Left Posterior Temporal Lobe Research Articles

Sentence comprehension and word repetition: A positron emission tomography investigation

Using positron emission tomography, visual presentation of sentences was shown to cause increased regional cerebral blood flow relative to word lists in the left lateral anterior superior and middle temporal gyri, attributable to cognitive processes that occur during sentence comprehension in addition to those carried out during word comprehension. Additional comparisons showed that repeating words (in a different context, when subjects did not attempt to learn the initial lists) led to significant patterns of both increased blood flow (left putamen and right caudate) and decreased blood flow (left posterior temporal lobe). Increases are argued to reflect retrieval of memory traces, whereas decreases reflect diminished necessity for processing of input. A decrease in the left inferior parietal lobe was attributable to other factors.

Functional differentiation of medial temporal and frontal regions involved in processing novel and familiar words: an fMRI study.

Results of recent functional magnetic resonance imaging (fMRI) studies of memory are not entirely consistent with lesion studies. Furthermore, although imaging probes have identified neural systems associated with processing novel visual episodic information, auditory verbal memory using a novel/familiar paradigm has not yet been examined. To address this gap, fMRI was used to compare the haemodynamic response when listening to recently learned and novel words. Sixteen healthy adults (6 male, 10 female) learned a 10-item word list to 100% criterion, approximately 1 h before functional scanning. During echo-planar imaging, subjects passively listened to a string of words presented at 6-s intervals. Previously learned words were interspersed pseudo-randomly between novel words. Mean scans corresponding to each word type were analysed with a random-effects model using statistical parametric mapping (SPM96). Familiar (learned) words activated the right prefrontal cortex, posterior left parahippocampal gyrus, left medial parietal cortex and right superior temporal gyrus. Novel words activated the anterior left hippocampal region. The results for the familiar words were similar to those found in other functional imaging studies of recognition and retrieval and implicate the right dorsolateral prefrontal and left posterior medial temporal lobe (MTL) regions. The results for novel words require replication, but are consistent with the substantial lesion and PET literature implicating the anterior MTL as a critical site for processing novel episodic information, presumably to permit encoding. Together, these results provide evidence for an anterior-posterior functional differentiation within the MTL in processing novel and familiar verbal information. The differentiation of MTL functions that was obtained is consistent with a large body of PET activation studies but is unique among fMRI studies, which to date have differed from results with PET. Further, the finding of left MTL lateralization is consistent with lesion-based material-specific models of memory.

Repetitive transcranial magnetic stimulation of the dominant hemisphere can disrupt visual naming in temporal lobe epilepsy patients

We used repetitive transcranial magnetic stimulation (rTMS) to study visual naming in 14 patients with temporal lobe epilepsy. Ten had left hemisphere language by Wada testing and all experienced speech arrest with rTMS of the motor speech area in the left frontal lobe. One left-hander had speech arrest with stimulation of sites on both sides. Subjects were asked to name pictures or read words presented on a computer monitor. rTMS was delivered on half of the trials. Stimulation sites were the motor speech area in the left frontal lobe, the mirror site on the right, and the left and right mid superior and posterior temporal lobes. rTMS at left hemisphere sites caused more naming errors than did right hemisphere rTMS. All individual subjects, except two who had temporal lobe resections and the one with bilateral speech arrest, produced more naming errors with rTMS of left hemisphere sites. There was no significant effect on word reading. rTMS at the left hemisphere and right frontal sites produced reductions in reaction time for picture naming, but not for word reading. This was observed for both correct and incorrect responses. This study shows that left hemisphere rTMS can disrupt visual naming selectively.

An MEG study of picture naming.

