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Biomedical subjects

B Gordon

Publications and source records attributed to B Gordon.

At least 37 records · Page 2Linked to original sources
PubMed1999

Brief bursts of pulse stimulation terminate afterdischarges caused by cortical stimulation.

OBJECTIVE: To determine whether cortical electrical stimulation can terminate bursts of epileptiform activity in humans, we used afterdischarges (ADs) as a model of epileptiform activity. METHODS: Cortical stimulation was performed for clinical localization purposes using subdural electrodes implanted in patients undergoing preresection evaluations for treatment of medically intractable seizures. We used 0.3-millisecond pulses of alternating polarity, repeated at 50 pulses/second. When stimulation produced AD, we often applied short additional brief bursts of pulse stimulation (BPS). We examined the effectiveness of BPS in aborting ADs in 17 patients using survival analysis. RESULTS: With BPS, ADs stopped within 2 seconds in 115 cases, 2 to 5 seconds in 22 cases, and in more than 5 seconds in 89 cases. Without BPS, ADs stopped within 2 seconds in 21 cases, 2 to 5 seconds in 114 cases, and in more than 5 seconds in 340 cases. BPS was an effective method to abort ADs (Cox proportional hazards model: p<0.0001). At any time during the course of ADs, the instantaneous rate of stopping ADs within 2 seconds after BPS was applied was 4.6 times greater than when BPS was not applied (95% CI = 3.7, 5.7). In eight cases, ADs progressed to the occurrence of clinical seizures, always when BPS was not applied. CONCLUSIONS: Afterdischarges significantly decreased in duration after we applied brief bursts of pulse stimulation. Although afterdischarges are not identical to spontaneous epileptiform activity, these results support the idea that electrical stimulation, applied in an appropriate manner at seizure onset, could abort seizures in humans.

Adolescent↗
PubMed1999

Making sense out of jargon: a neurolinguistic and computational account of jargon aphasia.

OBJECTIVE: To identify the cognitive and neuroanatomic bases of neologistic jargon aphasia with spared comprehension and production of written words. METHODS: Detailed analysis of performance across experiments of naming, reading, writing, repetition, and word/picture matching by a 68-year-old woman (J.B.N.) served to identify which cognitive mechanisms underlying naming and word comprehension were impaired. J.B.N.'s impairments were then simulated by selectively "lesioning" a computer model of word production that has semantic, word form, and subword phonologic levels of representation (described by Dell in 1986). RESULTS: In comprehension experiments, J.B.N. made far more errors with spoken word input than with written word or picture input (chi-square = 40-59; df = 1; p < 0.0001) despite intact auditory discrimination. In naming experiments (with picture, definition, or tactile input), J.B.N. made far more errors in spoken output relative to written output (chi-square = 14-56; df = 1; p < 0.0001). These selective impairments of spoken word processing were simulated by reducing connection strength between word-level and subword-level phonologic units but maintaining full connection strength between word-level and semantic units in Dell's model. The simulation yielded a distribution of error types that was nearly identical to that of J.B.N., and her CT and MRI scans showed a small subarachnoid hemorrhage in the left sylvian fissure without infarct. Cerebral angiogram showed focal vasospasm in sylvian branches of the left middle cerebral artery. CONCLUSION: Focal left perisylvian dysfunction can result in a highly selective "disconnection" between word-level and subword-level phonologic representations manifest as neologistic jargon aphasia with intact understanding and production of written words.

Aged↗
PubMed1999

Colesevelam hydrochloride (cholestagel): a new, potent bile acid sequestrant associated with a low incidence of gastrointestinal side effects.

