scholarly journals Cortical Effects of Shifting Letter Position in Letter Strings of Varying Length

2003 ◽  
Vol 15 (5) ◽  
pp. 731-746 ◽  
Author(s):  
Piers Cornelissen ◽  
Antti Tarkiainen ◽  
Päivi Helenius ◽  
Riitta Salmelin
Keyword(s):  
Word Length ◽  
Right Hemisphere ◽  
Word Reading ◽  
Temporal Dynamics ◽  
Temporal Cortex ◽  
Letter Position ◽  
Opposite Pattern ◽  
Spatio Temporal ◽  
Single Word Reading ◽  
The Right

Neuroimaging and lesion studies suggest that occipitotemporal brain areas play a necessary role in recognizing a wide variety of objects, be they faces, letters, numbers, or household items. However, many questions remain regarding the details of exactly what kinds of information are processed by the occipito-temporal cortex. Here, we address this question with respect to reading. Ten healthy adult subjects performed a single word reading task. We used whole-head magnetoencephalography to measure the spatio-temporal dynamics of brain responses, and investigated their sensitivity to: (1) lexicality (defined here as the difference between words and consonant strings), (2) word length, and (3) variation in letter position. Analysis revealed that midline occipital activity around 100 msec, consistent with low-level visual feature analysis, was insensitive to lexicality and variation in letter position, but was slightly affected by string length. Bilateral occipito-temporal activations around 150 msec were insensitive to lexicality and reacted to word length only in the timing (and not strength) of activation. However, vertical shifts in letter position revealed a hemispheric imbalance: The right hemisphere activation increased with the shifts, whereas the opposite pattern was evident in the left hemisphere. The results are discussed in the light of Caramazza and Hillis's (1990) model of early reading.

scholarly journals Brain Activation During Reading in Deep Dyslexia: An MEG Study

2000 ◽  
Vol 12 (4) ◽  
pp. 622-634 ◽  
Author(s):  
Matti Laine ◽  
Riitta Salmelin ◽  
Päivi Helenius ◽  
Reijo Marttila
Keyword(s):  
Semantic Processing ◽  
Semantic Analysis ◽  
Right Hemisphere ◽  
Word Reading ◽  
Brain Activity ◽  
Temporal Cortex ◽  
Single Word ◽  
Lexical Semantic ◽  
Deep Dyslexia ◽  
Single Word Reading

Magnetoencephalographic (MEG) changes in cortical activity were studied in a chronic Finnish-speaking deep dyslexic patient during single-word and sentence reading. It has been hypothesized that in deep dyslexia, written word recognition and its lexical-semantic analysis are subserved by the intact right hemisphere. However, in our patient, as well as in most nonimpaired readers, lexical-semantic processing as measured by sentence-final semantic-incongruency detection was related to the left superior-temporal cortex activation. Activations around this same cortical area could be identified in single-word reading as well. Another factor relevant to deep dyslexic reading, the morphological complexity of the presented words, was also studied. The effect of morphology was observed only during the preparation for oral output. By performing repeated recordings 1 year apart, we were able to document significant variability in both the spontaneous activity and the evoked responses in the lesioned left hemisphere even though at the behavioural level, the patient's performance was stable. The observed variability emphasizes the importance of estimating consistency of brain activity both within and between measurements in brain-damaged individuals.

Scanning the stammering brain

2000 ◽  
Vol 17 (4) ◽  
pp. 140-142 ◽  
Author(s):  
Caoimhghín S Breathnach
Keyword(s):  
Public Speaking ◽  
Right Hemisphere ◽  
Word Reading ◽  
Motor Preparation ◽  
Single Word ◽  
Regional Cerebral Blood ◽  
Self Monitoring ◽  
Single Word Reading ◽  
The Right ◽  
Abnormal Motor

AbstractStammering (or stuttering) may be defined as an impairment of continuous utterance. Developmental stammering, regardless of country or language, affects one per cent of adult populations. Exacerbation by the stress of adult conversation or public speaking contrasts sharply with normal flow during singing, acting or conversation with children. Alterations in regional cerebral blood flow suggest that there are underlying differences in sensorimotor function in developmental stammerers whose symptoms commonly appear during the period of intensive language acquisition around the third and fourth year. Emotional tensions may exacerbate the disturbance, but equally psychological growth is adversely affected by the handicap. Abnormal motor control is confirmed by the exaggerated activity in the right hemisphere. The normal sequence of articulatory programming and motor preparation for single word reading is reversed. Absence of activation over the left auditory cortex supports the notion of impaired or diminished auditory feedback in the self-monitoring of speech seen in normal brains. Subcortical abnormalities are a feature of both developmental and acquired stammering.

