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Unformatted text preview: The 2 Hemispheres of the Brain right emotional holistic intuitive left logical calculating linguistic right Strokes Evidence left pessimistic overly emotional overly noticing of even nonserious problems optimistic unemotional un-noticing of serious injury and disability anosognosia Really, really, really oversimplified....... oversimplified....... Not complete garbage....... garbage....... Lateralized Brain Functions
Lateralized = one hemisphere "controls" task processing controls" language - left (Broca and Wernicke's) left-handers - sometime right - language Localized versus Lateralized
Localized = contiguous portion of the brain controls task amnesia - selective memory loss patient GR who forgets identity for years recovers it on operating table (Schacter) aperceptive agnosia faces - right hemisphere visual motor tasks - right good vision, no ability to recognize shapes, forms associative agnosia good vision, good shape, object recognition problems Man who mistook his wife for a hat (Sacks) recognition of a glove dyscalculia cannot do simple caluculations left angular gyrus (Ramachandran) prosopagnosia - selective memory loss cannot recognize faces Capgras Syndrome aphasia Broca's - cannot speak (tan) - left frontal Wermicke's aphasia - can't undertand - left temporal think someone you love has been replaced by an imposter no other signs of dementia alexia cannot read Let's be critical ....are these disorders evidence for localization? Let' agraphia cannot write 1 A few ways to move information across cerebral hemispheres - corpus callosum vision - optic chiasm audition - a subcortical mess! sensory motor - spinal cord emotion - anterior commissure Cortex - Corpus Collosum bridge of 80 million fibers split brain patients Vision - Optic Chiasm right hemifield- left hemisphere left hemifield - right hemisphere Sensory Motor Audition Subcortical Mess!
pain, temperature 2 Emotion - Anterior Commissure primates - some vision also touch, vibration Physiological Difference Right more white matter mylinated axons... more holistic axons longer.... talk more broadly... Split Brain Patient corpus collosum severed severe epilepsy....tumors generally normal.... but under the right circumstances clever experiments.... Left more gray matter cell bodies more local axons shorter less extensive connectivity What the experiments can tell us How the hemispheres communicate visual, verbal, and tactile information How they communicate emotion How they coordinate motor activity How they exist somewhat independently... Question 1 Visual, Verbal, and Tactile Coordination Roger Sperry (Nobel Prize) M. Gazzaniga split brain patients 3 Part 2 Part 1 - cup flashed to left hemisphere (via right visual field) - experimenter - "what did you see?" see?" - patient - "a cup" cup" - spoon flashed to right hemisphere (via the left visual field) - experimenter - "what did you see?" see?" - patient - "nothing" nothing" - visual signal passed through optic chiasm to right hemisphere - left hemisphere....has no knowledge of the visual signal hemisphere... - patient responds "nothing" nothing" - did the patient "see" the spoon? see" - yes..... yes... NORMAL - visual signal passed through optic chiasm to left hemisphere - patient responds "cup" cup" Part 3 - spoon flashed to right hemisphere (again) - experimenter - "what did you see?" see?" - patient - "nothing" nothing" - put patient's left hand in the bag.... patient' bag... - Experimenter - "Find the object you saw" saw" - Patient - pulls a spoon out of a bag with a bunch of objects REASON - picture of the spoon is in the right hemiphere - left side of the body is controlled by the sensory-motor cortex (parietal) in the right hemisphere! Question 2 - Emotion Processing M. Gazzaniga & LeDoux (78) split brain patient special patient who could read a bit from both hemispheres (PS) Part 1 - patient saw emotionally charged words - words presented to the left hemisphere Devil - Experimenter - "Was the word good or bad?" bad?" - Patient - "bad" bad" Experimenter - "What was the word?" word?" - Patient - "devil" devil" Part 2 - patient saw emotionally charged words - words presented to the right hemisphere Devil - Experimenter - "Was the word good or bad?" bad?" - Patient - "bad" bad" - Experimenter - "What was the word?" word?" - Patient - "what word?" word?" 4 Conclusion Question 2 - Emotion processing M. Gazzaniga & LeDoux (78) Emotional stimuli "make it across" even without across" the corpus collosum split brain patient How? Anterior Commissure? Commissure? - patient saw emotionally upsetting vignettes to the right hemisphere...... hemisphere... - patient - developed a fear of Gazzaniga - no ability to explain why! Question 3 Systematic Coordination of Motor Activity Alien hand phenomenon Kurt Goldstein (1930's) - well-known neurologist case study- middle aged woman normal except..... would try to strangle herself with her left hand right hand would act to fight off the left hand -episodic experience giving rise to emotion -inaccessible by language -emotion itself -accessible to language explanation autopsy revealed a corpus callosum lesion motor coordination of the left side of the body (i.e., left hand) right hemisphere (more emotional) latent suicide tendencies instruct the left hand left hemisphere - unaware of right's "intentions" fights off the attack Implication about will and self???? Are there two of us???? 5 Case 2 - dressing example.... example... - right brain more expressive than left - left brain more conservative Question 4 Independent Existence case of young man asked what he would like to do with his life left hemisphere responds differently than right architect race car driver...... Abilities/Interpretation the left-hemisphere interpreter Left-hemisphere interpreter Gazzaniga & LeDoux picture matching task the right-hemisphere statistician a picture to left hemisphere - chicken a picture to right hemisphere - snow storm match board available to both responses made with hands Results left hand matches right hemisphere picture shovel for snow storm right hand matches left hemisphere picture chicken foot for chicken subject asked... why did your left hand pick the shovel? left hemisphere makes up an answer! 