The purpose of this study was to relate a psycholinguistic processing model of picture naming to the dynamics of cortical activation during picture naming. The activation was recorded from eight Dutch subjects with a whole-head neuromagnetometer. The processing model, based on extensive naming latency studies, is a stage model. In preparing a picture"s name, the speaker performs a chain of specific operations. They are, in this order, computing the visual percept, activating an appropriate lexical concept, selecting the target word from the mental lexicon, phonological encoding, phonetic encoding, and initiation of articulation. The time windows for each of these operations are reasonably well known and could be related to the peak activity of dipole sources in the individual magnetic response patterns. The analyses showed a clear progression over these time windows from early occipital activation, via parietal and temporal to frontal activation. The major specific findings were that (1) a region in the left posterior temporal lobe, agreeing with the location of Wernicke"s area, showed prominent activation starting about 200 msec after picture onset and peaking at about 350 msec (i.e., within the stage of phonological encoding), and (2) a consistent activation was found in the right parietal cortex, peaking at about 230 msec after picture onset, thus preceding and partly overlapping with the left temporal response. An interpretation in terms of the management of visual attention is proposed.

The functional anatomy of word comprehension and production

This review describes the functional anatomy of word comprehension and production. Data from functional neuroimaging studies of normal subjects are used to determine the distributed set of brain regions that are engaged during particular language tasks and data from studies of patients with neurological damage are used to determine which of these regions are necessary for task performance. This combination of techniques indicates that the left inferior temporal and left posterior inferior parietal cortices are required for accessing semantic knowledge; the left posterior basal temporal lobe and the left frontal operculum are required for translating semantics into phonological output and the left anterior inferior parietal cortex is required for translating orthography to phonology. Further studies are required to establish the specific functions of the different regions and how these functions interact to provide our sophisticated language system.

Right hemisphere speech perception revealed by amobarbital injection and electrical interference

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

A multimodal language region in the ventral visual pathway.

Reading words and naming pictures involves the association of visual stimuli with phonological and semantic knowledge. Damage to a region of the brain in the left basal posterior temporal lobe (BA37), which is strategically situated between the visual cortex and the more anterior temporal cortex, leads to reading and naming deficits. Additional evidence implicating this region in linguistic processing comes from functional neuroimaging studies of reading in normal subjects and subjects with developmental dyslexia. Here we test whether the visual component of reading is essential for activation of BA37 by comparing cortical activations elicited by word processing in congenitally blind, late-blind and sighted subjects using functional neuroimaging. Despite the different modalities used (visual and tactile), all groups of subjects showed a common activation of BA37 by words relative to non-word letter-strings. These findings agree with the proposal that BA37 is an association area that integrates converging inputs from many regions. Our study confirms a prediction of theories of brain function that depend on convergence zones; the absence of one input (that is, visual) does not alter the response properties of such a convergence region.

Worsening of Partially Recovered Aphasia After a Right Occipital Stroke

We present the first case of deterioration of aphasia associated with a nondominant (right) hemisphere lesion in an area that is nonhomotopic to left hemisphere language zones. A 70-year-old right-handed woman, who had partially recovered from Wer nicke's aphasia after a left posterior temporal and occipital lobe ischemic infarct, pre sented with sudden deterioration of aphasia. Imaging studies of the brain showed a new intraparenchymal hemorrhage in the right occipital lobe. Speech evaluation demonstrated worsening of comprehension, repetition, writing, and verbal expression. During a 4-month follow-up period, a small improvement in the ability to repeat was made, but no gains in functional language skills were achieved. This study provides evidence for participation of the right hemisphere in recovery from aphasia after left hemisphere damage. It also suggests that the subsequent lesions in the right hemi sphere cortex may not necessarily have to be located within an area that is homotopic to left hemis...

The Neural Substrate for Concrete, Abstract, and Emotional Word Lexica A Positron Emission Tomography Study

