Biomedical subjects

J J Barton

Publications and source records attributed to J J Barton.

At least 19 recordsLinked to original sources

PubMed2001

Covert recognition in acquired and developmental prosopagnosia.

BACKGROUND: Some patients with prosopagnosia have covert recognition, meaning that they retain some familiarity or knowledge of facial identity of which they are not aware. OBJECTIVE: To test the hypothesis that prosopagnosic patients with right occipitotemporal lesions and impaired face perception lack covert processing, whereas patients with associative prosopagnosia and bilateral anterior temporal lesions possess it. METHODS: Eight patients with prosopagnosia were tested with a battery of four face recognition tests to determine their ability to discriminate between famous and unknown faces. RESULTS: Measures of overt familiarity revealed better residual discrimination in patients with acquired prosopagnosia than in those with the developmental form. With forced-choice methods using famous faces paired with unknown faces, no patient demonstrated covert familiarity. However, when the semantic cue of the name of the famous face was provided, covert processing was present in all five patients with acquired prosopagnosia, including the three with extensive right-sided lesions and impaired perceptual discrimination of facial configuration. Sorting unrecognized faces by occupation was also performed above chance in three of these five patients. In contrast, none of the three patients with developmental prosopagnosia had covert processing, even though two demonstrated flawless performance on similar tests of name (rather than face) recognition. Overt familiarity correlated highly with the degree of covert recognition. CONCLUSIONS: Extensive right occipitotemporal lesions with significant deficits in face perception are not incompatible with covert face processing. Covert processing is absent in developmental prosopagnosia, because this condition likely precludes the establishment of a store of accurate facial memories. The presence of covert processing correlates with the degree of residual overt familiarity, indicating that these are related phenomena.

Adult↗

PubMed2001

A phase II study of combined oral uracil and ftorafur with leucovorin for patients with squamous cell carcinoma of the head and neck.

BACKGROUND: The objective of this Phase II study was to define the response rate, safety profile, and toxicity of oral uracil and ftorafur (UFT) with leucovorin (UFT/LV) as a palliative treatment for patients with squamous cell carcinoma of the head and neck (SCCHN). METHODS: Patients with metastatic or recurrent SCCHN with an Eastern Cooperative Oncology Group performance status < 2 and adequate organ function were enrolled in an institutional review board-approved trial. Prior induction or adjuvant chemotherapy was permitted provided 6 months had elapsed since the last chemotherapy. Patients were treated with UFT 300 mg/m(2) per day and leucovorin 90 mg per day administered in three doses daily for 28 days followed by a 7-day break for a 35-day cycle. Planned intrapatient dose modifications were based on individual toxicity. Patients were removed from the study for progression of disease or unacceptable toxicity. RESULTS: One hundred six cycles of UFT/LV had been administered to 42 patients as of January 1, 2000. The most common toxicities, in descending order of incidence, were anemia, pain, fatigue, diarrhea, nausea, mucositis, and anorexia. Clinically significant toxicities attributable to UFT/ LV were primarily gastrointestinal. On an intent-to-treat basis, three patients (7%) achieved a complete response, and six patients (14%) achieved a partial response. The overall response rate was 21% (95% confidence interval, 10--37%). CONCLUSIONS: UFT/LV therapy is feasible in this patient population and is generally well tolerated. Response rates are similar to the rates expected with continuous-infusion 5-fluorouracil. UFT/LV should be studied further both alone and in combination therapy for patients with SCCHN.

Administration, Oral↗

PubMed2001

The eye movements of pure alexic patients during reading and nonreading tasks.

