The Brain, Speech and Language: Control circuits Dr Pedro Amarante Andrade

CONTROL CIRCUITS Integrate and control the activities of the structures and pathways involved in motor performance Key point: Neither the basal ganglia not the cerebellum project directly onto lower motor neurons.

CONTROL CIRCUITS CEREBELLUM AND BASAL GANGLIA The cerebellum: coordinates motor and sensory information Gets info from the cortex about what muscles SHOULD be doing, and compares this with what is ACTUALLY happening The basal ganglia: involved in control of background movement, and initiation of movement patterns

THE CEREBELLUM ‘little brain’ in Latin

THE CEREBELLUM ‘little brain’ in Latin Vestibulocerebellum = flocculonodular lobe

PROJECTION TO THE CORTEX Cortex sends information to cerebellum via pontine nuclei cerebellum send information back to the cortex via the thalamus Cerebellum also receives sensory information from the brain stem and spinal cord (e.g. proprioceptive stimuli via spinocerebellar tracts) The basal ganglia form a complex collection of nuclei also involved in a loop from cortex to basal ganglia to thalamus and back to the cortex http://www.sofiatopia.org/equiaeon/ibrain12.jpg

FUNCTIONS OF THE CEREBELLUM Stores learned sequences of movements Participates in fine tuning and co-ordination of movements produced elsewhere in the brain Integrates all of these things to produce fluid and harmonious movements. So prime task is to ensure smooth coordination of muscles

ANTERIOR CEREBELLUM Spinocerebellum projection area for the spinocerebellar proprioceptive information Receives input from muscle and joint receptors (Golgi tendon organs & muscle spindles) via spinocerebellar tracts Regulates posture, gait and truncal tone.; It is connected to the spinal cord and controls postural muscle activity by influencing muscle tone.

POSTERIOR CEREBELLUM Cerebrocerebellum Connected to the contralateral cortex and thalamus Lateral portions of the cerebellar hemispheres have a role in coordinating skilled, sequential voluntary muscle activity Ensures that when one set of muscles initiates a movement, the opposing set acts as a brake, so that the body part in question arrives at its target precisely.

FLOCCULONODULAR LOBE Vestibulo Cerebellum The oldest part phylogenetically so aka the archicerebellum; Connects with the vestibule of the inner ear and is involved in balance. Contains the which connects with the 4 vestibular nuclei in the brainstem Modulates equilibrium (balance) and orientation of head and eyes fastigial nucleus vestibular nuclei

CEREBELLAR PEDUNCLES mostly afferent from spinal cord and brainstem; efferent to vestibular mechanisms and reticular formation Mainly efferent output via purkinje cells afferent from pontine nuclei Superior Middle Inferior Fibre tracts enter/leave through the inferior, middle and superior cerebellar peduncles

CEREBELLAR ANATOMY http://humanphysiology.academy/Neurosciences%202015/Chapter%205/A.5p%20Cerebellar%20Pathways.html

CEREBELLAR ANATOMY Motor planning Position sense Feedback

CEREBELLAR CONTROL CIRCUITS 1 loop important in planning and programming learned movements Primary motor & premotor regions Pontine nuclei Lateral cerebellar hemispheres Deep cerebellar nuclei Ventral thalamus

CEREBELLAR CONTROL CIRCUITS 2 Corticospinal/ Corticobulbar fibres Intermediate cerebellar hemispheres Deep cerebellar nuclei Ventral thalamic nuclei Primary motor cortex

CEREBELLAR CONTROL CIRCUITS & premotor regions Primary motor cortex Corticospinal/ Corticobulbar fibres Pontine nuclei Ventral thalamus Deep cerebellar nuclei Lateral cerebellar hemispheres Intermediate cerebellar hemispheres

FUNCTIONS OF CEREBELLAR CONTROL CIRCUITS Coordinate the timing between the single components of a movement Scale the size of muscular actions Coordinate the sequence of agonists and antagonist

CEREBELLAR SPEECH MOTOR CONTROL SUMMARY: Cortex sends preliminary advance information referring intended speech goals to cerebellum These preliminary speech commands are provisional, imprecise and in excess of those needed to accomplish speech goal Cerebellum is thus ‘primed’ to check the adequacy of the outcome, based on sensory information coming in from the periphery (i.e. muscle spindles, joint and tendon sensors) Cerebellum updates the motor output from the cortex to help smooth the actions of agonist/antagonist muscle contractions

