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.

Right hemisphere speech perception revealed by amobarbital injection and electrical interference

Neurology ◽  
1998 ◽  
Vol 51 (2) ◽  
pp. 458-464 ◽  
Author(s):  
D. Boatman ◽  
J. Hart ◽  
R. P. Lesser ◽  
N. Honeycutt ◽  
N. B. Anderson ◽  
...  
Keyword(s):  
Speech Perception ◽  
Left Hemisphere ◽  
Temporal Lobe ◽  
Right Hemisphere ◽  
Adult Brain ◽  
Left Posterior ◽  
Left And Right ◽  
Sodium Amobarbital ◽  
The Right ◽  
Electrical Interference

Objective: To investigate the right hemispheric speech perception capabilities of an adult right-handed patient with seizures.Methods: 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.Results: 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.Conclusions: The results suggest a functionally symmetric, parallel system in the adult brain with preferential use of left hemispheric pathways for speech perception.

scholarly journals Tumor location and reduction in functional MRI estimates of language laterality

2021 ◽  
pp. 1-11
Author(s):  
Monika M. Połczyńska ◽  
Lilian Beck ◽  
Taylor Kuhn ◽  
Christopher F. Benjamin ◽  
Timothy K. Ly ◽  
...  
Keyword(s):  
Functional Mri ◽  
Left Hemisphere ◽  
Right Hemisphere ◽  
Tumor Location ◽  
Broca’S Area ◽  
Broca's Area ◽  
Whole Brain ◽  
Language Dominance ◽  
Left Posterior ◽  
Language Laterality

OBJECTIVE Brain tumors located close to the language cortex may distort functional MRI (fMRI)–based estimates of language dominance. The nature of this distortion, and whether this is an artifact of numerous confounders, remains unknown. The authors hypothesized tumor bias based on laterality estimates independent of confounders and that the effects are the greatest for tumors proximal to Broca's area. METHODS To answer this question, the authors reviewed more than 1113 patients who underwent preoperative fMRI to match samples on 11 known confounders (tumor location, size, type, and grade; seizure history; prior neurosurgery; aphasia presence and severity; and patient age, sex, and handedness). The samples included 30 patients with left hemisphere tumors (15 anterior and 15 posterior) and 30 with right hemisphere tumors (15 anterior and 15 posterior), thus totaling 60 patients (25 women; 18 left-handed and 4 ambidextrous; mean age 47 [SD 14.1] years). Importantly, the authors matched not only patients with left and right hemisphere tumors but also those with anterior and posterior tumors. Standard fMRI laterality indices (LIs) were calculated using whole-brain and region of interest (ROI) approaches (Broca's and Wernicke's areas). RESULTS Tumors close to Broca's area in the left hemisphere decreased LIs independently of known confounders. At the whole-brain level, this appeared to reflect a decrease in LI values in patients with left anterior tumors compared with patients with right anterior tumors. ROI analysis replicated these findings. Broca's area LIs were significantly lower (p = 0.02) in patients with left anterior tumors (mean LI 0.28) when compared with patients with right anterior tumors (mean LI 0.70). Changes in Wernicke's area–based LIs did not differ as a function of the tumor hemisphere. Therefore, in patients with left anterior tumors, it is essential to assess language laterality using left posterior ROIs. In all remaining tumor groups (left posterior tumors and right hemisphere tumors), language laterality derived from the anterior language ROI was the most robust measure of language dominance. CONCLUSIONS Patients with tumors close to Broca's area showed more bilateral fMRI language maps independent of known confounders. The authors caution against the assumption that this reduced language laterality suggests no or little risk to language function following tumor resection in the left inferior frontal gyrus. Their results address how to interpret fMRI data for neurosurgical purposes, along with theoretical questions of contralesional functional compensation and disinhibition.

