Dreaming and unilateral brain lesions: A multiple lesion case analysis.

Lesions causing cessation of dreaming are thought to be more frequently left hemispheric than right hemispheric. However, reports of this phenomenon have not excluded epileptic cases and have not reported handedness, etiology of the lesion, lesion location, comorbidity, gender, age, and so forth, on a case-by-case basis. Some authors were also concerned about aphasia being a cause of dream loss and its lateralization, but they never measured its impact statistically. The present investigation reviews cases of post lesion dream cessation that answered to strict criteria for testing hemispheric lateralization and the effect of aphasia on it. In the 31 subjects, left hemisphere lesions were significantly more frequent than right, as predicted, but the left hemisphere lesions were very often associated with aphasia. Nonaphasic cases of total dream loss had lesions equally often in the right and in the left hemisphere. It is proposed that aphasia deprives patients of a second dream-encoding system, which is important enough to induce amnesia of dream occurrence. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Aphasia and Alalia from the Perspective of Natal’ya N. Traugott’s Studies on Higher Cognitive Processes

The paper describes one of the central areas of research of Professor Natal’ya N. Traugott, a famous Russian neurophysiologist. In particular, Prof. Traugott identified the general neurophysiological mechanisms responsible for speech disorders in children with alalia and in adults with aphasia caused by focal brain lesions. Physiological experiments showed that both sensory alalia in children and sensory aphasia in adults are associated with the deficiency of auditory analyzer; such deficiency leads to disorders in the formation of conditional reactions to sounds and sound complexes. Moreover, a general development pattern was identified in the ontogeny of interaction of signal systems and in the degradation of such interaction caused by the lesions of particular analyzers. This finding of Prof. Traugott is very important in both theory of cerebral speech mechanisms and speech therapy practices aimed at speech system development and rehabilitation following cerebral dysfunctions.     

Neuropsychological Analysis of The Predicative Structure of Utterances

A few years ago, one of the authors (A. R. Luriya, 1947, 1948, 1962, 1963) described a special form of speech disorder, which occurs as a result of local injury to the posterior frontal region of the left cerebral hemisphere, that he called dynamic aphasia.     

Vascular lesions of the thalamus on the dominant and nondominant side.

A clinicopathological study was done on 87 subjects with VPL lesions due to vascular pathology, with special reference to the difference of clinical manifestations between the right and left sides. Thalamic pain was far more common in VPL lesions on the right side. The responsible lesions for thalamic pain were observed in lesions of VPL and VPL extending to the internal capsule, while in the lesions of the VPL extending to the centrum medianum, central pain was rare. 2 cases with aphasia due to thalamic hemorrhage were found in this series, both in the dominant hemisphere. It is suggested that the thalamus in the dominant hemisphere may be related to speech and in the nondominant to a central pain mechanism.     

Word retrieval learning modulates right frontal cortex in patients with left frontal damage

Previous studies have suggested that recovery or compensation of language function after a lesion in the left hemisphere may depend on mechanisms in the right hemisphere. However, a direct relationship between performance and right hemisphere activity has not been established. Here, we show that patients with left frontal lesions and partially recovered aphasia learn, at a normal rate, a novel word retrieval task that requires the damaged cortex. Verbal learning is accompanied by specific response decrements in right frontal and right occipital cortex, strongly supporting the compensatory role of the right hemisphere. Furthermore, responses in left occipital cortex are abnormal and not modulated by practice. These findings indicate that frontal cortex is a source of top-down signals during learning.     

The contribution of the cerebellum to mental and social functions in developmental age

Here we present the data concerning the intellectual, language, and frontal performances of 24 children who have undergone surgery because of cerebellar hemisphere or vermis tumors and one girl with viral cerebellitis. The children with right cerebellar tumors presented auditory sequential memory and language processing disturbances; those with left cerebellar tumors showed deficits in spatial tests and visual sequential memory. The girl with cerebellitis showed a complex neuropsychological picture with impairment in processing language and general sequential functions. Lesions of the vermis lead to two pictures: (1) a postsurgical mutism that could be subdivided into speech disorders (even to the extent of anarthria) and true language disturbances similar to frontal aphasia and (2) behavioral disturbances ranging from irritability to a truly autistic response. These data seem to support the recently attributed role of the cerebellum as a modulator of the superior mental and social functions.     

