Adaptive visual memory reorganization in right medial temporal lobe epilepsy

Figueiredo, Patrícia; Santana, Isabel; Teixeira, João; Cunha, Catarina; Machado, Egídeo; Sales, Francisco; Almeida, Eduarda

doi:10.1111/j.1528-1167.2008.01629.x

Cited by 19 publications

(14 citation statements)

References 51 publications

(71 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…3b, F2). Greater right hippocampal activation in controls has been reported in the literature in visual memory encoding (Figueiredo et al, 2008), and in visual scene encoding in particular (Golby et al, 2001). The posterior location of this cluster in controls is consistent with published data (Powell et al, 2005;Figueiredo et al, 2008).…”

Section: Functional Activation Differencessupporting

confidence: 89%

Structure specific analysis of the hippocampus in temporal lobe epilepsy

et al. 2009

View full text Add to dashboard Cite

The hippocampus is a major structure of interest affected by temporal lobe epilepsy (TLE). Region of interest (ROI)-based analysis has traditionally been used to study hippocampal involvement in TLE, although spatial variation of structural and functional pathology have been known to exist within the ROI. In this article, structure-specific analysis (Yushkevich et al. (2007) Neuroimage 35:1516–1530) is applied to the study of both structure and function in TLE patients. This methodology takes into account information about the spatial correspondence of voxels within ROIs on left and right sides of the same subject as well as between subjects. Hippocampal thickness is studied as a measure of structural integrity, and functional activation in a functional magnetic resonance imaging (fMRI) experiment in which subjects performed a memory encoding task is studied as a measure of functional integrity. Pronounced disease-related decrease in thickness is found in posterior and anterior hippocampus. A region in the body also shows increased thickness in patients’ healthy hippocampi compared with controls. Functional activation in diseased hippocampi is reduced in the body region compared to controls, whereas a region in the tail showing greater right-lateralized activation in controls also shows greater activation in healthy hippocampi compared with the diseased side in patients. Summary measurements generated by integrating quantities of interest over the entire hippocampus can also be used, as is done in conventional ROI analysis.

show abstract

Section: Functional Activation Differencessupporting

confidence: 89%

Structure specific analysis of the hippocampus in temporal lobe epilepsy

et al. 2009

View full text Add to dashboard Cite

show abstract

“…However, in contrast to some authors [Detre et al, 1998; Stern et al, 1996; Szaflarski et al, 2004] who have found bilateral‐symmetrical hippocampal activation in normal controls and bilateral‐asymmetrical hippocampal activation in MTLE patients, we did not find hippocampal activations in the three groups during encoding stage of a visual content. This discrepancy could be explained by (1) differences in the fMRI task design; and/or (2) lack of MTL activation in our study owing to those technical limitations mentioned before, such as geometric distortions, signal loss artifacts, and partial volume effects [Figueiredo et al, 2008; Powell et al, 2004, 2005, 2007]. For different reasons some other functional studies have also failed to demonstrate hippocampal activation either during encoding or retrieval stages [Cabeza and Nyberg, 2000; Schacter and Wagner, 1999].…”

Section: Discussionmentioning

confidence: 90%

Brain plasticity for verbal and visual memories in patients with mesial temporal lobe epilepsy and hippocampal sclerosis: An fMRI study

Alessio

Pereira

Sercheli

et al. 2011

Human Brain Mapping

View full text Add to dashboard Cite

We aimed to identify the brain areas involved in verbal and visual memory processing in normal controls and patients with unilateral mesial temporal lobe epilepsy (MTLE) associated with unilateral hippocampal sclerosis (HS) by means of functional magnetic resonance imaging (fMRI). The sample comprised nine normal controls, eight patients with right MTLE, and nine patients with left MTLE. All subjects underwent fMRI with verbal and visual memory paradigms, consisting of encoding and immediate recall of 17 abstract words and 17 abstract drawings. A complex network including parietal, temporal, and frontal cortices seems to be involved in verbal memory encoding and retrieval in normal controls. Although similar areas of activation were identified in both patient groups, the extension of such activations was larger in the left-HS group. Patients with left HS also tended to exhibit more bilateral or right lateralized encoding related activations. This finding suggests a functional reorganization of verbal memory processing areas in these patients due to the failure of left MTL system. As regards visual memory encoding and retrieval, our findings support the hypothesis of a more diffuse and bilateral representation of this cognitive function in the brain. Compared to normal controls, encoding in the left-HS group recruited more widespread cortical areas, which were even more widespread in the right-HS group probably to compensate for their right mesial temporal dysfunction. In contrast, the right-HS group exhibited fewer activated areas during immediate recall than the other two groups, probably related to their greater difficulty in dealing with visual memory content.

show abstract

“…Therefore, the function of ipsilateral mesial temporal lobe is important in determining the presence of memory change after surgery 4 19 24. On the other hand, how the postoperative memory function is supported is another important issue to be investigated, and studies supporting the functional reserve models suggest that the postoperative memory function may rely on the ability of the contralateral mesial temporal lobe before surgery 26 36 37 38. The present study extended earlier findings26 39 by showing that the function of the contralateral mesial temporal lobe might play an important role in supporting ipsilateral memory function after surgery.…”

Section: Discussionmentioning

confidence: 99%

Pre- and postoperative fMRI and clinical memory performance in temporal lobe epilepsy

Cheung

Chan

Lam

et al. 2009

Journal of Neurology, Neurosurgery & Psychiatry

View full text Add to dashboard Cite

Objective:The present study aimed to examine and compare memory processing in patients with unilateral temporal lobe epilepsy (TLE) before and after surgery using functional magnetic resonance imaging (fMRI).Methods:Seventeen preoperative patients with unilateral TLE (nine left, eight right) and eight healthy controls were recruited. They performed a complex visual scene-encoding task during fMRI to measure memory activation in the mesial temporal lobe. Their memory performance was evaluated using standardised neuropsychological tests. After unilateral temporal lobe resection (either temporal lobectomy, selective amygdalohippocampectomy or lesionectomy), the same fMRI paradigm and neuropsychological tests were administered to the patient group.Results:Left-TLE patients demonstrated a decline in verbal memory after left temporal lobe resection. Their postoperative verbal and visual memory performance was positively associated with postoperative functional activation in the right mesial temporal lobe, whereas the postoperative memory performance of right-TLE patients was positively associated with postoperative functional activation in the left mesial temporal lobe, contralateral to their respective side of resection.Conclusion:Postoperative memory performance was significantly associated with functional activation contralateral to the side of resection in patients with unilateral TLE, and the function of the contralateral mesial temporal lobe might play an important role in supporting memory performance after temporal lobe resection.

show abstract

Adaptive visual memory reorganization in right medial temporal lobe epilepsy

Abstract: SUMMARY

Cited by 19 publications

References 51 publications

Structure specific analysis of the hippocampus in temporal lobe epilepsy

Structure specific analysis of the hippocampus in temporal lobe epilepsy

Brain plasticity for verbal and visual memories in patients with mesial temporal lobe epilepsy and hippocampal sclerosis: An fMRI study

Pre- and postoperative fMRI and clinical memory performance in temporal lobe epilepsy

Contact Info

Product

Resources

About