Sylvian Fissure Asymmetry Research Articles

Measurement of Sylvian Fissure asymmetry and occipital bending in humans and Pan troglodytes

The evolution of human-specific lateralised functions such as language has been linked to the development of structural asymmetries in the brain. Here we applied state of the art image analysis techniques to measure Sylvian Fissure (SF) asymmetry and Occipital Bending (OB) in 3D Magnetic Resonance (MR) images of the brain obtained in-vivo for 30 humans and 30 chimpanzees (Pan troglodytes).SF morphology differed between species, with the human SF terminating more superiorly in right inferior parietal lobe, an asymmetry that was on average absent in chimpanzees (F (1,52) = 5.963, p = 0.018). Irrespective of morphology, Total SF Length was, as previously reported, leftward in humans but not in chimpanzees, although the difference did not reach significance between species. However, when only brains possessing comparable bilateral SF bifurcation morphology were compared, humans showed previously reported “Typical” left-lateralised Anterior-Horizontal (AH-SF) and right-lateralised Vertical (V-SF) SF asymmetries. In contrast, chimpanzees lacked both asymmetries, and this approached being a significant difference between-species in the AH-SF segment (F (1, 34) = 3.680, p = 0.064).On average in humans the left occipital lobe crossed the midline toward the right (Rightward OB) which was significantly different from the chimpanzee cohort that showed no average OB (Independent-Samples Mann-Whitney U Test, p = 0.012). Furthermore, OB was related to SF asymmetry in humans, such that the more rightward V-SF and leftward AH-SF, the more rightward the OB. This “Default” pattern of SF and OB asymmetries was found in 41.7% of human individuals with bilateral SF bifurcation but none of the chimpanzees.To our knowledge, this is the first study highlighting that a pattern of SF and OB asymmetry distinguishes the human from the chimpanzee brain, and suggests this may be associated with a unique trajectory of brain development and functional abilities in humans.

Sylvian Fissure and Parietal Anatomy in Children with Autism Spectrum Disorder

Autism spectrum disorder (ASD) is characterized by deficits in social functioning and language and communication, with restricted interests or stereotyped behaviors. Anatomical differences have been found in the parietal cortex in children with ASD, but parietal subregions and associations between Sylvian fissure (SF) and parietal anatomy have not been explored. In this study, SF length and anterior and posterior parietal volumes were measured on MRI in 30 right-handed boys with ASD and 30 right-handed typically developing boys (7–14 years), matched on age and non-verbal IQ. There was leftward SF and anterior parietal asymmetry, and rightward posterior parietal asymmetry, across groups. There were associations between SF and parietal asymmetries, with slight group differences. Typical SF asymmetry was associated with typical anterior and posterior parietal asymmetry, in both groups. In the atypical SF asymmetry group, controls had atypical parietal asymmetry, whereas in ASD there were more equal numbers of individuals with typical as atypical anterior parietal asymmetry. We did not find significant anatomical-behavioral associations. Our findings of more individuals in the ASD group having a dissociation between cortical asymmetries warrants further investigation of these subgroups and emphasizes the importance of investigating anatomical relationships in addition to group differences in individual regions.

Sylvian fissure and parietal anatomy in children with autism spectrum disorder.

Autism spectrum disorder (ASD) is characterized by deficits in social functioning and language and communication, with restricted interests or stereotyped behaviors. Anatomical differences have been found in the parietal cortex in children with ASD, but parietal subregions and associations between Sylvian fissure (SF) and parietal anatomy have not been explored. In this study, SF length and anterior and posterior parietal volumes were measured on MRI in 30 right-handed boys with ASD and 30 right-handed typically developing boys (7–14 years), matched on age and non-verbal IQ. There was leftward SF and anterior parietal asymmetry, and rightward posterior parietal asymmetry, across groups. There were associations between SF and parietal asymmetries, with slight group differences. Typical SF asymmetry was associated with typical anterior and posterior parietal asymmetry, in both groups. In the atypical SF asymmetry group, controls had atypical parietal asymmetry, whereas in ASD there were more equal numbers of individuals with typical as atypical anterior parietal asymmetry. We did not find significant anatomical-behavioral associations. Our findings of more individuals in the ASD group having a dissociation between cortical asymmetries warrants further investigation of these subgroups and emphasizes the importance of investigating anatomical relationships in addition to group differences in individual regions.

