Masao Matsuhashi

Low-frequency electric cortical stimulation has an inhibitory effect on epileptic focus in mesial temporal lobe epilepsy

Summary:  Purpose: This study was conducted to investigate the effect of low‐frequency electric cortical stimulation on epileptic focus in humans.

The timing of the conscious intention to move

The foundation of modern neuroscience and psychology about intention for action was laid by B. Libet et al. [(1983) Brain106, 623–642]. They reported the time of awareness of wanting to move to be about 0.2 s before voluntary movement onset. However, despite repeated confirmation of the result, their method has been criticised for its dependence on self‐reported timing and subjective memory, and the interpretation has been widely debated without general consensus. Here, we show that the mean time of the conscious intention to move was 1.42 s before movement, estimated based on the subject’s real‐time decision of whether or not there was a thought to move when a tone occurred. This event is after the onset of the bereitschaftspotential, an electroencephalographic activity preceding voluntary movement, but about 1 s earlier than the timing of intention reported previously based on the subject’s recall. Our result solves some problems of the conventional method, thus giving a clearer answer to the controversies. The difference between the conventional result and our result suggests that the perception of intention rises through multiple levels of awareness, starting just after the brain initiates movement.

Intracarotid propofol test for speech and memory dominance in man

Objective: To evaluate the usefulness of propofol as an alternative drug to amobarbital for the Wada test. Methods: The authors analyzed 67 right-handed patients out of 123 patients who were candidates for neurosurgical therapy and thus underwent the Wada test as a preoperative evaluation. Twelve were tested with propofol and 55 were tested with amobarbital. Test conditions of the Wada test, recovery time of muscle power to manual muscle testing (MMT) Grade 3 (T3/5) and Grade 5 (T5/5), onset time of the first verbal response (Tverb) after injection and that of the first nonverbal response (Tnon-verb), were compared between the two groups. Power spectrum analysis of EEG background activity during the Wada test was performed and the time and spatial distribution of polymorphic slow activities were also compared in three cases. Results: With propofol injection, lateralities of language and memory function were identified in 12 and 9 of 12 patients in comparison to amobarbital (52 and 41 of 55 patients detection in language and memory function). No complications with direct intracarotid injection of propofol were observed. T3/5 and T5/5 with propofol injection were shorter while Tverb and Tnon-verb were longer compared to amobarbital. Absolute power of polymorphic slow EEG waves gradually increased and then rapidly decreased with propofol, which was in contrast to amobarbital injection. Conclusions: With direct intracarotid propofol injection, the Wada test was satisfactorily performed in all 12 patients and 2 more patients with left-handedness or with different injection dose for each side without any complications. Clinical usefulness of propofol as an alternative drug to amobarbital for the Wada test was indicated.

Electric Stimulation on Human Cortex Suppresses Fast Cortical Activity and Epileptic Spikes

Summary:  Purpose: To investigate underlying mechanisms and adequate parameters for electric cortical stimulation to inhibit epileptic focus in humans.

Maturational change of parallel auditory processing in school-aged children revealed by simultaneous recording of magnetic and electric cortical responses.

OBJECTIVES To elucidate the maturational change of cortical auditory processing, we analyzed simultaneously recorded auditory evoked potentials (AEPs) and magnetic fields (AEFs) in school-aged children. METHODS Simultaneous recording of AEP and AEF were performed in 32 healthy children of age ranging from 6 to 14 years and 10 adults. Tone bursts of 1 kHz were presented to the left and right ears alternately with 3 different within-ear stimulus onset asynchronies (SOAs) (1.6, 3.0 and 5.0 s for each ear) under attention-distracted condition. RESULTS All subjects showed clear N100 and N100m peaks under the longest SOA condition (5.0 s). Under the shortest SOA condition (1.6 s), 4 out of 19 subjects under 12 years (21%) failed to show the N100m component. By contrast, N250 and N250m were observed in the majority of children (29/32: 91%) while those were detected in only 4 out of 10 adults (40%). The spatial distribution of N100 in children under 9 years differed from that in older subjects, whereas the dipole orientation of N100m was constant among age groups, suggesting that radially oriented sources might make additional contribution to the generation of N100 in early childhood. N250 was significantly larger in children than in adults. The strength of N250 was suppressed with longer SOAs, whereas that of N100 was enhanced. The dipole of N250m was located around Heschls gyrus on the superior temporal plane which was significantly medial, anterior and inferior to that of N100m. CONCLUSIONS Dissociation of maturational change between the tangential and radial components of N100 suggests that auditory processing at around 100 ms consists of multiple parallel pathways which mature independently. Furthermore, a negative peak at around 250 ms specifically seen in children has different generators from N100 and might represent a special auditory processing which takes an active part until acquisition of the efficient cortical networks of the adult brain.

