Brain and Behaviour: BI2CV1 Lecture PDF

Brain and behaviour BI2CV1 Comparative Vertebrate Biology Dr Manabu Sakamoto [email protected] The vertebrate brain Vertebrates are defined by the presence of a spinal cord and a segmented brain. The brain (along with the spinal cord) is the centre of the...

Brain and behaviour BI2CV1 Comparative Vertebrate Biology Dr Manabu Sakamoto [email protected] The vertebrate brain Vertebrates are defined by the presence of a spinal cord and a segmented brain. The brain (along with the spinal cord) is the centre of the nervous system: central nervous system. Vertebrates concentrate brain functions in the head: Injurymap, CC BY 4.0 cephalisation. Vertebrate brain structure The vertebrate brain comprises three main divisions: Hindbrain (rhombencephalon) Mylencephalon Metencephalon Cerebellum [[::User:Nrets|Nrets]], CC BY-SA 3.0 Midbrain (mesencephalon) Tectum (optic tectum/lobe) Forebrain (prosencephalon) Diencephalon Telencephalon Cerebrum Butler & Hodos 2005. Wiley Vertebrate brain evolution The basic brain structure (three divisions) is common across vertebrates. O C G O Sugahara et al. 2017. Develop Growth Differ 59: 163-174 Dupret et al. 2014. Nature 507: 500–50 Hindbrain Hindbrain (rhombencephalon) The hindbrain is an extension of the spinal cord. No clear distinction as is often Cerebellu suggested. m Controls essential functions such as respiration and heartbeat. The hindbrain comprises: Medulla oblongata Pons Cerebellum: Medulla oblongat Balance a Coordination Smooth execution of rapid movement Patrick J. Lynch CC BY 2.5 Zebrafish UCL: http://zebrafishucl.org/brain-regio Midbrain Midbrain (mesencephalon) The midbrain links the sensory, motor and integrative components of the hindbrain with those of the forebrain. The midbrain comprises: Tectum: Dorsal part Butler & Hodos 2005. Wiley Tegmentum: Ventral part Isthmus: Boundary (transitional area) between midbrain and hindbrain Zebrafish UCL: http://zebrafishucl.org/brain-regio Midbrain tegmentum Tegmentum is the ventral portion of the midbrain and is separated from the hindbrain by the isthmus. Parts of the tegmentum consist of rostral continuation of the hindbrain. The tegmentum is a gateway for: Incoming sensory information Outgoing motor responses to and from the forebrain Zebrafish UCL: http://zebrafishucl.org/brain-regio Midbrain tectum The tectum forms the roof of the midbrain. It comprises Optic tectum Torus semicircularis Zebrafish UCL: http://zebrafishucl.org/brain-regio Midbrain tectum The midbrain tectum comprises: Auditory pathway Optic tectum Receives senses from visual and somatosensory (bodily sensation) systems. Visual pathways Torus semicircularis Receives senses from auditory and lateral line (hydrodynamic). The optic tectum and torus semicircularis projects rostrally to the forebrain Somatosensory pathways Descending motor pathways (diencephalon). Butler & Hodos 2005. Wiley Midbrain tectum Zebra fish larva Spatial mapping of senses Optic tectum and torus semicircularis map senses An example of spatial mapping by the optic from visual, somatosensory, tectum: being aware of something in your auditory and lateral line Elisa Galliano: 10.5281/zenodo.3926507 peripheral vision (hydrodynamic) sensory systems. Spatial awareness of sensory origin. Ben-Tov et al. 2013. J Neruphys 110: 748-759 Helmbrecht et al. 2018. Neuron 100: 1429-14 Forebrain Forebrain (prosencephalon) Neocortex: six- layered neural The forebrain comprises: Cerebral cortex: outer layer of tissue, making up 90% of cerebral cortex Diencephalon cerebrum in mammals Thalamus Hypothalamus Pineal gland Cerebrum Pituitary gland Telencephalon Pallium (Cerebrum) Hippocampus Amygdala OpenStax, CC BY 4.0 Naumann et al. 2015. Curr Biol 25: 317–321 Telencephalon Telencephalon structures are broadly homologous in vertebrates. The mammalian cerebral cortex (neocortex) arose from the dorsal pallium of other vertebrates. Cerebra l cortex Naumann et al. 2015. Curr Biol 25: 317–32 Mammalian cerebral cortex The mammalian neocortex is organised into areas, layers and columns. Areas are dedicated to processing sensory information Layers are composed of different neurons Lodato & Arlotta 2015. Annu Rev Cell Dev Biol 31: 699- Mammalian cerebral cortex vs avian pallium Birds can be as intelligent as mammals but do not have a neocortex. The avian pallium has layered