal boundaries. We address the importance for clinicians of recognizing the impact of prosody on restructuring syntactic boundaries and its consequent effects on /l/ articulation.

Perseveration and other repetitive verbal behaviors: functional dissociations.

This article will review types of perseveration from a neurolinguistic perspective. During the course of the article, continuous, stuck-in-set, and recurrent perseveration will be placed in contradistinction to several other types of repetitive behaviors commonly associated with neurogenic communication disorders. These include echolalia in mixed transcortical aphasia; conduite d'approche and conduite d'ecart in fluent aphasias; lexical and nonlexical automatisms in nonfluent aphasias; palilalia in neuromotor disorders, such as Parkinson's disease (PD); and sound, syllable, word, and phrase repetitions in neurogenic stuttering. When differentiating these phenomena from perseveration, it is helpful to consider the salient factors that condition observed behaviors in individual patients, such as overall speech fluency, inventory of available utterances, nature of eliciting tasks, and propositionality of responses. Information such as communication disorder diagnosis, underlying etiology, and known sites of lesion from each patient's total clinical profile may also assist with differentiation.

Phonemic carryover perseveration: word blends.

This article will outline and describe the aphasic disorder of recurrent perseveration and will demonstrate how it interacts with the retrieval and production of spoken words in the language of fluent aphasic patients who have sustained damage to the left (dominant) posterior temporoparietal lobe. We will concentrate on the various kinds of sublexical segmental perseverations (the so-called phonemic carryovers of Santo Pietro and Rigrodsky) that most often play a role in the generation of word blendings. We will show how perseverative blends allow the clinician to better understand the dynamics of word and syllable production in fluent aphasia by scrutinizing the "onset/rime" and "onset/superrime" constituents of monosyllabic and polysyllabic words, respectively. We will demonstrate to the speech language pathologist the importance of the trochee stress pattern and the possibility that its metrical template may constitute a structural unit that can be perseverated.

Walter Moxon and his thoughts about language and the brain.

Walter Moxon wrote a well-timed paper in 1866 on aphemia with accompanying right sided hemiplegia. Like many other investigators of this apparent lopsidedness of the articulatory system for human speech. Moxon had to reconcile left hemisphere specialization for this function with the overriding law of symmetry, which for a large sector of the scientific community was a sine qua non of the anatomy and function of high level animal cognition. His reasoning was essentially that since the right dominant hand (and hence the left hemisphere) in some sense led overall bilateral limb movement patterns, that the right side of the tongue would lead whole tongue movement for articulation, the left side following in some mechanical sense. Thus, Moxon could link left hemisphere dominance for handedness as well as for speech. His theory was that "attention" was focused on the left hemisphere during limb movement development, under his assumption that the articulators were limbs as well as the arms and hands. The present paper will examine the professional life of Moxon and his 1866 paper, as well as the scant commentary that it has elicited in the literature on the history of left hemisphere dominance for the human articulatory function.

Does the right hemisphere take over after damage to Broca's area? the Barlow case of 1877 and its history.

In 1877 Thomas Barlow, a London physician, published a remarkable case of functional recovery of speech following brain damage. It involved a 10-year-old boy who had lost his speech, regained it, and lost it again before he died from a disorder that affected his heart and produced embolisms that subsequently affected other organs, including his brain. Examination of the boy's brain revealed two focal regions of softening; one that affected Broca's area and the left facial-motor area, and another, which occurred weeks later, in the homologous regions of the right hemisphere. Although Barlow was most concerned with motor deficits, others at the turn of the century began to cite this case as strong evidence that the corresponding region of the right hemisphere can take over speech functions for Broca's area on the left. Whether this case really provides good support for functional takeover or vicariation theory is critically evaluated in the light of contemporary research, including PET scan studies involving damage to Broca's speech region.