RESUMEN
We explored the efficacy and safety of bilateral SubThalamic Nucleus (STN) stimulation in two subjects suffering from drug-resistant epilepsy even after anterior callosotomy. Case 1 had about 65% decrease of partial motor seizures and the complete disappearance of tonic-clonic generalized attacks. Case 2, with sudden drop (atonic) attacks, partial complex seizures, atypical absences and rare tonic-clonic seizures, showed no meaningful reduction of fits and a stimulation associated atypical absence rate increase.
Asunto(s)
Cuerpo Calloso/cirugía , Estimulación Encefálica Profunda/métodos , Epilepsia/terapia , Psicocirugía/métodos , Núcleo Subtalámico/fisiología , Adulto , Femenino , Humanos , Estudios Longitudinales , Masculino , Resultado del TratamientoRESUMEN
This study investigated interhemispheric transfer in ten normal, four anterior-, and four totally-split-brain individuals, through measures of manual asynchrony and bimanually-recorded crossed-uncrossed difference (CUD). The CUD relied on the difference between crossed and uncrossed responses whereas the asynchrony measure relied on the reaction time difference between the two responding hands. Manipulations of sensory and attentional factors were assessed for both measures. We found a normal CUD (3.8 ms) along with an exacerbated and more variable asynchrony for partial split-brain individuals (40.8 ms) compared to normal individuals (CUD: 0.4 ms, asynchrony: 13.8 ms). In turn, the CUD of total split-brain individuals (20.4 ms) was larger than that of partial split-brain and normal individuals. Also, the asynchrony of total split-brain individuals (57.6 ms) was larger and more variable than that of normal individuals, and more variable than that of partial split-brain individuals. We interpret these results as behavioural evidence of independent mechanisms underlying the CUD and bimanual synchronization, as well as evidence of the joint involvement of both the anterior and the posterior portions of the corpus callosum in bimanual coordination.
Asunto(s)
Cuerpo Calloso/fisiología , Lateralidad Funcional/fisiología , Desempeño Psicomotor/fisiología , Procedimiento de Escisión Encefálica , Adulto , Análisis de Varianza , Atención/fisiología , Cuerpo Calloso/cirugía , Humanos , Estimulación Luminosa , Tiempo de Reacción/fisiologíaRESUMEN
Recent neuroimaging studies suggest lateralized cerebral mechanisms in the right temporal parietal junction are involved in complex social and moral reasoning, such as ascribing beliefs to others. Based on this evidence, we tested 3 anterior-resected and 3 complete callosotomy patients along with 22 normal subjects on a reasoning task that required verbal moral judgments. All 6 patients based their judgments primarily on the outcome of the actions, disregarding the beliefs of the agents. The similarity in performance between complete and partial callosotomy patients suggests that normal judgments of morality require full interhemispheric integration of information critically supported by the right temporal parietal junction and right frontal processes.
Asunto(s)
Juicio/fisiología , Principios Morales , Trastorno de la Conducta Social/etiología , Percepción Social , Procedimiento de Escisión Encefálica/efectos adversos , Adolescente , Adulto , Epilepsia/cirugía , Femenino , Humanos , Imagen por Resonancia Magnética/métodos , Masculino , Pruebas Neuropsicológicas , Trastorno de la Conducta Social/psicología , Adulto JovenRESUMEN
Two callosotomized patients and 24 neurologically normal subjects performed simple binary discriminations between upright letters flashed in one or other visual field. Where discrimination of the letters F and R by name either showed a left-hemisphere advantage or no hemispheric effect, discrimination of whether the same letters were normal or backward showed a right-hemisphere advantage. These results suggest that discrimination of mirror-image letters depends on matching to an exemplar, for which the right-hemisphere is dominant, while letter naming depends on abstract category recognition. One commissurotomized patient, DDV, showed systematic left-right reversal of the letters in the left visual field, classifying the normal letters as reversed and reversed ones as normal, and persisted with this reversal when the letters were shown in free vision. This suggests that reversed exemplars of the letters may be laid down the right cerebral hemisphere. There was no such reversal in the other patient (DDC).
