Cortical stimulation mapping and Wada results demonstrate a normal variant of right hemisphere language organization.

Purpose: Exclusive right hemisphere language lateralization is rarely observed in the Wada angiography results of epilepsy surgery patients. Cortical stimulation mapping (CSM) is infrequently performed in such patients, as most undergo nondominant left hemisphere resections, which are presumed not to pose any risk to language. Early language reorganization is typically assumed in such individuals, taking left hemisphere epileptiform activity as confirmation of change resulting from a pathologic process.

Cortical language localization in left, dominant hemisphere. An electrical stimulation mapping investigation in 117 patients. 1989.

The localization of cortical sites essential for language was assessed by stimulation mapping in the left, dominant hemispheres of 117 patients. Sites were related to language when stimulation at a current below the threshold for afterdischarge evoked repeated statistically significant errors in object naming. The language center was highly localized in many patients to form several mosaics of 1 to 2 sq cm, usually one in the frontal and one or more in the temporoparietal lobe.

Individual variation in human motor-sensory (rolandic) cortex.

Eloquent cortex is generally identified using a variety of techniques including direct electrical stimulation to identify motor-sensory, language, and memory cortex and somatosensory evoked potentials to identify motor-sensory cortex. It is important that these areas of cortex be identified so as to prevent damage during the course of neurosurgical procedures. Seventy epilepsy patients undergoing evaluation for epilepsy surgery with chronically implanted subdural grids were retrospectively studied using both somatosensory evoked potentials and direct electrical stimulation.

Localization of language function in children: results of electrical stimulation mapping.

Object: The authors examined the localization of language sites and the frequency of naming errors at these sites in a population of children undergoing electrical stimulation mapping during surgeries in which epileptic foci and dominant hemisphere neoplasms were resected. The frequency with which essential language sites were found (that is, "the frequency of language sites") in children was compared with that of a population of adults who had undergone this procedure, to assess the relationship of age to the distribution of essential areas for language.

Methods: The results of electrical stimulation mapping to determine sites of naming and speech arrest in 26 children ranging in ages from 4 to 16 years are presented in this report.

Cortical stimulation mapping of language cortex by using a verb generation task: effects of learning and comparison to mapping based on object naming.

Object: Cortical stimulation mapping has traditionally relied on disruption of object naming to define essential language areas. In this study, the authors reviewed the use of a different language task, verb generation, in mapping language. This task has greater use in brain imaging studies and may be used to test aspects of language different from those of object naming.

Changes in power and coherence of brain activity in human sensorimotor cortex during performance of visuomotor tasks.

Electrocorticograms (ECoG) were recorded using subdural grid electrodes in forearm sensorimotor cortex of six human subjects. The subjects performed three visuomotor tasks, tracking a moving visual target with a joystick-controlled cursor; threading pieces of tubing; and pinching the fingers sequentially against the thumb. Control conditions were resting and active wrist extension.

Asymmetry of neuronal activity during extracellular microelectrode recording from left and right human temporal lobe neocortex during rhyming and line-matching.

Recordings of neuronal activity in humans have identified few correlates of the known hemispheric asymmetries of functional lateralization. Here, we examine single-unit activity recorded from both hemispheres during two delayed match-to-sample tasks that show strong hemispheric lateralization based on lesion effects; a line-matching (LM) task related to the right hemisphere, and a rhyming (RHY) task related to the left. Nineteen neuronal populations were recorded with extracellular microelectrodes from the left temporal neocortex of 11 awake patients, and 18 from the right in 9 patients during anterior temporal lobectomy for complex partial seizures under local anesthesia.

Increased gamma-range activity in human sensorimotor cortex during performance of visuomotor tasks.

Objective: We documented changes in spectral power of human electrocorticograms (ECoG) during performance of sensorimotor tasks.

Methods: In 6 human subjects, ECoGs were recorded simultaneously from 14 subdural cortical sites in forearm sensorimotor cortex. The subjects performed 3 visuomotor tasks: tracking a moving visual target with a joystick-controlled cursor, threading pieces of tubing, and pinching the fingers sequentially against the thumb.

