Dominant hemisphere functional networks compensate for structural connectivity loss to preserve phonological retrieval with aging.
BACKGROUND
Loss of hemispheric asymmetry during cognitive tasks has been previously demonstrated in the literature. In the context of language, increased right hemisphere activation is observed with aging. Whether this relates to compensation to preserve cognitive function or dedifferentiation implying loss of hemispheric specificity without functional consequence, remains unclear.


METHODS
With a multifaceted approach, integrating structural and functional imaging data during a word retrieval task, in a group of younger and older adults with equivalent cognitive performance, we aimed to establish whether interactions between hemispheres or reorganization of dominant hemisphere networks preserve function. We examined functional and structural connectivity on data from our previously published functional activation study. Functional connectivity was measured using psychophysiological interactions analysis from the left inferior frontal gyrus (LIFG) and the left insula (LINS), based on published literature, and the right inferior frontal gyrus (RIFG) based on our previous study.


RESULTS
Although RIFG showed increased activation, its connectivity decreased with age. Meanwhile, LIFG and LINS connected more bilaterally in the older adults. White matter integrity, measured by fractional anisotropy (FA) from diffusion tensor imaging, decreased significantly in the older group. Importantly, LINS functional connectivity to LIFG correlated inversely with FA.


CONCLUSIONS
We demonstrate that left hemispheric language areas show higher functional connectivity in older adults with intact behavioral performance, and thus, may have a role in preserving function. The inverse correlation of functional and structural connectivity with age is in keeping with emerging literature and merits further investigation with tractography studies and in other cognitive domains.
Stroke Research Group Addenbrooke's Hospital University of Cambridge R3, Box 83, Hills Road Cambridge CB2 2QQ UK.
Smriti
S
Agarwal
Division of Anaesthesia Addenbrooke's Hospital University of Cambridge Box 93, Hills Road Cambridge CB2 2QQ UK.
Emmanuel A
EA
Stamatakis
Developmental Cognitive Neuroscience Unit UCL Institute of Child Health 30 Guilford Street London WC1N 1EH UK.
Sharon
S
Geva
Stroke Research Group Addenbrooke's Hospital University of Cambridge R3, Box 83, Hills Road Cambridge CB2 2QQ UK.
Elizabeth A
EA
Warburton
Aging; DTI; PPI; functional connectivity; language; phonology; word retrieval
Cereb Cortex. 2012 Jan;22(1):232-42
21653286
Lancet. 1999 Mar 27;353(9158):1057-61
10199354
Hippocampus. 2003;13(5):572-86
12921348
Neuroimage. 2006 Aug 15;32(2):747-60
16797190
J Cogn Neurosci. 2009 Oct;21(10):2007-18
19296728
Magn Reson Imaging. 2009 Feb;27(2):163-75
18687552
J Cogn Neurosci. 2010 Jul;22(7):1530-40
19642890
Cereb Cortex. 2012 Nov;22(11):2643-52
22166764
Neurology. 2002 Dec 24;59(12):1950-5
12499489
PLoS One. 2012;7(11):e50425
23185621
Neuroreport. 1997 Nov 10;8(16):3479-83
9427311
Neuroimage. 2011 Jan 1;54(1):577-93
20656040
Neurology. 2010 Jul 13;75(2):168-76
20625170
Neuroimage. 2011 Sep 15;58(2):656-64
21722742
Trends Cogn Sci. 2009 Apr;13(4):175-81
19223226
Cognition. 2004 May-Jun;92(1-2):1-12
15037124
J Magn Reson Imaging. 2009 Jan;29(1):23-30
19097099
Gerontology. 2014;60(1):3-9
24080587
Brain Inj. 2011;25(12):1170-87
21932994
Proc Natl Acad Sci U S A. 2013 Oct 8;110(41):16402-7
24062469
Neuroimage. 1997 Oct;6(3):218-29
9344826
Cereb Cortex. 2008 Nov;18(11):2471-82
18281301
J Cogn Neurosci. 2011 Sep;23(9):2171-85
20954936
J Neurosci. 2009 Jan 7;29(1):43-51
19129383
Psychol Aging. 1999 Sep;14(3):365-79
10509693
PLoS One. 2011;6(6):e20726
21695183
Biol Res. 1992;25(2):51-61
1365702
AJNR Am J Neuroradiol. 2001 Jan;22(1):136-42
11158899
Ann N Y Acad Sci. 2008 Mar;1124:127-44
18400928
Curr Opin Neurobiol. 2013 Apr;23(2):250-4
23146876
J Cogn Neurosci. 2012 Nov;24(11):2135-46
22849403
J Int Neuropsychol Soc. 2010 Sep;16(5):754-60
20673381
Front Neurosci. 2011 Mar 21;5:38
21519384
PLoS One. 2011 Jan 07;6(1):e14496
21249127
Neuroimage. 2011 Aug 1;57(3):1103-15
21392583
Neurobiol Aging. 2008 Mar;29(3):436-51
17147975
Brain. 2011 Oct;134(Pt 10):3071-82
21975590
Hum Brain Mapp. 2014 Jan;35(1):319-30
22915491
Cereb Cortex. 2010 Feb;20(2):352-64
19505991
Neuroimage. 2003 Jun;19(2 Pt 1):466-70
12814595
Ann Neurol. 2005 Jan;57(1):8-16
15597383
Biol Psychol. 2009 Apr;81(1):14-23
19428964
Funct Neurol. 1987 Apr-Jun;2(2):189-94
3666548
Front Evol Neurosci. 2012 Jul 03;4:9
22783188
Physiol Rev. 2011 Oct;91(4):1357-92
22013214
Neuropsychologia. 1971 Mar;9(1):97-113
5146491
Front Psychol. 2013 Jul 12;4:416
23874313
Psychol Aging. 2002 Mar;17(1):85-100
11931290
Science. 2014 Oct 31;346(6209):583-7
25359966
Cereb Cortex. 2010 Mar;20(3):549-60
19546155
Nat Rev Neurosci. 2007 Sep;8(9):700-11
17704812
Neuroimage. 2005 Jul 1;26(3):839-51
15955494
Brain. 2010 Nov;133(11):3396-408
20870779
Brain Res. 2012 Jan 30;1435:130-45
22197699
Ann N Y Acad Sci. 2010 Mar;1191:62-88
20392276
Cereb Cortex. 2015 Apr;25(4):983-90
24152545
Brain Behav. 2016 Jul 27;6(9):e00495
27688934
Aging Dis. 2011 Jan 1;2(1):30-48
21461180
Proc Natl Acad Sci U S A. 2014 Nov 18;111(46):E4997-5006
25368199
Neuroimage. 2012 Mar;60(1):340-52
22178809
J Cogn Neurosci. 2007 Dec;19(12):2060-70
17892392