Week 3 Psych 169 Lecture Notes PDF

Today’s Lecture:  Split-brain patients  Alien hand syndrome  Functional organization of the corpus callosum  Hearing, touch, olfaction in split-brain patients Split Brains & Split Consciousness  Epilepsy: a debilitating disease that could cause seizures several times per day ...

Today’s Lecture:  Split-brain patients  Alien hand syndrome  Functional organization of the corpus callosum  Hearing, touch, olfaction in split-brain patients Split Brains & Split Consciousness  Epilepsy: a debilitating disease that could cause seizures several times per day  Tonic-Clonic Seizure (Previously known as Grand Mal Seizure)  Absence Seizure (Previously known as Petit Mal Seizure)  Epilepsy: a debilitating disease that could cause seizures several times per day  Cutting the corpus callosum prevents the seizure from spreading from one hemisphere to the other hemisphere of the brain  William Van Wagenen  Archives of Neurology and Psychiatry, 44, 740- 759.  In 1939, 10 people between the ages of 10 and 43, all with epilepsy, traveled to the University of Rochester Medical Center  All had violent and uncontrollable seizures  Corpus Callosotomy: Radical new Surgery to cut the corpus callosum (untested in humans)  He got the idea from two seizure patients with small tumors on the corpus callosum  Tumor grew, destroyed corpus callosum  Seizures eased up (no loss of consciousness)  Corpus callosum: 200 million nerve fibers (axons)  Cut to prevent seizures from spreading from one side of brain to the other The callosum tissue seen in a healthy brain (bright white in top image) retracts after a corpus callosotomy, leaving just the ventricle (black).  What happens to their IQ?  IQ remains the same  What happens to their personality?  Same personality  Verbal and problem-solving ability?  Same  Patients recover and live normal life What actually changes in split-brain patients?  Roger Sperry (1913-1994) – Caltech – Nobel Prize (1981)  Information from the left visual field goes to the right hemisphere, and from the right visual field to the left hemisphere  Sperry: – Split-brain patient is two conscious people – Two free wills  Is one of the two in charge?  “…the minor hemisphere constitutes a second conscious entity that is characteristically human and runs along in parallel with the more dominant stream of consciousness in the major hemisphere” (Sperry, 1968).  Michael Gazzaniga (UCSB) at first agreed with the Dual consciousness idea  Later experiments made Gazzaniga doubt this (dual consciousness)  The left brain is the “interpreter”  Right hand: Points to chicken  Split-brain patient: “It goes with the chicken”  Left hand points to shovel (snow)  Why did you point to the shovel?  “Because it is used to clean the chicken shed”  Right brain: points to shovel (snow)  Left brain interprets the action to fit a story  Left brain = the interpreter  Steven Pinker (Harvard): Left brain is the baloney generator (makes up stories)  Walk +  Right brain receives instruction to walk  Patient starts walking  Experimenter: “Why are you walking?”  Patient (left brain): “To go get a soda.”  What about the right hemisphere?  Is it conscious with a sense of self?  Gazzaniga: Only the left hemisphere has high-level consciousness (language, beliefs)  Is the right hemisphere a zombie?  Right hemisphere has: – Linguistic ability of a 3-year-old child – Reasoning capacity of a chimpanzee – Is it conscious?  Imagine one hemisphere sees a red screen  The other sees a blue screen +  Ask: “how many colors are there?  Both hemispheres responds: “only one”  How many streams of consciousness are there?  Two  Can you teach one half of the brain to play a game (chess) against the other half  Donald Mackay taught each half of a split- brain patient’s brain to play a game  Number guessing game: – I choose a number (0 to 9) – You guess the number – I say: “up”, “down”, or “OK”  The right and left brains could play the game against each other  Is this evidence for two conscious systems? Alien hand syndrome  Alien hand syndrome (Intermanual conflict): One hand acts on its own  Seen in split-brain patients, but also results from stroke, tumor, … that damage the frontal lobe  Functional dissociation of thought and action Patient G.H. (Brain & Cognition, 2011) Stroke occurring when part of the anterior cerebral artery (ACA) becomes blocked causing tissue damage to the corpus callosum Functional Organization of the Corpus Callosum  Is it necessary to cut the entire corpus callosum to treat epileptic seizures?  