Overview
My
primary research interests lie in understanding the neuropsychological and
neurodevelopmental substrates of language processing in normal and abnormal
development, particularly in autism and other developmental disabilities. I am interested in the study of the
cognitive requirements for early single word learning from perceptual
categorization to semantic or conceptual knowledge and how this early word
knowledge is later transformed into longer strings of sentences and ultimately
connected discourse. My research
projects have aimed at understanding the complex relationships between different
brain systems (attention, memory, visual processing, executive functions) and
the language system by studying their impairment in brain disorders such as,
aphasia, autism and ADHD. My goal has been to find corroborating behavioral
evidence for neural substrates that are known to be involved in language and
semantic impairments in certain developmental disorders, such as pathways that
involve specific frontal lobe areas. This evidence may lead to specific
cognitive interventions to improve everyday communication and language skills. For
example, my research has shown that task changes such as more time to respond,
less interference and cueing may reduce subjects' poor regulation of attention,
allowing them to perform in more typical ways. In addition, I have studied the connection between cognitive flexibility as measured by working
memory tasks involving executive function and the flexibility required in the
language system. I have also studied the connection between attention and
executive-type impairments in other domains such as visual processing, visual
search and number processing.Prior
to working with children with developmental disabilities, I investigated
language processing and acquisition issues in normally developing children
(German first language acquisition) as well as the rehabilitation of language
in aphasia using computer technology.
Selected
Publications
Boser
K, Weinrich M: Functional categories in agrammatic
production: Evidence for access to tense projections. Brain and Language 1998; 65(1): 207-210.
Weinrich
M, Boser K, McCall D: Representation of linguistic rules in the
brain: Evidence from training an aphasic patient to produce past tense verb
morphology. Brain and Language 1999; 70(1): 144-58.
Boser
K, Weinrich M, McCall D: Maintenance of oral production
in agrammatic aphasia: Verb tense morphology training. Journal of
Neurorehabilitation and Neural Repair 2000; 14(2): 105-18.
Boser
K, Higgins S, Fetherston A, Preissler MA, Gordon B:Semantic fields in low-functioning autism. Autism and Developmental
Disorders 2002, vol. 32(6) 563-82.
Presentations
Boser
K, Smrcka V, Wheelan M, Fitzgerald A,
Hamdy R, Gordon B: Familiarity and interference in learning single
word-to-picture discrimination in low functioning autism. Cognitive
Neuroscience Society, San Fransisco, CA, 2002.
Boser
K, Higgins S, Kiger R, O'Grady J, Gordon
B: Prototypicality effects and color categories in non-verbal individuals with
autism. Society for Neuroscience Abstracts, San Diego, CA, 2001.
Boser
K, Smrcka V, Stark S, Haarmann H, Gordon
B: Use of context in working memory in autism. International Meeting for
Autism Research, Orlando, Fl, 2002.
Boser
K, Gordon B: Exact number without exact
language in a child with autism. American Psychological Association,
Atlanta, GA, 2003.
Boser K: Language impairments in
autism correlate with impairments in working memory for temporally ordered
visual and auditory information, 4th Science Of Aphasia Conference:
Cross-Disciplinary Aspects, Trieste (Italy), August 22-27, 2003
Boser
K, Boatman D, Gordon B: Hemispheric
asymmetries in hierarchical visual processing in autism. Society for
Neuroscience, New Orleans, LA, 2003
Boser
K, Haarmann H, Gordon B: Semantic short‑term
memory impairment in childhood autism. 44th Annual Meeting of the
Psychonomics Society, Vancouver, British
Columbia, 2003
Boser
K: Proactive Interference in Subjects with
Autism. Annual Meeting of the International Neurological Society, Baltimore, MD, February, 2004.
Boser
K, Haarmann H, Knobel M: Poor Semantic
Activation and Interference In Autism. International Meeting for Autism
Research, Sacramento, CA, May, 2004.
Boser
K, Knobel M: Poor Inhibition of
Distracters In Pop-Out Counting: Evidence For Impaired Attention In Autism. International
Meeting for Autism Research, Sacramento, CA, May, 2004.
