NSC 5104 Systems Neuroscience The main textbook will

NSC 5104 Systems Neuroscience The main textbook will be Neuroscience by Purves et al. Professors may assign additional reading. The examination will consist of: (a) a presentation- 20% (b) a three hour written exam- 50% (c) a research essay – 30% The research essay will be on a specific neural system; the topic will be chosen in consultation with Dr. Maler. The brief presentation will be on selected research papers and also chosen in consultation with Dr. Maler.

The Organization of the Vertebrate Brain 1 Our Family Tree Striedter Vertebrates evolved from cephalochordates: animals with a cartilaginous notochord but no backbone. Some major highlights include the evolution of jaws, muscular limbs and protected eggs. The brains of all vertebrates follow the same plan. However different groups have evolved amazing specializations. This course will emphasize structure-function relations that connect neuronal networks to behavior. A comparative approach helps put this topic in perspective.

The Organization of the Vertebrate Brain 2 Butler and Hodos A closer look at where we come from. Most neuroscience is done on a very limited range of species: rodents, monkeys, etc. This gives a false idea of the true range of capabilities of the nervous system.

The Organization of the Vertebrate Brain 3 Brain size is log-linearly related to body size. Animals above the line may be “smarter”; but does that make them more fit? Size is not everything. Brain differentiation may be a strong indicator of neural “processing power’. Striedter

The Vertebrate Brain Plan 1 Butler and Hodos The CNS develops from a neural tube. The fluid filled core remains in the adult as the ventricular system. The major subdivisions of the CNS are found in all vertebrates: Forebrain (telencephalon + diencephalon, midbrain (mesencephalon) and hindbrain (rhombencephalon). Different parts of the CNS hypertrophy or atrophy depending on the species. A second division is useful in the mid and hindbrain: the alar plate and basal plates. The alar plate forms the roof and is generally sensory while the basal plate is motor. Useful terms for localization are: dorsal vs ventral and rostral vs caudal. Striedter

The Vertebrate Brain Plan 2 The brain of a fish. The telencephalon is relatively small compared to the tectum, a midbrain visual center. In mammals, the tectum is called the Superior Colliculus. Butler and Hodos Sensory input is stereotyped: in most vertebrates, sensory input reaches the pallium (dorsal telencephalon) via relays in the thalamus. Olfactory input enters the pallium directly from the olfactory bulb. Motor output is usually from mid and hind brain, except in mammals where the pallium (cortex) becomes dominant. The cortex assumes ever greater importance in more “advanced” vertebrates. The cerebellum also evolves to regulate both brainstem and forebrain neural processing.

The Vertebrate Forebrain 1 A B A. C B. C. D. Striedter The forebrain of most vertebrates (except fish) inverts so that the hippocampus (medial pallium) ends up curled up inside dorsal pallium (neocortex). Evolution of the hypothalamus. Pallium (cortex in mammals) is always separate from subpallium (basal ganglia and septum mostly). One distinguishing feature is dense acetylcholine esterase staining in subpallium. Note that pallium in mammals is layered while in birds (and reptiles) it is not. The pallium is involved in learning: as it expands in mammals, it projects massively to lower brain structures and exerts ever more control of all neural function.

The Vertebrate Forebrain 2 Cortex increases its surface area without a large increase in volume by folding: the folds are called gyri. Striedter The thalamus is the gateway to cortex and so evolves together with cortex. As cortex evolves areas that are not directly sensory or motor, thalamus evolves regions that connect cortex to cortex (and not to sensory input). One good example is the primate pulvinar.

The Vertebrate Forebrain 3: Sensory Visual areas increase enormously in the primate. And secondary visual areas increase the most. These are involved in extracting very complex information from images. In other words, the retina of a rabbit is just as complex as that of a primate; the primate extracts a lot more information from that retina and this is reflected in the increase in primary and secondary visual cortices. Striedter

A The Vertebrate Forebrain 4: Motor B A. B. C C. Striedter Frontal cortex increases far more than primary motor cortex; it is involved in complex control including working memory. Input regions for vocalizations and output motor areas for producing vocalizations are present in monkeys; these regions are greatly expanded in humans and involved in language comprehension and production. Cortex directly controls motor systems in primates that, in other mammals, are only indirectly controlled via brainstem.