What characteristic is generally associated with abnormal EEG activity in clinical settings?

The presence of epileptiform discharges is a key characteristic associated with abnormal EEG activity in clinical settings. These discharges are specifically linked to seizure activity and can manifest as spikes, sharp waves, or spike-and-wave complexes. They indicate the existence of underlying neurological conditions, such as epilepsy or other forms of cortical irritation or dysfunction. In many cases, their identification on an EEG helps in the diagnosis and management of epileptic syndromes and other relevant disorders.

Other options, while relevant in EEG interpretation, do not directly signify abnormal activity in the same way. For instance, synchronous rhythms (normal rhythmic activity) and stable baselines suggest healthy brain function, whereas asynchronous rhythms often occur without pathology but can also be present in normal variations of brain activity.