BMe Research Grant
Our results in connection with these research questions have been already published in peer reviewed international journals. I am the first author of one of them (Nagy et al., 2020, PLoS ONE, impact factor: 2.74, Q1 journal) and the corresponding author of another (Gaál et al., 2020, Frontier in Human Neuroscience, impact factor: 2.67, Q1 journal).
Figure 1: Experimental design of the modified Simon task
Figure 2: Reaction times (ms) and error rates (%) in different conditions of the modified Simon task in young (blue) and old (red) adults (mean ± SD). Asterisk – significant difference, CG – congruent gaze, ICG – incongruent gaze
Figure 3: Target-locked s-LRP component (difference of C3-C4 electrodes over the motor cortex) evoked in the modified Simon task in young and old adults. Waveforms: red – congruent Simon, congruent gaze (CS-CG); black – incongruent Simon, congruent gaze (ICS-CG); blue – congruent Simon, incongruent gaze (CS-ICG); green – incongruent Simon, incongruent gaze (ICS-ICG)
Additionally, we revealed that the irrelevant gaze-orientation did not have any effect on the target categorization measured with the P3b component (centro-parietally distributed positive going ERP component) or the motor response execution which is measured by the r-LRP component (response-locked lateralized readiness potential, which is a negative going difference component evoked over the motor cortex) (Figure 4). The analysis of these two ERP components showed age and cognitive load effects, which are established in the literature. In detail, the effectiveness of stimulus-categorization and the activated motor program execution is decreased with age, which was revealed by the smaller amplitude and later latency in the P3b and earlier latency and larger amplitude in the r-LRP components in older adults compared to younger ones. (The earlier latency and larger amplitude in r-LRP shows less effective processes due to the larger and longer activation, thus higher activation threshold is needed from the motor cortex in order to execute the motor response). Moreover, later latency and smaller amplitude in the P3b component was evoked in the incongruent Simon conditions compared to the congruent Simon conditions, which suggests less effective stimulus-categorization when the cognitive capacity is more loaded.
Figure 4: Target-locked P3b (measured at Pz electrode, left figure) and response-locked r-LRP components (difference of C3-C4 electrodes over motor cortex, right figure) evoked in the modified Simon task in young and old adults. Waveforms: red – congruent Simon, congruent gaze (CS-CG); black – incongruent Simon, congruent gaze (ICS-CG); blue – congruent Simon, incongruent gaze (CS-ICG); green – incongruent Simon, incongruent gaze (ICS-ICG)
Therefore, elderly people processed the task-irrelevant stimulus to a greater extent, which could be supported by the larger N170 amplitude in this age-group (negative going ERP component, which is connected to face-specific early visual processing and evoked at parieto-occipital visual areas) for the irrelevant faces compared to younger adults (Figure 5). Even though both age-groups performed better than chance in the old/new face recognition test (the discrimination index was significantly larger than 0 in young and old adults as well) but younger adults performed better than older ones. On top of that, the LPC component (late parietal component; positive going ERP component) which is related to recollection and recognition processes was only observed in the younger age-group but not in the old one (however, it was larger for new faces compared to old ones, which is in contrast with the previous literature). So eventually, the older age-group could not consolidate and retrieve the task-irrelevant information effectively.
In conclusion, we could detect only the negative effect of the task-irrelevant information on the cognitive load and cognitive conflict resolution in the older age group, but we found no evidence in this paradigm for the supporting role of the increased task-irrelevant stimuli processing.
Figure 5: Top – irrelevant face-locked N170 component and the evoked early visual face-processing in the modified Simon task (measured at PO7 and PO8 in the parieto-occipital visual areas). Waveforms: red – young adults, blue – old adults
Bottom – target face-locked LPC component (recollection effect measured at Pz electrode) in the old/new face recognition test, which could be detected just in young adults. Waveforms: red – right response for new faces (new); black – right response for old faces (old); blue - wrong response to new faces (old); green – wrong response to old faces (new)