Material-specific memory in the intracarotid amobarbital procedure

We examined material-specific memory in 45 left hemisphere language dominant patients with temporal complex partial seizures (24 right, 21 left) during the intracarotid amobarbital procedure (IAP) by showing eight cards displaying two line drawings of common objects, two printed words, one colored shape, one math expression, one face, and one abstract shape following amobarbital injection (mean = 109.9 mg). We assessed delayed recall and recognition following clearing. Patients with right foci recognized significantly fewer verbally mediated stimuli (words, object drawings, colored shape) with left than with right injection. Patients with left foci recognized a nonverbal stimulus (abstract shape) more poorly following right versus left injection. Discriminant function analysis lateralized 85% of the sample from memory predictors, upheld to 81% on crossvalidation. Material-specific memory remains intact in the hemisphere contralateral to a seizure focus, but wider representation may occur for stimuli normally dominant for the hemisphere with the seizure focus. The IAP significantly lateralizes a seizure focus with use of both types of stimuli.     

MRI-radiofrequency tissue tagging in patients with aortic insufficiency before and after operation

We examined the relation between language dominance and regional cerebral blood flow (rCBF) during the intracarotid amobarbital procedure (IAP). A previous report limited to three patients suggested that dominant rather than nondominant hemisphere IAP may have a differential effect on rCBF. Behavioral assessment during the IAP also suggests that dominant hemisphere injection results in a differential effect on memory and affective symptoms rather than nondominant injection. Thirteen patients were assessed using single-photon emission CT (SPECT) brain imaging during both left and right IAP. The SPECTs were coregistered with the individual's MRI. Changes in rCBF during each IAP were compared with the patient's baseline SPECT. Nine patients had left hemisphere dominance, two were right dominant, and two had bilateral speech representation. In the left dominant subjects, left-hemisphere injection had a consistently greater effect on rCBF than right-hemisphere injection in the anterior (p < 0.005) and posterior (p < 0.01) temporal neocortex. There was also a trend for greater hypoperfusion in the frontal lobe of the left hemisphere. rCBF in the ipsilateral hippocampus was not significantly different after each injection (p > 0.05). In the two patients with right hemisphere speech, the reverse pattern was seen, with greater hypoperfusion after right (dominant) hemisphere injection. There was no consistent asymmetry in the two patients with bilateral speech. Dominant hemisphere IAP results in significantly greater hypoperfusion than does nondominant injection. These data provide a physiologic basis for behavioral differences noted after dominant versus nondominant IAP.     

Surgical management of aortic regurgitation associated with ventricular septal defect

The intracarotid amobarbital procedure was carried out in 8 male and 7 female candidates to temporal lobectomy, and a female candidate to frontal lesionectomy, aged 18-50 (mean 32.5) years. Language and memory were tested after injection in each hemisphere. Both were measured by the Montreal procedure. In 9 patients language and memory were evaluated with the Seattle procedure too. In 12 patients the left hemisphere was dominant for language; three had bilateral dominance. In 1 patient the Seattle procedure demonstrated the dominant hemisphere by relatively slowness of speech during the drug effect in the left hemisphere. Memory was defined to be in the left hemisphere in 12 patients, in the right in 2, bilateral in 1 and in another lateralization was not possible. In 1 patient memory dominance was determined by the Montreal protocol alone because of lack of cooperation. These early results indicate that the methods may be complementary for determination of language and memory dominance in epilepsy surgery candidates.     

Anatomic correlates of memory from intracarotid amobarbital injections with technetium Tc 99m hexamethylpropyleneamine oxime SPECT

OBJECTIVE: To better identify regions of the brain affected by intracarotid amobarbital injections and to more precisely predict whether resections of specific brain regions will cause postoperative memory deficits. DESIGN: We modified the standard intracarotid amobarbital procedure by adding a radioactive tracer to the amobarbital injection, thereby providing better correlation between behavior and deactivated brain region. SETTING: Tertiary-care hospital center with a dedicated program for medical and surgical treatment of epilepsy. PATIENTS: We studied 39 patients with medically intractable epilepsy drawn from a regional referral base. INTERVENTION: Intracarotid injection of 125 mg of sodium amobarbital with 37 MBq of technetium Tc 99m hexamethylpropyleneamine oxime (HMPAO), followed by language and memory testing. MAIN OUTCOME MEASURES: The distribution of amobarbital as measured by single photon emission computed tomographic imaging of HMPAO and patient performance on memory tasks. RESULTS: Medial temporal regions were irrigated by the amobarbital in only 28% of the injections. Overall, findings suggest that medial temporal and lateral neotemporal cortex play a role in memory. CONCLUSIONS: The regions involved in memory function vary by individual, as does the distribution of amobarbital. Thus, the most accurate method of determining correlation of brain region with memory function during intracarotid amobarbital injection involves the use of a tracer such as HMPAO.     