Sylvian fissure asymmetry in capuchin monkeys (Cebus apella)

Asymmetries of the sylvian fissure (SF) are believed to reflect an enlargement of the posterior temporal lobe, particularly a region that corresponds to part of Wernicke's area in humans. In nonhuman primates the homologue to the region may be involved in the discrimination and processing of species-specific vocalisations. As capuchin monkeys are large brained, socially complex primates with a rich vocal repertoire, it was hypothesised that they would display asymmetry of the SF. We used high-resolution 3T MRI scans to investigate this asymmetry in 17 brown capuchin monkeys (Cebus apella; 9 males, 8 females). Results indicated a trend towards population-level leftward asymmetry in the lateral region of the SF. Post hoc analyses revealed significant sex differences in SF asymmetry, with females displaying a population-level leftward asymmetry of the lateral region of the SF. Age was a significant mediator of the effects of sex on asymmetry of the lateral region of the SF. These results provide evidence that capuchin monkeys display sex differences in the asymmetry of the SF and show developmental changes in hemispheric lateralisation.

Perisylvian Sulcal Morphology and Cerebral Asymmetry Patterns in Adults Who Stutter

Previous investigations of cerebral anatomy in persistent developmental stutterers have reported bilateral anomalies in the perisylvian region and atypical patterns of cerebral asymmetry. In this study, perisylvian sulcal patterns were analyzed to compare subjects with persistent developmental stuttering (PDS) and an age-, hand-, and gender-matched control group. This analysis was accomplished using software designed for 3-dimensional sulcal identification and extraction. Patterns of cerebral asymmetry were also investigated with standard planimetric measurements. PDS subjects showed a small but significant increase in both the number of sulci connecting with the second segment of the right Sylvian fissure and in the number of suprasylvian gyral banks (of sulci) along this segment. No differences were seen in the left perisylvian region for either sulcal number or gyral bank number. Measurements of asymmetry revealed typical patterns of cerebral asymmetry in both groups with no significant differences in frontal and occipital width asymmetry, frontal and occipital pole asymmetry, or planum temporale and Sylvian fissure asymmetries. The subtle difference in cortical folding of the right perisylvian region observed in PDS subjects may correlate with functional imaging studies that have reported increased right-hemisphere activity during stuttered speech.

Are planum temporale and sylvian fissure asymmetries directly related?: A MRI study in great apes

In humans and great apes, both the planum temporale (PT—part of Wernicke’s area) and the sylvian fissure (SF) in the left cerebral hemisphere have been consistently shown to be larger than the corresponding structures in the right hemisphere. The greater length of the SF in the left hemisphere is commonly thought to be a direct consequence of the larger expansion of the PT in the same hemisphere. However, there is a lack of studies that have attempted to directly assess the tenability of this hypothesis. To address this lack of data, we collected magnetic resonance images (MRI) of the brain in 28 apes. The surface area of the PT and the length of the pre- and post-central SF were measured in each hemisphere using image acquisition and analysis software. In accordance with previous findings, the PT was markedly larger in the left hemisphere than in the right, and there was also a leftward asymmetry of the SF, particularly of its post-central section. However, we found no statistically significant correlation between asymmetry of the PT and of the post-central SF, whereas we did find evidence of a positive association between asymmetry of the post-central SF and of the inferior parietal lobe. These results are congruent with those of a recent study with human subjects [Neuropsychiatry, Neuropsychology and Behavioral Neurology 12 (1999) 1]. Overall, this converging evidence leads us to question the widely accepted notion of a direct relationship between PT and SF asymmetries and to consider possible implications of this finding for the study of the evolutionary origin of PT asymmetry in primates.