Research
Interests:
Autism is a
unique disorder in its complexity and the contribution of a variety of different
kinds of impairments to the syndrome. In addition to severe language impairments, children with autism have
learning problems due to overfocused attention, difficulty switching from one
task to another and problems in cognitive flexibility. These symptoms have been associated
both with frontal and pre-frontal areas involved in executive control and with
cerebellar involvement and other areas thought to play a role in attention and
memory. It is not clear, however, that both lexical and non-lexical material is
processed in the same way. I have investigated executive function and
working memory in subjects with autism who have a particular deficit not
primarily with single word production or comprehension but with more abstract
sentences whose meaning is not derivable from real world knowledge. These subjects tend to have improved
ability in some tasks requiring visuo-spatial or counting/number abilities. I worked on studies which would help specify the nature of the working memory/executive
impairment using operation span tasks, tasks of context memory and those
involving the processing and concurrent storage of lexical and non-lexical
material. I believe the connection
between operation span, verbal working memory and language comprehension is an
important one, particularly for autism. Isolating the form of the relationship between working memory and
prefrontal impairments in autism we can better relate the specific functions of
rule-based frontal areas and cerebellar areas associated with temporal integration
with language processing in other impairments.
A
second main component of my research involves visual as well as number
processing in autism. I have demonstrated that subjects with autism may not use
number distance in the same manner to determine relative number size as normal
subjects. Their ability to count items in a 'pop-out' task seemed to follow a separate pattern with respect to subitization ( 3 items or less) relative to normal controls. In a counting count span task, I found that subjects with autism
counted faster when objects were organized like dots on a die, but, unlike
age-matched controls, when the layout of items was random, their response time
did not improve if the spatial layout of the amount was repeated. One
hypothesis about this pattern of results may be that children with autism do
not effectively use information across both hemispheres to integrate incoming
perception from different modalities. We tested this theory using attention-demanding
Navon figures requiring suppression of one of two hierarchical perceptual
levels (global or local) presented to either one or both (competing) visual
fields. We also obtained non-visual measures of hemispheric lateralization with
auditory dichotic word and competing sentence tests. Only the children with
autism demonstrated slower reaction times responding to global information presented
to the RH in the attention demanding conditions. These
same subjects were also poor on a standardized dichotic listening test and a
majority showed abnormally large right ear (LH) lateralization. This
abnormal lateralization for attention demanding auditory processing may be related
to slower RH processing for attention demanding visual tasks. Further studies
of the hypothesis of poor inter-hemispheric transfer in autism will include
studies of categorization and prototype extraction of concrete and abstract
material across Right and Left hemispheres.
Evidence for impairment in autism in attending to relevant features was shown in my studies of single word learning in nonverbal subjects. I designed a
large computer-presented assessment of receptive noun vocabulary for non-verbal, low functioning
autistic individuals (using a touch screen and E-prime software). I showed that carefully controlled assessment (even of a single subject) can show
that semantic representations may be broader than assumed particularly when
appropriate distractor items are used. A high number of semantic errors
indicated that multiple related semantic representations were available and
competing. In a more recent training study using Cosmo's learning system and a related computerized assessment, we demonstrated that errorless learning followed by 'graduated' cueing lead to quicker and more comprehensive single word learning than beginning with cues and then providing an errorless trial (i.e., target only trial). Another area of my research has shown that color categorization and
receptive color knowledge may be available in the absence of color naming in
this population. Again, the controlled use of distractor items showed that
irrelevant but highly salient information is difficult to inhibit. For example,
prototypical and more saturated/brighter colors were easier for several nonverbal subjects to match and select
and also incorrectly selected when they were distractors. These studies invovled hundreds of individual trials carefully designed to examine a variety of competing and or contrasting characteristics of target and distractor items.
Finally,
the relation between pragmatic discourse context and language learning and
processing is another specific interest of mine from my earlier work which I will continue to pursue in the area of autism and developmental language impairment. Several of my published papers
concern the influence of pragmatic information on word order acquisition in
early German child language. Other published papers concern the use of a
computerized iconic language training system (C-VIC) in rehabilitating language
skills in aphasia. These papers examined several issues including; differences
in regular/irregular tense morphology across written and spoken output
modalities in an agrammatic aphasic patient trained to produce tense marked
sentences, evidence for long-term maintenance of language therapy, retraining
of spoken passive sentences and, the effect of vocabulary and sentence training
on generalization to narrative structures.
Summary
Individuals
with autism are notoriously heterogeneous and thus may share many features with
other developmental disorders. In order to distinguish unique autistic features
I have carefully designed computerized attention and working memory measures and
compare performance to normal controls subjects. These measures also need to be compared in other developmental disorders, such as ADHD, Down
syndrome and Williams syndrome whose language impairments and visuo-spatial and
number abilities differ in specific ways. My aim in this research has been to develop a better set of
assessment methods for this population using the latest technology. The goal is to determine more precisely the neuropsychological
underpinnings of the disorder which will contribute to the development of
therapeutic processes that might remediate specific EF deficits and increase
not only single word but also combinatorial sentence production and comprehension in autism.