scholarly journals Localization of Syntactic and Semantic Brain Responses using Magnetoencephalography

2007 ◽  
Vol 19 (7) ◽  
pp. 1193-1205 ◽  
Author(s):  
Elisabet Service ◽  
Päivi Helenius ◽  
Sini Maury ◽  
Riitta Salmelin
Keyword(s):  
Temporal Lobe ◽  
Semantic Processing ◽  
Sentence Comprehension ◽  
Right Hemisphere ◽  
Temporal Cortex ◽  
Word Class ◽  
Sentence Reading ◽  
Word Onset ◽  
Semantic Errors ◽  
The Right

Electrophysiological methods have been used to study the temporal sequence of syntactic and semantic processing during sentence comprehension. Two responses associated with syntactic violations are the left anterior negativity (LAN) and the P600. A response to semantic violation is the N400. Although the sources of the N400 response have been identified in the left (and right) temporal lobe, the neural signatures of the LAN and P600 have not been revealed. The present study used magnetoencephalography to localize sources of syntactic and semantic activation in Finnish sentence reading. Participants were presented with sentences that ended in normally inf lected nouns, nouns in an unacceptable case, verbs instead of nouns, or nouns that were correctly inflected but made no sense in the context. Around 400 msec, semantically anomalous last words evoked strong activation in the left superior temporal lobe with significant activation also for word class errors (N400). Weaker activation was seen for the semantic errors in the right hemisphere. Later, 600-800 msec after word onset, the strongest activation was seen to word class and morphosyntactic errors (P600). Activation was significantly weaker to semantically anomalous and correct words. The P600 syntactic activation was localized to bilateral sources in the temporal lobe, posterior to the N400 sources. The results suggest that the same general region of the superior temporal cortex gives rise to both LAN and N400 with bilateral reactivity to semantic manipulation and a left hemisphere effect to syntactic manipulation. The bilateral P600 response was sensitive to syntactic but not semantic factors.

The Role of the Right Posterior Parietal Cortex in Letter Migration between Words

2015 ◽  
Vol 27 (2) ◽  
pp. 377-386 ◽  
Author(s):  
Dario Cazzoli ◽  
René M. Müri ◽  
Christopher Kennard ◽  
Clive R. Rosenthal
Keyword(s):  
Parietal Cortex ◽  
Posterior Parietal Cortex ◽  
Word Reading ◽  
Letter Position ◽  
Control Group ◽  
Neural Basis ◽  
Specific Effects ◽  
Letter Position Coding ◽  
Posterior Parietal ◽  
The Right

When briefly presented with pairs of words, skilled readers can sometimes report words with migrated letters (e.g., they report hunt when presented with the words hint and hurt). This and other letter migration phenomena have been often used to investigate factors that influence reading such as letter position coding. However, the neural basis of letter migration is poorly understood. Previous evidence has implicated the right posterior parietal cortex (PPC) in processing visuospatial attributes and lexical properties during word reading. The aim of this study was to assess this putative role by combining an inhibitory TMS protocol with a letter migration paradigm, which was designed to examine the contributions of visuospatial attributes and lexical factors. Temporary interference with the right PPC led to three specific effects on letter migration. First, the number of letter migrations was significantly increased only in the group with active stimulation (vs. a sham stimulation group or a control group without stimulation), and there was no significant effect on other error types. Second, this effect occurred only when letter migration could result in a meaningful word (migration vs. control context). Third, the effect of active stimulation on the number of letter migrations was lateralized to target words presented on the left. Our study thus demonstrates that the right PPC plays a specific and causal role in the phenomenon of letter migration. The nature of this role cannot be explained solely in terms of visuospatial attention, rather it involves an interplay between visuospatial attentional and word reading-specific factors.

