# -*- coding: utf-8 -*-
"""'Current Source Density analysis (CSD) is a class of methods of analysis of
extracellular electric potentials recorded at multiple sites leading to
estimates of current sources generating the measured potentials. It is usually
applied to low-frequency part of the potential (called the Local Field
Potential, LFP) and to simultaneous recordings or to recordings taken with
fixed time reference to the onset of specific stimulus (Evoked Potentials)'
(Definition by Prof.Daniel K. Wójcik for Encyclopedia of Computational
Neuroscience)
CSD is also called as Source Localization or Source Imaging in the EEG circles.
Here are CSD methods for different types of electrode configurations.
1D - laminar probe like electrodes.
2D - Microelectrode Array like
3D - UtahArray or multiple laminar probes.
The following methods have been implemented so far
1D - StandardCSD, DeltaiCSD, SplineiCSD, StepiCSD, KCSD1D
2D - KCSD2D, MoIKCSD (Saline layer on top of slice)
3D - KCSD3D
Each of these methods listed have some advantages. The KCSD methods for
instance can handle broken or irregular electrode configurations electrode
Keywords: LFP; CSD; Multielectrode; Laminar electrode; Barrel cortex
Citation Policy: See ./current_source_density_src/README.md
Contributors to this current source density estimation module are:
Chaitanya Chintaluri(CC), Espen Hagen(EH) and Michał Czerwinski(MC).
EH implemented the iCSD methods and StandardCSD
CC implemented the kCSD methods, kCSD1D(MC and CC)
CC and EH developed the interface to elephant.
"""
from __future__ import division
import neo
import quantities as pq
import numpy as np
from scipy import io
from scipy.integrate import simps
from elephant.current_source_density_src import KCSD
from elephant.current_source_density_src import icsd
import elephant.current_source_density_src.utility_functions as utils
utils.patch_quantities()
available_1d = ['StandardCSD', 'DeltaiCSD', 'StepiCSD', 'SplineiCSD', 'KCSD1D']
available_2d = ['KCSD2D', 'MoIKCSD']
available_3d = ['KCSD3D']
kernel_methods = ['KCSD1D', 'KCSD2D', 'KCSD3D', 'MoIKCSD']
icsd_methods = ['DeltaiCSD', 'StepiCSD', 'SplineiCSD']
py_iCSD_toolbox = ['StandardCSD'] + icsd_methods
[docs]def estimate_csd(lfp, coords=None, method=None,
process_estimate=True, **kwargs):
"""
Fuction call to compute the current source density (CSD) from extracellular
potential recordings(local-field potentials - LFP) using laminar electrodes
or multi-contact electrodes with 2D or 3D geometries.
Parameters
----------
lfp : neo.AnalogSignal
positions of electrodes can be added as neo.RecordingChannel
coordinate or sent externally as a func argument (See coords)
coords : [Optional] corresponding spatial coordinates of the electrodes
Defaults to None
Otherwise looks for RecordingChannels coordinate
method : string
Pick a method corresonding to the setup, in this implementation
For Laminar probe style (1D), use 'KCSD1D' or 'StandardCSD',
or 'DeltaiCSD' or 'StepiCSD' or 'SplineiCSD'
For MEA probe style (2D), use 'KCSD2D', or 'MoIKCSD'
For array of laminar probes (3D), use 'KCSD3D'
Defaults to None
process_estimate : bool
In the py_iCSD_toolbox this corresponds to the filter_csd -
the parameters are passed as kwargs here ie., f_type and f_order
In the kcsd methods this corresponds to cross_validate -
the parameters are passed as kwargs here ie., lambdas and Rs
Defaults to True
kwargs : parameters to each method
The parameters corresponding to the method chosen
See the documentation of the individual method
Default is {} - picks the best parameters,
Returns
-------
Estimated CSD
neo.AnalogSignal object
annotated with the spatial coordinates
Raises
------
AttributeError
No units specified for electrode spatial coordinates
ValueError
Invalid function arguments, wrong method name, or
mismatching coordinates
TypeError
Invalid cv_param argument passed
"""
if not isinstance(lfp, neo.AnalogSignal):
raise TypeError('Parameter `lfp` must be a neo.AnalogSignal object')
if coords is None:
coords = lfp.channel_index.coordinates
else:
scaled_coords = []
for coord in coords:
try:
scaled_coords.append(coord.rescale(pq.mm))
except AttributeError:
raise AttributeError('No units given for electrode spatial \
coordinates')
coords = scaled_coords
if method is None:
raise ValueError('Must specify a method of CSD implementation')
if len(coords) != lfp.shape[1]:
raise ValueError('Number of signals and coords is not same')
for ii in coords: # CHECK for Dimensionality of electrodes
if len(ii) > 3:
raise ValueError('Invalid number of coordinate positions')
dim = len(coords[0]) # TODO : Generic co-ordinates!
