8.1

• Sensory feedback plays an important role in directing the continuation of the responses that produced it.
• The only responses that are not normally influenced by sensory feedback are ballistic movements —brief, all-or-none, high-speed movements, such as swatting a fly.
• The posterior parietal association cortex (the portion of parietal neocortex posterior to the primary somatosensory cortex) plays an important role in integrating these two kinds of information, in directing behavior by providing spatial information, and in directing attention.
• A small area of prefrontal cortex that controls both eye movements and shifts in attention.

  frontal eye field
• Apraxia is a disorder of voluntary movement that is not attributable to a simple motor deficit (e.g., not to paralysis or weakness) or to any deficit in comprehension or motivation.
• Contralateral neglect, the other striking consequence of posterior parietal cortex damage, is a disturbance of a patient’s ability to respond to stimuli on the side of the body opposite to the side of a brain lesion in the absence of simple sensory or motor deficits.
• It receives projections from the posterior parietal cortex, and it sends projections to areas of secondary motor cortex, to primary motor cortex, and to the frontal eye field.

  Dorsolateral prefrontal association cortex
• Areas of secondary motor cortex are those that receive much of their input from association cortex (i.e., posterior parietal cortex and dorsolateral prefrontal cortex) and send much of their output to primary motor cortex.
• The supplementary motor area wraps over the top of the frontal lobe and extends down its medial surface into the longitudinal fissure.
• The premotor cortex runs in a strip from the supplementary motor area to the lateral fissure.
• Mirror neurons are neurons that fire when an individual performs a particular goal-directed movement or when they observe the same goal-directed movement performed by another.
• The primary motor cortex is located in the precentral gyrus of the frontal lobe. It is the major point of convergence of cortical sensorimotor signals, and it is the major, but not the only, point of departure of sensorimotor signals from the cerebral cortex.
• The somatotopic layout of the human primary motor cortex is commonly referred to as the motor homunculus.
• The process of identifying objects by touch.

  Stereognosis
• deficits in stereognosis

  astereognosia
• The cerebellum and the basal ganglia are both important and highly interconnected sensorimotor structures.
• The cerebellum receives information from primary and secondary motor cortex, information about descending motor signals from brain-stem motor nuclei, and feedback from motor responses via the somatosensory and vestibular systems.
• The basal ganglia are a complex heterogeneous collection of interconnected nuclei. It perform a modulatory function. It contribute few fibers to descending motor pathways; instead, they form neural loops via their numerous reciprocal connections with cortical areas and the cerebellum.
• The control of the speed and amplitude of movement based on motivational factors. For example, the basal ganglia might enable a concert pianist to play a particular piece with more or less vigor.

  Movement Vigor
• The ventromedial tracts are much more diffuse. Many of their axons innervate interneurons on both sides of the spinal gray matter and in several different segments


  The axons of the dorsolateral tracts terminate in the contralateral half of one spinal cord segment, sometimes directly on a motor neuron.