T2 L6. Anatomy and function of the Basal Ganglia (CR).pptx

Anatomy and function of the basal ganglia Dr Charlotte Rae School of Psychology [email protected] Learning objectives • Identify anatomical landmarks associated with the basal ganglia • Describe the role of the basal ganglia in the hierarchical motor control system • Describe the direct and indir...

Anatomy and function of the basal ganglia Dr Charlotte Rae School of Psychology [email protected] Learning objectives • Identify anatomical landmarks associated with the basal ganglia • Describe the role of the basal ganglia in the hierarchical motor control system • Describe the direct and indirect pathways • Describe how neurotransmitters influence activity within the pathways • Describe the link between pathophysiology and associated movement disorders (Dr Ganesalingam) Contents • Anatomy of the basal ganglia • Function of the basal ganglia - motor - limbic - executive function • Pathways of activity in the basal ganglia • Neurotransmitters in the basal ganglia • Preparation for understanding pathophysiology in clinical syndromes • Further online resources Hierarchy of motor control Level Function Structures High Strategy Middle Tactics Association areas of neocortex and basal ganglia Motor cortex, cerebellum Low Execution Brainstem, spinal cord The basal ganglia: the filter of the brain Basal ganglia anatomy caudate nucleus thalamus putamen globus pallidus Basal ganglia anatomy Basal ganglia anatomy Basal ganglia anatomy Basal ganglia anatomy thalamus { caudate putamen globus pallidus substantia nigra subthalamic nucleus Basal ganglia anatomy Globus pallidus is split into pars externa and pars interna Pallidum = globus pallidus internal + external Lentiform nucleus = putamen + globus pallidus Corpus striatum = caudate + putamen + pallidum Divided by INTERNAL CAPSULE: white matter of ascending and descending tracts Neostriatum = dorsal striatum (motor striatum) = caudate + putamen Basal ganglia anatomy Basal ganglia anatomy putamen globus pallidus caudate thalamus Basal ganglia anatomy 3D orientation Basal ganglia: interface with cortex Cerebral cortex Thalamus Striatum Basal ganglia Pallidum Basal ganglia loops Basal ganglia loops striatum caudate putamen Motor loop: movement filter Cerebral cortex Thalamus Striatum Basal ganglia Pallidum The Direct Pathway (Excitatory = GLUTAMATE) excitatory (Inhibitory = GABA) inhibitory GPe Globus pallidus external GPi Globus pallidus internal STN Subthalamic nucleus The Direct Pathway cortex excitatory striatum thalamus inhibitory GPe Globus pallidus external direct pathway PROMOTE movement GPi GPi Globus pallidus internal STN Subthalamic nucleus The Indirect Pathway cortex excitatory striatum indirect pathway thalamus inhibitory GPe GPe Globus pallidus external STN WITHHOLD movement GPi direct pathway GPi Globus pallidus internal STN Subthalamic nucleus The Hyperdirect Pathway cortex excitatory hyperdirect pathway striatum indirect pathway thalamus inhibitory GPe GPe Globus pallidus external STN PAUSE movement GPi direct pathway GPi Globus pallidus internal STN Subthalamic nucleus Pathway Demonstrations Please welcome our BASAL GANGLIA NUCLEI Who will demonstrate the pathways with BALLOONS Pathway Demonstrations At each pathway stage, I will ask audience to INSTRUCT THE NUCLEI excitator y (GLUTAMATE) OR inhibitor y (GABA) The Direct Pathway cortex excitatory striatum thalamus inhibitory GPe Globus pallidus external GPi Globus pallidus internal GPi STN Subthalamic nucleus The Direct Pathway cortex excitatory striatum thalamus inhibitory GPe Globus pallidus external GPi Globus pallidus internal GPi STN Subthalamic nucleus The Direct Pathway cortex excitatory striatum thalamus inhibitory GPe Globus pallidus external direct pathway GPi GPi Globus pallidus internal STN Subthalamic nucleus The Direct Pathway cortex excitatory striatum thalamus inhibitory GPe Globus pallidus external direct pathway GPi GPi Globus pallidus internal STN Subthalamic nucleus The Direct Pathway cortex excitatory striatum thalamus inhibitory GPe Globus pallidus external direct pathway PROMOTE movement GPi GPi Globus pallidus internal STN Subthalamic nucleus The Indirect Pathway cortex excitatory striatum thalamus inhibitory GPe GPe Globus pallidus external STN GPi GPi Globus pallidus internal STN Subthalamic nucleus The Indirect Pathway cortex excitatory striatum thalamus inhibitory GPe GPe Globus pallidus external STN GPi GPi Globus pallidus internal STN Subthalamic nucleus The Indirect Pathway cortex excitatory striatum indirect pathway thalamus inhibitory GPe GPe Globus pallidus external STN GPi GPi Globus pallidus