Brain evolved {brain, evolution}.
brain: parts
Brain is an enlargement and opening of spinal cord cranial end. First, slight enlargement formed rhombencephalon. Then, pons (bridge) evolved. Rhombencephalon evolved to myelencephalon and metencephalon. Above pons and further forward, rostrally towards nose, is mesencephalon. From midbrain roof, special motor cerebellum evolved, first becoming large and important in birds. Fourth-ventricle top became midbrain cerebral aqueduct. Rostral to midbrain is forebrain, with diencephalon and telencephalon [Cummins and Allen, 1998].
brain: processes
Neural structures evolved first reflexes, then associations, then feature surfaces and flows, then objects and events, then scenes and trajectories, and then histories and stories over space and time using language [Cummins and Allen, 1998].
brain: tissue
Neural tissue evolved from neuron to interneuron, ganglion, ganglia group, cortex, two-layer paleocortex, four-layer neocortex, and six-layer frontal lobe cortex.
design
Neural tissue and brains evolved opportunistically and did not follow design. Brains are not evolving teleologically to defined final state. Brains do not necessarily work efficiently.
motion
Originally, sensation led directly to motion. Brain evolved to separate perception from motion. Brain further evolved to integrate perception, memory, emotion, and goals. Brain then evolved to have consciousness.
Mammalian cortex has both caudal and rostral reciprocal pathways {dual origin hypothesis}. Birds have hyperstriatum and neostriatum. Hyperstriatum evolved like mammalian cortex. Neostriatum evolved from DVR.
pallium
Top and bottom cerebral neocortex layers are homologous to pallium. Reptile medial pallium evolves to mammal hippocampus major and subiculum. Reptile lateral pallium evolves to mammal olfactory cortex. Pallium receives from olfactory and limbic cortex, caudally.
ventricular ridge
Middle four cerebral neocortex layers are homologous to reptile dorsal ventricular ridge. Dorsal ventricular ridge receives from within itself, rostrally.
Reptiles have dorsal cortical plate {pallium}.
Reptiles have a two-layer ridge {ventricular ridge} {dorsal ventricular ridge} (DVR) behind brain ventricles.
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Date Modified: 2022.0225