Consciousness during a seizure is a complicated subject. Some neurologists choose to define or diagnose seizures while skirting around the issue. Luckily for us, a group of neuroscientists got together and, using data collected from EEGs and fMRIs, explained the intricacies of consciousness during two of the most well-known types of seizures.
Absence SeizureAn absense seizure is typically characterized by a short period of staring and a “reduction of awareness and responsiveness” (Seri 44). The person may also blink rapidly and make small jerking motions with the arms or head. During an absense seizure, researchers have found results vary among their patients regarding brain activity. Also, patients with absense seizures report a spectrum of consciousness-related issues, which may be related to the short (5-30 seconds) duration of these seizures.
Even so, the researchers decided that the loss or alteration of consciousness could be caused by the “involvement of discrete brain regions” (Seri 44).
- So, parts of the brain that would not normally be used at the same time, together, suddenly become used–all at once. This causes a malfunction in the DMN (default mode network). The DMN is a term for the processes of our brain that run, all of the time, without us having to ask. This is why we breathe, for example. If brain gets cluttered with too many processes, it seems, according to this research, that our DMN has to flick off a few switches, resulting in a loss of consciousness. This explains why some absense seizure patients suffer a total loss of consciousness, while others only have a mild interruption. Others enter “zombie brain” and the DMN fires in a pattern, causing the patient to perform a repetitive action, such as rapid blinking (Seri 44).
Generalized Tonic-Clonic SeizureGeneralized tonic-clonic seizures characteristically blend a loss of consciousness with the immediate onset of the physical (able to be witnessed) symptoms. These seizures vary between patients in terms of length, loss of bladder control, vocalizations, and other secondary symptoms. They always begin with a stiffening of the body for a brief period of time (tonic phase), and are always followed by repeated quick contractions of muscle groups (clonic phase), resulting in jerking motions (Seri 44) During the tonic phase, brain electricity increases quickly and steadily, until the end of the tonic phase, where it becomes intermittent. This results “in a reduction in temporal and spatial complexity of the brain electrical signal, necessary for maintaining consciousness. During the clonic phase, bursts of 10 Hz rhythms become separated by intervals of inactive tracing or by slow waves. The bursts are synchronous with the jerks” (Seri 45). Blood-flow studies show that the entire brain may be working, all at once, during a generalized tonic-clonic seizure (Seri 45).
- So, it seems here that the brain is again working against itself when a seizure occurs. It floods itself with electricity until the messages are all static, just noise where the messages once were, and the person loses consciousness. Then, the static slows, allowing the body to relax during the intervals but gripping it awake with every surge.