Brain II: Physiology and Senses Special vs Somatic Senses Olfaction

Brain II: Physiology and Senses Special vs Somatic Senses Olfaction

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. 5

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

General vs special senses CNS vs PNS * * *

general or somatic senses special senses chemical energy taste smell electromagenetic energy thermoreception vision mechanical energy touch hearing and balance General sensation enters the CNS via the sensory component of the general cranial nerves V, VII, IX, X as well as spinal nerves from the rest of the body Special sensation enters the CNS via the special sensory nerves cranial nerves I, II, and VIII. They lack motor components and are located only in the head.

Afferent Pathways to/in brain 18

Chemical senses: G Protein Coupled Receptors 19

Special Sensation The principle of labeled lines Electromagnetic energy Mechanical energy Chemical energy Q: Does an incoming sensory AP reflect the environmental modality that generated it?

The same basic brain areas that: 1) are stimulated by a particular type of environmental energy 2) transduced in a specialized sense organ 3) reaches the brain via a dedicated special sensory cranial nerve can be recognized in all vertebrate brains Cranial nerves I II VIII Special senses Northcutt 2002

Size comparison of of special sense referral areas often allows identification of dominant sensory modalities in non-mammals. Clark et al. 2001 Secondary integration in the cerebrum obscures this pattern in mammals.

Special senses: Olfaction The signal cascade of olfaction in mammals

Shepherd 2006 APs generated by olfactory neurons are integrated in glomeruli of the olfactory bulb.

Olfactory information is relayed from the olfactory bulb to the olfactory cortex and to the hypothalamus, and ultimately to many other parts of the brain.

Olfaction is used in near sensing, remote sensing, and to signal territories or sexual receptivity