Supine posture affects cortical plasticity in elderly but not young women during a word learning-recognition task

- 30 young and 20 old women were split in 2 h horizontal Bed Rest vs. sitting groups.
- In a word learning task Bed Rest elderly showed reduced left Recognition Potential.
- A correlation was found in elderly between lower performance and right shift of RP.
- 2 h Bed Rest in elderly is associated to dysfunctional loss of cortical asymmetry.

The present research investigated the hypothesis that elderly and horizontal body position contribute to impair learning capacity. To this aim, 30 young (mean age: 23.2 years) and 20 elderly women (mean age: 82.8 years) were split in two equal groups, one assigned to the Seated Position (SP), and the other to the horizontal Bed Rest position (hBR). In the Learning Phase, participants were shown 60 words randomly distributed, and in the subsequent Recognition Phase they had to recognize them mixed with a sample of 60 new words. Behavioral analyses showed age-group effects, with young women exhibiting faster response times and higher accuracy rates than elderly women, but no interaction of body position with age group was found. Analysis of the RP component (250-270 ms) revealed greater negativity in the left Occipital gyrus/Cuneus of both sitting age-groups, but significantly left-lateralized RP in left Lingual gyrus only in young bedridden women. Elderly hBR women showed a lack of left RP lateralization, the main generator being located in the right Cuneus. Young participants had the typical old/new effect (450-800 ms) in different portions of left Frontal gyri/Uncus, whereas elderly women showed no differences in stimulus processing and its location. EEG alpha activity analyzed during a 3 min resting state, soon after the recognition task, revealed greater alpha amplitude (i.e., cortical inhibition) in posterior sites of hBR elderly women, a result in line with their inhibited posterior RP. In elderly women the left asymmetry of RP was positively correlated with both greater accuracy and faster responses, thus pointing to a dysfunctional role, rather than a compensatory shift, of the observed right RP asymmetry in this group. This finding may have important clinical implications, with particular regard to the long-term side-effects of forced Bed Rest on elderly patients.