BASAL GANGLIA CIRCUITS

BASAL GANGLIA CIRCUITS Important in generating components of motor programmes for speech Cortex initiates impulses in excess of requirements to produce the motor act Basal ganglia is modulate through inhibition these impulses Important in regulating muscle tone, goal directed activities, automatic activities

ANATOMY OF THE BASAL GANGLIA http://7e.biopsychology.com/vs11.html

ANATOMY OF THE BASAL GANGLIA http://antranik.org/cerebral-white-matter-and-gray-matter-and-basal-ganglia/ https://kin450-neurophysiology.wikispaces.com/Basal+Ganglia+II

ANATOMY OF THE BASAL GANGLIA

BASAL GANGLIA CONTROL CIRCUITS Selectively activates and inhibits movements. Provides internal cues for planning and refining slow continuous movement

BASAL GANGLIA CONTROL CIRCUITS Caudate nucleus and putamen (the striatum): act together as a functional unit - INPUT Globus pallidus interna and substantia nigra pars reticulata - main OUTPUT Globus pallidus externa, Sub thalamic nucleus, and substantia nigra pars compacta - intermediate

BASAL GANGLIA CONTROL CIRCUITS Two Loops Direct = responsible for activating movement overall excitatory Indirect = stopping unwanted movement overall inhibitory The two pathways operate together to provide balanced control of descending pathways. NB Do not confuse these loops with the direct/indirect activation pathway

TWO LOOPS

NEUROTRANSMITTERS GABA (gamma aminobutyric acid) inhibitory - Glutamate excitatory + Ach (acetylcholine) - synapse in the striatum – excitatory + Dopamine (substantia nigra) neuromodulatory The balance of these is crucial to normal functioning of the loops and therefore motor output

DIRECT/INDIRECT PATHWAY OF BASAL GANGLIA Direct = Making movement (excitatory) Indirect = not moving (inhibitory) http://neurolove.tumblr.com/post/2745681497/lets-breakdown-the-basal-ganglia-pathways-there

DIRECT/INDIRECT PATHWAY OF BASAL GANGLIA CORTEX Direct = Promoting movement (excitatory) Striatum Thalamus Aim = Reduce the natural inhibited state of the Thalamus :o( Globus Pallidus Subthalamus Thalamus always wants to excite the cortex! Glutamate (+) GABA (-) Substantia nigra Dopamina

DIRECT/INDIRECT PATHWAY OF BASAL GANGLIA CORTEX Indirect = not moving (inhibitory) Striatum Thalamus Aim = Avoid unwanted movement (Thalamus and Subthalamus) :O( Globus Pallidus Subthalamus Thalamus always wants to excite the cortex! Glutamate (+) GABA (-) Substantia nigra Dopamina

DIRECT/INDIRECT LOOPS OF BASAL GANGLIA Premotor/motor cortex Striatum External globus pallidus Thalamus Substantia nigra Direct loop Indirect loop Subthalamic nucleus Internal globus pallidus PATHWAYS GREEN = EXCITATORY RED = INHIBITORY

NEUROMODULATORY EFFECT OF DOPAMINE Direct Pathway: Stimulates Indirect Pathway: Inhibits Overall Excitatory

OTHER FUNCTIONS/LOOPS OF THE BASAL GANGLIA An executive loop may regulate the initiation and termination of cognitive processes such as planning, working memory, and attention. The limbic loop may regulate emotional behaviour. The deterioration of cognitive and emotional function in both Huntington's disease and Parkinson's disease could be the result of disruption of these non-motor loops.

SUMMARY OF MOTOR PATHWAYS

SAME TYPICAL EXAMS QUESTIONS Which of the two following components of the basal ganglia form a functional unit? putamen and globus pallidus Substantia nigra and putamen Putamen and caudate nucleus 2. Complete the following: the lentiform nucleus is composed of……………………………………………….

3. Which of the following statements is NOT true of the functions of the cerebellum? Stores learned sequences of movements Ensures smooth coordination of muscles Regulates postural adjustments during skilled movements

4. In addition to its role in movement control, list 2 other posited functions of the basal ganglia

WHAT TO DO NOW Read the scanned chapter by Ellison (2012), chapter 6, Moving On. This should consolidate your understanding of movement, and the complex pathways involved. Chapter 10 in Atkinson and McHanwell provides a more comprehensive summary. Chapter 2 in Duffy (2007), a text you will use next year also has a good summary