Dissociating Verbal and Nonverbal Conceptual Processing in the Human Brain

2006 ◽  
Vol 18 (6) ◽  
pp. 1018-1028 ◽  
Author(s):  
Guillaume Thierry ◽  
Cathy J. Price
Keyword(s):  
Left Hemisphere ◽  
Right Hemisphere ◽  
Functional Neuroimaging ◽  
Temporal Cortex ◽  
Conceptual System ◽  
Conceptual Processing ◽  
Making Sense ◽  
Left And Right ◽  
Neuropsychological Evidence ◽  
The Right

Functional neuroimaging has highlighted a left-hemisphere conceptual system shared by verbal and nonverbal processing despite neuropsychological evidence that the ability to recognize verbal and nonverbal stimuli can doubly dissociate in patients with left- and right-hemisphere lesions, respectively. Previous attempts to control for perceptual differences between verbal and nonverbal stimuli in functional neuroimaging studies may have hidden differences arising at the conceptual level. Here we used a different approach and controlled for perceptual confounds by looking for amodal verbal and nonverbal conceptual activations that are common to both the visual and auditory modalities. In addition to the left-hemisphere conceptual system activated by all meaningful stimuli, we observed the left/right double dissociation in verbal and nonverbal conceptual processing, predicted by neuropsychological studies. Left middle and superior temporal regions were selectively more involved in comprehending words—heard or read—and the right midfusiform and right posterior middle temporal cortex were selectively more involved in making sense of environmental sounds and images. Thus, the neuroanatomical basis of a verbal/nonverbal conceptual processing dissociation is established.

scholarly journals Perceptual and Semantic Components of Memory for Objects and Faces: A PET Study

2001 ◽  
Vol 13 (4) ◽  
pp. 430-443 ◽  
Author(s):  
Jon S. Simons ◽  
Kim S. Graham ◽  
Adrian M. Owen ◽  
Karalyn Patterson ◽  
John R. Hodges
Keyword(s):  
Recognition Memory ◽  
Right Hemisphere ◽  
Temporal Cortex ◽  
Neural Substrates ◽  
Neural Correlates ◽  
Semantic Knowledge ◽  
Inferior Temporal Cortex ◽  
Within Subjects ◽  
Blood Flow Increase ◽  
The Right

Previous studies have suggested differences in the neural substrates of recognition memory when the contributions of perceptual and semantic information are manipulated. In a within-subjects design PET study, we investigated the neural correlates of the following factors: material type (objects or faces), semantic knowledge (familiar or unfamiliar items), and perceptual similarity at study and test (identical or different pictures). There was consistent material-specific lateralization in frontal and temporal lobe regions when the retrieval of different types of nonverbal stimuli was compared, with objects activating bilateral areas and faces preferentially activating the right hemisphere. Retrieval of memories for nameable, familiar items was associated with increased activation in the left ventrolateral prefrontal cortex, while memory for unfamiliar items involved occipital regions. Recognition memory for different pictures of the same item at study and test produced blood flow increase in left inferior temporal cortex. These results have implications for our understanding of the neural correlates of perceptual and semantic contributions to recognition memory.

scholarly journals What Does the Right Hemisphere Know about Phoneme Categories?

2011 ◽  
Vol 23 (3) ◽  
pp. 552-569 ◽  
Author(s):  
Michael Wolmetz ◽  
David Poeppel ◽  
Brenda Rapp
Keyword(s):  
Left Hemisphere ◽  
Right Hemisphere ◽  
Brain Lesion ◽  
Temporal Cortex ◽  
Primary Role ◽  
Lesion Studies ◽  
Pronounceable Nonword ◽  
The Right ◽  
Category Effects ◽  
Phonemic Category

Innate auditory sensitivities and familiarity with the sounds of language give rise to clear influences of phonemic categories on adult perception of speech. With few exceptions, current models endorse highly left-hemisphere-lateralized mechanisms responsible for the influence of phonemic category on speech perception, based primarily on results from functional imaging and brain-lesion studies. Here we directly test the hypothesis that the right hemisphere does not engage in phonemic analysis. By using fMRI to identify cortical sites sensitive to phonemes in both word and pronounceable nonword contexts, we find evidence that right-hemisphere phonemic sensitivity is limited to a lexical context. We extend the interpretation of these fMRI results through the study of an individual with a left-hemisphere lesion who is right-hemisphere reliant for initial acoustic and phonetic analysis of speech. This individual's performance revealed that the right hemisphere alone was insufficient to allow for typical phonemic category effects but did support the processing of gradient phonetic information in lexical contexts. Taken together, these findings confirm previous claims that the right temporal cortex does not play a primary role in phoneme processing, but they also indicate that lexical context may modulate the involvement of a right hemisphere largely tuned for less abstract dimensions of the speech signal.

scholarly journals Left hemisphere abnormalities in developmental prosopagnosia when looking at faces but not words

