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The Journal of Neuroscience, September 3, 2008, 28(36):8865-8872; doi:10.1523/JNEUROSCI.1640-08.2008
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Behavioral/Systems/Cognitive
Latency and Selectivity of Single Neurons Indicate Hierarchical Processing in the Human Medial Temporal Lobe
Florian Mormann,1,2 Simon Kornblith,1 Rodrigo Quian Quiroga,1,3 Alexander Kraskov,1,4 Moran Cerf,1,2 Itzhak Fried,2,5,6 andChristof Koch1 1Division of Biology, California Institute of Technology, Pasadena, California 91125, 2Department of Neurosurgery, University of California, Los Angeles, Los Angeles, California 90095, 3Department of Engineering, University of Leicester, Leicester LE1 7RH, United Kingdom, 4Institute of Neurology, University College London, London WC1N 3BG, United Kingdom, 5Functional Neurosurgery Unit, Tel-Aviv Sourasky Medical Center, Tel-Aviv 64239, Israel, and 6Sackler Faculty of Medicine, Tel-Aviv University, Tel-Aviv 69978, Israel
Correspondence should be addressed to Dr. Florian Mormann, California Institute of Technology, Division of Biology, MS 216-76, 1200 East California Boulevard, Pasadena, CA 91125. Email: fmormann{at}yahoo.de
Neurons in the temporal lobe of both monkeys and humans show selective responses to classes of visual stimuli and even to specific individuals. In this study, we investigate the latency and selectivity of visually responsive neurons recorded from microelectrodes in the parahippocampal cortex, entorhinal cortex, hippocampus, and amygdala of human subjects during a visual object presentation task. During 96 experimental sessions in 35 subjects, we recorded from a total of 3278 neurons. Of these units, 398 responded selectively to one or more of the presented stimuli. Mean response latencies were substantially larger than those reported in monkeys. We observed a highly significant correlation between the latency and the selectivity of these neurons: the longer the latency the greater the selectivity. Particularly, parahippocampal neurons were found to respond significantly earlier and less selectively than those in the other three regions. Regional analysis showed significant correlations between latency and selectivity within the parahippocampal cortex, entorhinal cortex, and hippocampus, but not within the amygdala. The later and more selective responses tended to be generated by cells with sparse baseline firing rates and vice versa. Our results provide direct evidence for hierarchical processing of sensory information at the interface between the visual pathway and the limbic system, by which increasingly refined and specific representations of stimulus identity are generated over time along the anatomic pathways of the medial temporal lobe.
Key words: single-unit recordings; object recognition; parahippocampal gyrus; entorhinal cortex; hippocampus; amygdala
Received April 15, 2008; revised June 23, 2008; accepted July 12, 2008.
Correspondence should be addressed to Dr. Florian Mormann, California Institute of Technology, Division of Biology, MS 216-76, 1200 East California Boulevard, Pasadena, CA 91125. Email: fmormann{at}yahoo.de
This article has been cited by other articles:
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J. Neurosci., June 10, 2009; 29(23): 7599 - 7606.
[Abstract] [Full Text] [PDF]
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