Wednesday, January 10, 2007

How thick is your cortex?

Morton Ann Gernsbacher is President of the Association for Psychological Science this year, and she's been giving autism a high profile in many of her monthly columns in the APS Observer. You can find two previous examples here and here.

Her latest illuminates a series of results in a trendy area of science, particularly in autism research. That's the measurement of cortical thickness. There have been several published papers, and surely more will come, asserting that autistics' cortices aren't the right thickness at all.

Dr Gernsbacher has put together a big heap of findings about thick and thin cortices, complete with how they've been interpreted. She seems to have done some work on effect sizes too. Now whose cortex is too thick, too thin, or just right?

Excerpting Dr Gernsbacher's latest column isn't fair to it. It's a classic. You have to go here and read the whole thing.

5 comments:

notmercury said...

I'll go read it now. I saw something the other day that I mean to track down. Something about cortical thickening during development and IQ.

Michelle Dawson said...

Hi notmercury,

That paper might be Shaw et al. (2006), which was published in Nature last year. You can find the abstract here. I have the pdf plus supplementary info, if you want it.

notmercury said...

Thanks Michelle,
I think that's it though I read a lay-speak article about it.

Is there anything that can be used to compare the cortical plasticity discussed here in the context of early development in autistic children?

Michelle Dawson said...

Hi again notmercury,

You asked, "Is there anything that can be used to compare the cortical plasticity discussed here in the context of early development in autistic children?"

There's nothing longitudinal that's been published, and none of the existing papers involves any children younger than 8, but here's the abstract of a paper that was presented at IMFAR 2006:

------------------------------------

CORTICAL THICKNESS IN AUTISM: A LONGITUDINAL MRI STUDY Antonio Y
Hardan, Rahul Bansal, Jeff Nutche, Matcheri S Keshavan, Nancy J Minshew, University of
Pittsburgh
Background: Increase in several brain structures including total brain volume have consistently
been reported in autism. Increase in grey matter volume has also been described but it remains
unclear whether this enlargement is related to an increase of cortical thickness, surface area or
both.
Objectives: The goal of this investigation is to examine in a longitudinal design cortical
abnormalities including cortical thickness in children with autism
Method: Total and lobar cortical grey matter cortical thickness were measured using MRI scans
acquired from 18 male children with autism and 22 age- and gender-matched normal healthy
controls. Measurements of sulcal and gyral thickness were also obtained. Nineteen individuals (9 with autism and 10 controls) had, to date, their imaging studies repeated 30 months after their
baseline scans and measurements were also conducted on this sample.
Results: Increased total cerebral gyral and sulcal thickness were observed in children with autism
when compared with controls. Similar findings were found in the temporal, and parietal lobes but not in the frontal and occipital. Results remained unchanged after controlling for total brain
volume. At follow-up, preliminary analysis indicates an increase in cortical thickness in the
autistic group when compared to controls, but without reaching statistical significance.
Conclusions: While the exact pathophysiology and developmental trajectory of increased brain
size in autism remains unclear, preliminary evidence from this study indicate that increased
cortical thickness may contribute to the increased grey matter volume and total brain size observed in children with autism and may also underlie anomalies in cortical connectivity.

------------------------------------

I'm afraid I can't remember the ages of the autistics in this study (in Hardan et al., 2006, an ealier published paper, they were between 8 and 12yrs). Shaw's paper (the 2006 Nature paper) included 307 participants whose ages (at first scan) ranged from 3.8yrs to 25.4yrs...

Ms. Clark said...

I haven't read it yet, but I suspect Dr. Gernsbacher's cortical thickness is just right. :-) Even if it's "too thick or too thin".