In a complex and changing environment, the validity of rules or goals might change in terms of their associated reward and cost, and we often face the necessity to make a strategic decision to adaptively shift between these behavioral rules or goals. Such a decision entails assessment of the value (cost and benefit) of current and alternative rules or reward resources for the individual, and also for the group, in socially advanced species. Cognitive abilities such as flexibility in adapting to a changing environment and adaptive foraging to seek a better environment might depend on such cognitive functions that enable a thorough assessment of the value of different options and a proper and timely decision to choose the most appropriate goal. A distributed neural network involving prefrontal and medial frontal cortices regulates the use of cognitive resources to optimize exploitation of current reward resources, while minimizing the associated cost. This is referred to as executive control of goal directed behavior. Recent studies suggest that dorsolateral prefrontal, orbitofrontal and anterior cingulate cortices are involved in optimizing the exploitation of the current reward sources however, the most rostral part of the prefrontal cortex (frontopolar cortex) plays a crucial role in adjusting the tendency for exploitation, versus exploration of other alternative resources, by assessing the value of alternative tasks/goals and re-distribution of our cognitive resources. Maintaining a proper balance between exploitation and exploration tendencies might be a fundamental cognitive ability necessary for foraging behavior and cognitive flexibility in adapting to environmental demands.
Cognitive functions such as working memory and selective attention depend on the action of neuromodulators in the cerebral cortex, including acetylcholine. Drugs that act on the cholinergic system improve cognitive function in human patients and animal models. In a series of recent studies, we have demonstrated similar benefits with intermittent electrical stimulation of the basal forebrain. We specifically targeted the Nucleus Basalis (NB) of Meynert, the source of acetylcholine in the cerebral cortex. NB stimulation proved beneficial in a range of tasks involving working memory and attention. NB stimulation may be particularly beneficial to human patients with Alzheimer’s disease, for whom these functions are compromised. We examine the possible mechanisms of action of NB stimulation. These include stimulation of cortical neurons, enhancement of synaptic connections, and regulation of blood flow. We present a hypothesis on how the amyloid formation in Alzheimer’s disease leads to cognitive decline, and how NB stimulation would impact this decline. Our results offer promise for the application of deep brain stimulation as a therapy for Alzheimer’s disease.