We compared the eye-movements of two patients who read letter-by-letter (LBL) following a left occipital lobe lesion with those of normal control subjects and of hemianopic patients in two tasks: a nonreading visual search task and a text reading task. Whereas the LBL readers exhibited similar eye-movement patterns to those of the other two groups on the nonreading task, their eye movements differed significantly during reading, as reflected in the disproportionate increase in the number and duration of fixations per word and in the regressive saccades per word. Importantly, relative to the two control groups, letter-by-letter readers also made more fixations per word as word length increased, especially as word frequency and word imageability decreased. Two critical results emerged from these experiments: First, the alteration in the oculomotor behavior of the LBL readers during reading is similar to that seen in normal readers under difficult reading conditions, as well as in beginning readers and in those with developmental dyslexia, and appears to reflect difficulties in processing the visual stimulus. Second, the interaction of length with frequency and with imageability in determining the eye movement pattern is consistent with an interactive activation model of normal word recognition in which weakened activation of orthographic input can nevertheless engage high-level lexical factors.

Adult↗

PubMed2001

Mode of delivery and risk of respiratory diseases in newborns.

OBJECTIVE: To determine whether there is an increased incidence of persistent pulmonary hypertension in neonates delivered by cesarean, with or without labor, compared with those delivered vaginally. METHODS: We did a computerized retrospective review of 29,669 consecutive deliveries over 7 years (1992-1999). The incidences of persistent pulmonary hypertension of the newborn, transient tachypnea of the newborn, and respiratory distress syndrome (RDS) were tabulated for each delivery mode. Cases of persistent pulmonary hypertension were reviewed individually to determine delivery method and whether labor had occurred. The three groups defined were all cesarean deliveries, all elective cesareans, and all vaginal deliveries. RESULTS: Among 4301 cesareans done, 17 neonates had persistent pulmonary hypertension (four per 1000 live births). Among 1889 elective cesarean deliveries, seven neonates had persistent pulmonary hypertension (3.7 per 1000 live births). Among 21,017 vaginal deliveries, 17 neonates had persistent pulmonary hypertension (0.8 per 1000 live births). chi2 analysis showed an odds ratio 4.6 and P <.001 for comparison of elective cesarean and vaginal delivery for that outcome. CONCLUSION: The incidence of persistent pulmonary hypertension of the newborn was approximately 0.37% among neonates delivered by elective cesarean, almost fivefold higher than those delivered vaginally. The findings have implications for informed consent before cesarean and increased surveillance of neonates after cesarean.

Chicago↗

PubMed2001

Deficits in cortical visual function.

Lesions of extrastriate cortex cause selective defects in visual function. Damage to portions of the "ventral stream" in medial and inferior occipitotemporal cortex lead to impaired perception of color or various specific visual object recognition defects, such as prospagnosia, the inability to recognize familiar faces, and alexia, the inability to read. The latter must be distinguished from a variety of other reading defects related to primary visual, attentional, linguistic, or ocular motor impairments. Damage to the "dorsal stream" in lateral occipito-temporo-parietal regions impairs visuospatial capabilities, leading to akinetopsia (impaired motion perception) or Balint's syndrome, a loosely bound triad of simultanagnosia, optic ataxia, and ocular motor apraxia. Topographagnosia can occur with ventral or dorsoal lesions for different reasons. Considerable evidence has accumulated showing that residual vision or even "blindsight," which is visual perception in the absence of awareness, can persist after lesion of striate cortex in some patients.

Brain Diseases↗

PubMed2001

Discrimination of spatial relations and features in faces: effects of inversion and viewing duration.

We studied discrimination of changes in eye position, mouth position, and eye colour at viewing durations ranging from 1 second to unlimited time. With upright faces, perception was rapid and did not improve above 2 seconds viewing time. Face inversion impaired discrimination of mouth position significantly, eye position slightly, but not eye colour. The 'inversion effect' for mouth position decreased with increasing stimulus duration, and disappeared when the subject knew that the only change in a trial was in mouth position. A subsequent experiment showed that the inversion impairment in the mouth region was not specific to spatial position but affected mouth colour to a lesser degree. When the mouth region was made more salient by increasing the frequency of mouth change trials, the inversion effect for mouth position decreased, and correlated with an increase in inversion effect for eye position but not eye colour. We conclude that the dominant effect of face inversion upon perception is decreased discrimination in less salient facial regions, that this impairment lessens with increasing viewing time, and that it affects both features and their spatial relations, though the effect on the latter is greater. These results are consistent with greater dependence on a serial component search strategy in inverted faces.

