Dissertation Research Overview
My dissertation research, performed in conjunction with Dr. Frank Guenther at the Department of Cognitive and Neural Systems at Boston University, focused on investigating how the brain represents and enacts sequences of learned sounds during speech production. This work included an experimental component using functional magnetic resonance imaging (fMRI) and magnetoencephalography (MEG), as well as a computational component resulting in the development of an extended neural model of speech production.
Dissertation Abstract
Defense Presentation
More coming soon...
Articles
Bohland, J.W. and Guenther, F.H. (2006). An fMRI investigation of syllable sequence production. NeuroImage, 32 (2): 821-841.
Pubmed |
731kB pdf
Guenther, F.H., and Bohland, J.W. (2002). Learning sound categories: A neural model and supporting experiments. Acoustical Science and Technology, 23(4): 213-220. Japanese-language version appeared in Journal of the Acoustical Society of Japan, 58 (7): 441-449, 2002.
686kB pdf
Bohland, J.W. and Minai, A.A. (2001). Efficient associative memory using small-world architecture. Neurocomputing, 38-40: 489-496.
182kB pdf
Bohland, J.W. and Minai, A.A. (2000). Small-World model of associative memory. Proceedings of the International Joint Conference on Neural Networks, 5: 597-604.
Presentations
"Neuroimaging and computational modeling of syllable sequence production." [Dissertation Defense]
8.2MB ppt
"Neural substrates for syllable sequence planning and production." Massachusetts Institute of Technology Speech Communication Group Seminar Series. Cambridge, MA. March 22, 2006. [Invited talk].
"An fMRI investigation of syllable sequence production." Massachusetts Institute of Technology Neurolinguistics Group. Cambridge, MA. April 21, 2006. [Invited talk].
"Modeling and imaging of sequencing in speech production." 10th International Conference on Cognitive and Neural Systems, Boston, MA. May 19, 2006. [Conference talk].
"Modeling the representation of speech sounds in auditory cortical areas." 1435th Meeting of the Acoustical Society of America. Nashville, TN. April, 2003. [Invited talk].
Posters
Ghosh, S.S. and Bohland, J.W. (2005). A speech recording setup for fMRI with online reduction of scanner noise. 11th Annual Meeting of the Organization for Human Brain Mapping, Toronto.
Tourville, J.A., Guenther, F.H., Ghosh, S.S., Reilly, K.J., Bohland, J.W., and Nieto-Castanon, A. (2005). Effects of acoustic and articulatory perturbation on cortical activity during speech production. 11th Annual Meeting of the Organization for Human Brain Mapping, Toronto.
Tourville, J.A., Guenther, F.H., Ghosh, S.S., and Bohland, J.W. (2004). Effects of jaw perturbation on cortical activity during speech production. 75th Meeting of the Acoustical Society of America, San Diego.
Bohland, J.W. and Guenther, F.H. (2004). An fMRI investigation of the neural bases of sequential organization for speech production. 10th Annual Meeting of the Organization for Human Brain Mapping, Budapest.
5.8MB pdf
Ghosh, S.S., Bohland, J.W., and Guenther, F.H. (2003). Comparisons of brain regions involved in overt production of elementary phonetic units. 9th Annual Meeting of the Organization for Human Brain Mapping, New York.
1.6MB pdf
Miscellaneous
Guenther, F.H., Nieto-Castanon, A., Tourville, J.A., and Bohland, J.W. (2002). 'Holes' in the brain help us sort out sounds. Lay Language Paper for the 143rd Meeting of the Acoustical Society of America.
HTML Link
Bohland, J.W. (2000). Associative memory on small-world networks. Unpublished Masters Thesis.
Other Projects / Interests
Coming soon...
Neuroimaging and computational modeling
of syllable sequence production
Jason W. Bohland
Fluent speech involves producing sound sequences that are composed
from a finite alphabet of learned words, syllables, and phonemes. The
brain thus requires machinery to organize and enact properly ordered
and timed motor command sequences that correspond to the desired
phonological plan. This dissertation seeks to provide an enhanced
mechanistic understanding of this system through a combination of
computational neural modeling and neuroimaging.
The first portion of the dissertation describes an experiment using
sparse event-triggered functional magnetic resonance imaging (fMRI) to
measure brain responses due to preparation and overt production of
non-lexical three syllable sequences of varying complexity. The
network of brain regions related to initiation, motor execution and
hearing one's own voice was found to include the primary motor and
somatosensory cortices, auditory cortices, supplementary motor area
(SMA), insula, and portions of the thalamus, basal ganglia, and
cerebellum. Additional stimulus complexity led to increased
engagement of the basic speech network and recruitment of additional
areas known to be involved in control of non-speech motor sequences,
including the left hemisphere inferior frontal sulcus region and
posterior parietal cortex, and bilateral regions at the junction of
the anterior insula and frontal operculum, the pre-SMA, basal ganglia,
anterior thalamus, and cerebellum.
These experimental results as well as previous clinical, behavioral,
and imaging data were used to guide the development of a neural model
of speech syllable sequencing based on a "competitive queuing"
architecture. The new GODIVA (Gradient Order DIVA) model extends the
DIVA model of speech production, which describes how individual speech
items are learned and produced, to include explicit parallel
representations for forthcoming utterances. GODIVA posits detailed
neuroanatomical substrates and neurobiologically plausible mechanisms
for its components. The model can thus account for a database of
clinical and neuroimaging results beyond the scope of previous
non-biological models.
Finally, preliminary efforts using magnetoencephalography (MEG) and
surface electromyography (EMG) to obtain neuroimaging data that
complements fMRI results and offers further modeling constraints are
described. A novel algorithm was applied to detect neural source
components that could be used to reliably discriminate between stimuli
that necessitated the preparation of one, two, or three syllable
plans.
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