Left Scalp Research Articles

Decoupling beliefs from reality in the brain: an ERP study of theory of mind.

Theory of mind, attributing behaviors to mental states, is a cognitive ability central to human social interactions. To investigate the neural substrates of theory of mind reasoning, we recorded human event-related brain potentials (ERP) while participants made judgments about belief and judgments about reality. A late ERP component (peaking around 800 ms post-stimulus) with a left frontal scalp distribution, which was inconsistent with a source in the anterior paracingulate cortex and consistent with a source possibly in the left orbitofrontal cortex, differentiated judgments about belief and about reality. This late left frontal component is probably associated with the decoupling mechanism that distinguishes mental states from reality.

Prefrontal-cingulate activation during executive control: which comes first?

The Stroop test requires executive control functions, in particular inhibition of a learned routine (in this case, word reading). The spatiotemporal analysis of brain activation during Stroop task execution was performed in 16 healthy subjects using high-density event-related potentials (ERPs) and dipole source modeling (BESA software). Scalp ERP analysis revealed the neurophysiological substrate of the interference effect: first, a greater negativity in the incongruent as compared to the congruent and neutral conditions was found between 350 and 450 ms poststimulus over left frontocentral scalp regions. Source analysis of the difference wave (incongruent–congruent) indicated that a generator localized in left prefrontal cortex (PFC) contributed to this effect. Second, immediately after the first effect, a greater positivity in the incongruent as compared to the congruent and neutral conditions developed between 450 and 550 ms poststimulus over midline frontocentral scalp regions. A generator of this effect was located in right anterior cingulate cortex (ACC). ACC activation seems to follow the activation of PFC with some overlap between the two components. Possible interpretation of this finding is that PFC signals ACC when executive control is required and ACC implements the control.

Design and implementation of an SVM-based computer classification system for discriminating depressive patients from healthy controls using the P600 component of ERP signals

A computer-based classification system has been designed capable of distinguishing patients with depression from normal controls by event-related potential (ERP) signals using the P600 component. Clinical material comprised 25 patients with depression and an equal number of gender and aged-matched healthy controls. All subjects were evaluated by a computerized version of the digit span Wechsler test. EEG activity was recorded and digitized from 15 scalp electrodes (leads). Seventeen features related to the shape of the waveform were generated and were employed in the design of an optimum support vector machine (SVM) classifier at each lead. The outcomes of those SVM classifiers were selected by a majority-vote engine (MVE), which assigned each subject to either the normal or depressive classes. MVE classification accuracy was 94% when using all leads and 92% or 82% when using only the right or left scalp leads, respectively. These findings support the hypothesis that depression is associated with dysfunction of right hemisphere mechanisms mediating the processing of information that assigns a specific response to a specific stimulus, as those mechanisms are reflected by the P600 component of ERPs. Our method may aid the further understanding of the neurophysiology underlying depression, due to its potentiality to integrate theories of depression and psychophysiology.

Transcranial magnetic stimulation to the parietal lobes reduces detection of contralateral somatosensory stimuli.

Neglect has been described in patients with lesions of the parietal cortex and has been interpreted as a disorder of the allocation of spatial attention. The persistence of neglect has been linked to poor rehabilitation outcome in patients suffering from acute stroke. Transcranial magnetic stimulation (TMS) applied to the parietal cortex has been shown to induce changes in the perception of stimuli including tactile stimulation of the fingers contra- and ipsilateral to the stimulated hemisphere. In the current study, eleven normal young subjects performed a detection task for cutaneous electrical stimuli to the left or right forearm that had been precued by a preceding visual warning stimulus. To investigate the role of the parietal cortical areas for attentional processes TMS was applied to frontal and parietal scalp sites of each hemisphere in the cue-target interval before the somatosensory stimulus. Right and left parietal stimulation led to reduced detection sensitivity for near threshold stimuli to the forearm contralateral to the stimulated hemisphere without hemispheric differences. Ipsilateral tactile perception was not influenced by parietal TMS and there was no change in perception after frontal stimulation to left or right scalp sites. This pattern of results is consistent with a role of the right and left parietal lobe in the distribution of spatial attention and provides an experimental basis for possible therapeutical application of TMS to improve attentional deficits in stroke patients.

