Fear of future uncertainties mapped on a specific brain region
Among 61 healthy participants who took part in the study, intolerance of uncertainty (IU) was positively correlated with striatal volume, particularly the putamen, and to a lesser extent the pallidum based on MRI and voxel-based morphometry [left: MNI (Montreal Neurologic Institute) space -21, 12, 6, t(55)=4.54, k=1,073 voxels; MNI space 22, 21 -8, t(55)=4.75, k=874 voxels; p<0.05]. [Emotion 2017, doi: 10.1037/emo0000331]
MRI data obtained from the participants were submitted for voxel-based morphometry. Images were first segmented into gray matter, white matter and cerebrospinal fluid. These images were then spatially aligned into standard MNI space. To acquire volume information for each voxel, gray and white matter images were modulated with determinants derived from nonlinear spatial alignment procedure.
Consistent with the initial results, hierarchical regression confirmed that adding IU scores in the second step significantly improved the model from the first step that included age, sex, intracranial volume, and trait anxiety, for the bilateral putamen [left putamen, first step: R2=0.217, F(4, 56)=3.883, p=0.007; second step: ∆R2=0.179, ∆F(1, 55)=16.267, p=0.00017] [right putamen, first step: R2=0.2, F(4, 56)=3.504, p=0.013; second step: ∆R2=0.144, ∆F(1, 55)= 12.03, p=0.001].
“Uncertainty and ambiguity of potential future threats are central to understanding the generation of anxiety and anxiety disorders,” said author Dr Justin Kim of Dartmouth College, Hanover, New Hampshire, US.
“In this study, we found no evidence for other gray matter structures or white matter tissue to be associated with IU… Our data also demonstrate that structural alterations of the striatum are linked to normal variations in a personality characteristic [elevated IU] that has ties with certain anxiety disorders such as obsessive compulsive disorder [OCD] or generalized anxiety disorder [GAD],” the authors wrote.
“Having a large striatal volume may be associated with how intolerant individuals are when facing an uncertain future. It can be observed in healthy individuals, and it does not mean that individuals with a large striatal volume have OCD or GAD,” the authors added.
Participants of the study were screened for past or current psychiatric illness using the Diagnostic and Statistical Manual of Mental Disorders IV (DSM IV) criteria for OCD and GAD, and had no current use or history of use of psychotropic medications.
Previous structural brain imaging studies examining gray matter volumes in patients with OCD and GAD have consistently found increased volume in the stratum, particularly the putamen. [Psychiatry Res 2015;234:314-320]