Auditory and cognitive deficits associated with acquired amusia after stroke: a magnetoencephalography and neuropsychological follow-up study

Acquired amusia is a common disorder after damage to the middle cerebral artery (MCA) territory. However, its neurocognitive mechanisms, especially the relative contribution of perceptual and cognitive factors, are still unclear. We studied cognitive and auditory processing in the amusic brain by performing neuropsychological testing as well as magnetoencephalography (MEG) measurements of frequency and duration discrimination using magnetic mismatch negativity (MMNm) recordings. Fifty-three patients with a left (n = 24) or right (n = 29) hemisphere MCA stroke (MRI verified) were investigated 1 week, 3 months, and 6 months after the stroke. Amusia was evaluated using the Montreal Battery of Evaluation of Amusia (MBEA). We found that amusia caused by right hemisphere damage (RHD), especially to temporal and frontal areas, was more severe than amusia caused by left hemisphere damage (LHD). Furthermore, the severity of amusia was found to correlate with weaker frequency MMNm responses only in amusic RHD patients. Additionally, within the RHD subgroup, the amusic patients who had damage to the auditory cortex (AC) showed worse recovery on the MBEA as well as weaker MMNm responses throughout the 6-month follow-up than the non-amusic patients or the amusic patients without AC damage. Furthermore, the amusic patients both with and without AC damage performed worse than the non-amusic patients on tests of working memory, attention, and cognitive flexibility. These findings suggest domain-general cognitive deficits to be the primary mechanism underlying amusia without AC damage whereas amusia with AC damage is associated with both auditory and cognitive deficits.     

On the Interrelationship of Speech Functioning and Manual Motor Activity in Aphasia

Clinicians, physiologists, and psychologists are familiar with cases of simultaneous disturbance of various functions in localized cerebral lesions. These phenomena have been studied and described repeatedly, but continue to be of substantial interest, as analysis of them may make a contribution to the study of localization of functions in the cerebral cortex, substitution and restoration of functions, and the nature of their interrelationships. Our attention was attracted by a case of simultaneous disturbance of motor function and the power of speech in a lesion of the left (dominant) hemisphere. We began by investigating motor functions in aphasia and in the normal state, with a view to subsequent comparison of the motor and verbal functions in the normal state and in aphasia.     

Neuropsychophysiological correlates of reactive depression

To justify neurophysiological correlates of depressive disorders, the spetral parameters of EEG, peak latencies of the “late” components of auditory cognitive evoked potentials, and latencies of sensorimotor reactions in middle age and elderly patients (aged 53–72 years) during therapy of prolonged psychogenic depressive reaction (F43.21 according to ICD-10) have been studied. Initial depression severity was associated to the EEG signs of decreased functional state of the anterior areas of the left hemisphere and increased activation of the right hemisphere (especially, its temporal areas). Pronounced improvement of clinical state under the affect of psychopharmacotherapy was accompanied by acceleration of the sensorimotor reactions, a decrease in peak latencies of the “late” components (P2, N2, and P3) of auditory cognitive evoked potentials and associated with the EEG signs of improvement of functional state of the posterior areas of the brain, an enforcement of inhibitory processes in the right hemisphere (especially, in its frontal, central, and temporal areas) and more pronounced activation of frontal areas of the left hemisphere. The data are in good agreement with the concept on the systemic character of impairments of brain functioning in depression, as well as on the preferential role of the left hemisphere in control of positive emotions and the right one, of negative emotions.     

Rapid effects of hearing song on catecholaminergic activity in the songbird auditory pathway

Catecholaminergic (CA) neurons innervate sensory areas and affect the processing of sensory signals. For example, in birds, CA fibers innervate the auditory pathway at each level, including the midbrain, thalamus, and forebrain. We have shown previously that in female European starlings, CA activity in the auditory forebrain can be enhanced by exposure to attractive male song for one week. It is not known, however, whether hearing song can initiate that activity more rapidly. Here, we exposed estrogen-primed, female white-throated sparrows to conspecific male song and looked for evidence of rapid synthesis of catecholamines in auditory areas. In one hemisphere of the brain, we used immunohistochemistry to detect the phosphorylation of tyrosine hydroxylase (TH), a rate-limiting enzyme in the CA synthetic pathway. We found that immunoreactivity for TH phosphorylated at serine 40 increased dramatically in the auditory forebrain, but not the auditory thalamus and midbrain, after 15 min of song exposure. In the other hemisphere, we used high pressure liquid chromatography to measure catecholamines and their metabolites. We found that two dopamine metabolites, dihydroxyphenylacetic acid and homovanillic acid, increased in the auditory forebrain but not the auditory midbrain after 30 min of exposure to conspecific song. Our results are consistent with the hypothesis that exposure to a behaviorally relevant auditory stimulus rapidly induces CA activity, which may play a role in auditory responses.     

Improvement of Speech Function in Patients with Aphasia: The Right Hemisphere,an Enemy or a Friend?

