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R J Chabot

Publications and source records attributed to R J Chabot.

11 recordsLinked to original sources
PubMed1995

QEEG and evoked potentials in central nervous system Lyme disease.

Quantitative EEG, flash visual evoked potentials, auditory evoked potentials to common and rare tones, and median nerve somatosensory evoked potentials were obtained from 12 patients with active CNS Lyme disease and from 11 patients previously treated for active CNS Lyme disease. Abnormal QEEG and/or EPs were found in 75% of the active Lyme disease patients and in 54% of the post CNS Lyme disease patients. Three different types of neurophysiological abnormality were observed in these patients including QEEG slowing, possible signs of cortical hyperexcitability, and focal patterns indicating disturbed interhemispheric relationships. In patients tested before and after treatment QEEG and EP normalization was associated with clinical improvement.

Adolescent↗
PubMed1992

Quantitative electroencephalography. A new approach to the diagnosis of cerebral dysfunction in systemic lupus erythematosus.

OBJECTIVE: Neuropsychiatric manifestations are common in patients with systemic lupus erythematosus (SLE), but accurate diagnosis is often difficult. We conducted a prospective study to determine the utility of neurometric quantitative electroencephalography (QEEG) as an indicator of cerebral dysfunction in SLE patients. METHODS: Fifty-two SLE patients were divided into 4 groups based on the results of neuropsychiatric evaluations. These included patients with objective evidence of neuropsychiatric SLE (NPSLE), patients with neuropsychiatric symptoms, patients with no evidence of NPSLE, and patients with a prior history of NPSLE: All QEEG findings were compared with data in an age-regressed normative database and with findings in an independent sample of normal subjects. RESULTS: QEEG sensitivity was 87%, and specificity was 75%. QEEG results were abnormal in 74% of the SLE patients with neuropsychiatric symptoms and in 28% of the patients with no evidence of active NPSLE: QEEG profiles varied as a function of the severity and type of neuropsychiatric manifestation present. Within this patient population, QEEG was more sensitive than magnetic resonance imaging, computed tomography scanning, or conventional EEG. CONCLUSION: Neurometric QEEG may be a sensitive indicator of cerebral dysfunction in patients with NPSLE and can differentiate patients with diverse neuropsychiatric manifestations. When combined with a careful clinical history and evaluation, QEEG provides information that may be useful for the early detection of NPSLE and for serial evaluation of disease activity and treatment efficacy.

Adult↗
PubMed1990

Quantitative EEG correlates of crack cocaine dependence.

Evidence for a distinctive syndrome of neuroadaptation in cocaine dependence has accumulated from behavioral, neurophysiological, and preclinical and clinical pharmacological studies. The authors report on the results of a preliminary investigation of the quantitative electroencephalographic (QEEG) correlates of severe DSM-III-R crack cocaine dependence in seven patients abstinent from cocaine for 1 to 68 days. The major QEEG finding was increased absolute and relative alpha power. Increased alpha power has also been reported in multiple previous studies of depressed patients. This series of crack-dependent patients showed significant depressive morbidity; four patients attempted suicide subsequent to initiating their use of crack and the group mean (+/- SD) Beck Depression Scale score was 18.9 (+/- 6.5). These results complement other studies that support the concept of neuroadaptation to chronic cocaine exposure. Prospective studies correlating QEEG measures with subsequent response to pharmacological interventions for cocaine dependence should be considered.

Adult↗
PubMed1989

Real-time intraoperative monitoring during neurosurgical and neuroradiological procedures.

A real-time intraoperative evoked potential (EP) monitoring system is described and evaluated. Unique features include (1) online artifact rejection to reduce noise contamination, (2) optimum digital filtering to improve the signal-to-noise ratio of the EP signal, (3) statistically defined confidence intervals to determine significant EP peak latency deviations, and (4) sliding windows of EP subaverages of various sizes to minimize feedback time to the surgeon. The reliability and validity of this system were determined by comparison with conventional intraoperative EP averaging and by examining the correlation of EP parameter changes with concurrent surgical and radiological manipulations. This system was clearly superior to conventional averaging systems. Reliable EPs could be obtained from neurologically compromised patients within the electrically hostile operating room environment, in cases in which conventional averaging failed to extract a stable EP signal. EP update times of 10-20 s were quite common and allowed direct moment-to-moment correlations with surgical and radiological events. Case histories are presented that show the utility of this system for aiding in the prevention of neurological complications. This utility is examined for neurosurgical and neuroradiological procedures involving spinal cord, brainstem, midbrain, and cortical structures, and affecting the somatosensory, motor, auditory, and visual system pathways.

