Motor Systems Vocabulary

These flashcards cover key vocabulary and concepts from the Motor Systems lecture notes.

Charles Sherrington

Confirmed that stimulating adjacent regions of the precentral gyrus in apes elicited movements of adjacent contralateral body parts.

Wilder Penfield

Verified the presence of a topographical map of body musculature in the primary motor cortex in humans by systematically stimulating different brain regions in human patients.

Motor Maps

Define a distorted representation of the body, with disproportionately large area of the lateral primary motor cortex devoted to the lips, tongue and hands, and a much smaller area of the dorsal and medial primary motor cortex devoted to the lower extremities and genitalia.

Proximal Muscles

Are located medially in the cervical spinal cord (close to the midline).

Distal Muscles

Are located laterally in the cervical spinal cord (toward the digits).

Motor Command

Whether the activity of neurons in these motor maps specifies what to do.

Motor Maps

Represent movements and not muscles.

Edward Evarts

Pioneered the technique of implanting electrodes in the motor cortex of monkeys that had been trained to reach toward cued targets in order to receive rewards.

Frontal Eye Fields

Generate commands to move the eyes.

Superior Colliculus

In the midbrain, projects to the brainstem reticular formation, which organizes and coordinates activation of the extraocular muscles by lower motor neurons in the brainstem.

Saccades

Electrical stimulation at any site evokes a saccade with a particular direction and amplitude, whereas stimulation at nearby sites evokes saccades with slightly different vectors.

Motor Preparation

A dynamic, competitive process linking sensory information to the intention to move, and that such processing entails the graded activation of neurons in a variety of higher-order premotor cortical and subcortical areas.

Readiness Potential

EEG recordings from medial frontal electrodes show a pronounced negative wave that begins up to several seconds in advance of the actual movement.

Anosognosia

Meaning loss of awareness. When premotor areas are damaged along with the primary motor cortex, patients are unaware of (or even deny) their inability to move.

Benjamin Libet

Found that estimates of the intention to move preceded the movement itself by about 200 milliseconds. However, readiness potentials over premotor areas clearly preceded subjects’ awareness of when they intended to move.

William Newsome and Michael Shadlen

Provided evidence that neuronal responses in a number of premotor areas involved in saccadic eye movements are systematically related to the weight of sensory evidence favoring a particular movement.

Paul Glimcher and Michael Platt

Designed a series of studies to understand how internal motivations shape the responses of neurons in the posterior parietal cortex.

Supplementary Motor Area (SMA)

Crucial for generating movements in the absence of explicit sensory cues, and the premotor cortex is especially important for the production of cued movements.

Jun Tanji and colleagues

Found that many neurons in the SMA were selectively activated when a particular action embedded within a sequence was performed.

Optic Ataxia

Damage to the parietal cortex in humans can disrupt both reaching and saccades

Mel Goodale and David Milner

Suggested that the dorsal visual stream may be particularly important for using vision to guide movement, whereas the ventral visual stream may be specialized for object identification

Basal Ganglia

Appears to serve as a gating mechanism, inhibiting potential movements until they are fully appropriate for the circumstances in which they are to be executed.

Parkinson’s Disease

The selective death of neurons in the substantia nigra pars compacta that use the neurotransmitter dopamine increases the excitatory tone of the direct pathway through the basal ganglia. Patients show a marked disruption in the ability to initiate voluntary movement.

Huntington’s Disease

Involves hereditary atrophy of the caudate nucleus. Patients typically have signs and symptoms that are the opposite of those seen in Parkinson’s disease.

Cerebellum

Responsible for online error corrections necessary to produce smoothly coordinated, skilled movements.

Truncal Ataxia

Lesions of the medial cerebellar vermis result in a condition known as . Characterized by a wide-based, unsteady gait.

Appendicular Ataxia

Damage to the lateral cerebellum disrupts the sensory coordination of limb movements.

Intention Tremor

Patients with damage to the ipsilateral cerebellum show halting, uncoordinated movements of the hand and arm; this deficit is called.