A reconsideration of bilateral language representation based on the intracarotid amobarbital procedure

Hemispheric language dominance was established for 368 epilepsy surgery candidates based on results of objective language performance during the intracarotid amobarbital procedure. Eight-three percent of patients were found to be left hemisphere dominant, while six percent were right dominant, and eleven percent demonstrated some degree of bilateral language representation. Bilateral patients were grouped according to modality-specific patterns of language performance in each hemisphere, with a majority demonstrating left hemisphere superiority in overall language processing. Variables affecting atypical language development are reviewed and results are considered in the context of previous research.     

MRI-radiofrequency tissue tagging in patients with aortic insufficiency before and after operation

We examined the relation between language dominance and regional cerebral blood flow (rCBF) during the intracarotid amobarbital procedure (IAP). A previous report limited to three patients suggested that dominant rather than nondominant hemisphere IAP may have a differential effect on rCBF. Behavioral assessment during the IAP also suggests that dominant hemisphere injection results in a differential effect on memory and affective symptoms rather than nondominant injection. Thirteen patients were assessed using single-photon emission CT (SPECT) brain imaging during both left and right IAP. The SPECTs were coregistered with the individual's MRI. Changes in rCBF during each IAP were compared with the patient's baseline SPECT. Nine patients had left hemisphere dominance, two were right dominant, and two had bilateral speech representation. In the left dominant subjects, left-hemisphere injection had a consistently greater effect on rCBF than right-hemisphere injection in the anterior (p < 0.005) and posterior (p < 0.01) temporal neocortex. There was also a trend for greater hypoperfusion in the frontal lobe of the left hemisphere. rCBF in the ipsilateral hippocampus was not significantly different after each injection (p > 0.05). In the two patients with right hemisphere speech, the reverse pattern was seen, with greater hypoperfusion after right (dominant) hemisphere injection. There was no consistent asymmetry in the two patients with bilateral speech. Dominant hemisphere IAP results in significantly greater hypoperfusion than does nondominant injection. These data provide a physiologic basis for behavioral differences noted after dominant versus nondominant IAP.     

Objective criteria for reporting language dominance by intracarotid amobarbital procedure

We propose a standardized method for reporting language lateralization by intracarotid amobarbital procedure (IAP). We retrospectively reviewed 165 IAPs, and classified language lateralization as left, right, or bilateral by three different methods, all based on the duration of speech arrest following each injection: absolute duration, side-to-side difference, and a "laterality index" defined as (L-R/L+R). Cutoff values were obtained by studying a pure subgroup of left hemisphere dominant right-handed subjects. In 142 patients (86%), the classification remained unchanged among all three methods: left in 112 (79%), right in 19 (13%), and bilateral in 11 (8%). In the other 23 patients (14%), language classification varied among the three criteria used. The change of category was never between left and right, and always involved bilateral language. Thus, this index may be helpful in standardizing and comparing IAP results from different series.     

Relation between intracarotid amobarbital memory asymmetry scores and hippocampal sclerosis in patients undergoing anterior temporal lobe resections

The intracarotid amobarbital procedure (IAP) is used to evaluate memory function preoperatively in candidates for anterior temporal lobe resections (ATL). We examined IAP memory asymmetry scores in 30 patients undergoing ATL (17 R, 13 L), as a function of the presence (HS+) or absence (HS-) of hippocampal sclerosis. Ictal onset zones were determined by extraoperative recording with subdural strip electrodes in all but 3 patients in whom magnetic resonance imaging (MRI) scan showed HS. MRI scans were otherwise normal. All patients were left hemisphere dominant for language except 1, in whom language was represented bilaterally. IAP memory testing involved presentation of eight subjects during anesthesia of each hemisphere, followed by recognition testing after patients recovered from amobarbital effects. A score of 1 was given for each correctly recognized object, and 0.5 was deducted for each false-positive identification. There were 16 foils. A total asymmetry score was calculated, which was positive if there was agreement between the direction of the symmetry and side of operation and negative if reversed. The mean asymmetry score for HS- (n = 8) was 0.9; that for HS+ (n = 22) was 4.1 (p < 0.01). IAP memory performance provided lateralizing information (asymmetry score > or = + or -2) in 73% of cases; among these, the lateralization was correct in 91%. Our data indicate that IAP memory asymmetry predicts both laterality of ictal onset and the presence of HS.     

