Left Temporoparietal Area Research Articles

Influence of duration of untreated psychosis on auditory P300 in drug‐naive and first‐episode schizophrenia

P300 amplitude reduction in schizophrenia is, according to previous studies, partially recovered by treatment with neuroleptics. However, whether this medication-induced P300 recovery is associated with duration of untreated psychosis (DUP) remains unreported; the present study is a preliminary examination of this question. Auditory P300 was recorded from 18 drug-naive and first-episode schizophrenia patients, among whom 10 were identified as short DUP, and eight as long DUP. Follow-up event-related potential tests were carried out after treatment with haloperidol or bromperidol for approximately 2 months. Recovery of P300 amplitude was replicated after neuroleptic medication was administered. A significant interaction was found between DUP and the medication effect in P300 amplitude over the left temporo-parietal area; a significant P300 recovery was seen in short DUP but not in long DUP. These results suggest that first-episode schizophrenia patients with long DUP might have severe impairments in the left temporal structures, supporting DUP as a key variable in future neurobiological studies of first-episode schizophrenia.

Diffusion changes suggesting predominant vasogenic oedema during partial status epilepticus

Diffusion-weighted imaging (DWI) has demonstrated a focal area of cytotoxic oedema during partial status epilepticus (PSE). However, vasogenic oedema related to the breakdown of the blood-brain-barrier (BBB) and ictal hyperperfusion could be the predominant DWI findings in the epileptogenic area during PSE. We report a case of PSE with ictal aphasia, right hemiparesis, and repetitive focal motor seizure of the right side. T2-weighted image (T2WI) and apparent diffusion coefficient (ADC) maps obtained during PSE showed an increased signal in the left temporo-parietal area, indicative of vasogenic oedema. EEG documented the ictal activities and single photon emission tomography (SPECT) showed asymmetrically increased perfusion in the corresponding area. Follow-up T2WI, DWI, and ADC maps obtained 3 months later showed the disappearance of the previous abnormalities. However, T2WI showed cortical atrophy and newly developed white matter changes in the corresponding area. This case shows that DWI findings may be variable during PSE, dependent on the predominance of cytotoxic and vasogenic oedema.

P300 alterations in schizophrenic patients experiencing auditory hallucinations

Rationale: Attentional deficits have been implicated in the pathophysiology of auditory hallucinations in schizophrenia. Since the latency of the P300 component of event-related potentials (ERPs) is considered to be a sensitive measure of stimulus classification speed, while its amplitude—a measure of attentional resource allocation when memory updating is engaged, the present study focuses on the comparison of P300 between healthy subjects and schizophrenic patients experiencing auditory hallucinations and treated with clozapine and olanzapine. Methods: The auditory P300 was assessed during the anticipatory period of a short memory test, in 16 male hallucinated schizophrenic patients and 13 male normal subjects matched for age and educational level. The patients were reexamined under identical conditions when their hallucinations had resolved following treatment with clozapine (8 patients) and olanzapine (8 patients). Results: The patients with hallucinations exhibited significantly reduced P300 amplitude at leads Fp1, F3, (C3-T5)/2, F4, Cz and Fz, when compared to the normal controls and at leads Fp1, F3, F4, (C4-T6)/2, C4, P4, Cz and Fz when compared to themselves during the remission phase. However logistic regression models revealed that the most important leads, differentiating the patient group before treatment either with the healthy controls, or with itself after treatment, were that at the left temporoparietal and at the left prefrontal area. Memory performance of the patient group, even after treatment and in spite of its significant improvement, remained significantly less than that of healthy controls. Both antipsychotic agents had similar effects on the P300 amplitude and memory performance. Conclusions: These findings indicate that auditory hallucinations in schizophrenia manifest abnormal aspects of attention, mediated by a distributed network involving or affecting the left temporoparietal and left prefrontal area. Additionally, the present study points to an improvement of attentional function in schizophrenic patients experiencing auditory hallucinations, both in the clozapine group but also in the olanzapine group.

