Semantic encoding enhances the pictorial superiority effect in the oldest-old

ABSTRACT We examined the effect of a semantic orienting task during encoding on free recall and recognition of simple line drawings and matching words in middle-aged (44-59 years), older (60-89 years), and oldest-old (90+ years) adults. Participants studied line drawings and matching words presented in blocked order. Half of the participants were given a semantic orienting task and the other half received standard intentional learning instructions. Results confirmed that the pictorial superiority effect was greater in magnitude following semantic encoding compared to the control condition. Analyses of clustering in free recall revealed that oldest-old adults' encoding and retrieval strategies were generally similar to the two younger groups. Self-reported strategy use was less frequent among the oldest-old adults. These data strongly suggest that semantic elaboration is an effective compensatory mechanism underlying preserved episodic memory performance that persists well into the ninth decade of life.     

Aphasic performance on a lexical decision task: multiple meanings and word frequency

The lexical access of words varying in the number of meanings and frequency of occurrence was examined in fluent and nonfluent aphasic individuals and a control group of non-brain-damaged adults, using a lexical decision task. Fluent aphasic subjects performed similarly to nonfluent aphasic and normal subjects, showing that words with a high number of meanings and with a high frequency of occurrence were recognized as real words faster than words with few meanings or a low frequency of occurrence. While previous research has demonstrated that the number of meanings associated with a word exerts a powerful influence on the internal lexicon of normals, the results of this study suggest that brain damage resulting in aphasia does not disrupt this semantic organization.     

Refractory semantics in global aphasia: On semantic organisation and the Access–Storage distinction in neuropsychology

Abstract

A single case study is reported of a global aphasic patient, JM, with impaired access to semantic information which was particularly severe for the class of proper names. JM's ability to perform matching tasks with printed words and pictures to auditory words deteriorated when items were repeated, especially when the response–stimulus interval was short. Performance was also inconsistent across items. The effect of repeated testing on items generalised to other, previously untested members of the same category. Despite this, JM was able to access general semantic information about stimuli from the affected categories (e.g. to categorise boys' and girls' names), and showed good ability to access an input lexicon concerning these stimuli. There was also a close relationship between the categories affected when he was tested with pictures and printed words. We propose that JM's deficit can be attributed to his semantic system entering an abnormal refractory state once semantic access for a particular item has been achieved, and with this stage being isolated from the procedures providing access to stored lexical knowledge. Furthermore, the representations affected seem common to pictures and printed words. We discuss the implications of the results for understanding the nature of semantic representations in general and for proper names in particular, and for the distinction between access and storage deficits in neuropsychology.     

A comparison of the category fluency deficits associated with Alzheimer's and Huntington's disease

The supermarket verbal fluency test of the Dementia Rating Scale (DRS) was administered to 20 patients with mild Alzheimer's disease (Mi-DAT), 20 patients with moderately severe Alzheimer's disease (Mo-DAT), 20 patients with Huntington's disease (HD), and 40 normal control subjects. The findings confirmed previous reports that Mo-DAT patients retrieved fewer words per category of supermarket items sampled and had a greater propensity to generate category labels (superordinates) than did intact controls. Similar disruptions of the structure of semantic knowledge were also noted in the fluency performances of the Mi-DAT and HD patients. The Mi-DAT patients' tendency to generate few exemplars for each category sampled suggested that a significant disruption in the structure of semantic knowledge occurred even in the earliest stages of DAT. When the present fluency findings for the HD patients were considered with previous reports of linguistic changes in this disorder, it appeared that HD patients' deterioration in semantic knowledge involved associative changes rather than the bottom-up breakdown associated with DAT.     

Lexical decision and aphasia: Evidence for semantic processing

Wernicke's and Broca's-Conduction aphasics and a Global aphasic were presented with a lexical-decision task in which English words and pronounceable nonwords were preceded by semantically related, unrelated, or nonword primes. The patients were also given a simple semantic-judgment task using the word pairs from the lexical-decision task. Wernicke's aphasics performed similar to normals and Broca's-Conduction aphasics showing significantly shorter latencies in making real-word identifications when preceded by a semantically related word. In addition, both superordinate and coordinate associates showed semantic-priming effects. Performance on the semantic-judgment task showed significantly more impairment in the aphasic group than in the normal controls. These results suggest that aphasics with even severe language impairments retain stored semantic information that may be automatically activated, yet is inaccessible to conscious semantic decision during metalinguistic tasks.     