A reconsideration of bilateral language representation based on the intracarotid amobarbital procedure

Hemispheric language dominance was established for 368 epilepsy surgery candidates based on results of objective language performance during the intracarotid amobarbital procedure. Eight-three percent of patients were found to be left hemisphere dominant, while six percent were right dominant, and eleven percent demonstrated some degree of bilateral language representation. Bilateral patients were grouped according to modality-specific patterns of language performance in each hemisphere, with a majority demonstrating left hemisphere superiority in overall language processing. Variables affecting atypical language development are reviewed and results are considered in the context of previous research.     

Verbal working memory components can be selectively influenced by transcranial magnetic stimulation in patients with left temporal lobe epilepsy

The aim of this study was to investigate whether transcranial magnetic stimulation (TMS) can be used for a lateralization of verbal and non-verbal memory functions in candidates for epilepsy surgery by inducing focal, material-specific memory deficits. Twenty patients who underwent presurgical epilepsy evaluation with chronically implanted subdural strip electrodes were submitted to focal TMS over the temporal lobes and the vertex while sequences of items of the Digit Span and the Corsi Block test were presented on a computer screen. TMS was applied synchronously or 200 msec following presentation of each item. The effects of TMS on the memory span and the serial position curve were analysed in comparison to baseline levels. The following results were obtained: the quantitative effects on the verbal (Digit Span) and non-verbal (Corsi Block) memory span were not significant, but there were significant qualitative changes of serial position effects. In the group of six patients with left temporal epilepsy, TMS over the left temporal lobe induced a significant recency effect in the Digit Span test, while TMS over the vertex significantly increased the recency errors. The absolute number of errors remained unchanged. No such effects were observed in the group of nine patients with right temporal lobe epilepsy. These results suggest that in the presence of a left temporal lobe focus TMS can induce qualitative, material specific changes in verbal working memory (phonological loop) which become apparent in the serial position curve. The dissociation of TMS effects for temporal and vertex stimulation imply that TMS can selectively influence specific phonological loop components and that the phonological loop has a functionally and neuroanatomically multimodular structure.     

Objective criteria for reporting language dominance by intracarotid amobarbital procedure

We propose a standardized method for reporting language lateralization by intracarotid amobarbital procedure (IAP). We retrospectively reviewed 165 IAPs, and classified language lateralization as left, right, or bilateral by three different methods, all based on the duration of speech arrest following each injection: absolute duration, side-to-side difference, and a "laterality index" defined as (L-R/L+R). Cutoff values were obtained by studying a pure subgroup of left hemisphere dominant right-handed subjects. In 142 patients (86%), the classification remained unchanged among all three methods: left in 112 (79%), right in 19 (13%), and bilateral in 11 (8%). In the other 23 patients (14%), language classification varied among the three criteria used. The change of category was never between left and right, and always involved bilateral language. Thus, this index may be helpful in standardizing and comparing IAP results from different series.     

Rat testicular extracellular superoxide dismutase: its purification, cellular distribution, and regulation

Rehabilitative measures for stroke are not generally based on basic neurobiological principles, despite evidence from animal models that certain anatomical and pharmacological changes correlate with recovery. In this report, we use functional magnetic resonance imaging (fMRI) to study in vivo human brain reorganization in a right handed patient with an acquired reading disorder from stroke. With phonological dyslexia, her whole-word (lexical) reading approach included inability to read nonwords and poor reading of function words. Following therapy, she was able to read nonwords and function words, and preferred a decompositional (sub-lexical) strategy in general. fMRI was performed during a reading task before and after treatment. Prior to therapy, her main focus of brain activation was in the left angular gyrus (area 39). After therapy, it was instead in the left lingual gyrus (area 18). This result suggests first that it is possible to alter brain physiology with therapy for acquired language disorders, and second, that two reading strategies commonly used in normal reading use distinct neural circuits, possibly reconciling several conflicting neuroimaging studies of reading.     

Neural organization of material-specific memory functions in temporal lobe epilepsy patients as assessed by the intracarotid amobarbital test.

