Event-related changes in neuromagnetic activity associated with syncopation and synchronization timing tasks.

For low rhythmic rates (1.0 to approximately 2.0 Hz), subjects are able to successfully coordinate finger flexion with an external metronome in either a syncopated (between the beats) or synchronized (on each beat) fashion. Beyond this rate, however, syncopation becomes unstable and subjects spontaneously switch to synchronization to maintain a 1:1 stimulus/response relationship. We used a whole-head magnetometer to investigate the spatiotemporal dynamics of neuromagnetic activity (MEG) associated with both coordinative patterns at eight different rates spanning the range 1.0-2.75 Hz. Timing changes in the event-related fields accompanied transitions from syncopation to synchronization and followed the placement of the motor response within each stimulus/response cycle. Decomposition of event-related fields into component auditory and motor brain responses revealed that the amplitude of the former decreased with increasing coordination rate whereas the motor contribution remained approximately constant across all rates. Such an interaction may contribute to changes in auditory-motor integration that cause syncopation to become unstable. Examination of event-related changes in high frequency bands revealed that MEG signal power in the beta band (15-30 Hz) was significantly lower during syncopated coordination in sensors covering the contralateral sensorimotor area suggesting a dependence of beta rhythm amplitude on task difficulty. Suppression of beta rhythms was also stronger during synchronization preceded by syncopation, e.g., after subjects had switched, when compared with a control condition in which subjects synchronized throughout the entire range of rates.

Neuromagnetic activity in alpha and beta bands reflect learning-induced increases in coordinative stability.

OBJECTIVE: To investigate how learning induced increases in stability on a syncopation task are manifest in the dynamics of cortical activity. METHOD: Magnetoencephalography was recorded from 143 sensors (CTF Systems, Inc). A pre-training procedure determined the critical frequency (F(c)) for each subject (n=4). Subjects either syncopated or synchronized to a metronome that increased in frequency from 1.2 to 3.0 Hz in 0.2 Hz steps. The F(c) was the point at which subjects spontaneously switched from syncopation to synchronization. Subjects then underwent 100 training trials (with feedback) at F(c). Following the learning phase the pre-training procedure was repeated. RESULTS: An increase in the F(c) occurred indicating that practice improved the stability of syncopation. The transition delay was also observed in the phase of the time-averaged signal in sensors over the contralateral sensorimotor area and in power analysis in the 8-12 Hz and 18-24 Hz frequency bands. Initially, reduced power was observed bilaterally during syncopation compared to synchronization. Following training, these differences were reduced or eliminated. CONCLUSION: Pre-training power differences can be explained by the greater difficulty of the syncopation task. The reduction in power differences following training suggests that at the cortical level, syncopation became more similar to synchronization possibly reflecting a decrease in task and/or attention demands.

Spatiotemporal analysis of neuromagnetic events underlying the emergence of coordinative instabilities.

A full-head 143-channel superconducting quantum interference device was used to study changes occurring in the magnetic activity of the human brain during performance of an auditory-motor coordination task in which the rate of coordination was systematically increased. Previous research using the same task paradigm demonstrated that spontaneous switches in timing behavior that arise with higher coordination rates are accompanied by qualitative changes in spatiotemporal brain activity measured by electro- and magnetoencephalography. Here we show how these patterns can be decomposed into basic physiological events, i.e., evoked brain responses to acoustic tones and self-initiated finger movements. The frequency dependence of the amplitudes of these component responses may shed new light onto why spontaneous timing transitions occur in the first place.

Spatiotemporal reorganization of electrical activity in the human brain associated with a timing transition in rhythmic auditory-motor coordination.

We used a 61-channel electrode array to investigate the spatiotemporal dynamics of electroencephalographic (EEG) activity related to behavioral transitions in rhythmic sensorimotor coordination. Subjects were instructed to maintain a 1:1 relationship between repeated right index finger flexion and a series of periodically delivered tones (metronome) in a syncopated (anti-phase) fashion. Systematic increases in stimulus presentation rate are known to induce a spontaneous switch in behavior from syncopation to synchronization (in-phase coordination). We show that this transition is accompanied by a large-scale reorganization of cortical activity manifested in the spatial distributions of EEG power at the coordination frequency. Significant decreases in power were observed at electrode locations over left central and anterior parietal areas, most likely reflecting reduced activation of left primary sensorimotor cortex. A second condition in which subjects were instructed to synchronize with the metronome controlled for the effects of movement frequency, since synchronization is known to remain stable across a wide range of frequencies. Different, smaller spatial differences were observed between topographic patterns associated with synchronization at low versus high stimulus rates. Our results demonstrate qualitative changes in the spatial dynamics of human brain electrical activity associated with a transition in the timing of sensorimotor coordination and suggest that maintenance of a more difficult anti-phase timing relation is associated with greater activation of primary sensorimotor areas.

In vitro fertilization and embryo transfer: two-year experience.

Between February 1983 and January 1985, 206 laparoscopies were performed on 172 women following controlled ovarian hyperstimulation with human menopausal gonadotropin (hMG) and human chorionic gonadotropin (hCG). Sixty-four clinical pregnancies advanced beyond the sixth week of gestation and were confirmed by ultrasound; and 37.2% of the patients conceived after in vitro fertilization and embryo transfer. The clinical pregnancy rate was 31.1% when based on the number of laparoscopies performed and 33.9% when based on the number of embryo transfers. There were 12 multiple pregnancies (18.8%), 11 miscarriages (17.2%), and one ectopic (tubal) pregnancy (1.6%). The most important factors contributing toward the success of this program were the establishment of specific criteria for patient selection, rigid adherence to clinical and laboratory protocols, and the maintenance of strict quality control.

The development of a successful non-university-based ambulatory in vitro fertilization/embryo transfer program: phase I.

Most of the current in vitro fertilization and embryo transfer (IVF-ET) programs are university-based. The establishment of a successful ambulatory IVF program in association with a busy, two-man general obstetrics-gynecologic practice is described. Seventy-one infertile couples were screened between February 1 and October 15, 1983. Forty-three couples were judged eligible for IVF-ET. Forty-three women underwent a single attempt at ET. The first 13 of these women underwent controlled ovarian hyperstimulation (COH) with 150 mg clomiphene citrate and human chorionic gonadotropin (hCG), and the remaining 30 underwent COH with human menopausal gonadotropin (hMG) and hCG. One of the 13 patients who underwent COH with clomiphene citrate conceived but subsequently miscarried early in the first trimester, for an 8% pregnancy rate. There were 12 pregnancies among the 30 patients who received hMG and hCG, for a 40% pregnancy rate. Only three of these pregnancies miscarried in the early first trimester, and three of the nine viable pregnancies are twin gestations. The possible factors responsible for the high pregnancy rate with IVF-ET, using COH with hMG and hCG, are discussed, and the feasibility of its performance in a well-controlled, non-university program is demonstrated.