Hi,
following the recent discussion on neuroanatomical connectivity data on the
SPM list, several people have inquired about the status of CoCoMac. Since
questions of anatomical connectivity seem to be of interest for many
neuroimaging people, I thought that I should maybe summarise my replies in
an e-mail to the list.
As Narender had kindly pointed out in previous e-mail, CoCoMac (standing
for "Collation of Connectivity in the Macaque") is a database of primate
connectivity data from published neuroanatomical tract tracing
studies. Those of you who have visited CoCoMac on the web
(www.cocomac.org) may have been disappointed to find out that the web site
currently only provides information on CoCoMac but that the database as
such is not accessible online yet. We are currently working hard to set up
an online interface to CoCoMac which will allow any researcher who is
interested in connectivity data to freely access CoCoMac, browse its
contents, download data from it in XML format, and use these data within
other software packages (possibly also within SPM in the future).
To prevent any disappointments or misunderstandings, I would like to
briefly summarise what you can and what you cannot expect from the CoCoMac
database when it will be online:
1. CoCoMac only contains monkey data - and thus it does NOT allow you to
make any direct inferences on human brain connectivity straight away. As
Geraint had already pointed out, the question of homology between man and
monkey is a difficult one and has not been answered yet for most cortical
areas. This problem is complicated by different concepts of homology
applied by different researchers and a large variety of different
parcellation schemes that have been defined for basically any cortical or
subcortical brain region. Is there any way how can we use monkey
connectivity data for human neuroimaging studies, in spite of the
unresolved problem of homology? At the moment, there only seem to be two
reasonable alternatives:
(A) restrict the transfer of connectivity data to those areas which have
been sufficiently well characterised by anatomical and functional studies
in both species so that there is a reasonable basis for the assumption that
two given areas in the two species may have an equivalent functional role
within the two brains. This seems to be more easily feasible for
"hierarchically lower" areas processing sensory input (for example, visual,
auditory, and somatosensory areas) and more complicated for "hierarchically
higher" / "association" areas (but see Petrides & Pandya 1999, Eur J
Neurosci 11:1011-1136, who have tried to establish equivalencies between
human and Macaque prefrontal areas on the basis of anatomical criteria).
(B) refrain from transferring monkey connectivity data to the human brain
on an area-to-area basis, and diminish the resolution of the data by only
looking at the connectivity between larger cortical regions (i.e. instead
of asking "is there a connection from area PG to area F4" it is spatially
less precise but also less error-prone to ask "is there a connection from
inferior posterior parietal cortex to inferior lateral premotor
cortex?"). For the future, we plan to offer a so-called "regional map"
within CoCoMac which is intended to help with this kind of strategy.
Whatever the strategy chosen, one should never forget that, in most cases,
the transfer of monkey data to the human brain is based on assumptions with
different degrees of validity. This uncertainty should remind us to be
cautious when interpreting analyses of human neuroimaging data that were
constrained by monkey connectivity data. Maybe most importantly, bear in
mind that it can be misleading to infer connections in the human brain from
monkey data solely on the basis of identical area names. Even within one
species such an inference should not be made without good knowledge of the
literature since the many diverging parcellation schemes quite often use
identical abbreviations for areas that are actually quite different.
Until new technologies are able to provide us with reliable and precise
information on human brain connectivity, however, there does not seem to be
a good alternative to using monkey data. For the future, diffusion tensor
imaging (DTI) looks like a promising method, but it does not have an
adequate resolution yet and, because diffusion occurs bidirectionally along
axons, it will probably never be able to indicate whether a given
connection is unidirectional or reciprocal.
2. CoCoMac does NOT contain information on the precise topographical
location within the brain. Instead, we use a variety of codings to
describe various features of connectivity data delivered by tract tracing
studies (including injected and labelled brain sites, relative spatial
extent of label, density of the labelling, laminar patterns of the
labelling, and quantitative data like absolute numbers of labelled neurons).
3. In addition to connectivity data, CoCoMac offers information on tract
tracing methodology, the definitions of the various brain maps used by
different authors, and on the logical relations between these maps.
4. CoCoMac both offers to browse the "raw" data as described in the
original articles as well as data sets that result from integrating and
analysing data from several articles whose data have been algorithmically
transformed to a single brain map.
We hope that a beta-version of this interface will be ready by
January/February 2002. I will send a note to the SPM list as soon as the
interface is online so that everyone can check whether CoCoMac is a useful
tool for her/him (maybe consider switching to monkey fMRI... ;-).
Best wishes,
Klaas
At 18:41 28.11.01 +0000, n.ramnani wrote:
>Mark,
>
>There is an excellent anatomical resource you might wish to access. It is a
>database called COCOMAC (www.cocomac.org) which systematically organizes
>connectivity data from an extremely large number of macaque monkey anatomy
>studies.
>
>You might also wish to refer to a couple of key articles by the authors of
>this database...
>
>Stephan KE, Kamper L, Bozkurt A, Burns GA, Young MP, Kotter R.
>
>Advanced database methodology for the Collation of Connectivity data on the
>Macaque brain (CoCoMac).
>Philos Trans R Soc Lond B Biol Sci. 2001 Aug 29;356(1412):1159-86.
>
>Stephan KE, Zilles K, Kotter R. Related Articles
>
>Coordinate-independent mapping of structural and functional data by
>objective relational transformation (ORT).
>Philos Trans R Soc Lond B Biol Sci. 2000 Jan 29;355(1393):37-54.
>
>I hope you find this useful.
>
>Best wishes,
>
>Narender
>
>
>
>At 15:22 28/11/2001 +0000, you wrote:
>>Hi,
>>
>>I am doing an SPM analysis looking for brain regions that are
>>functionally connected to areas activated in a previous analysis. I have
>>some "blobs" generated by SPM that are showing consistent associations
>>accross different contrasts and analyses. What I would like to do now is
>>to go back to the brain structure and see if these associations make
>>"structural sense".
>>
>>Can anyone recommend a good source of information (book, article,
>>website) on cortico-cortical connections at the level of structural
>>neuroanatomy?
>>
>>Many thanks in advance,
>>
>>Mark
>
>********************************************************************
>Dr Narender Ramnani
>
>Sensorimotor Control Group
>Department of Physiology
>University of Oxford
>Parks Road
>Oxford OX1 3TP
>UK
>
>Oxford University Centre for
>Functional Magnetic Resonance Imaging of the Brain,
>John Radcliffe Hospital,
>Headington,
>Oxford OX3 9DU
>UK
>
>Tel. 01865 222704 (Direct)
>01865 222729 (Admin)
>mob. 0771 2632785
>Fax. 01865 222717
>email [log in to unmask]
>
>*******************************************************************
________________________________________________
Klaas Enno Stephan
Institute for Medicine (IME), Cognitive Neurology Group
Research Centre Juelich, Germany
phone +49-(0)2461-61-4007 / fax +49-(0)2461-61-2820
[log in to unmask] / [log in to unmask]
http://www.hirn.uni-duesseldorf.de/~klaas/
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