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Question 1

Alpha motor neurons

Answer 1

The neurons that terminate on muscle fibers, causing contractions that produce movements. Alpha motor neurons originate in the spinal cord and exit through the ventral root of the cord.

Question 2

Basal Ganglia

Answer 2

A collection of five subcortical nuclei: the caudate, putamen, globus pallidus, subthalamic nucleus, and substantia nigra. The basal ganglia are involved in motor control and learning. Reciprocal neuronal loops project from cortical areas to the basal ganglia and back to the cortex. Two prominent basal ganglia disorders are Parkinson’s disease and Huntington’s disease.

Question 3

Central pattern generator

Answer 3

A neural network limited to the spinal cord that produces patterned motor outputs without descending commands from the cerebral cortex or sensory feedback.

Question 4

Cerebellum

Answer 4

Literally, “small cerebrum” or “little brain.” A large, highly convoluted (infolded) structure located dorsal to the brainstem at the level of the pons. The cerebellum maintains (directly or indirectly) interconnectivity with widespread cortical, subcortical, brainstem, and spinal cord structures, and plays a role in various aspects of coordination ranging from locomotion to skilled, volitional movement.

Question 5

Corticomotoneurons (CM neurons)

Answer 5

Specialized corticospinal neurons with axons that terminate directly on spinal motor neurons. Most are located in the primary motor cortex.

Question 6

pyramidal tract

Answer 6

A bundle of axons that originate in the cortex and terminate monosynaptically on alpha motor neurons and spinal interneurons in the spinal cord. Many of these fibers originate in the primary motor cortex, although some come from secondary motor areas. The corticospinal tract is important for the control of voluntary movements.

Question 7

Deep brain stimulation (DBS)

Answer 7

The electrical stimulation of brain structures via an implanted electrode. Stimulation of the subthalamic nucleus, one of the nuclei of the basal ganglia, is used as a treatment for Parkinson’s disease.

Question 8

Effector

Answer 8

Any part of the body that can move, such as an arm, finger, or leg.

Question 9

Extrapyramidal tracts

Answer 9

A collection of motor tracts that originate in various subcortical structures, including the vestibular nucleus and the red nucleus. These tracts are especially important for maintaining posture and balance.

Question 10

Huntington’s disease

Answer 10

A genetic degenerative disorder in which the primary pathology, at least in the early stages of the disease, is observed in the striatum (caudate and putamen) of the basal ganglia. Prominent symptoms include clumsiness and involuntary movements of the head and trunk. Cognitive impairments are also seen and become pronounced over time.

Question 11

Hyperdirect pathway

Answer 11

Direct connections from the motor cortex to the subthalamic nucleus (STN) that bypass the striatum and convey excitatory input directly to the STN and palladium.

Question 12

Mirror neuron

Answer 12

A neutron that shows similar responses when an animal is either performing an action or observing that action produced by another organism. For instance, a mirror neuron responds when you pick up a pencil and when you watch someone else pick up a pencil. Mirror neurons are hypothesised to provide a strong link between perception and action, perhaps providing an important basis for the development of conceptual knowledge.

Question 13

Mirror neuron network

Answer 13

A distributed network of neurons that respond not only to one’s own actions but also to perceived actions.

Question 14

Parkinson’s disease

Answer 14

A degenerative disorder of the basal ganglia in which the pathology results from the loss of dopaminergic cells in the substantia nigra. Primary symptoms include difficulty in initiating movement, slowness of movement, poorly articulated speech, and, in some cases, resting tremor.

Question 15

Population vector

Answer 15

The sum of the preferred directions of individual neurons within a group that represents the activity across that group. Population vectors reflect the aggregate activity across the cells, providing a better correlation with behaviour than that obtained from the analysis of individual neurons. For example, the population vector calculated from neurons in the motor cortex can predict the direction of a limb movement.

Question 16

Preferred direction

Answer 16

A property of cells in the motor pathway, referring to the direction of movement that results in the highest firing rate of the neuron. Voxels have also been shown to have preferred directions in fMRI studies, indicating that such preferences can even be measured at the cell population level of analysis.

Question 17

Premotor cortex

Answer 17

A secondary motor area that includes the lateral aspect of Brodmann area 6, just anterior to the primary motor cortex. Although some neurons in the premotor cortex project to the corticospinal tract, many terminate on neurons in the primary motor cortex and help shape the forthcoming movement.

Question 18

Primary motor cortex

Answer 18

A region of the cerebral cortex that lies along the anterior bank of the central sulcus and precentral gyrus, forming Brodmann area 4. Some axons originating in the primary motor cortex from the majority of the corticospinal tract; others project to cortical and subcortical regions involved in motor control. The primary motor cortex contains a prominent somatotopic representation of the body.

Question 19

Spinal interneurons

Answer 19

Neurons found in the spinal cord. Many descending axons from the pyramidal and extrapyramidal tracts synapse on interneurons, which, in turn, synapse on other interneurons or alpha motor neurons.

Question 20

Substantia nigra

Answer 20

One of the nuclei that form the basal ganglia. The substantia nigra is composed of two parts: The axons of the substantia nigra pars compacta provide the primary source of the neurotransmitter dopamine and terminate in the striatum (caudate and putamen). The substantia nigra pars reticular is one of the output nuclei from the basal ganglia.

Question 21

Supplementary motor area (SMA)

Answer 21

A secondary motor area that includes the medial aspect of Brodmann area 6, just anterior to the primary motor cortex. The SMA plays an important role in the production of sequential movements, especially those that have been well learned.

Question 22

optic ataxia

Answer 22

can see but can’t grab

Question 23

motor hierarchy - bottom

Answer 23

• muscle innervation
  – alpha motor neurons, gamma motor neurons, sensory neurons
• spinal reflexes
  – alpha motor neurons, gamma motor neurons, sensory neurons, stretch reflex
• central pattern generator
  – spinal cord

Question 24

motor hierarchy - middle (8)

Answer 24

• brainstem structures
• 12 cranial nerves
• vestibular nuclei
• reticular formation nuclei
• substantia nigra
• extrapyramidal tracts (posture, muscle tone, movement speed)
• cerebellum (ataxia)
• basal ganglia (parkinson’s, huntington’s)

Question 25

motor hierarchy - top

Answer 25

• primary motor cortex (pyramidal tract) (hemiplegia)
• secondary motor area (premotor cortex, supplementary motor area)
• broca’s area, inferior and superior parietal lobule, frontal eye fields
• two dorsal streams
  – dorso-dorsal stream to dorsal PM - superior parietal lobule -> optic ataxia
  – ventro-dorsal stream to ventral PM - inferior parietal lobule - apraxia (inability to coherently use objects)

Question 26

affordance competition hypothesis

Answer 26

Your brain looks at what you can do (like playing with a toy or eating a snack). It thinks about all the choices at the same time and picks the best one, like choosing the yummiest snack. This happens in a part of your brain that helps you decide what to do and how to do it, all at once!