Structural analysis of the primary somatosensory digit area in the human postcentral gyrus
Poster No:
1721
Submission Type:
Abstract Submission
Authors:
Anna Muellen1,2, Renate Schweizer1
Institutions:
1Functional Imaging Laboratory, German Primate Center, Goettingen, Germany, 2University of Goettingen, Goettingen, Germany
First Author:
Anna Muellen
Functional Imaging Laboratory, German Primate Center|University of Goettingen
Goettingen, Germany|Goettingen, Germany
Functional Imaging Laboratory, German Primate Center|University of Goettingen
Goettingen, Germany|Goettingen, Germany
Co-Author:
Introduction:
The primary somatosensory cortex (S1) in the postcentral gyrus and the primary motor cortex (M1) in the precentral gyrus are evolutionarily conserved cortical regions, where first-level input of afferent somatosensory information and last-level output of efferent motor information take place. Both S1 and M1 display a somatotopic organization with a comparably large cortical representation of the highly innervated hand and digits (Penfield & Boldrey, 1937). For M1, a knob-like structure at the superomedial third of the precentral gyrus, the hand knob, has been previously described as an anatomical landmark for the individual M1 hand area (Yousry, 1997). For S1, however, there are currently no macroscopic structures known to relate to the individual S1 digit area. The present study thus aims to identify anatomical landmarks for the tactile S1 digit area: Since the tactile S1 digit area of Brodmann Area (BA) 3b is located at the anterior front of the postcentral gyrus (Schweizer et al., 2008) and within the central sulcus (CS), the CS of >1000 subjects were first screened for potential landmarks. Second, a method was devised to extract and characterize candidate landmarks. Finally, suitable candidates within the CS were related to the anatomical layout of the anterior postcentral gyrus.
Methods:
Raw T1-weighted magnetic resonance imaging data (n = 1112 subjects) of the Human Connectome Project S1200 Data Release were downloaded and preprocessed (BrainVISA 4.6.0). Reconstructions of cortical grey and white matter and cortical sulci were obtained. Cortical sulci were computed as cortical fold graphs (CFGs) following the median plane of all sulci (Morphologist 2015). For each hemisphere of all subjects, CFGs of the CS were manually identified to obtain CS reconstructions and parametrizations (Sulcus Parametrization 2015) resulting in each a CS mesh (Fig. 1A), its depth profile, and its deflection profile (Fig. 1B). The depth profile thereby approximates the CS depth from surface to fundus at 101 discrete positions between the CS' medial start at the interhemispheric cleft (position: 0) and its lateral end at the lateral sulcus (position: 100). The deflection profile approximates the CS deviations towards anterior and posterior at the same positions.
Results:
Based on 2165 depth and deflection profiles, a method was devised (R, Version 4.2.2) to extract two macroscopic structures in the vicinity of the S1/BA3b digit area: From depth profiles, the pli-de-passage fronto-pariétal moyen (PPfpm), a deep annectant gyrus at the CS fundus (Cunningham, 1839), was extracted at its lateral end (PPfpm-II: deepest minimum at position > 45) and its peak height (PPfpm-I: maximum medially adjacent to PPfpm-II) (Fig. 1B, left). From deflection profiles, the hand knob was extracted as a posterior deflection following fast Fourier transformation (k ∈ ℤ | 0 ≤ k ≤ 50) and band pass filtering (2 ≤ k ≤ 9) (Fig. 1B, right). The PPfpm was found to be present across all subjects with an average height of 4.5 ± 2.7 mm. The PPfpm's lateral end (PPfpm-II) is stable across hemispheres and subjects at position 60.8 ± 5.1, and identical to the CS' deepest point in 96% of all data. A close association between PPfpm-II and a deflection marking the hand knob's lateral end, referred to as the lateral protrusion, is indicated. Translation of these findings to the 3D anatomy of the anterior postcentral gyrus as given per high-quality cortical reconstructions (FreeSurfer) revealed a match with corresponding macroscopic structures, i.e. the PPfpm and a usually distinct protrusion of the postcentral gyrus opposite of the hand knob.
Conclusions:
In conclusion, the present study offers a detailed description of the anatomical layout of the anterior postcentral gyrus. Three structures were identified as potential anatomical landmarks for the S1/BA3b digit area. Future work will focus on the direct extraction of the described structures from the anterior postcentral gyrus.
Modeling and Analysis Methods:
Image Registration and Computational Anatomy
Neuroanatomy, Physiology, Metabolism and Neurotransmission:
Anatomy and Functional Systems
Cortical Anatomy and Brain Mapping 1
Neuroanatomy Other 2
Keywords:
Cortex
Data analysis
MRI
Somatosensory
STRUCTURAL MRI
Other - central sulcus; postcentral gyrus
1|2Indicates the priority used for review
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2. Penfield, W., & Boldrey, E. (1937). Somatic motor and sensory representation in the cerebral cortex of man as studied by electrical stimulation. Brain, 60(4), 389–443.
3. Schweizer, R., Voit, D., & Frahm, J. (2008). Finger representations in human primary somatosensory cortex as revealed by high-resolution functional MRI of tactile stimulation. NeuroImage, 42(1), 28–35.
4. Yousry, T. (1997). Localization of the motor hand area to a knob on the precentral gyrus. A new landmark. Brain, 120(1), 141–157.