Structure of the human sensorimotor system. II: Lateral symmetry

White, Leonard; Andrews, Timothy J.; Hulette, Christine M.; Richards, Andrew; Groelle, M; Paydarfar, Joseph A.; Purves, Dale

doi:10.1093/cercor/7.1.31

Cited by 99 publications

(71 citation statements)

References 48 publications

(51 reference statements)

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“…In the current study we found that there was a larger volume of activation in the left motor cortex compared to the right, despite the fact that the anatomic volume of motor cortex did not differ between hemispheres across subjects. We should point out that we compared the total anatomic volume of the motor cortex in each hemisphere rather then the portion presumably related to arm movement as has been done in other studies (Amunts et al, 1996;White et al, 1997). The increased activation in the left motor cortex reached significance only in RH subjects; again this is consistent with previous work in which the dominance of the left motor cortex was most evident in RH subjects (Kim et al, 1993b).…”

Section: Hemisphere Dominance For Mo6ementsupporting

confidence: 85%

Effects of movement predictability on cortical motor activation

Dassonville

Lewis

Zhu

et al. 1998

Neuroscience Research

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Humans have the ability to make motor responses to unpredictable visual stimuli, and do so as a matter of course on a daily basis. We used functional magnetic resonance imaging (fMRI) to examine the neural substrate of this behavior in six cortical motor areas. We found that five of these areas (premotor, cingulate, supplementary motor area, pre-supplementary motor area, and superior parietal lobule) showed increased activation in association with an unpredictable behavior compared to a predictable one; only the motor cortex remained unchanged. There was also a quantitative relation between the response time and functional activation in the premotor and cingulate cortex. There was less activation across all the motor areas with repetition of the motor tasks. With the exception of the pre-supplementary motor area, all areas were significantly lateralized, with a greater volume of activation in the hemisphere contralateral to the performing hand. In addition, a left hemisphere dominance was found in the activation of motor cortex and supplementary motor areas. Our results suggest that activation in motor areas is differentially and quantitatively related to higher order aspects of motor behavior such as movement predictability.

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Section: Hemisphere Dominance For Mo6ementsupporting

confidence: 85%

Effects of movement predictability on cortical motor activation

Dassonville

Lewis

Zhu

et al. 1998

Neuroscience Research

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“…The posterior limit of the primary motor cortex (between Brodmann's areas 3a and 4) was more difficult to establish with precision, and in this study was placed where layer IV, which is clearly identified in area 3a, disappeared, and where the limit between the white and gray matter became blurred (White et al, 1997b). The anterior boundary of the primary motor cortex (between Brodmann's areas 4 and 6) was placed in the middle of a transitional zone where large pyramidal neurons begin to appear in layer III.…”

Section: Histologic Criteriamentioning

confidence: 85%

Stereologic characterization and spatial distribution patterns of Betz cells in the human primary motor cortex

et al. 2003

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Betz cells are giant motoneurons located in layer Vb of the primate primary motor cortex. We conducted stereological analyses of Betz cells and neighboring pyramidal cells from the brains of six neurologically normal elderly humans to determine their volume, total number, and spatial distribution, and to relate these data to functional localization. The distribution of cellular volumes exhibits a bimodal pattern, delineating two different subpopulations. Betz cell volumes follow a mediolateral gradient, the largest Betz cells being located on the most medial part of the motor cortex. Additionally, the shape of Betz cells varies between the rostral and caudal parts of the primary motor cortex, supporting the notion that there are anatomically distinct zones in primary motor cortex. The total number of Betz cells per hemisphere accounts for about one-tenth of the total number of pyramidal cells in layer Vb. Analysis of spatial distribution using Voronoi tessellation revealed maximal clustering of Betz cells in a zone situated two-thirds from the midline along the mediolateral axis of the primary motor cortex. These data suggest that Betz cells have a discrete subregional distribution that may correspond to certain aspects of the functional parcellation of area 4. These results may offer a histological correlate of functional imaging studies and are relevant in the context of neurodegenerative diseases such as amyotrophic lateral sclerosis, progressive supranuclear palsy, and Guamanian amyotrophic lateral sclerosis/Parkinsonism-dementia, and in studies of normal brain aging. Anat Rec Part A 270A: 137-151, 2003. © 2003 Key words: amyotrophic lateral sclerosis; area 4; Betz cells; cytoarchitecture; human neocortex; motoneurons; stereologyThe human neocortex is characterized by regional and laminar specific distributions of a variety of neuronal subtypes and distinct afferent and efferent connections. The neocortex can be parcellated into a large number of more or less distinct fields according to microscopic architecture. Identification of the primary motor cortex and its boundaries, however, has been particularly contentious. Brodmann (1903Brodmann ( , 1909 originally described area 4 as an agranular zone, delineated by the presence of Betz cells, a subpopulation of giant infragranular pyramidal neurons in cortical layer V, located on its rostral border and buried in the depth of the anterior wall of the central sulcus. This definition has since been criticized (Zeki, 1979), and Brodmann's original delineation of the primary motor cortex has been revised by other investigators, who described an intermediate precentral area, an area precentralis A, area

