Cerebral Dominance For Speech Research Articles

Lateralization of Speech Production Starts in Sensory Cortices—A Possible Sensory Origin of Cerebral Left Dominance for Speech

Speech production is a left-lateralized brain function, which could arise from a left dominance either in speech executive or sensory processes or both. Using functional magnetic resonance imaging in healthy subjects, we show that sensory cortices already lateralize when speaking is intended, while the frontal cortex only lateralizes when speech is acted out. The sequence of lateralization, first temporal then frontal lateralization, suggests that the functional lateralization of the auditory cortex could drive hemispheric specialization for speech production.

Cerebral Asymmetries: Complementary and Independent Processes

Most people are right-handed and left-cerebrally dominant for speech, leading historically to the general notion of left-hemispheric dominance, and more recently to genetic models proposing a single lateralizing gene. This hypothetical gene can account for higher incidence of right-handers in those with left cerebral dominance for speech. It remains unclear how this dominance relates to the right-cerebral dominance for some nonverbal functions such as spatial or emotional processing. Here we use functional magnetic resonance imaging with a sample of 155 subjects to measure asymmetrical activation induced by speech production in the frontal lobes, by face processing in the temporal lobes, and by spatial processing in the parietal lobes. Left-frontal, right-temporal, and right-parietal dominance were all intercorrelated, suggesting that right-cerebral biases may be at least in part complementary to the left-hemispheric dominance for language. However, handedness and parietal asymmetry for spatial processing were uncorrelated, implying independent lateralizing processes, one producing a leftward bias most closely associated with handedness, and the other a rightward bias most closely associated with spatial attention.

Visual half-field testing for defining cerebral hemisphere speech laterality

The purpose of this study was to investigate to what extent the noninvasive visual half-field (VHF) test can reliably determine cerebral speech dominance for the individual patient with partial epilepsy considered for surgical treatment. The present VHF test consisted of a list of 36 words presented correctly and mirrored in the lateral visual fields to 13 right-handed and 14 left-handed control subjects and to 14 right-handed and 2 left-handed patients with partial epilepsy. In the controls, it was found that all right-handed and 10 out of 14 left-handed control subjects showed a right VHF (i.e., left hemisphere) advantage. Three of the left-handed control subjects showed the opposite pattern, and one showed no visual field advantage. All of the right-handed patients showed a right VHF advantage, except one who showed no VHF advantage. The two left-handed patients had both a left VHF advantage. Intracarotid amytal speech testing documented left hemisphere speech dominance in all right-handed patients. Of the two left-handed patients, one had right-sided, the other bilateral speech representation. The results suggest that the present VHF test reliably predicts cerebral hemisphere speech in patients with epilepsy.