2019 ◽  
Vol 1 (1) ◽  
Author(s):  
Christian Gerlach ◽  
Solja K Klargaard ◽  
Dag Alnæs ◽  
Knut K Kolskår ◽  
Jens Karstoft ◽  
...  
Keyword(s):  
Face Recognition ◽  
Left Hemisphere ◽  
Word Processing ◽  
Right Hemisphere ◽  
Temporal Cortex ◽  
Brain Regions ◽  
Lateral Occipital Complex ◽  
Line Drawings ◽  
Neural Underpinnings ◽  
Mri Study

Abstract Developmental prosopagnosia is a disorder characterized by profound and lifelong difficulties with face recognition in the absence of sensory or intellectual deficits or known brain injury. While there has been a surge in research on developmental prosopagnosia over the last decade and a half, the cognitive mechanisms behind the disorder and its neural underpinnings remain elusive. Most recently it has been proposed that developmental prosopagnosia may be a manifestation of widespread disturbance in neural migration which affects both face responsive brain regions as well as other category-sensitive visual areas. We present a combined behavioural and functional MRI study of face, object and word processing in a group of developmental prosopagnosics (N = 15). We show that developmental prosopagnosia is associated with reduced activation of core ventral face areas during perception of faces. The reductions were bilateral but tended to be more pronounced in the left hemisphere. As the first study to address category selectivity for word processing in developmental prosopagnosia, we do not, however, find evidence for reduced activation of the visual word form area during perception of orthographic material. We also find no evidence for reduced activation of the lateral occipital complex during perception of objects. These imaging findings correspond well with the behavioural performance of the developmental prosopagnosics, who show severe impairment for faces but normal reading and recognition of line drawings. Our findings suggest that a general deficit in neural migration across ventral occipito-temporal cortex is not a viable explanation for developmental prosopagnosia. The finding of left hemisphere involvement in our group of developmental prosopagnosics was at first surprising. However, a closer look at existing studies shows similar, but hitherto undiscussed, findings. These left hemisphere abnormalities seen in developmental prosopagnosia contrasts with lesion and imaging studies suggesting primarily right hemisphere involvement in acquired prosopagnosia, and this may reflect that the left hemisphere is important for the development of a normal face recognition network.

scholarly journals Multiple adjoining word and face selective regions in ventral temporal cortex exhibit distinct dynamics

2020 ◽  
Author(s):  
Matthew J. Boring ◽  
Edward H. Silson ◽  
Michael J. Ward ◽  
R. Mark Richardson ◽  
Julie A. Fiez ◽  
...  
Keyword(s):  
Visual Field ◽  
Left Hemisphere ◽  
Visual Processing ◽  
Word Processing ◽  
Right Hemisphere ◽  
Temporal Dynamics ◽  
Temporal Cortex ◽  
7 Tesla ◽  
Important Principle ◽  
Ventral Temporal Cortex

AbstractThe map of category-selectivity in human ventral temporal cortex (VTC) provides organizational constraints to models of object recognition. One important principle is lateral-medial response biases to stimuli that are typically viewed in the center or periphery of the visual field. However, little is known about the relative temporal dynamics and location of regions that respond preferentially to stimulus classes that are centrally viewed, like the face and word processing networks. Here, word- and face-selective regions within VTC were mapped using intracranial recordings from 36 patients. Partially overlapping, but also anatomically dissociable patches of face and word selectivity were found in ventral temporal cortex. In addition to canonical word-selective regions along the left posterior occipitotemporal sulcus, selectivity was also located medial and anterior to face-selective regions on the fusiform gyrus at the group level and within individual subjects. These regions were replicated using 7-Tesla fMRI in healthy subjects. Left hemisphere word-selective regions preceded right hemisphere responses by 125 ms, potentially reflecting the left hemisphere bias for language; with no hemispheric difference in face-selective response latency. Word-selective regions along the posterior fusiform responded first, then spread medially and laterally, then anteriorally. Face-selective responses were first seen in posterior fusiform regions bilaterally, then proceeded anteriorally from there. For both words and faces, the relative delay between regions was longer than would be predicted by purely feedforward models of visual processing. The distinct time-courses of responses across these regions, and between hemispheres, suggest a complex and dynamic functional circuit supports face and word perception.Significance StatementRepresentations of visual objects in the human brain have been shown to be organized by several principles, including whether those objects tend to be viewed centrally or in the periphery of the visual field. However, it remains unclear how regions that process objects that are viewed centrally, like words and faces, are organized relative to one another. Here, direct neural recordings and 7T fMRI demonstrate that several intermingled regions in ventral temporal cortex participate in word and face processing. These regions display differences in their temporal dynamics and response characteristics, both within and between brain hemispheres, suggesting they play different roles in perception. These results illuminate extended, bilateral, and dynamic brain pathways that support face perception and reading.