Effect of stimulus frequency on human cerebral hemodynamic responses to electric median nerve stimulation: a near-infrared spectroscopic study

We examined the effect of stimulus frequency on optically recorded hemodynamic responses to electric median nerve stimulation. Electric stimuli were delivered to the right median nerve with an intensity of 90% of motor threshold. Four different stimulus frequencies (2, 5, 10, and 20 Hz) were administered in each subject. By means of a multi-channel near-infrared spectroscopic instrument, changes in concentration of oxygenated hemoglobin were continuously measured over the left scalp. After 20 Hz stimulation, we found two spatially and temporally distinct hemodynamic responses. One lasted beyond 60 s, and the center of this response was located over the secondary somatosensory area. The other had a transient duration starting immediately after the stimulus onset and was located in the primary somatosensory hand area. Both responses were linearly augmented as a function of the stimulus frequency. Since temporal activation patterns are different in two somatosensory areas, real-time optical monitoring is necessary in evaluation of hemodynamic responses to electric nerve stimulation.

Effect of stimulus frequency on human cerebral hemodynamic responses to electric median nerve stimulation: a near-infrared spectroscopic study

We examined the effect of stimulus frequency on optically recorded hemodynamic responses to electric median nerve stimulation. Electric stimuli were delivered to the right median nerve with an intensity of 90% of motor threshold. Four different stimulus frequencies (2, 5, 10, and 20 Hz) were administered in each subject. By means of a multi-channel near-infrared spectroscopic instrument, changes in concentration of oxygenated hemoglobin were continuously measured over the left scalp. After 20 Hz stimulation, we found two spatially and temporally distinct hemodynamic responses. One lasted beyond 60 s, and the center of this response was located over the secondary somatosensory area. The other had a transient duration starting immediately after the stimulus onset and was located in the primary somatosensory hand area. Both responses were linearly augmented as a function of the stimulus frequency. Since temporal activation patterns are different in two somatosensory areas, real-time optical monitoring is necessary in evaluation of hemodynamic responses to electric nerve stimulation.

Blunt multi-system trauma

Dr. Nathan Mick: Today’s case is that of a 46-year-old man who was struck by a car traveling at approximately 35 mph. According to witnesses, the patient was facing the car when he was hit and thrown 20 feet. When first responders arrived, the patient was found to have a Glascow Coma Scale (GSC) score of 6 and obvious bilateral lower extremity deformities. Pre-hospital personnel at the scene called for helicopter evacuation to a trauma center. The helicopter transport team found the patient supine on a long board with his cervical spine immobilized. The GCS was 6 with sonorous respirations. Vitals signs were as follows: heart rate (HR) 120 beats per minute, systolic blood pressure (BP) 120 mm Hg, and respiratory rate (RR) 10 breaths per minute. Two large bore antecubital intravenous (i.v.) lines were placed. He was pre-oxygenated and then intubated using rapid sequence induction with etomidate 20 mg i.v. and succinylcholine 100 mg i.v. Endotracheal tube placement was confirmed with a colorimetric end-tidal CO2 detector; the patient received midazolam 2 mg i.v. and vecuronium 8 mg i.v. En route to the hospital, the patient received 2000 cc of crystalloid i.v. and was noted to be persistently tachycardic. Dr. Eric Nadel: Are there any questions regarding the pre-hospital course? Dr. Barbara Masser: Why did the on-scene personnel elect to call the helicopter rather than transport the patient via ground ambulance? Dr. Stephen Thomas: Due to the extent of the patient’s injuries and the fact that rush hour traffic would delay transport to the nearest level I trauma center, I think that their choice was a prudent one. The question of when and how to best utilize aeromedical transport vehicles in the urban trauma setting has been long debated. It is generally accepted that the combination of timedistance factors and injury severity reliably predicts who might benefit from air transport to a Level I trauma center (1). Dr. Nathan Mick: The patient arrived in the Emergency Department (ED) at 1900 hours, approximately 45 minutes after being struck. The primary survey revealed that he was sedated, chemically paralyzed, and orally intubated; endotracheal tube placement was confirmed by auscultation of bilateral breath sounds and capnography. Femoral and carotid pulses were 2 and equal. The vital signs were BP 80/56 mm Hg, HR 115 beats/minute, mechanically ventilated RR 12 breaths/minute, oxygen saturation 100%. Secondary survey revealed a GCS of 3. There was a 2-cm laceration over the right eye with pupils that were 3 mm, symmetric and non-reactive. There was soft tissue swelling over the left parietal scalp without palpable deformity. The neck was immobilized; the trachea was midline. Examination of the chest revealed bilateral breath sounds with no crepitance or flail segments. The abdomen was non-distended without palpable masses.