Asunto(s)
Cuerpo Calloso/fisiopatología , Aprendizaje Discriminativo/fisiología , Imaginación/fisiología , Reconocimiento Visual de Modelos/fisiología , Campos Visuales/fisiología , Adulto , Cuerpo Calloso/cirugía , Toma de Decisiones/fisiología , Epilepsia/fisiopatología , Epilepsia/cirugía , Femenino , Humanos , Masculino , Persona de Mediana Edad , Pruebas Neuropsicológicas , Estimulación Luminosa/métodos , Adulto JovenRESUMEN
This study investigated the redundant target effect (RTE) in partial split-brain (anterior section sparing the splenium), total split-brain, and neurologically intact individuals. All completed an RTE protocol in which targets were presented on the midline or in an inter- or intrahemispheric manner. Stimuli of different nature (luminance, equiluminant colour, and global motion) were used separately in three experiments in order to investigate the contribution of subcortical versus cortical pathways. Despite the preservation of the splenium (the portion of the corpus callosum assumed to transfer visual information), partial split-brain individuals showed an enhanced RTE pattern as compared to neurologically intact individuals. Total split-brain individuals showed a tendency toward larger RTEs with the luminance stimuli than with the colour and motion stimuli, whereas this was not the case for partial split-brain individuals, suggesting a contribution of the posterior portion of the corpus callosum in the RTE. It is therefore likely that both sensory and motor processes contribute to the enhanced RTE in split-brain individuals.
Asunto(s)
Encéfalo/fisiopatología , Corteza Cerebral/fisiopatología , Cuerpo Calloso/fisiopatología , Desempeño Psicomotor , Procedimiento de Escisión Encefálica/psicología , Percepción Visual , Adulto , Cuerpo Calloso/patología , Cuerpo Calloso/cirugía , Femenino , Lateralidad Funcional , Humanos , Masculino , Estimulación Luminosa/métodos , Tiempo de Reacción , Vías VisualesRESUMEN
The aim of this study was to investigate the relationships between oxcarbazepine (OXC) dosage, metabolite mono-hydroxy-derivative (MHD) serum concentrations, number of concomitant antiepileptic drugs, age and incidence of adverse events (AEs) in epileptic patients. A retrospective analysis was conducted of 414 consecutive epileptic patients on OXC alone or added-on to previous therapy. The sample was collected from the period 2001 to 2006. Statistical analysis was performed in two groups: with and without AEs. Eighty-seven patients (21%) experienced at least one AE. The most frequent was hyponatremia, reported in 9.2%. OXC was discontinued because of AEs in 27 cases. There were no important differences between patients with and without AEs, except for age (p=0.04). The categorization of patients into three different age ranges, <20, 20-59 and (3)60 years, disclosed that the risk of AEs is notably lower in young (<20 years) and adult (20-59 years) patients (OR 0.46 and 0.51, respectively). In particular, the patients who experienced hyponatremia were significantly older than those who did not (p=0.0045). The other variables showed no major changes according to age. The incidence of major AEs during OXC treatment, leading to withdrawal, was found to be low and influenced by age, but not by OXC dosage, MHD concentrations or number of concomitant antiepileptic drugs.