The Preservation of Consciousness, Automatism, and Movement Control

Back to table of contents Previous article Next article LetterFull AccessThe Preservation of Consciousness, Automatism, and Movement ControlIraj Derakhshan, Iraj DerakhshanSearch for more papers by this author, Charleston, WVPublished Online:1 Nov 2003AboutSectionsPDF/EPUB ToolsAdd to favoritesDownload CitationsTrack Citations ShareShare onFacebookTwitterLinked InEmail SIR: The paper by Devinsky et al.1 contains important laterality indexed information concerning the preservation of consciousness, automatism, and movement control, which deserve to be put in a more cohesive perspective. This in turn could have helped to present the data in a more scientific manner. Specifically, I am referring to the works of Serafetinides2 on the role of the major hemisphere in preservation of consciousness and Serafetinides and Falconer3 on the role of the right (minor) hemisphere in speech automatism. The results of these large numbered and meticulously conducted studies have been confirmed in more recent times,4,5 all indicating that when a seizure occurs with speech arrest, loss of consciousness, and presence of memory of preictal events, the lesion is in the major hemisphere. As these authors recorded epileptiform EEG activity in such patients the process is epileptic by definition, and calling the process convulsive is appropriate in those in which actual convulsion is seen (majority occurring in major hemispheric lesions). To a neurologist, “nonepileptic seizure” is an oxymoron. Of course, “hysterical seizures” do occur, but if the behavior is associated with the rest of the items enumerated above and is seen with a brain lesion in either hemisphere, one must avoid using that confused and confusing terminology.The role of laterality of movement control (alluded to above, and codified in handedness) in maintaining the stream of conscious awareness is becoming clearer. The activating neuronal aggregate devoted to voluntary movements (otherwise called the command center in the major hemisphere) has been recently the subject of an investigation based on a review of the literature and my own data. This ensemble mediates interlimb coordination, guaranteeing the existence of a cohesive self in a brain consisting of two hemispheres. It is only when this asymmetrical interhemispheric relationship is disturbed, such as in surgical callosotomy, Marchiafava-Bignami disease, and traumatic or vascular callosotomy, that the cohesion is lost forever. Cases of ictal automatism, as mentioned above, are instances representing temporary disruption of this cohesion. All references cited indicate that only when the activating moiety (within the major hemisphere) is involved in the epileptogenesis will the person lose consciousness, as the disruptive process is conveyed to the remaining hemisphere via the callosum. Epileptic activity generated within the minor hemisphere is the source of automatisms only, as mentioned above. It cannot be generalized because the callosal traffic for movement is one-way only. This recently described anatomy forms the neural basis for handedness.6 One of its manifestations is the melody lead of the piano players that has been known to musicologists for more than a century. The reason for the delay of all effectors on the left side (in right handers) is the time taken for the command in the major hemisphere to reach the motor cortex on the right via the callosum.References1 Devinsky O, Mesad, S, Alpers K. Nondominant hemisphere lesions and conversion nonepileptic seizures. J Neuropsychiatry Clin Neurosci 2001; 13:367–373Link, Google Scholar2 Serafetinides EA, Hoare RD, Driver MV. Intracarotid sodium amobarbitone and cerebral dominance for speech and consciousness. Brain 1965; 88:107–130.Crossref, Medline, Google Scholar3 Serafetinides, EA, Falconer MA. Speech disturbances in temporal lobe lesions: A study in hundred epileptic patients submitted to anterior temporal lobectomy. Brain 1963; 86:333–346Crossref, Medline, Google Scholar4 Ebner A, Dinner DS, Noachtar S, Luders H. Automatism with preserved responsiveness: A lateralizing sign in psychomotor seizures. Neurology 1995; 45:61–64Crossref, Medline, Google Scholar5 Karlov VA, Selitskii GV, Sviderskaya NE: The trigger role of the left cerebral hemisphere in the generalization of epileptic activity. Neurosci Behav Physiol. 1993; 23:280–289Google Scholar6 Derakhshan I. In defense of the sinistrals: Anatomy of handedness and the safety of prenatal ultrasound. Obstet Gynecol 2003; 21:209–212Google Scholar FiguresReferencesCited byDetailsCited ByElectroencephalogram and Laterality of Movement Control: A Clinical Analysis2 July 2016 | Journal of Child Neurology, Vol. 18, No. 12 Volume 15Issue 4 November 2003Pages 456-456 Metrics PDF download History Published online 1 November 2003 Published in print 1 November 2003

Handedness and cerebral dominance: the right shift theory.

In a BBC radio program called “The Brain’s Trust,” the philosopher C.M. Joad typically began his answers with, “It all depends on what you mean by ‘x’.” Neglect of this proviso for “handedness” has serious consequences. Here are two examples. The argument for earlier mortality in leftthan right-handers depends on the premise that relative frequencies have not changed over this century. An early study classified 15.7% of students as left-handed but did not explain the criterion. Lefthanded writing has certainly changed, such that leftwriters today are younger on average than right-writers. Left-handers were 9 years younger among the recently deceased in California, but they are also 9 years younger among the living in the United Kingdom. The second example concerns cerebral dominance for speech (CD). No right-handers were found among aphasics with right-sided lesions in two influential series, but in both series the proportion of left-handers among all aphasics was considerably higher than among all nonaphasics, suggesting that the absence of right-handers among right-lesioned aphasics was due to generous criteria of left-handedness in critical cases. The right shift (RS) theory was founded on empirical study of types of handedness. This review aims to describe my approach to classification, outline its theoretical implications, point up some contrasts with other theories, and persuade readers to examine their data as needed for critical tests.

Gustave Dax and his fight for recognition: an overlooked chapter in the early history of cerebral dominance.