6 Right-hemisphere statistician Wolford study light 80% on right light 20% on left we distribute responses to match probabilities 68% correct Rats "maximize" and push right 100% 80% correct right hemisphere - uses rat, statistician strategy Things the mind/brain does... Getting information about the outside world to the inside and into a form in which it can be used.... What is perception? definition - process by which physical energy from the environment impinging on the senses is converted into electrochemical energy by the senses and processed by the brain for the purpose of effective and adaptive interaction with the world A complete understanding..... neuroanatomy neurophysiology psychology computational problem philosophy Neuroanatomy "hardware" or "wetware" - neural substrate kinds of cells connectivity between cells wiring of the relevant brain areas Neurophysiology receptive fields of cells in relevant brain regions questions organization of processing parallel versus serial processes hierarchical special purpose 7 Psychology What can we perceive? What do we do well? What do we do badly? What do we do with perception...tasks we solve? Computational Problem What is the problem? What is the information available to solve the problem? How can the information be quantified and used to solve the problem? Can this give insight into biological and/ or psychological solutions to the problem? Steps of Perceptions light
Sense Vision Audition Touch Energy Light Sound pressure
Mechanical /temperature Vision dimensions intensity - photons per unit area per unit time wavelength composition color, hue spectra Organ Eyes Ears Body Transduction Brain Rods/cones Hair cells Lots Occipital Temporal Parietal Parietal Olfactory bulb, etc. Gustation Chemical Olfaction Chemical Tongue Taste buds Nose Hair cells saturation - percentage of white light emitted versus reflected light emitted versus reflected light
illuminant sensor reflector 8 The pattern of light on the retinae is: complex function of:
illuminant reflectance properties of the object viewer position Philosophy Marr (1982) Vision What is the purpose of vision? create a 3D map of the world in the brain Vision is the solution - what is the problem? Gibson (1966) vision is for action navigation, manipulation, exploration What is the purpose of the eye? to get a good image.... What is a good image? focus - resolution contrast - light level, not too much, not too little light sensitivity - detection Gregory (1997). Eye and Brain. Tradeoff between resolution - focus light level - detection 9 Gregory (1997). Eye and Brain. The right balance depends on the environmental constraints and tasks of the creature ... What about us? Gregory (1997). Eye and Brain. The eye is like a camera, but... It moves ......not randomly.... Gregory (1997). Eye and Brain. Gregory (1997). Eye and Brain. Kinds of eye movements vergence convergence, divergence saccades ballistic movements, scan, reading pursuit, tracking optokinetic nystagmus jitter The eye is like a camera, but... there are two of them binocluar vision stereopsis 10 Parts of the eye in functional terms Focus - refraction of light -17 mm focal length cornea -shape - 42 diopters Parts of the eye in functional terms Light level Pupil - quantity of light - emotional lens - changeable shape - fine tuning - accomodation - 15-20 diopters Pigment epithelium - absorbs excess tapetum - scatters excess Landmarks on the Retinae optic disc optic nerve exits the retina blind spot - demo + fovea point of highest acuity Receptor rods "black and white" high light sensitivity too sensitive to light to operate during daylight cones color vision 3 kinds L wavelength R, 550 M wavelength G, 535 S wavelength B, 419 absorption spectrum peak 500 nanometers green low light sensitivity daylight not useful at night 11 2 Visual systems scotopic - rod vision photopic - cone vision mesopic - rod/cone vision rods and cones horizontal cells bipolar cells amacrine cells ganglion cells optic nerve axons of ganglion cells Circularly Symmetric Receptive Fields Receptive fields as convolution operators Simple picture -+ - + + + -- + + + On-center off-surround Off-center on-surround 12 Simple Edge detector Simple picture as 2D array of pixels Convolution operator -> edge detector
1 -1 Pixel = 20 Pixel = 100 100 100 20 20 1 -1 Simple Edge detector 1 -1 Result 1 -1 Convolution operator -> edge detector- "mask"
100 100 20 20 Convolution operator -> edge detector- "mask" 20*1 + 100*(-1) = -80 1 -1 Pixel 1 = 100*1 + 100*(-1) = 0 Pixel 2 = 100*1 + 20*(-1) = 80 Pixel 1 = 100*1 + 100*(-1) = 0 Pixel 2 = 100*1 + 20*(-1) = 80 Pixel 3 = 20*1 + 20*(-1) = 0 Pixel 3 = 20*1 + 20*(-1) = 0 100 w1x1 w2x2 W1=1 W2=-1 axon 0 All receptive fields work this way! Only the complexity and dimensionality of the operators will change Swixi 100 w1x1 w2x2 20 w1x1 20 w2x2 80 Swixi axon Swixi axon 0 13 + - 1 -1 1 -1 1 0 0 -1 14 0 1 -1 0 + - + - + - 15 ...
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- Fall '07
- Cognitive Science, optic chiasm, right hemisphere