The organisation of the bilingual lexicon: a PET study

In the literature on bilingualism, cognate relatedness has been shown to interact with proficiency in the foreign language such that cognate items are a measure of higher mastery than non-cognate ones. Systematic variation of these items in an activation study thus allows inter-subject control of different proficiency levels in the same bilingual subject. A positron emission tomography (PET) experiment was conducted with 11 Belgian subjects who were native speakers of Flemish/Dutch and had good proficiency in French. The experimental task consisted of internally naming pictures of objects in French and Dutch. For each language, there were two conditions. In one condition, the picture names were cognate across both languages, i.e. the translation equivalents shared phonological/orthographic similarity. In a second condition, picture names were non-cognate items without phonological/orthographic similarity in the French-Dutch translation equivalents. The items in both subsets were matched for visual complexity, object familiarity and familiarity of the French word. The results of our PET experiment on bilingual production showed hardly any difference between L2 cognates, L1 cognates and L1 non-cognates. The few significant differences of activation between L1 and L2 were almost exclusively due to increased activation for French non-cognate items in left inferior frontal and temporo-parietal areas. Thus, non-cognate foreign language naming recruited additional brain regions compared to native language non-cognate and native as well as foreign language cognate items. In our study, these areas of additional activation in L2 non-cognates were restricted to left hemispheric inferior frontal and temporal structures in or at the periphery of the known language areas. In conclusion, the bilingual production study presented here supports an important role of proficiency in activation differences between L1 and L2. The results suggest a relation between activation in left BA 20, BA 44 and BA 47 and effortful lexical retrieval. Our results are not in line with the hypothesis of entirely distinct neural substrates for the different languages of a bilingual individual.

Psychophysiological correlates in male to female transsexuals studied with a P300 investigation

Transsexualism is thought to be related to cortical processes reflecting a complex mosaic of biological, psychological and social/cultural information. Since the P300 component of event-related potentials is considered as an index of attentional processes, the present study focuses on auditory P300 elicited during a short memory test in male to female (MF) transsexuals, compared with that in healthy controls. The P300 component was evaluated during the anticipatory period of a short memory test in 13 MF transsexuals who had a gender reassignment operation, at least 3 years previously (mean time 17-6 years, range 3-31 years) and 26 healthy subjects (11 males and 15 females) matched for age and educational level. MF transsexuals exhibited significant reduction of P300 amplitude in the left frontal and temporoparietal areas in comparison to the control group. Furthermore, the group of transsexuals showed a significant delay of P300 latency in comparison to the controls, at the central frontal region. These findings point to significant psychophysiological alterations of distributed cortical circuits in MF transsexuals. These alterations may be critically related to the biological substrate of MF transsexualism.

Psychophysiological Features of Somatosensory Disorders in Victims of the Chernobyl Accident

Participants of the Chernobyl clean-up ( n = 145) teams exposed to radiation doses from 0.05 to 3.5 Gy who had for the first time complained of pathologic somatosensory sensations (ostealgic syndrome), 20 healthy subjects, and 50 veterans of the war in Afghanistan with posttraumatic stress disorder (PTSD) were examined by a neuropsychiatrist and presented with the MMPI test. Somatosensory evoked potentials (SSEPs) were recorded. Paresthesia and cenesthopathy were characteristic of the participants of the Chernobyl clean-up. Sensation disorders of the cerebral type, kinesthetic illusions, cenesthopathic hypochondriac disorders, and par- oxysmal psychosensory states predominated in this group of subjects. They differed significantly from the vet- erans with PTSD in markedly increased scores on MMPI scales (hypochondriasis, schizophrenia, pure hypo- chondriasis, pure schizophrenia, emotional exclusion, and perception oddity), which closely correlated with clinical somatosensory symptoms. In clean-up workers, somatosensory disorders were significantly associated with hypochondriac and schizophrenic-like symptoms. The latencies (LPs) of main SSEP components— N 20 , P 25 , N 140 , P 300 , and N 400 —were increased and their amplitudes decreased in subjects exposed to radiation. Their SSEPs had significant topographical deviations in the left temporoparietal area: the contralateral LPs were increased, whereas the contralateral amplitudes of the thalamocortical N 20 component and the cortical P 25 com- ponent were decreased as compared to normal values. Somatosensory disorders and hypochondriac and schizo- phrenic symptoms were significantly correlated with changes in the SSEPs. The decrease in the N 20 amplitude and increase in the P 25 latency in the left temporoparietal area were dose-dependent. The results suggest cere- bral rather than peripheral origin of ostealgic syndrome and other somatosensory disorders in the participants of the Chernobyl clean-up. These disorders are associated with radiation-induced dysfunction of the corticolim- bic structures of the left—dominant—hemisphere. It is suggested that somatosensory disorders in patients exposed to low doses of radiation can be considered as manifestations of chronic fatigue syndrome /fibromyalgia, whereas schizoform organic brain lesions manifest themselves after exposure to a radiation dose of 0.3-0.5 Gy.