Adult↗
PubMed1987

Response variability of somatosensory evoked potentials during scoliosis surgery.

Somatosensory evoked potentials (SSEP) were recorded from the scalp for intraoperative monitoring of patients undergoing surgical correction of spine deformities or spine fractures. Alterations in the SSEP with distraction, spine manipulation, anesthesia, hypotension, and other intraoperative variables are described. When loss of the SSEP occurred and a waiting period was undertaken until it returned, all patients with an SSEP present upon closing, which was within +/- 2 SD of their anesthetized control values, had no neurologic complications. Alterations in SSEP consisting of increases in latency of 15% and decreases in amplitude of 50% were not associated with any postoperative neurologic deficits.

Adolescent↗
PubMed1984

The late positive component of the evoked waveform II: Relationship to picture recognition processes.

Averaged evoked potentials were collected from Cz, C3', C4', and Pz while subjects made cognitive decisions about pairs of pictures using perceptual and semantic features. Decisions were made at three different levels within the picture recognition process. These levels correspond to feature detection and synthesis, and semantic memory activation at the basic category and superordinate category levels. The late positive component of the evoked waveform systematically varied as a function of the nature of the cognitive decision being made. The late positive component of the waveform was highly correlated with the response times associated with each experimental condition. It would appear that the late positive component of the waveform provides an internal index of the neural processes which accompany cognitive decisions. As such, the late positive component of the evoked waveform serves as a source of converging evidence, along with response latency measures, that the picture recognition process can be successfully tapped at several different levels within the information processing system. This work should be applicable for studying disruptions to the pattern recognition process which accompany stroke, head trauma, and neurological problems associated with learning disorders. It should also be sensitive to any disorder which influences central processing time more than early perceptual and peripheral processes.

Electroencephalography↗
PubMed1984

The late positive component of the evoked waveform: relationship to word recognition processes.

Averaged evoked potentials were collected from Cz, C3', C4', and Pz while subjects made perceptual and cognitive decisions about pairs of visually presented words. The nature and level of the decision being made was manipulated by varying the relationships between the two words presented Decisions were made at three different levels within the word recognition process. These levels corresponded to feature detection and synthesis, lexical access and naming, and semantic memory access at the superordinate category level. The late positive component of the evoked waveform varied systematically with the nature of the perceptual and cognitive decisions being made. The late positive component of the waveform was highly correlated with the response times associated with each of the three decision types. It would appear that the late positive component provides an internal index of the neural processes which accompany cognitive decisions. Specifically, the late positive component appears to reflect the time course of stimulus evaluation and comparison processes. The response time data and the evoked waveform provide converging sources of evidence in support of the notion that the word recognition process can be selectively tapped at several different levels within the information processing system.

Adult↗
PubMed1983

Developmental and reading ability differences in accessing information from semantic memory.

A categorical judgment task was utilized to investigate the relationships between word recognition skills and reading achievement at several grade levels. In the first experiment skilled and unskilled readers from Grades 2, 4, and 6 made cognitive decisions about pairs of words using either graphemic, lexical, or semantic information. In Experiment 2 skilled, average, and unskilled readers from Grades 1, 3, and 5 made semantic decisions about word or picture pairs. The speed and accuracy of word encoding, lexical access, and semantic memory access processes varied as a function of reading ability. These results suggest that inefficient word recognition skills can contribute to reading deficiencies as can deficiencies in semantic memory organization.

Achievement↗
PubMed1983

Adult age differences in accessing and retrieving information from long-term memory.

The present study employed a series of cognitive decision tasks to investigate adult age differences in accessing and retrieving information from long-term memory. Young and old adults, from low and high education populations, were required to make feature, lexical, and categorical judgments about word pairs. Older adults were slower than younger adults at feature extraction, lexical access, and accessing category information. The age deficit was proportionally greater when retrieval of category information was required. The results suggest that one contribution to the diminished processing capacity in elderly adults may be their slower semantic access speed.

Adolescent↗