neuronal circuitry similar to mammalian neocortex. Stacho et al. 2020. Science 369: eabc55 Associative areas of the brain Language and communication Speech Broca’s area of the frontal lobe Comprehension Wernicke's area of the temporal lobe Leuthardt et al. CC BY 3.0 Memory Hippocampus Spatial memory Encoding memory Converting short- to long-term memory Amygdala Emotional memory OpenStax College, CC BY 3.0 Basal ganglia Cognition Learning Motor control and activities Visual pathways in mammalian brains Visual information is received on the retina. Visual information travels through optic tracts to the LGN. Visual information is then relayed to the primary visual cortex of the cerebral cortex, Thalamu s where it is processed. (midbrai n) Two visual pathways: dorsal ‘where’ stream and ventral ‘what’ stream. Visual pathways in avian brains Visual associative areas in bird brains are in the pallium. Birds also have two visual pathways: Tectofugal (‘what’) pathway Object classification = visually recognise objects Thalamofugal (‘where’) pathway Mainly responsible for answering ‘where the target is’. Track targets and estimating their distance from the target. E: entopallium Rt: rotundus GLd: the nucleus geniculatus lateralis par dorsalis Niu et al. 2022. Avian Research 13: 100023 Olfaction: Sense of smell The olfactory bulb is responsible for the sense of smell. Enlarged olfactory bulbs associated with keen sense of smell. Bear et al. 2016. Curr Biol 26: 1039–1049 Evolution of vertebrate brain Lamanna et al. 2023. Nat Ecol Evol 7: 1714–1728 Olfactory acuity in dinosaurs Olfactory bulb size in Tyrannosaurus rex T. rex had exceptionally large olfactory bulbs. Turkey vultures also have T. relatively large rex OB. So T. rex was a scavenger! Turkey vulture Witmer & Ridgely. 2009. Anat Rec 292: 1266–1296 Grigg et al. 2017. Sci Rep 7: 17408 A, Majungasaurus; B, Allosaurus; C, Tyrannosaurus; D, Struthiomimus; E, Deinonychus; F, Archaeopteryx Zelenitsky et al. 2009. Proc R Soc B 276: 667–67 Was T. rex a scavenger? There is ample evidence for bone eating. Trace fossils. Cranio-dental adaptations. Had enlarged olfactory bulbs, meaning a good sense of smell Beneficial for sniffing out carcasses. Couldn’t run fast enough to catch prey. Running fast also increased the risk of fatal injuries. Olfactory bulb size in modern birds Common name Olfactory ratio Top ranks dominated by Snow petrel 0.372 tubenoses Kiwi 0.343 Wilson’s storm petrel 0.333 (Procellariiformes; petrels, Leach's storm petrel 0.330 albatrosses, shearwaters) Small shearwaters 0.309 Kakapo 0.302 Great shearwater 0.300 Black-vented shearwater 0.294 Antarctic prion 0.293 Turkey vulture 0.287 Black-footed albatross 0.286 Cape petrel 0.275 Northern fulmar 0.271 Relative olfactory ratio Olfactory ratio is correlated T. rex with body size. Olfactory ratio for turkey Alligato vulture is as expected for a r bird of its body size. Alligator has relatively large olfactory lobes for its size. T. rex does also seem to Turkey vultur have higher olfactory ratio e than expected for its size. Olfactory bulb size in Tyrannosaurus rex Most vultures have typical T. rex relative OB sizes. Birds with large relative OB Alligato sizes tend to be the r Procellarifor seagoing procellariiforms ms (albatrosses, petrels and sheerwaters and storm petrels). So large OB is not Turkey vultur associated with e scavenging! Rates of relative OB size evolution Having said that, there is a burst of evolution in relative OB size at the base of Tyrannosaurs Tyrannosauridae. Similarly, there is a burst of evolution at the base of Procellariiformes. So tyrannosaurs do indeed have significantly large OBs. What that means is up for debate! Procellariiformes T. rex had good visual acuity! T. rex had stereoscopic vision. Snout is Overlapping field of views in the between both eyes. way! This is in part allowed by a snout morphology that is constricted dorsally. Orbits are facing forwards. T. rex likely had good depth perception Contrast with Allosaurus Large, wide snout obscures vision Extra: T. rex only needed to outrun prey. Fossil evidence does show T. rex attacks on prey species. Healed bite mark on Edmontosaurus tail. T. rex tooth embedded in a hadrosaur tail vertebra, surrounded by healed bone growth. T. rex could outrun hadrosaurs and these are just failed attempts? Hadrosaurs could outrun T. rex?