Brain Architecture and Function Parts Size and Cognition

Brain Architecture and Function Parts Size and Cognition

Q: In what way has paedomorphosis been important in human evolution?

Brain Architecture F F F F H H 3

Q. How d we get to this point? Evolutionary trends Hindbrain: relatively smaller Midbrain: relatively smaller Forebrain: relatively larger especially the cerebrum (neocortex) 4

Brain organization DEVELOPMENT Prosencephalon Telencephalon (cerebrum) Diencephalon (eyes, pituitary, hypothalamus, thalamus, epiphysis) Mesencephalon Rhombencephalon Metencephalon (pons, cerebellum) Myelencephalon (medulla) FUNCTION Forebrain Cerebrum Thalamus Hypothalamus Midbrain Hindbrain Pons Medulla Cerebellum 5

Medulla oblongata Highway of axons to/from brain Nuclei (cell bodies) that control autonomic functions breathing heart rate blood pressure swallowing coughing/sneezing Damage is usually fatal Hindbrain Most cranial nerves emerge from brain stem

Pons ( bridge ) On top of brain stem Connects cerebral hemispheres with contralateral hemispheres of cerebellum Wakefulness and alertness Damage can lead to sleeplessness or hyperalertness Hindbrain

Cerebellum ( little brain ) As many neurons as rest of brain! Monitors sensory input from body and coordinates with outgoing motor commands from cerebrum Gross motor function Posture/balance muscle tone coordination Damage leads to loss of control on contralateral side Hindbrain

Midbrain Connects brainstem to forebrain Has nuclei that coordinate/integrate body movements with forebrain (damage -->Parkinson s) Eye movements (sup colliculus) Pain (Periaqueductal gray region, PAG) Reward, addiction, movement Motor coordination (red nucleus) Small in mammals

Diencephalon Thalamus ( inner chamber ) - relays all sensory information to cerebrum (except smell) - Also involved in awareness & learning Hypothalamus - Controls release of hormones by pituitary gland - Homeostasis of thirst, heart rate, blood pressure Forebrain

The cerebrum accomplishes most complex cognitive functions, especially thinking & awareness Forebrain - Receives/processes sensory information - Complex cognitive processes Language Thinking Awareness Memory Consciousness Etc

Topology of cerebral function Forebrain Frontal lobes Motor functions or movements (posterior) Memory/recognition Emotional regulation Motor aspects of speech Parietal lobes Integrate stimuli (e.g., vision and balance) Temporal lobes Sensory input from ears Visual/word memory Occipital lobe Sensory input from eyes

Limbic system Forebrain Cortical/subcortical structures around brainstem: generation/regulating emotions; learning

Two hemispheres are linked by the corpus callosum Forebrain A thick bundle of myelinated axons

Phineas Gage A moral man, Phineas Gage Tamping powder down holes for his wage Blew his special-made probe Through his left frontal lobe Now he drinks, swears, and flies in a rage. 15

Brain Size Q: Does body mass predict brain mass? Q: How does brain size differ among vertebrates? Northcutt 2002

Brain Size Q: Does body mass predict brain mass? Q: How does brain size differ among vertebrates? Slope = 1.0 Slope 0.67 Northcutt 2002

Q: Which mammals have the largest percent of body mass represented by brain? The largest absolute brain? The largest EQ? * * log brain mass * log body mass

Estimating the size of a brain subunit: the neocortex of mammals: 1) rhinal fissure placement hedgehog tree shrew monkey 2) cerebral sulcation rhinal fissure

Q: What aspect(s) of bird behavior correlate most strongly with a large telencephalic ( forebrain) fraction of the brain? Burish, Kueh, and Wang. 2002.

Pigeons have a telencephalic fraction of 0.552.. 0.552 Burish, Kueh, and Wang. 2002.

and can distinguish paintings by Picasso and Monet. Watanabe et al. 1995

Brain to body connection Q. How does brain receive and send information?

Signal Transduction An environmental stimulus Surface neurons are exposed to an environmental stimulus The environmental stimulus generates a receptor potential If the receptor potential exceeds threshold, it initiates an AP Sensory input is relayed to the central nervous system Q: How do environmental stimuli initiate APs? AP to the CNS

Signal Transduction Q: How do environmental stimuli initiate APs? See text box, p. 338