Neuropsychology and pathology of the cerebral cortex

In all clinics we are faced with questions about certain aspects of cerebral dominance. We consider first the problem of recognition of faces where the right hemisphere plays a leading role. However, the disorders manifesting that function appear only bilateral lesions. This suggests that the left hemisphere participates in this process. The reception of language raises a problem which is analogous with the preceding: we propose the participation of both hemispheres in this activity: the left hemisphere is dominant in the analysis of phonemes and syntax, the right hemisphere seems implicated above all in the processing of prosodic aspects--in particular intonations and individual features of the voice.     

Reverse micellar extraction of antibiotics from aqueous solutions

PURPOSE: We reviewed 1,360 EEG reports for all patients studied in two different neurophysiology laboratories during 1 calendar year to determine whether epileptiform discharges have a hemispheric dominance. METHODS: Both inpatients and outpatients, with or without epilepsy, were included. RESULTS: Ninety-four records (6.9%) demonstrated generalized epileptiform activity. Of 95 EEG reports indicating spikes solely from one hemisphere, spikes arose from the left in 61 and from the right in 34. Among 50 other records with bilateral independent spikes with lateralization, 40 were left hemisphere dominant and 10 were right hemisphere dominant. CONCLUSIONS: These findings raise the possibility that the left cerebral hemisphere may generate focal epilepsy more frequently than the right.     

Preoperative predictors of anterior temporal language areas

OBJECT: Although it is known that 5 to 10% of patients have language areas anterior to the rolandic cortex, many surgeons still perform standard anterior temporal lobectomies for epilepsy of mesial onset and report minimal long-term dysphasia. The authors examined the importance of language mapping before anterior temporal lobectomy. METHODS: The authors mapped naming, reading, and speech arrest in a series of 67 patients via stimulation of long-term implanted subdural grids before resective epilepsy surgery and correlated the presence of language areas in the anterior temporal lobe with preoperative demographic and neuropsychometric data. Naming (p < 0.03) and reading (p < 0.05) errors were more common than speech arrest in patients undergoing surgery in the anterior temporal lobe. In the approximate region of a standard anterior temporal lobectomy, including 2.5 cm of the superior temporal gyrus and 4.5 cm of both the middle and inferior temporal gyrus, the authors identified language areas in 14.5% of patients tested. Between 1.5 and 3.5 cm from the temporal tip, patients who had seizure onset before 6 years of age had more naming (p < 0.02) and reading (p < 0.01) areas than those in whom seizure onset occurred after age 6 years. Patients with a verbal intelligence quotient (IQ) lower than 90 had more naming (p < 0.05) and reading (p < 0.02) areas than those with an IQ higher than 90. Finally, patients who were either left handed or right hemisphere memory dominant had more naming (p < 0.05) and reading (p < 0.02) areas than right-handed patients with bilateral or left hemisphere memory lateralization. Postoperative neuropsychometric testing showed a trend toward a greater decline in naming ability in patients who were least likely to have anterior language areas, that is, those with higher verbal IQ and later seizure onset. CONCLUSIONS: Preoperative identification of markers of left hemisphere damage, such as early seizure onset, poor verbal IQ, left handedness, and right hemisphere memory dominance should alert neurosurgeons to the possibility of encountering essential language areas in the anterior temporal lobe (1.5-3.5 cm from the temporal tip). Naming and reading tasks are required to identify these areas. Whether removal of these areas necessarily induces long-term impairment in verbal abilities is unknown; however, in patients with a low verbal IQ and early seizure onset, these areas appear to be less critical for language processing.     

