1. Session 3 The Nervous System II: Central NS – Brain PS111 Brain & Behaviour Psychobiology “Things to do with a brain”

3. ... into the Brain

4. l precisely localised information (e.g., fine touch, proprioception): axons reach top of spinal cord (medulla) l Sensory neurons from all over the body (except the head) send (myelinated) axons into the spinal cord l poorly localised information (e.g., temperature, pain): axons synapse immediately with other neurons l Detection & transmission of sensory signals: l Neurons transmitting... into the Brain

5. l Sensory neurons from the head send axons directly into the brain via cranial nerves (e.g., the optic nerve) l All signals transmitted via several ‘relay stations’:... into the Brain eye brain thala- mus optic nerve retina visual cortex

6. l At each stage, signals are in- tegrated with signals from functionally LGN of the thalamus Visual Cortex Retina Brain Photoreceptors Ganglion cells Bipolar cells Optic Nerve l ‘higher’ levels l Sensory neurons from the head send axons directly into the brain via cranial nerves (e.g., the optic nerve) l All signals transmitted via several ‘relay stations’: l same level... into the Brain l ‘lower’ processing levels

7. Information Processing from functionally lower levels from same functional level from functionally higher levels

8. Information Processing from functionally lower levels from same functional level from functionally higher levels

9. Information Processing from functionally lower levels from same functional level from functionally higher levels neuron’s own output

10. Information Processing or no output from functionally lower levels from same functional level from functionally higher levels

11. LGN Visual Cortex Retina Brain Photoreceptors Ganglion cells Bipolar cells Optic Nerve l Sensory neurons from the head send axons directly into the brain via cranial nerves (e.g., the optic nerve) l All signals transmitted via several ‘relay stations’:... into the Brain l At each stage, signals are in- tegrated with signals from functionally l ‘higher’ levels l same level l ‘lower’ processing levels After that, it only gets worse… A lot of information processing takes place even before a signal reaches the brain!

12. Structures of the brain l Functions: Contains several nuclei of the autonomic NS

13. Structures of the brain l Functions: Contains several nuclei of the autonomic NS

14. l The forebrain: a) Diencephalon l Thalamus: Massive structure on top of the midbrain, deep in the centre of the brain Structures of the brain

15. l The forebrain: b) Telencephalon – Cerebral hemispheres l From diencephalon, incoming signals go up to cerebrum l Divided into two highly similar (but not identical) hemi- spheres, each -covered in cerebral cortex (thin layer of neurons) -contains several groups of sub-cortical nuclei (tight cluster of neurons’ cell bodies) Structures of the brain Grey matter & white matter: -Grey matter: Neurons’ cell bodies, i.e., cortex and sub- cortical nuclei -White matter: Neurons’ myelinated axons Functional organisation: each hemispheres mainly receives input from contralateral side of the body sends output to contralateral side of the body

16. l The forebrain: b) Telencephalon – Basal Ganglia l group of nuclei surrounding thalamus l involved in motor control l globus pallidus + putamen + caudate l (putamen + caudate = “corpus striatum”) l Amygdala closely connected to BG (sometimes listed as part of BG) l But functionally part of the limbic system: Structures of the brain

17. Medial view l The forebrain: b) Telencephalon – Limbic System l Several interconnected sub-cortical & cortical structures l Connected to l hypothalamus (via septum) l olfactory system l Function: memory formation & emotion Structures of the brain For- nix Amyg- dala Mammil- lary bodies Hippo- campus Cingulate Cortex “Glass brain” view Hippo- campus For- nix Amyg- dala Mammil- lary bodies Cingulate Cortex

18. l The forebrain: b) Telencephalon – Cortex & Corpus callosum l Cerebral cortex: thin layers of neurons covering the whole hemisphere i.e, not just outside, but inner (‘medial’) surface as well! l Corpus callosum: thick bundle of axons connecting the two hemispheres l Note: virtually all signal transfer between hemispheres done via CC! Structures of the brain

19. l The forebrain: b) Telencephalon – Cerebral Cortex l Highly folded l Gyrus: outward folded (pl. ‘gyri’) l Sulcus: inward folded (pl. ‘sulci’) l Longitudinal fissure: Largest sulcus, separates left & right hemisphere l Smaller sulci: boundaries of cerebral lobes: l Occipital lobe (at the back): Visual perception l Temporal lobe (at the sides): Auditory perception l Parietal lobe (at the top): Somatosensory perception; intersensory & sensory-motor integration l Frontal lobe (at the front): Planning & motor output Structures of the brain

20. l Signal transmission & interpretation Things to do with a brain l Vision: retina  visual cortex (occipital lobe), l Audition: chochlea  auditory cortex (tempo- ral lobe), l Touch, proprioception, etc.: skin, muscles, joints  somatosensory cortex (parietal lobe) l NOTE: All signals are identical (a neuron becoming electrically active) l Signal interpretation depends entirely on the location in the brain where it arrives! l Sensory signals:receptor cells  sensory neurons  (spinal thalamus (diencephalon)  primary sensory cortexcord  )

21. l Topographic representation: l In each sensory area, signals arrive at a position corresponding to the position of the receptor cell: l Somatotopic map: l Signals from the hand arrive in “hand area”, which is next to “arm area”, which is next to “shoulder area”… l Body shape ‘map- ped’ onto somato- sensory cortex l a.k.a “somato-sen- sory homunculus” l Signal transmission & interpretation Things to do with a brain

22. l retinotopic map: visual sig- nals from neighbouring retinal positions arrive at neigh- bouring positions in the primary visual cortex l But: multiple, differing maps exist for each sense modality! l tonotopic map: auditory signals from adjacent areas of the cochlea arrive at adjacent areas in the primary auditory cortex Things to do with a brain l Topographic representation: l In each sensory area, signals arrive at a position corresponding to the position of the receptor cell: l Signal transmission & interpretation R retina LeftRight side of the world around you:

23. l Direction of signal transmission: neurons l transmit signals only in one direction (from dendrites to axon terminals), but l receive signals from different sources: l Signal transmission & interpretation Things to do with a brain -earlier or ‘lower’ processing stages (‘bottom up’ or ‘feed-forward’) -neighbouring neurons in the same area (‘lateral’) -subsequent or ‘higher’ processing areas (‘top down’ or ‘feedback’) l Combination of feed-forward & feed-back signal loops: l information is not just passively ‘forwarded’, l but modified by everything else going on in the brain!

24. Prefrontal Cortex Supplementary & Premotor Cortices Primary Motor Cortex* Somato-sensory Cortex Posterior Parietal Cortex final execution stage planning & monitoring * axons stretch down to spinal cord (‘pyramidal tract’) Things to do with a brain l Finally: Motor output l Cortical motor areas:

25. l Finally: Motor output l Cortical motor areas: Things to do with a brain l Basal ganglia: l modulate movements l particularly involved in selective inhibition of movements l Cerebellum: l involved in maintaining posture & balance l timing of movements l motor learning l Both receive input from (and send output to!) l motor cortex l sensory cortex l various sub-cortical structures l Final motor signals are send down the spinal cord` l massively interconnected with l Sub-cortical motor areas:

26. Hindbrain Midbrain Forebrain Spinal Cord CerebellumMovement & Posture Pons Medulla Continuation of spinal cord; autonomic nuclei TectumPerception & Attention TegmentumMotor functions Cerebral Cortex (cortical lobes) Perception, Action, Cognition... Limbic SystemEmotion & Memory Basal GangliaMotor control Tel- encephalon ThalamusCentral relay station HypothalamusGateway to ES Di- encephalon Input Functions, Output Functions ascending (afferent) descending (efferent)