OBJECTIVES: To compare colesevelam hydrochloride (Cholestagel), a nonabsorbed hydrogel with bile acid-sequestering properties, with placebo for its lipid-lowering efficacy, its effects on laboratory and clinical safety parameters, and the incidence of adverse events. METHODS: Following diet and placebo lead-in periods, placebo or colesevelam was administered at 4 dosages (1.5, 2.25, 3.0, or 3.75 g/d) for 6 weeks with morning and evening meals to men and women with hypercholesterolemia (low-density lipoprotein cholesterol level >4.14 mmol/L [>160 mg/dL]). Patients returned to the clinic every 2 weeks throughout the treatment period for lipid parameter measurements and adverse event assessments. Samples were collected for serum chemistry profiles, hematologic studies, coagulation studies, and vitamin level assessment at baseline and after 6 weeks of treatment. RESULTS: Among the 149 patients randomized, 137 completed the study. Low-density lipoprotein cholesterol concentrations decreased in a dosage-dependent manner by 0.11 mmol/L (4.2 mg/dL) (1.8%) in the 1.5-g/d colesevelam treatment group and up to 1.01 mmol/L (39 mg/dL) (19.1%) in the 3.75-g/d colesevelam treatment group. Low-density lipoprotein cholesterol concentrations at the end of treatment were significantly reduced from baseline levels in the 3.0- and 3.75-g/d colesevelam treatment groups (P = .01 and P<.001, respectively). Total cholesterol levels demonstrated a similar response to colesevelam treatment, with an 8. 1% decrease from baseline in the 3.75-g/d treatment group (P<.001). High-density lipoprotein cholesterol levels rose significantly in the 3.0- and 3.75-g/d colesevelam treatment groups, by 11.2% (P=.006) and 8.1% (P=.02), respectively. Median triglyceride levels did not change from baseline, nor were there any significant differences between treatment groups. The incidence of adverse events was similar among all groups. CONCLUSIONS: Colesevelam therapy is effective for lowering low-density lipoprotein cholesterol concentrations in persons with moderate hypercholesterolemia. It lacks the constipating effect of other bile acid sequestrants, demonstrating the potential for increased compliance.

Adult↗
PubMed1999

The screening and diagnosis of autistic spectrum disorders.

The Child Neurology Society and American Academy of Neurology recently proposed to formulate Practice Parameters for the Diagnosis and Evaluation of Autism for their memberships. This endeavor was expanded to include representatives from nine professional organizations and four parent organizations, with liaisons from the National Institutes of Health. This document was written by this multidisciplinary Consensus Panel after systematic analysis of over 2,500 relevant scientific articles in the literature. The Panel concluded that appropriate diagnosis of autism requires a dual-level approach: (a) routine developmental surveillance, and (b) diagnosis and evaluation of autism. Specific detailed recommendations for each level have been established in this document, which are intended to improve the rate of early suspicion and diagnosis of, and therefore early intervention for, autism.

Asperger Syndrome↗
PubMed1999

Critical period for the monocular deprivation effect in rats: assessment with sweep visually evoked potentials.

Rats and mice are the species most frequently used for cellular and biochemical studies of plasticity, but only a few studies have examined developmentally regulated visual plasticity in these species. Here we report a study of the critical period for monocular deprivation in Long-Evans rats in which visual pattern sweep evoked potentials (sweep VEP) was used. Successful recording of sweep VEPs depended on establishing a stable light plane of anesthesia. We found a mixture of halothane and NO2 to be suitable. During a single trial lasting 10 s, anesthetized rats (n = 28) viewed a sinusoidal contrast grating (spatial frequency of 0.13 cycles/deg) that reversed phase at 3 Hz. During the trial, the grating contrast increased logarithmically from 1 to 70%. Extracellular recording pipettes were placed bilaterally in layers II/III of the binocular regions of primary visual cortex. Stimulating the right and left eye on alternate trials, sweep VEP amplitudes were collected for 30 trials from each eye. In monocularly deprived animals, the right eyelid had been sutured for 5 days before recording. Age at suture varied from P19 to P86. In 12 of 13 rats sutured between P19 and P50, the crossed response from the deprived eye was smaller than the crossed response from the nondeprived eye. The same relation prevailed for the uncrossed responses in 11 of 13 animals. There was no significant monocular deprivation effect in animals sutured between P55 and P86 (n = 9). Dark rearing until approximately P90 followed by 5 days of eyelid suture resulted in a strong monocular deprivation effect in both crossed and uncrossed pathways (n = 3). There was little effect of dark rearing alone on the size the sweep VEPs (n = 3). The critical period reported here lasts at least 2 wk longer than reported for rats by Fagliolini et al. and for mice by Gordon and Stryker. Both previous studies used single unit recording rather than the sweep VEP method.

Animals↗
PubMed1999

Injection of MK-801 affects ocular dominance shifts more than visual activity.