Lateralization of material-specific memory processing was evaluated in 105 epilepsy patients undergoing the intracarotid amobarbital test prior to temporal lobectomy (TL). Left hemisphere (LH) language dominant patients demonstrated LH specialization for long-term verbal recognition memory and right hemisphere specialization for visuospatial recognition memory. The pattern of hemispheric memory specialization was similar for LH language dominant patients with brain injuries before 2 yrs of age and those without history of early brain injury, suggesting that the apparent sparing of memory post-TL in early brain injury patients reflects reorganization of memory functions within the epileptic hemisphere. Non-LH-language dominant patients showed no lateral specialization for either verbal or visuospatial memory processing, suggesting that in these individuals reorganization of memory functions between hemispheres accompanies the lateral shift in language representation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A critical period in the sensitivity of basal forebrain cholinergic neurones to NGF deprivation

OBJECTIVE: We undertook this study to investigate functional MR imaging as a new clinical method for determining hemispheric language dominance. Seven patients undergoing surgical evaluation for chronic intractable epilepsy were studied. Intracarotid amobarbital injection was also performed and the findings compared with the functional MR imaging results. CONCLUSION: Functional MR imaging studies enabled localization of the frontal and temporal lobe language cortices. The results of functional MR imaging and intracarotid amobarbital testing of hemispheric language dominance agreed in all seven patients, including two right-handed patients with right-hemisphere language dominance. These preliminary results show that functional MR imaging is an accurate noninvasive method of determining language dominance that may replace the amobarbital test for some purposes if confirmed by additional research.     

Microvessel density of invasive breast cancer assessed by dynamic Gd-DTPA enhanced MRI

We compared Wada memory performance for stimuli presented at two timing intervals following amobarbital injection in 47 non-lesional patients with complex partial seizures (L = 26; R = 21). A significant interaction between seizure focus and timing of presentation was present (P < 0.03). Memory performance for objects whose presentation began approximately 50-55 s following amobarbital administration differed as a function of ipsilateral vs. contralateral injection at a very high level of statistical significance (P < 0.00001). Items presented approximately 4 min, 30 s post injection were also related to seizure onset literality, but at a lower statistical level (P < 0.01). Presentation of Wada memory stimuli earlier during hemispheric anaesthesia yields results that are more sensitive to lateralized temporal lobe seizure onset than does presentation of items later during the procedure.     

Language lateralization of Chinese-English bilingual patients with temporal lobe epilepsy: A functional MRI study.

Functional MRI was used to examine language lateralization of Chinese characters and English words associated with temporal lobe epilepsy (TLE) in Chinese-English bilinguals with left or right TLE. The results suggest that the neural basis of processing Chinese and English seems to be different, as normal controls demonstrated left hemispheric lateralization in reading English words but bi-hemispheric lateralization in reading Chinese characters. This difference in the neural bases of Chinese and English processing was found to affect the patterns in change-of-language processing associated with TLE. That is, whereas left-TLE patients were more likely than right-TLE patients to demonstrate a bi-hemispheric language involvement in reading English, both left- and right-TLE patients demonstrated primarily bilateral hemispheric involvement for reading Chinese characters. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Permanent rescue of lesioned neonatal motoneurons and enhanced axonal regeneration by adenovirus-mediated expression of glial cell-line-derived neurotrophic factor

Studies of patients with brain damage suggest that specific brain regions may be differentially involved in representing/processing certain categories of conceptual knowledge. With regard to the dissociation that has received the most attention--between the domains of living things and artifacts--a debate continues as to whether these category-specific effects reflect neural implementation of categories directly or some more basic properties of brain organization. The present positron emission tomography (PET) study addressed this issue by probing explicitly for differential activation associated with written names of objects from the domains of living things or artifacts during similarity judgments about different attributes of these objects. Subjects viewed triads of written object names and selected one of two response words as more similar to a target word according to a specified perceptual attribute (typical color of the objects) or an associative attribute (typical location of the objects). The control task required a similarity judgment about the number of syllables in the target and response words. All tasks were performed under two different stimulus conditions: names of living things and names of artifacts. Judgments for both domains and both attribute types activated an extensive, distributed, left-hemisphere semantic system, but showed some differential activation-particularly as a function of attribute type. The left temporo-occipito-parietal junction showed enhanced activity for judgments about object location, whereas the left anteromedial temporal cortex and caudate nucleus were differentially activated by color judgments. Smaller differences were seen for living and nonliving domains, the positive findings being largely consistent with previous studies using objects; in particular, words denoting artifacts produced enhanced activation in the left posterior middle temporal gyrus. These results suggest that, within a distributed conceptual system activated by words, the more prominent neural distinction relates to type of attribute.     

