Anosognosia and the intracarotid amobarbital procedure (Wada test).
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Agnosia↗
Biomedical subjects
D W Loring
Publications and source records attributed to D W Loring.
Effects of temporal lobectomy on generative fluency and other language functions.
We investigated the acute effects of unilateral temporal lobectomy on multiple language measures and standardized generative word fluency tasks, as well as longer term effects measured 1 year following surgery. All patients were left cerebral dominant for language functioning as determined by Wada testing. Results indicate consistent acute language decline for left but not right temporal lobectomy patients. In contrast, verbal generative fluency decreased independent of lesion laterality, suggesting diffuse acute lesion effects on certain tasks mediated primarily by the left hemisphere. When examining language performance in an independent patient group at their 1-year follow-up assessment, no negative surgery effects were present on any language measure. Further, significant improvement over baseline performance for word fluency was present 1 year following surgery. In the acute assessment of cognition following temporal lobectomy, the relative sensitivity of neuropsychological measures to acute cerebral lesions should be considered.
Journal Article↗
Evidence for a central cholinergic effect of high-dose thiamine.
In vitro animal studies have suggested that thiamine is involved in the presynaptic release of acetylcholine. Total thiamine content in cholinergic nerve terminals is comparable with that of acetylcholine, and the phosphorylation state of thiamine changes with release of acetylcholine. Thiamine binds to nicotinic receptors and may exhibit anticholinesterase activity. Based on these observations, we investigated the effects of pharmacological doses of thiamine on the cognitive deficits induced by the anticholinergic scopolamine in healthy young adults using a randomized, double-blind, placebo-controlled, double-crossover design. Drug effects were assessed by P3 event-related potential, quantitated electroencephalography, and free recall memory. Conditions included (1) baseline, (2) thiamine 5 gm p.o. and scopolamine 0.007 mg/kg IM, and (3) lactose PO and scopolamine 0.007 mg/kg IM. Thiamine significantly reduced adverse effects of scopolamine on P3 latency, spectral components of electroencephalography, and memory recall. The results are consistent with a cholinomimetic effect of thiamine in the central nervous system. Additional studies are needed to delineate the basic mechanisms and possible therapeutic efficacy of thiamine at pharmacological dosages.
Adult↗
The role of cholinergic systems in visuospatial processing and memory.
Few studies have specifically addressed the cholinergic role in visuospatial memory. In the present study, we employed a randomized double-blind repeated measures design to investigate the effects of scopolamine on Judgement of Line Orientation (JLO) and two distinct visuospatial memory tasks. Complex Figures (CF) is a test of drawn reproduction similar to the Rey complex figure. The Spatial Array Memory Test (SAMT) is a two-dimensional free-recall visuospatial test which minimizes constructive skills and allows sensitive measurement of placement errors. Scopolamine impaired performance on JLO and CF. However, no effects of scopolamine on SAMT were apparent even though the SAMT is sensitive to aging and right temporal-lobe lesions. Selective effects of scopolamine on focused versus distributed attention may account for these differential results.
Adult↗
Seizure localization in temporal lobe epilepsy: a comparison of scalp-sphenoidal EEG and volumetric MRI.
We determined the accuracy of volumetric MRI (based on identification of unilateral hippocampal atrophy) and scalp-sphenoidal EEG (based on concordant interpretations of scalp-sphenoidal ictal EEG by three independent interpreters) for seizure focus localization in 20 patients with temporal lobe epilepsy. All patients became seizure-free or had rare seizures following temporal lobectomy. Among the 20 patients, nine (45%) met both MRI and EEG localization criteria, six (30%) met MRI localization criteria alone, three (15%) met EEG localization criteria alone, and two patients (10%) did not meet either localization criteria. In the 18 patients meeting MRI or EEG localization criteria, the predicted localization agreed with the side of temporal lobectomy. These results suggest that a noninvasive approach combining MRI and EEG will correctly localize the side of seizure onset in most patients with temporal lobe epilepsy.
Adolescent↗
Wada memory testing and hippocampal volume measurements in the evaluation for temporal lobectomy.
We examined the relationship of Wada memory performance and MRI hippocampal volume measurements to laterality of ultimate seizure localization in 20 patients with complex partial seizures who later underwent temporal lobectomy. Discriminant function analysis employing both Wada memory test asymmetries and hippocampal volume asymmetries correctly classified 100% of the patients into left and right temporal lobe groups. Wada memory asymmetries alone correctly classified 90% of the sample (80% of the sample when the discriminant function included all patients except the one being classified), and hippocampal volume asymmetries alone correctly classified 90% of the patients. A significant correlation was present between Wada memory asymmetries and hippocampal volume asymmetries (r = 0.78), indicating that structural evidence of reduced hippocampal volume has a functional correlate reflected by Wada memory performance. These data suggest that the combination of functional and structural measures is of value in the preoperative evaluation for epilepsy surgery.