Kittens were given intramuscular injections of the N-methyl--aspartate (NMDA) antagonist MK-801 twice daily (morning and midday) during the peak of the period of susceptibility for ocular dominance changes. They were then exposed to light with one eye closed for 4 h after each injection. The ocular dominance of these kittens was shifted significantly less than that of kittens injected with saline and exposed to light over the same period at the same age. After recording a sample of cells for an ocular dominance histogram, the kittens were injected with the same dose of MK-801 that was used during rearing to observe its effect on the activity of single cells in the visual cortex. In the majority of cells (7/13) there was no significant change in activity. Positive evidence for a reduction in activity was seen in only a minority (3/13) of cells. In a separate series of experiments, dose-response curves were measured for cells in the visual cortex in response to iontophoresis of NMDA or alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA), and the effect of an injection of MK-801 on these curves was measured. MK-801, at doses similar to those used in the ocular dominance experiments, had a significant effect on the dose-response curves for NMDA, but little effect on the dose-response curves for AMPA, or the visual responses of the cells. We conclude that ocular dominance shifts can be reduced significantly by a treatment that has little effect on the level of activity of cells in the visual cortex but does specifically affect the responses of the cells to NMDA as opposed to the responses to AMPA.

Algorithms↗
PubMed1999

Congenital thyroid disease revisited: migrational anomalies and dyshormonogenesis.

Nuclear medicine scintigraphy, in conjunction with other diagnostic tools, plays a vital role in assessing patients with congenital migrational anomalies. We present 5 patients, 4 of whom were hypothyroid and 1 patient who was euthyroid. Scintigraphic and ultrasonographic images were examined and correlated with laboratory results. These patients demonstrate the spectrum of migrational anomalies of the thyroid. Nuclear medicine scintigraphy was a valuable aid in establishing the location of the ectopic thyroid as well as its function.

Adolescent↗
PubMed1998

Temporal dynamics of verbal object comprehension.

Knowledge of the stage composition and the temporal dynamics of human cognitive operations is critical for building theories of higher mental activity. This information has been difficult to acquire, even with different combinations of techniques such as refined behavioral testing, electrical recording/interference, and metabolic imaging studies. Verbal object comprehension was studied herein in a single individual, by using three tasks (object naming, auditory word comprehension, and visual word comprehension), two languages (English and Farsi), and four techniques (stimulus manipulation, direct cortical electrical interference, electrocorticography, and a variation of the technique of direct cortical electrical interference to produce time-delimited effects, called timeslicing), in a subject in whom indwelling subdural electrode arrays had been placed for clinical purposes. Electrical interference at a pair of electrodes on the left lateral occipitotemporal gyrus interfered with naming in both languages and with comprehension in the language tested (English). The naming and comprehension deficit resulted from interference with processing of verbal object meaning. Electrocorticography indices of cortical activation at this site during naming started 250-300 msec after visual stimulus presentation. By using the timeslicing technique, which varies the onset of electrical interference relative to the behavioral task, we found that completion of processing for verbal object meaning varied from 450 to 750 msec after current onset. This variability was found to be a function of the subject's familiarity with the objects.

Adult↗
PubMed1998

A study of the efficacy of a comprehensive memory enhancement program in healthy elderly persons.

Well educated, high functioning older adults (ages 60-90) were given a comprehensive memory enhancement training program to determine the effectiveness of the program in increasing cognitive performance and positively influencing self-assessments of memory efficacy. The 68 subjects who participated in the memory enhancement training were compared to 74 subjects who were enrolled in a video control group. Between subject differences were analyzed prior to the interventions and at three time points following the interventions (immediately post, 3 months and 6 months). Only one cognitive measure, assessing verbal memory, revealed a significant difference between the groups, with participants in the memory enhancement group showing less decline from baseline than the video control group immediately following the intervention but with no difference between groups at 6 months post-intervention. Several self-report measures showed that the memory enhancement training subjects experienced improved memory functioning and decreased memory concerns relative to the video control group. The self-reported effects of the training were sustained over the 6-month follow-up period.

Adult↗
PubMed1998

Increased platelet transfusion requirement is associated with multiple organ dysfunctions in patients undergoing hematopoietic stem cell transplantation.

