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.     

Visual and semantic processing in reading Kanji.

A. Nakagawa (see record 1992-15549-001) showed hemispheric asymmetries during semantic processing of single English words. The right hemisphere passively maintained both strong and weak associations, whereas the left hemisphere maintained only strong associations when Ss were left free to attend. The present study extends the methodology to the study of Kanji characters. Contrary to the study of English characters, there was a general right-hemisphere advantage in single-character Kanji words. A study using a visual cue to direct attention suggested that the right-hemisphere advantage of Kanji was due to better representation of visual features by the posterior right hemisphere. However, the pattern of semantic priming found in English was replicated. Semantic analysis, mediated by more anterior systems, appears similar in the 2 languages. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Spatial relationships of electrical activity during reproduction of verbal signals in children

The study of intercentral correlations of the brain biopotentials in five-to six year old children revealed considerable differences in the spatial distribution of interrelations of the neocortex projection and associative zones during reproduction of familiar and unfamiliar words. Reproduction of familiar words was accompanied by the greatest enhancement of interrelations of associative structures (infraparietal, frontal areas and Broca speech centre) with projection zones of the motor and acoustic analysers in the left hemisphere, while reproduction of unfamiliar words was attented with closer connections of the projection motor zone with the temporal and the anterior associative (frontal and speech) zones in the right hemisphere. The facts obtained testify to the existence of the interhemispheric asymmetry and to the different involvement of the neocortex projection and associative zones in the organization of motor speech in children.     

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.     

The complexities and pitfalls of working with the countertransference

Left unilateral spatial neglect (USN) and spatial agraphia are both caused by right hemisphere damage. However, effects of USN on spatial agraphia have not been fully investigated. This study examined performances of patients with or without neglect and normals on single letter writing, using Japanese unique writing systems, kana (phonogram) and kanji (ideogram). Our patients exhibited agraphia of kanji, but not of kana. However, accuracy of writing was not associated to neglect severity, and errors for writing to dictation occurred either on the left or right side of kanji. Right frontal damage seemed to be related to the genesis of duplication or omission errors of repeated elements. Effect of USN was limited to spatial arrangement of letters and copying performance.     

Tachistoscopic recognition of Kana and Hangul words, handedness and shift of laterality difference

Nonsense Kana words as verbal stimuli and Hangul words (Korean orthographic characters) as non-verbal were presented tachistoscopically in the left or right visual field to normal right-handed, non-familial left-handed Japanese subjects, who have not seen Hangul characters. Right-handers showed a significant right (or left) field superiority for the recognition of verbal (or non-verbal) stimuli. This pattern of differences found in right-handers is, though to a slightly lesser degree, also present in non-familial left-handers, while it is absent in familial left-handers. Initial left field superiority for Hangul word recognition shifted to no laterality difference in left-handers as well as in right-handers during the learning period for Hangul words.     

Multiwell 14CO2-capture assay for evaluation of substrate oxidation rates of cells in culture

The functional anatomy of the interactions between spoken language and visual mental imagery was investigated with PET in eight normal volunteers during a series of three conditions: listening to concrete word definitions and generating their mental images (CONC), listening to abstract word definitions (ABST) and silent REST. The CONC task specifically elicited activations of the bilateral inferior temporal gyri, of the left premotor and left prefrontal regions, while activations in the bilateral superior temporal gyri were smaller than during the ABST task, during which an additional activation of the anterior part of the right middle temporal gyrus was observed. No activation of the occipital areas was observed during the CONC task when compared either to the REST or to the ABST task. The present study demonstrates that a network including part of the bilateral ventral stream and the frontal working memory areas is recruited when mental imagery of concrete words is performed on the basis of continuous spoken language.     

A case of porencephaly with mirror movements: pathophysiological investigation by using long-latency long-loop reflex and dipole tracing method

We report a 42-year-old left-handed woman with congenital right hemiparesis and bilateral mirror movements in the hands. She had a porencephaly of the left hemisphere and the brain MRI demonstrated cortical and subcortical defect of the left hemisphere from Brodmann's area 6 to 40 including the left motor cortex. By electrical stimulation of the left median nerve at the wrist, N20 of the somatosensory evoked potential was recorded in the right postcentral gyrus by using the dipole tracing method. Long-loop reflexes from the bilateral thenar muscles were recorded and their latencies were almost the same. The stimulation of the right median nerve did not evoke N20, nor long-loop reflex. These electrophysiological findings suggest that the reorganization of the motor system made the right motor cortex to innervate bilateral hands, and caused bilateral mirror movements. In other words, the mirror movements managed to relieve the paralysis of the right hand though the damage of the left motor cortex was present. In the previous literature we are able to find hypotheses regarding the mechanism of mirror movements in congenital hemiparesis. Here we discussed about the reorganization of the motor system in the damaged brain.     

