Lecture 27 Outline of Last Lecture I. Control of motor activity exists in a hierarchya. Prefrontal cortex  premotor cortex  motor cortexII. Mirror neurons can be activated not just by carrying out a task, but by observing it and thinking about it as wellIII. Spatial representation of motor control is represented on a homunculusIV. The motor cortex involves several fundamental movement categories that may differ depending on the type of response requireda. Brainstem controls species-specific behaviorsb. Motor cortex involves complex series of movementsc. Spinal cord controls more instinctual movements such as walking or scratchingV. The cortex compensates action potential rates depending on anticipation of a taskVI. The cortex exhibits plasticitya. Rehabilitation can help lesioned areas regain motor controlVII. The corticospinal tract is the main efferent pathway leaving the motor cortexa. Lateral tracts relay information to the contralateral sidesb. Ventral tracts relay information to ipsilateral sidesOutline of Current Lecture I. The corticospinal tract is divided into ventral and lateral pathwaysII. Extrapyramidal tracts originate in areas excluding the primary motor cortexa. Rubrospinal tract controls arm musclesb. Tectospinal tract controls head and neck musclesIII. Reflexes controlled by the spinal cord involve the movement of agonist and antagonist musclesIV. The basal ganglia are involved in regulating motor activity through connections to the cortex and thalamusa. Volume hypothesis stresses the importance of the globus pallidus and putamen in modulating the activity of this pathwayCurrent Lecture- Left upper motor neurons control:o Trunk muscles along midline  Ventral CS tracto Limbs on the body’s right side Lateral CS tracto The pyramidal tract refers to the internal capsule  the CS and cortibulbar tracts- Extrapyramidal tracts originate in locations other than the primary motor cortexThese 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. NSCI 110 1st Editiono Rubrospinal tract originates in the red nucleus of the tegmentum Receives input from the motor cortex and cerebellum in order to guide muscles (primarily arm muscles) Red nucleus restores some motor function lost from CS system damage (pyramidal tract lesions)o Tectospinal tract originates in the superior colliculus of the tectum Receives input from the visual system to coordinate head and neck movements  Orienting to visual stimuli- Limb muscles are pairedo Extensors vs. flexorso Coordinated movement requires extensor contraction as flexor relaxes, or vice versa Producing a lot of force or becoming rigid requires contraction of both- Reflexes occur at the level of the spinal cordo Between the patella and tibia is a tendon that connects to the quadricep muscles This muscle detects the stretch of the tendon and the sensory neurons are activated Send signals to the dorsal root ganglia and synapses on lower motor neuron The lower motor neuron travels through the ventral root out of the spinalcord and sends signals to the same muscle (the agonist muscle)o The afferent sensory neurons can also synapse on inhibitory interneurons Help regulate activity  connect to the antagonist muscles which control the opposite movement of the original muscle (flexor or extensor)o Therefore, movement is a result of different firing rates to agonist and antagonistmuscles- Basal ganglia and movement forceo Basal ganglia receives input from: All areas of neocortex, limbic cortex, some from motor cortex Nigrostriatal dopaminergic system from substantia nigrao Projects back to the motor cortex via the thalamus and substantia nigrao Also involved in habit learning, motivation, emotiono Damage to the basal ganglia results in: Hyperkinetic symptoms  twitching, writhing (called dyskinesias)- Huntington’s Hypokinetic symptoms  rigidity, difficulty initiating and producing movements- Parkinson’so Volume hypothesis involves the internal globus pallidus inhibitory role GP “turned up”  movement blocked (indirect pathway)- Tourettes involves problems with this pathway GP “turned off”  movement is allowed (direct pathway)- Motor cortex releases glutamate (excitatory) to putamen which synapses on the globus pallidus internal (inhibitory)- More GABA release synapses with the thalamus (inhibitory)- So, less GABA release to the thalamus (less inhibition)- More excitatory activity from the thalamus to cortex The GP has inhibitory effects on the thalamus, which has direct connections to the