PSY4320 Research methods in cognitive neuroscience Preliminary results Lars T. Westlye, PhD Research Fellow Center for the Study of Human Cognition Department of Psychology, University of Oslo

1.Decreased P3a amplitude in the old compared to the young group 2.Decreased cortical thickness and FA in the old compared to the young group 3.Cortical thickness and FA positively correlated with amplitude in both groups 4.Spatial distribution and strenght of the relationships between vary between groups Hypotheses

Channel posititions F = frontal Z = central P = parietal O = occipital Cz

P3a

P3a amplitude P3a young old

P3a amplitude YoungOldp Cz20.9 (8.7)14.2 (7.7).002 Amplitude significantly stronger in the young than the old group Independent samples t-test

P3a amplitude Spatiotemporal distribution of the differences between young and old group (p3a) Increased frontal activation in old compared to young group FRONTAL SHIFT?

Female 25 years Female 74 years Young vs old

Cortical thickness Young Old General Linear Model testing the effect of group Thickness (vertex n ) = (young × β1) + (old × β2) + error H0: β1 = β2 (no difference between group) Mean young group Mean old group

Young Old Young > Old General Linear Model testing the effect of group Colored areas: p(β 1 = β 2 )< 5% (here we reject H0)

FA Red areas: reduced FA in old compared to young group

FA ~ 60 % of the skeleton voxels show a significant effect of group (young > old)

FA ~ 60 % of the skeleton voxels show a significant effect of group (young > old) Young Oldp FA0.49 (.02) 0.45 (0.01) <.001 Independent samples t-test

NB! Life-span changes in FA are not linear FA increases until ~30 years Y O

General Linear Model testing the effect of P3a amplitude on thickness within and between groups Thickness (vertex n ) = (young×β 1 ) + (old×β 2 ) + (ERP y × β 3 ) + (ERP o × β 4 ) + error Within groups: H0 1 : β 3 = 0 (no relation between amplitude and thickness in young group ) H0 2 : β 4 = 0 (no relation between amplitude and thickness in old group ) Between groups H0 3 : β 3 = β 4 (no difference between β 3 and β 4 ) Cortical thickness vs P3a amplitude

H0: β 3 = 0 (no relation between amplitude and thickness in young group ) Colored areas: the probability (p) of H0 < 5 % Young

Cortical thickness vs P3a amplitude H0: β 4 = 0 (no relation between amplitude and thickness in old group ) Colored areas: the probability (p) of H0 < 5 % Old

p(β 3 )=0p(β 4 )=0 Between groups H0 3 : β 3 = β 4 (no difference between the amplitude × thickness correlations between groups) Within groups youngold

p(β 3 = β 4 ) < 5% Red areas: thickness stronger related to amplitude in young than in old group

p(β 3 = β 4 ) < 5% Red areas: thickness stronger related to amplitude in young than in old group p(β 3 )=0 p(β 4 )=0

FA vs P3a amplitude in young group Green areas: negative correlation between amplitude and FA

FA vs P3a amplitude in young group β= -.67, p <.01

FA vs P3a amplitude in old group Red areas: negative correlation between amplitude and FA

FA vs P3a amplitude in old group β= -.71 p <.01

Low FA High FA Tract 1 Tract 2 Crossing fibres? How do we explain the negative correlations between amplitude and FA?

Radial diffusion Increased radial diffusion?

How do we explain the negative correlations between amplitude and FA? Radial diffusion Along Perpendicular Positive correlation between radial diffusion and P3a amplitude Increased axonal calibre/diameter?

FA/thickness: Young > old P3a positively correlated with thickness Summary P3a negatively correlated with FA P3a positively correlated with radial diffusion YoungOld Young vs old OldYoung

Q: How could we improve the study?

The inverse problem Theoretical source 1 Theoretical source 2 Scalp electrodes Scalp EEG Question: How do you separate signals from the various sources?

Task #2 Correlate MRI brain structural measures (cortical thickness, diffusion tensor imaging) with ERP parameters between and across groups A) How do the different measures change with age? B) Are the relationships between MRI and ERP different between groups? Research questions

Inter-trial variability

Female 25 years Female 74 years Young vs old

Does the same pattern emerge when comparing groups of subjects? -- Young participants -- Old participants

Task #1 Compare peak amplitude and latency between two groups: Group A: young (n=30, years) Group B: old (n=30, years) Course research assignments