Glossary Terms  Home

T

Talairach Space

The most commonly used space for normalization of fMRI data.

Task Frequency

The rate of presentation of a periodic experimental task.

Temporal Interpolation

The estimation of the value of a signal at a time point that was not originally collected, using data from nearby time points.

Time Domain

The expression of a signal in terms of its intensity at different points in time.

Torsion

A rotation (twisting) of an object. Even if the motion of objects is restricted so that they cannot translate, a strong magnetic field will still exert a torque that may cause them to rotate so that they become aligned with the magnetic field.

Translation

The movement of an object along an axis in space (in the absence of rotation).

Transmitter Coil

An electromagnetic coil that generates an oscillating magnetic field at the resonant frequency of atomic nuclei within a sample.

Transverse

Perpendicular to the magnetic field, or z-direction, of the scanner (into the bore).

Transverse Relaxation

The loss of net magnetization within the transverse plane due to the loss of phase coherence of spins.

Torque

A force that induces rotational motion.

Type I error

Rejecting the null hypothesis when it is in fact true.  Also known as a false positive.

Type II error

Accepting th enull hypothesis when it is in fact false.  Also known as an incorrect rejection or false negative. 

T1 (recovery)

The time constant that describes the recovery of the longitudinal component of net magnetization over time.

T2 (decay)

The time constant that describes the decay of the transverse component of net magnetization due to accumulated phase differences caused by spin-spin interactions.

T2* (decay)

The time constant that describes the transverse component of net magnetization due to both accumulated phase differences and local magnetic field inhomogeneities. T2* is always shorter than T2. BOLD-contrast fMRI relies on T2* contrast.