Adolescent↗

PubMed2000

A phase II trial of palliative docetaxel plus 5-fluorouracil for squamous-cell cancer of the head and neck.

PURPOSE: A phase II study to determine the response rate and toxicity of docetaxel and 5-fluorouracil (5-FU) every four weeks ('TF'), in patients with incurable SCCHN. PATIENTS AND METHODS: Patients with metastatic or recurrent SCCHN with an ECOG PS < 3 were enrolled in an institutional review board approved trial. Prior induction or adjuvant chemotherapy was permitted provided six months had elapsed. The regimen was docetaxel 70 mg/m2 i.v., day 1 and 5-FU 800 mg/m2/d x 5 days, days 1-5, as a continuous intravenous infusion, repeated every 28 days. Planned intra-patient dose modifications were based on hematological, cutaneous, and gastrointestinal toxicities. Patients were removed from the study for progression of disease or unacceptable toxicity. RESULTS: Seventeen patients were enrolled. Fourty-six cycles of TF were administered. Reasons for discontinuance of TF included: progressive disease, 12 patients; toxicity, 3 patients; concomitant illness, 1 patient; death, 1 patient. The most common toxicities were neutropenia, mucositis, anemia, fatigue, alopecia, pain, diarrhea and nausea. Evaluation of responses to TF showed that there were four patients of seventeen (24%, 95% exact CI: 6.8-49.9) who achieved a PR or CR. Accrual was terminated after interim analysis of the response rate of the first 17 patients failed to exceed 4 of 17. CONCLUSIONS: The response rate to TF in patients with SCCHN was lower than expected. Trials of other regimens should take precedence over further exploration of the TF regimen.

Adult↗

PubMed2000

Ocular aspects of myasthenia gravis.

Ocular myasthenia gravis is a not uncommon autoimmune disorder causing diplopia, ptosis, and weakness of lid closure. The predilection of myasthenia for the ocular muscles may be related to differences between limb and extraocular muscles in either physiological function or antigenicity. Clinically, ocular myasthenia can mimic any form of pupil-sparing ocular motility disorder. Dynamic abnormalities of myasthenic eye movements may reflect the primary hallmarks of the disease, which are fatigability and variability in strength, or secondary adaptive effects by the central nervous system. Tests to confirm the diagnosis include edrophonium challenge, repetitive nerve stimulation, single-fiber electromyography (EMG) of the frontalis, and assays for antibody directed against the acetylcholine receptor: all are less sensitive for ocular myasthenia than for generalized myasthenia. There is a higher incidence of other autoimmune conditions in myasthenia, notably thymoma and thyroid dysfunction. The differential diagnosis includes other diseases of the neuromuscular junction, such as Lambert-Eaton syndrome and botulism. Treatment consists of symptomatic use of acetylcholinesterase inhibitors and immunosuppression with steroids or azathioprine. Between 50 and 70% of patients with ocular myasthenia will eventually develop generalized disease: there is some retrospective data that steroids or azathioprine may reduce this by about 75%. The role of thymectomy in ocular myasthenia remains unclear.

Humans↗

PubMed1999

Intrapartum antibiotic prophylaxis increases the incidence of gram-negative neonatal sepsis.