Sequential histochemical studies of neuronal lipofuscin in human cerebral cortex from the first to the ninth decade of life

The typical and most consistent physico-histochemical properties of lipofuscin granules, such as autofluorescence, sudanophilia, acid-fastness, PAS-reactivity, and lectin reactivities for diverse saccharide moieties have been generally detected in tissue specimens of old humans and animals. The purpose of this study was, therefore, to explore possible sequential variations of each of these properties in cortical neurons of the left cerebral temporo-parietal areas from individuals dying from the first to the ninth decade. Autofluorescence was studied with an ad hoc equipped microscope, sudanophilia was evaluated by Oil-red-O (ORO) staining, acid-fastness by long Ziehl–Nielsen reagent, PAS reactivity by the periodic-acid-Schiff reagent before and after diastase treatment, and the saccharide moieties by the use of a commercial kit of seven different biotinylated lectins. In the specimen from a 5-year-old child, lipofuscin granules were detected in less than 5% of the cortical neurons, but these granules already showed golden-yellow autofluorescence, sudanophilia, acid-fastness and PAS-reactivity. From the second to the ninth decade of life, perikaryal lipofuscin granules were found in practically all cortical neurons with apparent agewise increases in the intensity of sudanophilia and PAS-reactivity, but with variable acid-fastness expression. Surprisingly, however, no saccharide residues were detected by lectin histochemistry before the fifth decade of life. First detected saccharide was mannose in specimens from the fifth decade of life, and at later decades acetyl galactosamine, sialic acid and lactose were also found. Although, the reasons for the absence of lipofuscin affinity for the seven lectins used in this study in the cortical neurons of young and middle-aged individuals are presently unknown, these unexpected findings suggested important evolutionary changes of biogenesis and composition of the age-pigment.

Event-related potentials and genetic risk for schizophrenia

Background: Event-related potentials (ERPs) during an auditory oddball task were investigated in patients with schizophrenia and in their healthy siblings to explore the question of whether abnormalities of two-dimensional topographic scalp-distribution of P300 amplitude and latency relate to genetic risk for schizophrenia. We also examined the P50, N100, and P200-waves, elicited during the same task. Methods: We investigated 42 schizophrenic patients, 62 of their healthy siblings, and 34 unrelated normal control subjects with a standard auditory oddball paradigm and 16 electroencephalogram electrodes. Amplitudes and latencies of the ERPs P50, N100, P200, and P300 were topographically analyzed. Results: In the patients, P300 amplitude was significantly decreased in the range of 54%–58% over the left parietotemporal area. Siblings did not show decreased P300 amplitudes when compared with normal subjects. P300 latencies were unchanged in both groups. No significant group differences were observed for the other event-related potentials. Conclusions: In line with previous studies, the P300 amplitude in schizophrenic patients was decreased over the left temporoparietal area; however, we found no evidence for a genetic trait effect in the event-related potential abnormality. Possible reasons for these largely negative findings are discussed.

