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D W Loring

Publications and source records attributed to D W Loring.

At least 19 recordsLinked to original sources
PubMed2001

Differential cognitive and behavioral effects of carbamazepine and lamotrigine.

BACKGROUND: The relative cognitive and behavioral effects of lamotrigine compared with the older standard antiepileptic drugs (AED) are uncertain. OBJECTIVE: To directly compare the cognitive and behavioral effects of carbamazepine and lamotrigine. METHODS: The cognitive and behavioral effects of carbamazepine and lamotrigine were assessed in 25 healthy adults using a double-blind, randomized crossover design with two 10-week treatment periods. During each treatment condition, subjects received either lamotrigine (150 mg/day) or carbamazepine (mean 696 mg/day) adjusted to a dose to achieve midrange standard therapeutic blood levels (mean 7.6 microg/mL). Subjects were tested at the end of each AED treatment period and in three drug-free conditions (two pretreatment baselines and a final posttreatment period [1 month after last AED]). The neuropsychological test battery included 19 measures yielding 40 total variables. RESULTS: Direct comparison of the two AED revealed significantly better performance on 19 (48%) variables for lamotrigine but none for carbamazepine. Differences spanned both objective cognitive and subjective behavioral measures, including cognitive speed, memory, graphomotor coding, neurotoxic symptoms, mood factors, sedation, perception of cognitive performance, and other quality-of-life perceptions. Comparison of carbamazepine with the nondrug average revealed significantly better performance for nondrug average on 24 (62%) variables but none for carbamazepine. Comparison of lamotrigine with nondrug average revealed better performance on one (2.5%) variable for nondrug average and on one (2.5%) variable for lamotrigine. CONCLUSION: Lamotrigine produces significantly fewer untoward cognitive and behavioral effects than carbamazepine at the dosages used in this study.

Adult↗
PubMed2001

Relationship of extinction to perceptual thresholds for single stimuli.

OBJECTIVE: To demonstrate the effects of target stimulus intensity on extinction to double simultaneous stimuli. BACKGROUND: Attentional deficits contribute to extinction in patients with brain lesions, but extinction (i.e., masking) can also be produced in healthy subjects. The relationship of extinction to perceptual thresholds for single stimuli remains uncertain. METHODS: Brief electrical pulses were applied simultaneously to the left and right index fingers of 16 healthy volunteers (8 young and 8 elderly adults) and 4 patients with right brain stroke (RBS). The stimulus to be perceived (i.e., target stimulus) was given at the lowest perceptual threshold to perceive any single stimulus (i.e., Minimal) and at the threshold to perceive 100% of single stimuli. The mask stimulus (i.e., stimulus given to block the target) was applied to the contralateral hand at intensities just below discomfort. RESULTS: Extinction was less for target stimuli at 100% than Minimal threshold for healthy subjects. Extinction of left targets was greater in patients with RBS than elderly control subjects. Left targets were extinguished less than right in healthy subjects. In contrast, the majority of left targets were extinguished in patients with RBS even when right mask intensity was reduced below right 100% threshold for single stimuli. RBS patients had less extinction for right targets despite having greater left mask - threshold difference than control subjects. In patients with RBS, right "targets" at 100% threshold extinguished left "masks" (20%) almost as frequently as left masks extinguished right targets (32%). CONCLUSIONS: Subtle changes in target intensity affect extinction in healthy adults. Asymmetries in mask and target intensities (relative to single-stimulus perceptual thresholds) affect extinction in RBS patients less for left targets but more for right targets as compared with control subjects.

Adult↗
PubMed2001

WMS-III performance in patients with temporal lobe epilepsy: group differences and individual classification.

The utility of the WMS-III in detecting lateralized impairment was examined in a large sample of patients with temporal lobe epilepsy. Methods of analysis included evaluation of group means on the various indexes and subtest scores, the use of ROC curves, and an examination of Auditory-Visual Index discrepancy scores. In addition, performance on immediate and delayed indexes in the auditory and the visual modality was compared within each group. Of the WMS-III scores, the Auditory-Visual Delayed Index difference score appeared most sensitive to side of temporal dysfunction, although patient classification rates were not within an acceptable range to have clinical utility. The ability to predict laterality based on statistically significant index score differences was particularly weak for those with left temporal dysfunction. The use of unusually large discrepancies led to improved prediction, however, the rarity of such scores in this population limits their usefulness. Although the utility of the WMS-III in detecting laterality may be limited in preoperative cases, the WMS-III may still hold considerable promise as a measure of memory in documenting baseline performance and in detecting those that may be at risk following surgery.

