TLE

Visual Learning Deficits in TLE

     Many patients who have temporal lobe epilepsy experience visual deficits in which different aspects of their vision and perception are impaired. In the next few sections different tests will be discussed that assess visual impairment that occurs during temporal lobe epilepsy.

Rey Complex Figure Test

     Patients that have temporal lobe epilepsy have different affected abilities. The part of the temporal lobe that triggers a visual deficit is not dependant upon location. In a study by Anna R. Giovagnoli and Giuliano Avanzini (1999), a group of patients with left temporal lobe epilepsy and a group with right temporal epilepsy were tested with visual memory tests and verbal memory tests. One visual test that the scientists used was the Rey Complex Figure Test (Giovagnoli et al.,1999). This test involves the patient copying a nonsense picture consisting of 18 items and the reproducing it one hour later. The patient is scored on a scale of correctness. The patients with right and left temporal lobe epilepsy had more impaired functioning as compared to the controls. The combined results of this and other tests showed that patients with temporal lobe epilepsy that was lateralized to the right (or in the ride side of the brain) were impaired on all visual tests. Results also showed that the characteristics and location of a lesion do not play an important role in determining the impairment of learning and memory abilities.

Visual Selective Reminding Procedure

     In another study conducted by Anna Rita Giovagnoli, Maria Casazza, and Guiliano Avanzini (1995), patients with right and left temporal epilepsy were tested with a visual selective reminding procedure (Giovagnoli et al., 1995). A visual selective reminding procedure is when a patient is given the task of learning 10 abstract designs. The items are shown to the patients in the same order, and they are allowed ten seconds to copy each design and then reproduce as many designs as they can. Next, the test administrator presents the designs that had not been remembered or the reproductions that had been different from the model design in one or more details. This procedure continues until either the patient can reproduce two correct lists without reminding or until 18 trials were completed.

Electrodes in Brain
Image courtesy of http://www.nature.com
     Patients with right temporal lobe epilepsy were deficient in learning the designs. This is because there was impairment in the storing of visual material. Visual material is information that is constantly being retrieved from long-term memory. This retrieval system was impaired in the case of right temporal lobe epilepsy patients. The patients with left temporal lobe epilepsy acted similarly to the control patients of the experiment. The study also showed that the lateralization (side of the brain) of temporal lobe epilepsy had no effect on how constructive ability (the ability to construct images in the brain), visual perception (the brain's perception of information coming in through the eyes), or attention (the brain's way of focusing on single events or objects) was measured. This suggests that the difference in memory performance is relatively free of other brain functions and that the visual selective reminding procedure is primarily a learning test, and not a brain-functioning test.


 

Sympotoms of TLE •  Continued