Good Essay On Tempoparietal-Occipital Stimulation And The Perception Of Shadow Figures
A seizure is unchecked excitatory activity spreading through the brain. The intensity of the electrical activity and the area of the brain where a seizure is focused determines what effect it will have on body systems, sensations and perceptions, and outward physical behaviors. Because neurons fire without external stimulus, uncontrollable muscle movements occur as well as false sensory perceptions such as imagined sights, smells, and sounds. Seizure activity recorded the occipital lobe has been correlated to simple visual hallucinations, while seizure activity that involves the occipital lobe and temporal lobes has caused much more intense multisensory hallucinations involving bright colors, sounds, and emotional context (Elliott, Joyce, and Shorvon, 2009).
Almost all head movements that happen during a seizure occur on the same side of the body where the electrical activity originated in the brain. This is also true of eye movement and gaze so it is of note when a person who is experiencing a seizure fixes their gaze in the opposite direction. A 2002 case study describes a 30-year-old Dutch woman who had been experiencing intractable seizures for 15 years who was observed fixing her gaze to the opposite side of the seizure activity (Zijlmans, et al, 2009). Researchers observed and recorded the seizure activity in her temporal lobe with subdural electrodes; gamma activity was recorded over her medial temporal gyrus and then spread to her temporal lobe which corresponded with her contralateral gaze deviations. She was simultaneously videotaped. Later, researchers were able to reproduce the same seizure activity in the lab by electrically stimulating the same subdural electrode points. When the points at the junction of the temporal and occipital lobe were stimulated, the woman reported the strong sensation that there was a presence in the room. She described an irresistible urge to look to the right because she felt someone standing there, corresponding to the gaze deviations witnessed in her seizure activity. Afterword, she had been unable to recall the sensation of the shadow figure(Zijlmans, et al, 2009).
The temporal lobe has been the focus of a body of research connected to sensed presences and mystical experiences (Granqvist et al, 2005; Persinger, et al, 2000.) Transcranial magnetic stimulation over the temporal lobe was claimed by researchers led by Persinger to raise the average person's perception that they are in the presence of a sentient being by 80%. Persinger posited that electromagnetic forces further exacerbated structural weaknesses in the temporal lobes in certain people, causing them to perceive the presence of alien visitors, ghosts, and other supernatural entities (Persinger at all, 2000). However, following up on Persinger's work, Granqvist found that certain personal characteristics, specifically suggestibility, were more likely to determine the perception of supernatural entities than was stimulation by transcranial magnetic stimulation over the temporal lobe.
Clinicians inadvertently triggered the shadow person sensation in a woman as they were preparing her for epilepsy surgery. While stimulating different parts of her brain, Dr. Arzy observed that the patient became frightened and described the shadow person phenomenon when she stimulated the junction between the occipital parietal and temporal lobes (Arzy, et al. 2009). The continued frantic electrical activity of epilepsy can cause lesions in the brain; Structurally, researchers have noticed some of the same anatomical features in individuals with temporal lobe epilepsy – such as lesions that occur in the junction of occipital, parietal, and temporal lobes –also appear in individuals with schizophrenia, causing speculation about overactive pathways leading from the occipital lobe through the temporal lobe on the left hemisphere that may cause threatening hallucinations or sense of being watched (Elliott, Joyce, and Shorvon, 2009).
Arzy, S., Seeck, M., Ortigue, S., Spinelli, L., & Blanke, O. (2006). Induction of an illusory shadow person. Nature, 443(7109), 287-287.
Elliott, B., Joyce, E., & Shorvon, S. (2009). Delusions, illusions and hallucinations in epilepsy: 1. Elementary phenomena. Epilepsy research, 85(2), 162-171.
Granqvist, P., Fredrikson, M., Unge, P., Hagenfeldt, A., Valind, S., Larhammar, D., & Larsson, M. (2005). Sensed presence and mystical experiences are predicted by suggestibility, not by the application of transcranial weak complex magnetic fields. Neuroscience Letters, 379(1), 1-6.
Persinger, M. A., Tiller, S. G., & Koren, S. A. (2000). Experimental simulation of a haunt experience and elicitation of paroxysmal electroencephalographic activity by transcerebral complex magnetic fields: induction of a synthetic'ghost'?. Perceptual and Motor Skills, 90(2), 659-674.
Strong, T. K. (2010). Neuro plastic possibilities for expanded consciousness: A consideration of the effects on brain dynamics and consciousness of neurophysiological alterations attributed to temporal lobe epilepsy and post temporal lobectomy recovery (Doctoral dissertation, CALIFORNIA INSTITUTE OF INTEGRAL STUDIES).
Zijlmans, M., van Eijsden, P., Ferrier, C. H., Kho, K. H., van Rijen, P. C., & Leijten, F. S. S. (2009). Illusory shadow person causing paradoxical gaze deviations during temporal lobe seizures. Journal of Neurology, Neurosurgery & Psychiatry, 80(6), 686-688.