Human cortical activity during vestibular- and drug-induced nausea detected using MSI.
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Brain Mapping↗
Biomedical subjects
H A Rowley
Publications and source records attributed to H A Rowley.
Magnetic source imaging and the neural basis of dyslexia.
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Brain↗
Comparison of late components in simultaneously recorded event-related electrical potentials and event-related magnetic fields.
We have attempted to define the late components of the event-related magnetic field (ERF) and to relate them to the late components of the event-related electrical potential (ERP). Simultaneous multichannel electroencephalogram (EEG) and magnetoencephalogram (MEG) were recorded in 13 subjects during an auditory oddball paradigm in two series of experiments. EEG responses to frequent tones consisted of the N1 and P2 components of the auditory vertex potential. Responses to rare tones consisted of N1, apparent P2, N2 and P3 components. All EEG components were best seen in the midline and were highly reproducible for all subjects. MEG responses to frequent tones consisted of N1m and P2m components that were highly reproducible only when recorded over the temporal region. By contrast, the ERF to rare tones was less well defined and only the N1m component could be identified satisfactorily. There was little consistent activity in the MEG at the time of occurrence of the N2 and P3 components of the ERP.
Acoustic Stimulation↗
Noninvasive somatosensory monitoring of the injured inferior alveolar nerve using magnetic source imaging.
PURPOSE: This study evaluates magnetoencephalography (MEG) as an objective monitor for the evaluation of post-traumatic inferior alveolar nerve injuries. MATERIALS AND METHODS: Six patients with unilateral inferior alveolar nerve injuries were assessed using conventional sensory examination techniques. All damaged nerves, and their contralateral controls, were then reexamined using MEG technology. Regions of somatosensory-induced magnetic activity were superimposed on three-dimensional magnetic resonance imaging (MRI) scans to give cortical magnetic source images (MSI). All patients subsequently underwent surgical exploration of the damaged nerves. RESULTS: All six patients had no sensitivity to conventional testing on the damaged side. On evaluation with MEG, all six control nerves had an appropriate cortical signal in response to repetitive lip stimulation. Somatosensory stimulation of two of the six damaged nerves resulted in cortical magnetic field changes. Surgical exploration showed that the four nerves with negative MEG tests had discontinuity defects. In contrast, the two patients with positive MEG signals had intact nerves. CONCLUSION: This technology may differentiate between intact but damaged nerves and transected nerves.
Adult↗
Task-induced asymmetry of the auditory evoked M100 neuromagnetic field elicited by speech sounds.
The auditory evoked neuromagnetic fields elicited by synthesized speech sounds (consonant-vowel syllables) were recorded in six subjects over the left and right temporal cortices using a 37-channel SQUID-based magnetometer. The latencies and amplitudes of the peaks of the M100 evoked responses were bilaterally symmetric for passively presented stimuli. In contrast, when subjects were asked to discriminate among the same syllabic stimuli, the amplitude of the M100 increased in the left and decreased in the right temporal cortices. Single equivalent current dipole modeling of the activity elicited by all stimulus-types localized to a well-circumscribed area in supratemporal auditory cortex. The results suggest that attentional modulation affects the two supratemporal cortices in a differential manner. Task-conditioned attention to speech sounds is reflected in lateralized supratemporal cortical responses possibly concordant with hemispheric language dominance.
Acoustic Stimulation↗
MR in partial epilepsy: value of high-resolution volumetric techniques.
PURPOSE: To assess the utility of high-resolution volumetric MR examinations with thin partition size for patients with simple partial epilepsies that were well located with electrical and clinical criteria. METHODS: Fifteen patients with normal standard MR findings were studied with three-dimensional Fourier transform volumetric MR examinations using thin (1 to 1.5 mm) partition size. Imaging was done in the coronal plane, then reformatted manually on an independent console with each gyrus analyzed in the planes parallel and perpendicular to its axis. RESULTS: Cortical abnormalities were detected in 8 of the 15 patients in the study. Surgical resection of the affected cortex in 2 patients showed polymicrogyria in one and dysplastic cortical organization in the other. CONCLUSION: In this preliminary study, 3-D Fourier transform volumetric MR examinations with thin partition size appeared to be useful in identifying cortical dysplasias in patients with localized simple partial epilepsies.
Adolescent↗
Functional localization by magnetoencephalography.
Magnetoencephalography combines the attributes of real-time millisecond temporal resolution with precise anatomic localization. In addition to characterizing spontaneous epileptiform discharges and slow wave activity, magnetoencephalography may be used to map sensorimotor, auditory, and visual functions. Magnetoencephalography functional data are registered to three-dimensional magnetic resonance imaging to provide a useful way to analyze the relationship of structure to function and to assist in surgical planning. Magnetoencephalography is noninvasive and can be done with rapid turn-around time, but it is expensive and is not optimal for all brain areas or functions. Future integration and cross-analysis of magnetoencephalography with other functional mapping modalities will likely prove to be complementary and of even greater use.
Auditory Cortex↗
Cladosporium trichoides cerebral phaeohyphomycosis in a liver transplant recipient. Report of a case.
Cerebral phaeohyphomycosis (also referred to as cerebral chromomycosis), one of the diseases caused by the dematiaceous (black) fungi, is most commonly caused by Cladosporium trichoides (referred to by some as Xylohypha bantiana) and is a rare disease, with 31 culture-proven cases reported to date. Although most cases have occurred in immunocompetent hosts, recent experimental evidence suggests that host immunosuppression may predispose patients to the disease. The authors report a case of fatal cerebral phaeohyphomycosis in a liver transplant patient, the first to occur in a transplant patient of any type, to the best of the authors' knowledge. This case provides support for the hypothesis that immunosuppressed patients may be at increased risk for development of this disease.
Brain Diseases↗
Thalamomesencephalic strokes after cocaine abuse.
Three young patients developed strokes of rostral midbrain and thalamus shortly following cocaine abuse. Two had infarctions and one had a hemorrhage, but none had clear risk factors other than cocaine for this relatively uncommon type of stroke. Toxicologic analysis confirmed isolated cocaine use in each patient. In the two cases of infarction studied angiographically, one had normal findings and the other had focal narrowing of the P1 segments of the posterior cerebral arteries bilaterally. Since the P1 segment has a uniquely sparse perivascular sympathetic supply, we suggest that direct adrenergic-mediated vasoconstriction is not critical to the production of cocaine-associated stroke.
Adult↗
Magnetic resonance imaging in amyotrophic lateral sclerosis.
Magnetic resonance imaging (MRI) was used in 5 patients with clinically definite amyotrophic lateral sclerosis to determine the frequency of central white matter abnormalities. Two patients had symmetrical areas of increased signal intensity seen on MRI extending from the cortex, through the corona radiata, posterior limb of the internal capsule, and cerebral peduncles into the pons. These MRI abnormalities presumably relate to the pathological changes observed by others in the central white matter of patients with amyotrophic lateral sclerosis.
Adult↗