Human neurophysiology Gabriel Kreiman - PowerPoint PPT Presentation

Human neurophysiology Gabriel Kreiman Gabriel.Kreiman@childrens.harvard.edu Children’s Hospital Boston, Harvard Medical School McGovern Institute for Brain Research Massachusetts Institute of Technology

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

Single neuron recordings in epileptic patients MRI Electrodes •Patients with pharmacologically intractable epilepsy Fried et al. J.Neurosurgery 1999 •Electrodes implanted to localize seizure Spike sorting focus •Targets include the hippocampus, entorhinal cortex, amygdala and parahippocampal gyrus Collaboration with neurosurgeon Itzhak Fried (UCLA) and Christof Koch (Caltech) Kreiman, Koch, Fried (2000) Nature Neuroscience 3 :946-953

Inferior temporal cortex projects to frontal cortex and the medial temporal lobe (among other places) Saleem & Tanaka. J.Neurosci. 1996 Suzuki. Sem.Neurosci. 1996 Miller. Nat.Rev.Neurosci. 2000 Logothetis & 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 :946-953 Kreiman, Koch, Fried. Nature Neuroscience 2000 R Entorhinal Cortex

Two extreme forms of representation Fully distributed representation Completely sparse representation (grandmother representation) Every unit responds to every object Every object is represented by the Every unit responds to only 1 object combined ensemble activity Every object is represented by 1 neuron

A neuron selective to 3 different views of Bill Clinton n=9 n=14 n=13 n=7 n=5 n=7 n=6 n=6 n=7 n=4 n=4 n=7 n=11 n=10 n=11 R amygdala 1000 ms

A neuron selective to 7 different views of actress Jennifer Aniston ROC area=1 Quian Quiroga, Reddy, Kreiman, Koch, Fried. Nature 2005 Quiroga, Reddy, Kreiman, Koch, Fried . Nature, In Press L Parahippocampal gyrus

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 Prof. Christof Koch Caltech Prof. Itzhak Fried UCLA Prof. Tomaso Poggio MIT Human Recordings Leila Reddy Caltech Prof. Rodrigo Quiroga U. Leicester Eve Isham UCLA Prof. Charles Wilson UCLA Irene Wainwright UCLA Prof. Anatol Bragin UCLA Patients LB, SI, YS, RZ, TD, JG, YK, HM, MS, MM, MM, DF, LA, MF, WO, RS, XV