Premotor Cortex

Premotor Cortex

<table class="infobox infobox-cell">
<tr>
<th class="infobox-header" colspan="2">Premotor Cortex</th>
</tr>
<tr>
<td class="label">Region</td>
<td>Function</td>
</tr>
<tr>
<td class="label">Dorsal premotor cortex (PMd)</td>
<td>Spatial selection, arbitrary mappings</td>
</tr>
<tr>
<td class="label">Ventral premotor cortex (PMv)</td>
<td>Object manipulation, action understanding</td>
</tr>
<tr>
<td class="label">Area F5 (monkey)</td>
<td>Mirror neurons, hand actions</td>
</tr>
<tr>
<td class="label">Receptor Type</td>
<td>Distribution</td>
</tr>
<tr>
<td class="label">NMDA</td>
<td>Pyramidal neurons</td>
</tr>
<tr>
<td class="label">AMPA</td>
<td>Widespread</td>
</tr>
<tr>
<td class="label">GABA-A</td>
<td>Interneurons</td>
</tr>
<tr>
<td class="label">D1 Dopamine</td>
<td>Layer III, V</td>
</tr>
<tr>
<td class="label">D2 Dopamine</td>
<td>Layer I, II</td>
</tr>
<tr>
<td class="label">Frequency</td>
<td>Function</td>
</tr>
<tr>
<td class="label">Beta (15-30 Hz)</td>
<td>Movement suppression, maintenance</td>
</tr>
<tr>
<td class="label">Gamma (40-100 Hz)</td>
<td>Movement preparation, execution</td>
</tr>
<tr>
<td class="label">Alpha (8-12 Hz)</td>
<td>Sensory gating</td>
</tr>
<tr>
<td class="label">Method</td>
<td>Application</td>
</tr>
<tr>
<td class="label">fMRI</td>
<td>Localize activity during tasks</td>
</tr>
<tr>
<td class="label">PET</td>
<td>

...

Premotor Cortex

<table class="infobox infobox-cell">
<tr>
<th class="infobox-header" colspan="2">Premotor Cortex</th>
</tr>
<tr>
<td class="label">Region</td>
<td>Function</td>
</tr>
<tr>
<td class="label">Dorsal premotor cortex (PMd)</td>
<td>Spatial selection, arbitrary mappings</td>
</tr>
<tr>
<td class="label">Ventral premotor cortex (PMv)</td>
<td>Object manipulation, action understanding</td>
</tr>
<tr>
<td class="label">Area F5 (monkey)</td>
<td>Mirror neurons, hand actions</td>
</tr>
<tr>
<td class="label">Receptor Type</td>
<td>Distribution</td>
</tr>
<tr>
<td class="label">NMDA</td>
<td>Pyramidal neurons</td>
</tr>
<tr>
<td class="label">AMPA</td>
<td>Widespread</td>
</tr>
<tr>
<td class="label">GABA-A</td>
<td>Interneurons</td>
</tr>
<tr>
<td class="label">D1 Dopamine</td>
<td>Layer III, V</td>
</tr>
<tr>
<td class="label">D2 Dopamine</td>
<td>Layer I, II</td>
</tr>
<tr>
<td class="label">Frequency</td>
<td>Function</td>
</tr>
<tr>
<td class="label">Beta (15-30 Hz)</td>
<td>Movement suppression, maintenance</td>
</tr>
<tr>
<td class="label">Gamma (40-100 Hz)</td>
<td>Movement preparation, execution</td>
</tr>
<tr>
<td class="label">Alpha (8-12 Hz)</td>
<td>Sensory gating</td>
</tr>
<tr>
<td class="label">Method</td>
<td>Application</td>
</tr>
<tr>
<td class="label">fMRI</td>
<td>Localize activity during tasks</td>
</tr>
<tr>
<td class="label">PET</td>
<td>Metabolic mapping</td>
</tr>
<tr>
<td class="label">TMS</td>
<td>Disruption studies</td>
</tr>
<tr>
<td class="label">EEG/MEG</td>
<td>Temporal dynamics</td>
</tr>
</table>

Overview

Premotor [Cortex](/brain-regions/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.

Introduction

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](/diseases/parkinsons-disease) (PD), where it contributes to bradykinesia and movement selection deficits, and in [Alzheimer's disease](/diseases/alzheimers-disease) (AD), where it underlies apraxia and motor planning impairments. [@hoshi2007]

Anatomy and Location

Anatomical Position

The premotor cortex occupies the lateral portion of Brodmann area 6 [3]: [@toni2001]

• 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

Cytoarchitecture

The PMC has distinct laminar organization: [@kurata2009]

• Layer III: Medium pyramidal [neurons](/entities/neurons), intracortical connections
• Layer V: Large pyramidal neurons, output to subcortical structures
• Prominent layer IV: Receives sensory inputs
• Columnar organization: Functional modules

Subdivisions

The premotor cortex comprises several functional subregions: [@davare2010]

Inputs and Outputs

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

Neurochemistry

Neurotransmitters

Glutamate (excitatory):

• Primary excitatory neurotransmitter
• [NMDA](/entities/nmda-receptor) and AMPA receptors
• Critical for motor learning and plasticity

GABA (inhibitory):

• Local interneuron inhibition
• Shapes motor commands
• Prevents unwanted movements