Adult↗
Anticonvulsant withdrawal.
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Anticonvulsants↗
Influence of premorbid personality and location of lesion on emotional expression.
Both premorbid personality characteristics and location of brain lesion have been proposed to account for emotional changes after cerebral damage. To explore the relative merits of each hypothesis, we compared the MMPI profiles of 30 epileptic patients, who showed either a euphoric or depressive reaction after injection of amobarbital into the right or left hemisphere, with the MMPI profiles of 30 matched controls. There were no significant T-score differences between euphoric, depressed, or control patients on any of the MMPI scales. However, more patients with euphoric (42%) than depressed (0%) reactions had hypomania (scale 9) scores greater than 70 T. With regard to location of lesion, there was a statistically significant association between emotional reaction and side of amobarbital brain inactivation. Euphoria was more frequent following right, and depression was more common after left, hemisphere inactivation. Although support was found for both premorbid personality and lesion location in the genesis of emotional reactions after brain damage, results were more robust for location of lesion.
Adult↗
How does the fable end? A reply to Hartlage.
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Comment↗
Cerebral lateralization and histamine skin test asymmetries in humans.
Although asymmetries exist in both cerebral and somatic systems, their relationship is not well understood. One hypothesis suggests that some processes determining cerebral hemispheric dominance also affect immune systems. We employed histamine, a final common mediator for the immediate hypersensitivity immune response, to examine the relationship of skin response to cerebral lateralization (ie, left versus right brain dominance). Histamine skin wheal responses on the left and right forearms were measured using computerized planimetry in 176 consecutive patients undergoing allergy skin testing. Cerebral lateralization was determined by personal and family handedness via questionnaires. Subjects were classified as right handed (RH) with only RH relatives, RH with non-RH relatives, or non-RH (ie, left-handed or ambidextrous). Left/right arm asymmetries in wheal area were demonstrated and were related to cerebral dominance, but could not be explained by simple arm use. Right-handed subjects with only RH relatives had greater wheal size on the right arm, RH subjects with non-RH relatives had no significant left/right difference in wheal size, and non-RH subjects had greater wheal size on the left arm. Further, gender differences in these asymmetries appeared to be present for subjects with mixed cerebral dominance. The results suggest an association between process affecting cerebral and somatic asymmetries, and offer new insight into brain/body interactions.
Adolescent↗
Neuropsychological effects of antiepileptic drugs: a current perspective.
Epilepsy has widespread direct and indirect effects on the patient's quality of life. These patients generally have neuropsychological impairments that lower their educational and occupational levels of achievement, and many have additional emotional and/or behavioral disorders. Multiple factors underlie the cognitive changes associated with epilepsy, including the effect of antiepileptic drug (AED) therapy itself. Although it is recognized that the beneficial results of reduced seizure frequency may compensate at least in part for detrimental cognitive AED side effects, polypharmacy and higher AED blood levels can shift this balance. Further, there is much debate concerning the existence and clinical importance of differential AED cognitive side effects. While all the major AEDs can produce cognitive side effects, more recent research indicates that the magnitude of these effects may not be clinically significant with monotherapy within standard therapeutic range. The impact of AED differential cognitive side effects on the patient's quality of life is only beginning to be appreciated as research focuses on this important aspect of patient management. The information gained from such investigations will influence not only current therapeutic decisions, but also the development of future anticonvulsants.
Adult↗
Differential effects of left versus right seizure focus on human hippocampal evoked responses.
Hippocampal evoked potentials were recorded using the P3 tonal oddball paradigm in 30 patients with unilateral temporal lobe seizure focus. Spectral power of the evoked potentials was decreased on the side of seizure focus, but this reduction was much greater when the focus was on the left. The effect of left/right focus does not appear to be due to group differences in age, sex, seizure duration, or operative pathology. Remote or finer left/right structural differences or differential left/right hippocampal processing for the sequential tonal task are possible explanations.
Adolescent↗
Diazepam effects on the P3 event-related potential.
Cerebral event-related potentials arise from synchronous neural activity associated with cognitive processing. The P3 is a late positive component that is related to task complexity and is directly proportional to stimulus evaluation time. P3 latency and amplitude were examined after oral administration of diazepam, a commonly prescribed medication with known cognitive side effects. Latency of the P3 was significantly increased after a single dose of both 5 and 10 mg of diazepam but not after placebo. P3 amplitude decreased slightly, but not significantly after 10 mg of diazepam. Changes in P3 occurred in the absence of significant changes in the preceding evoked waves (N1, P2). These findings should be considered when the P3 is obtained for clinical or research purposes from medicated patients.
