NSCI 110 1st Edition Lecture 26 Outline of Last Lecture I Music and language related tasks can be detected through PET scans a Activate different regions surrounding Heschi s gyrus II There are various components that constitute expression of language a Phoneme morpheme b Semantics syntax lexicon c Context discourse III Different varieties of aphasia lead to deficits in speech and comprehension of language IV Information involving the somatosensory cortex involves a specific serial order a The amount you attend to a motor task depends on familiarity and complexity Outline of Current Lecture I Control of motor activity exists in a hierarchy a Prefrontal cortex premotor cortex motor cortex II Mirror neurons can be activated not just by carrying out a task but by observing it and thinking about it as well III Spatial representation of motor control is represented on a homunculus IV The motor cortex involves several fundamental movement categories that may differ depending on the type of response required a Brainstem controls species specific behaviors b Motor cortex involves complex series of movements c Spinal cord controls more instinctual movements such as walking or scratching V VI VII The cortex compensates action potential rates depending on anticipation of a task The cortex exhibits plasticity a Rehabilitation can help lesioned areas regain motor control The corticospinal tract is the main efferent pathway leaving the motor cortex a Lateral tracts relay information to the contralateral sides b Ventral tracts relay information to ipsilateral sides Current Lecture Hierarchy of movement control o Prefrontal cortex plans premotor cortex sequences motor cortex executes actions Monkey on slide why is this behavior disrupted o Can the joints assume the correct position o Does the subject understand the use of the object o Could movement sequence be enacted together These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute Mirror neurons are neurons in the premotor cortex and other areas that can be active during action or observation of a specific task o Active upon thinking about doing the task not just doing it o Less active if using a tool o The brain s response to seeing different actions is influenced by the acquired motor skills of the individual observer MOTOR SYSTEM ORGANIZATION Wilder Penfield mapped the cortices of patients who were about to undergo neurosurgery o Confirmed motor cortex role in movement by asking different tasks of the patients o Stimulating electrode movement of certain body parts Homunculus is a topographical representation of the body o Spatial representation as perceived The motor cortex does not represent muscle but rather a repertoire of fundamental movement categories o Monkey models revealed that longer stimulations give rise to more complex series of movements Defensive facial posture Hand to mouth Central body space Outward reach Climb reach o Not the only site to elicit movement categories Brainstem gives rise to species specific behaviors swimming grooming nest making chewing defensive behaviors Spinal cord facilitates complex motor patterns that are common among a species scratching walking Activation in neurons occurs before motor activity takes place o Anticipatory response before movement occurs Planning and executive movement discharged before during frontal cortex o The cortex is capable of code force of movement Rate duration of firing compensates depending on weights of objects complexity of task o Simple coding of movement direction Flexors extensors Is the motor cortex organization stable over time o No it changes It is directly influenced on the daily tasks you participate in and lifestyle Neuroplasticity of the motor system o What occurs when a lesion is induced Monkey experiment lesioned a region responsible for digit wrist forearm movement Differences between no rehab and rehab What happened to the cortical representation of the two subject groups The monkeys without rehab has less neurons devoted to the activity but those with rehab regenerated the area to a larger extent Corticospinal tract is the main efferent pathway that begins in the motor cortex o Corresponds to layer V of the cortex Axons descend into the brainstem some go to the brainstem nuclei and emerge on the brainstem s ventral surface as pyramidal tracts bumps on each side are seen in the lumps on the tegmentum o Responsible for conscious control over skeletal muscles Internal capsule is the tract of white matter between the cortex and medulla From the medulla the tract can divide into the ventral stays ipsilateral smaller or lateral thicker CS tract know each of their functions Decussation of Pyramids looks like an X where the lateral tracts cross over the ventral tracts do not do this All the tracts except those responsible for the face neck descend down the CS o Corticobulbar tract gives us conscious control over eye jaw face muscles Descends to internal capsule but branches off near the brainstem Different output regions midbrain pons medulla depending on what movement is to be produced Lateral CS tract branches at the medulla to cross to the contralateral side o Moves digits and limbs Ventral CS tract stays on the ipsilateral side o Moves muscles of the midline trunk Organization in the spinal cord ventral horn o Lateral tract synapses with interneurons and motor neurons Interneurons synapse with motor neurons that innervate muscle More distal areas of the body correspond with more distal neurons in the spinal cord o The interneurons and motor neurons of the spinal cord are envisioned as a homunculus representing the types of muscles they innervate o Limb muscles are paired Extensors move limbs away from the trunk Flexors move limbs toward the trunk o Connections between interneurons and motor neurons ensure coordination of extensor flexor actions o Left upper motor neurons control Trunk muscles along the midline Limbs on the body s right side