22 March 2021
Using CANTAB to investigate specific contributions from the volume of hippocampal subregions to visuospatial memory tasks
We recently caught up with Tamara Shavitt, a psychology student who conducted research at the Faculty of Medicine, University of São Paulo to discuss how CANTAB impacted her research: investigate specific contributions from the volume of hippocampal subregions to visuospatial memory tasks.
Tell us a little about yourself?
As an undergraduate student in Psychology aiming to learn more about neuroscience and cognition, I have joined a program at the Institute of Psychiatry, Hospital das Clínicas da Universidade de Sao Paulo (Faculty of Medicine, University of São Paulo, Brazil) designed for undergraduate students interested in scientific projects. With the aim of studying memory and the relevance of this executive function in everyday life, we have submitted and obtained an “introduction to science” one-year research grant (aimed at young researchers who are initiating their academic life and work) to carry out research in this field.
Can you provide some background to the study?
It has long been known about the participation of the hippocampus in mnemic processes. Research in this area goes back to the patient H.M, one of the first cases to highlight the importance of the hippocampus in the formation of new episodic memories. Work with H.M. and subsequent studies paved the way for further exploration of the brain networks encoding fundamental principles about how memory functions are organized.
Therefore, the present study was based on a previous series of studies conducted in London with taxi drivers that investigated the relationship between visuospatial memory and hippocampal volume using magnetic resonance imaging (MRI) (Maguire et al., 2000; Maguire et al., 2003; Maguire, Nannery and Spiers, 2006;). In general, the results indicated greater hippocampal volume (bilaterally) in taxi drivers in comparison to healthy controls, since taxi drivers experience extensive memory training (Maguire et al., 2000).
From that, we considered that it would be interesting to replicate these findings in healthy controls, to evaluate whether there would be a relationship between the volume of the bilateral hippocampal formation (particularly the right hippocampus) and the performance in visuospatial memory tasks, while accounting for covariates, such as age and IQ.
What about the methods used and why?
Thirty-one healthy individuals were assessed by the Rey-Osterrieth Complex Figure test and four CANTAB memory tests: 1) Spatial Span (SSP); 2) Delayed Matching to Sample (DMS), and 3) Spatial Recognition Memory (SRM). SSP is analogous to the Corsi block-tapping subtest from the Wechsler Memory Scale, and assesses visuospatial working memory capacity. DMS, a test in which the participant should identify the figure that exactly matches the model, assesses both simultaneous: visual matching ability and short-term visual recognition memory. Finally, SRM is a test that assesses visual pattern recognition memory in a 2-choice forced discrimination paradigm.
The results on these tests were grouped in a composite score (since CANTAB offered a great variety of output variables from each test, an exploratory factorial analysis could be made in order to investigate the set of variables that were precisely related to visuospatial memory), which was entered as a dependent variable in a linear regression model using the hippocampal formation volumes (obtained from a structural T1 image from a 3T Phillips MRI scan) as independent variables.
Why did you choose CANTAB for your study?
Our study aimed not only to replicate the findings of the previous studies conducted with the taxi drivers but also to introduce methodological innovations in the field. The hippocampal segmentation automatically performed in the Freesurfer software is an example, since the division into its subregions provides more precise and specific measures. Besides, another relevant novelty was to use computerized memory tests not used previously, like those offered by CANTAB. Therefore, we chose CANTAB because it represented a new and innovative technique to be used in the study, and also because it provides an accurate and reliable system, with a robust and wide battery that includes a great range of tests.
Can you summarize your findings and their implications?
We found significant associations between the hippocampal subregions of the left hemisphere, (more specifically the granular cells of the molecular layer of the dentate gyrus and CA4) and the performance in visuospatial memory tasks. When the IQ was entered as a covariate, we also found significant results for the right hemisphere, although no specific subregion contributed to predicting the visuospatial memory index. Interpreting the results, we concluded that the bilateral hippocampal formations contribute to the performance of memory tasks, although more specific functions may be different depending on laterality. We could also conclude that visuospatial memory processing is essential for a diverse set of daily activities and may be influenced by demographic variables in healthy subjects.
What future areas of investigation could follow your research?
Since this study was conducted only with healthy subjects, it would be interesting to conduct a similar study with patients suffering from a variety of conditions characterized by memory impairment or with hippocampal lesions (or even hippocampal atrophy, as in Alzheimer’s disease) to further investigate the association between the volume of hippocampal subregions and performance in memory tasks in specific disorders (especially those in which non-verbal memory deficits have been already implicated).
Is there anything else you'd like to share?
I just wanted to emphasize the importance, for undergraduate students, to take part in research projects like this one – it may be challenging, but it is certainly rewarding and a great opportunity for personal and academic growth.
1. Maguire EA, Gadian DG, Johnsrude IS, Good CD, Ashburner J, Frackowiak RS, et al. Navigation-related structural change in the hippocampi of taxi drivers. Proc Natl Acad Sci USA 2000; 97: 4398–4403, doi: 10.1073/pnas.070039597.
2. Maguire EA, Nannery R, Spiers HJ. Navigation around London by a taxi driver with bilateral hippocampal lesions. Brain 2006; 2894–2907, doi: 10.1093/brain/awl286.
3. Maguire EA, Spiers HJ, Good CD, Hartley T, Frackowiak RSJ, Burgess N. Navigation expertise and the human hippocampus: a structural brain imaging analysis. Hippocampus 2003; 13: 250–259, doi: 10.1002/hipo.10087.
Tamara Shavitt - Faculty of Medicine, University of São Paulo, Brazil