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Brain and Behavior LECTURE NOTES Part 3 - I got a 4.0 in the class

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University of Pittsburgh

Test 3 Notes Vision – Lecture 17 Human senses = sight, scent, taste, touch, hear - Additionally: balance, pain, kinesthetic sense (body position, motion, & accel.), internal organs (interoception), & electroreception (absent in humans) Different sensory systems – multilevel structures responsible for processing of sensory info - Visual - Auditory - Somatosensory  Vestibular-balance  Gustatory-taste  Olfactory-smell  Ineroceptive/visceral Common plan: sensory r’s  neural relays  primary sensory cortex  assoc. sensory cortices R’s  Neuron 1  Neuron 2  Neuron 3  Neuron 4 …. Sensory R’s: cells located in sense organs; responsible for Transduction - generally separate cells. - Can be specialized structures @ end of peripheral nerve or free nerve endings Transduction – r’s convert (transduce) energy of stimulus into neural activity Receptor fields: region of space serviced by sensory r’s which form the area. - High level sensory neurons have larger receptive field - Size r-field \/ as importance ^ ( higher density = more neurons per area = ^ acuity) Receptor - types: convert specific type of energy to readable form by cell Modality Stimulus Receptor Type Specific Receptor Vision Light Photoreceptors Rods, cones Hearing Air-pressure waves Mechanoreceptors Hair cells (in cochlea) Balance Head motion Mechanoreceptors Hair cells (in semicircular canals) Touch Mechanical, thermal Mechanoreceptors, Meissner, thermoreceptors Pacinian, Ruffini’s corpuscules, Merkel’s disks, free nerve endings Taste Chemical Chemoreceptors Taste buds Smell Chemical Chemoreceptors Endings of olfactory sensory neurons Pain Mechanical, thermal, Nociceptors Free nerve chemical endings Neural relays - # levels before info arrives @ primary sensory cortex - Pathways go through Thalamus - Most complicated – auditory system o Nothing in this class RE olfaction (doesn’t go through thalamus) - Just need to know thalamus filters sensory info arriving at / from cortex Primary Sensory Cortices Visual = occ. Lobe Auditory = temporal love somatosensory = parietal lobe - Process more simple sensory info - Neurons respond to simple stimuli (light bar recognition) Damage  irreversible loss of sensation Association Sensory Cortices - Process more complex sensory info. - Neurons respond to complex stimuli (face rec.) Damage  lack of recognition through senses but sensation still present Sensory Deprivation expt. - Floatation tanks: ST = relaxing & conducive to meditation LT= extended ( >1 hr)  extreme anxiety, hallucinations, bizarre thoughts & depression Vision- Visual System Retina = light-sensitive surface @ back of eye - Consists of neurons & photo-r’s  Sensory r’s = photo r’s Photo r’s  bipolar cells….. doesn’t take place there?  Retinal ganglion cells give rise to optic nerve. - Fovea = region @ center of retina that is specialized for high acuity - Blind Spot = (AKA optic disc) where axons forming optic nerve leave the eye – has no photoreceptors. Photo r’s = convert light energy into neural (electrical signals)….phototransduction Rods = sensitive to low levels of light (dim), used mainly for night vision - Peripheral vision works > fovea @ night. Cones = highly responsive to bright light, specialized for color @ high acuity - fovea = mostly cones - 3 types: Blue, Green, Red  color’s not quite according to wavelength, “relative? Blind-sight = occipitcal lobe affected on one side. - Cannot see things on other side. - Uses ancient midbrain pathway Nasal = closer to nose (inner) Temporal – closer to temple (outer) Info into left nasal visual field  right side of brain. Info into right nasal visual field  left. - Temporal vision fields do not cross (outer right stays on right side…outer left stays on left) o o Optic Chiasm = junction of optic nerves from each eye. 1 & 2 visual cortices – Occ. Cortex = at least 6 different visual regions V1: receives input from thalamus V – V = receive input from V 2 5 1 Dorsal (Back-side) visual stream - Originates @ occ. Cortex  parietal cortex - “How” action is to be guided toward object  “How pathway” Ventral (Belly-side) Visual Stream “temporal” - “what” pathway; identification of objects. Agnosia = not knowing Visual-form agnosia – inability to recognize objects or drawings of objects - Can still copy / (draw objects from memory) – but cannot recognize these later - Can still appropriately shape hand when grasping objets. Color Agnosia – inability to recognize colors. Face Agnosia – inability to rec. races. Injury