The temporal lobe in schizophrenia from uni- and multiply affected families

To investigate the effect of genetic loading on brain structure in schizophrenia, we hypothesized that separating families into uniaffected and multiply affected would reveal effects of schizophrenia and family type. Volumes and asymmetries of the amygdala–hippocampus-complex (AHC) and sylvian fissure (SF) were determined using magnetic resonance imaging of subjects with schizophrenia from 12 uniaffected and 14 multiply affected families, and ten healthy controls. AHC volume was reduced in schizophrenia, particularly on the right side in subjects from uniaffected families. AHC asymmetry was disturbed, too. Enlargement of the right SF and disturbed SF asymmetry was demonstrated in subjects from uniaffected families as well. Comparing subjects from uni- and multiply affected families may be a useful strategy to reduce variability for future studies of environmental interactions with genetic risk for schizophrenia.

Sylvian Fissure Asymmetries in Nonhuman Primates Revisited: A Comparative MRI Study

Magnetic resonance images (MRI) were collected in a sample of 28 apes, 16 Old World monkeys and 8 New World monkeys. The length of the sylvian fissure (SF) and the superior temporal sulcus (STS) was traced in each hemisphere from three regions of the cerebral cortex. These three regions were labeled according to their position on the sagittal plane as lateral, medial and insular. It was hypothesized that the length and asymmetry of these fissures would be dependent on the region of measurement and that a leftward asymmetry in the SF and STS would be more robust in the great ape sample than for the monkeys. The results indicated within the ape sample a population-level leftward asymmetry in the medial and insular regions of the SF. Within the Old and New World monkey samples, the SF was leftward in the medial region at the population level, but not at the insular region. Additionally, the Old World monkeys exhibited a population-level rightward lateral SF and a rightward lateral STS. No other families exhibited population-level asymmetries in the lateral region of the SF or in any region of the STS. These results are consistent with findings reported in apes and, to a lesser extent, monkeys. MRI has excellent potential for comparing neuroanatomy across taxonomic families that will help future investigations.

Gender differences in Sylvian fissure asymmetry in multiplex families affected with schizophrenia

Gender differences in Sylvian fissure asymmetry in multiplex families affected with schizophrenia

Cortical variability and asymmetry in normal aging and Alzheimer's disease.

The onset of Alzheimer's disease (AD) is accompanied by a complex and distributed pattern of neuroanatomic change, difficult to distinguish clinically from dynamic alterations in normal aging. Extreme variations in the sulcal patterns of the human cortex have made it difficult to identify diffuse and focal variations in cortical structure in neurodegenerative disease. We report the first comprehensive 3D statistical analysis of deep sulcal structure in vivo, in both normal aging and dementia. High-resolution 3D T1-weighted fast SPGR (spoiled GRASS) MRI volumes were acquired from 10 patients diagnosed with AD (NINCDS-ARDRA criteria; age: 71.9 +/- 10.7 years) and 10 normal subjects matched for age (72.9 +/- 5.6 years), gender, educational level and handedness. Scans were digitally transformed into Talairach stereotaxic space. To determine specific patterns of cortical variation in dementia patients, 3D average and probabilistic maps of primary deep sulci were developed for both normal and AD groups. Major sulci (including supracallosal, cingulate, marginal, parieto-occipital, anterior and posterior calcarine sulci, and Sylvian fissures) were modeled as complex systems of 3D surfaces using a multi-resolution parametric mesh approach. Variations and asymmetries in their extents, curvature, area and surface complexity were evaluated. Three-dimensional maps of anatomic variability, structural asymmetry and local atrophy indicated severe regionally selective fiber loss in AD. A midsagittal area loss of 24.5% at the corpus callosum's posterior midbody (P < 0.025) matched increases in structural variability in corresponding temporo-parietal projection areas. Confidence limits on 3D cortical variation, visualized in 3D, exhibited severe increases in AD from 2 to 4 mm at the callosum to a peak SD of 19.6 mm at the posterior left Sylvian fissure. Normal Sylvian fissure asymmetries (right higher than left; P < 0.0005), mapped for the first time in three dimensions, were accentuated in AD (P < 0.0002), and were greater in AD than in controls (P < 0.05). Severe AD-related increases in 3D variability and asymmetry may reflect disease-related disruption of the commissural system connecting bilateral temporal and parietal cortical zones, regions known to be at risk of early metabolic dysfunction, perfusion deficits and selective neuronal loss in AD.

