"""
To eliminate averaging of positive and negative voltages of polyphasic signals, all MEP voltages were converted to absolute values and integrated for measures of power (area under the curve). [...] Peak-to-peak amplitude, motor threshold (MT) and integrated amplitude were computed automatically in the 5–30 msec time window, as our pilot data indicated a 4 msec maximal duration of TMS artifact, and approximately 25 msec maximal latency to onset of the MEP in rats
"""
import numpy as np
from numpy import ndarray
from typing import Tuple
from math import ceil
[docs]def rotenberg(
trace: ndarray,
tms_sampleidx: int,
mep_window_in_ms: Tuple[float, float] = (5, 30),
fs: float = 1000,
) -> float:
"""Estimate the area of an iMEP based on Rotenberg 2010
Returns the iMEP Area of the rectified EMG integrated for the search window
.. warning::
This study was conducted on rats, and therefore the default search window from 5 to 30ms is probably too fast in humans. We therefore implemented the mep_window_in_ms as an argument. Consider adapting it when conducting studies with humans, e.g. to 15 to 50ms.
args
----
trace:ndarray
the one-dimensional (samples,) EMG signal with units of µV
tms_sampleidx: int
the sample at which the TMS pulse was applied
fs:float
the sampling rate of the signal
mep_window_in_ms: Tuple[float, float]
the search window after TMS to look for an iMEP.
returns
-------
amplitude:float
the iMEP area
.. admonition:: Reference
Rotenberg, A.; Muller, P. A.; Vahabzadeh-Hagh, A. M.; Navarro, X.; López-Vales, R.; Pascual-Leone, A. & Jensen, F. Lateralization of forelimb motor evoked potentials by transcranial magnetic stimulation in rats Clinical Neurophysiology, Elsevier BV, 2010, 121, 104-108
"""
a = tms_sampleidx + ceil(mep_window_in_ms[0] * fs / 1000)
# b should not be higher then the len of the trace
b = ceil(
min((tms_sampleidx + (mep_window_in_ms[1] * fs / 1000)), len(trace))
)
amp = np.sum(np.abs(trace[a:b]))
return amp