Functional organization of the right nondominant cortex: Evidence from electrical stimulation.

Studied discrete functional localization for visuo-perceptual, spatial, and nonverbal memory tasks in conjunction with focal electrical stimulation of the exposed right-dominant cortex during awake craniotomies in 22 patients. Results provide evidence for discrete functional localization in the right, nondominant hemisphere. Performance on each task was significantly impaired in association with stimulation of some, but not all, sites in comparison with performance on nonstimulation control trials. There was, generally, a strong dissociation of sites involved in separate functions across individual Ss. Contrary to the notion of diffuse functional organization in the nondominant hemisphere, visuospatial functions in the right hemisphere appear to be as discretely localized as verbal functions in the left hemisphere. Language and language-related functions of naming, reading, short-term verbal memory, nonverbal oral-facial movement, and phonemic identification were assessed in a subgroup of 10 Ss in conjunction with right nondominant cortical stimulation. In right-handed Ss, no disruptions of these tasks were seen with stimulation of sites outside the right face motor cortex itself. In 2 case studies, there was evidence for right cortical involvement in the mediation of 2 nonphonetic symbol-based language systems: Japanese Kanji and Fortran. (French abstract) (72 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Sex differences in oral asymmetries during wordrepetition

During speech production the right side of the mouth is opened to a larger degree in most people. This facial asymmetry is thought to be related to a left hemisphere dominance in language processing and/or motor programming. We investigated asymmetrical lip separations during discrete or serial word productions in right handed persons. The results revealed a right sided lip separation bias in both genders during discrete word production in which the words had to be uttered once. As soon as the words had to be produced continuously, however, a clear sex difference appeared with males having the usual right bias but females now showing no clear asymmetry, with a tendency for larger lip separations on the left side. These results suggest the existence of two separate neural systems from which one controls the discrete task and which is left hemisphere dominant in both genders. The other is probably involved in serial word productions and shows a sex difference with regard to its asymmetry pattern.     

Diffuse proliferative lupus nephritis in a patient with ulcerative colitis

PURPOSE: To compare activation of the ipsilateral cerebral hemisphere during tactile sensory and motor tasks involving the right and left hands. METHODS: Eight volunteers had functional MR imaging to measure the extent of cerebral hemisphere activation during a motor task and sensory task involving each hand. Hemispheric indexes (left hemisphere activation minus right hemisphere activation)/(left hemisphere activation plus right hemisphere activation) were computed for each hand and each task. The indexes for two tasks and the two hands were compared. RESULTS: The left-hand motor tasks activated the ipsilateral hemisphere in right handers significantly more than did the right-hand tasks. Motor tasks produced a greater activation of the ipsilateral hemisphere than did the sensory tasks. No significant differences were found between the hemispheric indexes for the right-hand and left-hand sensory tasks. CONCLUSION: This study confirms findings of a previous study, showing that the left hemisphere is active in left-hand motor tasks. Activation of the ipsilateral hemisphere is significantly less pronounced during sensory tasks than during motor tasks.     

Receptor tyrosine kinase expression in human bone marrow stromal cells

A case of crossed aphasia is presented in a strongly right-handed 77-year-old white female without history of familial sinistrality or prior neurological illness. She developed a right middle cerebral artery infarction documented by CT and accompanied by obvious clinical signs of a conduction aphasia with some resolution but continuing obvious language defect after 9 weeks in rehabilitation. Comprehensive neuropsychological and aphasia testing suggested anomalous lateralization of phonologic-output aspects of language, emotional prosody, motor planning and body schema modules with usual lateralization of lexical-semantic aspects of language and visuo-spatial functions. Experimental validation of the uncrossed lexical-semantic aspects of language using tachistoscope methods found support for the Alexander-Annett theory that different aspects of language can be dissociated in their lateralization. The subject had difficulty identifying a semantic associate of a picture presented to the left visual field (7 errors out of 10) relative to right visual field presentation (2 errors out of 10). Bilateral free naming errors (6 and 5 errors in the left and right visual fields, respectively) occurred consistent with the aphasic presentation, suggesting phonologic-output dysfunction from the right cerebral vascular accident. Implications of the results for aphasia classification are discussed.     

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.     

Aphasia and the CNS from Imhotep to Broca.