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“…Compared with wt (n ϭ 6), the size of the rostral motor domain is significantly reduced in TG (Ϫ34 Ϯ 1.7% ** , n ϭ 9), significantly increased in Eϩ/Ϫ (ϩ15 Ϯ 1.5% ** , n ϭ 6), and reverts towards wt in TG;Eϩ/Ϫ (Ϫ18 Ϯ 2.7% ** , n ϭ 9). Measurements were performed on whole mounts of cad8 in situ relatively modest changes in area size can have profound effects on behavioral performance, suggesting that in humans behavioral performance could differ substantially in relationship to the 2-fold size continuum reported for human cortical areas (1)(2)(3)(4)(5). We predict that a specific range of area size would result in optimal behavioral performance, and that this size range would be influenced by parameters of that area's neural system, some of which likely vary among individuals, particularly in out-bred populations.…”

Section: Discussionmentioning

confidence: 99%

“…In humans, the primary areas, motor (M1), somatosensory (S1), and visual (V1), vary Ϸ2-fold in size in a smooth continuum (1)(2)(3)(4)(5). In mice, the sizes of V1 and the S1 barrelfield are very consistent within inbred strains of mice, but their mean sizes can differ between some inbred strains of mice (6).…”

mentioning

confidence: 99%

Cortical area size dictates performance at modality-specific behaviors

Leingärtner

Thuret

Kroll

et al. 2007

Proc. Natl. Acad. Sci. U.S.A.

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The mammalian neocortex is organized into unique areas that serve functions such as sensory perception and modality-specific behaviors. The sizes of primary cortical areas vary across species, and also within a species, raising the question of whether area size dictates behavioral performance. We show that adult mice genetically engineered to overexpress the transcription factor EMX2 in embryonic cortical progenitor cells, resulting in reductions in sizes of somatosensory and motor areas, exhibit significant deficiencies at tactile and motor behaviors. Even increasing the size of sensorimotor areas by decreasing cortical EMX2 levels can lead to diminished sensorimotor behaviors. Genetic crosses that retain ectopic Emx2 transgene expression subcortically but restore cortical Emx2 expression to wild-type levels also restore cortical areas to wild-type sizes and in parallel restore tactile and motor behaviors to wild-type performance. These findings show that area size can dictate performance at modality-specific behaviors and suggest that areas have an optimal size, influenced by parameters of its neural system, for maximum behavioral performance. This study underscores the importance of establishing during embryonic development appropriate levels of regulatory proteins that determine area sizes, thereby influencing behavior later in life.cortex ͉ EMX2 ͉ sensorimotor performance ͉ cortical area patterning ͉ somatosensory cortex T he mammalian neocortex is tangentially organized into areas that serve unique functions such as sensory perception and modality-specific behaviors. In humans, the primary areas, motor (M1), somatosensory (S1), and visual (V1), vary Ϸ2-fold in size in a smooth continuum (1-5). In mice, the sizes of V1 and the S1 barrelfield are very consistent within inbred strains of mice, but their mean sizes can differ between some inbred strains of mice (6).These observations raise the question of whether the size of a cortical area influences behavioral performance. Normal humans exhibit significant differences in proficiency at visual psychophysical tasks (7), but these differences have not been correlated to differences in area size. Complementing these findings are studies of adult cortical plasticity. For example, repetitive use of a digit, or microstimulation of its cortical representation, results in an enlarged functional representation in M1 and S1 resulting in an increased overlap with functional representations of adjacent digits. These enlargements, which are evident physiologically but not anatomically, do not extend across area borders, do not increase area size, and have not been shown to affect systems-level behavior (8, 9).Here we address whether differences in cortical area size influence modality-specific behaviors in adults by using genetic manipulations that act during embryonic development to alter cortical area size in a consistent, reproducible manner. Establishing a relationship between area size and behavioral performance could be predictive for behavioral differences between ...

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Structure of the human sensorimotor system. II: Lateral symmetry

Cited by 99 publications

References 48 publications

Effects of movement predictability on cortical motor activation

Effects of movement predictability on cortical motor activation

Stereologic characterization and spatial distribution patterns of Betz cells in the human primary motor cortex

Cortical area size dictates performance at modality-specific behaviors

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