Organ dysfunction following hematopoietic stem cell transplantation (HSCT) may be a manifestation of a systemic inflammatory response. We speculate that part of the platelet transfusion requirement in HSCT patients results from this systemic inflammatory response, and increased transfusion requirement would be associated with, or precede, organ dysfunction. We studied 199 adults undergoing autologous (n=173) or allogeneic (n=26) HSCT. Patients with CNS (P=0.008) or pulmonary (P=0.002) dysfunction, or with VOD (P=0.05) received a higher mean number of platelet transfusions per week than patients who did not have these dysfunctions. Furthermore, a higher number of platelet transfusions during any 1 week period was significantly associated with development of pulmonary (P=0.0002) or renal (P < 0.0001) dysfunction in the following week. This predictive value was strongest early in the HSCT course, but remained significant over all 4 weeks. In multivariate analysis the number of platelet transfusions during the previous week was independently predictive for development of pulmonary dysfunction in week 2 (P=0.01) and week 3 (P=0.055). We believe that occurrence of increased platelet transfusion requirement prior to onset of dysfunction is consistent with the concept that an antecedent inflammatory response results in both platelet consumption and various organ dysfunctions. Increased platelet transfusion requirement may act as an early marker of subsequent organ dysfunction. Additionally, there may be a direct role of platelets in the development and progression of organ dysfunction in HSCT patients.

Adolescent↗
PubMed1998

Functional mapping of human sensorimotor cortex with electrocorticographic spectral analysis. I. Alpha and beta event-related desynchronization.

Human scalp EEG studies have shown that event-related desynchronization (ERD) in the alpha (8-13 Hz) and beta (15-25 Hz) bands may be used to detect functional activation of sensorimotor cortex. However, in most previous studies somatotopy has not been examined in detail and brief, self-paced movements, focusing on the planning of motor output, have been used. We recorded electrocorticographic (ECoG) signals in five clinical subjects during a visual-motor decision task that was designed to activate the representations of different body parts in sensorimotor cortex. To focus more on execution of motor output than on its planning, subjects were instructed to make sustained isometric muscle contractions in different body parts (tongue protrusion, fist-clenching or foot dorsiflexion) in response to randomized visual stimuli depicting each action. ECoG spectral analysis utilized a mixed-effects analysis of variance model in which within-trial temporal dependencies were taken into account, and the magnitude and statistical significance of alpha and beta ERDs were mapped onto a surface rendering of each subject's brain MRI. Cortical electrical stimulation was performed in all subjects for clinical purposes, and the resulting maps of sensorimotor function were compared with those generated by ECoG spectral analysis. During the early phases of the motor responses, alpha ERD commonly occurred in a diffuse spatial pattern that was not somatotopically specific. During the late phases, the spatial pattern of alpha ERD usually became more focused and somatotopically specific. Maps of alpha ERD were closer to cortical stimulation maps when alpha ERD was sustained throughout the late phases of the motor responses. Thus, the topography of alpha ERD more resembled traditional somatotopy when its temporal profile approximated that of the motor response. The topography of beta ERD was often more discrete and somatotopically specific than that of alpha ERD, but beta ERD was often transient and sometimes absent. Sometimes, unilateral limb movement produced sustained alpha and beta ERD over bilateral sensorimotor cortices, with overlapping patterns for different body parts. The topographical spread of alpha ERD beyond expected functional-anatomical boundaries during early (and sometimes late) phases of motor responses invites a re-examination of traditional assumptions about sensorimotor functional neuroanatomy, as well as the role of alpha ERD as an index of cortical activation. We agree with others that the somatotopic representations of different body parts overlap more than previously thought. Also, unilateral limb movements may be associated with both contralateral and ipsilateral activation of sensorimotor cortex. We conjecture that alpha ERD may reflect activity within a broad synaptic network with distributed cortical representations.

Adult↗
PubMed1998

Functional mapping of human sensorimotor cortex with electrocorticographic spectral analysis. II. Event-related synchronization in the gamma band.

