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Cortical Thickness

4 studies

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Cortical thickness is a structural neuroimaging metric that measures the distance between the inner white matter boundary and the outer pial surface of the cerebral cortex. Measured using high-resolution structural MRI, it provides an estimate of the local density and spatial organization of gray matter.

Understanding cortical thickness is crucial because it serves as a sensitive biomarker for both healthy neurodevelopment, such as synaptic pruning during adolescence, and neurodegenerative processes. Undergraduates will encounter this metric when analyzing cognitive decline, aging trajectories, and clinical diagnostics in disorders like Parkinson's disease.

Studies

4

Findings

5

6 supporting · 0 challenging · 0 qualifying citations

Open tensions

0

Currently

What we know

  1. Healthy adolescent development from late childhood through early adulthood is characterized by a widespread, continuous decrease in both cortical volume and cortical thickness.
  2. Cortical thinning, rather than changes in surface area, is the primary developmental driver behind the overall reduction of cerebral cortical volume during adolescence.
  3. There is substantial inter-individual variability in the timing, speed, and direction of cortical thickness changes during the transition from late childhood to young adulthood.
  4. In newly diagnosed Parkinson's disease, patients with mild cognitive impairment show accelerated, widespread cortical thinning in frontal, temporal, parietal, and occipital regions over 18 months compared to patients with normal cognition.
  5. Functional network alterations, such as default mode network hyperconnectivity in Parkinson's patients with visual hallucinations, can exist independently without any detectable loss in cortical thickness.

Procedure

How it works

The main stages of the method. Specific protocols and analysis choices vary between studies.

  1. Acquire a high-resolution T1 volume

    A structural MRI with good grey–white contrast is required before surfaces can be placed. Motion, bias field, and field strength all affect how sharp those boundaries look.

  2. Find white-matter and pial surfaces

    Automated segmentation places an inner surface at the grey–white interface and an outer surface at the pial boundary. Errors concentrate where cortex is thin, folded, or lesioned; those errors become millimeters of 'thickness.'

  3. Measure the distance between surfaces

    Thickness at each cortical location is the distance between the two surfaces. It is a geometric estimate of local cortical width, not a cell count, synapse count, or myelin stain.

  4. Register to a common cortical surface

    Individual maps are aligned using folding patterns so group statistics can be computed vertex-wise. Misregistration of sulci can look like a thickness difference.

  5. Compare thickness, not function

    Thinning or thickening is a structural contrast. It does not establish that a clinical symptom requires tissue loss, and group-average adolescent thinning does not mean every individual follows the same trajectory.

Common misconceptions

  • Reductions in cortical volume during adolescent development are primarily caused by a shrinking of the brain's outer surface area.

    Longitudinal MRI data demonstrates that the loss of cortical volume is driven overwhelmingly by cortical thinning, whereas surface area changes play a significantly smaller role.

  • All adolescents undergo identical, uniform rates of cortical thinning as they mature.

    While group-level averages show overall declines, individuals exhibit highly distinct developmental trajectories, with differences in rate, timing, and biological factors like sex and initial brain size.

  • Severe cognitive and perceptual clinical symptoms, like visual hallucinations, require underlying structural tissue loss or cortical thinning.

    Subtle or early pathological states can manifest as functional network hyperconnectivity in key networks even in the absence of any statistically detectable thinning of the cortex.

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