Memory Control: Investigating the Consequences and Mechanisms of Directed Forgetting in Working Memory.

Can people control what they remember and what they forget? Directed forgetting is an experimental method for investigating this question. Prior research has most commonly studied directed forgetting in a long-term memory context using long lists (i.e., greater than 6 items) and test delays of minutes or hours. My dissertation steps outside this standard paradigm and examines directed forgetting within working memory, when forgetting is performed on memory representations that are currently held in mind, potentially allowing for more targeted control. My dissertation has two main research aims: (1) to document the effectiveness of directed forgetting implemented within working memory using explicit long-term memory tests and implicit measures of semantic and proactive interference, and (2) to examine the role of rehearsal in directed forgetting within working memory. Results demonstrated that people could voluntarily forget specific memoranda within a canonical working memory task, and that this forgetting diminished both semantic and proactive interference and reduced the long-term memorability of these items. Moreover, additional experimental evidence indicated that articulatory suppression interfered with directed forgetting and that forgetting could be performed in isolation, without the presence of competitors to remember. In combination, these experiments suggest that directed forgetting within working memory attenuates the strength of the to-be-forgotten memory representations, that it requires an active control process that is limited by articulatory suppression, and that it can be performed efficiently regardless of whether or not additional to-be-remembered items are present. This research expands our knowledge of whether and how people can voluntarily control the contents of memory by further characterizing the consequences and mechanisms of directed forgetting within working memory.PhDPsychologyUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/108778/1/sfestini_1.pd

Backward Compatibility Effects in Younger and Older Adults

In many dual-task situations, responses to the second of two tasks are slowed when the time between tasks is short. The response-selection bottleneck model of dual-task performance accounts for this phenomenon by assuming that central processing of the second task is blocked by a bottleneck until central processing of Task 1 is complete. This assumption could be called into question if it could be demonstrated that the response to Task 2 affected the central processing of Task 1, a backward response compatibility effect. Such effects are well-established in younger adults. Backward compatibility effects in older (as well as younger) adults were explored in two experiments. The first experiment found clear backward response compatibility effects for younger adults but no evidence of them for older adults. The second experiment explored backward stimulus compatibility and found similar effects in both younger and older adults. Evidence possibly consistent with some pre-bottleneck processing of Task 2 central stages also was found in the second experiment in both age groups. For younger adults, the results provide further evidence falsifying the claim of an immutable response selection bottleneck. For older adults, the evidence suggested that Task 2 affects Task 1 when there is stimulus compatibility but not when there is response compatibility

The Busier the Better: Greater Busyness is Associated with Better Cognition

Sustained engagement in mentally challenging activities has been shown to improve memory in older adults. We hypothesized that a busy schedule would be a proxy for an engaged lifestyle and would facilitate cognition. Here, we examined the relationship between busyness and cognition in adults aged 50-89. Participants (N = 330) from the Dallas Lifespan Brain Study completed a cognitive battery and the Martin and Park Environmental Demands Questionnaire (MPED), an assessment of busyness. Results revealed that greater busyness was associated with better processing speed, working memory, episodic memory, reasoning, and crystallized knowledge. Hierarchical regressions also showed that, after controlling for age and education, busyness accounted for significant additional variance in all cognitive constructs—especially episodic memory. Finally, an interaction between age and busyness was not present while predicting cognitive performance, suggesting that busyness was similarly beneficial in adults aged 50-89. Although correlational, these data demonstrate that living a busy lifestyle is associated with better cognition

Altered cerebellar connectivity in Parkinson’s patients ON and OFF L-DOPA medication

Although nigrostriatal changes are most commonly affiliated with Parkinson’s disease, the role of the cerebellum in Parkinson’s has become increasingly apparent. The present study used lobule-based cerebellar resting state functional connectivity to (1) compare cerebellar-whole brain and cerebellar-cerebellar connectivity in Parkinson’s patients both ON and OFF L-DOPA medication and controls, and to (2) relate variations in cerebellar connectivity to behavioral performance. Results indicated that, when contrasted to the control group, Parkinson’s patients OFF medication had increased levels of cerebellar-whole brain and cerebellar-cerebellar connectivity, whereas Parkinson’s patients ON medication had decreased levels of cerebellar-whole brain and cerebellar-cerebellar connectivity. Moreover, analyses relating levels of cerebellar connectivity to behavioral measures demonstrated that, within each group, increased levels of connectivity were most often associated with improved cognitive and motor performance, but there were several instances where increased connectivity was related to poorer performance. Overall, the present study found medication-variant cerebellar connectivity in Parkinson’s patients, further demonstrating cerebellar changes associated with Parkinson’s disease and the moderating effects of medication