A Functional Neuroimaging Description of Two Deep Dyslexic Patients

1998 ◽  
Vol 10 (3) ◽  
pp. 303-315 ◽  
Author(s):  
C. J. Price ◽  
D. Howard ◽  
K. Patterson ◽  
E. A. Warburton ◽  
K. J. Friston ◽  
...  
Keyword(s):  
Left Hemisphere ◽  
Word Processing ◽  
Right Hemisphere ◽  
Temporal Cortex ◽  
Inferior Temporal Cortex ◽  
Broca's Area ◽  
Enhanced Activity ◽  
Left Posterior ◽  
Deep Dyslexia ◽  
The Right

Deep dyslexia is a striking reading disorder that results from left-hemisphere brain damage and is characterized by semantic errors in reading single words aloud (e.g., reading spirit as whisky). Two types of explanation for this syndrome have been advanced. One is that deep dyslexia results from a residual left-hemisphere reading system that has lost the ability to pronounce a printed word without reference to meaning. The second is that deep dyslexia reflects right-hemisphere word processing. Although previous attempts to adjudicate between these hypotheses have been inconclusive, the controversy can now be addressed by mapping functional anatomy. In this study, we demonstrate that reading by two deep dyslexic patients (CJ and JG) involves normal or enhanced activity in spared left-hemisphere regions associated with naming (Broca's area and the left posterior inferior temporal cortex) and with the meanings of words (the left posterior temporo-parietal cortex and the left anterior temporal cortex). In the right-hemisphere homologues of these regions, there was inconsistent activation within the normal group and between the deep dyslexic patients. One (CJ) showed enhanced activity (relative to the normals) in the right anterior inferior temporal cortex, the other (JG) in the right Broca's area, and both in the right frontal operculum. Although these differential right-hemisphere activations may have influenced the reading behavior of the patients, their activation patterns primarily reflect semantic and phonological systems in spared regions of the left hemisphere. These results preclude an explanation of deep dyslexia in terms of purely right-hemisphere word processing.

scholarly journals Spatio-temporal dynamics of EEG features during sleep in major depressive disorder after treatment with escitalopram:A pilot study

2019 ◽  
Author(s):  
Li Wu ◽  
Xue-Qin Wang ◽  
Teng-Fei Dong ◽  
Ling Lei ◽  
Su-Xia Li ◽  
...  
Keyword(s):  
Major Depressive Disorder ◽  
Depressive Disorder ◽  
Right Hemisphere ◽  
Temporal Dynamics ◽  
Sleep Eeg ◽  
Sleep Stages ◽  
Major Depressive ◽  
Pharmacological Mechanism ◽  
Spatio Temporal ◽  
Eeg Features

Abstract Background: Previous studies have shown escitalopram is related to sleep quality. However, effects of escitalopram on dynamics of electroencephalogram (EEG) features especially during different sleep stages have not been reported. This study may help to reveal pharmacological mechanism underlying escitalopram treatment.Methods: The spatial and temporal responses of patients with major depressive disorder (MDD) to escitalopram treatment were analyzed in this study. Eleven MDD patients and eleven healthy control subjects who completed whole tests were included in the final statistics. Six-channel sleep EEG signals were acquired during sleep. Power spectrum and nonlinear dynamics were used to analyze the spatio-temporal dynamics features of the sleep EEG after escitalopram treatment. Results: For temporal dynamics: after treatment, there was a significant increase in the relative energy (RE) of band, accompanied by a significant decrease in the RE of band. Lempel-Ziv complexity and C0 complexity values were significantly lower. EEG changes at different sleep stages also showed the same regulation as the whole sleep process. For spatio dynamics: after treatment, the EEG response of the left and right hemisphere showed asymmetry. Further analysis of brain region-specific targets found that the frontal cortex showed a more intense EEG response with escitalopram treatment than central and occipital cortices.Conclusions: These findings may contribute to a comprehensive understanding of the pharmacological mechanism of escitalopram in the treatment of depression.

scholarly journals Further to the Left: Stress-Induced Increase of Spatial Pseudoneglect During the COVID-19 Lockdown

2021 ◽  
Vol 12 ◽  
Author(s):  
Federica Somma ◽  
Paolo Bartolomeo ◽  
Federica Vallone ◽  
Antonietta Argiuolo ◽  
Antonio Cerrato ◽  
...  
Keyword(s):  
Coping Strategies ◽  
Spatial Cognition ◽  
Perceived Stress ◽  
Psychological Health ◽  
Right Hemisphere ◽  
Opposite Pattern ◽  
Leftward Bias ◽  
Student Stress ◽  
Related Stress ◽  
The Right

