Which condition might result in the observation of abnormal readings when normal waveforms are absent?

The observation of abnormal readings when normal waveforms are absent can be associated with seizure activity. During a seizure, the brain exhibits synchronized, excessive neuronal discharge, which can lead to distinct changes in the electrical activity measured by electroencephalography (EEG). This can result in abnormal readings such as spikes, sharp waves, or other atypical patterns, even if the typical voltage waveforms that represent normal brain activity are not present.

In contrast, other conditions may not lead to the same significant changes in brain electrical activity. Resting states generally do not produce abnormal readings, as a resting brain typically shows a baseline level of activity that doesn't exhibit the highly synchronized discharges seen in seizures. Normal cognitive processing and memory recall are also associated with specific activation patterns that do not equate to abnormal readings; instead, the brain functions within a typical range during these processes. Therefore, seizure activity is the condition that best aligns with the presence of abnormal readings amidst the absence of normal waveforms.