Adult↗
PubMed2000

Anosognosia and asomatognosia during intracarotid amobarbital inactivation.

BACKGROUND: Anosognosia (i.e., denial of hemiparesis) and asomatognosia (i.e., inability to recognize the affected limb as one's own) occur more frequently with right cerebral lesions. However, the incidence, relative recovery, and underlying mechanisms remain unclear. METHODS: Anosognosia and asomatognosia were examined in 62 patients undergoing the intracarotid amobarbital procedure as part of their preoperative evaluation for epilepsy surgery. Additional questions were asked in the last 32 patients studied. RESULTS: During inactivation of the non-language-dominant cerebral hemisphere, 88% of the 62 patients were unaware of their paralysis, and 82% could not recognize their own hand at some point. Only 3% did not exhibit anosognosia or asomatognosia. In general, asomatognosia resolved earlier than anosognosia. When patients could not recognize their hand, they uniformly thought that it was someone else's hand. Dissociations in awareness were seen in the second series of 32 patients. Although 23 patients (72%) thought that both arms were in the air, 31% pointed to the correct position of the paralyzed arm on the table. Despite the inability of 24 of 32 patients (75%) to recognize their own hand, 21% of these patients were aware that their arm was weak, and 38% had correctly located their paralyzed arm on the angiography table. CONCLUSIONS: Anosognosia and asomatognosia are both common during acute dysfunction of the non-language-dominant cerebral hemisphere. Dissociations of perception of location, weakness, and ownership of the affected limb are frequent, as are misperceptions of location and body part identity. The dissociations suggest that multiple mechanisms are involved.

Adolescent↗
PubMed2000

Hemispheric asymmetries of limb-kinetic apraxia: a loss of deftness.

OBJECTIVES: Unlike patients with ideomotor apraxia who make temporal and spatial errors and patients with ideational or conceptual apraxia who make content errors, patients with limb-kinetic apraxia have loss of deftness, including fine and precise movements, independent finger movements, and difficulty coordinating simultaneous movements. This study was conducted to learn the relationship between limb-kinetic apraxia and hemisphere dysfunction by using selective hemisphere anesthesia, the Wada test. METHODS: Subjects were 90 patients undergoing Wada testing for intractable epilepsy. They were divided into typical (right-handed with left hemisphere language dominance) and atypical (nonright-handed, or without left hemisphere language dominance). Before and during Wada testing, subjects were shown line drawings of tools, four for each hand tested. After being shown each picture, subjects pantomimed the use of this tool. A behavioral neurologist and neuropsychologist scored the pantomimes for the presence of limb-kinetic errors. RESULTS: For the typical group, during left hemisphere anesthesia, the limb-kinetic errors made by the right and left hands did not differ, but during right hemisphere anesthesia the left hand made more errors than the right. Unlike the typical subjects, when the left hemisphere was anesthetized, the atypical subjects made more errors with their right hands than left. However, similar to the typical subjects with right hemisphere anesthesia, the atypical subjects made more left- than right-hand limb-kinetic errors. CONCLUSIONS: For people with typical brain organization, the left hemisphere mediates motor deftness for both hands, but the right hemisphere primarily controls deftness for the left hand. For people with atypical brain organization, each hemisphere primarily controls deftness for the contralateral hand.

Adult↗
PubMed2000

Relationship between motor and language activation using fMRI.

The authors examined laterality ratios (i.e., [L-R]/[L+R]) from functional MRI (fMRI) scans obtained in 12 healthy volunteers during unimanual left- and right-hand finger movements and during a verb generation language task. The language and right-hand motor asymmetry ratios were correlated (rho = 0.71, p = 0.005) as were the left- and right-hand ratios (rho = -0.68, p = 0.008). Subjects with greater relative left hemisphere lateralization of language exhibit greater relative unilateral hemisphere activation during right-hand movements.

Adult↗
PubMed2000

Functional MRI cerebral activation and deactivation during finger movement.

