P W Fink, P Foo, V K Jirsa, and J A Kelso (2000)
Local and global stabilization of coordination by sensory information
EXPERIMENTAL BRAIN RESEARCH 134(1):9–20.
In studies of rhythmic coordination, where sensory information is
often generated by an auditory stimulus, spatial and temporal variability
are known to decrease at points in the movement cycle coincident
with the stimulus, a phenomenon known as anchoring (Byblow et al.
1994). Here we hypothesize that the role of anchoring may be to
globally stabilize coordination under conditions in which it would
otherwise undergo a global coordinative change such as a phase transition.
To test this hypothesis, anchoring was studied in a bimanual coordination
paradigm in which either inphase or antiphase coordination was produced
as auditory pacing stimuli land hence movement frequency) were scaled
over a wide range of frequencies. Two different anchoring conditions
were used: a single-metronome condition, in which peak amplitude
of right finger flexion coincided with the auditory stimulus; and
a double-metronome condition, in which each finger reversal (flexion
and extension) occurred simultaneously with the auditory stimuli.
Anchored reversal points displayed lower spatial variation than
unanchored reversal points, resulting in more symmetric phase plane
trajectories in the double- than the single-metronome condition.
The global coordination dynamics of the double-metronome condition
was also more stable, with transitions from antiphase to inphase
occurring less often and at higher movement frequencies than in
the single-metronome condition. An extension of the Haken-Kelso-Bunz
model of bimanual coordination is presented briefly which includes
specific coupling of sensory information to movement through a process
we call parametric stabilization. The parametric stabilization model
provides a theoretical account of both local effects on the individual
movement trajectories (anchoring) and global stabilization of observed
coordination patterns, including the delay of phase transitions.,