Impaired cerebral glucose metabolism and cognitive functioning predict deterioration in mild cognitive impairment.

The objective of this study was to assess whether reduced glucose metabolism (rCMRGlu) and cognitive functioning could predict development of Alzheimer's disease (AD) in subjects with mild cognitive impairment (MCI). Twenty MCI patients underwent baseline and follow-up investigations of rCMRGlu, as measured by PET, and cognitive function measured by neuropsychological test assessments. Subjects were clinically followed up with an average interval of 36.5 months. Two groups were obtained after the second clinical assessment. Nine patients were diagnosed as AD and classified as progressive MCI (P-MCI), whereas 11 patients remained clinically stable and were classified as stable MCI (S-MCI). There were no differences in demographic variables or baseline MMSE between the two subgroups. Logistic regression indicated the two variables that most effectively predicted future development of AD were rCMRGlu from the left temporoparietal area and performance on the block design. These combined measures gave an optimal 90% correct classification rate, whereas only rCMRGlu or neuropsychology alone gave 75% and 65% correct classification, respectively. Measures of temporoparietal cerebral metabolism and visuospatial function may aid in predicting the evolution to AD for patients with MCI.

Left Temporal and Temporoparietal Brain Activity Depends on Depth of Word Encoding: A Magnetoencephalographic Study in Healthy Young Subjects

Using a 143-channel whole-head magnetoencephalograph (MEG) we recorded the temporal changes of brain activity from 26 healthy young subjects (14 females) related to shallow perceptual and deep semantic word encoding. During subsequent recognition tests, the subjects had to recognize the previously encoded words which were interspersed with new words. The resulting mean memory performances across all subjects clearly mirrored the different levels of encoding. The grand averaged event-related fields (ERFs) associated with perceptual and semantic word encoding differed significantly between 200 and 550 ms after stimulus onset mainly over left superior temporal and left superior parietal sensors. Semantic encoding elicited higher brain activity than perceptual encoding. Source localization procedures revealed that neural populations of the left temporal and temporoparietal brain areas showed different activity strengths across the whole group of subjects depending on depth of word encoding. We suggest that the higher brain activity associated with deep encoding as compared to shallow encoding was due to the involvement of more neural systems during the processing of visually presented words. Deep encoding required more energy than shallow encoding but for all that led to a better memory performance.

The magnocellular theory of developmental dyslexia.

Low literacy is termed 'developmental dyslexia' when reading is significantly behind that expected from the intelligence quotient (IQ) in the presence of other symptoms--incoordination, left-right confusions, poor sequencing--that characterize it as a neurological syndrome. 5-10% of children, particularly boys, are found to be dyslexic. Reading requires the acquisition of good orthographic skills for recognising the visual form of words which allows one to access their meaning directly. It also requires the development of good phonological skills for sounding out unfamiliar words using knowledge of letter sound conversion rules. In the dyslexic brain, temporoparietal language areas on the two sides are symmetrical without the normal left-sided advantage. Also brain 'warts' (ectopias) are found, particularly clustered round the left temporoparietal language areas. The visual magnocellular system is responsible for timing visual events when reading. It therefore signals any visual motion that occurs if unintended movements lead to images moving off the fovea ('retinal slip'). These signals are then used to bring the eyes back on target. Thus, sensitivity to visual motion seems to help determine how well orthographic skill can develop in both good and bad readers. In dyslexics, the development of the visual magnocellular system is impaired: development of the magnocellular layers of the dyslexic lateral geniculate nucleus (LGN) is abnormal; their motion sensitivity is reduced; many dyslexics show unsteady binocular fixation; hence poor visual localization, particularly on the left side (left neglect). Dyslexics' binocular instability and visual perceptual instability, therefore, can cause the letters they are trying to read to appear to move around and cross over each other. Hence, blanking one eye (monocular occlusion) can improve reading. Thus, good magnocellular function is essential for high motion sensitivity and stable binocular fixation, hence proper development of orthographic skills. Many dyslexics also have auditory/phonological problems. Distinguishing letter sounds depends on picking up the changes in sound frequency and amplitude that characterize them. Thus, high frequency (FM) and amplitude modulation (AM) sensitivity helps the development of good phonological skill, and low sensitivity impedes the acquisition of these skills. Thus dyslexics' sensitivity to FM and AM is significantly lower than that of good readers and this explains their problems with phonology. The cerebellum is the head ganglion of magnocellular systems; it contributes to binocular fixation and to inner speech for sounding out words, and it is clearly defective in dyslexics. Thus, there is evidence that most reading problems have a fundamental sensorimotor cause. But why do magnocellular systems fail to develop properly? There is a clear genetic basis for impaired development of magnocells throughout the brain. The best understood linkage is to the region of the Major Histocompatibility Complex (MHC) Class 1 on the short arm of chromosome 6 which helps to control the production of antibodies. The development of magnocells may be impaired by autoantibodies affecting the developing brain. Magnocells also need high amounts of polyunsaturated fatty acids to preserve the membrane flexibility that permits the rapid conformational changes of channel proteins which underlie their transient sensitivity. But the genes that underlie magnocellular weakness would not be so common unless there were compensating advantages to dyslexia. In developmental dyslexics there may be heightened development of parvocellular systems that underlie their holistic, artistic, 'seeing the whole picture' and entrepreneurial talents.