The effect of semantic plausibility on sentence comprehension in aphasia

Tested were 50 aphasic patients (16 Broca's, 15 Wernicke's, 10 global, and 9 amnesic), 13 nonaphasic brain damaged patients, and 13 normal adults to evaluate the effect of semantic plausibility on sentence comprehension in active affirmative declarative sentences with a sentence-picture matching task. A plate of two pictures was provided for each stimulus sentence, and the subject was required to choose the picture corresponding to the sentence presented auditorily. Two types of sentences in terms of plausibility were prepared, i.e., probable sentences (P) describing common events in our daily life and improbable sentences (I) describing rare events. There were four kinds of combinations of a picture with the other to make a correct/(distractor) set, i.e., P/(P), P/(I), I/(P), and I/(I) constructions. The results indicated that probable sentences were more comprehensible than improbable sentences, and that the effect of semantic plausibility did not differ among aphasic types.     

Spatial organization in the free recall of pictorial stimuli

Thirty-one young adults were presented with a series of visual arrays each containing drawings of objects. Free recall of the objects on each visual array could be organized by the spatial location of the objects or by another type of organization. The other type of organization was different on each array and comprised semantic, shape, colour, size, orientation or phonetic categories. The results showed that free recall could be organized by spatial location or by semantic, shape, colour or size categories. However, only semantic and colour category organization were found to correlate significantly with recall. To account for the correlation results, two distinct general forms of organization are hypothesized.     

Cue utilization following different forms of encoding in mildly, moderately, and severely demented patients with Alzheimer's disease

The ability of patients with Alzheimer's disease (AD) to utilize semantic category cues in order to improve memory performance was examined. Categorizable lists of words or objects were presented under five different encoding conditions: (a) nouns, (b) objects, (c) objects with a semantic orienting question, (d) objects with self-generated motoric acts, and (e) objects with experimenter-instructed motoric acts. Subjects were asked to memorize the items for a free recall test, and were subsequently provided with the category names in a cued recall test. Mildly, moderately, and severely demented AD patients, and a group of normal older adults participated in the study. Results showed that normal older adults and mildly demented AD subjects were able to utilize cues to improve memory performance in all conditions. Moderately demented patients utilized cues in all conditions except in the verbal condition (condition [a]), whereas severely demented patients utilized cues only in the motoric condition (condition [e]). These results suggest that the ability to utilize category cues following a motoric encoding is preserved later in AD than the ability to utilize cues after a semantic encoding.     

Word-finding abilities of three types of aphasic subjects

Word-finding difficulties are often observed among different types of aphasic patients. This investigation analyzed the word-finding abilities of 30 aphasic subjects (10 Broca's, 10 Wernicke's, and 10 anomic). Forty nouns counterbalanced according to word length and frequency of occurrence in English language usage were used as stimuli and presented through four modalities (oral expression, writing, auditory comprehension, and reading comprehension). It was expected that patterns of word finding abilities would help in the classification of the different types of aphasia. In addition, long words and less frequently occurring words in English language usage should prove more difficult in word-finding ability, regardless of modality. The results of this study found long words and less frequent words were more difficult for aphasic subjects. Among the modalities, long words were significantly harder than short words for the writing modality only. It was also found that semantic errors were the most common errors for all types of aphasic subjects. Broca's subjects produced significantly moreno response errors in oral expression; Wernicke's subjects produced significantly more semantic and phonemic errors in reading comprehension; and, Wernicke's subjects produced significantly more unrelated errors in both oral expression and reading comprehension. Clinical implications were also discussed.The present study was based on a doctoral dissertation completed at the City University of New York in partial fulfillment of the requirements of the doctoral degree in Speech and Hearing Sciences by the first author under the direction of the second author. The authors wish to thank Dr. Louis J. Gerstman for his assistance with the statistical analysis of this research and Dr. Robert Goldfarb for all his helpful suggestions and editorial comments.     