The anterior and posterior selective temporal lobe amobarbital tests: angiographic, clinical, electroencephalographic, PET, SPECT findings, and memory performance

The techniques, results, and problems of three types of selective temporal lobe (TL) amobarbital procedures (balloon technique with temporary occlusion of the internal carotid artery distal to the origin of the anterior choroidal artery (acha) [n = 19]; selective anterior catheterization of the acha [n = 20]; and selective catheterization of the peduncular P2-segment of the posterior cerebral artery [n = 5]) are described in a group of 40 patients with medically refractory complex partial seizures of mesial TL origin. Selective amobarbital tests were carried out before surgery to predict the memory deficit after an intended selective amygdalohippocampectomy. The effects of selective anaesthetization of TL were correlated with clinical data, pattern and duration of amobarbital induced EEG changes, and performance on verbal and nonverbal memory tasks measured during the test. In 4 patients the effect of selective amobarbital injection on regional and global metabolism was studied with 18F-FDG-PET, with the PET tracer being injected intravenously immediately after amobarbital. More recently in 2 patients the vascular territory perfused by amobarbital in the acha test was studied with SPECT using 99m Tc ECD injected immediately prior to the amobarbital into the acha. Whereas the PET studies showed a rather widespread and bilateral amobarbital-induced decrease of metabolism, the SPECT studies confirmed the selective distribution of the tracer in the vascular territory of the acha, i.e., in amygdala and hippocampus. The comparison of selective TL amobarbital test performance with postoperative neuropsychological performance showed that the predictive value of this test is rather good for the postoperative verbal memory but underestimates postoperative nonverbal ("figural") memory performance.     

Exploring the neural organization of person-related knowledge: Lateralization of lesion, category specificity, and stimulus modality effects.

While it is generally agreed that the right fusiform gyrus is specialized for face recognition, the question of whether knowledge about persons is lateralized in the temporal lobes is more contentious. Does knowledge about people differ from other kinds of object knowledge with respect to brain laterality? Are side-of-lesion effects mediated by stimulus modality? This study aimed to investigate these questions by comparing patients with left temporal (LT) (n = 8) and right temporal (RT) (n = 11) lesions to control subjects (n = 12) on verbal and visual tests of people, buildings, and objects. The RT group was impaired at recognizing famous faces, but not at choosing the picture of a famous building or a famous name from nonfamous distracters. The LT group was impaired at naming people, buildings, and objects, regardless of stimulus modality. When presemantic processing was controlled for, neither patient group was impaired in producing person-specific knowledge to faces or names, supporting the notion that semantic knowledge for people as for other kinds of objects, is stored in a distributed network across both hemispheres, regardless of stimulus modality. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Neural correlates of the episodic encoding of pictures and words

A striking characteristic of human memory is that pictures are remembered better than words. We examined the neural correlates of memory for pictures and words in the context of episodic memory encoding to determine material-specific differences in brain activity patterns. To do this, we used positron emission tomography to map the brain regions active during encoding of words and pictures of objects. Encoding was carried out by using three different strategies to explore possible interactions between material specificity and types of processing. Encoding of pictures resulted in greater activity of bilateral visual and medial temporal cortices, compared with encoding words, whereas encoding of words was associated with increased activity in prefrontal and temporoparietal regions related to language function. Each encoding strategy was characterized by a distinctive activity pattern, but these patterns were largely the same for pictures and words. Thus, superior overall memory for pictures may be mediated by more effective and automatic engagement of areas important for visual memory, including medial temporal cortex, whereas the mechanisms underlying specific encoding strategies appear to operate similarly on pictures and words.     

Multiwell 14CO2-capture assay for evaluation of substrate oxidation rates of cells in culture

The functional anatomy of the interactions between spoken language and visual mental imagery was investigated with PET in eight normal volunteers during a series of three conditions: listening to concrete word definitions and generating their mental images (CONC), listening to abstract word definitions (ABST) and silent REST. The CONC task specifically elicited activations of the bilateral inferior temporal gyri, of the left premotor and left prefrontal regions, while activations in the bilateral superior temporal gyri were smaller than during the ABST task, during which an additional activation of the anterior part of the right middle temporal gyrus was observed. No activation of the occipital areas was observed during the CONC task when compared either to the REST or to the ABST task. The present study demonstrates that a network including part of the bilateral ventral stream and the frontal working memory areas is recruited when mental imagery of concrete words is performed on the basis of continuous spoken language.     

Functional MRI activation in children with and without dyslexia during pseudoword aural repeat and visual decode: Before and after treatment.

