Functional Dissociation between Cognitive Estimation and Object Naming in Focal Temporal and Frontal Lobe Epilepsies

Abstract

Abstract Purpose This study addresses specific impairments of cognitive estimation and object naming in patients with focal temporal lobe epilepsy (TLE) and frontal lobe epilepsy (FLE). It was investigated whether selective impairments can be explained by differences in lesion localization and functional hemispheric specialization. Materials and Methods Seventy-eight patients (39 females, 39 males) with FLE and TLE were investigated using the German “Test zum Kognitiven Schätzen” and the “Boston Naming Test” to assess cognitive estimation abilities and visual object naming. Questions According to theoretical models that support a distinct hemispheric dominance for estimation and naming, it was expected that epilepsy localization in the right hemisphere would result in impairments of cognitive estimation, whereas patients with left epileptogenic foci would show deficits in object naming. Results In comparison to a healthy control group, a significant impairment in estimation performance was present in patients with right temporal mesial and right frontal epilepsy. A significant impairment of naming performance was found in patients with left temporal mesial, right temporal mesial, left temporal neocortical, and left frontal epilepsy. Overall, localization-dependent deficits were detected in patients with hippocampal sclerosis (cognitive estimation and object naming), right frontal epilepsy (cognitive estimation), and left temporal neocortical/left frontal epilepsy (object naming). In patients with right temporal neocortical epilepsy, no functional deficits were found. Conclusion It is hypothesized that there is a functional dissociation between cognitive estimation processes and object naming due to different functional specialization of the left and right hemispheres, respectively.