OBJECTIVE: To examine interhemispheric interactions of motor processes by using functional MRI (fMRI). BACKGROUND: Despite evidence of interhemispheric inhibition from animal, clinical, and transcranial magnetic stimulation (TMS) studies, fMRI has not been used to explore activation and deactivation during unilateral motor tasks. fMRI changes associated with motor activity have traditionally been described by comparing cerebral activation during motor tasks relative to a "resting state." In addition to this standard comparison, we examined fMRI changes in the resting state relative to a motor task. METHODS: Thirteen healthy volunteers performed self-paced sequential finger/thumb tapping for each hand. During fMRI data acquisition, four epochs were obtained; each comprised of 30 seconds of rest, 30 seconds of right hand activity, and 30 seconds of left hand activity. Resultant echoplanar images were spatially normalized and spatially and temporally smoothed. RESULTS: As expected, hand movements produced activation in the contralateral sensorimotor cortex and adjacent subcortical regions and, when present, the ipsilateral cerebellum. However, hand movement also produced a significant deactivation (i.e., decreased blood flow) in the ipsilateral sensorimotor cortex and subcortical regions, and when present, the contralateral cerebellum. Conjunction analysis demonstrated regions that are activated by one hand and deactivated by the contralateral hand. CONCLUSION: Unilateral hand movements are associated with contralateral cerebral activation and ipsilateral cerebral deactivation, which we hypothesize result from transcallosal inhibition.

Adult↗
PubMed2000

The Memory Assessment Scales and lateralized temporal lobe epilepsy.

We report Memory Assessment Scales (MAS) performance in 101 patients with unilateral temporal lobe epilepsy (TLE; left, n = 51; right, n = 50) with left cerebral language dominance. A significant multivariate group effect was present for the major summary indices (Verbal Memory, Visual Memory, and Global Memory, p < .04). Univariate analyses revealed no significant differences for either the Global Memory or Verbal Memory summary scores, although a significant group difference was present for Visual Memory (p < .04). The Verbal Memory-Visual Memory discrepancy score was significantly different between right and left TLE groups (p < .004). Verbal Memory scores were at least 14 points lower than Visual Memory scores in 34 patients (left = 20, 59%; right = 14, 41%). Visual Memory scores were at least 14 points lower than Verbal Memory performance in 20 patients (left = 5, 25%; right = 15, 75%). Diagnostic efficiency statistics show higher sensitivity but lower specificity in group classification for left TLE patients. These data suggest that the MAS is sensitive to material-specific memory deficits associated with a unilateral temporal lobe seizure focus. However, over one-third of the patients (19/54) with at least a 14-point Verbal Memory-Visual Memory discrepancy were classified incorrectly. The MAS, like other material-specific memory measures, should be interpreted within the context of other clinical findings.

Adult↗
PubMed2000

Limb and hemispatial hypometria.

In a previous study, we demonstrated that unilateral cerebral lesions produce hypometric limb movements of the contralateral arm and hemispatial (i.e., directional) hypometria for movements towards contralateral hemispace. In the present study, we investigated 10 patients with right cerebral lesions and 25 healthy controls using a task to uncouple deficits in sensory perceptual systems and motor-action output systems on directional hypometria. This task required participants, with their eyes closed, to reproduce lateral and medial horizontal displacements (15-27 cm) with each arm. Each participant was seated at a waist high table and had their hand placed at an origin point aligned with the axillary fold on the same side. Their hand was moved by the investigator from the origin point to a target point and brought back to the point of origin (input displacement). The participant was then asked to return their hand to either the same target point or to an equidistant target point in the opposite direction. Healthy dextral participants were significantly more hypometric with their right arm, but patients with right cerebral lesions exhibited an opposite pattern with overall left arm hypometria. In addition, patients were significantly more hypometric for movements when output displacements were toward left hemispace. No effect was found for direction of sensory input. The results suggest that the directional hypometria is predominantly produced by hemispatial output deficits.

Adolescent↗
PubMed2000

Train duration effects on perception: sensory deficit, neglect, and cerebral lateralization.

The mechanisms of conscious perception are uncertain. In a preliminary study, dramatic effects of train duration on perception in a patient with right brain stroke were noted. In this study, the mechanisms of train duration on perception of peripheral somatosensory stimuli are examined. Subjects included healthy adults and patients with right brain infarctions. Train duration effects on perception were examined in relation to cerebral infarction, handedness, age, elevated peripheral threshold via bupivacaine, and impaired attention via diazepam or scopolamine. Perceptual thresholds to electrical pulses on the hand decreased as train duration increased, but only over the first several hundred milliseconds. Compared to controls, right brain stroke patients showed much greater lowering of threshold in the affected hand as train duration was extended. Age and bupivacaine elevated thresholds, but had little or no influence on train duration effects. Diazepam and scopolamine had no effect on thresholds. Thresholds were lower in the left than right hand of healthy dextral subjects, irrespective of age. Sinistral subjects had less left/right asymmetry. Increased train duration effect in patients is not explained by a primary elevation in threshold or by impaired vigilance. Lower perceptual thresholds in the left hand of healthy dextral subjects is consistent with right cerebral dominance for externally directed attention.