Acoustic Stimulation↗
Allochiria vs allesthesia. Is there a misperception?
Allochiria is the mislocation of sensory stimuli to the corresponding opposite half of the body or space. Obersteiner (1882) introduced the term allochiria (Greek allos = other + chiria = hand), and more than 20 authors employed it in this context over the next 25 years. Stewart (1894) described a related phenomenon in which stimuli are displaced to a different point on the same extremity. He noted that the displacements were different than allochiria and coined the term allachaesthesia (ie, allesthesia) (Greek allaché = elsewhere + aisthésis = perception). Despite this historical background, Jones (1907) redefined both terms in an attempt to increase diagnostic specificity and attributed allochiria to hysteria. Jones' reinterpretation does not appear to be justified historically, etymologically, or scientifically and has resulted in contradictory definitions of allochiria and allesthesia in present-day medical dictionaries and neurologic textbooks. We advocate a return to usage consistent with the original descriptions and word derivations.
Europe↗
Hippocampal contribution to verbal recent memory following dominant-hemisphere temporal lobectomy.
The effects of hippocampal encroachment in the language dominant-hemisphere were studied in 41 patients who underwent previous temporal lobectomy (TL). Patients undergoing dominant-hemisphere TL including anterior hippocampus (n = 13) performed significantly worse than nondominant TL patients (n = 16) on a verbal learning test (Selective Reminding; p less than or equal to .00001), thereby confirming the sensitivity of this procedure to lateralized temporal-lobe dysfunction. However, no significant difference was present on this or other primary measures of material-specific memory when contrasting dominant TL patients in whom the anterior hippocampus was spared (n = 12) to those in whom anterior hippocampus was resected. These data suggest that more extensive and posterior mesial temporal-lobe resection is not necessarily associated with a greater verbal material-specific memory deficit following dominant-hemisphere temporal lobectomy.
Adult↗
Differential effects of unilateral temporal lobectomy on visuospatial memory and attention.
We investigated free recall of visuospatial arrays in a free-field format in epileptic patients following unilateral temporal lobectomy (TL) (left = 15, right = 17). TL patients exhibited leftward deviation in right hemispace, but more variable response in left hemispace, a pattern that has been observed in healthy adults. This finding is postulated to result from combined preferential right cerebral activation and a tendency to err toward peri-personal space. Temporal lobectomy affected overall leftward deviation by initially shifting deviation more toward the side of lesion. The initial directional shift in immediate memory dissipated over time suggesting that these subtle attentional shifts may be compensated by learning. Consistent with differential cerebral hemispheric mechanisms, absolute vertical errors were greater in right than left TL patients, and absolute horizontal errors were worse in right hemispace.
Adult↗
Comparative cognitive effects of carbamazepine and phenytoin in healthy adults.
We investigated neuropsychological effects of carbamazepine and phenytoin in 21 healthy adults using a randomized, double-blind, double-crossover design and treating each subject with each drug for 1 month, separated by a 1-month washout. There were neuropsychological evaluations at baseline, the end of each treatment month, and 1 month after the last treatment phase. Cognitive measures included Symbol Digit Modalities Test, Selective Reminding Test, Complex Figures, Paced Auditory Serial Addition Test, Stroop, Finger Tapping, Grooved Pegboard, Choice Reaction Time, P3 Event-Related Potential, Hopkins Symptom Checklist, and Profile of Mood States (POMS). Compared with nondrug conditions, the anticonvulsants significantly impaired Stroop, Choice Reaction Time, Grooved Pegboard, Hopkins, and POMS. Employing anticonvulsant blood levels as covariates, there were only two significant differences between drugs, one in favor of carbamazepine (ie, Finger Tapping) and one in favor of phenytoin (ie, Stroop). The results suggest that differences in cognitive effects of carbamazepine and phenytoin are not clinically significant.
Adult↗
Behavioral state-specific changes in human hippocampal theta activity.
Although there has been extensive examination of the behavioral and physiologic correlates of hippocampal theta activity in animals, the human literature consists of a single case study. We investigated the differential effects of four behavioral states on human hippocampal theta activity in 16 epilepsy surgery patients. Behavioral conditions included resting eyes closed (RC), resting eyes open (RO), eyes open with auditory word activation (AW), and eyes open with visuospatial activation (VS). Hippocampal theta activity decreased during both RO and VS compared to both RC and AW. There were reciprocal changes in delta activity. Comparisons of RO to VS and of RC to AW were nonsignificant. The results demonstrate state-specific changes in human hippocampal theta and are consistent with the animal literature that relates hippocampal theta to sensorimotor integration and forebrain volitional mechanisms.
Adolescent↗