BackgroundThe measures taken to contain the coronavirus disease 2019 (COVID-19) pandemic, such as the lockdown in Italy, do impact psychological health; yet, less is known about their effect on cognitive functioning. The transactional theory of stress predicts reciprocal influences between perceived stress and cognitive performance. However, the effects of a period of stress due to social isolation on spatial cognition and exploration have been little examined. The aim of the present study was to investigate the possible effects and impact of the COVID-19 pandemic on spatial cognition tasks, particularly those concerning spatial exploration, and the physiological leftward bias known as pseudoneglect. A right-hemisphere asymmetry for spatial attention processes crucially contributes to pseudoneglect. Other evidence indicates a predominantly right-hemisphere activity in stressful situations. We also analyzed the effects of lockdown on coping strategies, which typically show an opposite pattern of hemispheric asymmetry, favoring the left hemisphere. If so, then pseudoneglect should increase during the lockdown and be negatively correlated with the efficacy of coping strategies.MethodsOne week before the start of the lockdown due to COVID-19 in Italy (T1), we had collected data from a battery of behavioral tests including tasks of peri-personal spatial cognition. During the quarantine period, from late April to early May 2020 (T2), we repeated the testing sessions with a subgroup of the same participants (47 right-handed students, mean age = 20, SD = 1.33). At both testing sessions, participants performed digitized neuropsychological tests, including a Cancellation task, Radial Arm Maze task, and Raven’s Advanced Progressive Matrices. Participants also completed a newly developed COVID-19 Student Stress Scale, based on transactional models of stress, and the Coping Orientation to Problems Experienced—New Italian Version (COPE-NIV) to assess coping orientation.ResultsThe tendency to start cancelation from a left-sided item, to explore first a left-sided arm of the maze, and to choose erroneous response items on the left side of the page on Raven’s matrices increased from T1 to T2. The degree of pseudoneglect increment positively correlated with perceived stress and negatively correlated with Positive Attitude and Problem-Solving COPE-NIV subscales.ConclusionLockdown-related stress may have contributed to increase leftward bias during quarantine through a greater activation of the right hemisphere. On the other hand, pseudoneglect was decreased for better coping participants, perhaps as a consequence of a more balanced hemispheric activity in these individuals.

scholarly journals Neurophysiological Subtypes of Depressive Disorders

Psychiatry ◽  
2021 ◽  
Vol 19 (2) ◽  
pp. 63-76
Author(s):  
I. A. Lapin ◽  
T. A. Rogacheva ◽  
A. A. Mitrofanov
Keyword(s):  
Depressive Disorders ◽  
Right Hemisphere ◽  
Temporal Cortex ◽  
Statistical Research ◽  
Atypical Depression ◽  
Leading Role ◽  
Gamma Coherence ◽  
Left And Right ◽  
The Right ◽  
Bipolar Affective Disorders

Background: the clinical polymorphism of depressive disorders, together with the available data on the different responses of patients to treatment, motivate modern neuroscience to search for models that can explain such heterogeneity.Objective: to identify neurophysiological subtypes of depressive disorders.Patients and methods: 189 patients with moderate depression in the structure of a depressive episode (n = 42), recurrent depressive (n = 102) and bipolar affective disorders (n = 45); 56 healthy subjects. Clinical-psychopathological, psychometric, neurophysiological and statistical research methods were used in the work.The results: with the help of coherent EEG analysis, it is possible to identify at least 6 subtypes of the disorder, which characterize various branches of the pathogenesis of affective pathology, which go beyond the currently accepted nomenclature. The selected subtypes were determined by the profi les of dysfunctional interaction of various cortical zones in the alpha, beta and gamma ranges of the EEG. Subtype 1 was characterized by a decrease relative to the norm of imaginary alpha-coherence between the right parietal and left central, right parietal and left anterior temporal, as well as the right parietal and right anterior temporal EEG leads (P4-C3, P4-F7, P4-F8) and explained part of depressions, in the pathogenesis of which the leading role was played by violations of the promotion of positive and suppression of negative affect. Subtype 2 — an increase in beta-2-imaginary-coherence between the frontal leads of the left and right hemispheres, between the left frontal and right central cortex (F3-F4; F3-C4) and its decrease between the central cortical zones (C4-C3), in clinical terms this subtype was characterized by a persistent hedonic response and was associated with the clinical picture of atypical depression. Subtype 3 — an increase in imaginary alpha-coherence between the frontal (F4-F3) and its decrease between the central leads of the left and right hemisphere (C4-C3), correlated with the severity of depressive rumination. Subtype 4 — a decrease in imaginary alpha-coherence between the anterior temporal and frontal, as well as the anterior temporal and central cortex of the right hemisphere (F8-F4 and F8-C4), explained part of the depressions that developed against the background of avoidance personality disorder. Subtype 5 — a decrease in imaginary gamma coherence between the frontal and parietal, as well as the central and occipital cortical zones of the left hemisphere (F3-P3 and C3-O1), was associated with an outwardly oriented utilitarian style of thinking (alexithymia). Subtype 6 — a decrease in imaginary beta-1 coherence between the left central and right anterior temporal cortex (C3-F8), explained part of the depression with phobic and hypochondriacal disorders in the structure of recurrent depressive disorder. Such a clinical and biological typology seems new and promising in terms of searching for specifi c neurophysiological disorders in different types of depression and, accordingly, reaching differentiated therapeutic recommendations.