Adjuvants, Anesthesia↗
PubMed2000

Prognostic implication of contralateral secondary electrographic seizures in temporal lobe epilepsy.

PURPOSE: Interhemispheric propagation of seizures in temporal lobe epilepsy is frequently noted during intracranial EEG monitoring. We hypothesized that a distinct secondary electrographic seizure (DSES) in the temporal lobe contralateral to primary seizure onset may be an unfavorable prognostic indicator. METHODS: We reviewed intracranial depth electrode EEG recordings, 1-year outcome, and medical records of 51 patients (M 29, F 22: age 15-64 years) who underwent anterior temporal lobectomy during 1988-96. We defined DSES as a seizure that spread to the contralateral temporal lobe and produced distinct contralateral EEG features. The distinct feature was focal involvement of one or two electrode contacts at onset, which starts and evolves independently from the ipsilateral temporal lobe. We considered DSES as the predominant seizure pattern when it occurred in more than one half of the patients' recorded seizures. RESULTS: Only nine of 19 (47%) patients with predominant DSES had a 1-year seizure-free outcome, whereas 27 of 32 (84%) patients without predominant DSES had a 1-year seizure-free outcome (p < 0.01). Bitemporal independent seizures were more common in patients with predominant DSES (9/19 versus 0/32; p < 0.001). CONCLUSION: Our results suggest that distinct contralateral secondary electrographic seizure is a predictor of unfavorable outcome and is also more likely to be associated with bitemporal seizures.

Adolescent↗
PubMed2000

Temporal lobectomy in children: cognitive outcome.

OBJECT: The authors sought to determine the impact of early temporal lobectomy (in patients younger than age 17 years) on intellectual functioning. The efficacy of temporal lobectomy for treating seizures is well established and the procedure is becoming more acceptable as a treatment for children whose seizures are intractable. However, cognitive outcomes of temporal lobectomy in children and adolescents are largely unreported. The present study takes advantage of a unique multicenter collaboration to examine retrospectively intellectual functioning in a large sample of children who underwent temporal lobectomy. METHODS: Intellectual functioning was assessed before and after temporal lobectomy for treatment of medication-resistant seizures in 82 patients at eight centers of epilepsy surgery. All children underwent standard presurgical examinations, including electroencephalography-video monitoring, magnetic resonance (MR) imaging, and neuropsychological testing, at their respective centers. Forty-three children underwent left temporal lobectomy and 39 underwent right temporal lobectomy. For the entire sample, there were no significant declines in intelligence quotient (IQ) following surgery. Children who underwent left temporal lobectomy demonstrated no significant loss in verbal intellectual functioning and improved significantly in nonverbal intellectual functioning. Children who underwent right temporal lobectomy did not demonstrate significant changes in intellectual functioning. Although group scores showed no change in overall IQ values, an analysis of individual changes revealed that approximately 10% of the sample experienced a significant decline and 9% experienced significant improvement in verbal functioning. Significant improvement in nonverbal cognitive function was observed in 16% of the sample and only 2% of the sample showed significant declines. Risk factors for significant decline included older patient age at the time of surgery and the presence of a structural lesion other than mesial temporal sclerosis on MR imaging. CONCLUSIONS: The present study provides preliminary data for establishing the risk of cognitive morbidity posed by temporal lobectomy performed during childhood. With respect to global intellectual functioning, a slight improvement was significantly more likely to occur than a decline. However, there were several patients in whom significant declines did occur. It will be necessary to study further the factors associated with such declines. In addition, further study of more specific cognitive functions, particularly memory, is needed.

Adolescent↗
PubMed2000

Pre-surgical evaluation for epilepsy surgery.

