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An extensive literature has demonstrated a detriment to the maintenance of information in working memory (WM) by interference from the external environment 1-9. External interference can be classified into two general types; interference by irrelevant information one intends to ignore: distraction, and interfering information which demands attention as part of another (secondary) task goal: interruption. Studies comparing these types of external interference using a within-participant design enable assessment of the neuro-behavioral impact of goal-focused top-down attention in the processing and resolution of external interference.
Recently, the Gazzaley lab designed a paradigm that facilitates comparison of ‘to-be-attended’ interruptions and ‘to-be-ignored’ distractions that occur in the setting of a working memory task. Emerging evidence from this paradigm suggests that these different types of external interference exert distinct effects on behavior and have distinct underlying neural mechanisms 2-5,10,11. This paradigm has revealed differences in external interference processing in normal aging 2,3,4,10,11; though aging deficits in the context of interference are not always found 5; it has also distinguished mechanisms of interference by distractors versus interruptors using high-level visual stimulation of faces and scenes 2,3,4,12, low-level visual motion of dot kinematograms 5,10,11, and low-level auditory motion of frequency sweeps 5.
External Interference and Aging
External interference induces a detrimental impact on working memory throughout the lifespan, although older adults exhibit a more negative impact than younger adults 2,3,13-18. Older adults also exhibit different patterns of neural activity compared to younger adults when attempting to resolve this interference 3,4,17,21. However, some studies do not find evidence for such age-related behavioral 5,19,20 or neural 5 differences with interference.
Interestingly, the impact of aging on resolving interference seems to differ by sensory modality, although this issue remains unresolved at present. Visual intrasensory interference has been widely shown to exhibit age-related decline (summarized in an extensive review 22). In contrast, many experiments suggest no age-related deficits during intra-sensory auditory interference 19,22-25, while other studies demonstrate significant age-related increases in auditory distractibility 19,22,26-32. In addition, the salience of interfering stimuli (congruent or incongruent between the cue and probe stimuli) 2, and stimulus complexity (high or low processing load) 5 may interact with interference processing and its differences across task goals and age.
The paradigm described here supplements the aging interference literature by probing the mechanisms of top-down attention (in the form of task goals) and resolution of external interfering stimuli. Evidence from the visual face & scene version of this paradigm indicates an interaction between aging and interference type, with older adults demonstrating even greater vulnerability to attended interruptors relative to ignored distractors 3,4. Characterizing the behavioral and neural differences between these types of interference are important to understand how cognitive control abilities change with aging.
Why do older adults show exacerbated deficits in resolving to-be-attended interruptors? Are older adults impaired by excessive processing of interruptors when they are presented, or by an inability to re-activate representations of the primary goal-relevant stimuli after interruptions, or by prolonged processing of interruptors after they are no longer present or relevant 33? To address these questions, the current paradigm’s design allows for comparison of neural activity at time-points before, during, and after different types of interference. For instance, by comparing neural activity elicited by ignored distraction versus activity during attended interruptions, one can ascertain the specific impact of top-down attention on resolution of interference in working memory.
Several studies have implemented multiple variants of this interference paradigm to understand the neural correlates of the different types of external interference both at high spatial and temporal resolution using functional magnetic resonance imaging (fMRI) and electroencephalography (EEG), respectively. This paradigm has also been used to clarify important distinctions between interference in the visual and auditory domains, as well as the impact of stimulus complexity and congruence on interference. Here, the paradigm variants are described in detail.