gabriel kreiman [email protected]
TRANSCRIPT
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Human neurophysiology
Gabriel [email protected]
Children’s Hospital Boston, Harvard Medical School
McGovern Institute for Brain ResearchMassachusetts Institute of Technology
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• Genomics, microarrays, transcriptional regulation• Visual object recognition• More info at http://www.mit.edu
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Single neuron recordings in epileptic patients
•Patients with pharmacologically intractable epilepsy
Kreiman, Koch, Fried (2000) Nature Neuroscience 3:946-953
Electrodes
Spike sorting
MRI
•Electrodes implanted to localize seizure focus
•Targets include the hippocampus, entorhinal cortex, amygdala and parahippocampal gyrus
Collaboration with neurosurgeon Itzhak Fried (UCLA) and Christof Koch (Caltech)
Fried et al. J.Neurosurgery 1999
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Inferior temporal cortex
projects to frontal cortex
and the medial temporal lobe (among other
places)
Saleem & Tanaka. J.Neurosci.1996Suzuki. Sem.Neurosci. 1996Miller. Nat.Rev.Neurosci. 2000Logothetis & Sheinberg. Ann.Rev.Neurosci. 1996
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Individual neurons in the human MTL show visual selectivity and visual invariance
Emotional face (100) Object (51) Spatial (105) Animal (46)
Car (17) Face drawing (134) Famous face (100) Pattern (54)
1000 ms
Kreiman, Koch, Fried (2000) Nature Neuroscience 3:946-953Kreiman, Koch, Fried. Nature Neuroscience 2000R Entorhinal Cortex
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Two extreme forms of representation
Fully distributed representation
Every unit responds to every objectEvery object is represented by the
combined ensemble activity
Completely sparse representation(grandmother representation)
Every unit responds to only 1 objectEvery object is represented by 1 neuron
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A neuron selective to 3 different views of Bill Clinton
n=7n=9 n=13 n=5n=14
n=4n=7 n=6
n=7n=11 n=11 n=10
1000 ms
n=4
n=6 n=7
R a
myg
dala
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A neuron selective to 7 different views of actress Jennifer Aniston
Quiroga, Reddy, Kreiman, Koch, Fried. Nature, In PressL Parahippocampal gyrus
ROC area=1
Quian Quiroga, Reddy, Kreiman, Koch, Fried. Nature 2005
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Observations in the human medial temporal lobe
• Neurons are activated during the recall of visual information (Kreiman, Koch, Fried, Nature 2000)
N• Neuronal activity correlates with subjective perception (Kreiman, Koch, Fried,
PNAS 2002)
• Neurons show visual selectivity (Kreiman, Koch, Fried, Nature Neuroscience 2000)
• Sparseness and invariance in the responses of single neurons (Quian Quiroga, Reddy, Kreiman, Koch, Fried, Nature 2005)
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Acknowledgments
Human Recordings
Prof. Rodrigo Quiroga U. Leicester
Eve Isham UCLA
Irene Wainwright UCLA
Prof. Charles Wilson UCLA
Prof. Anatol Bragin UCLA
Leila Reddy Caltech
Prof. Christof Koch Caltech
Prof. Itzhak Fried UCLA
Prof. Tomaso Poggio MIT
Patients
LB, SI, YS, RZ, TD, JG, YK, HM, MS, MM, MM, DF, LA, MF, WO, RS, XV