Meningeal melanocytoma of the brain and oculodermal melanocytosis (nevus of ota): case report and literature review

Background Meningeal melanocytomas are rare benign pigmented tumors of meningeal melanocytes. Nevus of Ota is a melanocytic pigmentation of the sclera and the skin adjacent to the eye. We report a rare case of parietal convexity meningeal melanocytoma associated with ipsilateral mucocutaneous melanosis and review the literature. Methods A 17-year-old man presented with headache and blindness. There was left scalp and facial mucocutaneous melanosis. During surgery, speckled hyperpigmentation was seen in all layers of the scalp, bone, dura, and even ependyma. Pathologic examination of the tumor and scalp consisted of light microscopy and immunohistochemistry. In a literature review, the demographics (age, sex), clinical characteristics (site of lesion, duration of symptoms), therapeutic options (surgical excision, radiotherapy), and prognosis (recurrence, death, death related to the disease, and follow-up) were analyzed. For statistical analysis we used the independent sample t-test and χ 2 tests. Results Ninety-five cases (45 intracranial and 50 spinal) of meningeal melanocytoma have been reported. The median age of patients with intracranial lesions (40 years) was significantly lower than that of patients with spinal lesions (49 years) ( p = 0.016). Of the 95 patients, 57.9% were female. In the nervous system, melanocytes are more common in the infratentorial and cervical areas, but more than half of the tumors have been located in the supratentorial region and the thoracic spine. In 46 months median follow-up, tumor recurrence rate and tumor related death rate were 26.3% and 10.5%, respectively. These were not statistically significant for different therapeutic modalities. There was a trend toward shorter survival for patients who underwent subtotal tumor resection without radiotherapy compared with other groups. Conclusion The prognostic criteria, differential diagnosis, and the embryological aspects of meningeal melanocytoma are discussed with a review of the related literature.

Level-repetition effects in hierarchical stimulus processing: timing and location of cortical activity

The specific mechanisms that underlie repetition priming effects are only partly understood. We examined the timing and extent of brain activity in response to level-repeated and level-shifted conditions during hierarchical stimulus processing. A response cost in behavioral reaction times was evident for level-shifted compared to level-repeated conditions. Larger event-related potentials amplitudes for level-shifted conditions were evident over occipital scalp regions for an early component peaking at 132 ms post-stimulus onset. A negative potential over posterior temporal electrodes that peaked at 204 ms showed asymmetries in amplitudes that were consistent with lateralized differences in global and local level processing. A positive potential peaking at 290 ms also showed differences between level-repeated and level-shifted conditions over left parietal and left posterior temporal scalp regions. The study demonstrates cortical activity related to repetition priming for both local and global level targets. Early sensory (‘P1’) and later cortical processing can be affected by the need to shift attention across hierarchical levels. The results support the existence of multiple processes underlying level-repetition effects.

MRI Findings of the Brain in High-Voltage Electrical Burn Patient: Case Report

We report the delayed sequelae arising in a case of electrical injury, reviewing the literature on the subject and focusing on the MRI findings of the brain. A 23-year-old male suffered burns to the left parietal scalp, both feet, and the anterior chest wall. Neurological symptoms and MRI abnormalities appeared 14 days after the insult and continued for about three months. T1-weighted MR images demonstrated homogeneous hypointensity, while T2-weighted images depicted hyperintense finger-like projections. Contrast-enhanced T1-weighted images demonstrated strong band-like enhancement, indicating meningeal hyperemia. Follow-up MR imaging showed that the lesion had disappeared, indicating that the cerebral edema and meningeal hyperemia were reversible.

頭部血管肉腫 頭部血管肉腫の１剖検例

An 83-year-old man noted rapidly progressing nodes with recurrent bleeding on the scalp for 2 months. He had no history of head injury, although he had renal failure, hypertension and gallstones. The patient first visited the department of surgery in a neighboring hospital, and a biopsy of the node disclosed the findings of angiosarcoma. The patient was referred to our department for the treatment with IL-2 and electron beam. Examination on admission revealed palm-sized, welldemarcated darkly-reddish plaque on the left parietal and occipital scalp. Several thumb-head sized dome-shaped nodes were coalesced on the center of the plaque. Local injection of IL-2 was started and then electron beam therapy (totally 50 Gy) was added. Pulmonary metastases were found on 75th day of hospitalization, and the patient died of respiratory failure one month later. Post-mortem examination revealed multiple metastases of the both lungs, the liver, the diaphragm and the cervical lymph nodes. Tumor cells were also found in the pleural fluid.We clinically and pathologically compared the same site on admission and on post-mortem examination. Plaque lesions on admission underwent nodular lesions on autopsy. Histologically, the density of tumor cells was increased whereas the formation of vascular lumina was obscure in the specimens of the autopsy. The densities of p53 and MIB-1 positive cells were greater in the specimens of the autopsy than those on admission. [Skin Cancer (Japan) 2003; 18: 208-213]

