I was interested in learning more about amnesia, so I found this article about a specific type of amnesia called Transient Global Amnesia, or TGA. TGA is an acute amnesia that does not last longer than 24 hours. The person may have both anterograde (cannot create new memories) and retrograde (cannot remember past) amnesia; however, they still retain alertness, attention, identity, and implicit procedural memories. TGA has been linked with a failure of certain areas that store and retrieve episodic memories, such as the temporal structures but not at the posterior cingulate cortex. The researchers of this case study wanted "to investigate the cognitive and neuro-functional correlates of TGA in the acute phase and at subsequent follow-ups after one month and one year, to investigate whether there were any long-term sequels at the neuro-functional level following the attack." Researchers used SPECT (single-photon emission computed tomography) for brain imaging and neurological assessments on participants.
The participants were the case study, a 55 year old educated, female teacher, who suffered a severe headache and amnesia. She could not recognize her daughter’s voice on the phone, could not remember who was the current prime minister, nor current events that had taken place in her life. However, she had retained normal retrieval functioning of short-term and semantic memory. She received several brain scans and a brain perfusion test, using SPECT. A perfusion test measures the amount of blood flowing through certain cerebral areas of the brain. Scans revealed she had less blood in the bilateral inferior temporal regions and right superior and posterior parietal areas. The next day her memory was restored and she could not remember the events of the previous day.
Researchers asked this participant and then six more healthy participants (control group) to participate in their study. All participants underwent SPECT analysis. Her results were compared with different control results right after the acute attack, one month after the attack, and one year after the attack. A within-subjects analysis of the SPECT results concludes there was more blood in the hippocampus, medial temporal lobe and frontal cortex bilaterally after one month as compared to her scan right after the acute attack. A year later there was more blood in the right hippocampus as compared to the acute scan; also, there was more blood in the right hippocampus and frontal cortex when compared to the one month scan.
When the patient is compared to the healthy individuals at the three different times the scans show a lack of blood flow to the brain areas in the right hemisphere, cingulated, and gyri. However, after one year there were not significant differences between the patient and the controls. The increases and decreases of brain perfusion tell the researchers what brain regions are allowing her to retain some cognitive functions and memories and which regions are producing deficits resulting in acute amnesia. As stated, the researchers discovered no lasting effects of TGA after one year. In conclusion, TGA “appears to be a benign syndrome resulting from transient dysfunction of structures supporting memory encoding and retrieval processes such as the hippocampus (bilaterally), the right prefrontal and cingulated cortex.”
This article was consistent with what we learned in class: the hippocampus is highly involved in the process of storing and retrieving memory; and any deficit or dysfunction of this area can cause acute to chronic amnesia.
Caffarra, P., Concari, L., Gardini, S., Spaggiar, S., Dieci, F., Copelli, S.,. . . Venneri, A. (2009) Recovery from transient global amnesia following restoration of hippocampal and fronto-cingulate perfusion. Behavioral Neurology, 22, 131-139. doi: 10.3233/BEN-2009-0253
No comments:
Post a Comment