A frontoparietal network for spatial attention reorienting in the auditory domain: a human fMRI/MEG study of functional and temporal dynamics.

Several studies have identified a supramodal network critical to the reorienting of attention toward stimuli at novel locations and which involves the right temporoparietal junction and the inferior frontal areas. The present functional magnetic resonance imaging (fMRI)\magnetoencephalography (MEG) study investigates: 1) the cerebral circuit underlying attentional reorienting to spatially varying sound locations; 2) the circuit related to the regular change of sound location in the same hemifield, the change of sound location across hemifields, or sounds presented randomly at different locations on the azimuth plane; 3) functional temporal dynamics of the observed cortical areas exploiting the complementary characteristics of the fMRI and MEG paradigms. fMRI results suggest 3 distinct roles: the supratemporal plane appears modulated by variations of sound location; the inferior parietal lobule is modulated by the cross-meridian effect; and the inferior frontal cortex is engaged by the inhibition of a motor response. MEG data help to elucidate the temporal dynamics of this network by providing high-resolution time series with which to measure latency of neural activation manipulated by the reorienting of attention.

Measurement of the longitudinal relaxation time by continuous-wave, nonlinear electron spin resonance spectroscopies

We characterize a continuous-wave, nonlinear electron spin resonance spectroscopy which detects the longitudinal component of the magnetization. It is demonstrated that the signal is proportional to the Laplace transform of a relaxation function with decay time equal to the longitudinal relaxation time T1. The conclusion is reached by comparing T1 to the effective time T(eff)1 being drawn by progressive saturation for a nitroxide radical dissolved in supercooled o-terphenyl. Copyright 1998 Academic Press.