It has been shown in animals that neuronal activity in the 'gamma band' (>30 Hz) is associated with cortical activation and may play a role in multi-regional and multi-modal integration of cortical processing. Studies of gamma activity in human scalp EEG have typically focused on event-related synchronization (ERS) in the 40 Hz band. To assess further the gamma band ERS further, as an index of cortical activation and as a tool for human functional brain mapping, we recorded subdural electrocorticographic (ECoG) signals in five clinical subjects while they performed visual-motor decision tasks designed to activate the representations of different body parts in sensorimotor cortex. ECoG spectral analysis utilized a mixed-effects analysis of variance model in which within-trial temporal dependencies were accounted for. Taking an exploratory approach, we studied gamma ERS in 10-Hz-wide bands (overlapping by 5 Hz) ranging from 30 to 100 Hz, and compared these findings with changes in the alpha (8-13 Hz) and beta (15-25 Hz) bands. Gamma ERS (observed in three out of subjects) occurred in two broad bands-'low gamma' included the 35-45 and 40-50 Hz bands, and 'high gamma' the 75-85, 80-90, 85-95 and 90-100 Hz bands. The temporal and spatial characteristics of low and high gamma ERS were distinct, suggesting relatively independent neurophysiological mechanisms. Low gamma ERS often began after onset of the motor response and was sustained through much of it, in parallel with event-related desynchronization (ERD) in the alpha band. High gamma ERS often began during, or slightly before, the motor response and was transient, ending well before completion of the motor response. These temporal differences in low and high gamma suggest different functional associations with motor performance. Compared with alpha and beta ERD, the topographical patterns of low and high gamma ERS were more discrete and somatotopically specific and only occurred over contralateral sensorimotor cortex during unilateral limb movements (alpha and beta ERD were also observed ipsilaterally). Maps of sensorimotor function inferred from gamma ERS were consistent with maps generated by cortical electrical stimulation for clinical purposes. In addition, different task conditions in one subject produced consistent differences in both motor response latencies and onset latency of gamma ERS, particularly high gamma ERS. Compared with alpha and beta ERD, the topography of gamma ERS is more consistent with traditional maps of sensorimotor functional anatomy. In addition, gamma ERS may provide complementary information about cortical neurophysiology that is useful for mapping brain function in humans.

Adult↗
PubMed1998

The Ipswich Childbirth Study: 1. A randomised evaluation of two stage postpartum perineal repair leaving the skin unsutured.

OBJECTIVE: To evaluate a policy of two stage postpartum perineal repair leaving the skin unsutured. DESIGN: A stratified randomised controlled trial using a 2 x 2 factorial design. SETTING: The maternity unit at Ipswich Hospital NHS Trust, a district general hospital, between 1992 and 1994. SAMPLE: 1780 women requiring surgical repair of episiotomy or first or second degree tear following a spontaneous or simple instrumental delivery. METHODS: A policy of two-stage perineal repair leaving skin unsutured was compared with a policy of three stage repair including skin closure with interrupted or subcuticular sutures. Both groups were assessed by a research midwife, blind to the allocation, completing questionnaires at 24 to 48 hours and 10 days postpartum, and by self-completed questionnaires at three months after birth. MAIN OUTCOME MEASURES: 1. 24 to 48 hours postpartum: perineal pain; healing; 2. 10 days postpartum: perineal pain, healing and removal of sutures; 3. three months postpartum: perineal pain, removal of sutures, resuturing, dyspareunia, and failure to resume pain-free intercourse. RESULTS: Completed questionnaires were returned for 99% of women at both 24 to 48 hours and ten days and by 93% of women three months postpartum. No differences were detected in perineal pain at 24 to 48 hours (62% vs 64%; RR 0.96, 95% CI 0.90-1.03; 2P = 0.3) and 10 days (25% vs 28%; RR 0.90, 95% CI 0.77-1.06; 2P = 0.2). Significantly fewer women allocated to two-stage repair reported tight stitches at ten days (14% vs 18%; RR 0.77, 95% CI 0.62-0.96, 2P = 0.02); similar numbers of repairs were judged to be breaking down (five compared with seven women). At three months postpartum fewer women allocated to the two-stage repair reported perineal pain and more had resumed pain-free intercourse. Amongst women who had resumed intercourse there was a significant difference in dyspareunia (15% vs 19%; RR 0.80, 95% CI 0.65-0.99; 2P = 0.04). Significantly fewer women in the two-stage repair group (7% vs 12%; RR 0.61, 95% CI 0.45-0.83; 2P = < 0.01) reported removal of suture material. Four women in the two-stage repair group had required resuturing, compared with nine allocated to the three-stage repair. CONCLUSIONS: Two-stage repair of perineal trauma leaving the skin unsutured appears to reduce pain and dyspareunia three months postpartum. There are no apparent disadvantages, in particular no evidence of an increased risk of breakdown of the repair and resuturing.

