Biomedical subjects

Phyllis Koenig

Publications and source records attributed to Phyllis Koenig.

10 recordsLinked to original sources

PubMed2006

How necessary are the stripes of a tiger? Diagnostic and characteristic features in an fMRI study of word meaning.

This study contrasted two approaches to word meaning: the statistically determined role of high-contribution features like striped in the meaning of complex nouns like "tiger" typically used in studies of semantic memory, and the contribution of diagnostic features like parent's brother that play a critical role in the meaning of nominal kinds like "uncle." fMRI monitored regional brain activity while participants read complex noun descriptions consisting of statistically high-contribution and low-contribution features; and nominal kind descriptions consisting of diagnostic and characteristic features. We found different patterns of activation depending on the type of noun and the type of feature contributing to the noun. Complex nouns recruited significantly greater bilateral superior temporal and left prefrontal activation compared to nominal kind nouns, while nominal kind nouns activated bilateral medial parietal and right inferior parietal regions more than complex nouns. Moreover, features making a statistically high contribution to complex noun meaning activated right inferior frontal cortex relative to low-contribution features, while diagnostic features of nominal kinds activated left dorsolateral prefrontal and right parietal regions more than characteristic features. These findings are consistent with the hypothesis that at least two different neural mechanisms appear to support word meaning: one driven by a statistically determined approach to feature knowledge, and the other sensitive to the qualitatively critical role that a specific diagnostic feature plays in word meaning.

Adult↗

PubMed2006

Category-specific effects in semantic memory: category-task interactions suggested by fMRI.

Much work has investigated the neural representation of specific categories of knowledge, but relatively scant attention has been paid in the cognitive neuroscience literature to the semantic processes that contribute to semantic memory. In this study, we monitored regional cortical activity with fMRI while healthy young adults evaluated visually displayed NATURAL KIND, ARTIFACT, and ABSTRACT nouns with two standard tasks: Typicality judgments and Pleasantness judgments. We observed a significant interaction effect between the category of knowledge and the type of judgment used to evaluate members of these semantic categories. Typicality judgments recruited greater temporal-occipital activation relative to Pleasantness judgments of the same category, and this was seen for comparisons of all three semantic categories. However, when contrasted with Typicality judgments, Pleasantness judgments activated a different anatomic distribution for each semantic category. These findings are consistent with a dynamic approach to semantic memory that includes at least two components: semantic knowledge and semantic processes that interpret this knowledge in several ways depending on the particular semantic challenge.

Adult↗

PubMed2004

The neural basis for novel semantic categorization.

We monitored regional cerebral activity with BOLD fMRI during acquisition of a novel semantic category and subsequent categorization of test stimuli by a rule-based strategy or a similarity-based strategy. We observed different patterns of activation in direct comparisons of rule- and similarity-based categorization. During rule-based category acquisition, subjects recruited anterior cingulate, thalamic, and parietal regions to support selective attention to perceptual features, and left inferior frontal cortex to helps maintain rules in working memory. Subsequent rule-based categorization revealed anterior cingulate and parietal activation while judging stimuli whose conformity with the rules was readily apparent, and left inferior frontal recruitment during judgments of stimuli whose conformity was less apparent. By comparison, similarity-based category acquisition showed recruitment of anterior prefrontal and posterior cingulate regions, presumably to support successful retrieval of previously encountered exemplars from long-term memory, and bilateral temporal-parietal activation for perceptual feature integration. Subsequent similarity-based categorization revealed temporal-parietal, posterior cingulate, and anterior prefrontal activation. These findings suggest that large-scale networks support relatively distinct categorization processes during the acquisition and judgment of semantic category knowledge.

Adult↗

PubMed2003

Category-specific medial temporal lobe activation and the consolidation of semantic memory: evidence from fMRI.

Semantic memory consolidation was studied by comparing medial temporal lobe (MTL) fMRI activation to ANIMAL, IMPLEMENT and ABSTRACT nouns in healthy seniors to that of young adults. Relative to healthy seniors, young adults were predicted to show greater MTL activation for IMPLEMENTS, but not ANIMALS, because the ANIMALS category consists of highly intercorrelated and overlapping features that should require less MTL-mediated binding than IMPLEMENTS over a shorter period of time during concept consolidation. ABSTRACT meanings are context-dependent and do not consist of fixed feature sets. Thus it was predicted that ABSTRACT words would not involve age-related feature binding mediated by the MTL. These predictions were confirmed by the results. Our observations are consistent with the hypothesis that the structure of a category influences the consolidation of knowledge in semantic memory.

Adult↗

PubMed2003

Neural basis for verb processing in Alzheimer's disease: an fMRI study.

Patients with probable Alzheimer's disease (AD) have difficulty understanding verbs. To investigate the neural basis for this deficit, the authors used functional magnetic resonance imaging to examine patterns of neural activation during verb processing in 11 AD patients compared with 16 healthy seniors. Subjects judged the pleasantness of verbs, including MOTION verbs and COGNITION verbs. Healthy seniors and AD patients both activated posterolateral temporal and inferior frontal regions during judgments of verbs. These activations were relatively reduced and somewhat changed in their anatomic distribution in AD patients compared with healthy seniors, particularly for the subcategory of MOTION verbs, but AD patients showed minimal activation in association with COGNITION verbs. These findings imply that poor performance with verbs in AD is due in part to altered activation of the large-scale neural network that supports verb processing.

Aged↗

PubMed2003

Neural basis for semantic memory difficulty in Alzheimer's disease: an fMRI study.

