Last Lecture http://www.umich.edu/~psycours/345/ What is Cognitive Neuroscience? Historical Roots Phrenology Modern Neuropsychology: Broca, Wernicke Study of lesion effects: Prism on the mind Experimental vs. clinical neuropsychology
Today’s Lecture Getting around the brain Orientational Terminology Gross Neuroanatomy Maps Cytoarchitectonic Projections Maps
Directional Terms
Planes of Section Frontal plane: coronal section Sagittal plane : medial and parasagittal section Horizontal plane: transaxial or horizontal section
Planes of Section Frontal plane: coronal section
Planes of Section Sagittal plane : medial & parasagittal section
Planes of Section Horizontal plane: horizontal or transaxial section
Photo PET
Major Subdivisions: Forebrain, Midbrain, Hindbrain Medulla Pons Cerebellum Midbrain superior colliculus inferior colliculus Motor nuclei Hindbrain: medulla: motor nuclei of the cranial nerves vital functions & reflexes: respiration, heart rate reticular activating system cerebellum: balance, timing, posture, coordinated movements, cognition?? pons: cranial nerves, superior olive (auditory nucleus) reticular activating system, vestibular nuclei for balance Midbrain: superior and colliculus, oculomotor nuclei
Major Subdivisions: Forebrain, Midbrain, Hindbrain Medulla Pons Cerebellum Midbrain superior colliculus inferior colliculus Motor nuclei Hindbrain: medulla: motor nuclei of the cranial nerves vital functions & reflexes: respiration, heart rate reticular activating system cerebellum: balance, timing, posture, coordinated movements, cognition?? pons: cranial nerves, superior olive (auditory nucleus) reticular activating system, vestibular nuclei for balance Midbrain: superior and colliculus, oculomotor nuclei
Forebrain neocortex/cortex limbic system basal ganglia olfactory system thalamus / hypothalamus
Our primary focus: Neocortex Phylogenetically youngest structure Well developed only in mammals Accounts for 9 billion of the 12 billion neurons in the human nervous system.
Terminology (for a convoluted surface) Fissure: Deep cleft Sulcus: Shallow cleft Gyrus: Ridge Major Landmarks Longitudinal Fissure: separates Left & Right hemispheres Central Fissure: separates parietal and frontal Lateral (Sylvian) Fissure dorsal boundary of temporal lobe
Four Lobes: Named for overlying skull bones Offer "crude" functional (sensory-motor) parse Frontal: voluntary motor control Parietal: somatosensory Temporal: auditory Occipital: visual
Blood Supply to the Brain (highlights) Internal Carotid arteries- supply only cortex anterior cerebral artery middle cerebral artery Vertebral Arteries- supply brainstem, cerebellum and cortex posterior cerebral artery occipital, temporal lobes tectum Neurons are highly metabolic, thus sensitive to oxygen and glucose deprivation Brain uses large fraction of body’s energy resources-- 20% of circulating glucose is used by brain. PET, SPECT, fMRI are all sensitive to local changes in cerebral blood flow. Arterial blood supply to the brain provides different territories of the brain with blood. If there is clogging or infarction, stroke then the regions of cortex supplied by the affected branch will be at risk.
Principles of Cortical Organization: Cytoarchitectonic Maps & Projection Maps system for classifying & defining cortical organization orderly representation on cortical surface structural basis for defining an area's function function can follow closely from structure (e.g. projection maps)
Nissl stain reveals cell bodies (rich in DNA and RNA) Golgi stains reveals axons White matter tracts carrying connections between brain regions: cortical-cortical, cortical thalamic, thalamo-cortical.
Cytoarchitecture Gray matter is 2 mm thick. 6 layers differing in number, type, density of cells. 2 & 4 : receiving layers fibers from sensory and association cortex thicker in sensory cortex 3, 5 & 6: sending layers 3 association cortex and commissures 5 brainstem and spinal cord 6 thalamus thicker in motor cortex Thalamocortical, corticothalamic & Corticocortical connections (intra and interhemispheric)
Cytoarchitectonic Maps: Complex micro-structure of neural tissue Brodmann's (1909) Map Classified regions based on density of cell layers Identified about 50 distinct areas Structural classification --> functional differences system widely used to refer to areas of interest.
Cytoarchitectonic Maps: Complex micro-structure of neural tissue Brodmann's (1909) Map Classified regions based on cell layers Identified 52 areas Structural classification --> functional differences system widely used to refer to areas of interest.
Projection Maps defined by their input What gets mapped depends on the sensory modality vision-- visual space auditory-- pitch (frequency) touch-- body surface
Generic (simplified) Pathway: Properties of Cortical Organization Hierarchical Organization ranking based on modality specificity & complexity of functions Contralateral Organization e.g. LH represents: Right Visual Field Right side of body Right Ear Input Vice versa for RH Functional Segregation “modules” with specialized functions Generic (simplified) Pathway: SENSORY RECEPTOR THALAMIC NUCLEUS PRIMARY CORTEX SECONDARY CORTEX ASSOCIATION CORTEX Association cortex- 75% of all brain tissue thalamic input is via thalamic nuclei that get their input from other cortical areas, not from sensory receptors. this input to association areas is highly processed and multi modal.