to “How” Pathway  deficits in visual control of reaching & other movements - Damage to parietal cortex - Can recognize objects normally Processing of Visual Info Seeing shape: retina (ganglian cells) - Respond to presence or absence of light - Provide info about edges, enhance contrast o 1 Visual Cortex (V ) 1 - Simple cells: Orientation detectors: excited by bars of light oriented in particular directions o Rectangular receptive field - Complex cells: maximally excited by bars of light moving in certain directions through receptive field. Visual Stream Occipital lobe  temporal cortex - Cells are maximalls excited by complex visual stimuli - May even be selective to particular faces seen head-on, to faces viewed in profile, to posture of the head, or even facial positions Color: Trichromatic theory- 3 primary colors S-cones (Blue), M- cones (Green), & L-cones (red) - Opponent-Process theory  Red vs. green  Blue vs. Yellow o Opponent processing occurs in ganglion cells in retina as well as in the visual cortex. Audition & Somatosensation- Lecture 18 System R’s & neural relays = important Audition Stimulus: Sound (sound waves) - Variation in air pressure - Molecules displaced forward: leaving area of low pressure Characterized by Amplitude: loudness (magnitude of change in air-molecule density) - Measured in decibels (dB) Frequency: # of compressions / second (perceived as Pitch) - Hz (cycles / second) Complexity: Pure tones = single waves, complex tones = sounds with a mixture of frequencies… corresponds to our perception of timbre, or uniqueness Structure of Ear – outer, middle, inner - Outer Ear: Pinna, auditory canal (amplifies sound a little bit), ear drum - Middle Ear: air-filled chambers comprised of tiny bones (the ossicles- contact / simplify vibrations to oval window) - Inner Ear: cochlea, semicircular canals, vestibules Inner Ear: Cochlea (=snail) - Fluid filled inner-ear structure - Contain organs of cortiauditory r cells (= hair cells) Balance-semicircular canals/ vestibule Auditory r’s = hair cells – convert air pressure waves into neural activity Spiral ganglion - Contain bipolar cells that are connected w/ hair cells & form auditory nerve Mech. E. –(transmitted) neural activity Sound waves in Inner Ear - Different wavelengths travel different distances o Fast frequencies= max displacement near base of membrane o Slow frequencies= max displacement near membrane’s apex @ pitch \/ ---------------------- Sound waves produce a traveling wave that moves all along the basilar membrane of the cochlea Auditory Pathways: Sound waves  [Haircell receptors  bipolar cells] –>produce AP’s sent to axons in the hindbrain –axons tomidbrain –axons tothalamus[Cortex–new synapses axons 2 o Auditory cortex A ] 2 Auditory Cortex A1= w/in Heschl’s Gyrus A2= Wernicke’s area: behind HG at rear of the left temporal lobe that regulates language comprehension; also called posterior speech zone. Lateralization - Functions become localized mainly on 1 side of brain Left hemisphere = mostly assoc. w/ language Hearing Pitch- audible range = (16-20hz) 20kHz <16 Hz = infrasound- windmills/highways (can lead to depression, formerly used as torture in old prisons) > 20 kHz = ultrasound frequencies processed in the cochlea & in the A 1 Special parts of cochlea & A res1onsible for different frequencies Detecting loudness: ^amplitude  ^ fire rate of bipolar cells in cochlea ^ intensity of sound waves triggers ^ intensity of movements of basilar membrane  ^ shearing action of hair cells, leads to more NT release onto bipolar cells - Loudness depends upon both intensity & frequency - Human voice perceived loudness ^ as frequency increases & loudness stays the same *insert threshold of pain / audibility graph* also relative decibels for different activities Somatosensation-------------- soma: body (skin, skeletalmuscles, joints) R’s distributed throughout body rather than concentrated in small specialized locations - Respond to many different stimuli @ least 4 senses, 1. Touch, 2. Body position/motion, 3. Temperature 4. Pain 3 Main modalities – Fine touch / pressure, temp, pain - Areas w/ ^ #’s r’s = ^ sensitivity than areas w/ fewer r’s - 2 types of skin Hairy Skin - \/ density sensory r’s, receptor fields bigger, have ^ hair follicles Glabrous skin - ^ density sensory r’s, receptor fields smaller, have \/ hair follicles Muscle/joint r’s (proprireceptors) - r’s in skeletal muscles – mechanosensitive proprietoreceptors - muscle spindles modality: position – movement sensation - where, direction, & speed Transduction: mechanoreceptors Pressure  deformation of the cell membrane of mechanoreceptors  opening ion channels  electrical