Patients with probable Alzheimer's disease are thought to have a semantic memory deficit. We used functional MRI to evaluate the neural basis for impaired semantic memory for ANIMALS and IMPLEMENTS in 11 patients with Alzheimer's disease and 16 healthy seniors. For both categories of knowledge, Alzheimer's disease patients show reduced activation in the left posterolateral temporal-inferior parietal cortex compared with healthy seniors. Activation changes in this heteromodal association region may be related to an impairment of the category-neutral semantic processes involved in integrating feature knowledge that is represented in modality-specific association cortices. We also found increased activation of an area of the left temporal cortex for both categories of knowledge in Alzheimer's disease that was not activated in healthy seniors. Category-specific changes were also seen in Alzheimer's disease compared with healthy seniors that may be related to the neural representation of category-specific feature knowledge represented in semantic memory. For ANIMALS, the left ventral temporal cortex was activated in Alzheimer's disease in an anatomical distribution that was posterior to the left ventral recruitment for this category in healthy seniors. For IMPLEMENTS, frontal-striatal regions were activated in Alzheimer's disease in a manner that was displaced from the locus of recruitment for this category in healthy seniors. Our findings are consistent with a two-component model of semantic memory involving category-neutral processes operating on category- specific knowledge, and both components appear to be compromised in Alzheimer's disease. Components of the large-scale neural network underlying semantic memory may modify themselves to maintain performance in the face of a neurodegenerative disease.

Aged↗

PubMed2002

Neural basis for sentence comprehension: grammatical and short-term memory components.

We monitored regional cerebral activity with BOLD fMRI while subjects were presented written sentences differing in their grammatical structure (subject-relative or object-relative center-embedded clauses) and their short-term memory demands (short or long antecedent-gap linkages). A core region of left posterior superior temporal cortex was recruited during all sentence conditions in comparison to a pseudofont baseline, suggesting that this area plays a central role in sustaining comprehension that is common to all sentences. Right posterior superior temporal cortex was recruited during sentences with long compared to short antecedent-gap linkages regardless of grammatical structure, suggesting that this brain region supports passive short-term memory during sentence comprehension. Recruitment of left inferior frontal cortex was most clearly associated with sentences that featured both an object-relative clause and a long antecedent-gap linkage, suggesting that this region supports the cognitive resources required to maintain long-distance syntactic dependencies during the comprehension of grammatically complex sentences.

Adult↗

PubMed2002

Neural representation of verb meaning: an fMRI study.

The neural basis for verb comprehension has proven elusive, in part because of the limited range of verb categories that have been assessed. In the present study, 16 healthy young adults were probed for the meaning associated with verbs of MOTION and verbs of COGNITION. We observed distinct patterns of activation for each verb subcategory: MOTION verbs are associated with recruitment of left ventral temporal-occipital cortex, bilateral prefrontal cortex and caudate, whereas COGNITION verbs are associated with left posterolateral temporal activation. These findings are consistent with the claim that the neural representations of verb subcategories are distinct. Although the "sensory-motor" hypothesis may play a role in explaining activation associated with MOTION verbs, the left posterolateral temporal distribution of cortical activation associated with COGNITION verbs cannot be easily explained by the "sensory-motor" hypothesis. We suggest that left posterolateral temporal activation supports aspects of lexical semantic processing concerned with the neural representation of propositional knowledge contributing to COGNITION verbs.

Adult↗

PubMed2002

The neural basis for category-specific knowledge: an fMRI study.

Functional neuroimaging studies of healthy adults have associated different categories of knowledge with distinct activation patterns. The basis for these recruitment patterns has been controversial, due in part to the limited range of categories that has been studied. We used fMRI to monitor regional cortical recruitment patterns while subjects were exposed to printed names of Animals, Implements, and Abstract nouns. Both Implements and Abstract nouns were related to recruitment of left posterolateral temporal cortex and left prefrontal cortex, and Abstract nouns additionally recruited posterolateral temporal and prefrontal regions of the right hemisphere. Animals were associated with activation of ventral-medial occipital cortex in the left hemisphere at a level that approaches significance. These findings are not consistent with the "sensory-motor" model proposed to explain the neural representation of word knowledge. We suggest instead a neural model of semantic memory that reflects the processes common to understanding Implements and Abstract nouns and a selective sensitivity, possibly evolving from adaptive pressures, to the overlapping, intercorrelated visual characteristics of Animals.

Adult↗

PubMed2002

The neural basis for categorization in semantic memory.

We asked young adults to categorize written object descriptions into one of two categories, based on a rule or on overall similarity, while we monitored regional brain activity with functional magnetic resonance imaging (fMRI). We found significantly greater recruitment of left dorsolateral prefrontal cortex for rule-based categorization in direct comparison with similarity-based categorization. Recruitment of right ventral frontal cortex and thalamus was uniquely associated with rule-based categorization as well. These observations lend support to the claim that executive functions such as working memory, inhibitory control, and selective attention contribute to rule-based categorization. Right inferior parietal activation was uniquely associated with similarity-based categorization. This region may play an important role in overall feature configuration that is important for this form of categorization. We found other brain regions recruited for both rule-based and similarity-based categorization: Anterior cingulate cortex may support the implementation of executive functions during situations with competing response alternatives; and left inferior parietal cortex may be related to the integration of feature knowledge about objects represented in modality-specific association cortices. We also administered a degraded-similarity condition where the task of categorizing a written object description was made more difficult by perceptually degrading the stimulus materials. The degraded condition and the rule-based condition, but not the similarity-based condition, were associated with caudate activation. The caudate may support resource demands that are not specific for a particular categorization process. These findings associate partially distinct large-scale neural networks with different forms of categorization in semantic memory.

Adolescent↗