Vegetative-Vascular Dystonia and Osteoalgetic Syndrome or Chronic Fatigue Syndrome as a Characteristic After-Effect of Radioecological Disaster

The aim of this study was to determine whether the Chronic Fatigue Syndrome (CFS) definition could be applicable to the assessment of the medical aftermath of radioecological disasters and to investigate a possible psychophysiological basis of fatigue in Chernobyl accident survivors. One hundred randomly selected clean-up workers of the Chernobyl accident who presented with complains of fatigue were examined neuropsychiatrically using MMPI profiles, Quantitative Electroencephalography (QEEG) and Somatosensory evoked potentials (SSEP). Twenty-six percent of them met the CFS diagnostic criteria. Their absorbed radiation doses were less than 0.3 Sv, an exposure level that is not expected to produce a clear deterministic radiation effect. Clinical symptomatology included persistent fatigue, odd skin sensations, bizarre feelings in bones, muscles and joints, irritability, headache, vertigo, pain in the chest area, emotional lability, irritability, lack of concentration and memory, cognitive deterioration, depression signs and sleep disorders. Liquidators with CFS had the characteristic MMPI profile with increased hypochondria, depression, clear hypochondria, schizophrenia, hysteria, psychasthenia, and bizarre sensory perception scales. Spectral analysis of QEEG showed lateralised (left-sided) increase of θ-power (P < 0.001) and lateralised (left-sided) decrease of a-power (P < 0.001) and lateralised (left-sided) increase of β-power (P < 0.01). SSEP were characterized by increased latencies and decreased amplitudes. SSEP significantly differed by topographic abnormalities in the left temporoparietal area in liquidators with CFS. Associations between schizophrenia-like, hypochondriac and psychasthenic psycho-pathology and an increase of latency of SSEP P300 and N400 in liquidators with CFS were revealed. Thus, “Vegetative-Vascular Dystonia” and “Osteoalgetic Syndrome” cases following exposure to ionizing radiation as a result of the Chernobyl accident can be classified as CFS cases. The psychophysiological basis of fatigue in liquidators consists of dysfunction of the cortico-limbical structures of the left, dominating, hemisphere. CFS is one of the most important consequences of radio-ecological disaster, which results from an interaction of different hazardous environmental factors.