P300 amplitude over temporal regions in schizophrenia

To examine the left temporal scalp area reductions of P300 amplitude, event-related potentials (ERPs) during a standard oddball task were recorded in 57 schizophrenic patients and 33 normal controls. The P300 amplitude at T3 was not significantly smaller than that at T4 in schizophrenic patients. In the ANOVA analysis of P300 peak amplitude, significant lateral topographical differences in P300 were not present between patients and controls. However, in schizophrenia, patients in the low T3 P300 group have relatively low P300 amplitudes and significantly delayed P300 latency, compared with those in the high T3 P300 group. These findings suggested that the reduction of left temporal P300 amplitude may be associated with the severity of the disease process and/or impairment of cognitive function.

EMG discharge patterns during human grip movement are task-dependent and not modulated by muscle contraction modes: a transcranial magnetic stimulation (TMS) study

Our previous study revealed that, during tonic muscle contraction, remarkable functional differences among intrinsic and extrinsic muscles were observed during two different grip movements, i.e., precision and power grips. To verify whether this evidence is true even under the phasic muscle contraction, magnetic stimulation was delivered over the left scalp while a normal human subject performed phasic precision or power grip responses of the right-hand fingers in a simple reaction time (SRT) paradigm. Magnetic stimulation delivered during the latent period revealed different cortico-motoneuronal excitations between the two grip responses. In particular, the contributions of extensor carpi radialis (ECR) muscle were definitely different between the two grip responses, although motor-evoked potentials (MEPs) of first dorsal interosseous (FDI) prior to, and after EMG onset of movement initiation, were not different. These results were similar to previous results obtained during tonic muscle contraction. Thus, we have concluded that the task-dependent EMG discharge pattern in finger manipulation could not be modulated by muscle contraction modes.

P300 amplitude over temporal regions in schizophrenia

To examine the left temporal scalp area reductions of P300 amplitude, event-related potentials (ERPs) during a standard oddball task were recorded in 57 schizophrenic patients and 33 normal controls. The P300 amplitude at T3 was not significantly smaller than that at T4 in schizophrenic patients. In the ANOVA analysis of the P300 peak amplitude and PCA factor scores, significant lateral topographical differences in P300 were not present between patients and controls. However, in schizophrenia, patients in the low T3 P300 group were older and consuming higher doses of antipsychotic medicine than those in the high T3 P300 group, and they had relatively low P300 amplitudes and significantly delayed P300 latency, compared with those in the high T3 P300 group. These findings suggested that although the reduction in the left temporal P300 amplitude did not necessarily exist in schizophrenic patients, it may be associated with the severity of the disease process and/or impairment of cognitive function.

Variation of temporal characteristics in human cerebral hemodynamic responses to electric median nerve stimulation: a near-infrared spectroscopic study

Using near-infrared spectroscopy, we studied cerebral hemodynamic responses to electric median nerve stimulation in ten subjects. The recordings were conducted by optical fibers placed over the left scalp. Electric stimuli were delivered to contra- and ipsilateral median nerves, respectively. Hemodynamic responses in the secondary somatosensory cortex were observed following each median nerve stimulation, except for three drowsy subjects. The contralateral stimulation tended to induce a larger response. The degree of change in oxygenated hemoglobin was hardly related to stimulus intensities, and was augmented by attention. Four subjects showed long-lasting responses throughout the stimulus periods, while three other subjects revealed transient responses. Thus, taking account of the temporal activation patterns is necessary for proper interpretation of the hemodynamic response following electric nerve stimulation.

The Neuroanatomy of Autobiographical Memory: A Slow Cortical Potential Study of Autobiographical Memory Retrieval

Changes in slow cortical potentials recorded at the scalp were tracked while participants retrieved autobiographical memories and then held them in mind. During retrieval extensive areas over left frontal scalp exhibited marked negative dc shifts and a similar though smaller effect was also observed over right frontal regions. As a memory was formed and then held in mind, electrodes located over posterior temporal and occipital regions exhibited marked negative shifts. It is proposed that the left frontal negativity primarily reflects cortical activation associated with the operation of a complex retrieval process, whereas the later temporal and occipital negativity (the result of the retrieval process) reflects activation corresponding to the formation and maintenance of a detailed memory.

