19th August 2013Bio Neurobiology I - Organization of the nervous system1 Organization of the nervous system 2 Raghav Rajan Bio 334 – Neurobiology I August 22nd 2013

19th August 2013Bio Neurobiology I - Organization of the nervous system2 Orienting within the brain – absolute axes and relative axes ANTERIOR (in front) POSTERIOR (behind) INFERIOR (below) SUPERIOR (above) ● Anterior/Posterior, Superior/Inferior – absolute axis system ● Rostral/Caudal, Dorsal/Lateral – relative to the long axis of the brain or spinal cord

19th August 2013Bio Neurobiology I - Organization of the nervous system3 Medial – lateral axes MEDIAL (near the midline) LATERAL (away from the midline) LATERAL (away from the midline) Mark F Bear, Barry W Connors, Michael A Paradiso. Neuroscience: Exploring the brain (2007) – Chapter 7

19th August 2013Bio Neurobiology I - Organization of the nervous system4 Ipsilateral and contralateral – things on the same side or the opposite side IPSILATERAL (same side) CONTRALATERAL (opposite side) Mark F Bear, Barry W Connors, Michael A Paradiso. Neuroscience: Exploring the brain (2007) – Chapter 7

19th August 2013Bio Neurobiology I - Organization of the nervous system5 Planes of brain sections Kandel, Schwartz and Jessell, Principles of Neural Science

19th August 2013Bio Neurobiology I - Organization of the nervous system6 Divisions of the nervous system

19th August 2013Bio Neurobiology I - Organization of the nervous system7 Basal ganglia are a set of nuclei within the brain ● Clearly distinguishable cluster of neurons usually deep in the brain ● Shows up as a some gray matter often surrounded by white matter Kandel, Schwartz and Jessell, Principles of Neural Science

19th August 2013Bio Neurobiology I - Organization of the nervous system8 Basal ganglia consist of 4 nuclei ● Striatum ● Pallidum ● Substantia nigra ● Subthalamic nucleus Kandel, Schwartz and Jessell, Principles of Neural Science

19th August 2013Bio Neurobiology I - Organization of the nervous system9 The basal ganglia form loops with the cortex and thalamus ● Cortex - Basal ganglia- thalamus – cortex loops are important in the initiation and selection of movements ● Normal function disrupted in many diseases – Parkinson's disease, Huntington's disease ● Multiple parallel loops involved in other functions too Kandel, Schwartz and Jessell, Principles of Neural Science

19th August 2013Bio Neurobiology I - Organization of the nervous system10 They are involved in movement selection and movement initiation ● Two pathways: ● Direct pathway – initiates movements ● Indirect pathway – suppresses movements ● Recent optogenetic experiments show this very nicely – Supplementary videos 2 and 3 from /journal/v466/n7306/full/natur e09159.html#supplementary- information Yin and Knowlton, The role of the basal ganglia in habit formation. Nature Reviews Neuroscience (2006)

19th August 2013Bio Neurobiology I - Organization of the nervous system11 Songbirds have served as a good model system for understanding the function of these loops ● Evolutionarily conserved – neuronal morphology, molecular markers, activity patterns, connections ● Specialized portion of this loop appears to be involved only in song learning Doupe AJ et al. Songbirds could teach basal ganglia research a new song. Trends in Neurosciences 2005

19th August 2013Bio Neurobiology I - Organization of the nervous system12 This loop is important for learning and is involved in generating variability required for learning ● Learning of complex movement sequences requires three steps – Exploration using variability – A mechanism to decide “good” and “bad” outcomes – Selectively re-inforce “good” outcomes Doupe AJ et al. Songbirds could teach basal ganglia research a new song. Trends in Neurosciences 2005

19th August 2013Bio Neurobiology I - Organization of the nervous system13 Basal ganglia loops are thought to form parallel circuits that have a number of other functions too ● Parallel loops with high degree of organization Kandel, Schwartz and Jessell, Principles of Neural Science

