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Motor Planning: Premotor and Supplementary Motor Cortex

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125topics build on this

1,353prerequisites beneath it

Primary Motor Cortex and Motor Representation Primary Motor Cortex: Movement Planning and Execution +1 more→→Basal Ganglia: Action Selection and Habit Formation

Core Idea

Premotor cortex and supplementary motor cortex (SMA) plan and sequence motor actions before M1 execution. These regions integrate sensory information, motivational signals, and goal representations to select and organize movement sequences. Damage to premotor areas produces apraxia (inability to execute learned motor sequences) despite preserved M1 function, demonstrating the distinction between planning and execution.

Explainer

You already know that the primary motor cortex (M1) contains a topographic map of the body — stimulate a specific point and a specific muscle contracts. But knowing *which* muscles to recruit, in *what order*, and toward *what goal* requires more than M1. That preparatory work is the job of the premotor cortex (PMC) and supplementary motor area (SMA), two regions that sit just anterior to M1 and function as the choreographers of movement before execution begins.

Think of M1 as the orchestra playing the notes, and PMC/SMA as the conductor who has already decided the tempo, order, and phrasing. The SMA is particularly involved in self-initiated sequences — movements that arise from internal intention rather than external cues. When you decide to tap out a rhythm from memory, SMA is highly active even before movement begins; recording studies in monkeys and humans show a buildup of electrical activity called the readiness potential (Bereitschaftspotential) up to a second before the movement itself occurs. The PMC, by contrast, is more involved in externally guided actions, where a sensory cue (a visual target, a verbal instruction) triggers a learned response.

The clearest evidence that planning and execution are distinct comes from a neurological syndrome called apraxia. A patient with damage to premotor areas may have full muscular strength and intact M1 function — they can move their limbs — yet they cannot perform learned, purposeful sequences on command. Asked to pantomime using a toothbrush, they make fumbling, incoherent movements. The motor program itself exists in M1, but the system that assembles and dispatches it is disrupted. This dissociation maps cleanly onto the planning-versus-execution architecture: premotor damage breaks the plan; M1 damage breaks the execution. Your knowledge of the motor cortex's somatotopic organization makes this make sense — M1 knows *how* to fire muscle groups, but it needs upstream regions to tell it *when* and *in what sequence*.

Your soft prerequisite — dorsolateral prefrontal cortex and cognitive control — adds an important layer. DLPFC communicates goal representations (what you are trying to achieve) downward to premotor areas, which then translate those goals into motor sequences. This top-down connection explains why motor actions can be flexibly reorganized in novel contexts or overridden when goals change. The full motor hierarchy thus runs: DLPFC (goal) → PMC/SMA (plan and sequence) → M1 (execute) → spinal cord (muscle). Each stage converts a more abstract representation into a more concrete motor command, a principle called hierarchical motor control.