The meaning of ‘life’ and other abstract words: Insights from neuropsychology

There are a number of long‐standing theories on how the cognitive processing of abstract words, like ‘life’, differs from that of concrete words, like ‘knife’. This review considers current perspectives on this debate, focusing particularly on insights obtained from patients with language disorders and integrating these with evidence from functional neuroimaging studies. The evidence supports three distinct and mutually compatible hypotheses. (1) Concrete and abstract words differ in their representational substrates, with concrete words depending particularly on sensory experiences and abstract words on linguistic, emotional, and magnitude‐based information. Differential dependence on visual versus verbal experience is supported by the evidence for graded specialization in the anterior temporal lobes for concrete versus abstract words. In addition, concrete words have richer representations, in line with better processing of these words in most aphasic patients and, in particular, patients with semantic dementia. (2) Abstract words place greater demands on executive regulation processes because they have variable meanings that change with context. This theory explains abstract word impairments in patients with semantic‐executive deficits and is supported by neuroimaging studies showing greater response to abstract words in inferior prefrontal cortex. (3) The relationships between concrete words are governed primarily by conceptual similarity, while those of abstract words depend on association to a greater degree. This theory, based primarily on interference and priming effects in aphasic patients, is the most recent to emerge and the least well understood. I present analyses indicating that patterns of lexical co‐occurrence may be important in understanding these effects.     

Semantic impairment and anomia in Alzheimer''s disease

Impairment in naming visually presented objects was investigated in patients with a clinical diagnosis of Alzheimer's disease. Impaired object naming correlated with difficulty listing the names of objects from a specified semantic category and with erroneous selection of words semantically related to the correct names for objects in a name recognition test. These results suggest that patients with Alzheimer's disease have a semantic impairment characterized by inability to distinguish among objects that are members of the same semantic category, and that this impairment is associated with difficulty producing the names for objects. Semantic impairment was present in patients with normal ability to discriminate visually presented shapes, indicating that the semantic deficit in Alzheimer's disease occurs independently of abnormalities of visuospatial function. Patients tended to make errors on the same items in both confrontation naming and name recognition tests, suggesting that the semantic impairment in Alzheimer's disease involves loss of information about specific objects and their names.     

Word Length and Vowel Duration in Apraxia of Speech: The Use of Relative Measures

Previous research has established that the duration of stressed word stem vowels is shorter in polysyllabic words than in monosyllabic words for normal speakers and for speakers with aphasia and apraxia of speech (AOS). However, the results are inconsistent across studies with regard to the magnitude and pattern of the duration reduction for apraxic speakers. We hypothesized that this inconsistency may be explained based on different relative measures of duration reduction. A speech sample was obtained from 10 aphasic speakers with AOS, 10 aphasic speakers without AOS, and 10 normal controls. As predicted, the use of two different relative measures resulted in different vowel reduction patterns, both of which were consistent with previous reports. The results further indicate that the production of polysyllabic words is particularly taxing in AOS and is associated with a substantial reduction of speaking rate compared to other aphasic and normal speakers.     

Triadic decision making in lexical memory

Word and category recognition was investigated in the context of other stimuli, where the semantic distance relationships among the stimuli were derived from multidimensional scaling. On each trial, three horizontal strings of letters were presented. In the word condition, a positive response was required when the three strings formed three words; in the category condition, a positive response was required when the three strings formed words belonging to the same category. The results indicated that: (a) category decisions take about 150-200 msec longer than do word decisions, (b) word decisions are facilitated by a common categorical membership but semantic distances within the category are relatively unimportant, and (c)within-category semantic distances systematically altered response time for the category condition. It was hypothesized that semantic distance relationships may be sensitized for categorical decisions, but that only large semantic distances function effectively for word decisions.     

Changes to the object recognition system in patients with dementia of the Alzheimer's type

Do DAT patients show category-specific deficits in object identification, and do they arise from semantic or visual damage? Participants decided whether line drawings of living and nonliving objects matched names at superordinate, basic, or subordinate levels. Patients were most impaired with superordinate decisions. Controls had most difficulty with subordinate decisions. No category-specific deficit was found with patients. Impaired superordinate decisions by the patients support semantic damage. If category-specific deficits arise from damaged semantics, they should have been found. Since they were not, and since patients performed subordinate decisions the best, a visual basis to category specificity is supported. Finally, a living advantage was found with normal observers which cannot be spurious due to differences in concept familiarity since living and nonliving objects were matched for this variable.     

Variability in the semantic errors produced by brain-injured patients

One of the most common types of errors produced by aphasic patients during oral word production is semantic errors. However, although aphasia semantic errors are often treated as a single homogenous group, there are, in fact, several subtypes defined by the nature of the error-target relationship: paradigmatic, if the two words are category coordinates; syntagmatic, if they are associatively related but from different semantic categories; and superordinate, if the meaning of the error is broader than the meaning of the target. The goal of this study was to investigate whether or not these various subtypes of semantic errors have a similar processing origin. With this objective, we compared the patterns of semantic errors made by a group of Alzheimer patients in a picture-naming task with those made by a group of aphasic patients. We examined the percentages of the different error types, the degree of association between target and error, and the frequency values both of errors and targets. The results suggest that the three subtypes of semantic errors have different origins: the superordinate appear to arise at the semantic level, the syntagmatic at the lexical level, and the paradigmatic at both levels of processing.     

