Year: 2005
Type: dissertation
Abstract: Age-related differences in information processing have often been explained \nthrough deficits in older adults' ability to ignore irrelevant stimuli and suppress \ninappropriate responses through inhibitory control processes. Functional imaging \nwork on young adults by Nelson and colleagues (2003) has indicated that inferior \nfrontal and anterior cingulate cortex playa key role in resolving interference effects \nduring a delay-to-match memory task. Specifically, inferior frontal cortex appeared to \nbe recruited under conditions of context interference while the anterior cingulate was \nassociated with interference resolution at the stage of response selection. Related \nwork has shown that specific neural activities related to interference resolution are not \npreserved in older adults, supporting the notion of age-related declines in inhibitory \ncontrol (Jonides et aI., 2000, West et aI., 2004b). \nIn this study the time course and nature of these inhibition-related processes \nwere investigated in young and old adults using high-density ERPs collected during a \nmodified Sternberg task. Participants were presented with four target letters followed \nby a probe that either did or did not match one of the target letters held in working \nmemory. Inhibitory processes were evoked by manipulating the nature of cognitive \nconflict in a particular trial. Conflict in working memory was elicited through the \npresentation of a probe letter in immediately previous target sets. Response-based \nconflict was produced by presenting a negative probe that had just been viewed as a \npositive probe on the previous trial. \nYounger adults displayed a larger orienting response (P3a and P3b) to positive \nprobes relative to a non-target baseline. Older adults produced the orienting P3a and \n3 \nP3b waveforms but their responses did not differentiate between target and non-target \nstimuli. This age-related change in response to targetness is discussed in terms of \n"early selection/late correction" models of cognitive ageing. \nYounger adults also showed a sensitivity in their N450 response to different \nlevels of interference. Source analysis of the N450 responses to the conflict trials of \nyounger adults indicated an initial dipole in inferior frontal cortex and a subsequent \ndipole in anterior cingulate cortex, suggesting that inferior prefrontal regions may \nrecruit the anterior cingulate to exert cognitive control functions. Individual older \nadults did show some evidence of an N450 response to conflict; however, this \nresponse was attenuated by a co-occurring positive deflection in the N450 time \nwindow. It is suggested that this positivity may reflect a form of compensatory \nactivity in older adults to adapt to their decline in inhibitory control.
Author: William J. Tays
Language: English
Subfield: Cognitive Neuroscience
Field: Neuroscience
Domain: Life Sciences
Open Access status: green
OpenAlex ID: W2254169811