Left-Brain/Right-Brain Differences Found in People with Autism

Coupled with pre­vi­ous stud­ies, find­ings sug­gest treat­ments for autism

Using func­tion­al mag­net­ic res­o­nance imag­ing (fMRI) scans, a team of sci­en­tists at Carnegie Mel­lon Uni­ver­si­ty and the Uni­ver­si­ty of Pitts­burgh have found dif­fer­ences in the acti­va­tion and syn­chro­niza­tion of brain net­works between peo­ple with autism and those with­out it. These find­ings could yield strate­gies for treat­ing autism, a mys­te­ri­ous brain dis­or­der that impairs ver­bal and non-ver­bal com­mu­ni­ca­tions and social inter­ac­tions. The study will be pub­lished in the jour­nal Neu­roim­age and will be avail­able online Novem­ber 29 at www.sciencedirect.com.

The research was con­duct­ed at Carnegie Mel­lon’s Cen­ter for Cog­ni­tive Brain Imag­ing (CCBI) and was co-authored by Mar­cel Just, direc­tor of the cen­ter and the D.O. Hebb Pro­fes­sor of Psy­chol­o­gy at Carnegie Mel­lon. The lead author was Hideya Koshi­no, an assis­tant pro­fes­sor of psy­chol­o­gy at Cal­i­for­nia State Uni­ver­si­ty at San Bernardi­no and a for­mer post­doc­tor­al fel­low at the CCBI.

The study fol­lows on the heels of ground­break­ing research pub­lished by the CCBI in July that pro­posed the under­con­nec­tiv­i­ty the­o­ry, which holds that autism is a sys­tem-wide brain dis­or­der that lim­its the coor­di­na­tion and inte­gra­tion among brain areas. Because this type of coor­di­na­tion is crit­i­cal to com­plex think­ing and social inter­ac­tion, a wide range of behav­iors are affect­ed in autism.

The cur­rent study com­pared a group of high-func­tion­ing adults with autism to a con­trol group of nor­mal par­tic­i­pants with sim­i­lar ages and IQs. Each par­tic­i­pant saw a series of alpha­bet let­ters pre­sent­ed one at a time at the cen­ter of a com­put­er screen, and they had to decide if the let­ter was the same as the pre­vi­ous let­ter, or in some cas­es, whether it was the same as the let­ter that was pre­sent­ed two let­ters previously.

Although the two groups per­formed the task equal­ly well, the fMRI scans revealed three impor­tant dif­fer­ences in brain acti­va­tion between them. First, the autism group showed more acti­va­tion in the right hemi­sphere of the brain than the left, where­as the con­trol group showed more acti­va­tion in the left hemi­sphere than the right. The left hemi­sphere usu­al­ly is asso­ci­at­ed with pro­cess­ing ver­bal infor­ma­tion and the right hemi­sphere is asso­ci­at­ed with visu­al and spa­tial infor­ma­tion pro­cess­ing. Since let­ters can be inter­pret­ed as ver­bal codes (let­ter names) or visu­al codes (let­ter shapes), the dif­fer­ent uses of two hemi­spheres seem to cor­re­spond to a dif­fer­ence in strate­gies: The autism group like­ly remem­bered let­ters by their shape, while the con­trol group remem­bered let­ter names.

A sec­ond dif­fer­ence was that the autism group showed less acti­va­tion in the ante­ri­or parts (pre­frontal regions) of the brain and more acti­va­tion in the pos­te­ri­or parts than the con­trol group. Work­ing mem­o­ry is usu­al­ly asso­ci­at­ed with the pre­frontal regions of the brain, and the con­trol group showed a typ­i­cal pat­tern of acti­va­tion in the pre­frontal regions, where­as the autism group showed weak­er acti­va­tion in the pre­frontal regions. This pat­tern is con­sis­tent with pre­vi­ous find­ings in which peo­ple with autism group showed more acti­va­tion in the pos­te­ri­or lan­guage area (Wer­nick­e’s area) than the ante­ri­or lan­guage area (Bro­ca’s area) dur­ing sen­tence comprehension.

The third dif­fer­ence was that the over­all syn­chro­niza­tion among the brain regions was weak­er for the autism group than for the con­trol group. The acti­vat­ed brain areas were also not as tight­ly orga­nized into groups with sim­i­lar syn­chro­niza­tion in the case of the peo­ple with autism. The results were con­sis­tent with the under­con­nec­tiv­i­ty the­o­ry. Tak­en togeth­er, the results of these and oth­er autism stud­ies sug­gest that pos­si­ble treat­ments of autism might include instruc­tion and train­ing that focus­es on the inte­gra­tion of the types of pro­cess­ing per­formed by dif­fer­ent brain areas.

(Post­ed because I know a few of my friends are inter­est­ed in the subject.)