Inhibition in memory and attention: The role of the frontal lobes

This research explores the nature and extent of inhibitory failures in patients with frontal lobe damage as they relate to impaired attention and retrieval from long-term memory. Two theoretical questions were of primary interest in this investigation. First, we explored the possibility that patients with frontal lobe damage show impaired inhibition during memory retrieval (i.e., retrieval inhibition) as well as during selective attention. Retrieval inhibition is an adaptive process that is believed to be functionally analogous to inhibition in selective attention. That is, it is a process designed to reduce the effects of retrieval interference.; Second, we evaluated whether retrieval from long-term memory represents a generalized impairment, affecting retrieval from both semantic and episodic memory stores. Therefore, a second purpose was to demonstrate that patients with frontal lobe damage show impaired inhibition during retrieval from semantic memory, as well as from episodic memory. Taken together, it was hypothesized that patients with frontal lobe damage would show impaired inhibition in selective attention and in retrieval from long-term memory; and that inhibitory failures in memory would disrupt retrieval from both semantic and episodic memory. These hypotheses were evaluated in three experiments (in patients with frontal lobe damage) that examine inhibition in selective attention, episodic memory retrieval, and semantic memory retrieval.; Across the three tasks, we found rather strong support for our hypotheses. While the frontal group as a whole was not impaired across domains, we found strong support for laterality differences in disrupted inhibition. Those with left frontal damage showed significant impairments on all three tasks, suggesting disrupted inhibition in selective attention, episodic retrieval, and semantic retrieval. Those with right frontal damage were only significantly impaired on a task of semantic retrieval, although they showed evidence of reduced inhibition in episodic retrieval as well. Patients with right frontal damage were not impaired in selective attention. These results suggest that inhibitory processing is impaired in patients with frontal lobe damage, or rather left frontal lobe damage, and that inhibitory failures occur across domains of attention and memory. A unified theory of inhibitory processing is discussed, along with clinical implications of disrupted inhibition in patients with frontal lobe dysfunction.