The purpose of our research is to investigate interhemispheric language functional reorganization in patients with gliomas of the left hemisphere using functional magnetic resonance tomography (fMRI) in comparison with the dynamics of speech disorders. A total of 20 patients with a glioma in the left hemisphere underwent fMRI examination and Luria’s neuropsychological testing. The age of patients varied from 26 to 67 years; the mean age was 40 years (median, interquartile range; 13 women and 7 men). The glioma was located in the frontal lobe (12 patients) 34.50–49.75 years; or in the temporal lobe (8 patients). All patients underwent both fMRI scanning and neuropsychological testing on the same day before the surgery and then 3–10 days and 3, 5–7, 12 months after tumor surgery. The handedness was determined by using self-assessment and the Annett Hand Preference Questionnaire. Almost all the subjects were right-handed, and one was ambidexter. On the basis of the analysis of fMRI data in dynamics, all subjects were divided into two groups: (1) patients with no signs of activation of the right hemisphere homologues of Broca’s and Wernicke’s areas (even in 4 patients with severe aphasia) during the follow-up period (at least one year), and (2) patients with signs of activation in the right-sided Broca’s and Wernicke’s areas, which were found in at least several tests (16 patients; 3 of them had normal speech function during the whole follow-up period). We conclude that the lack of consistency between the presence/absence of aphasia and the activation of homologous speech areas in the right hemisphere in fMRI results from individual differences in the involvement of the right hemisphere in speech processes. Thus, we should be very cautious about the hypothesis of reciprocal relationships of the hemispheres in speech function and the use of this hypothesis in speech rehabilitation.     

Some effects of aphasic lesions on order perception.

Twenty-four aphasic, nine brain-damaged, and eight non-brain-damaged patients were tested for their ability to associate odors with visual targets. The results of the experiment show that lesions producing aphasia interfere with the ability to match an odor to a directly corresponding visual target. As aphasics with anterior and posterior lesions performed at similar levels in this task, it was not possible to conclude that the observed deficits were specifically related to temporal lobe functions. The severity of the deficit was greater for more massively lesioned aphasics. The exact nature of the deficit was not clear, but review of the literature and differential results obtained for the two experimental tasks suggest that aphasic lesions may interefere with odor identification.     

Hemispheric specialization in dogs for processing different acoustic stimuli

Considerable experimental evidence shows that functional cerebral asymmetries are widespread in animals. Activity of the right cerebral hemisphere has been associated with responses to novel stimuli and the expression of intense emotions, such as aggression, escape behaviour and fear. The left hemisphere uses learned patterns and responds to familiar stimuli. Although such lateralization has been studied mainly for visual responses, there is evidence in primates that auditory perception is lateralized and that vocal communication depends on differential processing by the hemispheres. The aim of the present work was to investigate whether dogs use different hemispheres to process different acoustic stimuli by presenting them with playbacks of a thunderstorm and their species-typical vocalizations. The results revealed that dogs usually process their species-typical vocalizations using the left hemisphere and the thunderstorm sounds using the right hemisphere. Nevertheless, conspecific vocalizations are not always processed by the left hemisphere, since the right hemisphere is used for processing vocalizations when they elicit intense emotion, including fear. These findings suggest that the specialisation of the left hemisphere for intraspecific communication is more ancient that previously thought, and so is specialisation of the right hemisphere for intense emotions.     

The neural basis of body form and body action agnosia

Visual analysis of faces and nonfacial body stimuli brings about neural activity in different cortical areas. Moreover, processing body form and body action relies on distinct neural substrates. Although brain lesion studies show specific face processing deficits, neuropsychological evidence for defective recognition of nonfacial body parts is lacking. By combining psychophysics studies with lesion-mapping techniques, we found that lesions of ventromedial, occipitotemporal areas induce face and body recognition deficits while lesions involving extrastriate body area seem causatively associated with impaired recognition of body but not of face and object stimuli. We also found that body form and body action recognition deficits can be double dissociated and are causatively associated with lesions to extrastriate body area and ventral premotor cortex, respectively. Our study reports two category-specific visual deficits, called body form and body action agnosia, and highlights their neural underpinnings.     

Auditory and Visual Interhemispheric Communication in Musicians and Non-Musicians

The corpus callosum (CC) is a brain structure composed of axon fibres linking the right and left hemispheres. Musical training is associated with larger midsagittal cross-sectional area of the CC, suggesting that interhemispheric communication may be faster in musicians. Here we compared interhemispheric transmission times (ITTs) for musicians and non-musicians. ITT was measured by comparing simple reaction times to stimuli presented to the same hemisphere that controlled a button-press response (uncrossed reaction time), or to the contralateral hemisphere (crossed reaction time). Both visual and auditory stimuli were tested. We predicted that the crossed-uncrossed difference (CUD) for musicians would be smaller than for non-musicians as a result of faster interhemispheric transfer times. We did not expect a difference in CUDs between the visual and auditory modalities for either musicians or non-musicians, as previous work indicates that interhemispheric transfer may happen through the genu of the CC, which contains motor fibres rather than sensory fibres. There were no significant differences in CUDs between musicians and non-musicians. However, auditory CUDs were significantly smaller than visual CUDs. Although this auditory-visual difference was larger in musicians than non-musicians, the interaction between modality and musical training was not significant. Therefore, although musical training does not significantly affect ITT, the crossing of auditory information between hemispheres appears to be faster than visual information, perhaps because subcortical pathways play a greater role for auditory interhemispheric transfer.     

