Components of aging Graduate School of Systemic Neurosciences - Digitale Hochschulschriften der LMU
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Age-related cognitive decline has been linked to a reduction in attentional resources that are assumed to result from alterations in the aging brain. A core ability that is subject to age-related decline is visual attention, which enables individuals to select the most important information for conscious processing and action. However, visual attention is considered a conglomerate of various functions and the specific components underlying age differences in performance remain little understood. The present PhD project aimed at dissociating age effects on several (sub-) components that concur in visual attention tasks within a neurocognitive approach. Established and theoretically grounded psychological paradigms that allow separating various attentional components were combined with event-related potentials (ERPs), which provide a temporally fine-graded dissociation of cognitive processes involved in a task.
1st Project
The first project was designed to determine the origin(s) of age-related decline in visual search, a key paradigm of attention research. To pursue this goal on a micro-level, response time measures in a compound-search task, in which the target-defining feature of a pop-out target (color/shape) was dissociated from the response-defining feature (orientation), were coupled with lateralized ERPs. Several ERP components tracked the timing of processing stages involved in this task, these being (1) allocation of attention to the target, marked by the posterior-contralateral negativity (PCN), (2) target analyses in vSTM, marked by the sustained posterior-contralateral negativity (SPCN), (3) response selection, marked by the stimulus-locked lateralized readiness potential (LRP) and (4) response execution, marked by the response-locked LRP. Slowed response times (RT) in older participants were associated with age differences in all analyzed ERPs, indicating that behavioural slowing accrues across multiple stages within the information processing stream. Furthermore,
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behavioral data and ERPs were analyzed with respect to age and carry-over effects from one trial to the next. The intertrial analyses revealed relatively automatic processes – such as dimension weighting facilitating the early stage of visual selection, and response weighting facilitating the late stage of response execution – to be preserved in older age. By contrast, more controlled processes – such as the flexible stimulus-response (S-R) (re-) mapping across trials on the intermediate stages of response selection - were particularly affected by aging. This indicates that besides general slowing, specific age decrements in executively controlled processes contribute to age-related decline in visual search.
2nd Project
The second project explored neural markers of individual and age differences in attention parameters formally integrated in Bundesen’s computational Theory of Visual Attention (TVA). According to the model, two parameters of general visual attention capacity, perceptual processing speed C and visual short-term memory (vSTM) storage capacity K are defined and can be modeled mathematically independently for a particular individual. More recently, the neural interpretation of the model (NTVA) suggested that the two functions (at least partly) rely on distinct brain mechanisms. To test this assumption in an empirical approach, individual TVA-based estimates were derived in a standard TVA whole report task, and ERPs of the same participants were recorded in an adapted EEG-compatible version of the task. In the first study of the second project, we explored neurophysiological markers of interindividual differences in the two functions in younger participants. The results revealed distinct ERP correlates to be related to the parameters: Individuals with higher compared to lower processing speed C had significantly smaller posterior N1 amplitudes, suggesting that the rate of object categorization is associated with the efficiency of e
Age-related cognitive decline has been linked to a reduction in attentional resources that are assumed to result from alterations in the aging brain. A core ability that is subject to age-related decline is visual attention, which enables individuals to select the most important information for conscious processing and action. However, visual attention is considered a conglomerate of various functions and the specific components underlying age differences in performance remain little understood. The present PhD project aimed at dissociating age effects on several (sub-) components that concur in visual attention tasks within a neurocognitive approach. Established and theoretically grounded psychological paradigms that allow separating various attentional components were combined with event-related potentials (ERPs), which provide a temporally fine-graded dissociation of cognitive processes involved in a task.
1st Project
The first project was designed to determine the origin(s) of age-related decline in visual search, a key paradigm of attention research. To pursue this goal on a micro-level, response time measures in a compound-search task, in which the target-defining feature of a pop-out target (color/shape) was dissociated from the response-defining feature (orientation), were coupled with lateralized ERPs. Several ERP components tracked the timing of processing stages involved in this task, these being (1) allocation of attention to the target, marked by the posterior-contralateral negativity (PCN), (2) target analyses in vSTM, marked by the sustained posterior-contralateral negativity (SPCN), (3) response selection, marked by the stimulus-locked lateralized readiness potential (LRP) and (4) response execution, marked by the response-locked LRP. Slowed response times (RT) in older participants were associated with age differences in all analyzed ERPs, indicating that behavioural slowing accrues across multiple stages within the information processing stream. Furthermore,
v
behavioral data and ERPs were analyzed with respect to age and carry-over effects from one trial to the next. The intertrial analyses revealed relatively automatic processes – such as dimension weighting facilitating the early stage of visual selection, and response weighting facilitating the late stage of response execution – to be preserved in older age. By contrast, more controlled processes – such as the flexible stimulus-response (S-R) (re-) mapping across trials on the intermediate stages of response selection - were particularly affected by aging. This indicates that besides general slowing, specific age decrements in executively controlled processes contribute to age-related decline in visual search.
2nd Project
The second project explored neural markers of individual and age differences in attention parameters formally integrated in Bundesen’s computational Theory of Visual Attention (TVA). According to the model, two parameters of general visual attention capacity, perceptual processing speed C and visual short-term memory (vSTM) storage capacity K are defined and can be modeled mathematically independently for a particular individual. More recently, the neural interpretation of the model (NTVA) suggested that the two functions (at least partly) rely on distinct brain mechanisms. To test this assumption in an empirical approach, individual TVA-based estimates were derived in a standard TVA whole report task, and ERPs of the same participants were recorded in an adapted EEG-compatible version of the task. In the first study of the second project, we explored neurophysiological markers of interindividual differences in the two functions in younger participants. The results revealed distinct ERP correlates to be related to the parameters: Individuals with higher compared to lower processing speed C had significantly smaller posterior N1 amplitudes, suggesting that the rate of object categorization is associated with the efficiency of e
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