Cerebral lateralization of neuronal activity during naming, reading and line-matching.

Changes in human right or left temporal cortical neuronal activity during language and visuospatial tasks were investigated during craniotomy under local anesthesia for medically intractable epilepsy in patients known to be left dominant for language based on preoperative intracarotid amobarbital perfusion testing. Extracellular recordings were obtained from 57 neuronal populations (26 from the left hemisphere) in the superior and middle temporal gyri of 34 patients. Frequency of activity was compared during over and silent object naming, word reading and line-matching.

Functional cortex and subcortical white matter located within gliomas.

Some neurosurgeons state that intra-axial tumors may be resected with a low risk of neurological deficit if the tumor removal stays within the confines of the grossly abnormal tissue. This is thought to be so even when the lesion is presumably located in a functional area, providing that the adjacent normal-appearing cortex and subcortical white matter are not disturbed. This retrospective analysis presents evidence that this view is not always correct, because functioning motor, sensory, or language tissue can be located within a grossly obvious tumor or the surrounding infiltrated brain.

Neuronal activity in human right lateral temporal cortex related to visuospatial memory and perception.

Neuronal activity was recorded extracellularly from 22 neurons in the right lateral temporal cortex of 12 patients undergoing awake craniotomy for surgical treatment of epilepsy during tests of visuospatial function. These included: measures of short-term visuospatial memory; face, complex figure and line matching; labeling of facial emotional expressions; and a language task, object naming. Six neurons demonstrated significant changes during one or more of the three 1.

Cortical localization of temporal lobe language sites in patients with gliomas.

In a series of 40 patients undergoing an awake craniotomy for the removal of a glioma of the dominant hemisphere temporal lobe, cortical stimulation mapping was used to localize essential language sites. These sites were localized to distinct temporal lobe sectors and compared with 83 patients without tumors who had undergone language mapping for the treatment of intractable epilepsy. In patients with and without temporal lobe gliomas, the superior temporal gyrus contained significantly more language sites than the middle temporal gyrus.

Neuronal activity in human lateral temporal cortex during serial retrieval from short-term memory.

Neuronal activity was recorded extracellularly from 20 populations in the lateral cortex of the left anterior temporal lobe of 11 patients undergoing awake craniotomy for epilepsy, during an input-distraction-retrieval measure of recent verbal memory that also included two later successive retrievals of the same information after additional distracting tasks. Changes in activity were determined for each 1 sec epoch in three major comparisons: (1) the same visual cues used for naming an input to recent memory, naming without a memory component, and a spatial matching task; (2) memory input (MI), distraction (S), and initial cued retrieval (R1) from memory, where object naming was the input to memory and naming of other objects the distractors; (3) initial retrieval (R1) and the two subsequent serial retrievals of the same information (R2, R3). Control comparisons were also made with serial naming and viewing of blank slides, and repeated naming of the same objects.

Comparing the extent of hippocampal removal to the outcome in terms of seizure control.

The relationship between the outcome of temporal lobectomy for epilepsy and the size of the hippocampectomy tailored to intraoperative electrocorticographic findings was evaluated in 52 patients, with at least 1 year of follow-up. In 22 patients, < 2.0 cm of hippocampus was removed.

Dissociation of cortical and single unit activity in spoken and signed languages.

Based on stroke and other lesion data, the cortical organization of sign language has been shown to be in the verbal language-dominant hemisphere. However, finer detail of the cortical organization of sign language is not readily available. Intraoperative cortical mapping of spoken and American Sign Language (ASL) was performed in a hearing patient proficient in ASL undergoing an awake operation for intractable epilepsy.

Use of propofol (Diprivan) for awake craniotomies: technical note.

We describe the use of propofol (Diprivan) to provide patient comfort during the initial stages of awake craniotomies.

Neuronal activity related to faces and matching in human right nondominant temporal cortex.

