Behavioural and neurophysiological data from experiments on the impact of spatial frequency information to action comprehension

Understanding object-directed actions performed by others is central to
everyday life. This ability is thought to rely on the interaction between
the dorsal action observation network (AON) and a ventral object
recognition pathway. On this view, the AON would encode action kinematics,
and the ventral pathway, the most likely intention afforded by the
objects. However, experimental evidence supporting this model is still
scarce. Here, we aimed to disentangle the contribution of dorsal vs.
ventral pathways to action comprehension by exploiting their differential
tuning to lowspatial frequencies (LSFs) and high-spatial frequencies
(HSFs). We filtered naturalistic action images to contain only LSF or HSF
and measured behavioral performance and corticospinal excitability (CSE)
using transcranial magnetic stimulation (TMS). Actions were embedded in
congruent or incongruent scenarios as defined by the compatibility between
grips and intentions afforded by the contextual objects. Behaviorally,
participants were better at discriminating congruent actions in intact
than LSF images. This effect was reversed for incongruent actions, with
better performance for LSF than intact and HSF. These modulations were
mirrored at the neurophysiological level, with greater CSE facilitation
for congruent than incongruent actions for HSF and the opposite pattern
for LSF images. Finally, only for LSF did we observe CSE modulations
according to grip kinematics. While results point to differential dorsal
(LSF) and ventral (HSF) contributions to action comprehension for grip and
context encoding, respectively, the negative congruency effect for LSF
images suggests that object processing may influence action perception not
only through ventral-to-dorsal connections, but also through a
dorsal-to-dorsal route involved in predictive processing.