Neuropsychology in temporal lobe epilepsy: influences from cognitive neuroscience and functional neuroimaging

Abstract

Neuropsychologists assist in diagnosis (i.e., localization of dysfunction) and in prediction (i.e., how cognition may change following surgery) in individuals being considered for temporal lobe surgery. The current practice includes behavioural testing as well as mapping function via stimulation, inactivation, and (more recently) functional imaging. These methods have been providing valuable information in surgical planning for 60 years. Here, we discuss current assessment strategies and highlight how they are evolving, particularly with respect to integrating recent advances in cognitive neuroscience.

Figure 1

Presurgical fMRI for language in patients with TLE. Two individuals with epileptic foci in the left temporal lobe were scanned using a panel of tasks involving 25-second blocks of verb generation, sentence completion, category fluency, and naming to confrontation, alternating with 20-second blocks of fixation. The case in (a) shows left-hemisphere dominance, and the case in (b) shows right hemisphere dominance. In figure, L: left and R: right; threshold is set to z > 2.25.

Figure 2

Autobiographical memory profiles. fMRI maps illustrate regions demonstrating higher activation for during autobiographical memory recall (retrieving personal memories based on event cues) relative to semantic retrieval (sentence completion). Note that there is less activity in the epileptogenic mesial temporal region for both left and right TLE groups compared to healthy controls (n = 10 per group). In figure, L: left and R: right; threshold set at P < .0001, uncorrected.