Reviews work related to speech disorders and the central nervous system (CNS) before P. Broca's (1861) discovery of a center for articulate language in the patient Tan. Literature before 1861 indicates that Broca was not the first to write about an association between frontal lobe damage and aphasia and that the case of Tan is a confirmation of a recurrent idea. This review shows that the study of the aphasias and the brain began at least with the ancient Egyptians. The idea of speech centers in the cortex was a recurrent topic debated by physicians and scientists before Broca presented the case of Tan. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Language, cognition, and the right hemisphere: A response to Gazzaniga.

Responds to M. S. Gazzaniga's (see record 1984-07149-001) review of right-hemisphere language in split-brain patients. The present author disagrees with (1) Gazzaniga's assumption that any capacity to extract meaning from spoken or written words is indicative of linguistic competence, and (2) Gazzaniga's claim that the right hemisphere is passive and nonresponsive. The present author provides evidence that, although the right hemisphere is nonlinguistic, it is active, highly intelligent, thinking, conscious, and fully human. (22 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The relatedness-of-meaning effect for ambiguous words in lexical-decision tasks: When does relatedness matter?

Effects of the number of meanings (NOM) and the relatedness of those meanings (ROM) were examined for Japanese Katakana words using a lexical-decision task. In Experiment 1, only a NOM advantage was observed. In Experiment 2, the same Katakana words produced a ROM advantage when Kanji words and nonwords were added. Because the Kanji nonwords consisted of unrelated characters whereas the Kanji words consisted of related characters, participants may have used the relatedness of activated meanings as a cue in making lexical decisions in this experiment, artificially creating a ROM advantage for Katakana words. Consistent with this explanation, no ROM effect for Katakana words was observed in Experiment 3 when the Kanji nonwords consisted of characters with similar (i.e., related) meanings. These results pose a further challenge to the position that the speed of semantic coding is modulated by ROM for ambiguous words. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Anosognosia for motor impairment following left brain damage.

Anosognosia for motor impairment has been linked to lesions of the right hemisphere. However, left hemisphere damaged patients have often been excluded from investigation because of their associated language deficits. In this study we assessed anosognosia for motor disorders in a group of left hemisphere damaged patients using 2 tools that assess the presence of unawareness—a structured interview that is a common method of assessment of anosognosia in clinical settings, and a new tool, the Visual-Analogue Test for Anosognosia for Motor Impairment (VATAm; Della Sala, Cocchini, Beschin, & Cameron, in press). The structured interview relies heavily on language and enquires about general motor ability whereas the VATAm is less dependent on language abilities and enquires about specific motor tasks. Results suggest that the frequency of anosognosia in left brain damaged patients may have been underestimated due to methodological reasons, and that anosognosia for motor impairment can also be associated with lesions of the left hemisphere. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The inconsistency of consistency effects in reading: The case of Japanese Kanji.

Most Japanese Kanji characters have several different pronunciations, at least one ON-reading (of Chinese origin) and a KUN-reading (of Japanese origin); the appropriate pronunciation is determined by intraword context. There are also Kanji characters that have a single ON-reading and no KUN-reading. With 2-character ON-reading Kanji words as stimuli, naming experiments were carried out to investigate print-to-sound consistency effects. The consistent Kanji words were those in which neither constituent character had an alternative ON-reading or a KUN-reading, hence there can be no pronunciation ambiguity for these words. The inconsistent items were ON-reading words composed of characters that have KUN-readings that are appropriate to other words in which the characters occur, hence there should be some ambiguity about the pronunciation of the constituent characters. Six experiments yielded reliable effects of both word and character frequency and familiarity on speed and accuracy of word naming but virtually no evidence for consistency effects. It was concluded that for Kanji, phonology is dominantly computed at the word rather than at the character level. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Hand, space and attentional asymmetries in goal-directed manual aiming

Two experiments were conducted to explore the interaction of the two cerebral hemispheres in motor control, by examining hand, space and attentional asymmetries in goal-directed aiming. In Experiment 1, right-handed subjects moved to targets more quickly with their right hand than their left hand. In addition, each hand was faster when moving in its own hemispace. Although in a control condition, movements were initiated more quickly with the left hand, visual distractors disrupted left hand performance more than right hand performance. For contralateral aiming, ipsilateral distractors caused the greatest interference. In Experiment 2, when targets and distractors were all presented at the midline, a right hand advantage was found for movement time along with a left hand advantage for reaction time, independent of target and distractor location. Our findings are discussed in terms of a right hemisphere role in movement preparation and the allocation of attention in space, and greater left hemisphere involvement in movement execution.