Phasic alerting increases visual processing speed in amnestic mild cognitive impairment

External warning cues temporarily increase the brain's sensitivity for upcoming events. Such increased levels of phasic alertness help individuals to flexibly adapt their reactions to the fast-changing requirements of highly complex visual environments. Previous studies reported that both healthy younger and older adults profit from phasic alerting cues. Arguably, such an intact phasic alerting mechanism could be even more relevant in pathologically aging individuals who are characterized by pronounced reductions of general processing capacity. The present study employed a theory of visual attention based whole report paradigm with auditory cues in order to investigate phasic alerting effects in amnestic mild cognitive impairment (aMCI) on a purely perceptual level. In addition, aMCI patients were compared to a previously reported sample of healthy older adults. The analysis in aMCI patients indicated that their visual processing speed was significantly higher in the cue compared to the no-cue condition. Across groups, auditory alerting cues significantly increased visual processing speed. Further, visual processing speed was reduced in aMCI patients compared to healthy older adults, replicating prior findings. Taken together, the results suggest that the processing system of aMCI patients exhibits general declines but can still flexibly integrate auditory warning signals. Phasic alerting cues facilitate a temporary increase in processing speed, enabling an efficient handling of upcoming sensory information.

Right-lateralized fronto-parietal network and phasic alertness in healthy aging

Phasic alerting cues temporarily increase the brain’s arousal state. In younger and older participants, visual processing speed in a whole report task, estimated based on the theory of visual attention (TVA), is increased in cue compared to no-cue conditions. The present study assessed whether older participants’ ability to profit from warning cues is related to iFC in the cingulo-opercular and/or right fronto-parietal network. We obtained resting-state functional magnetic resonance imaging (rs-fMRI) data from 31 older participants. By combining an independent component analysis and dual regression, we investigated iFC in both networks. A voxel-wise multiple regression in older participants revealed that higher phasic alerting effects on visual processing speed were significantly associated with lower right fronto-parietal network iFC. We then compared healthy older participants to a previously reported sample of healthy younger participants to assess whether behaviour-iFC relationships are age group specific. The comparison revealed that the association between phasic alerting and cingulo-opercular network iFC is significantly lower in older than in younger adults. Additionally, it yielded a stronger association between phasic alerting and right fronto-parietal network iFC in older versus younger participants. The results support a particular role of the right fronto-parietal network in maintaining phasic alerting capabilities in aging.