Dynamic causal modeling of reorganization of memory and language networks in temporal lobe epilepsy.

OBJECTIVE: To evaluate the alterations of language and memory functions using dynamic causal modeling, in order to identify the epileptogenic hemisphere in temporal lobe epilepsy (TLE). METHODS: Twenty-two patients with left TLE and 13 patients with right TLE underwent functional magnetic resonance imaging (fMRI) during four memory and four language mapping tasks. Dynamic causal modeling (DCM) was employed on fMRI data to examine effective directional connectivity in memory and language networks and the alterations in people with TLE compared to healthy individuals. RESULTS: DCM analysis suggested that TLE can influence the memory network more widely compared to the language network. For memory mapping, it demonstrated overall hyperconnectivity from the left hemisphere to the other cranial regions in the picture encoding, and from the right hemisphere to the other cranial regions in the word encoding tasks. On the contrary, overall hypoconnectivity was seen from the brain hemisphere contralateral to the seizure onset in the retrieval tasks. DCM analysis further manifested hypoconnectivity between the brain's hemispheres in the language network in patients with TLE compared to controls. The CANTAB® neuropsychological test revealed a negative correlation for the left TLE and a positive correlation for the right TLE cohorts for the connections extracted by DCM that were significantly different between the left and right TLE cohorts. INTERPRETATION: In this study, dynamic causal modeling evidenced the reorganization of language and memory networks in TLE that can be used for a better understanding of the effects of TLE on the brain's cognitive functions.

Prediction of delay discounting in intertemporal decisions by future thinking: Accounting for fluency, contents, and functions of future thoughts.

PURPOSE: To study the variations of delay discounting rates as a function of fluency, contents, and functions of future thoughts in healthy subjects. BACKGROUND: Delay discounting (DD) is a concept that can measure a frequent tendency toward smaller, yet immediate rewards, while a delayed reward is greater in value. DD describes people's choices in intertemporal decisions and is associated with self-control. Future thinking (FT) and having a vivid imagination of the future can reduce individuals' DD rates. However, constructing a specific episodic future representation was merely studied in relation to DD. Although fluency and contents of future thoughts have been reported related to various disorders and behaviors, their association with DD has not been previously addressed. METHODS: The present study applies a verbal fluency task named the personal future task (PFT), the functions of future thinking scale (FoFTS), and the 27-item delay discounting questionnaire (DDQ) in order to assess fluency, contents, and functions of future thoughts, and delay discounting in healthy subjects (N = 114, Female = 64%, Male = 36%, Mage = 34.22, SDage = 7.15). RESULTS: Findings indicate that fluency of future thoughts is associated with DD. Among the contents of FT categories, financial contents (future thoughts about money and real estate matters), and regarding functions of FT, engaging in FT for planning are related to DD. Due to the final model, the above-mentioned correlated variables can be considered as significant predictors of intertemporal choices when controlling for education and gender (R2  = 0.4, Adjusted R2  = 0.33, F = 5.186, p-value = 0.001). CONCLUSION: The frequency of future thoughts one can generate, specifically future thoughts about financial contents, is associated with less short-sighted intertemporal decisions. The former relationship is enhanced for longer delays (e.g., 5-10 years). Besides, individuals who frequently engage in FT for planning (planning out sequences of actions) discount future rewards to a lesser extent.