A marker for differentiation of capabilities for processing of musical harmonies as detected by magnetoencephalography in musicians

This investigation was designed to study the characteristics of a marker for harmonic processing and to test whether it could be used for differentiating harmonic processing capabilities. The first three chords of an ordinary musical cadenca were presented to the left ear to establish a harmonic context followed by a harmonic or non-harmonic target tone. Cadencas were presented rapidly and randomly in different keys to render the task difficult. Results showed a specific P3m (magnetic P300) effect to the non-harmonic targets which was only visible in subjects with low target recognition errors. Low resolution electro-magnetic tomography current density maps showed P3m sources in the right temporoparietal, left temporoparietal and frontocentral brain areas with right temporoparietal sources being strongest and most reliable. The results offer new possibilities to selectively study harmonic variables in music processing.

Behavioral and Psychological Symptoms in Alzheimer’s Disease

Fundamental and therapeutic research in Alzheimer’s disease (AD) focused for a long time exclusively on cognitive aspects. However, AD also frequently involves complex disorders of affect and behavior, which are currently grouped under the heading ‘behavioral and psychological signs and symptoms of dementia’ (BPSSD). Several rating tools have been developed over the years on the basis of a variety of source data. Some are derived from psychiatric practise or have specifically been developed for dementia, such as the Neuropsychiatric Inventory (NPI). In this study we prospectively used the NPI to examine BPSSD. Sixty-three French patients (mean age 74.7 years, SD 7.9) with a Mini-Mental State Examination (MMSE) score higher than 10 were examined. BPPSD were detected by NPI in 95.2% of the patients. Anxiety was the most common abnormality (65.1%), followed by apathy and dysphoria (58.7%). The highest frequency × severity NPI score was observed for apathy. In order to identify the relationship between regional cerebral perfusion and apathy, 20 of these AD patients underwent a technetium-99m-bicisate SPECT protocol within the same week as the NPI evaluation. The mean age of this population was 74.4 years (SD 5.3) and the mean MMSE score was 21 (SD 4.1). The apathy NPI score was correlated with right cingulate deficit whereas the highest correlation for the MMSE was with the left temporoparietal area. This stresses the interest to focus on SPECT imaging of AD patients not only in the posterior areas.

Clinical and quantitative EEG studies of mania

Background: Earlier EEG studies reported essentially normal findings during acute manic episodes but some atypical EEG characteristics and distinctions between familial and sporadic cases were described. Recently quantitative EEG (qEEG) studies differentiating mania from schizophrenia and depression have been published. Methods: Clinical EEGs were obtained in 202 patients hospitalized for acute mania. EEGs were repeated in 75 patients rehospitalized for subsequent manic attacks. Quantitative EEGs were recorded in 37 patients who were able to cooperate after drug washout and again on completion of randomly assigned pharmacotherapy. Results: Normal EEGs were obtained in most patients. Moderately abnormal EEGs in 16% were significantly associated with absent family histories of affective disorder. Left sided abnormalities were more common than right. “Small sharp spikes” and “microsleep” were encountered in 17% and 10% respectively of patients who drowsed. EEG findings during subsequent episodes did not suggest increasing CNS vulnerability. qEEGs showed significant differences between each of the therapeutic agents compared-lithium, carbamazepine, and lithium combined with carbamazepine, haloperidol or risperidone. Nonresponders at baseline had significantly more diffuse theta activity than responders. During pharmacotherapy nonresponders had higher amplitudes in the left temporoparietal areas. Limitation: Clinical EEG findings confirmed previous reports but did not contain original observations. Applications of qEEG were limited by requirements for patient cooperation.

A clue in the duodenum

A 60-year-old man was admitted to hospital in July, 1990, with anorexia, lethargy, and confusion. 12 months previously he had injured his left temporoparietal area and made an uneventful recovery. He did not have any specific gastrointestinal or rheumatological symptoms. On examination he was febrile (37.8–38.2°C). There was no evidence of lymphadenopathy. His liver, kidneys, and spleen were not enlarged. The only laboratory abnormalities were leucocytosis (15×109/L, 85% polymorphonuclear leucoytes) and thrombocytosis (550×109/L).

