A quantitative study of gamma-band activity in human intracranial recordings triggered by visual stimuli

Authors

  • Jean-Philippe Lachaux,

    1. Laboratoire de Neurosciences Cognitives et Imagerie Cérébrale (LENA), CNRS UPR 640, Hôpital de La Salpêtrière, 47 Blvd de l'Hôpital,75651 Paris cedex 13, France
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  • Eugenio Rodriguez,

    1. Laboratoire de Neurosciences Cognitives et Imagerie Cérébrale (LENA), CNRS UPR 640, Hôpital de La Salpêtrière, 47 Blvd de l'Hôpital,75651 Paris cedex 13, France
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  • Jacques Martinerie,

    1. Laboratoire de Neurosciences Cognitives et Imagerie Cérébrale (LENA), CNRS UPR 640, Hôpital de La Salpêtrière, 47 Blvd de l'Hôpital,75651 Paris cedex 13, France
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  • Claude Adam,

    1. Laboratoire de Neurosciences Cognitives et Imagerie Cérébrale (LENA), CNRS UPR 640, Hôpital de La Salpêtrière, 47 Blvd de l'Hôpital,75651 Paris cedex 13, France
    2. Unité d'Epilepsie, Hôpital de La Salpêtrière, 47 Blvd de l'Hôpital,75651 Paris cedex 13, France
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  • Dominique Hasboun,

    1. Laboratoire de Neurosciences Cognitives et Imagerie Cérébrale (LENA), CNRS UPR 640, Hôpital de La Salpêtrière, 47 Blvd de l'Hôpital,75651 Paris cedex 13, France
    2. Unité de Neuroradiologie, Hôpital de La Salpêtrière, 47 Blvd de l'Hôpital,75651 Paris cedex 13, France
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  • Francisco J. Varela

    1. Laboratoire de Neurosciences Cognitives et Imagerie Cérébrale (LENA), CNRS UPR 640, Hôpital de La Salpêtrière, 47 Blvd de l'Hôpital,75651 Paris cedex 13, France
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: Dr F. J. Varela, as above.
E-mail: fv@ccr.jussieu.fr

Abstract

This paper studies gamma-band responses from two implanted epileptic patients during a simple visual discrimination task. Our main aim was to ascertain, in a reliable manner, whether evoked (stimulus-locked) and induced (triggered by, but not locked to, stimuli) responses are present in intracranial recordings. For this purpose, we introduce new methods adapted to detect the presence of gamma responses at this level of recording, intermediary between EEG-scalp and unicellular responses. The analysis relies on a trial-by-trial time–frequency analysis and on the use of surrogate data for statistical testing. We report that visual stimulation reliably elicits evoked and induced responses in human intracranial recordings. Induced intracranial gamma activity is significantly present in short oscillatory bursts (a few cycles) following visual stimulation. These responses are highly variable from trial to trial, beginning after 200 ms and lasting up to 500 ms. In contrast, intracranial-evoked gamma responses concentrate around 100 ms latencies corresponding to evoked responses observed on the scalp. We discuss our results in relation to scalp gamma response in a similar protocol [Tallon-Baudry et al. (1996) J. Neurosci., 16, 4240–4249] and draw some conclusions for bridging the gap between gamma oscillations observed on the scalp surface and their possible cortical sources.

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