Receptor Expression

Neuromodulators

• Dopamine: From ventral tegmental area, modulates motor learning
• Noradrenaline: From locus coeruleus, attention to sensory cues
• Serotonin: From dorsal raphe, mood and motivation
• [Acetylcholine](/entities/acetylcholine): From basal forebrain, learning and attention

Function and Motor Control

Movement Planning

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

Visuomotor Transformations

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

Mirror Neuron System

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)

Sensory Guidance

Unlike the SMA (internally-cued movements), the PMC:

• Responds to external sensory cues
• Adapts to changing conditions
• Uses feedback for corrections

Motor Learning

The PMC contributes to motor learning:

• Arbitrary sensorimotor mappings
• Novel skill acquisition
• Error-based learning
• Reward-based learning

Electrophysiology

Neural Activity

• Set-related activity: Activity during motor planning
• Movement-related activity: Activity during execution
• Neuronal selectivity: For specific directions, objects, contexts

Oscillations

Receptive Fields

• Visual: Large receptive fields in posterior parietal input
• Somatosensory: Body-part specific
• Multimodal integration: Combines multiple modalities

Disease Connections

Parkinson's Disease

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

Alzheimer's Disease

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

Huntington's Disease

• Impaired movement selection
• Reduced PMC activation
• Motor timing deficits

Stroke

• PMC lesions cause apraxia
• Impairs sensory-guided movements
• Recovery involves PMC reorganization

Progressive Supranuclear Palsy

• Axial rigidity
• Gait initiation failure
• Oculomotor deficits

Motor Learning Mechanisms

Arbitrary Mappings

The PMC learns arbitrary relationships:

• Stimulus-response pairs
• Context-dependent actions
• Novel tool use

Error-Based Learning

• Compares expected and actual outcomes
• Adjusts motor commands
• Uses sensory prediction errors

Reward-Based Learning

• Reinforces successful actions
• Modulates synaptic strength
• [Dopamine](/mechanisms/dopaminergic-signaling)dependent

Research Methods

Neuroimaging

Electrophysiology

• Single-unit recording in primates
• Surface EEG in humans
• Intracranial EEG in patients

Behavioral Paradigms

• Reaching tasks: Visuomotor transformations
• Object manipulation: Grasp planning
• Mirror tasks: Action understanding
• Conditional learning: Arbitrary mappings

Therapeutic Approaches

Pharmacological

• Dopamine agonists: Improve PMC function in PD
• Levodopa: Normalizes activity
• [Cholinesterase inhibitors](/entities/cholinesterase-inhibitors): May help cortical function

Surgical

• Deep brain stimulation: Modulates PMC via basal ganglia
• Motor cortex stimulation: For PD and stroke

Rehabilitation

• Constraint-induced movement therapy: Forces PMC use
• Mirror therapy: Uses mirror neuron system
• Virtual reality: Rich sensory environments
• tDCS: Modulate PMC excitability

Emerging

• Brain-computer interfaces: Neural prosthetics
• Robotic rehabilitation: Intensive training
• Gene therapy: Neuroprotection

Key Publications

[1] [Rizzolatti et al., Premotor cortex and recognition (1996)](https://pubmed.ncbi.nlm.nih.gov/8788440/)

[2] [Plotnik et al., Premotor cortex in Parkinson's disease (2008)](https://pubmed.ncbi.nlm.nih.gov/18372449/)

[3] [Brodmann, Localisation in the cerebral cortex (1909/2006)](https://pubmed.ncbi.nlm.nih.gov/17148446/)

[4] [Wise, Motor area of the cerebral cortex (1985)](https://pubmed.ncbi.nlm.nih.gov/3906687/)

[5] [Gallese et al., Action recognition in the premotor cortex (1996)](https://pubmed.ncbi.nlm.nih.gov/8788441/)

[6] [Jahanshahi et al., Self-initiated versus externally-cued movements in PD (2000)](https://pubmed.ncbi.nlm.nih.gov/10719850/)

[7] [Thobois et al., Premotor dysfunction in PD (2000)](https://pubmed.ncbi.nlm.nih.gov/10719852/)

[8] [Morrison & Hof, Changes in motor cortex in AD (2007)](https://pubmed.ncbi.nlm.nih.gov/17531956/)

Overview

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.

Background

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.

External Links

• [Human Connectome Project - Motor Networks](https://www.humanconnectome.org/)
• [Allen Brain Atlas - Frontal Lobe](https://brain-map.org/)
• [Michael J. Fox Foundation - PD Research](https://www.michaeljfox.org/)
• [Alzheimer's Association - Research](https://www.alz.org/)
• [PubMed - Premotor Cortex](https://pubmed.ncbi.nlm.nih.gov/?term=premotor+cortex+motor+planning+neurodegeneration)

References

davare2010, Functional organization of primary motor cortex (2010)
hoshi2007, Distinctions between dorsal and ventral premotor areas: anatomical connectivity and functional properties (2007)
kurata2009, Reappraising the cortical motor areas (2009)
rizzolatti1996, Premotor cortex and the recognition of motor actions (1996)
toni2001, Movement preparation and motor intention (2001)

Pathway Diagram

The following diagram shows the key molecular relationships involving Premotor Cortex discovered through SciDEX knowledge graph analysis: