Abstracts

Neurosurgical treatment of patients with frontal lobe epilepsy (FLE) is highly effective in eliminating seizures in patients who are refractory to anticonvulsant medications. Surgical resections, however, cannot reverse the damage resulting from years of pathological brain activity and may even intensify neuropsychological deficits. In particular, patients with FLE often show deficits in memory and attention following surgery that serve as a barrier to rehabilitation and limit their independent functioning. This investigation explored post-operative deficits in memory and attention in patients with FLE from a neuropsychological perspective of disrupted inhibition. We proposed that two adaptive inhibitory mechanisms--attentional suppression and retrieval inhibition--are impaired in patients with FLE and account for their post-operative impairments in attention and memory. This hypothesis was explored in three experiments designed to measure inhibition in selective attention ([italic]negative priming[/italic]), episodic memory ([italic]directed forgetting[/italic]), and semantic memory ([italic]semantic priming[/italic]). It was proposed that patients with FLE would be impaired on all three tasks of inhibition due to an underlying impairment in inhibitory processing that relies on intact frontal lobe functioning.
Participants in this investigation were 20 patients with FLE who underwent a unilateral frontal resection and 20 healthy controls. All participants completed a series of neuropsychological tests, in addition to three computeralized reaction-time tasks of inhibitory processing.
Results showed that patients with left FLE were impaired on all three tasks of inhibitory processing. Patients with right FLE were impaired on a task of semantic retrieval, although they showed [italic]reduced[/italic] inhibition in episodic retrieval. Inter-task correlations revealed that inhibition in attention was modestly related to inhibition in episodic retrieval, while inhibition in semantic retrieval was unrelated to other task performances.
These results suggest that inhibitory processing is disrupted in patients with FLE following surgical resection, especially left frontal lobe resections, and that inhibitory failures occur across domains of memory and attention. Furthermore, these results support the theory that inhibitory functioning in selective attention, episodic memory, and semantic memory involves dissociable processes, although these processes may jointly rely on the integrity of the frontal lobes. This research has important theoretical implications for clarifying the role of the frontal lobes in inhibition, as well as important clinical implications for predicting cognitive deficits in patients with FLE following surgical resection.
[Supported by: The Epilepsy Foundation through the generous support of the American Epilepsy Society.]