Ch 1 4 09 09 2011 GOAL OF THE COURSE to understand how we get mind from brain difficult problem to solve Cognition perception memory social behavior etc in terms of neuronal activity Multiple levels of analysis Behavior Speed accuracy and confusions of discrimination recognition o 1 10th of a second Spontaneous categories preferences that people manifest Brain as a system real estate What brain loci circuits are activated in a certain behavior fMRI Effects of restrictive lesions Neural Coding Single unit activity what are individual neurons doing Population code 10 s of thousands of millions neurons theory neutral net model o Lumping together groups of neurons and coming up with something that they can do CPU can t store two things in one location Biological memory stored in neural tissue don t have to erase what we already have new material gets integrated into network Hippocampus allows new experiences to be integrated with old experiences by adjusting synapse strength Development throughout all levels of life How genetics and experience build a brain Diverse methodologies to try and answer how mind is separate from brain Behavioral and psychophysical testing Analysis of lesions and genetic variation in patient population fMRI and optical imaging Single unit recording mesh electrode plate on brain and can measure stimulate brain Neurotransmitter and hormone level Computational analysis Cerebral cortex does sensory input and output Macaque Cortexo ventral pathway for recognition Can pick up item but cannot tell you what it is o Dorsal pathway for motor Lesion in dorsal pathway cannot pick up an item but can tell you what it is Four lobes occipital temporal parietal frontal o Flattened out each hemisphere equivalent to two medium 36cm diameter pizzas o 100 billion neurons Each neuron in visual cortex receives inputs from 200010000 other neurons needs 200 neurons firing in one dendrite of postsynaptic neuron in less than 2ms FIRE 100 000 neurons mm cubed 800 million synapses mm cubed 3km axons per mm cubed Brain is washed in GABA inhibitory bath conserving energy signals can be selected and sparse neural codes NO SEIZURES Cortex and Vision 50 of macaque and 50 of cortex either exclusively or partially devoted to vision 27 of whole brain Local cortical modules are each performing a different function for vision Submodules are in an area eg Visual recognition has subregions for faces places tools colors Why use modules Neurons need to interact with each other so bring them together so long distances aren t needed less energy and less myelination o Efficient packaging compartmentalization minimizes fiber length volume energy consumption does it faster Does the nervous system minimize fiber length Christopher Cherniak 1994 realized nemotode c elegans could analyze neuron efficiency because we know the complete nervous system and ganglia are arranged linearly o Traveling salesman problem what is the most efficient route o C elegans have optimal arrangement for minimizing axon length o Next best is only 1 worse How do the neurons know where to go C elegans is too close to big bang so trial and error isn t how the neuron position adapted Process o Target neurons signal when they need another neuron to attach chemical attractor progenitor neuron o Recent cooperation and competition from recently generated neurons Do we see evidence of component optimization in mammalian organization Yes Areas that are spatially contiguous have high connectivity seen in visual and motor areas o Limiting factor seems to be spatial contiguity some noncontiguous areas are also highly connected Corpus callosum counters efficiency model wtf Cherniak deduced C elegans are social and some would eat by themselves and some would eat together social difference eating together is there a genetic source of this behavioral difference Big developmental questions How does a brain build itself How does the mind build itself How are the effects of experience incorporated Brain Glial cells send signals into cells that will ultimately become cortex Once strands go up then cells are born that will be activated and crawl along fiber into cortex build a column of cells Radial Unit Model Pasco Rakic in 1988 o Over time 6 layer cortex is built o Top most layer is newest layer added Pruning cell death o A large number of neurons in the cortex die over time purposeful reduction in number of cells No we do not become dumber You are getting rid of neurons that aren t doing much for you and with new space available you sprout a large number of dendrites dendrites up until 20 s Chimp prefrontal cortex more neurons per cubic inch than humans but humans have more dendrites Synaptogenesis synaptic pruning Sensorimotor cortex then parietal temporal cortex then prefrontal cortex are myelinated and etc in that order Hence why decision making is hindered limited until 20 s since prefrontal cortex is myelinated last Behavior Broadbent s information flowchart of human performance as overview of behavior 1958 Senses Short term memory filter rehearsal loop with limited capacity channel not all information retained o Limited capacity channel either goes to long term memory or response selection Need to go through limited capacity channel to long term memory Channel is the same channel for external sensory input as well as internal sensory input daydreaming imagination o After practicing long term memory response occurs Rehearsal loop look up phone number and keep rehearsing it and then type in number but if someone asks you what time it is you forget it distraction sensory and perception Ch 5 09 09 2011 High frequency higher auditory spikes Low frequency lower auditory spikes Tonotopic maps in cortex through fMRI Receptive field for auditory neuron is tuned to a particular position size frequency orientation direction Neurons will fire when stimulated with appropriate stimulus stimulus must match preferred scale of cell Mexican hat tuning profile sound High bandpass spatial frequency sharp outline Low bandpass spatial frequency fuzzy Different scales and then combined to form picture we know Patient DF can use hands visual expression is not okay Found in shower in a coma hypoxia lack of oxygen from CO poisoning When she woke up she couldn t see When boyfriend came in didn t recognize him If person spoke she knew who it was She could see things like a fork but couldn t tell you what it was but if you described a fork she could tell you yeah that