OBJECTIVE: To investigate the influence of the increased use of intrapartum chemoprophylaxis on the incidence of vertically transmitted neonatal sepsis. METHODS: Multiple institutional databases were queried for the number of cases in which intrapartum antibiotics were used, the obstetric risk factors that were present, and the number of resultant cases of neonatal sepsis that occurred for deliveries from 1992 through 1997. Intrapartum antibiotic use was compared between the first and fourth quarter of 1997. Comparisons were made between the years 1992-1996 and 1997 for the incidence of the various pathogens causing neonatal sepsis; group B streptococcus (GBS), gram-negative sepsis, and others. RESULTS: We found a significant increase in intrapartum chemoprophylaxis between the first and fourth quarters of 1997 corresponding to the increased physician awareness of published guidelines. As expected, the incidence of neonatal GBS sepsis was drastically reduced (from 1.7/1000 live births to 0 in 3730 births, P = 0.02). Unfortunately, there was a concomitant increase in the incidence of gram-negative sepsis (0.29/1000 vs. 1.3/1000, P = .02). The overall incidence of neonatal sepsis remained unchanged (2.7/1000 vs. 2.1/1000, P = .69). CONCLUSIONS: Published guidelines have encouraged physicians to increase the use of intrapartum chemoprophylaxis to reduce vertical transmission of GBS. This study confirms the efficacy of this approach. Unfortunately, this reduction comes at the cost of increasing the incidence of ampicillin-resistant gram-negative neonatal sepsis with a resultant increased mortality. These data provide compelling evidence that the policy of providing ampicillin chemoprophylaxis in selected patients needs to be reconsidered.

Ampicillin↗

PubMed1999

Spatial representation in the normal visual field: a study of hemifield line bisection.

We examined bisection of lines viewed in only one hemifield by normal subjects. Subjects first performed a traditional version of line bisection, by indicating the perceived midpoint of a line on paper with a penmark. Bisection was accurate when they were allowed to shift their gaze over the stimulus, but it was biased towards the central visual field (centripetally) when gaze was fixed so that the line was seen in only one hemifield. In a second experiment, lines with transectors at various locations were presented briefly on a screen and subjects had to indicate on which side of the perceived midpoint the transector was located. A centripetal bias was still found, indicating that it has a perceptual origin. The interaction between bias and effects of tangent line presentation suggested that subjects were performing an angle bisection rather than a line bisection. Also, there was bias in not only right and left hemifields but also upper and lower hemifields. In a third experiment, increasing the width of the stimulus bars peripherally did not eliminate this bias. Bias was size-invariant along the horizontal meridian. This spatial version of Weber's law was modeled by a magnification function using an exponential equation. The slope of this function is much shallower than those currently known for V1, V4 and V5. We conclude that a centripetal bias exists for hemifield line bisection and that this bias likely contributes to the contralateral bias of line bisection by hemianopic patients found in other studies.

Adolescent↗

PubMed1999

Pediatrician attendance at cesarean delivery: necessary or not?

OBJECTIVE: To determine whether it is necessary for a pediatrician to attend all cesarean deliveries. METHODS: We analyzed a database of 17,867 consecutive deliveries to determine the rates of low Apgar scores in the following three groups of patients: those with vaginal delivery, cesarean delivery using regional anesthesia without fetal indication, and cesarean delivery for fetal indications or using general anesthesia. RESULTS: There was a significantly higher rate of low Apgar scores in the fetal indications or general anesthesia group when compared with vaginal deliveries. Specifically, 35 (5.8%) of 596 cesareans for fetal heart rate abnormality or using general anesthesia had 1-minute Apgars under 4 in contrast to 115 of 10,270 (1.1%) of vaginal deliveries. There was no significantly increased risk for low Apgar scores in the group of cesareans using regional anesthesia for nonfetal indications (33 of 2057, 1.6%). Results were similar for Apgar scores under 7 at 5 minutes. CONCLUSION: Because there is no higher incidence of low Apgar scores in cesarean deliveries using regional anesthesia for nonfetal indications compared with vaginal deliveries, there is no convincing need for pediatrician attendance at such deliveries.

Apgar Score↗

PubMed1999

Acquired convergence-evoked pendular nystagmus in multiple sclerosis.

