Neuroscience Motor function

Motor Function

Primary Areas of Motor Control

• Cerebral Cortex

• Basal Ganglia

• Cerebellum

Cerebrum

Primary motor cortex (M1)

• Located in precentral gyrus

• Origin of cortico-spinal tract

• Works with other motor area to plan and implement movement

• Lesions to primary motor cortex lead to loss of voluntary movement on contralateral side of body

Premotor and supplementary motor areas

• Premotor: located anterior to M1 

  • plays role in Praxis (ability to plan motor movements)

• Supplementary motor area: part of premotor area 

  • plays role in bilateral control of posture and praxis

Frontal Eye Fields

• Responsible for visual attention and directing visual saccades to stimulus of interest

Motor Planning

• Ideational praxis: the ability to cognitively understand the motor demands of a task

• Ideomotor planning: the ability to access and execute the motor plan

Basal Ganglia

• Stereotypical

  • Hard wired patterns

  • Develop as a normal part of nervous system maturation

  • Walking, arm stretch during yawns, arm swing during walking

      -    Automated

- Movement patterns that are mediated by conscious control while learning, but become         automated once learned

- Riding a bike, driving, writing

• May have a role in cognitive processes related to rewarding and addictive behaviors

• May play a role in ADHD as it relates to impulse control and turn-taking

• Neurotransmitters (Dopamine, GABA, Acetylcholine)

Basal Ganglia Pathways: 

- Primary motor cortex (M1) → Basal Ganglia → Thalamus → back to M1 and premotor areas

Lesions of Basal Ganglia

• Symptoms = Difficulty initiating, continuing, or stopping movements

• Examples = parkinson's disease, huntington’s disease, cervical dystonia, myoclonus-dystonia, tourette’s syndrome

Cerebellum

• Coordination of movement

• Regulation of muscle tone

• Maintenance of posture and equilibrium

• Proprioception

Cerebellar lobes

• Archicerebellum (Flocculonodular)

  • Central area, receives information from vestibular nuclei

  • Damage to this lobe results in impairments of balance and gait

• Paleocerebellum (Anterior)

  • Information from anterior and posterior spinocerebellar tracts

  • Damage = difficulty with precision movements of body and limbs

• Neocerebellum (Posterior)

  • Receives information from cerebral hemispheres

  • Damage = impairments with planning anticipatory movements and cognitive function of movement

Cerebellar Lesions

• Ataxia (loss of coordination and balance, difficulty with walking)

• Dysmetria (inability to judge distance, speed and power of movements)

• Inability to regulate reciprocal movements

Sensory Function and Dysfunction

Sensory Pathway: Sensory Information → Thalamus → Postcentral gyrus (SS1)

• Damage to the primary sensory cortex will result in contralateral sensory loss

Secondary Somatosensory Cortex (SS2)

• Found posterior to the primary somatosensory cortex and is neurally tied to it

• This is where meaning is attached to incoming sensory information

• Synthesizes multiple sensory inputs to create a complete comprehension of the object being felt

Lesions

• Perceptual Dysfunction

  • Tactile: tactile agnosias (inability to recognize objects by touch)

  • Visual: visual agnosias (inability to recognize object by sight)

  • Auditory: auditory agnosias (inability to recognize sounds)