Adynamic Aphasia: A Transcortical Motor Aphasia with Defective Semantic Strategy Formation

Adynamic aphasia is a form of transcortical motor aphasia characterized by sparse but otherwise normal spontaneous speech that may improve when concepts are introduced by external stimuli. Akinesia, impaired concept formation, inertia of concept generation, a defective semantic network, damage or impaired access to the verbal output lexicon, and defective semantic strategy formation have been proposed to account for this disorder. We studied a patient with adynamic aphasia and frontal lobe systems dysfunction due to bilateral striatocapsular infarctions. The patient was not akinetic but did demonstrate inertia of concept generation that could be overcome with prompting. However, prompting did not improve the number of concepts generated. He demonstrated a generally intact verbal lexicon and semantic network and normal lexical priming. However, his ability to sort closely related items into different classes without prior cuing regarding the nature of the classes was defective. Although his verbal memory was normal, he appeared to use a serial rather than a semantic strategy to recall items. Finally, despite normal lexical priming, he was impaired on a letter fluency task. These results most clearly demonstrate a defect in semantic strategy formation but indicate an additional and possibly related deficit in concept formation and a partial deficit in lexical strategy formation. All of these deficits appear to reflect impairment in the hierarchical organization of knowledge specific to the task at hand. This appears to be a key component of executive functions supported by frontal lobe systems.     

Deep dysphasia: analysis of a rare form of repetition disorder

"Deep dysphasia" is the parallel in repetition to the reading impairment deep dyslexia. Our patient, S.M., showed part of speech, word/nonword, and concreteness effects in repetition, and he made semantic errors, but his oral reading was relatively spared. Further testing indicated that S.M. did not have difficulty perceiving spoken stimuli or deciding their lexical status, but he was deficient at semantically processing spoken words. Moreover, his phonemic memory was severely impaired. We argue that the routes for repetition (lexical and nonlexical) that function without semantic mediation were defective and that deficits in phonemic memory further diminished their effectiveness, since initial phonological encoding of spoken words was not available to guide the output stages of phonological processing. In addition, the semantically mediated route for repetition was unreliable because semantic processing was faulty and S.M. could not accurately label concepts.     

You’re looking for what? Comparing search for familiar,nameable objects to search for unfamiliar,novel objects

Searching for items in one’s environment often includes considerable reliance on semantic knowledge. The present study examines the importance of semantic information in visual and memory search, especially with respect to whether the items reside in long-term or working memory. In Experiment 1, participants engaged in hybrid visual memory search for items that were either highly familiar or novel. Importantly, the relatively large number of targets in this hybrid search task necessitated that targets be stored in some form of long-term memory. We found that search for familiar objects was more efficient than search for novel objects. In Experiment 2, we investigated search for familiar versus novel objects when the number of targets was low enough to be stored in working memory. We also manipulated how often participants in Experiment 2 were required to update their target (every trial vs. every block) in order to control for target templates that were stored in long-term memory as a result of repeated exposure over trials. We found no differences in search efficiency for familiar versus novel objects when templates were stored in working memory. Our results suggest that while semantic information may provide additional individuating features that are useful for object recognition in hybrid search, this information could be irrelevant or even distracting when searching for targets stored in working memory.     

The update of semantic memories in amnestic mild cognitive impairment

It is still controversial to what extent neocortical consolidated memories are susceptible of change by processes of reconsolidation and transformation throughout experience, and whether the medial temporal lobes are necessary for this update of semantic consolidated memories, as they are for episodic remembering. We hypothesize that patients with amnestic mild cognitive impairment (aMCI) who have deficits in episodic memory may also have difficulties in updating information on added new features of objects. Sixteen participants with aMCI and 20 healthy control participants performed a semantic word-to-picture task, in which they were asked to identify as belonging to a given semantic category NEW objects, that have incorporated novel features, as well as OLD items, semantically and visually SIMILAR items and UNRELATED items. Patients with aMCI made a greater percentage of errors than healthy controls. Participants globally made greater percentages of errors in difficult types of items, namely NEW and SIMILAR, as compared to easier ones, OLD and UNRELATED. Importantly, an item by diagnostic group interaction effect was observed, and post hoc analysis showed that patients with aMCI made a higher percentage of errors than controls in NEW items only. In conclusion, patients with aMCI had a particular difficulty in identifying the NEW items of the word-to-picture task as compared to the control participants, supporting the concept of a flexible and dynamic conceptual knowledge system, involving the update of semantic memories and the integration of new attributes in a constant transformation process, which is impaired in these patients.     

The role of context on boundary extension

Boundary extension (BE) is a memory error in which observers remember more of a scene than they actually viewed. This error reflects one’s prediction that a scene naturally continues and is driven by scene schema and contextual knowledge. In two separate experiments we investigated the necessity of context and scene schema in BE. In Experiment 1, observers viewed scenes that either contained semantically consistent or inconsistent objects as well as objects on white backgrounds. In both types of scenes and in the no-background condition there was a BE effect; critically, semantic inconsistency in scenes reduced the magnitude of BE. In Experiment 2 when we used abstract shapes instead of meaningful objects, there was no BE effect. We suggest that although scene schema is necessary to elicit BE, contextual consistency is not required.     

Naming without knowing and appearance without associations: Evidence for constructive processes in semantic memory?

