Visual Streams. A"en%on

Transcription

1

2 al Pathways

3 Visual Streams A"en%on

4 Dorsal Stream: Vision beyond iden4fica4on

5 Ventral Stream: Iden4fica4on Hierarchical Organiza4on

6 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

7 Hierarchical Organiza%on

8 Single unit recordings in V1: Orienta%on selec%vity V1 data Stimulus orientation (deg)

9 sponse selectivity: Jennifer Aniston cell Response selec%vity: the Jennifer Aniston cell

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11 Ventral Stream High Level (LOC, IT) Low Level V1- V3

12 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

13 Lingual gyrus Parahippocampal gyrus Collateral sulcus Medial temporal lobe; PPA; TE/TEO;TF;TH monkey

14 Neural Communica4on Neurons that fire together, wire together Hebbian Theory Spa%al organiza%on Temporal organiza%on

15 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)

16 Temporal organiza4on Firing rate of neurons carry meaningful informa%on

17 Temporal organiza4on Carried through to levels of fmri signal

18 Cogni%ve Neuroscience Methods

19 Franz Gall ( ) Franz Gall s Phrenology 1796

20 Franz Gall s Phrenology 1796 Wrong about: Bumps traits Right about: Localiza%on

21 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

22 Electrical S4mula4on Human neurosurgery Penfield 1951 Hubel & Weisel 1950s, 1960s, 1970s orientation columns 22

23 Pa%ent Work/Brain Lesions Visual Agnosias 1890 Studies of brain lesions really gained speed in the 1970s Warrington & Colleagues 1980s - neurophysiology

24 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

25 Cogni%ve Neuroscience Methods Design experiments hypothesis driven inves%ga%ons

26 Not one ideal technique, but several prety good ones... W. W. Norton

27 Cogni%ve Neuroscience Methods Design experiments hypothesis driven inves%ga%ons What kinds of ques%ons can we ask?

28 Cogni%ve Neuroscience Methods (non- humans) Induced lesions Physiology

29 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

30 Intracellular Recording

31 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

32 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

33 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

34 Response selectivity: he Jennifer Aniston cell Response selec%vity: the Jennifer Aniston cell

35 Logothe%s, Pauls & Poggio, 1995

36 Not one ideal technique, but several prety good ones... W. W. Norton

37 Electroencephalography (EEG/ERP)

38 Electroencephalography (EEG/ERP) Pros: Temporal Resolu%on Direct measurement of ac%vity Cons: Spa%al Resolu%on

39 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

40 Ques%ons to ask using MEG/EEG Temporal ques%ons Neuroimaging ques%ons with very short inter- s%mulus- intervals