if dim == 1 and (method not in available_1d):
raise ValueError('Invalid method, Available options are:',
available_1d)
if dim == 2 and (method not in available_2d):
raise ValueError('Invalid method, Available options are:',
available_2d)
if dim == 3 and (method not in available_3d):
raise ValueError('Invalid method, Available options are:',
available_3d)
if method in kernel_methods:
input_array = np.zeros((len(lfp), lfp[0].magnitude.shape[0]))
for ii, jj in enumerate(lfp):
input_array[ii, :] = jj.rescale(pq.mV).magnitude
kernel_method = getattr(KCSD, method) # fetch the class 'KCSD1D'
lambdas = kwargs.pop('lambdas', None)
Rs = kwargs.pop('Rs', None)
k = kernel_method(np.array(coords), input_array.T, **kwargs)
if process_estimate:
k.cross_validate(lambdas, Rs)
estm_csd = k.values()
estm_csd = np.rollaxis(estm_csd, -1, 0)
output = neo.AnalogSignal(estm_csd * pq.uA / pq.mm**3,
t_start=lfp.t_start,
sampling_rate=lfp.sampling_rate)
if dim == 1:
output.annotate(x_coords=k.estm_x)
elif dim == 2:
output.annotate(x_coords=k.estm_x, y_coords=k.estm_y)
elif dim == 3:
output.annotate(x_coords=k.estm_x, y_coords=k.estm_y,
z_coords=k.estm_z)
elif method in py_iCSD_toolbox:
coords = np.array(coords) * coords[0].units
if method in icsd_methods:
try:
coords = coords.rescale(kwargs['diam'].units)
except KeyError: # Then why specify as a default in icsd?
# All iCSD methods explicitly assume a source
# diameter in contrast to the stdCSD that
# implicitly assume infinite source radius
raise ValueError("Parameter diam must be specified for iCSD \
methods: {}".format(", ".join(icsd_methods)))
if 'f_type' in kwargs:
if (kwargs['f_type'] is not 'identity') and \
(kwargs['f_order'] is None):
raise ValueError("The order of {} filter must be \
specified".format(kwargs['f_type']))
lfp = neo.AnalogSignal(np.asarray(lfp).T, units=lfp.units,
sampling_rate=lfp.sampling_rate)
csd_method = getattr(icsd, method) # fetch class from icsd.py file
csd_estimator = csd_method(lfp=lfp.magnitude * lfp.units,
coord_electrode=coords.flatten(),
**kwargs)
csd_pqarr = csd_estimator.get_csd()
if process_estimate:
csd_pqarr_filtered = csd_estimator.filter_csd(csd_pqarr)
output = neo.AnalogSignal(csd_pqarr_filtered.T,
t_start=lfp.t_start,
sampling_rate=lfp.sampling_rate)
else:
output = neo.AnalogSignal(csd_pqarr.T, t_start=lfp.t_start,
sampling_rate=lfp.sampling_rate)
output.annotate(x_coords=coords)
return output
[docs]def generate_lfp(csd_profile, ele_xx, ele_yy=None, ele_zz=None,
xlims=[0., 1.], ylims=[0., 1.], zlims=[0., 1.], res=50):
"""Forward modelling for the getting the potentials for testing CSD
Parameters
----------
csd_profile : fuction that computes True CSD profile
Available options are (see ./csd/utility_functions.py)
1D : gauss_1d_dipole
2D : large_source_2D and small_source_2D
3D : gauss_3d_dipole
ele_xx : np.array
Positions of the x coordinates of the electrodes
ele_yy : np.array
Positions of the y coordinates of the electrodes
Defaults ot None, use in 2D or 3D cases only
ele_zz : np.array
Positions of the z coordinates of the electrodes
Defaults ot None, use in 3D case only
x_lims : [start, end]
The starting spatial coordinate and the ending for integration
Defaults to [0.,1.]