Human Brain Language Areas Identified by Functional Magnetic Resonance Imaging

Functional magnetic resonance imaging (FMRI) was used to identify candidate language processing areas in the intact human brain. Language was defined broadly to include both phonological and lexical-semantic functions and to exclude sensory, motor, and general executive functions. The language activation task required phonetic and semantic analysis of aurally presented words and was compared with a control task involving perceptual analysis of nonlinguistic sounds. Functional maps of the entire brain were obtained from 30 right-handed subjects. These maps were averaged in standard stereotaxic space to produce a robust "average activation map" that proved reliable in a split-half analysis. As predicted from classical models of language organization based on lesion data, cortical activation associated with language processing was strongly lateralized to the left cerebral hemisphere and involved a network of regions in the frontal, temporal, and parietal lobes. Less consistent with classical models were (1) the existence of left hemisphere temporoparietal language areas outside the traditional "Wernicke area," namely, in the middle temporal, inferior temporal, fusiform, and angular gyri; (2) extensive left prefrontal language areas outside the classical "Broca area"; and (3) clear participation of these left frontal areas in a task emphasizing "receptive" language functions. Although partly in conflict with the classical model of language localization, these findings are generally compatible with reported lesion data and provide additional support for ongoing efforts to refine and extend the classical model.

Cavitating Lung Lesions and a Cerebral Mass

A 67-year-old retired marine engineer presented with a 3-week history of increasing tiredness and dyspnea without cough, sputum, or chest pain. Three months previously, he had been diagnosed as having an inoperable glioma of the left temporoparietal area for which he had received palliative treatment with radiotherapy and dexamethasone. He had had Addison's disease for 40 years, insulin-dependent diabetes mellitus for 12 years, and bilateral femoral vein thrombi 2 years previously. He had never smoked.

The Time Course of Syntactic Activation During Language Processing: A Model Based on Neuropsychological and Neurophysiological Data

This paper presents a model describing the temporal and neurotopological structure of syntactic processes during comprehension. It postulates three distinct phases of language comprehension, two of which are primarily syntactic in nature. During the first phase the parser assigns the initial syntactic structure on the basis of word category information. These early structural processes are assumed to be subserved by the anterior parts of the left hemisphere, as event-related brain potentials show this area to be maximally activated when phrase structure violations are processed and as circumscribed lesions in this area lead to an impairment of the on-line structural assignment. During the second phase lexical-semantic and verb-argument structure information is processed. This phase is neurophysiologically manifest in a negative component in the event-related brain potential around 400 ms after stimulus onset which is distributed over the left and right temporo-parietal areas when lexical-semantic information is processed and over left anterior areas when verb-argument structure information is processed. During the third phase the parser tries to map the initial syntactic structure onto the available lexical-semantic and verb-argument structure information. In case of an unsuccessful match between the two types of information reanalyses may become necessary. These processes of structural reanalysis are correlated with a centroparietally distributed late positive component in the event-related brain potential. The different temporal and topographical patterns of the event-related brain potential. as well as some aspects of aphasics′ comprehension behavior are taken to support the view that these different processing phases are distinct and that the left anterior cortex, in particular, is responsible for the on-line assignment of syntactic structure.

Affinities between both the syndromal structure and neurophysiology of the adolescent schizotypal personality and adult schizophrenia

This investigation was designed to study the characteristics of a marker for harmonic processing and to test whether it could be used for differentiating harmonic processing capabilities. The first three chords of an ordinary musical cadenca were presented to the left ear to establish a harmonic context followed by a harmonic or non-harmonic target tone. Cadencas were presented rapidly and randomly in different keys to render the task difficult. Results showed a specific P3m (magnetic P300) effect to the non-harmonic targets which was only visible in subjects with low target recognition errors. Low resolution electro-magnetic tomography current density maps showed P3m sources in the right temporoparietal, left temporoparietal and frontocentral brain areas with right temporoparietal sources being strongest and most reliable. The results offer new possibilities to selectively study harmonic variables in music processing.