Viewing of single words produces a cognitively complex mental state in which anticipation, emotional responses, visual perceptual analysis, and activation of orthographic representations are all occurring. Previous PET studies have produced conflicting results, perhaps due to the conflation of these separate processes or the presence of subtle differences in stimulus material and methodology. A PET study of 10 normal individuals was carried out using the bolus H2(15)O intravenous injection technique to examine components of processing of passively viewed words. Subjects viewed blocks of random-letter strings or abstract, concrete, or emotional words (words with positive or negative emotional salience). Baseline conditions were either passive viewing of plus signs or an anticipatory state (viewing plus signs after being warned to expect words or random letters to appear imminently). All words (and to a lesser extent the random letters) produced robust activation of cerebral blood flow in the left posterior temporal lobe, in addition to bilateral occipital activation. Furthermore, emotional words produced activation in orbital and midline frontal structures. Further activation in the left orbital frontal gyrus, the left inferior temporal gyrus, the left caudate nucleus, the anterior cingulate, and the cerebellum could be ascribed to the anticipatory state. This pattern of activity suggests that the occipital regions are recruited for visual-perceptual analysis of words, and the left temporal lobe represents the neural substrate for the orthographic lexicon. In addition, emotionally relevant material produces further processing in limbic brain structures of the frontal lobes. Detailed analysis of the task therefore substantially clarifies the neuroanatomic basis of single-word processing.

On the Status of Object Concepts in Aphasia

While verbal comprehension is often impaired in aphasia due to left hemispheric damage, the status of nonverbal conceptual knowledge of objects remains controversial. We tested 16 aphasic subjects for their comprehension of concrete single words. Eight showed significant impairment on word-to-picture matching, when distractors were semantically and not just perceptually confusable. These 8 also made errors in answering verbal probe questions concerning the same items. When tested on a nonverbal pictorial version of the same probe questions, however, 3 of these 8 improved their performance to the level of normal controls. The other 5 showed continuing impairment in indicating responses to pictorial probes. These 5 showed no evidence of generalized intellectual impairment, and it is concluded that they demonstrated a comprehension deficit not limited to the verbal domain. Unlike the other aphasic patients, these latter 5 also had CT scan lesions extending into the posterior left temporal lobe (involving Brodmann's areas 22, 21, and 37). They were also more impaired in terms of general aphasia severity. It is suggested that a nonverbal (as well as verbal) semantic memory deficit occurs in a subgroup of patients with single word comprehension disturbance due to aphasia, and this may reflect general severity of language impairment as well as damage to certain localized brain regions.

Cognitive Conjunction: A New Approach to Brain Activation Experiments

This paper introduces the concepts and procedures of “cognitive conjunction,” a new approach to designing and analyzing cognitive activation experiments. Cognitive conjunction compliments categorical approaches such as cognitive subtraction and requires a specific form of statistical inference that involves the conjunction of several hypotheses. While cognitive subtraction studies are designed such that a pair of tasks differ only by the processing component(s) of interest, cognitive conjunction studies are designed such that two or more distinct task pairs each share a common processing difference. The neural correlates of the process of interest are then associated with the common areas of activation for each task pair. There are two main advantages of cognitive conjunction relative to cognitive subtraction. The first is that it provides a greater latitude for selecting baseline tasks because it is not necessary to control for all but the component of interest. The only constraint on selecting the baseline is that the component of interest is the only process that differs in each task pair. The second advantage is that cognitive conjunction does not depend on “pure insertion”—the assumption that the addition of an extra processing component in the activation task has no effect on the implementation of processes that are also engaged by the baseline task. The differences between the design and the statistical analysis of experiments based on cognitive subtraction, cognitive conjunction, and factorial designs are illustrated with a study of phonological retrieval. Cognitive conjunction analysis indicates that irrespective of whether subjects name words, objects, letters, or colors, there is activation of the left posterior basal temporal lobe, the left frontal operculum, the left thalamus, and the midline cerebellum.

Memory: recording experience in cells and circuits: diversity in memory research.

One of the long-standing and challenging issues that memory research continues to confront is the dilemma of localizing a complex function in an exquisitely anatomically differentiated central nervous system. Is memory a mental function that can be identified with an isolated neural structure or specific groups of neurons? Traditionally, this question has been framed by psychological inquiry. The 19th century school of “faculty psychology” divided mental processes into separate and distinct human attributes such as “courage” and “ambition,” encouraging the anatomist, Gall (1), to impose the multiple attributes of human psychological make-up onto a physical map of the brain. Although this naive view of psychological process was widely repudiated, it nevertheless spawned the powerful and ultimately validated idea that specific functions can be relegated to particular brain structures or regions. Clinical observations in patients with focal lesions in the last century clearly established a correspondence between specific symptoms and localized regions of injury, most notably left hemisphere frontal sites with expression of speech (2) and left hemisphere posterior temporal lobe sites with speech …

The neural regions sustaining object recognition and naming.