19th August 2013Bio Neurobiology I - Organization of the nervous system14 Hippocampus and associated structures are involved in learning and memory Mark F Bear, Barry W Connors, Michael A Paradiso. Neuroscience: Exploring the brain (2007) – Chapter 7

19th August 2013Bio Neurobiology I - Organization of the nervous system15 H.M. (Henry Molaison) revolutionized our understanding of function of hippocampus ● Surgery when he was 27 ● Died at the age of 82 ● Could not form new memories ● Only some types of memories were affected ● Could remember most things from before surgery ● CAVEAT: Lesions encompass larger area than just hippocampus Mark F Bear, Barry W Connors, Michael A Paradiso. Neuroscience: Exploring the brain (2007) – Chapter 7

19th August 2013Bio Neurobiology I - Organization of the nervous system16 Diencephalon gives rise to thalamus and hypothalamus Mark F Bear, Barry W Connors, Michael A Paradiso. Neuroscience: Exploring the brain (2007) – Chapter 7

19th August 2013Bio Neurobiology I - Organization of the nervous system17 Thalamus is the “gateway” to the cortex ● All sensory (except olfactory) are relayed to the cortex through the thalamus ● Thalamo-cortico-thalamic loops are believed to be important for consciousness Mark F Bear, Barry W Connors, Michael A Paradiso. Neuroscience: Exploring the brain (2007) – Chapter 7

19th August 2013Bio Neurobiology I - Organization of the nervous system18 Midbrain gives rise to tectum and tegmentum ● Tectum consists of superior and inferior colliculus ● Superior Colliculus gets information from eye and controls eye movements ● Inferior colliculus gets information from the ears Mark F Bear, Barry W Connors, Michael A Paradiso. Neuroscience: Exploring the brain (2007) – Chapter 7

19th August 2013Bio Neurobiology I - Organization of the nervous system19 Midbrain gives rise to tectum and tegmentum ● Tegmentum consists of red nucleus and substantia nigra ● Both are involved in controlling voluntary movement ● Corticospinal tract passes through the midbrain Mark F Bear, Barry W Connors, Michael A Paradiso. Neuroscience: Exploring the brain (2007) – Chapter 7

19th August 2013Bio Neurobiology I - Organization of the nervous system20 Rostral hindbrain gives rise to cerebellum and pons Mark F Bear, Barry W Connors, Michael A Paradiso. Neuroscience: Exploring the brain (2007) – Chapter 7

19th August 2013Bio Neurobiology I - Organization of the nervous system21 Caudal hindbrain gives rise to medulla Mark F Bear, Barry W Connors, Michael A Paradiso. Neuroscience: Exploring the brain (2007) – Chapter 7

19th August 2013Bio Neurobiology I - Organization of the nervous system22 Cerebellum is again involved in modifying movements ● Gets detailed motor information through the pons about the commands that have been sent out from cerebral cortex ● Receives sensory information from the spinal cord about body position, etc ● Can then compare and adjust movements ● Lesions result in uncoordinated movements Mark F Bear, Barry W Connors, Michael A Paradiso. Neuroscience: Exploring the brain (2007) – Chapter 7

19th August 2013Bio Neurobiology I - Organization of the nervous system23 Pons – a “switchboard” for the cerebellum ● Carries information from cerebral cortex to cerebellum ● Also controls a number of vital functions like breathing, sleep, bladder control, swallowing, etc. Mark F Bear, Barry W Connors, Michael A Paradiso. Neuroscience: Exploring the brain (2007)

19th August 2013Bio Neurobiology I - Organization of the nervous system24 Medulla - ● Has motor neurons that control the tongue ● Receives a lot of sensory information from various senses ● A number of other autonomous functions Mark F Bear, Barry W Connors, Michael A Paradiso. Neuroscience: Exploring the brain (2007)