Anomalous cerebral asymmetry and language processing in schizophrenia.

Reversal or reduction of normal structural cerebral asymmetries may be related to the pathogenesis of schizophrenia, but this relationship remains controversial. We review the literature and describe a further study designed to detect whether anomalous asymmetries are present early in the illness (at the first episode), whether they predict deficits in language processing, and whether they may be related to a genetic predisposition for schizophrenia. Asymmetries of brain widths and segments of the sylvian fissure were assessed in a magnetic resonance imaging study of 87 patients with a first episode of schizophrenia and 52 normal controls. These asymmetries were correlated with specific measures of language processing, memory, and hand skill. An independent group of 14 pairs of siblings with schizophrenia were also evaluated for evidence of heritability to cerebral asymmetries. Width asymmetries were reduced in patients compared with controls in the posterior (p = 0.02) and occipital (p = 0.05) regions. Brain horizontal length, on the other hand, was significantly more asymmetrical in patients (left > right; p = 0.04). For sylvian fissure measurements, asymmetries in controls (left > right) were greatest for the horizontal component; this asymmetry tended to detect differences in patients by comparison with controls (p < 0.06). In a range of tests of language and memory, few significant correlations between performance and cerebral asymmetries were detected either in patients or controls, although patients consistently scored poorer than controls in the majority of tests. In 14 pairs of psychotic siblings, within-pair correlations for the horizontal sylvian fissure asymmetry were significantly greater than between-pair correlations. These findings are consistent with the early presence (possibly genetic) of anomalous cerebral asymmetry. However, the functional correlates of reduced asymmetry remain obscure.

A study of sylvian fissure asymmetries in the runwell 3 series of psychotic brains

A study of sylvian fissure asymmetries in the runwell 3 series of psychotic brains

The temporal lobes, reversed asymmetry and the genetics of schizophrenia

Mechanisms determining temporal lobe structural asymmetries may be involved in the pathogenesis of schizophrenia. To investigate the temporal lobes in familial schizophrenia, computed tomographic scans were obtained from 51 subjects (seven families). Enlargement of sylvian fissures and temporal lobe sulcal spaces was observed in family members with schizophrenia. The posterior one-third of the sylvian fissure was larger on the left side in subjects with schizophrenia, and larger on the right side in unaffected individuals. This disturbed pattern of posterior sylvian fissure asymmetry suggests that adjacent language regions may be affected in schizophrenia. An intermediate degree of disturbance in subjects who had schizophrenia-related illnesses or were obligate carriers suggests that genetic factors may be important determinants of temporal lobe asymmetries in familial schizophrenia.

Sylvian fissure asymmetries in monozygotic twins: A test of laterality in schizophrenia

To address prior reports that schizophrenia is associated with loss of normal brain asymmetry and that it might be linked to a defect of a gene controlling cerebral laterization, we measured on three-dimensional cortical renderings from magnetic resonance imaging (MRI) scans the lengths and angles of the sylvian fissures in 10 normal monozygotic (MZ) twin pairs (n = 10 pairs) and in 10 MZ pairs discordant for schizophrenia (n = 10 pairs). We confirmed in both sets of twins the expected normal asymmetries of length and angle of the sylvian fissure. We also confirmed that the length asymmetry occurs solely in the region of the planum temporale. In the discordant twins, affected and unaffected twins did not differ in asymmetry measures, thus failing to support an association between illness per se and diminished asymmetry. Moreover, the discordant twins as a group did not differ from the normal twins as a group, thus failing to confirm the hypothesis of a genetic association with abnormal asymmetry. The implications of variations in methodology and patient samples are discussed.