Adult↗
PubMed1998

The Ipswich Childbirth Study: 2. A randomised comparison of polyglactin 910 with chromic catgut for postpartum perineal repair.

OBJECTIVE: To compare polyglactin 910 sutures with chromic catgut sutures for postpartum perineal repair. DESIGN: A stratified randomised controlled trial, using a 2 x 2 factorial design. SETTING: The maternity unit at Ipswich Hospital NHS Trust, a district general hospital, between 1992 and 1994. SAMPLE: 1780 women who had sustained an episiotomy or first or second degree tear following a spontaneous or simple instrumental delivery. METHODS: Policies of repair with polyglactin 910 or chromic catgut were compared. Both groups were assessed by a research midwife completing questionnaires at 24 to 48 hours and at ten days postpartum, and by self-completed questionnaires at three months after birth. MAIN OUTCOME MEASURES: 1. 24 to 48 hours postpartum: perineal pain, healing; 2. ten days postpartum: perineal pain, healing and removal of sutures; 3. three months postpartum: perineal pain, removal of sutures, resuturing, dyspareunia, and failure to resume pain-free intercourse. RESULTS: Completed questionnaires were returned for 99% of women at both 24 to 48 hours and ten days and by 93% of women three months postpartum. The two groups were similar at trial entry. Significantly fewer women allocated to the polyglactin 910 reported pain in the previous 24 hours at both 24 to 48 hours (59% vs 67%; RR 0.89, 95% CI 0.83-0.95; 2P < 0.01), and ten days (24% vs 29%; RR 0.81, 95% CI 0.69-0.95; 2P = 0.01). At three months postpartum there was no clear difference between the groups in terms of perineal pain, dyspareunia or failure to resume pain-free intercourse. More women in the polyglactin 910 group reported that some suture material had been removed (12% vs 7%; RR 1.62, 95% CI 1.19-2.21; 2P < 0.01). Three women in the polyglactin 910 group had required resuturing compared with ten in the chromic catgut group (RR 0.30; 95% CI 0.08-1.09; 2P = 0.1). CONCLUSIONS: Using polyglactin 910 rather than chromic catgut for perineal repair leads to about one fewer women among every 20 having perineal pain and using analgesia ten days postpartum. Its only apparent disadvantage is that more women, again estimated as 1 in 20, report having material removed during healing. Data from this and other trials suggest that for every 100 women repaired with a polyglycolic acid-based material, about one fewer will require resuturing.

Adult↗
PubMed1998

Motor and sensory mapping of the frontal and occipital lobes.

In patients with intractable epilepsy, surgical resections are performed with the primary goal of improving seizure control. The risk is that the resections may also remove tissues crucial for normal activities. The goal of surgical planning is therefore to determine as accurately as possible the regions of seizure onset and the regions controlling important functions, so that one can determine what to remove and what to leave in place. Clinical functional localization has been performed using cortical stimulation for over half a century, using both intraoperative and extraoperative methods. Signal averaging also has been widely used. More recently, techniques based on analysis of EEG in the frequency domain have shown promise. The methods appear to accurately indicate the function of the region assessed but do not necessarily predict functional consequences of resection. We review these methods, their indications, and the results obtained by their use.

Brain Mapping↗
PubMed1998

Right hemisphere speech perception revealed by amobarbital injection and electrical interference.

OBJECTIVE: To investigate the right hemispheric speech perception capabilities of an adult right-handed patient with seizures. METHODS: Consecutive, unilateral, intracarotid sodium amobarbital injections and left hemispheric electrical interference mapping were used to determine lateralization and localization of speech perception, measured as syllable discrimination. RESULTS: Syllable discrimination remained intact after left and right intracarotid sodium amobarbital injections. Language otherwise strongly lateralized to the left hemisphere. Despite evidence of bilateral speech perception capabilities, electrical interference testing in the left posterior temporal lobe impaired syllable discrimination. CONCLUSIONS: The results suggest a functionally symmetric, parallel system in the adult brain with preferential use of left hemispheric pathways for speech perception.

Adult↗