In 2017, more than sixteen journal articles have been published, featuring the keywords: ‘agenesis of the corpus callosum.’ New data is being generated as years of research come to fruition and as new technology allows researchers to revisit unanswered questions. Groups like the International Research Consortium for the Corpus Callosum and Cerebral Connectivity (IRC⁵) allow researchers across the world to share data via the internet. Interesting case studies published this year have involved young children and the elderly alike. Examples of areas investigated include visual and time perception and cognitive skills.

A new study released recently by Siffredi at al (2017), used fMRI (functional Magnetic Resonance Imaging) to explore how ‘working memory’ may retain information on a short- term basis, while there are other distracting stimuli. Nine children with agenesis of the corpus callosum (AgCC) were compared with a group of sixteen neurotypical children. The significance of this study was that this kind of investigation had not previously been performed on children with AgCC. In neurotypical children, working memory is associated with development of the anterior corpus callosum. In brain-injured children, loss of integrity of the corpus callosum is associated with a difference in verbal and visuospatial working memory. This idea has been explored in case studies with adults with AgCC, but not groups and not children and the results in these case studies differed from one another.

The working memory processes tested were ‘encoding,’ ‘maintenance,’ and ‘retrieval.’  These processes involve different parts of the brain and different parts of the corpus callosum. Bilateral activation of these areas of the brain was seen in both groups, however the AgCC group did underperform in some specific areas. The supramarginal gyrus was seen to be less activated when involved with verbal tasks, among other things. This may indicate the process is less efficient in those with AgCC. The fusiform gyrus was seen to be less activated in facial processing tasks. This part of the brain has a role in facial recognition. The AgCC group demonstrated a different cognitive strategy for processing multiple stimuli at once.

To assess working memory capacity the children were asked to repeat backwards, a sequence of numbers they heard. The participants were given letters to remember in a sequence, 1 letter per second (encoding), a delay where they were given visual or verbal stimulus for 6 seconds (maintenance). The participant had 3 seconds to recall the position of a single uppercase letter in the sequence (retrieval). During the maintenance period, the task was to decide whether a string of letters was an actual word or whether an image was a real face. Participants were required to press either a red or green button to record their response. This process was then repeated multiple times for each participant.

Participants with AgCC appeared to be less able to use lateralised brain systems in encoding and retrieval. There also appeared to be a greater degree of conflict between verbal stimulus and visual stimulus, in that maintenance period, compared with the control group

 

So as memory processes are highly lateralised, children with AgCC appear more susceptible to distractor stimulus and have different cognitive pathways for dealing with processing information. As in most AgCC studies, there were limitations in the number of participants. This study has implications for how we might think about memory and learning in children with AgCC and will be a stepping stone to larger studies and broader implications.

Reference:

Siffredi, V., Spencer-Smith, M., Barrouillet, Vaessen, M., Leventer, R., Anderson V., & Vuilleumier P (2017). Neural correlates of working memory in children and adolescents with agenesis of the corpus callosum: an fMRI study. Neuropsychologia DOI 10.1016/j.neuropsychologia.2017.09.008

If you have any research questions or any requests for searches of the literature, I can be contacted on twitter via AusDoCC:

info@ausdocc.org.au Please mark it ‘ATTN Michael Shanahan’

or my page AusDoCC: Disorders of the Corpus Callosum Research Findings at https://www.facebook.com/DCCresearch/

More information about the IRC⁵ can be found at https://irc5.qbi.uq.edu.au

You can also check out AusDoCC member and mum of a child with AgCC, Pieta Shakes’s DCC blog: https://disordersofthecorpuscallosum.com

Michael Shanahan – AusDoCC Committee member

About Michael:

Michael has partial ACC and works as a registered nurse. He is studying for his Masters and hopes to focus his thesis on ACC. His role as an AusDoCC committee member is to keep track of and disseminate corpus callosum research findings and to promote participation in research projects, particularly at the Queensland Brain Institute (QBI) and the Murdoch Children’s Research Institute (MCRI).