Neuronal activity was recorded from 13 sites in right nondominant superior and middle temporal gyrus during matching of faces (FM), matching of complex figures (CM), labelling of facial emotional expression (FE) and object naming (N) in 11 patients undergoing craniotomy under local anaesthesia. These extracellular recordings were divided into 21 neuronal populations of one to a few cells, using amplitude window discriminators. Sixty-two percent of those populations showed statistically significant changes in activity during FM; 52% during FE; 38% during N and 38% during CM.

Postoperative deficits and functional recovery following removal of tumors involving the dominant hemisphere supplementary motor area.

The supplementary motor area (SMA) is a region located within each cerebral hemisphere at the posterior mesial border of the frontal lobe adjacent to the falx. The functional significance of this area has been somewhat unclear, and information regarding its influence on motor output has largely been based on evoked responses to direct stimulation in primates and humans. In this series of patients with primary and metastatic tumors involving the dominant hemisphere SMA, a distinct pattern of postoperative deficits and recovery has emerged which emphasizes the role of this critical area in the initiation of motor activity, including speech.

Seizures of fronto-orbital origin: a proven case.

Distinguishing characteristics of seizures of frontal origin have not been clearly delineated. We describe a case of seizures of proven fronto-orbital origin to provide further definition of characteristics of seizures arising in that lobe. A 36-year-old man had medically intractable seizures since age 8 years.

Nitrous oxide: suppression of focal epileptiform activity during inhalation, and spreading of seizure activity following withdrawal.

Intraoperative brain surface electrocorticography (ECoG) is an integral part of the surgical excision of epileptogenic foci. If surgical excision is performed under general anesthesia, anesthetics should be selected that do not seriously interfere with the ECoG. We report a case where nitrous oxide appeared to suppress focal epileptiform activity at the time of intraoperative ECoG, and subsequent withdrawal of nitrous oxide produced generalized electrical seizure activity.

Neurophysiological monitoring during astrocytoma surgery.

The technique of direct stimulation mapping of the cortex is used to identify regions of language representation in the dominant cerebral hemosphere and the Rolandic cortex in either hemisphere. The use of electrocorticography to remove epileptogenic zones in patients with difficult-to-control seizures is described. The article presents the authors' experience with brain mapping during glioma surgery to maximize the extent of tumor resection and minimize surgical morbidity.

Brain mapping techniques to maximize resection, safety, and seizure control in children with brain tumors.

Intraoperative brain mapping techniques were used to localize language cortex, sensorimotor pathways, and seizure foci in children with supratentorial brain tumors. The methods of direct cortical and subcortical stimulation, in addition to electrocorticography, enabled us to maximize tumor resection, minimize morbidity, and eradicate epileptogenic zones which were always adjacent to, but not involving, the tumor nidus. Language localization was found to be quite variable in the children tested and anatomically unpredictable based on the preoperative neurological or radiological examination.

Electrocorticographic (ECoG) correlates of language. I. Desynchronization in temporal language cortex during object naming.

The electrocorticogram (ECoG) was recorded during a language task, silent naming, from sites identified as essential for naming by electrical stimulation mapping and from surrounding cortex of left dominant temporal cortex at craniotomies under local anesthesia. The ECoG was analyzed quantitatively for a reduction in spectral density in 7-12 Hz frequencies indicating 'desynchronization.' These measurements were made on the averaged ECoG in 3 subjects and on individual ECoG segments in 4.

Cortical language localization in left, dominant hemisphere. An electrical stimulation mapping investigation in 117 patients.

The localization of cortical sites essential for language was assessed by stimulation mapping in the left, dominant hemispheres of 117 patients. Sites were related to language when stimulation at a current below the threshold for afterdischarge evoked repeated statistically significant errors in object naming. The language center was highly localized in many patients to form several mosaics of 1 to 2 sq cm, usually one in the frontal and one or more in the temporoparietal lobe.

Neuronal activity in the human lateral temporal lobe. II. Responses to the subjects own voice.

We have recorded neuronal responses in the lateral temporal lobe of man to overt speech during open brain surgery for epilepsy. Tests included overt naming of objects and reading words or short sentences shown on a projector screen, repetition of tape recorded words or sentences presented over a loudspeaker, and free conversation. Neuronal activity in the dominant and non-dominant temporal lobe were about equally affected by overt speech.