Asunto(s)
Anticonvulsivantes/efectos adversos , Carbamazepina/análogos & derivados , Epilepsia/tratamiento farmacológico , Hiponatremia/inducido químicamente , Adolescente , Adulto , Distribución por Edad , Anciano , Anciano de 80 o más Años , Anticonvulsivantes/sangre , Carbamazepina/efectos adversos , Carbamazepina/sangre , Niño , Relación Dosis-Respuesta a Droga , Interacciones Farmacológicas , Quimioterapia Combinada , Epilepsia/sangre , Femenino , Humanos , Masculino , Persona de Mediana Edad , Oportunidad Relativa , Oxcarbazepina , Estudios RetrospectivosRESUMEN
It is now common knowledge that the total surgical section of the corpus callosum (CC) and of the other forebrain commissures prevents interhemispheric transfer (IT) of a host of mental functions. By contrast, IT of simple sensorimotor functions, although severely delayed, is not abolished, and an important question concerns the pathways subserving this residual IT. To answer this question we assessed visuomotor IT in split-brain patients using the Poffenberger paradigm (PP), that is, a behavioral paradigm in which simple reaction time (RT) to visual stimuli presented to the hemifield ipsilateral to the responding hand is compared to stimuli presented to the contralateral hemifield, a condition requiring an IT. We tested the possibility that the residual IT is mediated by the collicular commissure interconnecting the two sides of the superior colliculus (SC). To this purpose, we used short-wavelength visual stimuli, which in neurophysiological studies in non-human primates have been shown to be undetectable by collicular neurons. We found that, in both totally and partially callosotomised patients, IT was considerably longer with S-cone input than with L-cone input or with achromatic stimuli. This was not the case in healthy participants in whom IT was not affected by color. These data clearly show that the SC plays an important role in IT of sensorimotor information in the absence of the corpus callosum.
Asunto(s)
Cuerpo Calloso/fisiología , Lateralidad Funcional/fisiología , Tiempo de Reacción/fisiología , Colículos Superiores/fisiología , Vías Visuales/fisiología , Percepción Visual/fisiología , Adulto , Estudios de Casos y Controles , Cuerpo Calloso/cirugía , Femenino , Humanos , Masculino , Análisis por Apareamiento , Persona de Mediana Edad , Movimiento/fisiología , Pruebas Neuropsicológicas , Desempeño Psicomotor/fisiología , Valores de ReferenciaRESUMEN
The question of whether there is a right-hemisphere dominance in the processing of auditory spatial information in human cortex as well as the role of the corpus callosum in spatial hearing functions is still a matter of debate. Here, we approached this issue by investigating two late-callosotomized subjects and one subject with agenesis of the corpus callosum, using a task of sound lateralization with variable interaural time differences. For comparison, three subjects with left or right hemispherectomy were also tested by employing identical methods. Besides a significant reduction in their acuity, subjects with total or partial section of the corpus callosum exhibited a considerable leftward bias of sound lateralization compared to normal controls. No such bias was found in the subject with callosal agenesis, but merely a marginal reduction of general acuity. Also, one subject with complete resection of the left cerebral cortex showed virtually normal performance, whereas another subject with left hemispherectomy and one subject with right hemispherectomy exhibited severe deficits, with almost total loss of sound-lateralization ability. The results obtained in subjects with callosotomy indicate that the integrity of the corpus callosum is not indispensable for preservation of sound-lateralization ability. On the other hand, transcallosal interhemispheric transfer of auditory information obviously plays a significant role in spatial hearing functions that depend on binaural cues. Moreover, these data are compatible with the general view of a dominance of the right cortical hemisphere in auditory space perception.
Asunto(s)
Cuerpo Calloso , Dominancia Cerebral/fisiología , Hemisferectomía , Localización de Sonidos/fisiología , Estimulación Acústica/métodos , Adulto , Agenesia del Cuerpo Calloso , Cuerpo Calloso/patología , Cuerpo Calloso/fisiología , Cuerpo Calloso/cirugía , Femenino , Humanos , Masculino , Persona de Mediana Edad , Tiempo de Reacción/fisiologíaRESUMEN
We describe the case of a callosotomized man, D.D.V., who shows unusual neglect of stimuli in the left visual field (LVF). This is manifest in simple reaction time (RT) to stimuli flashed in the LVF and in judging whether pairs of filled circles in the LVF are of the same or different color. It may reflect strong left-hemispheric control and consequent attention restricted to the right side of space. It is not evident in simple RT when there are continuous markers in the visual fields to indicate the locations of the stimuli. In this condition, his RTs are actually faster to LVF than to right visual field (RVF) stimuli, suggesting a switch to right-hemispheric control that eliminates the hemineglect. Neglect is also not evident when D.D.V. responds by pointing to or touching the locations of the stimuli, perhaps because these responses are controlled by the dorsal rather than the ventral visual system. Despite his atypical manifestations of hemineglect, D.D.V. showed evidence of functional disconnection typical of split-brained subjects, including prolonged crossed-uncrossed different in simple reaction time, inability to match colors between visual fields, and enhanced redundancy gain in simple RT to bilateral stimuli even when the stimulus in the LVF was neglected.
