Repetitive transcranial magnetic stimulation interrupts phase synchronization during rhythmic motor entrainment.

Rhythmic stimuli delivered through the auditory system can facilitate improved motor control following a motor impairment. The synchronization of movement to rhythmic auditory cues is characterized by quick, stable coupling of motor responses to rhythmic auditory cues. The exact neural sites responsible for this transformation of auditory input into timed rhythmic motor output are not clear. Neuroimaging studies have identified left ventral premotor cortex (vPMC) and left superior temporal-parietal (STP) activation during rhythmic auditory-motor synchronization. To investigate brain areas necessary for different types of rhythmic auditory-motor synchronization, we delivered repetitive transcranial magnetic stimulation (rTMS) to 15 healthy individuals prior to a rhythmic-auditory tapping task. Subthreshold rTMS was administered separately to the left vPMC and STP at a frequency of 0.9Hz for 15 min. Phase synchronization error (difference between auditory stimulus and response onsets) significantly increased after rTMS to STP as compared to baseline. Synchronization error also increased after rTMS to vPMC as compared to baseline, but not significantly. Absolute period error, (absolute difference between metronome interval and response interval) was not affected by rTMS. The significant effect of rTMS at the STP expands upon previous imaging research, suggesting that this area is part of the network responsible for rhythmic auditory-motor synchronization. The effect of rTMS on phase synchronization, but not period synchronization suggests these are separate neural processes controlled by different neural networks.

Time, story, and wisdom: emerging themes in narrative gerontology.

Narrative approaches in the field of aging are receiving increasing attention by theorists and practitioners alike. This article draws on recent thinking in narrative gerontology to look at three aspects of aging on which a narrative perspective can shed further light. In relation to the temporal aspects, the notion of storytime is examined. Concerning its poetical aspects, the article considers the stages, styles, genres, contexts, and selves of self-storying. Under spiritual aspects, the topics of meaning and identity are explored. A discussion of these aspects may be seen to converge on the theme of wisdom and the possibility of wisdom environments.

Rapid motor adaptations to subliminal frequency shifts during syncopated rhythmic sensorimotor synchronization.

The synchronization of rhythmic arm movements to a syncopated metronome cue was studied in a step-change design whereby small tempo shifts were inserted at fixed time points into the metronome frequency. The cueing sequence involved three stimulus types: (1) target contact in synchrony with the metronome beats, (2) syncopated target contact midway in time between audible beats, and (3) syncopated target contact following either a +2% or -2% change in stimulus frequency. Analysis of normalized and aggregated data revealed that (1) during the syncopation condition the response period showed a rapid adaptation to the frequency-incremented stimulus period, (2) response period was less variable during syncopated movement, (3) mean synchronization error and variability, calculated during syncopation relative to the mathematical midpoint of the stimulus cycle, were reduced during syncopated movements, and (4) synchronization error following the frequency increment showed trends to return linearly to pre-increment values which was fully achieved in the -2% change condition only. The results suggest that frequency entrainment to stimulus period was possible during syncopated movement with the response and stimulus onsets 180 degrees out of phase. Most remarkably, 70-80% of the adaptation of the response period to the new stimulus period was immediately attained during the second half cycle of the syncopated movement. Finally, a mathematical model, based on recursion, was introduced that accurately modeled actual data as a function of the previous stimulus and response intervals and a weighted response of period error and synchronization error, which showed dominance of frequency entrainment over phase entrainment during rhythmic synchronization.