Nystagmus seen only with convergence is unusual. We describe four cases of acquired convergence-evoked pendular nystagmus in patients with multiple sclerosis. The nystagmus was horizontal and asymmetric in all patients. Eye movement recordings in one subject showed a conjugate rather than a convergent-divergent relationship of the phase of movement between the two eyes. All patients had evidence of optic neuropathy and cerebellar dysfunction. Occlusion of either eye during fixation of near targets led to divergent drift of the covered eye and a decrease in nystagmus. Intravenous scopolamine reduced nystagmus in one patient. Base-in prisms alleviated symptoms of oscillopsia at near and improving reading visual acuity. Convergence-evoked pendular nystagmus may be more common than currently appreciated, particularly among patients with multiple sclerosis.

Adult↗

PubMed1998

Quantitative ocular tests for myasthenia gravis: a comparative review with detection theory analysis.

Many reports in the literature describe a variety of ocular signs in myasthenia gravis. To determine the utility of laboratory recordings of ocular signs in the evaluation for myasthenia, we reviewed all previous studies of quantitative measures of eye movements or intra-ocular pressures. We selected those studies with data presented for both myasthenic and non-myasthenic ocular palsies. Signal detection theory was used to evaluate the discriminative power of each variable. The characteristics of saccades and quick phases of optokinetic nystagmus at the start of recording were poor at distinguishing between myasthenic and non-myasthenic palsies, except when the comparison was solely between myasthenia and chronic progressive external ophthalmoplegia. The effects of fatigue on saccadic parameters were also not discriminative, though there was insufficient data to evaluate this adequately. Changes induced by edrophonium in the amplitude or peak velocity of saccades or optokinetic quick phases were good diagnostic tests, retaining high sensitivities when criteria were set to yield a specificity of 95%. Most of these parameters were less efficient as screening tests, with modest specificities when criteria were set to yield a sensitivity of 95%. The change in optokinetic quick phase amplitude recorded by infrared oculography was the best test, with ideal characteristics of 97% specificity and sensitivity at a criterion of zero change. This analysis suggests that eye movement recordings of saccades or optokinetic nystagmus have potential as useful and inexpensive tests for myasthenia, and warrant further study.

Edrophonium↗

PubMed1998

Intrapartum management relating to the risk of perinatal transmission of group B streptococcus.

OBJECTIVE: To review the incidence of neonatal group B streptococcal (GBS) sepsis and its associated risk factors in our obstetrical population. METHODS: A computerized perinatal database of over 17,000 births (from 1992 to 1996) was queried for the incidence of neonatal GBS sepsis. A more detailed review of 895 births (from the first quarter of 1997) was undertaken to identify the incidence of risk factors known to be associated with neonatal GBS sepsis. RESULTS: In our institution, 30 cases of neonatal early-onset GBS sepsis were identified in over 17,000 births (or 1.7/1,000 deliveries). Risk factors were identified in 17 of those cases (56%). There were two neonatal fatalities. Chemoprophylaxis was provided in 15% of the total deliveries. CONCLUSIONS: In spite of the lack of a uniform policy for identifying patients suitable for GBS chemoprophylaxis, we found only a 43% incidence of neonatal GBS sepsis occurring without risk factors present. Identification of antepartum or intrapartum risk factors in our series, therefore, would have identified the majority of cases resulting in neonatal GBS sepsis, which may have benefited from intrapartum therapy. Some negative potential consequences of chemoprophylaxis are discussed, raising questions regarding the recent recommendations of the Centers for Disease Control and Prevention.

Ampicillin↗

PubMed1998

Small retinal hemorrhages as the only sign of an intracranial aneurysm.

PURPOSE: To report a woman with two small circumpapillary and nerve fiber layer hemorrhages found on routine examination. METHODS: Case report. The patient had a history of severe headache 2 weeks previously but no other symptoms or signs. RESULT: Magnetic resonance imaging showed an intracranial aneurysm. CONCLUSIONS: This potentially lethal abnormality should be considered with small unexplained retinal hemorrhages, even when the neurologic examination is normal. A history of recent headache should be sought.

Adult↗

PubMed1998

Ocular search during line bisection. The effects of hemi-neglect and hemianopia.