Asunto(s)
Cuerpo Calloso/fisiopatología , Trastornos de la Percepción/fisiopatología , Campos Visuales/fisiología , Atención/fisiología , Cuerpo Calloso/cirugía , Lateralidad Funcional/fisiología , Humanos , Masculino , Persona de Mediana Edad , Trastornos de la Percepción/cirugía , Estimulación Luminosa/métodos , Desempeño Psicomotor/fisiología , Tiempo de Reacción/fisiología , Estudios RetrospectivosRESUMEN
Three total and three partial callosotomy patients underwent neuropsychological testing to evaluate interhemispheric transfer of tactile information. Tactile transfer is required to name objects presented to the left hand, to compare objects held in either hand, and to transfer topological information between hands. Tactile Naming, Same-Different Recognition, and Tactile Finger Localization Tests (intra- and intermanual tasks) were administered as specific tools. Results were compared with previous fMRI data from the same subjects and with the performance of a control group (20 age-matched subjects). Total callosotomy patients performed modestly: mean correct responses were 93% and 30% (right and left hand, respectively) in Tactile Naming; 68% in Same-Different Recognition; 84% and 76% (right and left hand stimulation, respectively) in intermanual Tactile Finger Localization, and 100% in the intramanual task. Partial callosotomy patients achieved 93-100% accuracy: all have an intact splenium, and one, and possibly all, also an intact posterior callosal body. Controls scored 99% in Tactile Naming, both hands, and Same-Different Recognition; 100% in intramanual Tactile Finger Localization; and 96% and 95%, with right and left hand stimulation, respectively, in the intermanual task. Differences between the two callosotomy groups were significant, as were those between total callosotomy patients and controls. The partial callosotomy group scored like the control subjects. Neuropsychological data agree with previous functional findings, further demonstrating that interhemispheric tactile transfer requires posterior corpus callosum integrity.
Asunto(s)
Cuerpo Calloso/fisiopatología , Lateralidad Funcional/fisiología , Reconocimiento en Psicología/fisiología , Tacto/fisiología , Transferencia de Experiencia en Psicología/fisiología , Adulto , Mapeo Encefálico , Estudios de Casos y Controles , Cuerpo Calloso/cirugía , Epilepsia/fisiopatología , Epilepsia/cirugía , Femenino , Humanos , Imagen por Resonancia Magnética , Masculino , Pruebas Neuropsicológicas , Oxígeno/sangre , Estimulación Física/métodos , Desempeño Psicomotor/fisiología , Corteza Somatosensorial/irrigación sanguínea , Corteza Somatosensorial/fisiopatologíaRESUMEN
Five people lacking the corpus callosum (two callosotomized, three with agenesis of the corpus callosum) and neurologically normal subjects were shown vertical lines that appeared instantaneously between pairs of rectangles in one or other visual field. When one of the rectangles flashed prior to the presentation of the line, and the line was in the same visual field, all subjects perceived the line as spreading from the flashed rectangle to the other. Normal subjects and one of the callosotomized subjects showed a slight but significant right visual-field advantage, perhaps reflecting a left-hemispheric superiority in processing rapid temporal events. The illusion was also induced when the line and the flash were in opposite visual fields in one of the callosotomized, one of the acallosal subjects, and about half of the normal subjects, implying interhemispheric integration even in the absence of the corpus callosum.