The End Point of the Sylvian Fissure is Higher on the Right than the Left in Cat Brain as in Human Brain

The height of the end point of the sylvian fissure (SF) was analyzed in the right and left brains of male and female adult cats. A corrected SF asymmetry coefficient (AC) was computed for each brain. An AC larger than zero (AC+) showed a rightward asymmetry, and an AC smaller than zero (AC-) a leftward asymmetry. In the total sample, ACs fit a normal distribution with a mean significantly larger than zero. Of these brains, 75% had ACs larger than zero median; 23.4% had ACs smaller than zero median. Of 11 right-pawed cats, 90.9% had ACs larger than zero. Of 13 left-pawed male cats, there was no significant difference between AC+ and AC- brains. In right-pawed female cats, the right SF was also higher in most animals, but the difference did not reach the 5% significance level. In left-pawed female cats, the number of AC+ brains significantly exceeded that of AC-brains. Thus, the brains of the left-pawed male cats resembled those of the right-pawed female cats; right-pawed male cats resembled left-pawed female cats with regard to asymmetries in SF height. It was concluded that the human brain is not unique in SF asymmetries, which may be linked to manual asymmetry and sex hormones.

Individual differences in brain asymmetries and fiber composition in the human corpus callosum

There have been several recent reports concerning individual differences inthe gross morphometry of the human corpus callosum. However, no studies exist on individual differences in the fiber composition of the corpus callosum. Here we report for the first time the relation of fiber composition in specific callosal segments (as seen in light microscopy) to anatomical asymmetries in language-gifted cortex, as a function of sex. We found a significant negative correlation between Sylvian fissure asymmetries and the total numbers of fibers in the isthmus of males, and in the anterior splenium of females. In addition, a population of relatively large fibers (between 1 μm and 3 μm in diameter) in the isthmus showed a strong negative correlation with perisylvian asymmetries only in males. These findings suggest a sex-dependent, pathway-specific decrease in interhemispheric connectivity with increasing lateralization.

Loss of sylvian fissure asymmetry in schizophrenia: A quantitative post mortem study

The sylvian fissure is known to be one of the most asymmetric structures of the human brain. Sylvian fissure length was measured in post-mortem brains of 35 schizoprenic patients and 33 matched non psychiatric control subjects. The schizophrenics showed a significantly reduced length of the left sylvian fissure ( - 16%, p < 0.0001) compared to the control subjects, while the right sylvian fissure length was unchanged. Sylvian fissure asymmetry (left/right ratio) was more reduced in male schizophrenics ( - 24%, p < 0.001) than in female patients ( - 16%, p < 0.03). This finding is consistent with several post-mortem and MRI studies showing left temporal lobe pathology in a significant proportion of patients and may indicate that schizophrenia is a disorder of early neurodevelopment causing impaired cerebral lateralization.

Loss of sylvian fissure asymmetry in schizophrenia: Findings in the runwell 2 series of brains

Objective: Several studies have suggested the existence of thalamic volume reduction in patients with schizophrenia. However, the precise locus of volume reduction within the thalamus has scarcely been investigated. On the other hand, underdevelopment of the adhesio interthalamica [AI; Danos, P., Baumann, B., Kramer, A., Bernstein, H.G., Stauch, R., Krell, D., Falkai, P., Bogerts, B., 2003. Volumes of association thalamic nuclei in schizophrenia: a post-mortem study. Schizophr. Res. 60 141–155], which bridges bilateral medial edges of the thalamus, has been reported in patients with schizophrenia. We assessed the volumes of mediodorsal nuclei (MDN) of thalami, level of AI development, and their interrelationship, in patients with schizophrenia. Method: A sample of 58 patients with schizophrenia and 44 matched healthy volunteers underwent assessment with high-resolution 1-mm-thick anatomical MRI. Volume measurements of the MDN of the thalamus and whole thalamus were performed by manual tracing. The level of AI development was quantitatively defined as the maximal anterior-to-posterior length of the AI. Results: Schizophrenia patients had significantly smaller volumes of bilateral MDN. AI ratings were twice as high in women than in men among the control subjects; however, no gender difference emerged in the schizophrenia group due to reduced ratings in female patients. No significant correlation was found between MDN volumes and AI ratings among both groups. Conclusions: These results provide evidence of volume reduction of the MDN, and female-specific underdevelopment of the AI in schizophrenia. As we did not demonstrate a relationship between MDN volume and AI ratings, it is suggested that these two measures of medial thalamic abnormality are manifestations of different neuropathological processes in schizophrenia patients.