The year 1865 was revolutionary in neuroscience. In this year, three papers were published on the topic of cerebral dominance for speech. These papers were authored by Paul Broca, Marc Dax, and Gustave Dax, and they contributed to a priority debate that cannot be easily resolved. Gustave Dax claimed that his long dead father had written a memoir and presented it orally in Montpellier in 1836, thus making him the first person to write about cerebral dominance. He also claimed that he was the second person to write on the subject, the first to support his father's claims, and the first to try to localize the center for speech in just one part the left hemisphere, the middle (temporal) lobe. Paul Broca, however, was now getting much of the credit for these discoveries. To set the record straight, Gustave published several letters. This paper presents translations of Gustave's letters of 1866, 1875, and 1877, as well as the historical note written by Raymond Caizergues in 1879, and recreates the events that triggered the younger Dax's anger.

Ictal Speech Manifestations in Temporal Lobe Epilepsy: A Video‐EEG Study

To evaluate ictal speech manifestations in complex partial seizures (C PS), we reviewed videotapes of 68 consecutive patients who underwent anterior temporal lobectomy (ATL) for treatment of intractable epilepsy in Taiwan. In all, 261 CPS were collected from their video-EEG (VEEG) recordings. Cerebral speech dominance was determined by intracarotid injection of sodium amobarbital (Wada test) in all cases. Ictal speech manifestations, classified as verbalization or vocalization, occurred in 32 patients (47.1%) with 96 seizures (36.8%). Ictal verbalization occurred in 10 patients (14.7%). Ictal vocalization was observed in 28 patients (41.2%); including 6 patients who also had ictal verbalization. Thirty-six patients (52.9%) had no seizure with ictal speech manifestations. Ictal verbalization had significant lateralization value: 90% of patients with this manifestation had seizure focus in the nondominant temporal lobe (p = 0.049). Seizures of patients with ictal vocalization were not more likely to arise from either temporal lobe. We also observed bilingual patients who exclusively spoke in their mother tongue (Taiwanese) rather than the acquired language (Mandarin) in 72.2% of seizures with verbalization. This finding is significant and contrary to a commonly held notion that the acquired language is used in seizures associated with speech behaviors.

Predicting cognitive impairment in epilepsy: findings from the Bozeman epilepsy consortium.

We examined the contribution of age of seizure onset, seizure duration, seizure laterality, seizure location, gender, handedness, and cerebral speech representation to cognitive attainment in 1,141 patients with medically refractory seizures. The combined influence of the predictor variables was modest. Age of seizure onset was the best single indicator of Full Scale IQ (partial r = .23) and General Memory (partial r = .20). Laterality and location of dysfunction, and cerebral speech dominance were also relevant and independent indicators of aspects of cognition. Except for age of onset of seizures (early onset was associated with poorer cognitive attainment), however, the magnitude of the effects was limited.

Cerebral dominance for speech and handwriting of patients with cortical vascular malformations.

Lateralization of speech dominance was established using amobarbital for 22 patients with vascular malformations lateralized to the left cerebral hemisphere. Patients' histories were negative for clinically evident neurological events (e.g., seizures or hemorrhage) prior to adulthood. The vascular lesions were categorized as high flow arteriovenous malformations (AVMs) (n = 4), low flow AVMs (n = 6), cavernous hemangiomas (n = 10), or venous angiomas (n = 2) by reviewing angiographic findings and surgical pathology for those patients whose lesions were excised. Three of the malformations encroached upon primary language areas. The frequency of right hemisphere speech dominance was not significantly elevated in comparison with the normal population, even though the incidence of nonright-handedness was. Ninety-five percent of the patients were left hemisphere dominant for speech: only one patient, with a parietal lobe cavernous hemangioma, was found to be right hemisphere dominant for speech. This malformation did not involve the primary language areas. These findings suggest that vascular malformations do not affect speech dominance as readily as other neurological diseases, but frequently affect manual dominance.

