Emergence of ß-Band Oscillations in the Aged Rat Amygdala during Discrimination Learning and Decision Making Tasks.

ABSTRACT

Older adults tend to use strategies that differ from those used by young adults to solve decision-making tasks. MRI experiments suggest that altered strategy use during aging can be accompanied by a change in extent of activation of a given brain region, inter-hemispheric bilateralization or added brain structures. It has been suggested that these changes reflect compensation for less effective networks to enable optimal performance. One way that communication can be influenced within and between brain networks is through oscillatory events that help structure and synchronize incoming and outgoing information. It is unknown how aging impacts local oscillatory activity within the basolateral complex of the amygdala (BLA). The present study recorded local field potentials (LFPs) and single units in old and young rats during the performance of tasks that involve discrimination learning and probabilistic decision making. We found task- and age-specific increases in power selectively within the ß range (15-30 Hz). The increased ß power occurred after lever presses, as old animals reached the goal location. Periods of high-power ß developed over training days in the aged rats, and was greatest in early trials of a session. ß Power was also greater after pressing for the large reward option. These data suggest that aging of BLA networks results in strengthened synchrony of ß oscillations when older animals are learning or deciding between rewards of different size. Whether this increased synchrony reflects the neural basis of a compensatory strategy change of old animals in reward-based decision-making tasks, remains to be verified.