al Pathways
Visual Streams A"en%on
Dorsal Stream: Vision beyond iden4fica4on
Ventral Stream: Iden4fica4on Hierarchical Organiza4on
Columnar architecture in other visual areas Fujita, Tanaka, Ito, Cheng, Nature (1992) Albright, Desimone, Gross, J Neurophysiol (1984) Direction columns in MT Feature columns in IT
Hierarchical Organiza%on
Single unit recordings in V1: Orienta%on selec%vity V1 data Stimulus orientation (deg)
sponse selectivity: Jennifer Aniston cell Response selec%vity: the Jennifer Aniston cell
Ventral Stream High Level (LOC, IT) Low Level V1- V3
Fusiform gyrus Occipitotemporal sulcus Lateral occipitotemporal gyrus Inferior temporal cortex (IT): all of these regions; lateral occipital cortex (LOC); TE/TEO (monkey) Inferior temporal sulcus
Lingual gyrus Parahippocampal gyrus Collateral sulcus Medial temporal lobe; PPA; TE/TEO;TF;TH monkey
Neural Communica4on Neurons that fire together, wire together Hebbian Theory Spa%al organiza%on Temporal organiza%on
Spa4al organiza4on cells that are grouped together into func%onally unique zones. Reflects func%onal mechanisms connected to other brain areas via long and short sets of pathways (axons of nerve cells)
Temporal organiza4on Firing rate of neurons carry meaningful informa%on
Temporal organiza4on Carried through to levels of fmri signal
Cogni%ve Neuroscience Methods
Franz Gall (1758 1828) Franz Gall s Phrenology 1796
Franz Gall s Phrenology 1796 Wrong about: Bumps traits Right about: Localiza%on
Pa%ent Work/Brain Lesions Broca s and Wernicke s aphasia 1870 s- ish Visual Agnosias 1890 Lissaeuer Appercep%ve and Associa%ve Studies of brain lesions really gained speed in the 1970s
Electrical S4mula4on Human neurosurgery Penfield 1951 Hubel & Weisel 1950s, 1960s, 1970s orientation columns 22
Pa%ent Work/Brain Lesions Visual Agnosias 1890 Studies of brain lesions really gained speed in the 1970s Warrington & Colleagues 1980s - neurophysiology
Brain Lesions As a result of traumas, surgery, infarcts, or diseases Main advantage: causality Disadvantages - Localiza4on uncertainty (affec4ng connec4ons instead of neural center per se) - Specificity (mul4ple/extensive lesions may lead to more than one deficit) - Plas4city (neural reorganiza4on complicates interpreta4on) - Rarity (only very few cases may exist) - Sufficiency but not necessity 24
Cogni%ve Neuroscience Methods Design experiments hypothesis driven inves%ga%ons
Not one ideal technique, but several prety good ones... W. W. Norton
Cogni%ve Neuroscience Methods Design experiments hypothesis driven inves%ga%ons What kinds of ques%ons can we ask?
Cogni%ve Neuroscience Methods (non- humans) Induced lesions Physiology
Intracellular Recording Microelectrode Glass micropipe"e Much smaller %p (<1 micron) Small enough to penetrate the cell wall Insert electrode inside of the neuron Record changes in res%ng poten%al Tells you about the currents entering and exi%ng the neuron Change voltage of the cell and see how the cell reacts
Intracellular Recording
Single Unit Recording Pro Can record from single neurons Can be done in vivo or in vitro Can systema%cally manipulate the condi%ons under which the cell will respond Con Invasive Anesthesia Difficult to do while animal is awake and behaving Requires responses from a large number of neurons to study a system
Mul%- Unit Recording Macro electrode Larger diameter electrode is used Record the responses of a large number of neurons at the same %me Local field poten%als Changes in the res%ng poten%al of the neurons at the dendrites Dipole
Mul% Unit Recording Pro Can record many neurons at a %me Not as invasive Can u%lize awake behaving prepara%ons Con Not as precise as single unit recording Traces can include ar%facts not related to the behavior
Response selectivity: he Jennifer Aniston cell Response selec%vity: the Jennifer Aniston cell
Logothe%s, Pauls & Poggio, 1995
Not one ideal technique, but several prety good ones... W. W. Norton
Electroencephalography (EEG/ERP)
Electroencephalography (EEG/ERP) Pros: Temporal Resolu%on Direct measurement of ac%vity Cons: Spa%al Resolu%on
Magnetoencephalography (MEG) Pros: Temporal Resolu%on Direct measurement of ac%vity Be"er spa%al resolu%on Cons: S%ll, not great spa%al resolu%on
Ques%ons to ask using MEG/EEG Temporal ques%ons Neuroimaging ques%ons with very short inter- s%mulus- intervals