SelfOrganising Networks for Classification Learning from Normal and
Aphasic Speech

Sheila Garfield, Mark Elshaw and Stefan Wermter
University of Sunderland
Informatics Centre, SCET
St. Peter's Way
Sunderland SR6 0DD, United Kingdom
Email: Stefan.Wermter@sunderland.ac.uk
Phone: +44 191 515 3279
Fax: +44 191 515 3553

Abstract
An understanding of language processing in humans is
critical if realistic computerised systems are to be produced 
to perform various language operations. The examination 
of aphasia in individuals has provided a large
amount of information on the organisation of language
processing, with particular reference to the regions in the
brain where processing occurs and the ability to regain
language functionality despite damage to the brain. Given
the importance played by aphasic studies an approach that
can distinguish between aphasic forms was devised by
using a Kohonen selforganising network to classify sentences 
from the CAP (Comparative Aphasia Project) Corpus. 
We demonstrate that the different distributions of
words in aphasics types may lead to grammatical systems
which inhabit different areas in selforganising maps.


References
Anderson, B. Kohonen neural networks and language.
Brain and Language, 70:86--94, 1999.
Basso, A., Gardelli, M., Grassi, M. & Mariotti, M. The
role of the right hemisphere in recovery from aphasia:
Two case studies. Cortex, 25:555--566, 1989.
Bates, E., Friederici, A. & Wulfeck, B. Grammatical
morphology in aphasia: Evidence from three languages. 
Cortex 23:545--574, 1987a.
Bates, E., Friederici, A. & Wulfeck, B. Sentence comprehension 
in aphasia: A crosslinguistic study. Brain
and Language, 32:19--67, 1987b.
Binder, J., & Frost, J., Hammeke, T., Cox, R., Rao, S.
& Prieto, T. Human brain language areas identified by
functional magnetic resonance images. The Journal of
Neuroscience, 17(1):280--288, 1997.
Brendt, R. & Caramazza, A. How regular is sentence
comprehension in broca's aphasia? it depends on
how you select the patients. Brain and Language,
64(2):231--256, 1999.
Capp, S., Perani, D., Grassi, F., Bressi, S., Alberoni, M.,
Franceschi, M., Bettinardi, V., Todde, S. & Frazio,
F. A PET Followup Study of Recovery after Stroke
in Acute Aphasics. Brain and Language, 56:55--67,
1997.
Chen, S. & Bates, E. The dissociation between nouns
and verbs in Broca's and Wernicke's aphasia: Findings
from Chinese. Aphasiology, 12(1):5--36, 1998.
Dodel, S., Hermann, J. & Geisel, T. Stimulus
independent data analysis of fMRI data. In Wermter,
S., Austin, J. & Willshaw, D., editors, EmerNet: International 
Workshop on Emergent Neural Computa
tional Architectures Based on Neuroscience, pages 7--
10. EmerNet, 1999.
Elman J. Finding structures in time. Cognitive Science,
14:179--211, 1990.
Grodzinsky, Y., Pinango, M., Zurif, E. and Drai, D.
The Critical Role of Group Studies in Neuropsychol
ogy: Comprehension Regularities in Broca's Aphasia,
Brain and Language, 67:134--147, 1999.
Hartsuiker, R. & Kolk, H. Syntactic Facilitation in
agrammatic sentences production. Brain and Language, 62:221--254, 1998.
HechtNielsen, R. Neurocomputing. Addison Wesley,
Reading MA, 1990.
Karbe, H., Thiel, A., WeberLuxenburger, G., Herholz,
K. & Heiss, W. Brain plasticity in poststroke aphasia: 
What is the contribution of the right hemisphere?
Brain and Language, 64:215--230, 1998.
Kohonen, T. SelfOrganizing Maps. Springer Verlag,
Heidelberg, 1997.
Marshall, J., Pring, T. & Chait, S. Verb Retrieval and
Sentence Production in Aphasia. Brain and Language,
63(2):159--183, 1998.
Mimura, M., Kato, M., Kato, M., Santo, Y., Kojima, T.
and Naeser, M. and Kashima, T. Prospective and Retrospective 
Studies of Recovery in Aphasia: Changes
in Cerebral Blood Flow and Language Functions.
Brain, 121: 2083--2094, 1998.
Papke, K., Hellmann, T., Renger, B., Morgenroth, C.,
Knecht, S., Schuierer, G. & Reimer, P. Clinical applications 
of functional MRI at 1.0 t: motor and language
studies in healthy subjects and patients. European Radiology, 9(2):211--220, 1999.
Raichle, M., Fiez, J., Videen, T., MacLeod, A., Pardo, J.,
Fox, P. & Petersen, S. Practicerelated changes in human 
brain functionalanatomy during nonmotor learning. Cerebral Cortex, 4(1):34--54, 1994.
Reggia, J., Shkuro, Y. & Shevtsova, N. Emergent 
Specialization in Cerebral Regional Modules. In Wermter,
S., Austin, J. & Willshaw, D., editors, Proceedings of
the Third International Workshop on Computational
Architectures Intergrating Neural Networks and Neuroscience, 
pages 11--14. EmerNet, 2000.
Reilly, R. Collaborative cell assemblies: Building blocks
of cortical computation. In Wermter, S., Austin, J. &
Willshaw, D., editors, In Emergent Neural Computational 
Architectures based on Neuroscience, Springer
Verlag, Heidelberg, Germany, 2001.
Shaywitz, B., Shaywitz, S., Pugh, K., Constable, R.,
Skudlarski, P., Fulbright, R., Bronen, R., Fletcher, J.,
Shankweiler, D., Katz, L. & Gore, J. Sex differences in
the functional organisation of the brain for language.
Nature, 373(6515):607--609, 1995.
Spitzer, M. The Mind Within the Net: Models of Learning, 
Thinking and Acting. MIT Press, Cambridge,
MA, 1999.
Taylor, J. Images of the mind: brain images and neural
networks. In Wermter, S., Austin, J. & Willshaw, D.,
editors, Proceedings of the International Workshop on
Emergent Neural Computational Architectures based
Neuroscience, pages 1--6. EmerNet, 1999.
Weiller, C., Isensee, C., Rijnties, M., Huber, W., Muller
S., Bier, D., Dutschka, K., Woods, P., Noth, J. &
Diener, C. Recovery from Wernicke's aphasia: A
positron emissions tomographic study. American Neurological 
Association, 37(6):723--732, 1995.
Wermter, S., Panchev, C. & Houlsby, J. Language disorders 
in the brain: Distinguishing aphasia forms with
recurrent networks. In AAAI99 Conference Workshop
on Neuroscience and Neural Computation, pages 93--
98, 1999.
Wermter S. & Meurer M. Building Lexical Representations 
Dynamically Using Artificial Neural Networks.
Proceedings of the International Conference of the
Cognitive Science Society, pages 802--807, Stanford,
1997.
Wermter, S. and Sun, R. Hybrid Neural Systems
SpringerVerlag, Heidelberg, 2000.
Xiong, J., Rao, S., Gao, J., Woldorff, M. & Fox, P. Evaluation 
of hemispheric dominance for language using
functional MRI: A comparison with positron emission 
tomography. Human Brain Mapping, 6:367--389,
1998.
Zurif, E., Swinney, D., Prather, P., Solomon, J. &
Bushell, C. An online analysis of syntatic processing
in Broca's and Wernicke's aphasia. Brain and Language, 45:448464, 1993.