response “mechanotransduction” Transduction: thermorecptors - 2 types of r’s - Cold: 5-35 o - Warm: 30-45 Co Temp detection built into structure of channel; can also respond to specific chemical stimuli (menthol-cold, capacin- hot) Dermatomes- area of skin innervated by single spinal vertebrate Dorsal-root ganglion – not just bundled fibers; 2X DR- ganglions / 1X spinal segments - 1 left & 1 right - Contains pseudonunipolar neurons w/ two axonal branches o 1 axon goes to periphery o Other goes to spinal cord- may synapse up to brain or other neurons AP’s propogate 1. [Touch pressure proprioception]  [Skin Dorsal root ganglion]  [Medulla]  [Thalamus]  [Cortex Somatosensory Cortex] 1. Touch/Proprioception - Carries touch information from skin/muscles 2. Temp & pain - Carries info from skin r’s thorugh several relays to somatosensory cortex. T ( C/ F)  skin Nerve endings  [ DR-ganglion]  [Dorsal horns] [Info crosses to contralateral side] ex. Right finger  left somato sensory cortex Touch- medulla Pain/ temp- Lecture # 19 Two main Somatosensory Areas: Primary Somatosensory Cortex- input from thalamus; starts perception construction process - Discovered by Wilder Penfield - Located in Parietal lobe, post-central gyrus Secondary Somatosensory Cortex- behind primary SS.C; continues perceptory construction - projects to frontal cortex 4 different homunculi Control of Movement- difference between skeletal muscles and internal organ muscles - skeletal muscles can be controlled consciously Hierarchy: neocortex, brainstem, spinal cord PF cortex –(sends info to) motor neurons in SSC…motor control assoc. w/ somatosensation Basal Ganglia: comes before PF cortex and receives signals from motor cortex…allows for adjustability Cerebellum: comes before brain stem and receives signals from PF cortex and PM cortex. maintains movement accuracy & performs error correction… Tourettes = over excitation of nervous system (motor parts? Maybe) PF cortex (movements planned)  PM cortex (movements sequenced)  Motor cortex (movements executed)  corticospinal tract - looking @ blood flow in brain region shows activation Fibers = corticospinal track; starts at brainstem Lateral – controls limbs & digits; crosses to otherside of brainstem Ventral – controls trunk muscles; doesn’t cross Motor neurons project to muscles in the body - connected with sensory neurons either directly or through interneurons to form reflex arc. - Motor / interneurons can be envisioned as homunculus representing innervated muscles.(extends from shoulder to fingers as distance from center of ventral horn increases) Limbs  extensor (extend out from body)…..flexor (moves limbs towards body) - Connections between interneurons/motor neurons to coordinate complementary action (extensor neuron inhibitrs flexor neuron?) Spiral reflexes – involuntary & nearly instantaneous movement in response to stimuli…no info from cortex required - Sensory receives info, transmitted to motor neuron, which sends info to muscle Monosynaptic (knee-jerk effort) – just 1 synapse….sensory & motor neurons… Polysynaptic (pain reflex) – sensory neuron  excitatory or inhibitory interneuron (dorsal/ventral roots)  motor neuron * starts @ pain receptors (skin), ends @ bicept muscle. Central Pattern Generators (CPG’s) - Neuronal circuits which can generate coordinated rhythmic flexion and extension of the limbs, as well as associated postural adjustments. - Fundamentally complete walking/running requires participation of supra-spinal centers to control balance & direction, although these centers appear to act through CPG circuits in the SC Scratch reflex: animal’s automatic response to stimulus to scratch it to try and remove it Dorsal horn: sensory structures Dorsal roots: axons of sensory neurons ventral horn: contains cell bodies of motor neurons Ventral roots: axons of motor neurons Self-Study Lecture #20 Pain- experienced through somatosensory stimulation/system - Receptors = nociceptors (free nerve endings in skin muscles tooth pulp, ear…) o Axons of nociceptors = smaller in diameter & unmyelinated…why? o Sensitized w/ repeated stimulation - Prostaglandins = released from (which tissues…inflamed or surrounding area?) tissues o Increase sensitization o Asprin stops synth of P’s Pathway: nociceptor fires AP’s down axon –(synapse) dorsal root ganglion –(synapse) dorsal horn takes it into SC… enters SC and divides into 3 branches (still on axon…) —(synapse) spinal neurons Neurotransmitter = SUBSTANCE P (excitatory or inhibitory?) for each of the 3 axons….not the same NT as for non-pain receptor TOUCH pathways…. - 3 axon branches w/ Sub
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