We examined ocular fixations during line bisection in five patients with left hemianopia, two patients with right hemianopia, nine patients with left hemi-neglect and nine normal control subjects. Compared with measures in control subjects, the median fixation, and left- and rightmost fixations were shifted contralaterally in patients with hemianopia alone and ipsilaterally in patients with hemi-neglect. The fixation with the longest duration and the bisection point were also shifted contralaterally with hemianopia and ipsilaterally with hemi-neglect. However, the number of fixations and the spatial range spanned by fixations did not differ between the groups, showing that ocular exploration was not truncated in any group. Only some patients showed a previously reported directional search bias. Overall, there was no directional bias in saccadic number or amplitude. The distribution of fixations was most dense at the centre of the line in normal subjects, while hemianopic patients fixated most frequently at the ends of lines in their contralateral (blind) hemispace and at a central locus that was biased slightly contralaterally, as was their bisection judgement. This contralateral bias may reflect either an adaptive contralateral attentional gradient or a non-veridical spatial representation within the remaining normal hemifield. Hemi-neglect patients had a broad distribution of fixation peaks in the ipsilateral hemispace. Of two hemi-neglect patients with many fixations, one clustered fixations at a position right of centre, as if a normal fixation pattern was shifted rightward, while the other had two fixation peaks: one to the far right and the other near the centre of the line, reminiscent of the dual peaks of activity seen in some recent hemi-neglect models. These data reveal a heterogeneity in the routes by which right-biased judgements of spatial centre are reached by hemi-neglect patients.

Adult↗

PubMed1998

Ocular tracking of step-ramp targets by patients with unilateral cerebral lesions.

The relationship of sinusoidal smooth pursuit defects to pursuit defects with step-ramp targets in patients with cerebral lesions is unclear. We examined pursuit and saccades to both step-ramp and sinusoidal targets in 17 patients with unilateral cerebral lesions. Two types of pursuit defects were found. One group of three patients had ipsi-directional sinusoidal pursuit defects from lesions to the posterior internal capsule. Their chief abnormality with step-ramp targets was increased contra-directional pursuit. Their ipsi-directional step-ramp pursuit was often normal and disproportionately better than their ipsi-directional sinusoidal pursuit. Another patient with a parietal lesion had a second type of pursuit defect. He had low-normal sinusoidal pursuit bilaterally, but decreased ipsi- and contra-directional step-ramp pursuit. Also, he had an abnormal contra-directional drift after saccades to stationary targets. Despite these pursuit defects, saccadic accuracy did not show poor compensation for target motion in either patient type. The patient with the parietal lesion also had increased latencies for contralateral saccades. Recovery of pursuit was studied in one patient with an infarct of the posterior internal capsule. Initially he had a contra-directional bias that caused decreased ipsi-directional pursuit, increased contra-directional pursuit, and a contra-directional drift after saccades to stationary targets. Four months later, ipsi-directional pursuit and the post-saccadic drift to stationary targets had recovered, but contra-directional pursuit remained abnormally high. We conclude that lesions of descending pursuit tracts in the internal capsule are characterized by a contra-directional bias which recovers partly through a direction-specific adaptation. Lesions that affect the human homologue of posterior parietal cortex cause asymmetric bi-directional defects in pursuit initiation and increased contralateral saccadic latencies.

Adult↗

PubMed1998

Higher cortical visual function.

Higher cortical visual function continues to be explored with both lesion and functional imaging studies. Studies with functional MRI confirm that the fusiform gyri are involved in color and face perception, and show multiple regions participating in motion perception, including V5, V3A, and a new area, the kinetic occipital region. There were numerous blindsight reports, including studies of spatial summation and "inhibition of return," and a refutation of the argument that blindsight is merely a "criterion shift." However, other studies failed to find blindsight-like ocular motor responses to moving stimuli. Occipitotemporal lesions were found to cause defects in perception of both first- and second-order motion. The psychophysical impairments of the motion-blind patient LM were shown to be similar to those of monkeys with V5 ablations, suggesting a close homology between this monkey visual area and the human motion area in the lateral occipitotemporal cortex.

Animals↗