For some patients the corpus callosum was sectioned in stages over several months  Functional organization of the corpus callosum?  Posterior regions: transfer basic sensory information: vision, audition, somatosensory  Anterior regions: transfer of attention and higher cognitive information  Middle regions: motor functions Motor coordination in split- brain patients  How do split-brain patients walk?  Left brain controls right leg, right hand, etc.  Soon after surgery, patients can walk, run, play piano, dance,…  How is this possible?  One possibility is cross cuing: Non-neural interhemispheric communication in split-brain patients  Analogous to how conjoined twins may operate (two brains, one body)  Abby and Brittany Hensel  Each controls one arm, one leg, …  Ride a bike, drive, play softball, swim  How do they coordinate (automatically)?  Picking up on subtle behavioral cues  Brittany perceives a movement initiated by Abby and unconsciously coordinate  Other ways in which the left and right brains may communicate in split-brain patients:  Subcortical pathways (brainstem, cerebellum) Brainstem Cerebellum Hearing, touch, and olfaction in split-brain patients  Auditory (present high-low-high tones to left ear) High-Low-High Low-Low-High  Patient can’t identify (using speech) the melodic pattern  But can “hum” the pattern (motor system) Can’t Identify Can hum  Tactile: Patient closes eyes, given object (apple) to left hand  Can’t verbally identify  Can draw apple with left hand  Olfaction  Smell of garlic to right nostril  Olfactory receptors project ipsilaterally  Patient looks disgusted  Says: “I smell nothing”  Her left hand pointed to correct object (garlic)  Today’s Lecture  Damaged brains  Korsakoff’s syndrome (Amnesia)  Neglect (Anosognosia)  Perception of time  The binding problem  Damaged brains (Other disorders of consciousness) Memory disorders  Korsakoff’s syndrome  Most common form of amnesia  Toxic effects of alcohol & Thiamine (Vit. B1) deficiency  Destroys parts of the thalamus and frontal lobes  Oliver Sacks’ patient Jimmie G. Sergei Korsakoff  Typically results in both retrograde and anterograde amnesia  Anterograde amnesia  Can’t form new long-term memories  Short-term memory intact  Can hold a conversation or remember a phone number long enough to dial  If distracted, memory is gone  Isolated in a very brief present  Retrograde amnesia  Loss of long-term memory from time of accident to a variable time in the past  Accidents, concussions, trauma  Blank period shrinks with recovery  Classical conditioning remains intact – Puff of air to eye paired with a sound – Happy to see a friend, while claiming to have never met them (positive feeling about friend)  Procedural learning remains intact – Can drive a car or type – Can also pick up new skills – Using a computer mouse improves each time, while claiming to never have seen the mouse  Amnesia: dissociation between performance & consciousness (e.g., unaware that they have ever used a mouse) Is memory a precondition to consciousness?  Wada Test (make half the brain unconscious)  Wada test  Use drugs to knock out whole hemispheres (make it unconscious)  Why? Locate language/memory areas Avoid damaging them  Sodium amytal injected into artery Juhn Wada  Goes to one hemisphere  Patient is given memory and language test  Drug lasts only a few minutes  British neuropsychologist Paul Broks performed Wada test on 19 year old Naomi  Epileptic patient  Surgery to remove damaged amygdala and hippocampus on her right side  Make sure the equivalent structures on the left were functioning fine Paul Broks Amygdala Hippocampus  Conversation when left brain was knocked out:  Doctor: “Can you name the days of the week?”  Naomi: “Fa-fa-fa-fa…”  “Can you count backwards from 10?”  “Tem, nipe, ape, ape, ape…”  Neglect (Deficit of Awareness)  Anosognosia: a type of neglect in which a person is unaware of their own disability  Complete paralysis on one side of the body (stroke), but patient is unaware  “I can move perfectly if I want to”  “I know I’m paralyzed on my left side but can I have my knitting needles to knit something?”  