1Listen to the audio lecture while viewing these slides1Psychology 372Physiological PsychologySteven E. Meier, Ph.D.Basal Ganglia2Psyc 372 – Physiological PsychologyBasal Ganglia• Does not have direct input or output to the spinal cord• Receives information from the cortex• Sends output to • Brain stem via the thalamus•Cortex3Psyc 372 – Physiological PsychologyPast• Had specific systems involved with movement• Pyramidal• Extrapyramidal• Corticospinal• Other structures including BG4Psyc 372 – Physiological PsychologyToday• Many more parts are involved• Movement problems can also occur with problems in the•Brain stem• Red Nucleus• Cerebellum 5Psyc 372 – Physiological PsychologyConsists of Four Principal Nuclei• Striatum• Globus Pallidus (Pallidum)•SubstantiaNigra• Subthalamic Nucleus6Psyc 372 – Physiological PsychologyStriatum • Has three important subdivisions•Caudate Nucleus•Putamen• Ventral Striatum (Includes Nucleus Accumbens)• Mostly divided by the internal capsule• Are fibers that go from the cortex to the thalamus in both directions.27Psyc 372 – Physiological PsychologyStriatum• Receives most of the fibers from the •Cortex•Thalamus• Brain St em St ructures• Sends fibers to • Globus Pallidus• Substantia Nigra8Psyc 372 – Physiological PsychologyStriatum• All areas of the cortex send excitatory (glutaminergic) fibers to the striatum.• Also gets dopaminergic projections from the midbrain• Fina lly gets seroto nergic inp ut fro m the Raphe Nuclei• Contains mostly GABA neurons• Has two separate parts (called patches)•Matrix•Striosome• Both are separate and have different types of receptors9Psyc 372 – Physiological PsychologyGlobus Pallidus (Pallidum)• Lies medial to the Putamen• Has two segments•External• Internal• Use GABA as a NT.10Psyc 372 – Physiological PsychologySubstantia Nigra• Lies in the midbrain on medial side of the internal capsule• Has a compact zone (pars compacta)• Is a distinct nucleus•Contains•Many Dopamine neurons•Oxidized pigment from Dopamine•Neuromelanin (makes the structure dark)•Increases with age11Psyc 372 – Physiological PsychologySubthalamic Nucleus• Lies below the thalamus• Lies above the substantia nigra• Is closely connected to • Parts of the Globus Pallidus• Substantia Nigra• Uses glutaminergic neurons • Are the only excitatory neurons in BG.• All others are inhibitory12Psyc 372 – Physiological PsychologySubthalamic Nucleus313Psyc 372 – Physiological PsychologySubthalamic Nucleus• Input to the basal ganglia is from the • Primary motor cortex •SubstantiaNigra• Output of the basal ganglia is to• Primary motor cortex• Supplemental motor area• Premotor area• Brainstem motor nuclei (ventromedialpathways) • Cortical Basal Ganglia Loop• Frontal, parietal, temporal cortex send axons to caudate/putamen• Caudate/putamen sends axons to the globuspallidus• Globus pallidus sends information to the motor cortex via thalamic nuclei14Psyc 372 – Physiological PsychologyFunctions• Past - Only motor related functions•Today• Motor•Cognitive•Emotional • Motivated behavior 15Psyc 372 – Physiological PsychologyOutput from the BG • Output is very important• Output neurons discharge at high frequency• Structures• Internal Pallidal Segment• Pars Reticulata of Substantia Nigra • Both tonically inhibit target nuclei in the thalamus and Brain Stem• Modulated by two parallel pathways•Indirect Pathway•Direct16Psyc 372 – Physiological PsychologyIndirect• Is purely Gabainergic• Goes first to external Pallidal Segment • Then goes to subthalamic nucleus• Finally goes to output nuclei in subt halamic nucleus• Contains excitatory glutaminergic neurons 17Psyc 372 – Physiological PsychologyDirect • Striatum to Pallidum• When activated shuts down the tonicly active neurons• Permits the thalamus and cortex to be activated18Psyc 372 – Physiological PsychologyComparisons•Direct • Provides positive feedback • Activation disinhibits the Thalamus • Increases thalamus/cortical activity • Facilitates movement•Indirect• Provides negative feedback• Activation inhibits the thalamus• Has opposing effect• Shuts down movement419Psyc 372 – Physiological PsychologyDopamine• Is very important• Direct are D1 receptors are excitatory• Indirect are D2 receptors are inhibitory• Synaptic actions are different • Both decrease inhibition of thalamocortical neurons • Thus both facilit ate movement• Decrease dopamine in the striatum• A ctivity increases output nuclei increas es• Output nuclei then inhibit thalamocortical neurons • Movement decreases20Psyc 372 – Physiological PsychologyDisorders• Many different types• Parkinson’s syndrome/disease• Huntington’s Disease• Most involve some sort of motor functioning