Inhibitory breakdown and dementia of the Alzheimer type: a general phenomenon?

Several recent studies have provided substantial support for the proposal that a decrease in inhibitory processing may play an important role in cognitive changes occurring in the early stages of Dementia of the Alzheimer Type (DAT). The question addressed by the present study was whether these deficits are the result of the failure of a general inhibitory mechanism, or whether DAT is associated with selective decreases in a subset of inhibitory processes. For this, a computerized battery of tasks assessing several inhibitory mechanisms was administered to 28 mild DAT patients and 28 matched elderly adults. The results showed that DAT patients failed to produce Negative Priming effects and were severely impaired in the Stroop task. However, no evidence was found for an impairment on the Go-No go task and only limited impairment on the Stop Signal task, suggesting that in the early stages of the disease, not all inhibitory mechanisms are uniformly impaired.