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# Bug 833 - minimumnormestimate should work with lambda in an interpretable range

Status | CLOSED FIXED |

Reported | 2011-07-19 14:48:00 +0200 |

Modified | 2012-03-21 15:42:55 +0100 |

Product: | FieldTrip |

Component: | inverse |

Version: | unspecified |

Hardware: | All |

Operating System: | All |

Importance: | P1 enhancement |

Assigned to: | Jan-Mathijs Schoffelen |

URL: | |

Tags: | |

Depends on: | |

Blocks: | |

See also: |

## Jan-Mathijs Schoffelen - 2011-07-19 14:48:27 +0200

-Right now, the influence of the lambda is determined by the magnitude of the noise covariance matrix, and the magnitude of the gram-matrix (including the source priors). -Check how this is done in the MNE-suite Implement something similar

## Jan-Mathijs Schoffelen - 2012-02-06 16:48:27 +0100

MNE-suite allows for the spatial filter to be computed based on prewhitened leadfields, where the leadfields are prewhitened with an estimate of C^-1/2 where C is the noise covariance estimate. In a next step, the source covariance estimate is tailored such that the trace of the A*R*A' matrix is the same as the trace of I, where A is the prewhitened leadfield matrix and R the source covariance matrix. As a consequence of the prewhitening, the lambda parameter can take 'normal' values. According to the documentation can be taken as ~ 1/SNR I implement this in minimumnormestimate as: cfg.mne.prewhiten = 'yes';

## Jan-Mathijs Schoffelen - 2012-02-07 16:17:13 +0100

.