Material-specific memory in the intracarotid amobarbital procedure

We examined material-specific memory in 45 left hemisphere language dominant patients with temporal complex partial seizures (24 right, 21 left) during the intracarotid amobarbital procedure (IAP) by showing eight cards displaying two line drawings of common objects, two printed words, one colored shape, one math expression, one face, and one abstract shape following amobarbital injection (mean = 109.9 mg). We assessed delayed recall and recognition following clearing. Patients with right foci recognized significantly fewer verbally mediated stimuli (words, object drawings, colored shape) with left than with right injection. Patients with left foci recognized a nonverbal stimulus (abstract shape) more poorly following right versus left injection. Discriminant function analysis lateralized 85% of the sample from memory predictors, upheld to 81% on crossvalidation. Material-specific memory remains intact in the hemisphere contralateral to a seizure focus, but wider representation may occur for stimuli normally dominant for the hemisphere with the seizure focus. The IAP significantly lateralizes a seizure focus with use of both types of stimuli.     

Making sense of cerebral dominance and syndromes of the nondominant hemisphere

Knowing the special function of each half of the brain is important to the clinician. If he doesn't understand what damage to the nondominant hemisphere can do, he may mistake the resulting syndrome for a psychiatric illness or generalized dementia, and the patient won't get proper treatment and counseling. The tendency is to think of dominance in terms of language, but other functions are asymmetrically located even though their input and output are bilateral. Generally, lesions in the left hemisphere cause problems with language and those in the right disrupt visual and spatial skills, attention, and emotional behavior. By far the most common syndrome in right hemisphere lesions is neglect of the left side. A patient may show lack of concern about his illness or he may deny that he is sick or even that the left side of his body belongs to him. Patients with left hemisphere lesions may neglect the right side but rarely to this extreme.     

A study of visual processes in a case of interhemispheric disconnexion

A 75-year-old right-handed woman, after a probable cerebral infarct, developed an irregular constriction of the visual fields, a left-sided agraphia, and an anomia for objects in the left hand. Subsequent testing demonstrated an inability to name, though ability to recognize, letters and objects flashed in the homonymous left visual field. An inter-hemispheric disconnexion syndrome was inferred from these findings. The present publication concerns mainly the visual aspects of this disconnexion syndrome. Tasks were devised to test the abilities of the major and minor hemisphere: (a) the left hemisphere demonstrated a complete dominance for language expression and an incomplete dominance for written language comprehension; (b) the right hemisphere appeared to be dominant for some visuo-spatial tasks including number comprehension; (c) when the hemispheres were given contradictory visual informations on a non-verbal task (chimeric stimuli) there was a predominance of the right hemisphere. The right hemisphere appeared able to process complex information. Specialization of functional activities in each hemisphere is briefly discussed.     

Neural organization of material-specific memory functions in temporal lobe epilepsy patients as assessed by the intracarotid amobarbital test.

Lateralization of material-specific memory processing was evaluated in 105 epilepsy patients undergoing the intracarotid amobarbital test prior to temporal lobectomy (TL). Left hemisphere (LH) language dominant patients demonstrated LH specialization for long-term verbal recognition memory and right hemisphere specialization for visuospatial recognition memory. The pattern of hemispheric memory specialization was similar for LH language dominant patients with brain injuries before 2 yrs of age and those without history of early brain injury, suggesting that the apparent sparing of memory post-TL in early brain injury patients reflects reorganization of memory functions within the epileptic hemisphere. Non-LH-language dominant patients showed no lateral specialization for either verbal or visuospatial memory processing, suggesting that in these individuals reorganization of memory functions between hemispheres accompanies the lateral shift in language representation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Modular organization of cognitive systems masked by interhemispheric integration

After resection of the corpus callosum, V.J., a left-handed woman with left-hemisphere dominance for spoken language, demonstrated a dissociation between spoken and written language. In the key experiment, words flashed to V.J.'s dominant left hemisphere were easily spoken out loud, but could not be written. However, when the words were flashed to her right hemisphere, she could not speak them out loud, but could write them with her left hand. This marked dissociation supports the view that spoken and written language output can be controlled by independent hemispheres, even though before her hemispheric disconnection, they appeared as inseparable cognitive entities.     