This positron emission tomography study dissociates the neural correlates of object recognition and naming. Stimuli comprised coloured outline drawings of objects and coloured nonsense shapes. Subjects either viewed or explicitly named objects, similarly they viewed or named the colour of the shapes. Activations common to object and colour naming were identified by contrasting the explicit naming conditions (objects and colours) with the control (viewing) conditions. Activations associated with object recognition were identified by contrasting both object conditions (naming and viewing) with both shape conditions and activations specific to object or colour naming were identified by contrasting object naming (relative to object viewing) with colour naming (relative to shape viewing). The results associate: (i) object recognition with left middle occipital and bilateral anterior temporal cortices; (ii) modality independent naming with left posterior basal temporal lobe and the left prefrontal cortex; (iii) areas specific to object naming with left temporal extrasylvian regions, left anterior insula and right cerebellum; and (iv) areas specific to colour naming with left posterior lingual and fusiform gyri and midline cerebellum. These results are discussed in relation to previous neuroimaging and neuropsychological findings.

脳神経外科領域に於ける顕微鏡下・内視鏡下レーザー手術の現状

Present situation of laser neurosurgery using operating microscope and endoscope are discussed. The lasers which we have mainly used are the CO2 laser and KTP laser. The CO2 laser is very useful to remove hard tissues, even calcified one, through narrow surgical field, especially in cases of deep-seated highly vascular tumors. A case of teratoma in the third ventricle and a case of deep-seated cavernous angioma in the left posterior temporal lobe which were removed by the CO2 laser are presented in this paper. The dural protector which we developed enables the operator to perform safe and complete removal of ossified posterior longitudinal ligament. Vaporizing capability of the KTP laser is far stronger than that of the YAG laser in the open-air surgical field. One of the advantages of the KTP laser is that it can be applied through fine optical fiber, which enable endoscopic use through CSF. And also the handpiece of the KTP laser can be designed very thin and light because this laser beam can be transmitted through optical fiber, which is very important in microsurgery. Recently we have started endoscopic examination of spinal lesions. This new technique revealed some interesting findings, such as rapid to and fro movement of CSF in the area where the subarachnoid space is narrowed, which is impossible to observe without this method. Hyper-vascularization of cauda equina caused by spinal tumor, thickning and adhesion of arachnoid were clearly observed by this sytem. However, development of special bipolar coagulator which can be applied through the working channel is indispensable prior to endoscopic interventions of spinal lesions, although the KTP laser is already applicable.

Antipsychotic Medication Changes the EEG of Schizophrenic Patients Towards Normal

In a study of the efficacy and safety of remoxipride compared with haloperidol in schizophrenia (DSM 111 R criteria), EEG frequencies were mapped before and after six weeks of medication. To be reported here, EEG changes had to reach statistical significance of t-scores of 3 or more and had to be present in both eyes-closed and eyes-open recordings. Delta (0.5-3.5 Hz) did not change significantly. Theta (4.0-7.5 Hz) decreased in the left anterior temporal, right frontal and right parietal lobes. Alpha (8.0-11.5) decreased in the right anterior temporal, left posterior temporal and right occipital lobes. Beta1 (12.0-15.5 Hz), beta2 (16-19.5 Hz) and beta3 (20.0-23.5 Hz) all decreased in the left posterior temporal lobe. Beta2 and 3 also decreased in the occipital lobes. Morstyn et al (1983) reported that in schizophrenia: (1) slow activity was increased anteriorly; (2) fast activity was increased posteriorly and in the left anterior temporal lobe. A very similar pattern was found in our patients before treatment. Antipsychotic medication returned our patients' EEGs towards normal. © 1994 American College of europsychopharmacology