Anatomical Asymmetries in the Adult and Developing Brain and their Implications for Function

The left cerebral hemisphere is dominant for language function. Thus, lesions involving this hemisphere in children and adults are more likely to cause disorders in language function than the same or even larger lesions in the opposite hemisphere. Lesions that interfere with language tend to be clustered around the Sylvian fissure. Two regions appear to be especially important: one in the posterior frontal opercular area, the other in the posterior third of the superior temporal gyrus and adjacent parietal operculum. Lesions in other language regions that occupy more posterior portions of the inferior parietal lobule appear to result in disorders of written language; supplementary motor and sensory areas located on the medial portion of the left hemisphere surrounding the cingulate gyrus appear to influence spontaneous language activity. Finally, lesions in the left posterior pulvinar may also produce short-lived aphasic disturbances. The brain exhibits both gross anatomical and microscopic asymmetries in the region of the language areas. Sylvian fissure asymmetries suggest a greater development of the posterior temporal region and of the parietal operculum on the left. The greater development of the left posterior temporal region is also illustrated by a larger posterior upper surface (planum temporale) on that side. Furthermore, the anterior speech area on the frontal operculum may be more convoluted and therefore larger on the left. Asymmetries in the Sylvian fissures and in the relative widths of portions of the hemispheres can be demonstrated during life by radiologic means. Gross anatomical asymmetries appear to reflect side differences in areas of distinctive microscopic structure (architectonic areas) and function. Thus, in the posterior speech area the auditory field Tpt is larger on the left, and in the frontal lobe an opercular motor field is also larger on the left. Area 39, an inferior parietal association cortex, may be thicker on the left side, and its corresponding thalamic projection nucleus, nucleus lateralis posterior, is also larger on the left. The normally occurring asymmetry may be altered in pathology and pathological lesions may be asymmetrically distributed. Thus, the analysis of a brain of a dyslexic patient has disclosed an abnormally large left hemisphere as well as cortical malformations restricted to the left side of the brain. Later-alized abnormalities may occur in other disease entities and may be linked to genetic abnormalities, as evidenced by the familial occurrence of some dyslexias as well as of similar brain malformations. On the other hand, lateralized abnormalities may result from early lesions, as illustrated by limb malformations in rats and reversals of habenular asymmetries in newts. Lateralized limb malformations with a male preponderance also occur in man, although genetic or environmental factors have not been identified. Finally, lateralized malformations in fiber connectivities may be the result of early lesions in the brain, as shown by experimental data from fetal monkeys and newborn hamsters. Thus, knowledge of functional and structural lateralization of the human brain has begun to play an increasingly important role in our understanding of the neurologic bases of normal language function and of some disorders of functional lateralization of which developmental dyslexia is an example. Future improvements in the anatomical model of language and related functions will come from additional studies of anatomical lateralization. It is likely that anatomical lateralization results from genetic and prenatal environmental influences, and that a clearer picture of the factors leading to normal and abnormal manifestations of asymmetry will come from animal models of lateralization. Until recently, lateralization in function has been thought to be an exclusively human trait. However, animal models appear to be emerging with the discovery of functional lateralization in rats35, 67 and monkeys.61 Furthermore, the effects of early lesions on recovery and laterality are under current investigation in these animal models.36, 66 Finally, the possible identification of intrauterine environmental insults leading in some manner to abnormalities in lateralization of structure and function provide additional hope for improvement of our ability to prevent and treat disorders of brain asymmetry.