Successive activation of both cerebral hemispheres during cued word generation

Most humans have a left hemispheric dominance for language. However, during diagnostic language testing there also is activation of the right hemisphere, which is probably related to attention. To investigate further the role of attention during language production we monitored cerebral blood flow velocities in the middle cerebral arteries by continuous bilateral transcranial Doppler ultrasonography (TCD) in nine right-handed subjects. During cued word generation, a successive activation of the right hemisphere in the preparatory phase, and of the left hemisphere during word searching was demonstrated. These findings indicate that attentional processes precede verbal activation and that the two procedures can be separated by comparative blood flow velocity measurement.     

Semantic, phonological, and perceptual changes following left and right intracarotid injection (Wada) with a low amytal dosage

Intracarotid injection of a low dosage of amobarbital (75 mg, 5% solution) was studied in 30 temporal lobectomy candidates while naming achromatic, incongruously, and congruously colored pictorial objects and reading real, nonsense, and embedded words. Semantic errors and phonological alexia followed the left injection, while the right injection induced visuoperceptual errors. When the contralateral hemisphere was anesthetized, the left brain formulated supraordinate categories for words and objects, while the right brain applied concrete labels. The basic language proficiency of patients influenced recovery and outcome; left temporal patients who were interictally anomic performed especially poorly after both injections. Codifying phonological and perceptual changes during the intracarotid amobarbital procedure can improve interpretations about language laterality and organization.     

Tips for effective teaching

For all of us, one side of the brain, right or left, is the dominant hemisphere used to process information. In 9 out of 10 persons, the left temporal lobe becomes the dominant hemisphere. In the remaining one tenth of the population both sides develop at the same rate, forming "dual dominance," or, more rarely, the right side alone becomes highly developed. The left hemisphere of the brain serves as the analytical, sequential, cause and effect processor, whereas the right hemisphere of the brain is the mind's eye, assimilating information simultaneously and processing visual and nonverbal information and sound. Neither hemisphere works independently, and both are used to effectively learn new information. The creative teacher understands this arrangement and can successfully determine when a complex diagram or video is needed to teach a patient, or when only a clear voice is necessary.     

Language processing in aphasia: changes in lateralization patterns during recovery reflect cerebral plasticity in adults

During single word processing the negative cortical DC-potential reveals a left frontal preponderance in normal right-handers as well as in patients with a history of transient aphasia. Lateralization of DC-negativity therefore provides a reliable and robust method for the assessment of language dominance. In 11 stroke patients with permanent aphasia this physiological pattern changed to bilateral activation reflecting an additional right-hemispheric involvement in compensatory mechanisms in aphasia. Along with complete clinical recovery the classical aphasic syndromes revealed specific differences in changes of their lateralization patterns. In Broca's aphasia the initial right-hemispheric preponderance changed to a left frontal lateralization while in Wernicke's aphasia a presumably permanent shift towards the right hemisphere occurred. Differences in lateralization patterns might reflect different mechanisms of recovery such as the initial disinhibition of homologous areas contralaterally and subsequent collateral sprouting and synaptic modulation. The assessment of changes in lateralization of the cortical DC-potential during language tasks in a non-invasive, safe method with excellent time resolution that might provide further insights in the neural basis of recovery from aphasia.     

Language-related hemispheric asymmetry in healthy subjects and patients with temporal lobe epilepsy as studied by event-related brain potentials and intracarotid amobarbital test

There are current attempts to replace the WADA test for pre-surgical evaluation of hemispheric language capabilities by one of the methods of functional brain imaging. Recent PET and fMRI studies using verbal cognitive tasks like verb generation, semantic monitoring or semantic ('deep') encoding of words showed asymmetries of activation in the fronto-lateral cortex. In a previous ERP study subjects were required to indicate whether pronounceable non-words and abstract geometric figures were presented for the first time ('new item') or whether they had been shown before ('old item'). Group analyses of this study showed significant material-specific hemispheric asymmetries with ERPs being more negative-going in recordings of the posterior part of the left hemisphere with verbal material (CP5/6) but more negative-going in recordings of the right hemisphere with the spatial material (P7/8). The aim of the present study was to test statistically ERP lateralization effects in individual healthy subjects as well as WADA-tested patients suffering from seizures of the mesio-temporal lobe (MTL). In all subjects ERP lateralization with verbal material was tested in the electrode pair CP5/6, and ERP lateralization with figures in the electrode pair P7/8. Statistical analyses of single trials showed that in 20 out of 24 subjects ERPs with verbal material started to be more negative-going in CP5 as compared to CP6 in the period between 100 and 200 ms after stimulus onset or the subsequent time epoch (200-300 ms). In one subject not CP5/6 but the closely adjacent electrode pair P7/P8 showed this verbal material-related hemispheric effect. In patients language dominance as indicated by ERPs was not always consistent with the data of the WADA test. In one patient with left MTL seizures ERPs with verbal material and figures were found to be significantly lateralized to the right hemisphere although the WADA test assigned this patient to have a language-dominant left hemisphere.     