y_lims : [start, end]
The starting spatial coordinate and the ending for integration
Defaults to [0.,1.], use only in 2D and 3D case
z_lims : [start, end]
The starting spatial coordinate and the ending for integration
Defaults to [0.,1.], use only in 3D case
res : int
The resolution of the integration
Defaults to 50
Returns
-------
LFP : neo.AnalogSignal object
The potentials created by the csd profile at the electrode positions
The electrode postions are attached as RecordingChannel's coordinate
"""
def integrate_1D(x0, csd_x, csd, h):
m = np.sqrt((csd_x - x0)**2 + h**2) - abs(csd_x - x0)
y = csd * m
I = simps(y, csd_x)
return I
def integrate_2D(x, y, xlin, ylin, csd, h, X, Y):
Ny = ylin.shape[0]
m = np.sqrt((x - X)**2 + (y - Y)**2)
m[m < 0.0000001] = 0.0000001
y = np.arcsinh(2 * h / m) * csd
I = np.zeros(Ny)
for i in range(Ny):
I[i] = simps(y[:, i], ylin)
F = simps(I, xlin)
return F
def integrate_3D(x, y, z, xlim, ylim, zlim, csd, xlin, ylin, zlin,
X, Y, Z):
Nz = zlin.shape[0]
Ny = ylin.shape[0]
m = np.sqrt((x - X)**2 + (y - Y)**2 + (z - Z)**2)
m[m < 0.0000001] = 0.0000001
z = csd / m
Iy = np.zeros(Ny)
for j in range(Ny):
Iz = np.zeros(Nz)
for i in range(Nz):
Iz[i] = simps(z[:, j, i], zlin)
Iy[j] = simps(Iz, ylin)
F = simps(Iy, xlin)
return F
dim = 1
if ele_zz is not None:
dim = 3
elif ele_yy is not None:
dim = 2
x = np.linspace(xlims[0], xlims[1], res)
if dim >= 2:
y = np.linspace(ylims[0], ylims[1], res)
if dim == 3:
z = np.linspace(zlims[0], zlims[1], res)
sigma = 1.0
h = 50.
pots = np.zeros(len(ele_xx))
if dim == 1:
chrg_x = np.linspace(xlims[0], xlims[1], res)
csd = csd_profile(chrg_x)
for ii in range(len(ele_xx)):
pots[ii] = integrate_1D(ele_xx[ii], chrg_x, csd, h)
pots /= 2. * sigma # eq.: 26 from Potworowski et al
ele_pos = ele_xx
elif dim == 2:
chrg_x, chrg_y = np.mgrid[xlims[0]:xlims[1]:np.complex(0, res),
ylims[0]:ylims[1]:np.complex(0, res)]
csd = csd_profile(chrg_x, chrg_y)
for ii in range(len(ele_xx)):
pots[ii] = integrate_2D(ele_xx[ii], ele_yy[ii],
x, y, csd, h, chrg_x, chrg_y)
pots /= 2 * np.pi * sigma
ele_pos = np.vstack((ele_xx, ele_yy)).T
elif dim == 3:
chrg_x, chrg_y, chrg_z = np.mgrid[xlims[0]:xlims[1]:np.complex(0, res),
ylims[0]:ylims[1]:np.complex(0, res),
zlims[0]:zlims[1]:np.complex(0, res)]
csd = csd_profile(chrg_x, chrg_y, chrg_z)
xlin = chrg_x[:, 0, 0]
ylin = chrg_y[0, :, 0]
zlin = chrg_z[0, 0, :]
for ii in range(len(ele_xx)):
pots[ii] = integrate_3D(ele_xx[ii], ele_yy[ii], ele_zz[ii],
xlims, ylims, zlims, csd,
xlin, ylin, zlin,
chrg_x, chrg_y, chrg_z)
pots /= 4 * np.pi * sigma
ele_pos = np.vstack((ele_xx, ele_yy, ele_zz)).T
pots = np.reshape(pots, (-1, 1)) * pq.mV
ele_pos = ele_pos * pq.mm
lfp = []
ch = neo.ChannelIndex(index=range(len(pots)))
for ii in range(len(pots)):
lfp.append(pots[ii])
asig = neo.AnalogSignal(np.array(lfp).T, sampling_rate=pq.kHz, units='mV')
ch.coordinates = ele_pos
ch.analogsignals.append(asig)
ch.create_relationship()
return asig