Practice Questions 5 questions

Prerequisite Chain

Understanding Zero → The Number Zero → Counting to Five → Counting to 10 → One-to-One Correspondence → Counting a Set of Objects Up to 20 → Cardinality: The Last Number Counted → Matching Numerals to Quantities → Subitizing Small Quantities → Addition Within 10 → Making 10 as an Addition Strategy → Addition Within 20 → Doubles and Near Doubles → Doubles Facts Within 10 → Near Doubles Facts Within 20 → Mental Math Strategies for Addition → Mental Math: Adding and Subtracting Tens → Addition Within 100 → Repeated Addition as Multiplication → Multiplication as Equal Groups → Multiplication: Arrays → Basic Multiplication Facts (0s, 1s, 2s, 5s, 10s) → Multiplication Facts Within 100 → Division as Equal Sharing → Division as Grouping (Measurement Division) → Division: Grouping (Repeated Subtraction) Model → Division: Fair Sharing Model → Division as Equal Sharing → Division as Grouping → Basic Division Facts → Division Facts Within 100 → Multiplication and Division Fact Families → Relationship Between Multiplication and Division → Division Facts as Inverse of Multiplication → Remainders and Quotients in Division → Division Word Problems → Multi-Step Word Problems → Solving Multi-Step Word Problems → Multiplication Word Problems → Division Word Problems → Introduction to Long Division → Factors and Multiples → Prime and Composite Numbers → Equivalent Fractions → Relating Fractions and Decimals → Decimal Place Value → Integers and the Number Line → Comparing and Ordering Integers → Absolute Value → Adding Integers → Subtracting Integers → Multiplying Integers → Dividing Integers → Unit Rates → Proportions → Percent Concept → Converting Between Fractions, Decimals, and Percents → Operations with Rational Numbers → Two-Step Equations → Solving Multi-Step Equations → Equations with Variables on Both Sides → Angle Pairs: Complementary, Supplementary, and Vertical → Parallel Lines and Transversals → Corresponding Angles → Alternate Interior Angles → Triangle Angle Sum Theorem → Exterior Angle Theorem → Triangle Inequality Theorem → Similar Triangles: AA Similarity → Similar Triangles: SSS and SAS Similarity → Proportions in Similar Triangles → Right Triangle Trigonometry Introduction → Sine, Cosine, and Tangent Ratios → Trigonometric Ratios Review → Radian Measure → Converting Between Degrees and Radians → The Unit Circle → Graphing Sine and Cosine → Graphing Tangent and Reciprocal Trigonometric Functions → Derivatives of Trigonometric Functions → Antiderivatives → Iterated Integrals and Fubini's Theorem → Double Integrals in Cartesian Coordinates → Double Integrals in Polar Coordinates → Double Integrals in Polar Coordinates → Double Integrals: Definition and Setup → Iterated Integrals and Fubini's Theorem → Double Integrals over Rectangular Regions → Double Integrals over General Regions → Applications of Double Integrals: Area, Mass, and Moments → Triple Integrals in Cartesian Coordinates → Triple Integrals in Cylindrical and Spherical Coordinates → Change of Variables and the Jacobian Determinant → Applications of Triple Integrals: Volume and Mass → Vector Fields and Their Representations → Line Integrals of Vector Fields → Work and Circulation → Line Integrals of Scalar and Vector Functions → Fundamental Theorem for Line Integrals → Conservative Vector Fields → Conservative Vector Fields and Potential Functions → Curl and Divergence of Vector Fields → Curl and Divergence → Divergence Theorem → Electric Flux and Divergence Theorem → Gauss's Law: Integral Form and Meaning → Solving Problems with Gauss's Law → Conductors in Electrostatic Equilibrium → Capacitance and Capacitors → Dielectrics → Dielectric Constant and Relative Permittivity → Electric Field Inside Dielectric Materials → Dielectric Materials and Polarization → Dielectric Susceptibility and Permittivity → Energy Density in Electric Fields → Electric Current and Current Density → Electrical Resistance and Resistivity → Ohm's Law and Circuit Elements → Electromotive Force (EMF) and Batteries → Kirchhoff's Circuit Laws: Voltage and Current → DC Circuit Network Analysis Methods → Transient Response in RC Circuits → RC Circuits → LC and RLC Circuits → AC Circuits: Fundamentals → Impedance and Reactance → AC Power and Resonance → Electromagnetic Waves → Postulates of Special Relativity → Time Dilation → Length Contraction → Lorentz Transformation → Relativistic Velocity Addition → Relativistic Momentum and Energy → Mass-Energy Equivalence and E=mc² → Photons as Particles with Energy and Momentum → Planck-Einstein Relation: Energy and Frequency → Photoelectric Effect → The Photon: Light as Quanta → Compton Scattering → Wave-Particle Duality → de Broglie Wavelength → The Schrödinger Equation → State Vectors and Wavefunctions → Quantum Superposition → The Measurement Problem → Interpretations of Quantum Mechanics → Postulates of Quantum Mechanics → Observables and Quantum Operators → Commutators and Commutation Relations → Quantum Angular Momentum → Quantum Mechanical Treatment of Hydrogen → Solving the Schrödinger Equation for Hydrogen Atom → Quantum Numbers → Electron Configuration → Periodic Trends → Covalent Bonding → Electronegativity and Bond Polarity → Ionic Bonding → Lewis Structures → VSEPR Theory and Molecular Geometry → Molecular Geometry and Electron Pair Geometry → Molecular Polarity and Dipole Moments → Intermolecular Forces → States of Matter and Phase Changes: Melting, Boiling, and Sublimation → Gas Laws and the Ideal Gas Equation → Gas Stoichiometry and Volume-Volume Calculations → Thermochemistry and Enthalpy → Heat Capacity and Calorimetry → Entropy and Molecular Disorder → Spontaneity and ΔG → Entropy and Gibbs Free Energy → Chemical Equilibrium → Acid-Base Chemistry → Weak Acid Ionization → Weak Base Ionization → Acid and Base Strength: Ka, Kb, and Ionization → Leaving Groups and Nucleofugality → SN2 Substitution Reactions → SN1 Substitution Reactions → E1 Elimination Reactions → Alcohols and Ethers: Structure, Properties, and Nomenclature → Reactions of Alcohols → Aldehydes and Ketones: Structure and Reactivity → Oxidation Reactions in Organic Chemistry → Oxidation of Alcohols to Aldehydes and Ketones → Aldehyde and Ketone Structure and Nomenclature → Nucleophilic Addition to Aldehydes and Ketones → Carboxylic Acids and Their Derivatives → IUPAC Nomenclature of Carbonyls and Carboxylic Acids → IUPAC Nomenclature of Alkenes → Electrophilic Addition to Alkenes → Aromaticity and Benzene → Electrophilic Aromatic Substitution (EAS) → Nucleophilic Aromatic Substitution (SNAr) → Nucleophilic Acyl Substitution → Amines: Structure, Basicity, and Reactions → Amine Reactivity: Nucleophilicity and Basicity → Amino Acid Structure and Properties → Peptide Bonds and Polypeptide Formation → Protein Primary Structure → Protein Secondary Structure → Protein Tertiary Structure → Enzyme Structure and Function → Transcription: DNA to RNA → RNA Types and Structure → RNA Structure and Intramolecular Base Pairing → RNA Processing and Splicing → Translation: RNA to Protein → Ribosomes: Protein Synthesis Machines → Translation: Initiation and Elongation → Post-Translational Modifications → Proteasomal Degradation and Ubiquitin-Mediated Marking → Cell Cycle Regulation and Checkpoints → Cell Cycle Checkpoints: Ensuring Genome Integrity → Cell Cycle Checkpoints and Cancer Prevention → Mitotic Spindle Checkpoint and Chromosome Segregation → Kinetochore Structure and Function → Mitochondria: Structure and Function → Cellular Respiration Overview → Glycolysis → Pyruvate Oxidation → The Krebs Cycle (Citric Acid Cycle) → Electron Transport Chain → ATP Synthesis and Oxidative Phosphorylation → ATP Hydrolysis and Cellular Free Energy → The Na+/K+-ATPase: Maintaining Ion Gradients → Resting Membrane Potential → Ligand-Gated Ion Channels → Voltage-Gated Sodium Channels → Action Potential Initiation: Threshold, All-or-None, and Depolarization → Primary Motor Cortex: Voluntary Movement and Motor Control → Cortical Organization and Columns → Cerebral Cortex Organization → Sensory Pathways Overview → Visual Processing Pathway → The Dorsal Stream and Action Control → Dorsal Stream and Visuomotor Control → Spatial Attention and Posterior Parietal Cortex → Prefrontal-Parietal Attention Networks and Control → Executive Control Networks and the Prefrontal Cortex → Neuroeconomics and Value Computation → Neural Mechanisms of Decision-Making → Working Memory Neural Circuits → Dorsolateral Prefrontal Cortex and Cognitive Control → Motor Planning: Premotor and Supplementary Motor Cortex

Longest path: 246 steps · 1353 total prerequisite topics

Prerequisites (3)

Primary Motor Cortex and Motor Representationhard Primary Motor Cortex: Movement Planning and Executionhard Dorsolateral Prefrontal Cortex and Cognitive Controlsoft

Leads To (1)

Basal Ganglia: Action Selection and Habit Formationsoft