Chapter 11 Flashcards
Somatosensory and motor systems → direction of info
Afferent somatosensory information travels from the sensory organs inward via the somatic nervous system
Movement information travels out of the central nervous system via a parallel efferent motor system
Sensory → Afferent
Motor → Efferent
Connections between the nerves and spine
Fibers entering the posterior root bring sensory info from sensory receptors
Fibers leaving the anterior root carry motor info to the muscles
Collateral branches of sensory neurons may cross to the other side and influence motor neurons there
White-matter finer tracts carry info to and from the brain
Posterior → Sensory
Anterior → Motor
Dermatome
The spinal cord lies within a series of small bones called vertebrae
Each spinal segment corresponds to a region of body surface called a dermatome
Dermatomes C1-C8 → cervical nerves
Dermatomes T1-T12 → thoracic nerves
Dermatomes L1-L5 → lumbar nerves
Dermatomes S1-S5 → sacral nerves
Layering in the neocortex
The 6 cortical layers differ in appearance, characteristics, and functions
Sensory regions have a large input layer, and motor regions have a large output layer
Top → Bottom layering order: integrative functions → Sensory input (Afferent) → output to other parts of brain (efferent)
Motor cortex: frontal lobe, anterior to central fissure
Sensory cortex: posterior to central fissure, extends into parietal lobe
Parallel and independent movement control
Movement required for simple actions involves widespread CNS regions → ex: picking up a cup
Forebrain areas must act through lower functional areas: the brainstem and spinal cord
There must be some parallel organization within these areas
↳ you can do other behaviors (ex. Speaking) while picking up a cup
There also must be some independence in the function of these brain regions → movement independent of conscious control
Sequentially organized movement
- Visual info required to locate the target
- Frontal-lobe motor areas plan the reach and command the movement
- Spinal cord carries information to the hand
- Motor neurons carry message to muscles of the hand and forearm
- Sensory receptors on the fingers send message to sensory cortex saying object has been grasped
- Spinal cord carnies sensory info to brain
- Basal ganglia judge grasp forces, and cerebellum corrects movement errors
- Sensory cortex receives message that the cup has been grasped
Forebrain: initiating movement
Lashley (1951) → argued that movements must be performed as motor sequences, with the next sequence held in readiness while the ongoing one is underway (priming)
Motor sequence: movement modules are preprogrammed by the brain and produced as a unit
Ideal motor sequence: movement categories produced from brain as entire preprogrammed sequence
Initiating a motor sequence
Frontal lobe regions act hierarchically and in parallel to initiate behavior
Prefrontal cortex: plans complex behavior
Premotor cortex: produces the appropriate complex movement sequences
Primary motor cortex: specifies how each movement is to be carried out
Prefrontal cortex → initiating motor sequence
Top of hierarchy → plans behavior
Makes decisions about behavioral goals to select
PFC damage leads to the inability to suppress inappropriate behaviors
Promoter control
Premotor cortex receives instructions from the PFC
Produces movements by coordinating body parts
If damaged → no longer able to produce fine motor functions
Primary motor cortex → M1
Specializes in producing focal skilled movements, such as those of the arms, hands, and mouth
People with damage to M1 have difficulty reaching and shaping their fingers to perform various hand grasps
Simple movement → blood flow in brain
Blood flow increases in hand area of primary somatosensory and primary motor cortex when participants use a finger to push a lever
Movement sequence → blood flow in brain
Blood flow increases in promotor cortex when participants perform a sequence of movements
Complex movement → blood flow in brain
When participants use a finger to find a route through a maze, blood flow also increases in prefrontal, temporal, and parietal cortex
Brainstem: species-typical movement
Species typical movement→ bipedal walking in humans etc.
Brainstem: organizes many adaptive movements → standing upright, coordinating limb movement, walking and swimming, etc.
Cerebral palsy
Hard time executing voluntary movement
Disorder primarily of motor function, in which making voluntary movements becomes difficult
Caused by brainstem trauma
Often due to birth complications → lack of oxygen to brain etc.
Locked-in syndrome
Condition in which a patient is aware and awake but cannot move or communicate verbally because of complete paralysis of nearly all voluntary muscles except the eyes
Due to brainstem damage
Extent of paralysis due to spinal cord injury
Cervical (neck) → quadriplegia
Thoratic (upper back) → paraplegia
Lumbar (lower back) → paraplegia → less extreme or less of lower body
Quadriplegia and paraplegia → reflexes
Spinal reflexes still function even though the spinal cord is cut off from communication with the brain
Paralyzed limbs may display spontaneous movements or spasms
The brain can no longer guide the timing of these automatic movements
Fritsch and Hitzig
Discovered they could electrically stimulate the neocortex of an anesthetized dog to produce movements of the mouth, limbs, and paws on the opposite side of the dogs body
1st example of controlateral motor control
Wilder Penfield
Used electrical stimulation to map the cornices of human patients who were about to undergo neurosurgery
Confirmed the role of the primary motor cortex in producing movement in humans
