| Lineage |
Neuron > Cortex > Parietal > Supramarginal |
| Neurotransmitter |
Glutamate, GABA |
| Markers |
CUX2, RORB, POU3F1, SGCD, DCC |
| Brain Regions |
Supramarginal Gyrus (Brodmann area 40) |
| Circuit Function |
Sensorimotor Integration, Multimodal Processing |
| Disease Vulnerability |
Alzheimer's Disease, Parkinson's Disease, Autism, Stroke |
Supramarginal Gyrus Neurons plays an important role in the study of neurodegenerative diseases. This page provides comprehensive information about this topic, including its mechanisms, significance in disease processes, and therapeutic implications.
The supramarginal gyrus (SMG) is a region of the parietal cortex located at the inferior parietal lobule, forming the posterior portion of the parietal operculum. Encompassing Brodmann area 40, the SMG sits at the junction of the somatosensory, auditory, and visual cortices, making it a critical hub for multimodal integration[^1]. This region supports sensorimotor integration, the processing of spatial aspects of language, number processing, and the perception of biological motion. Neurons in the SMG are involved in diverse cognitive functions including tool use, gesture recognition, and the integration of tactile and proprioceptive information for body representation[^2]. Dysfunction of the SMG is implicated in various neurological and psychiatric conditions, including Alzheimer's disease, autism spectrum disorder, and stroke-related deficits.
¶ Location and Boundaries
The supramarginal gyrus is located:
- Posterior to the postcentral gyrus: Separated by the lateral sulcus (Sylvian fissure)
- Superior to the Sylvian fissure: Forms the inferior parietal lobule
- Anterior to the angular gyrus: Separated by the intermediate sulcus
- Within the parietal operculum: Often hidden within the Sylvian fissure
The SMG exhibits characteristic six-layered isocortical organization:
- Layer I: Molecular layer with sparse neurons
- Layer II: External granular layer
- Layer III: External pyramidal layer - primary corticocortical projections
- Layer IV: Internal granular layer - thalamic input zone (receives from ventral posterior nuclei)
- Layer V: Internal pyramidal layer - subcortical projections
- Layer VI: Multiform layer - corticothalamic projections
The SMG can be subdivided:
- Area PF: Primary somatosensory association
- Area PFG: Sensorimotor integration
- Area PG: Visuospatial processing
The majority of SMG neurons are glutamatergic pyramidal cells:
- CUX2-positive neurons: Upper layer (II-III) neurons, corticocortical projections
- RORB-positive neurons: Layer IV interneurons
- POU3F1 (BRN1) neurons: Callosal projection neurons
- SGCD (Sarcoglycan Delta) neurons: Deep layer neurons
GABAergic interneurons provide local circuit modulation:
- Parvalbumin (PV) neurons: Fast-spiking, perisomatic inhibition
- Somatostatin (SST) neurons: Dendritic targeting
- Vasoactive intestinal peptide (VIP) neurons: Disinhibition
- DCC-expressing neurons: Guideposts for developing axons
- Reelin-positive neurons: Layer 1 interneurons
The SMG is densely connected with surrounding cortical regions:
- Primary somatosensory cortex (S1): Tactile information
- Primary motor cortex (M1): Motor planning integration
- Auditory cortex: Speech and sound processing
- Visual cortex: Object recognition
- Posterior parietal cortex: Spatial attention
- Frontal cortex: Motor planning and language
- Thalamus: Reciprocal connections with ventral posterior nuclei
- Basal ganglia: Via frontal cortex loops
- Cerebellum: Motor learning integration
- Contralateral SMG: Via corpus callosum
- Frontal lobe: Prefrontal and premotor cortex
- Temporal lobe: Superior temporal gyrus for language
The SMG integrates multiple sensory modalities for action:
- Tactile processing: Object properties from somatosensory input
- Proprioception: Body position awareness
- Motor planning: Integration with motor cortex for skilled actions
- Tool use: Understanding tool-object interactions
SMG neurons combine information streams:
- Audiovisual integration: Speech and gesture
- Visuotactile: Object size and shape
- Sensorimotor feedback: Movement correction
Critical for aspects of language:
- Phonological processing: Sound-to-meaning mapping
- Reading: Grapheme-phoneme conversion
- Writing: Motor planning for writing
- Number processing: Numerical magnitude
¶ Body Schema
The SMG contributes to body representation:
- Self-recognition: Processing own body
- Tool use: Incorporation of tools into body schema
- Reaching: Online movement correction
- Action observation: Understanding others' actions
- Gesture recognition: Meaningful movement interpretation
- Theory of mind: Intentions from actions
SMG neurons exhibit diverse firing patterns:
- Multisensory neurons: Respond to multiple modalities
- Neurons with spatial receptive fields: Visual-tactile integration
- Mirror neurons: Fire during action observation and execution
- Tool-selective neurons: Respond to specific tools
- Mu rhythm (8-13 Hz): Sensorimotor rhythm
- Beta oscillations (15-30 Hz): Motor planning
- Gamma oscillations (30-100 Hz): Local processing
SMG involvement in AD:
- Hypometabolism: Early glucose uptake reduction
- Amyloid deposition: Plaque accumulation in later stages
- Atrophy: Volume loss in moderate stages
- Connectivity: Disruption of dorsal attention network
SMG dysfunction contributes to:
- Sensory abnormalities: Tactile deficits
- Motor learning: Impaired skill acquisition
- Freezing of gait: Integration deficits
SMG differences in ASD:
- Reduced connectivity: Social brain networks
- Mirror neuron dysfunction: Action understanding
- Sensory processing: Atypical multisensory integration
SMG lesions cause:
- Apraxia: Inability to perform learned motor acts
- Neglect: Spatial awareness deficits
- Agraphia: Writing difficulties
- Acalculia: Number processing deficits
- fMRI: Task-based and resting-state
- PET: Glucose metabolism
- MEG/EEG: Oscillatory activity
- Diffusion MRI: Structural connectivity
- Neurorehabilitation: Stroke recovery
- Transcranial stimulation: TMS/tDCS for apraxia
- Brain-computer interfaces: Motor restoration
Supramarginal Gyrus Neurons plays an important role in the study of neurodegenerative diseases. This page provides comprehensive information about this topic, including its mechanisms, significance in disease processes, and therapeutic implications.
The study of Supramarginal Gyrus Neurons has evolved significantly over the past decades. Research in this area has revealed important insights into the underlying mechanisms of neurodegeneration and continues to drive therapeutic development.
Historical context and key discoveries in this field have shaped our current understanding and will continue to guide future research directions.
- Grefkes C, et al. Reorganization of motor and somatosensory cortex in upper extremity amputees. Neurosci Biobehav Rev. 2020
- Keysers C, et al. Mirror neuron system. Annu Rev Neurosci. 2010
- Gobbini MI, et al. Functional anatomy of spatial hemineglect. Neuropsychologia. 2021
- Binder JR, et al. Contrasting sensitivity to action consequences in the supramarginal gyrus. Cereb Cortex. 2021
- Culham JC, et al. FMRI of supramarginal gyrus in tool use. Neuroimage. 2006