Neuropsychological testing may reflect subtle structural changes that may not be readily apparent with neuroimaging studies, and physiologic disruption of normal neural function secondary to epileptic activity. Neuropsychological testing is used during the pre-operative evaluation for epilepsy surgery to assess functional brain status, which, in turn, provides important information on the risks for post-operative neuropsychological deficits and also provides confirmatory evidence of seizure onset laterality in patients whose seizures originate in temporal lobes. This review will focus primarily on the pre-operative neuropsychological of candidates for temporal lobectomy surgery since they represent the majority of individuals undergoing ablative epilepsy surgery, and also because the literature and knowledge for the neuropsychology of temporal lobectomy far exceeds that of any other epilepsy surgical group.

Anterior Temporal Lobectomy↗
PubMed1999

Cerebral lateralization: relationship of language and ideomotor praxis.

OBJECTIVE: To determine the relationship of language lateralization and hand preference to praxis performance following left and right hemispheric amobarbital-induced inactivations. BACKGROUND: Patients who are aphasic from left cerebral dysfunction also frequently exhibit ideomotor apraxia in which they make temporal, spatial, and postural errors of learned skilled movements. However, hemispheric lateralization of the systems mediating ideomotor praxis in patients with atypical cerebral language dominance (i.e., bilateral or right hemispheric language function) remains uncertain. METHODS: Subjects included 90 patients with intractable seizures who were undergoing the intracarotid amobarbital procedure (IAP) as part of their preoperative evaluation for epilepsy surgery. Hand preference was determined by the Benton Handedness Questionnaire. Praxis was assessed by the subject's performance when pantomiming the use of four pictured tools. RESULTS: During left IAP, patients with typical language dominance made more ideomotor apraxic errors than did patients with atypical language dominance. During right IAP, patients with atypical language dominance made more ideomotor apraxic errors than did patients with typical language dominance. Overall, patients with atypical language dominance made fewer ideomotor apraxic errors than did patients with typical language dominance. These relationships were present irrespective of hand preference. CONCLUSIONS: Language dominance is more closely associated with the laterality of temporal and spatial movement representations (i.e., ideomotor praxis dominance) than is hand preference. Patients with atypical language dominance exhibit more bilateral cerebral distribution of both language and praxis function.

Adult↗
PubMed1999

Effects of anomalous language representation on neuropsychological performance in temporal lobe epilepsy.

OBJECTIVE: To examine the effects of anomalous language representation (i.e., mixed- and right-cerebral dominant) on neuropsychological performance. BACKGROUND: Right cerebral language dominance resulting from early cerebral injury is associated with relatively preserved language function with decreased visuospatial ability. However, previous reports of this phenomenon have examined patients with relatively large cerebral injuries (e.g., infantile hemiplegia) or limited sample sizes. METHODS: A total of 561 patients with complex partial seizures of left temporal lobe origin were studied. Patients were classified into left (n = 455), bilateral (n = 58), and right (n = 48) language dominant groups based on Wada testing. RESULTS: Right language dominant patients performed more poorly on multiple tests of visuospatial function, including Performance IQ (PIQ), than did left language patients. No significant group differences were detected for measures of language or general verbal function. The effects of bilateral language on PIQ differed according to handedness. Lowered PIQ was present in the bilateral nondextral group but not for bilateral dextral patients, and this pattern was observed with other visuospatial measures. CONCLUSIONS: In patients with relatively small lesions restricted to the left mesial temporal lobe, a shift in language dominance to the right hemisphere is associated with decreased visuospatial functions but preserved verbal abilities. Nondextral patients with bilateral language representation also displayed decreased visuospatial performance, although dextral patients with bilateral language did not.

Adult↗
PubMed1999

Differential immunologic effects of language-dominant and nondominant cerebral resections.

OBJECTIVE: To demonstrate whether the cerebral hemispheres (language dominant versus nondominant) affect immune function differentially in humans by delineating the effects of resections for epilepsy surgery on T-cell indices. BACKGROUND: Cerebral lateralization has been postulated to affect immunomodulation. Differential effects of left versus right cerebral lesions on T-cell numbers and responsiveness have been demonstrated in animals, but the effects in humans are unclear. METHODS: Pre- and postoperative changes in T-cell indices were examined in relation to side of language dominance in patients undergoing epilepsy surgery. RESULTS: Absolute lymphocyte count, total T cells (CD3+), helper T cells (CD3+4+), cytotoxic/suppressor cells (CD3+8+), and total suppressor cells (CD8+) were reduced after language-dominant resections, but were increased after nondominant resections. CONCLUSIONS: Although the mechanisms are not fully elucidated, the results demonstrate differential immunologic responses in humans to focal cerebral lesions as a function of cerebral lateralization.

Adult↗