Spared within-hands but impaired between-hands response preparation in aging

Both facilitatory and inhibitory impairments underlie age-related differences of proactive cognitive control across the adult lifespan

We investigated two components of proactive cognitive control, response facilitation and response inhibition, in an adult lifespan sample (N=544, age range=18-91years) by administering two response-preparation tasks: a procue task, primarily involving facilitation, and an anticue task, involving both facilitation and inhibition. Cues in both tasks corresponded with the index and middle fingers of either the left or right hand. After a random preparation interval (PI) of 100-850ms following the onset of the cue signal, a single-target stimulus indicated the required response. Where procues were spatially aligned with the two fingers of the responding hand, anticues consistently indicated the two fingers of the opposite hand, requiring a remapping of cue location and response hand. This remapping requires inhibition to suppress the automatic activation of the ipsilateral responses. Previous research revealed typical reaction time (RT) profiles for procues and anticues as a function of PI. Whereas procues generate RT benefits (relative to a neutral-cue condition) already at short PIs, which increase with longer PIs, anticues generate RT costs at short PIs and RT benefits at longer PIs. Our results showed that, in the anticue task, older participants needed more preparation time to turn RT costs into RT benefits than younger participants, revealing an age-related deficit of response inhibition. Moreover, in both tasks, older participants were less able to increase RT benefits with longer PIs, revealing a deficit of response facilitation. We conclude that both facilitatory and inhibitory impairments contribute to age-related deficiencies in proactive cognitive control.

Serum 25-hydroxyvitamin D is associated with cognitive executive function in Dutch prefrail and frail elderly: a cross-sectional study exploring the associations of 25-hydroxyvitamin D with glucose metabolism, cognitive performance and depression

OBJECTIVES

The primary objective was to explore the possible association of serum 25-hydroxyvitamin D (25[OH]D) and vitamin D intake with markers of glucose metabolism, depression, and cognitive performance. In addition, we examined to what extent the associations between vitamin D and cognitive performance were modified or mediated by fasting plasma glucose (FPG) levels.

DESIGN, SETTING, AND PARTICIPANTS

Cross-sectional study using data of 127 frail or prefrail Dutch elderly, aged 65 years or older. Frailty was defined according to the criteria of Fried and colleagues. A participant was classified prefrail when 1 to 2 criteria were met; frailty was classified as the presence of 3 or more criteria.

MEASUREMENTS

Associations of 25(OH)D and vitamin D intake with markers of glucose metabolism and domain-specific cognitive performance were examined by multivariable regression analyses. The possible association of vitamin D with depression and global cognitive performance was explored by Poisson regression.

RESULTS

No associations were observed for 25(OH)D with FPG, fasting plasma insulin (FPI), Homeostasis Model Assessment-estimated Insulin Resistance (HOMA-IR), or depression. In contrast, serum 25(OH)D was positively associated with executive functioning (β 0.007, P = .01) and tended to be associated with information-processing speed (β 0.006, P = .06). FPG did not modify or mediate these associations. Vitamin D intake was not associated with cognitive performance, glucose metabolism, or depression.

CONCLUSION

This cross-sectional study suggests an association of serum 25(OH)D with domain-specific cognitive performance, in particular executive functioning and possibly information-processing speed, but not with FPG, FPI, HOMA-IR, or depression. Whether these associations are causal is yet to be demonstrated.