  In this work, we study the outward propagation of temperature perturbations.
For this purpose, we apply an advanced analysis technique, the Transfer
Entropy, to ECE measurements performed in ECR heated discharges at the
low-shear stellarator TJ-II. We observe that the propagation of these
perturbations is not smooth, but is slowed down at specific radial positions,
near 'trapping zones' characterized by long time lags with respect to the
perturbation origin. We also detect instances of rapid or instantaneous
(non-local) propagation, in which perturbations appear to 'jump over' specific
radial regions.
  The analysis of perturbations introduced in a resistive Magneto-Hydrodynamic
model of the plasma leads to similar results. The radial regions corresponding
to slow radial transport are identified with maxima of the flow shear
associated with rational surfaces (mini-transport barriers). The non-local
interactions are ascribed to MHD mode coupling effects.