Children without dyslexia (n=10) received nonphonological treatment, and those with dyslexia received phonological (n=11) or nonphonological (n=9) treatment. Before and after treatment they performed aural repeat, visual decode, and aural match pseudoword tasks during functional MRI scanning that separated stimulus input from response production. Group map analysis indicated that children with dyslexia overactivated compared with good readers during the aural-repeat/aural-match contrast in bilateral frontal (Brodmann's area [BA] 3, 4, 5, 6, 9), left parietal (BA 2, 3), left temporal (BA 38), and right temporal (BA 20, 21, 37) regions (stimulus input) and underactivated in right frontal (BA 24, 32) and right insula (BA 48) regions (response production); they underactivated in BA 19/V5 during the visual-decode/aural-match contrast (response production). Individual brain analysis for children with dyslexia revealed that during the aural-repeat/aural-match contrast (stimulus input), phonological treatment decreased and normalized activation in left supramarginal gyrus and postcentral gyrus. Nonphonological treatment increased and normalized activation during the visual-decode/aural-match contrast (response production) in BA19/V5 and changed activation in the same direction as good readers during aural-repeat/aural-match contrast (stimulus input) in left postcentral gyrus. The significance of the findings for competing theories of dyslexia is discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Preoperative predictors of anterior temporal language areas

OBJECT: Although it is known that 5 to 10% of patients have language areas anterior to the rolandic cortex, many surgeons still perform standard anterior temporal lobectomies for epilepsy of mesial onset and report minimal long-term dysphasia. The authors examined the importance of language mapping before anterior temporal lobectomy. METHODS: The authors mapped naming, reading, and speech arrest in a series of 67 patients via stimulation of long-term implanted subdural grids before resective epilepsy surgery and correlated the presence of language areas in the anterior temporal lobe with preoperative demographic and neuropsychometric data. Naming (p < 0.03) and reading (p < 0.05) errors were more common than speech arrest in patients undergoing surgery in the anterior temporal lobe. In the approximate region of a standard anterior temporal lobectomy, including 2.5 cm of the superior temporal gyrus and 4.5 cm of both the middle and inferior temporal gyrus, the authors identified language areas in 14.5% of patients tested. Between 1.5 and 3.5 cm from the temporal tip, patients who had seizure onset before 6 years of age had more naming (p < 0.02) and reading (p < 0.01) areas than those in whom seizure onset occurred after age 6 years. Patients with a verbal intelligence quotient (IQ) lower than 90 had more naming (p < 0.05) and reading (p < 0.02) areas than those with an IQ higher than 90. Finally, patients who were either left handed or right hemisphere memory dominant had more naming (p < 0.05) and reading (p < 0.02) areas than right-handed patients with bilateral or left hemisphere memory lateralization. Postoperative neuropsychometric testing showed a trend toward a greater decline in naming ability in patients who were least likely to have anterior language areas, that is, those with higher verbal IQ and later seizure onset. CONCLUSIONS: Preoperative identification of markers of left hemisphere damage, such as early seizure onset, poor verbal IQ, left handedness, and right hemisphere memory dominance should alert neurosurgeons to the possibility of encountering essential language areas in the anterior temporal lobe (1.5-3.5 cm from the temporal tip). Naming and reading tasks are required to identify these areas. Whether removal of these areas necessarily induces long-term impairment in verbal abilities is unknown; however, in patients with a low verbal IQ and early seizure onset, these areas appear to be less critical for language processing.     

Comparison between oral and written spelling in Alzheimer's disease

Written and oral spelling were compared in 33 patients with Alzheimer's disease (AD) and 25 control subjects. AD patients had poorer spelling results which were influenced by orthographic difficulty and word frequency, but not by grammatical word class. Lexical spelling was also more deteriorated than phonological spelling. Moreover, oral spelling was more impaired than written spelling in AD patients, whereas no difference was present between oral and written spelling of controls. Analysis of spelling errors showed that, for controls, errors were predominantly phonologically accurate in both spelling tasks. Significantly, AD patients produced more phonologically accurate than inaccurate errors in written spelling, whereas these errors did not differ in oral spelling. In contrast to controls who produced more constant than variable responses in oral and written spelling, AD patients made more variable responses (words correctly spelled in one task but incorrectly in the other) and they showed many instances of variable errors (different misspellings from one spelling task to the other). Two stepwise regression procedures showed that written misspellings were specifically correlated with language impairment, whereas oral spelling errors were correlated with attentional and language disorders. These results suggest that AD increases the attentional demands of oral spelling process as compared to written spelling. This dissociation argues, either for a unique Graphemic Buffer in which oral spelling requires more attentional resources than written spelling or for the hypothesis of separate buffers for oral and written spelling.