As the dead region will be less detectable due to the upward spread of excitation.

For example, a sloping audiogram is often present with someone with a dead region, due to the spread of excitation.

This pattern of the spread of excitation is similar to the 'upward spread of masking' phenomenon.

This means that the threshold of the responding area is sufficiently raised, so that it cannot detect the spread of excitation from the tone.

Because of the arrangement of sensory regions in the thalamus, there may be a spread of excitation in this brain region.

Although it is likely that the slope represents the less pronounced downward spread of excitation, rather than accurate thresholds for those frequencies with non-functioning hair cells.

If the basilar membrane vibration is large enough, neurons tuned to different characteristic frequencies such as those adjacent to the dead region, will be stimulated due to the spread of excitation.

The hippocampus, which contains a large volume of just such glutamatergic neurons (and NMDA receptors, which are permeable to Ca entry after binding of both glutamate and glycine), is especially vulnerable to epileptic seizure, subsequent spread of excitation, and possible neuronal death.

In the case of dead regions, when the test signal lies within the boundaries of a dead region, the tip of the PTC will be shifted to the edge of the dead region, to the area that is still functioning and detecting the spread of excitation from the signal.