Neurophysiology: Motor Cortex and Pyramidal Tracts

A set of flashcards covering neurophysiological terms, anatomical views, brain structures, and neural measurement techniques related to motor control and learning.

Absolute error (AE)

Represents the absolute difference between the target and the performance without considering bias ($+/-$).

Constant error (CE)

Represents the directional performance bias ($+/-$).

Variable error (VE)

Represents the consistency or inconsistency of the performance, specifically the standard deviation.

Anterior

Towards the front.

Posterior

Towards the back.

Superior

Above.

Inferior

Below.

Medial

Towards the midline.

Lateral

Towards the edge.

Rostral

Towards the nose.

Caudal

Tail (posterior).

Ventral

Towards the front (inferior brain).

Dorsal

Towards the back (superior brain).

Frontal/coronal plane

An anatomical plane used to identify and distinguish neural structures of the CNS by dividing the body into front and back sections.

Sagittal plane

An anatomical plane that divides the body or brain into left and right parts.

Horizontal plane

An anatomical plane used to identify neural structures by dividing them into top and bottom sections.

Central nervous system (CNS)

Consists of the brain and spinal cord; it acts as the powerhouse responsible for generating motor commands and integrating sensory information.

Peripheral nervous system (PNS)

Connecting nerves (neurons) outside the CNS that relay afferent signals from the periphery and efferent signals to the muscles.

Upper motoneurons

Neurons arising from premotor areas that connect the brain to the spinal cord via axons, facilitating the planning of voluntary movement.

Lower motoneurons (alpha motoneurons)

Neurons arising from the brainstem and spinal cord that directly innervate skeletal muscle and can control complex patterns like reflexes.

Grey matter

CNS tissue containing the dendrites and cell bodies of neurons.

White matter

CNS tissue containing the axons of neurons.

Frontal lobe

The brain region containing motor areas required for voluntary movement, planning, language, and problem solving.

Parietal lobe

The brain region responsible for the integration of sensory information including touch, temperature, and pain.

Occipital lobe

The brain region that processes visual information to determine location and depth.

Temporal lobe

The brain region involved in memory formation and auditory processing, containing the hippocampus.

Gyri

Raised areas or ridges formed by fibres in each lobe of the brain.

Sulci

Troughs or fissures that separate the gyri in the brain.

Central sulcus

The trough that separates the frontal lobe from the parietal lobe.

Sylvian fissure (lateral sulcus)

The structure that defines the border of the temporal lobe.

Parieto-occipital sulcus

The structure that separates brain regions associated with visual processing and sensory processing.

Primary motor cortex (M1)

The motor area responsible for movement execution and distinct movements of contralateral limbs.

Premotor cortex (PMC)

The area responsible for motor planning and the selection of movements.

Supplementary motor area (SMA)

Motor area associated with movements from both ipsilateral and contralateral muscles or stopping ongoing voluntary movement.

Betz cells

“Giant pyramids” found in Layer V of the primary motor cortex that directly innervate alpha motoneurons and the brainstem.

Lateral PMC

The part of the premotor cortex that encodes the selection of movement based on external stimuli like visual cues.

Medial PMC (Supplementary Motor Area)

The part of the premotor cortex that encodes the selection of movement based on internal stimuli such as memory.

Electroencephalography (EEG)

A method using electrodes to measure the electrical activity of different cortical areas.

Positron emission tomography (PET)

An imaging technique using a radioactive tracer to assess metabolic activity and blood flow in the brain.

Functional magnetic resonance imaging (fMRI)

A high-resolution imaging technique used to assess blood flow in the brain, often used for activation maps.

Electromyography (EMG)

A technique that measures the electrical activity of nerves and muscles to infer muscle weakness or motor unit activation.

Motor Evoked Potential (MEP)

A potential generated by synchronous firings of corticospinal neurons following TMS, reflecting the excitability of the entire corticospinal pathway.

Motor wave (M-wave)

An evoked potential produced by stimulation to peripheral nerve fibres that reflects the excitability of the nerve.

Transcranial Magnetic Stimulation (TMS)

A non-invasive magnetic stimulation delivered over the scalp to activate neurons of the motor cortex.

Corticobulbar tract

Part of the pyramidal tracts that projects from motor areas to the brainstem to innervate head and neck musculature.

Lateral corticospinal tract

Pathway formed by ~$90\%$ of fibres that cross at the medulla to control extremity muscles on the contralateral side.

Anterior corticospinal tract

Pathway formed by ~$10\%$ of neurons that do not decussate at the medulla, responsible for axial and trunk muscles.

Glutamate

An excitatory neurotransmitter that promotes the propagation of action potentials along a pathway by generating EPSPs.

Gamma-amino butyric acid (GABA)

An inhibitory neurotransmitter that prevents the generation and propagation of action potentials by generating IPSPs.

Excitatory post-synaptic potentials (EPSP)

Graded potentials generated by glutamate that depolarize the neuron, making the membrane more positive.

Inhibitory post-synaptic potentials (IPSP)

Graded potentials generated by GABA that hyperpolarize the neuron, making the cell membrane more negative.