Part of her minds knows, another does not  Anosognosia: damage to right parietal lobe  Anosognosia is sometimes accompanied by asomatognosia, a form of neglect in which patients deny ownership of own body parts  Most extreme example of neglect is Anton’s syndrome  Blind, yet insist that they can see  “My eyes are not that good, but I enjoy Gabriel Anton (1858 - 1933) watching TV”  Thinks that watching TV means listening to TV for everyone  Hemifield neglect or unilateral neglect:  Lose half of their visual world  Don’t realize left-hand side of the world exists  Results from right parietal damage  One woman applied makeup only to the right side of her face, and ate only from the right side of her plate  One man only shaved one side of his face  Copy a drawing:  Emotional stimuli can influence attention to left side  Priming  Hemifield neglect can be partially explained by deficit of attention  They don’t attend to left side of the world  Treatment: Trained to turn from side to side (lighthouse) Perception of time  We don’t always experience things in the order in which they actually happen in the world  Experiments show that conscious awareness of the timing of events may be different than how they occur  The flash lag effect  Explanations for flash lag:  Visual system predicts where the moving stimulus is going so as to allow for neural processing delays  The flashed extra piece is stationary  Moving segment is projected forward in time (relative to the stationary piece)  – The Phi phenomenon  Problem: the motion trajectory has to be calculated in the brain after the second dot has occurred  Cutaneous rabbit  Taps are perceived as continuous series moving up the arm  Why are taps 2 to 5 experienced as moving up the arm when tap 6 has not happened yet?  How did the brain know where the next tap was going to be?  Perception of time and space is not always a match to actual events  The brain generates a conscious percept after events have occurred to make sense of what has happened The binding problem – V4: color processing – V5 (MT): motion processing  Color is perceived before motion by 80 ms  Why does everything seem in sync?  The brain binds the color and motion and shape of the ball into a unified experience  How?  Attention is required for binding  When attention is overloaded, wrong features can be bound together: illusory conjunctions  Rushing along a street and you see a black dog  Later realize it was a golden Labrador  sitting next to a black garbage bag  Damage to parietal cortex, which affects attention, can cause binding deficits  How does the brain bind features?  By synchrony of neural oscillations across areas of cortex (for example v4 and v5)  Especially Gamma waves: 40 Hz  EEG and ECoG studies: Gamma oscillations are much stronger during feature binding  Evidence from Synesthesia (binding of wrong information)  Synesthesia – Letters & numbers written in black ink have color qualia  More common in women (6 times as many)  More likely to be left handed  Neurologically normal (intelligence, etc.)  Genetically transferred (X-Chromosome)  Hear sound in response to smell  Smell or taste in response to touch  Feel touch in response to sight  “What a yellow voice you have”  Almost any combination of senses  Specific to an individual (two synesthetes usually disagree about color associations)  Synesthesia involving 3 senses is possible but very rare  Is it just a memory?  “I see perfectly clearly.”  “I kind of see it, I kind of don’t”  “No, it’s not like a memory. I see the number as being clearly red but I also know it isn’t; it’s black. So it must be a memory, I guess”  Maybe they’re just faking it?  Test to see if it’s truly perceptual  What causes synesthesia?  Cross wiring between brain regions  V4 (color) is close to area that codes for number shapes  TPO (temporal parietal occipital junction) receives input from V4 and from temporal cortex  fMRI of the brain of a synesthete (rear view)  V4 (brain’s color processing area) active when synesthete is looking at black numbers  This area is not active in people with normal vision