Hemispheric dominance in the processing of J.S. Bach fugues: a transcranial Doppler sonography (TCD) study with musicians

Although the majority of studies on musical processing in musicians observed a left hemisphere dominance which has usually been explained by a proficient analytical strategy used by these subjects, the findings are still inconsistent. Changes in hemispheric activity induced by listening to music (J. S. Bach fugues) and by recognizing the repetitions of the fugue theme were examined, using the technique of bilateral transcranial Doppler sonography (TCD) of the left and right middle cerebral artery (MCA). Subjects were 32 right-handed musicians, half of whom were members of an orchestra or members of a choir. The fugues were presented in two versions: a-cappella and instrumental. During passive listening to the a-cappella version, a weak left-dominant asymmetry of blood flow acceleration was observed, while there was no hemispheric asymmetry during listening to the instrumental version. During the task of fugue theme recognition, a highly significant asymmetry in favour of the right MCA was observed with both versions. It is concluded that when the processing of complex musical material has to be based on the analysis of melodic contour features and calls for working memory capacities a right hemisphere dominance is observed even in musically sophisticated subjects.     

Villoglandular adenocarcinoma of the cervix: cytologic presentation

A 69-year-old left-handed man developed Broca aphasia and jargon agraphia following a right cerebral infarction. He learned to write with his right hand. There is no family history of left-handedness. Neurological examination revealed hemiparesis, sensory impairment, and hyperreflexia with pathological reflexes on the left side. An MRI demonstrated lesions in the area including the pre- and post-central gyri, the posterior part of the middle and inferior frontal gyri, and inferior parietal lobule on the right side. Neuropsychologically he was alert and cooperative. He demonstrated severe Broca aphasia and his verbal output was limited to a few residual words. On the other hand, he could communicate through writing Kanji words. Writing words was relatively preserved with Kanji but not with Kana characters. Asked to write a Japanese folk tale, he showed jargon agraphia mixed with some correct Kanji words. His comprehension of spoken and written sentences was well preserved. He showed mild ideomotor and buccofacial apraxia, left unilateral spatial neglect, and constructional impairment. Dissociation between spoken and written language is a prominent feature of this patient's language output. In this patient, right hemisphere seems to be dominant for language and praxis, and left hemisphere for motor engram of writing. Learning to write with the right hand may have enhanced the establishment and maintenance of motor engram for writing in the left hemisphere. The intact motor engram of characters in the left hemisphere could be retrieved by the right hand without control from the language area in the diseased right hemisphere, resulting in jargon agraphia especially with Kana characters. In left handed people, the hand with which they learn to write may effect interhemisphere lateralization of language functions.     

Long-term subdural strip electrocorticographic monitoring of ictal déjà vu

We report a series of 8 patients with ictal déjà vu. Subdural strip electrocorticographic (ECoG) monitoring localized the ictal epileptogenic focus as follows: right (n = 6) and left (n = 2) mesiotemporal lobe. In all 8 patients, the left hemisphere was dominant for language function based on intracarotid amytal testing. In 6 right-handed patients, ictal déjà vu was associated with a right temporal lobe focus. However, in the 2 left-handed patients, the ictal focus was left temporal lobe. Although ictal déjà vu localizes the epileptic focus to temporal lobe, this experimental phenomenon appears to lateralize to the hemisphere nondominant for handedness.