Multisensory convergence at human temporo-parietal junction – epicortical recording of evoked responses

OBJECTIVE Previous lesion studies in patients and functional imaging studies in normal subjects have led to the notion that the temporo-parietal junction (TPJ) has an integrative function for multisensory inputs. However, its electrophysiological properties such as response latencies and distributions of responses to various stimulus modalities in humans have not been fully investigated. The aim of the study is to clarify this issue. METHODS We recorded evoked potentials to different kinds of sensory stimuli including somatosensory, auditory and visual modalities in 6 patients with intractable partial epilepsy, who underwent chronic implantation of subdural electrodes in TPJ for presurgical evaluation. RESULTS In 5 out of 6 subjects, at least one electrode located in TPJ for each subject showed a maximum somatosensory evoked response commonly to electric, passive joint motion and pain stimuli. These electrodes showed the maximum responses also to tone stimuli in all of 4 subjects studied, and to visual motion stimuli in 3 out of 5 subjects studied. The polarity was consistent regardless of the stimulus modality within each individual subject, although the anatomical location, polarity and latency varied among subjects. CONCLUSIONS A small area in TPJ for each individual subject receives sensory information of multiple modalities possibly coming from different receptive sites, although the electrophysiological properties of the responses may vary among subjects. SIGNIFICANCE We confirmed the convergence of somatosensory, auditory and visual evoked responses at human TPJ.

Partial Epilepsy Manifesting Atonic Seizure: Report of Two Cases

Summary:  Purpose: Atonic seizures are commonly seen in patients with generalized epilepsy but only infrequently in patients with partial epilepsy. Clinically generalized atonic seizures as a partial epilepsy have not been studied in detail with video/EEG monitoring. Here we describe the clinical and physiologic characteristics of atonic seizures due to partial epilepsy and discuss the underlying mechanism.

Left anterior temporal cortex actively engages in speech perception: A direct cortical stimulation study

Recent neuroimaging studies proposed the importance of the anterior auditory pathway for speech comprehension. Its clinical significance is implicated by semantic dementia or pure word deafness. Neurodegenerative or cerebrovascular nature, however, precluded precise localization of the cortex responsible for speech perception. Electrical cortical stimulation could delineate such localization by producing transient, functional impairment. We investigated engagement of the left anterior temporal cortex in speech perception by means of direct electrical cortical stimulation. Subjects were two partial epilepsy patients, who underwent direct cortical stimulation as a part of invasive presurgical evaluations. Stimulus sites were coregistered to presurgical 3D-MRI, and then to MNI standard space for anatomical localization. Separate from the posterior temporal language area, electrical cortical stimulation revealed a well-restricted language area in the anterior part of the superior temporal sulcus and gyrus (aSTS/STG) in both patients. Auditory sentence comprehension was impaired upon electrical stimulation of aSTS/STG. In one patient, additional investigation revealed that the functional impairment was restricted to auditory sentence comprehension with preserved visual sentence comprehension and perception of music and environmental sounds. Both patients reported that they could hear the voice but not understand the sentence well (e.g., heard as a series of meaningless utterance). The standard coordinates of this restricted area at left aSTS/STG well corresponded with the coordinates of speech perception reported in neuroimaging activation studies in healthy subjects. The present combined anatomo-functional case study, for the first time, demonstrated that aSTS/STG in the language dominant hemisphere actively engages in speech perception.

A mirror reflection of a hand modulates stimulus-induced 20-Hz activity

Mirror therapy is one of the promising rehabilitation therapeutic interventions but the neural basis of the therapeutic effect remains unknown. It has been reported that the 20-Hz rhythmic activity is induced in the primary motor cortex after median nerve stimulation and the amount of the induced activity is decreased when the primary motor cortex is activated. In the present study, to elucidate the neural mechanisms underlying mirror therapy, we investigated whether the mirror reflection of a hand holding a pencil modulates the stimulus-induced 20-Hz activity. Neuromagnetic brain activities were recorded from 11 healthy right-handed subjects while they were viewing their hand holding a pencil or its mirror reflection. The right median nerve was stimulated and the stimulus-induced 20-Hz activity over the left rolandic cortex dominantly innervating right-hand movements was quantified. The stimulus-induced 20-Hz activity was strongly suppressed when subjects viewed the right hand holding a pencil or the mirror reflection of the left hand looking like the right hand holding a pencil, compared with when subjects viewed the left hand holding a pencil or the mirror reflection of the right hand looking like the left hand holding a pencil. These results suggest that the human left primary motor cortex is strongly activated when the subjects view not only the right hand holding a pencil but also the mirror reflection of the left hand looking like the right hand holding a pencil. This may be one of the neural mechanisms responsible for the therapeutic effect of mirror therapy.

Mirth and laughter arising from human temporal cortex

Laughter and mirth are essential in our enjoyment of daily life and in facilitating communication. Various studies have been done relating to the emotional processing that takes place in the human cerebral cortex, but few have explored the cerebral origins of mirth. Some reports on pathological laughter have implicated the hypothalamus, brain stem, and temporal lobe.1–3 As part of the presurgical evaluation of patients with epilepsy, electric cortical stimulation is used to delineate the functional cortical areas, and sometimes this elicits various emotional responses.4 However, only two stimulation studies2,5 have been conducted with a focus on mirth and laughter. Arroyo et al suggested that the motor act of laughter and the processing of its emotional content were separately represented in, respectively, the anterior cingulate area and the basal temporal area (the fusiform gyrus or parahippocampal gyrus, or both).2 Fried et al suggested not only that laughter and mirth were represented in the presupplementary motor area, but also that there was close linkage between the motor, affective, and cognitive components of laughter.5 We report a patient in whom electric cortical stimulation applied to the inferior temporal gyrus produced mirth alone or laughter preceded by mirth, depending on the intensity of the stimulation. A 24 year old right handed …