Age-Related Effects in Working Memory Recognition Modulated by Retroactive Interference
The journals of gerontology. Series A, Biological sciences and medical sciences
One of the main causes for age-related declines in working memory is a higher vulnerability to retroactive interference due to a reduced ability to suppress irrelevant information. However, the underlying neural correlates remain to be established. Magnetoencephalography was used to investigate differential neural patterns in young and older adults performing an interference-based memory task with two experimental conditions, interrupting and distracting, during successful recognition.
... lly, both types of retroactive interference significantly impaired accuracy at recognition more in older adults than in young adults with the latter exhibiting greater disruptions by interrupters. Magnetoencephalography revealed the presence of differential age-related neural patterns. Specifically, time-modulated activations in temporo-occipital and superior parietal regions were higher in young adults compared with older adults for the interrupting condition. These results suggest that age-related deficits in inhibitory mechanisms that increase vulnerability to retroactive interference may be associated with neural under-recruitments in a high-interference task. T HE increasing life expectancy occurred during the last decades demands the study of the particular needs of aged individuals (1); therefore, the study of age-related cognitive declines and their neural correlates is crucial. Aging is associated with memory impairments (2,3), particularly in working memory (WM). This theoretical construct involves the ability to retain and actively manipulate information temporarily. WM is a capacity-limited system, which affects both storage and processing, resulting in limited maintenance and attention capacity, respectively (4). WM supports other high-level cognitive processes, such as storage, rehearsal, and executive functions (5). Executive functions, in turn, include inhibitory mechanisms, necessary to delete task-irrelevant information and resolve interference during memory maintenance (6). Regarding the neural correlates of WM, neuroimaging research suggests that it represents an emergent property with neural interactions between the prefrontal cortex (PFC) and more posterior regions of the brain (7). Specifically, it seems that controlled top-down signals from the PFC modulate the storage in posterior parietal regions (8). Inhibitory deficit hypothesis (9) provides a theoretical framework to understand which cognitive processes remain stable and which are affected by aging. Specifically, it postulates age-related difficulties to reduce interference from task-irrelevant information due to inefficient inhibitory control mechanisms (10,11). Age-related decrements in WM performance at recognition have been reported (12-16), especially in tasks in which subsequent events interfere with previous ones during the maintenance of information (17). This phenomenon, known as retroactive interference (RI), reduces the ability to suppress irrelevant information and also leads to declines in bottom-up mechanisms. Two main sources of RI might affect inhibitory mechanisms, distractions, and interruptions. Distractions are referred to the irrelevant information that should be ignored and is related to top-down suppression signals from the PFC (18,19), whereas interruptions are referred to the information encountered as secondary and involve the reallocation of cognitive resources in order to reactivate disrupted representations, which is related to the medial temporal lobe (MTL) and the PFC (19,20). Distractions are defined by an