Auditory perception of segmental features: a functional-neuroanatomic study

This study investigated the extent to which segmental feature perception depends on left-hemisphere mechanisms, as previously claimed. We used direct cortical electrical interference to examine purported lateralisation differences in the perception of stop consonants and vowels and in stop consonant voicing and place-of-articulation. Electrical interference was applied through indwelling subdural electrode arrays covering the lateral left perisylvian cortex of six patients with normal speech perception and language abilities. Extensive screening of the temporal lobe and other cortical regions revealed auditory syllable discrimination errors at only one posterior temporal site in each patient. Patients were significantly more impaired in detecting consonant differences than vowel differences, but showed no evidence of selective voicing or place-of-articulation impairments when pairs were contrasted in syllable-initial position. Moreover, discrepancies in patients' ability to detect place-of-articulation and voicing differences in syllable-final position were attributed to syllable context effects. These findings concur with previous claims concerning the relative importance of the left hemisphere for consonant perception, and further suggest that stop consonant processing is supported by a small region of the left posterior temporal lobe. Conversely, despite the specificity of electrical interference effects, our data do not support previous claims for the neurofunctional independence of stop consonant feature detectors, and furthermore suggest that no single feature may account for the lateralisation of stop consonant perception.

左側頭葉後下部の脳梗塞による失読失書の１例 ｀１２３´Ｉ‐ＩＭＰ３次元脳表面画像による検討

症例は62歳右利き男性.左側頭葉後下部の梗塞により, 漢字に強い失読失書と喚語困難を生じた。失読の回復は良好であったが, 特に漢字につよい失書を残した.123I-IMP脳表面画像により, 左側の中側頭回下半部より下側頭回にかけての皮質血流の低下が顕著であった.上側頭回や角回での血流低下は認められなかった.本邦で報告されている左側頭葉後下部損傷による失読失書の報告例と比較して, 本例は責任病巣の解剖学的分布をより明確に描出し得た.即ち, 優位半球の中側頭回下半部より下側頭回にかけての領域が漢字の読み書き, 特に書きに関与していること, 及び同部位の損傷により健忘失語が合併しうることを考察した.

Alexia with agraphia due to the left posterior inferior temporal lobe lesion—Neuropsychological analysis and its pathogenetic mechanisms

We report three cases of alexia with agraphia due to the left posterior inferior temporal lesions. In Case 1, the reading disability was more prominent in the use of Kana than in the use of Kanji, which is similar to previously reported cases of alexia with agraphia due to angular gyrus lesion. In Cases 2 and 3, by contrast, the reading disability was more prominent in the use of Kanji than in the use of Kana. In spontaneous writing and dictation, the disability was more pronounced in the use of Kanji compared with the use of Kana. In each of the three cases, the CT scan and positron emission tomography showed a localized lesion in the lower part of the left posterior temporal lobe. A typical form of an alexia with agraphia could be caused not only by the left angular lesion but also by the left posterior inferior temporal lesion. We discuss the neuropsychological analysis and pathogenetic mechanisms of alexia with agraphia due to the left posterior inferior temporal lesion in the comparison of alexia with agraphia caused by the left angular lesion.

Deficits in auditory-spatial integration of sequentially presented patterns due to cortical lesions

Groups of patients with cortical lesions were subjected to uniquely developed procedure to test auditory-spatial perception. The stimuli were comprised of a sound source, which sequentially outlined a pattern within a 10×10 matrix of loudspeakers. Simple sound patterns, which “moved” across the loudspeaker array only once or twice, were equally well identify by the control group and the various patient groups. However, the more complex patterns, which outlined the contour of alphabetical letters, resulted in significantly lowered identification rates for the patient groups with lesions in the right posterior, left posterior and left temporal lobes. As a control measure, visual-spatial tasks were administered, and lower performance rates were found for the left and right posterior groups. The differences and similarities between auditory-spatial and visual-spatial processing are discussed.