Premotor Cortex 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 Premotor Cortex (PMC), also known as Brodmann area 6 (lateral part), is a critical region of the frontal lobe located anterior to the primary motor cortex, on the lateral surface of the frontal gyrus. The PMC is fundamentally involved in movement planning, the selection of motor programs based on sensory cues, the guidance of movements through visual and somatosensory feedback, and higher-order motor functions including action understanding through mirror neuron activity [1][2]. This cortical region is significantly impacted in neurodegenerative diseases such as Parkinson's disease (PD), where it contributes to bradykinesia and movement selection deficits, and in Alzheimer's disease (AD), where it underlies apraxia and motor planning impairments.
¶ Anatomy and Location
The premotor cortex occupies the lateral portion of Brodmann area 6 [3]:
- Anterior boundary: Prefrontal cortex (BA 8, 9, 44, 45)
- Posterior boundary: Primary motor cortex (BA 4)
- Superior boundary: Superior frontal gyrus, dorsal premotor area
- Inferior boundary: Inferior frontal gyrus, opercular region
- Lateral boundary: Lateral cortical surface
The PMC has distinct laminar organization:
- Layer III: Medium pyramidal neurons, intracortical connections
- Layer V: Large pyramidal neurons, output to subcortical structures
- Prominent layer IV: Receives sensory inputs
- Columnar organization: Functional modules
The premotor cortex comprises several functional subregions:
| Region |
Function |
| Dorsal premotor cortex (PMd) |
Spatial selection, arbitrary mappings |
| Ventral premotor cortex (PMv) |
Object manipulation, action understanding |
| Area F5 (monkey) |
Mirror neurons, hand actions |
Major inputs:
- Primary motor cortex
- Supplementary motor area
- Posterior parietal cortex (BA 5, 7)
- Prefrontal cortex
- Basal ganglia (via thalamus)
- Cerebellum (via thalamus)
- Superior temporal sulcus
Major outputs:
- Primary motor cortex (cortico-cortical)
- Corticospinal tract (via M1)
- Corticostriatal projections
- Brainstem motor nuclei
Glutamate (excitatory):
- Primary excitatory neurotransmitter
- NMDA and AMPA receptors
- Critical for motor learning and plasticity
GABA (inhibitory):
- Local interneuron inhibition
- Shapes motor commands
- Prevents unwanted movements
| Receptor Type |
Distribution |
Function |
| NMDA |
Pyramidal neurons |
Synaptic plasticity |
| AMPA |
Widespread |
Fast excitation |
| GABA-A |
Interneurons |
Inhibition |
| D1 Dopamine |
Layer III, V |
Motor learning |
| D2 Dopamine |
Layer I, II |
Motor suppression |
- Dopamine: From ventral tegmental area, modulates motor learning
- Noradrenaline: From locus coeruleus, attention to sensory cues
- Serotonin: From dorsal raphe, mood and motivation
- Acetylcholine: From basal forebrain, learning and attention
¶ Function and Motor Control
The PMC is crucial for translating motor intentions into concrete motor plans [2][4]:
- Sensory guidance: Uses visual, auditory, and somatosensory information
- Movement selection: Chooses among possible actions based on context
- Motor schemas: Retrieves appropriate motor programs
- Coordinate transformations: Converts sensory coordinates to motor coordinates
The PMC performs critical coordinate transformations:
- Visual space to motor space: Where to reach
- Object-centered coordinates: How to grasp
- Body-centered coordinates: Which limb to use
The ventral premotor cortex contains mirror neurons [1][5]:
Properties:
- Fire when performing an action
- Fire when observing the same action
- Code action goals, not muscle movements
Functions:
- Action understanding
- Motor imitation
- Social cognition
- Language evolution (theories)
Unlike the SMA (internally-cued movements), the PMC:
- Responds to external sensory cues
- Adapts to changing conditions
- Uses feedback for corrections
The PMC contributes to motor learning:
- Arbitrary sensorimotor mappings
- Novel skill acquisition
- Error-based learning
- Reward-based learning
- Set-related activity: Activity during motor planning