Neuroelectrical signs of selective attention to color in boys with attention-deficit hyperactivity disorder

In order to gain insight into the functional and macroanatomical loci of visual selective processing deficits that may be basic to attention-deficit hyperactivity disorder (ADHD), the present study examined multi-channel event-related potentials (ERPs) recorded from 7- to 11-year-old boys clinically diagnosed as having ADHD ( n=24) and age-matched healthy control boys ( n=24) while they performed a visual (color) selective attention task. The spatio-temporal dynamics of several ERP components related to attention to color were characterized using topographic profile analysis, topographic mapping of the ERP and associated scalp current density distributions, and spatio-temporal source potential modeling. Boys with ADHD showed a lower target hit rate, a higher false-alarm rate, and a lower perceptual sensitivity than controls. Also, whereas color attention induced in the ERPs from controls a characteristic early frontally maximal selection positivity (FSP), ADHD boys displayed little or no FSP. Similarly, ADHD boys manifested P3b amplitude decrements that were partially lateralized (i.e., maximal at left temporal scalp locations) as well as affected by maturation. These results indicate that ADHD boys suffer from deficits at both relatively early (sensory) and late (semantic) levels of visual selective information processing. The data also support the hypothesis that the visual selective processing deficits observed in the ADHD boys originate from deficits in the strength of activation of a neural network comprising prefrontal and occipito-temporal brain regions. This network seems to be actively engaged during attention to color and may contain the major intracerebral generating sources of the associated scalp-recorded ERP components.

Pilomatrix carcinoma: A report of a case arising from a previously excised pilomatrixoma and a review of the literature

A 63-year-old woman was evaluated in 1995 for a nodule on the left parietal scalp. Biopsy revealed pilomatrixoma. The lesion was treated by curettage. The patient returned to the clinic in March of 1998 with a 2-month history of a rapidly growing nodule at the surgical site. Histology showed changes consistent with pilomatrix carcinoma. We will discuss the malignant transformation of a common hair matrix tumor and review the literature. (J Am Acad Dermatol 2001;44:358-61.)

Neurophysiological Indices of Language Impairment in Children

Recent investigations of children with specific language impairment (SLI) have found deviant anatomical asymmetry of the perisylvian cortex. These studies argue that this deviant anatomical asymmetry is linked to the language disorders of SLI children. To date no studies have examined whether deviant functional asymmetry underlies the processing of spoken language in these children. In the current study, brain-electrical activity was recorded from 31 scalp sites while children with SLI listened to auditorally presented stories and two different nonsense contexts. Electrical activity was time-locked to the grammatical word ''the'' in these contexts. The SLI children showed reversed asymmetry compared to control children from 200 ms to 400 ms in processing ''the'' in all contexts. More specifically, they showed depressed processing at the left temporal scalp site (T7) and enhanced processing at the right temporal site (T8). The second spatial derivative (the Laplacian) of the voltage activity was calculated to remove constant voltage potential and uniform changes in voltage potential across the scalp. The Laplacian analysis indicated that the sources of the positive electrical activity seen at the temporal electrode sites T7 and T8 are the lateral surfaces of the temporal cortices. A comparison of the scalp topography of the voltage potentials and Laplacian also suggests that children with SLI lack some contribution from a deep neural generator, possibly in the hippocampus or basal ganglia. This investigation is the first to demonstrate a direct link between deviant neurophysiological asymmetry and the processing of spoken language in children with SLI.

Left temporal deficit of P300 in patients with schizophrenia: effects of task

P300 is often, but not always, observed to be more reduced over left than right temporal lobes in patients with schizophrenia. The possibility that task differences contribute to the inconsistency in the literature was explored in this study. ERPs were collected from 17 right-handed men with schizophrenia (DSM-IIIR) and 11 right-handed healthy male community controls, performing three auditory oddball tasks — respond to a target tone by: (1) counting; (2) pressing a response button with the right index finger; or (3) pressing a response button with the left index finger. Although patients with schizophrenia had smaller and later P300 amplitudes than controls, they did not have smaller P300s over the left temporal scalp (T3) than over the right (T4). P300 recorded over the left (C3) and right (C4) motor cortices indicated sensitivity to responding hand, with greater negativity being associated with contralateral button pressing. Failure to find P300 asymmetry is not related to the presence or absence of a button pressing task, or the hand used for button pressing. Rather, P300 asymmetry may be related to structural neuroanatomical asymmetries.