Semantic priming in young and older adults: evidence for age constancy in automatic and attentional processes

Automatic and attentional components of semantic priming and the relation of each to episodic memory were evaluated in young and older adults. Category names served as prime words, and the relatedness of the prime to a subsequent lexical decision target was varied orthogonally with whether the target category was expected or unexpected. At a prime-target stimulus-onset asynchrony (SOA) of 410 ms, target words in the same category had faster lexical decision latencies than did different category targets. This effect was not significant at a 1,550-ms SOA and was attributed to automatic processes. Expected category targets had faster latencies than unexpected category targets at the 410-ms SOA, and the magnitude of the effect increased at the 1,550-ms SOA. This effect was attributed to attentional processes. These patterns of priming were obtained for both age groups, but in a surprise memory test older adults had poorer recall of primes and targets. We discuss the implications of these results for the hypothesis that older adults suffer deficits in selective attention and for the related hypothesis that attentional deficits impair semantic processing, which causes memory decrements in old age.     

Developmental effects of typicality and superordinate property dominance on sentence verification

Second graders (mean age, 8 years 3 months), fourth graders (mean age, 10 years 4 months), and adults verified telegraphic sentences with typical or atypical subject nouns and high or low dominant property predicates. The hypothesis tested was that the similarity in the attribute structures of category members to their superordinate prototype should be related to degree of typicality. Adult reaction time and error data supported the prototype model of semantic category structure. Second and fourth graders showed comparable property knowledge to adults, but evidenced different organizational patterns than predicted by the adult model. The results suggest that with development children learn to simultaneously use many attribute dimensions and to abstract the family resemblance structure and relative importance of category properties.     

What is right with “deep” dyslexic patients?

Two aphasic adults with a specific acquired dyslexia were given tests requiring the processing of written words and sentences. Despite the general severity of the patients' deficits, some aspects of such processing appear to be relatively well preserved. The patients have particular difficulty reading aloud function words and abstract words; yet in word/nonword discrimination tests, both patients showed normal recognition of function words and one showed normal performance with abstract words. The patients do have a deficit in comprehension of visually presented words and sentences; yet their performance on comprehension tests was considerable and, moreover, showed meaningful relationships with their ability to read aloud.     

Idiom comprehension in aphasic patients

Idiom comprehension was assessed in 10 aphasic patients with semantic deficits by means of a string-to-picture matching task. Patients were also submitted to an oral explanation of the same idioms, and to a word comprehension task. The stimuli of this last task were the words following the verb in the idioms. Idiom comprehension was severely impaired, with a bias toward the literal interpretation. Very few errors were produced with words, making impossible to establish a correlation between comprehension of idioms and of individual words. The difficulties in idiom comprehension seemed to be due to the fact that patients rely on a literal-first strategy, accessing a figurative interpretation only when the linguistic analysis fails to yield acceptable results.     

The effects of slowed speech on auditory comprehension in aphasia

The present study investigates the effects of slowed speech on auditory comprehension in aphasia. Specifically, an attempt was made to isolate the effects of added time on comprehension at the language processing stages of auditory perception, by increasing the duration of the vowel segments in each word; word recognition and semantic analysis, by adding silences between words; and syntactic analysis, by adding silences at constituent phrase boundaries. Sentences were also read at a slow rate to see the effects of naturally slowed speech on sentence comprehension. Test sentences consisted of simple active and passive declarative sentences, and complex sentences with embedded medial and final relative clauses. Sentences were either semantically reversible or nonreversible. Thirty-four aphasic patients who varied in both severity and type of aphasia were tested on a picture verification task. Results indicated that slowing facilitated language comprehension significantly only in the syntactic condition. Neither syntactic complexity nor semantic reversibility interacted with slowed speech to facilitate auditory language comprehension. Further, it was only the Wernicke's aphasics who showed significant improvement with time added at constituent boundaries. These results suggest that time alone does not facilitate language comprehension in aphasia, but that rather it is the interaction of time with syntactic processing which improves comprehension.