Marchiafava-Bignami Disease, Syndrome of Interhemispheric Disconnection, and Right-handed Agraphia in a Left-hander

We present an original case of Marchiafava-Bignami disease in a 47-year-old left-handed alcoholic man. Computed tomography and magnetic resonance imaging demonstrated the typical lesion, a necrosis of the middle portion of the corpus callosum. Diagnosis may thus be established in the living. In our case, the course was not fatal, which, to our knowledge, has only been described in four other cases in the literature. Clinically, our patient demonstrated an interhemispheric disconnection syndrome. The striking feature is that some of the symptoms were on the side opposite of the one that has previously been described in the literature, eg, right-handed agraphia, while others were on the usual side, eg, left-handed anomia. We discuss cerebral dominance for speech and handedness in left-handers and come to the conclusion that our patient's clinical features can only be explained by right hemispheric dominance for handedness and bilateral hemispheric representation of speech.

Activation of the epileptic focus during intracarotid amobarbital test. Electrocorticographic registration via subdural electrodes

During presurgical evaluation, bilateral intracarotid amobarbital tests were performed in 21 patients (42 tests) to establish the lateralization of cerebral speech dominance as well as memory function. All patients suffered from long-standing, medically intractable, complex partial seizures. Electrocorticographic recording during the investigation was carried out via bilaterally implanted subdural electrodes. The aim of the study was to assess amobarbital-induced effects on the primary epileptic focus, determined throughout presurgical evaluation. Following the application of amobarbital the primary epileptic focus was selectively activated in 10 and preferentially activated in 3 patients suffering from temporal lobe epilepsy. Specific responses of the primary epileptic focus consisted of: (i) induction of a spike-burst-suppression pattern, mainly in the mesio-basal aspects of the focal temporal lobe (n = 13); (ii) induction of spikes or sharp waves following contralateral intracarotid injection (n = 10); (iii) late induction of spikes or sharp waves following ipsilateral injection (n = 4); (iv) loss or marked reduction of drug-induced β activity over the primary epileptic focus (n = 14) following ipsilateral or contralateral injection. In conclusion, electrocorticographic recording during the intracarotid amobarbital test contributes valuable information about the primary epileptic focus in a high proportion of patients.

The corpus callosum is larger with right-hemisphere cerebral speech dominance.

Variations in the size of the human corpus callosum were examined as a possible morphological substrate of functional asymmetries of the cerebral hemispheres, such as cerebral speech dominance. The midsagittal surface area of the corpus callosum, obtained by magnetic resonance imaging, was measured in 50 patients with epilepsy and 50 neurologically normal control subjects. The mean callosal area did not differ significantly between patients and control subjects, between left-handed and right-handed subjects, or between men and women. When measurements were compared among 44 patients, whose cerebral speech dominance had been determined by the intracarotid injection of sodium amytal, the area of the corpus callosum was significantly greater in patients with right-hemisphere cerebral speech dominance. The mean callosal area was greater by 109 to 159 square millimeters (18-28%) when compared to that of patients with either left-hemisphere speech dominance or bilateral speech representation. This difference in midsagittal surface area could represent as many as 37 to 54 million additional callosal axons in subjects with right-hemisphere cerebral speech dominance.

Hand preference and proficiency and cerebral speech dominance determined by the carotid amytal test.

Epileptic patients whose speech dominance had been determined with the carotid amytal test were given tests of hand preference, strength, and dexterity. A Discriminant Function Analysis applied to the data correctly identified the side of speech representation in 89.5% of the sample.

A study on handedness and cerebral speech dominance in right-handed Chinese

Abstract The handedness of Chinese schoolchildren and adults was examined with nine test items; the former group was also surveyed using a questionnaire. The prevalence rate of left-handers was about 3.5% for both schoolchildren and adults. This result strongly suggests that handedness is established in childhood. A study of cerebral speech dominance in 94 right-handed Chinese by means of a Wada test showed that the dominant hemisphere was on the left side in 92 patients and on the right in the remaining two. Thirty of the 94 patients with surgical lesions in the sylvian region were operated upon, and the reliability of the Wada test was demonstrated in each case. It is concluded that in the great majority, but not all, of right-handers the left cerebral hemisphere is dominant for speech. A study of 55 right-handed aphasic patients with surgically verified lesions showed the following: 1. The lesions were invariably found around the sylvian fissure, on the left in 53 and on the right in two. 2. Nominal aphasia was most frequent (32/55), with lesions any where around the Sylvian fissure. 3. Motor aphasia was relatively frequent (20/55), with lesions solely in the anterior sylvian region. 4. Sensory aphasia was rare (3/55), with lesions in the posterior sylvian region. In this study the patients undergoing the Wada test were all, right-handed. No satisfactory explanation for this absence of left-handers has yet been found.