scholarly journals Volumetric MRI Analysis of Brain Structures in Patients with History of First and Repeated Suicide Attempts: A Cross Sectional Study

Diagnostics ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 488
Author(s):  
Milda Sarkinaite ◽  
Rymante Gleizniene ◽  
Virginija Adomaitiene ◽  
Kristina Dambrauskiene ◽  
Nijole Raskauskiene ◽  
...  
Keyword(s):  
Suicide Attempt ◽  
Left Hemisphere ◽  
Cortical Thickness ◽  
Suicide Attempts ◽  
Right Hemisphere ◽  
Temporal Cortex ◽  
Brain Regions ◽  
Cross Sectional ◽  
Suicide Attempters ◽  
The Right

Structural brain changes are found in suicide attempters and in patients with mental disorders. It remains unclear whether the suicidal behaviors are related to atrophy of brain regions and how the morphology of specific brain areas is changing with each suicide attempt. The sample consisted of 56 patients hospitalized after first suicide attempt (first SA) (n = 29), more than one suicide attempt (SA > 1) (n = 27) and 54 healthy controls (HC). Brain volume was measured using FreeSurfer 6.0 automatic segmentation technique. In comparison to HC, patients with first SA had significantly lower cortical thickness of the superior and rostral middle frontal areas, the inferior, middle and superior temporal areas of the left hemisphere and superior frontal area of the right hemisphere. In comparison to HC, patients after SA > 1 had a significantly lower cortical thickness in ten areas of frontal cortex of the left hemisphere and seven areas of the right hemisphere. The comparison of hippocampus volume showed a significantly lower mean volume of left and right parts in patients with SA > 1, but not in patients with first SA. The atrophy of frontal, temporal cortex and hippocampus parts was significantly higher in repeated suicide attempters than in patients with first suicide attempt.

Covert Speech Arrest Induced by rTMS over Both Motor and Nonmotor Left Hemisphere Frontal Sites

2005 ◽  
Vol 17 (6) ◽  
pp. 928-938 ◽  
Author(s):  
Lisa Aziz-Zadeh ◽  
Luigi Cattaneo ◽  
Magali Rochat ◽  
Giacomo Rizzolatti
Keyword(s):  
Left Hemisphere ◽  
Right Hemisphere ◽  
Repetitive Transcranial Magnetic Stimulation ◽  
Inferior Frontal Gyrus ◽  
Posterior Part ◽  
Left Frontal Lobe ◽  
Posterior Site ◽  
Left Posterior ◽  
The Right ◽  
Overt Speech

Blocking the capacity to speak aloud (overt speech arrest, SA) may be induced by repetitive transcranial magnetic stimulation (rTMS). The possibility, however, of blocking internal speech (covert SA) has not been explored. To investigate this issue, we conducted two rTMS experiments. In the first experiment, we stimulated two left frontal lobe sites. The first was a motor site (left posterior site) and the second was a nonmotor site located in correspondence to the posterior part of the inferior frontal gyrus (IFG) (left anterior site). The corresponding right hemisphere nonmotor SA site was stimulated as a control. In the second experiment, we focused on the right hemisphere and stimulated a right hemisphere motor site (right posterior site), and, as control sites, a right hemisphere nonmotor site corresponding to the IFG (right anterior site) and a left hemisphere anteromedial site (left control). For both experiments, participants performed a syllable counting task both covertly and overtly for each stimulation site. Longer latencies in this task imply the occurrence of an overt and/or covert SA. All participants showed significantly longer latencies when stimulation was either over the left posterior or the left anterior site, as compared with the right hemisphere site (Experiment 1). This result was observed for the overt and covert speech task alike. During stimulation of the posterior right hemisphere site, a dissociation for overt and covert speech was observed. An overt SA was observed but there was no evidence for a covert SA (Experiment 2). Taken together, the results show that rTMS can induce a covert SA when applied to areas over the brain that are pertinent to language. Furthermore, both the left posterior/motor site and the left anterior/IFG site appear to be essential to language elaboration even when motor output is not required.

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