Tonotopy of the Auditory-Evoked Field Component N100m in Patients with Schizophrenia

2000 ◽  
Vol 14 (3) ◽  
pp. 131-141 ◽  
Author(s):  
T. Rosburg ◽  
I. Kreitschmann-Andermahr ◽  
T. Ugur ◽  
H. Nestmann ◽  
H. Nowak ◽  
...  
Keyword(s):  
Right Hemisphere ◽  
Temporal Cortex ◽  
Dipole Orientation ◽  
Global Field Power ◽  
Functional Reorganization ◽  
Schizophrenic Patients ◽  
Posterior Direction ◽  
The Right ◽  
Main Effects ◽  
Anterior Posterior

Abstract A number of clinical studies on the auditory neuromagnetic evoked field (AEF) component N100m have reported an altered lateralization in schizophrenic patients. This study addresses the problem of a possible functional reorganization of the temporal cortex in schizophrenia by examining the tonotopic organization of the N100m. Thirty-two patients with schizophrenia and 33 healthy controls of both sexes took part. Two tone frequencies (1000 and 5000 Hz tone) were applied for auditory stimuli, and AEF were recorded over both hemispheres successively using a 31-channel biomagnetometer. The comparison of N100m dipole location and orientation between hemispheres revealed no alterations in male or female patients. Between tone frequencies highly significant differences were found for N100m peak latency, mean global field power, dipole orientation, and dipole location in the anterior-posterior direction. Although the main effects of frequency were found to be the same in patients and controls, the balance between hemispheres was altered in patients with schizophrenia, with respect to the dependence between frequency and dipole location in the anterior-posterior direction as well as between frequency and latency. In patients, the influence of frequency on these variables was more pronounced in the right hemisphere and less pronounced in the left, compared to controls.

Wada Testing Reveals Frontal Lateralization for the Memorization of Words and Faces

2002 ◽  
Vol 14 (1) ◽  
pp. 116-125 ◽  
Author(s):  
W. M. Kelley ◽  
J. G. Ojemann ◽  
R. D. Wetzel ◽  
C. P. Derdeyn ◽  
C. J. Moran ◽  
...  
Keyword(s):  
Right Hemisphere ◽  
Temporal Cortex ◽  
Memory Formation ◽  
Wada Test ◽  
Memory Impairments ◽  
Reversible Lesion ◽  
The Right ◽  
Open Question ◽  
Normal Performance ◽  
Better Than

Neuroimaging studies have suggested that specific regions of the frontal and medial temporal cortex are engaged during memory formation. Further, there is specialization across these regions such that verbal materials appear to preferentially engage the left regions while nonverbal materials primarily engage the right regions. An open question, however, has been to what extent frontal regions contribute to successful memory formation. The present study investigates this question using a reversible lesion technique known as the Wada test. Patients memorized words and unfamiliar faces while portions of their left and right hemispheres were temporarily anesthetized with sodium amytal. Subsequent memory tests revealed that faces were remembered better than words following left-hemisphere anesthesia, whereas words were remembered better than faces following right-hemisphere anesthesia. Importantly, inspection of the circulation affected by the amytal further suggests that these memory impairments did not result from direct anesthetization of the medial temporal regions. Taken in the context of the imaging findings, these results suggest that frontal regions may also contribute to memory formation in normal performance.

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