Visual laterality effects and cerebral speech dominance determined by the carotid amytal test

Epileptic patients whose speech dominance had been ascertained using the carotid Amytal test were given a verbal-visual half-field task. Patients with left-hemisphere speech dominance, like normal controls, tended to show a RVF effect whereas patients with atypical speech patterns showed a bias in favor of the LVF.

Broca on the relation between handedness and cerebral speech dominance

Broca on the relation between handedness and cerebral speech dominance

Writing Hand Posture and Cerebral Dominance for Speech

Levy and Reid's claim (1976, 1978) that writing hand/posture is predictive of cerebral dominance was examined in patients who had undergone bilateral sodium Amytal speech testing. Contrary to their prediction, inverted writers showed the same pattern of speech representation as did straight writers.

Sensory cortical tongue representation in man.

Extensive data on cortical tongue representation were analyzed in 100 patients who underwent craniotomy and cortical mapping by electrical stimulation for surgical treatment of epilepsy. As noted in the literature, the tongue is extensively represented within the central nervous system with a highly organized sensorimotor system and the data from this study corroborate a large cortical representation of the human tongue over the postcentral gyrus. The tongue was found to have a clear somatotopic organization over the postcentral area and to be represented bilaterally to a significant degree. Furthermore, the tongue appears to have an asymmetrical sensory cortical representation, as cerebral dominance for speech is more extensively represented on the dominant hemisphere. Cortical tongue mapping has proved extremely useful in determining the point of junction of the central and Sylvian sulci, a crucial landmark during surgical cortical resections.

Lateral Preferences and Cerebral Speech Dominance

Four types of lateral preference (hand, foot, eye, ear) were measured in 73 patients, who underwent sodium Amytal speech testing. In 63 cases, speech was on the left side whereas in 10, speech was on the right.All of the patients with right hemisphere lesions had speech represented in the left hemisphere. Only a third of the patients with left hemisphere damage prior to the end of the first year of life continued to have speech on the left side. By contrast, 82% of those with left hemisphere damage after this sensitive period had speech exclusively mediated by the left hemisphere. In short, the occurrence of right hemisphere speech dominance without an early lesion to the left hemisphere is rare.The majority of patients with right-sided motor and sense organ preferences had speech represented in the left hemisphere, independent of location or age of onset of the damage. By contrast, in individuals with a clinical history of early left hemisphere injury, left-sided motor and sense organ preferences were linked to right hemisphere speech dominance. In those cases without evidence of early cerebral damage, most of the non-right-sided individuals had speech in the left hemisphere. However, the proportion of unilateral, left hemisphere speech representation in the right-handed and right-footed was higher than that observed in the left-handed and left-footed, even when those with early onset of damage were excluded from analysis. It was suggested that in the normal population, handedness and footedness are relevant factors in predicting cerebral speech dominance. Knowledge of eye and ear preference may be of little predictive value. Further, in a neurological population the overall congruency across the four patterns of lateral preference may provide useful information regarding cerebral speech dominance.A small group (5) of patients with bilateral representation of speech was also examined. Contrary to the experience at the Montreal Neurological Institute, most of these patients preferred the right limb and sense organ. Differences in investigative approach may account for the conflicting observations.

Language function and dysfunction among Chinese- and English-speaking polyglots: Cortical stimulation, Wada Testing, and clinical studies

Language functions in a group of Chinese- and English-speaking polyglots living in a multiracial society have been investigated by several methods: the effects of cortical stimulation on object-naming and reading tasks in patients who required awake craniotomy, lateralization of cerebral dominance for speech by the Wada Test, and the pattern of language loss and recovery following stroke. The data indicate that these polyglots were all left hemisphere dominant for the languages tested; no consistent evidence for increased participation by the right hemisphere for language functions was found. The cortical stimulation experiments provided data most compatible with the “differential localization” model of cerebral localization in bilingualism. The variable which most influenced performance in all of these investigations was which language was used primarily for speaking as well as reading and writing at the time of the study.