The relationship between structural MRI, FDG-PET, and memory in temporal lobe epilepsy: Preliminary results.

Structural and metabolic abnormalities of the temporal lobe are frequently found in temporal lobe epilepsy (TLE). In the present retrospective study, we investigated whether structural abnormalities evident in magnetic resonance imaging (MRI) and hypometabolism evident in [18F]fluorodeoxyglucose positron emission tomography (FDG-PET) independently influence verbal and nonverbal learning and delayed memory in patients with TLE. Sixty-eight patients with refractory unilateral TLE (35 left TLE, 33 right TLE) were divided into three groups: (1) no evidence of pathology in either MRI or FDG-PET studies (MRI-/PET-, n=15), (2) temporal FDG-PET determined hypometabolism with normal MRI findings (MRI-/PET+, n=21), and (3) evidence of temporal abnormalities in both MRI and FDG-PET studies (MRI+/PET+, n=32). A fourth group (MRI+/PET-, n=4) was too small for further statistical analysis and could not be included. Patients with MRI+/PET+ showed worse verbal memory than patients with MRI-/PET- (p<0.01), regardless of side of seizure focus. Verbal memory performance of patients with MRI-/PET+ was located between patients with MRI+/PET+ and MRI-/PET-, although group differences did not achieve statistical significance (ps>0.1). No group differences were found for nonverbal memory (p=0.27). Our results may suggest an interactive negative effect of metabolic and structural temporal lobe abnormalities on verbal memory. Still, our results are preliminary and need further validation by studies involving larger patient groups and up-to date quantitative imaging analysis methods.

Female verbal memory advantage in temporal, but not frontal lobe epilepsy.

Women show better performance than men on a range of episodic memory tasks. Evidence regarding a neuroanatomical localization of this effect remains ambiguous. It has been suggested that anterior temporal lobe structures are responsible for sex differences in verbal memory, yet temporal lobe epilepsy (TLE) and TLE surgery do not affect women's verbal memory advantage. Instead, frontal lobe regions may be relevant for female verbal memory superiority, i.e. by enabling more efficient encoding and retrieval strategies in women. The aim of the present study was to investigate whether women's verbal memory advantage can be found in patients with frontal lobe epilepsy (FLE), and how patients with FLE and those with TLE differ with regard to sex differences in verbal memory. Fifty patients with unilateral FLE (26 women, 24 men) were compared with 183 patients with unilateral TLE (90 women, 93 men) on both verbal learning and delayed memory. We found that women showed better verbal memory than men in the TLE group, but not in the FLE group. In addition, we found that patients with TLE showed worse verbal learning than those with FLE. Our findings support the idea that women's advantage in verbal memory may be related to frontal lobe function.

Are mental distress and cognitive impairment related in temporal lobe epilepsy?

OBJECTIVE: Cognitive impairment and depression often co-exist among patients with epilepsy. However, there is still debate whether depression and cognition are related in patients with temporal lobe epilepsy (TLE). Even if they were related, it is still unclear whether symptoms of depression specifically, or rather symptoms of mental distress in general, have a negative impact on cognition in patients with TLE. In the present study, we examined whether self-rated symptoms of mental distress and of depression are related to different cognitive functions in unilateral TLE. METHODS: We retrospectively studied 162 patients undergoing preoperative evaluation for epilepsy surgery (95 patients with left TLE (LTLE) and 67 patients with right TLE (RTLE)). Severity of mental distress and symptoms of depression were measured with the Symptom Checklist-90-Revised (SCL-90-R) and the Beck Depression Inventory (BDI), respectively. Bivariate correlations were calculated between these two measures and neuropsychological measures of verbal recall, figural learning, psychomotor speed, and phonemic word fluency. Due to multiple testing, a corrected level of p < 0.0063 was regarded as significant, only. RESULTS: Seventeen and 19% of patients reported meaningful mental distress and meaningful symptoms of depression, respectively. Mental distress highly correlated with symptoms of depression (rs = 0.80). We found no significant correlations of either mental distress or symptoms of depression with measures of cognitive function. CONCLUSIONS: In contrast to some former studies with smaller sample sizes, the present study could not detect a relationship of depression with cognitive impairment in patients with unilateral TLE. Likewise, mental distress and cognition were unrelated in our sample of patients. Our results may argue against theoretical models claiming a causal link between depression and cognitive impairment or a common pathogenic mechanism for these conditions in patients with TLE.

Differences in Neural Recovery From Acute Stress Between Cortisol Responders and Non-responders.

Adaptive recovery from a stressor fosters resilience. So far, however, few studies have examined brain functional connectivity in the aftermath of stress, with inconsistent results reported. Focusing on the immediate recovery from psychosocial stress, the current study compared amygdala resting-state functional connectivity (RSFC) before and immediately after psychosocial stress between cortisol responders and non-responders. Differences between groups were expected for amygdala RSFC with regions involved in down-regulation of the physiological stress response, emotion regulation, and memory consolidation. Eighty-six healthy participants (36 males/50 females) underwent a social stress paradigm inside the MRI scanner. Before and immediately after stress, resting-state (RS) fMRI scans were acquired to determine amygdala RSFC. Next, changes in connectivity from pre- to post-stress were compared between cortisol responders and non-responders. Responders demonstrated a cortisol increase, higher negative affect, and decreased heart rate variability (HRV) in response to stress compared to non-responders. A significant Sex-by-Responder-by-Time interaction was found between the bilateral amygdala and posterior cingulate cortex (PCC) and precuneus (p < 0.05, corrected). As males were also more likely to show a cortisol increase to the stress task than females, follow-up analyses were conducted for both sexes separately. Whereas no difference was observed between female responders and non-responders, male non-responders showed an increase in FC after stress between the bilateral amygdala and the PCC and precuneus (p < 0.05, corrected). The increased coupling of the amygdala with the PCC/precuneus, a core component of the default mode network (DMN), might indicate an increased engagement of the amygdala within the DMN directly after stress in non-responders. Although this study was carried out in healthy participants, and the results likely reflect normal variations in the neural response to stress, understanding the mechanisms that underlie these variations could prove beneficial in revealing neural markers that promote resilience to stress-related disorders.