Dysphagia in acute stroke.

A prospective study was undertaken to define the incidence, duration, and consequences of dysphagia in an unselected group of 91 consecutive patients who had suffered acute stroke. The site of the present lesion and of any previous stroke was determined clinically and was confirmed by computed tomography of the brain or necropsy in 40 cases. Of 41 patients who had dysphagia on admission, 37 had had a stroke in one cerebral hemisphere. Only seven patients showed evidence of lesions in both hemispheres. Nineteen of 22 patients who survived a stroke in a hemisphere regained their ability to swallow within 14 days. Dysphagia in patients who had had a stroke in a cerebral hemisphere was associated in this study with a higher incidence of chest infections, dehydration, and death.     

Model approach to neurological variants of visuo-spatial neglect

Neglect is a neurological disorder of spatial attention with reduced awareness of visual stimuli in the hemifield contralateral to an acute temporo-parietal lesion mainly of the right hemisphere. There is a close association of multisensory orientation centers (MSO) and vestibular tonus imbalance. A lesion of the dominant right MSO causes a left-sided neglect due to a lack of ipsilateral activation of the visual cortex, which is further enhanced by increasing inhibition from the contralateral visual cortex. The nondominant MSO in the left hemisphere might be involved in the manifestation of the less frequent and more transient right-sided neglect and in the plastic mechanisms of gradual recovery from left-sided neglect or extinction. There is evidence that a vestibular tonus inbalance due to peripheral or central vestibular pathway lesions may also induce a neglect. In a first model approach using an attractor network and assuming that there is only one MSO in the right hemisphere, it is possible to simulate attentional shifts into a visual hemifield and to induce a neglect. The neural network model consists of four layers of neurons: retina, MSO, visual cortex V1, and superior colliculus. The superior colliculus layer is modeled as a recurrent attractor network with one inhibitory interneuron and synaptic weights chosen to implement a winner-take-all network that centers the hill of activity on the strongest input. We are well aware of the simplifications used in the conceptual drawings and the computational model, but nevertheless hope that they will serve as an inspiration for further modeling and clinical studies.     

Higher density of mental capacities in the left cerebral hemisphere of man: a quantitative investigation in children with localized cerebral lesions

51 children with localized cerebral lesions were investigated with the British Ability Scales, Wechsler test, Porteus Mazes, Conners Teacher Rating Scale, and computerized tomography. The extent of the lesions was quantitatively determined. The IQ was 10 points lower in the left hemispheric lesions, although the right hemispheric lesions were larger. When corrected for size of lesions, the IQ is 17 points higher (p less than 0.05) in children with right than with left hemispheric early lesions. The children with left hemispheric lesions had also significantly more behavioural problems (Conners Scale). Children with bilateral lesions had 15 points lower IQ than those with unilateral lesions, although from the slightly larger extent one could expect only 3 points difference. There was no influence of hemiparesis or of epilepsy of the IQ independent of the extent of lesion. There was more plasticity of the hemisphere than of the lobes as shown by Wisconsin Card Sorting data. The higher density of mental capacities in the left cerebral hemisphere of man is explained by more efficient programs, and more dense packing of functions due to more training of the left cerebral hemisphere.     

Absence of Auditory M100 Source Asymmetry in Schizophrenia and Bipolar Disorder: A MEG Study

Background

Whether schizophrenia and bipolar disorder are the clinical outcomes of discrete or shared causative processes is much debated in psychiatry. Several studies have demonstrated anomalous structural and functional superior temporal gyrus (STG) symmetries in schizophrenia. We examined bipolar patients to determine if they also have altered STG asymmetry.

Methods

Whole-head magnetoencephalography (MEG) recordings of auditory evoked fields were obtained for 20 subjects with schizophrenia, 20 with bipolar disorder, and 20 control subjects. Neural generators of the M100 auditory response were modeled using a single equivalent current dipole for each hemisphere. The source location of the M100 response was used as a measure of functional STG asymmetry.

Results

Control subjects showed the typical M100 asymmetrical pattern with more anterior sources in the right STG. In contrast, both schizophrenia and bipolar disorder patients displayed a symmetrical M100 source pattern. There was no significant difference in the M100 latency and strength in bilateral hemispheres within three groups.

Conclusions

Our results indicate that disturbed asymmetry of temporal lobe function may reflect a common deviance present in schizophrenia and bipolar disorder, suggesting the two disorders might share etiological and pathophysiological factors.