internal STN Subthalamic nucleus The Indirect Pathway cortex excitatory striatum indirect pathway thalamus inhibitory GPe GPe Globus pallidus external STN GPi GPi Globus pallidus internal STN Subthalamic nucleus The Indirect Pathway cortex excitatory striatum indirect pathway thalamus inhibitory GPe GPe Globus pallidus external STN GPi GPi Globus pallidus internal STN Subthalamic nucleus The Indirect Pathway cortex excitatory striatum indirect pathway thalamus inhibitory GPe GPe Globus pallidus external STN GPi GPi Globus pallidus internal STN Subthalamic nucleus The Indirect Pathway cortex excitatory striatum indirect pathway thalamus inhibitory GPe GPe Globus pallidus external STN WITHHOLD movement GPi GPi Globus pallidus internal STN Subthalamic nucleus The Hyperdirect Pathway cortex excitatory hyperdirect pathway striatum thalamus inhibitory GPe GPe Globus pallidus external STN GPi GPi Globus pallidus internal STN Subthalamic nucleus The Hyperdirect Pathway cortex excitatory hyperdirect pathway striatum thalamus inhibitory GPe GPe Globus pallidus external STN GPi GPi Globus pallidus internal STN Subthalamic nucleus The Hyperdirect Pathway cortex excitatory hyperdirect pathway striatum thalamus inhibitory GPe GPe Globus pallidus external STN GPi GPi Globus pallidus internal STN Subthalamic nucleus The Hyperdirect Pathway cortex excitatory hyperdirect pathway striatum thalamus inhibitory GPe GPe Globus pallidus external STN GPi GPi Globus pallidus internal STN Subthalamic nucleus The Hyperdirect Pathway cortex excitatory hyperdirect pathway striatum thalamus inhibitory GPe GPe Globus pallidus external STN PAUSE movement GPi GPi Globus pallidus internal STN Subthalamic nucleus Pathway Demonstrations Thank you to our BASAL GANGLIA NUCLEI Pathways Summary • Cortex striatum excitatory • Striatum outputs • Thalamus inhibitory cortex excitatory • The inhibition of thalamus prevents movement • Reducing inhibition of thalamus facilitates movement Pathways Conundrum • How does striatum ‘know’ if a motor plan is to be promoted (direct pathway) or prevented (indirect pathway?) • We have a lot of options, always changing, so movement plans are NOISY. How do the basal ganglia achieve their filter? Pathways Conundrum: transmitters • How does striatum ‘know’ if a motor plan is to be promoted (direct pathway) or prevented (indirect pathway?) • We have a lot of options, always changing, so movement plans are NOISY. How do the basal ganglia achieve their filter? 2 POPULATIONS OF STRIATUM NEURONS with specialised DOPAMINE receptors Substantia nigra Dopamine is released by the substantia nigra Substantia nigra substantia nigra Striatum neurons & dopamine STRIATUM medium spiny neurons with specialised DIRECT D1 DA ramps up MSN excitation DOPAMINE receptors INDIRECT D2 DA dampens down MSN excitation Striatum neurons & dopamine STRIATUM medium spiny neurons with specialised DIRECT D1 DA ramps up MSN excitation DOPAMINE receptors INDIRECT D2 DA dampens down MSN excitation = release of DA tips pathways towards promotion of movement Striatum neurons & acetylcholine STRIATUM interneurons DIRECT D1 that use ACETYLCHOLINE ACh dampens down ACh opposes MSN excitation effects of DA INDIRECT D2 ACh ramps up MSN excitation Striatum neurons & acetylcholine STRIATUM interneurons DIRECT D1 that use ACETYLCHOLINE ACh dampens down ACh opposes MSN excitation effects of DA INDIRECT D2 ACh ramps up MSN excitation = tips pathways towards prevention of movement Pathway balance Essentially: The ‘balance’ of activity between the 2 medium spiny neuron populations determines the likelihood of movement taking place through the direct & indirect pathways This balance is regulated by dopamine & acetylcholine And influenced by the cortical inputs to the striatum Pathway balance *depending on dopamine & acetylcholine Pathway balance SN cortex excitatory D2 D1 ACh striatum indirect pathway thalamus inhibitory GPe GPe Globus pallidus external STN GPi direct pathway GPi Globus pallidus internal STN Subthalamic nucleus SN Substantia nigra Learning objectives • Identify anatomical landmarks associated with the basal ganglia • Describe the role of the basal ganglia in the hierarchical motor control system • Describe the direct and indirect pathways • Describe how neurotransmitters influence activity within the pathways • Describe the link between pathophysiology and associated movement disorders (Dr Ganesalingam) Further online resources “The Basal Ganglia – Direct and Indirect Pathways” Brains Explained https://www.youtube.com/watch?v=NcIWYCkKwVA Anatomy and function of the basal ganglia Dr Charlotte Rae School of Psychology [email protected]