- Movement-related activity: Activity during execution
- Neuronal selectivity: For specific directions, objects, contexts
| Frequency |
Function |
| Beta (15-30 Hz) |
Movement suppression, maintenance |
| Gamma (40-100 Hz) |
Movement preparation, execution |
| Alpha (8-12 Hz) |
Sensory gating |
- Visual: Large receptive fields in posterior parietal input
- Somatosensory: Body-part specific
- Multimodal integration: Combines multiple modalities
PMC dysfunction in PD contributes to multiple symptoms [6][7]:
Movement Selection Deficits:
- Difficulty selecting appropriate movements
- Over-reliance on external cues
- Reduced spontaneous movement
Bradykinesia:
- Reduced premotor activity
- Impaired motor preparation
- Dopaminergic deficiency effects
Freezing of Gait:
- Failure to initiate gait
- Cue-dependent improvement
- PMC hypometabolism
Treatment Effects:
- Levodopa improves PMC function
- Visual cues compensate for PMC deficits
- Deep brain stimulation modulates PMC
PMC involvement in AD [8]:
Apraxia:
- Loss of learned motor programs
- Ideomotor apraxia
- Limb kinetic apraxia
Motor Planning Deficits:
- Impaired movement selection
- Reduced planning activity
- Early cortical dysfunction
Neuroimaging:
- Glucose hypometabolism
- Cortical atrophy
- Connectivity disruption
- Impaired movement selection
- Reduced PMC activation
- Motor timing deficits
- PMC lesions cause apraxia
- Impairs sensory-guided movements
- Recovery involves PMC reorganization
- Axial rigidity
- Gait initiation failure
- Oculomotor deficits
The PMC learns arbitrary relationships:
- Stimulus-response pairs
- Context-dependent actions
- Novel tool use
- Compares expected and actual outcomes
- Adjusts motor commands
- Uses sensory prediction errors
- Reinforces successful actions
- Modulates synaptic strength
- Dopamine-dependent
| Method |
Application |
| fMRI |
Localize activity during tasks |
| PET |
Metabolic mapping |
| TMS |
Disruption studies |
| EEG/MEG |
Temporal dynamics |
- Single-unit recording in primates
- Surface EEG in humans
- Intracranial EEG in patients
- Reaching tasks: Visuomotor transformations
- Object manipulation: Grasp planning
- Mirror tasks: Action understanding
- Conditional learning: Arbitrary mappings
- Dopamine agonists: Improve PMC function in PD
- Levodopa: Normalizes activity
- Cholinesterase inhibitors: May help cortical function
- Deep brain stimulation: Modulates PMC via basal ganglia
- Motor cortex stimulation: For PD and stroke
- Constraint-induced movement therapy: Forces PMC use
- Mirror therapy: Uses mirror neuron system
- Virtual reality: Rich sensory environments
- tDCS: Modulate PMC excitability
- Brain-computer interfaces: Neural prosthetics
- Robotic rehabilitation: Intensive training
- Gene therapy: Neuroprotection
[1] Rizzolatti et al., Premotor cortex and recognition (1996)
[2] Plotnik et al., Premotor cortex in Parkinson's disease (2008)
[3] Brodmann, Localisation in the cerebral cortex (1909/2006)
[4] Wise, Motor area of the cerebral cortex (1985)
[5] Gallese et al., Action recognition in the premotor cortex (1996)
[6] Jahanshahi et al., Self-initiated versus externally-cued movements in PD (2000)
[7] Thobois et al., Premotor dysfunction in PD (2000)
[8] Morrison & Hof, Changes in motor cortex in AD (2007)
Premotor Cortex 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 Premotor Cortex 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.
- Rizzolatti G, et al. Premotor cortex and the recognition of motor actions. Brain Res Cogn Brain Res. 1996;3(2):131-141. PMID:8713354
- Hoshi E, Tanji J. Distinctions between dorsal and ventral premotor areas: anatomical connectivity and functional properties. Curr Opin Neurobiol. 2007;17(2):234-242. PMID:17314052
- Toni I, et al. Movement preparation and motor intention. Neuroimage. 2001;14(2):S110-S117. PMID:11373172
- Kurata K, Hoshi E. Reappraising the cortical motor areas. Cereb Cortex. 2009;19(9):2015-2026. PMID:19150975
- Davare M, et al. Functional organization of primary motor cortex. Handb Clin Neurol. 2010;95:37-49. PMID:20189176