Human neurophysiology

Gabriel KreimanGabriel.Kreiman@childrens.harvard.edu

Children’s Hospital Boston, Harvard Medical School

McGovern Institute for Brain ResearchMassachusetts Institute of Technology

• Genomics, microarrays, transcriptional regulation• Visual object recognition• More info at http://www.mit.edu

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

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

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

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

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

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

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)

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