Abstract

This study describes a patient (SE) with temporal lobe injury resulting from Herpes Simplex Encephalitis, who displayed a previously unreported impairment in which his knowledge of associative and functional attributes of animals was disproportionately impaired by comparison with his knowledge of their sensory attributes (including their visual properties and characteristic sounds). His knowledge of man-made objects was preserved. A striking aspect of the present case was that the patient remained able to name many animals from their pictures, despite making gross errors in generating associative information about these same animals. This suggests that a semantic representation incorporating stored sensory knowledge may be sufficient for naming (at least for biological categories) and associative information may be unnecessary. Semantic knowledge may normally incorporate more information than is necessary for identification. SE's errors were found to be confabulatory and reconstructive in nature and it is argued that this aspect of his performance challenges passive conceptions of semantic memory couched in terms of a catalogue of stored representations. It is proposed that the patient's disorder affects a dynamic, constructive, and inferential component of his knowledge base, and that this component is sensitive to semantic category.     

Category specificity in normal episodic learning: applications to object recognition and category-specific agnosia

Studies of patients with category-specific agnosia (CSA) have given rise to multiple theories of object recognition, most of which assume the existence of a stable, abstract semantic memory system. We applied an episodic view of memory to questions raised by CSA in a series of studies examining normal observers' recall of newly learned attributes of familiar objects. Subjects first learned to associate arbitrarily assigned colors or textures to objects in a training phase, and then attempted to report the newly learned attribute of each object in a recall task. Our subjects' pattern of recall errors was similar both quantitatively and qualitatively to the identification deficits among patients with CSA for biological objects. Furthermore, errors tended to reflect conceptually and structurally based confusions. We suggest that object identification involves recruitment and integration of information across distributed episodic memories and that this process is susceptible to interference from objects that are structurally similar and conceptually related.     

Mechanisms for accessing lexical representations for output: evidence from a category-specific semantic deficit

We report the performance of a neurologically impaired patient, JJ, whose oral reading of words exceeded his naming and comprehension performance for the same words--a pattern of performance that has been previously presented as evidence for "direct, nonsemantic, lexical" routes to output in reading. However, detailed analyses of JJ's reading and comprehension revealed two results that do not follow directly from the "direct route" hypothesis: (1) He accurately read aloud all orthophonologically regular words and just those irregular words for which he demonstrated some comprehension (as indicated by correct responses or within-category semantic errors in naming and comprehension tasks); and (2) his reading errors on words that were not comprehended at all (but were recognized as words) were phonologically plausible (e.g., soot read as "suit"). We account for these results by proposing that preserved sublexical mechanisms for converting print to sound, together with partially preserved semantic information, serve to mediate the activation of representations in the phonological output lexicon in the task of reading aloud. We present similar arguments for postulating an interaction between sublexical mechanisms and lexical output components of the spelling process.     

Are semantic errors actually semantic?: Evidence from alzheimer's disease

Patients with Alzheimer's disease (AD) produce a high rate of semantic errors when naming to confrontation. This is considered to be one of the many consequences of their semantic memory deficit. However, it has been shown, in aphasic patients with focal lesions, that semantic errors could arise from impairment to any one of the levels in the naming process. To check this hypothesis in AD, we assessed in 15 patients the capacity to name and access semantic knowledge (by multiple-choice probe questions) about 14 objects presented successively in the visual, tactile, auditory, and verbal modalities. In the visual naming task, 33 errors were recorded: 26 (78.8%) were semantic and 7 (21.2%) were unrelated errors. Of the 26 semantic errors, 8 were related to a deficit of the semantic knowledge related to the item and 17 to a deficit in the retrieval of the phonological form of the word. One was associated with a deficit of access to semantic knowledge in the visual modality. The 7 unrelated errors were associated with a loss of semantic knowledge for 4 and deficit of access to the phonological form for 3. In conclusion, this study shows that semantic errors do not systematically reflect a deficit of semantic knowledge in Alzheimer's disease. It also seems that unrelated errors are more frequently related to semantic deficits than semantic errors in this population.     

逆行性遗忘、额叶与远期记忆的组织

通过对一例严重记忆障碍合并额叶损伤病人的逆行性遗忘的分析,对远期记忆的组织特点进行了探讨。被试的额叶功能受损较为明显。除顺行性遗忘外,患者的逆行性遗忘也较为严重。对病人进行的逆行性遗忘检测包括：著名人物测验、著名事件、一般知识测验和自传性记忆测验等。被试对著名人物、著名事件的回忆和再认成绩、以及有关个人的情节和语义记忆成绩均较低,但没有典型的随时间下降的趋势,而是呈平直斜率;患者儿童期的自传性记忆和公众事件记忆也受损。这两个特点均与内侧颞叶一间脑系统损伤的特点不同,提示额叶参与了远期记忆的提取等过程。     

The effects of acoustic and semantic similarity on concept identification

Since both acoustic and semantic similarity exert an influence on memory, the role of memory in concept identification (CI) was investigated by varying the acoustic and semantic similarity of the stimuli used in the CI task. Varying acoustic similarity had no effect on CI, but CI was significantly impaired when the dimensions of a CI task were semantically similar.     

Episodic and semantic memory influences on picture naming in Alzheimer's disease

This study investigated the relationship between semantic and episodic memory as they support lexical access by healthy younger and older adults and individuals with Alzheimer's disease (AD). In particular, we were interested in examining the pattern of semantic and episodic memory declines in AD (i.e., word-finding difficulty and impaired recent memory) vis-à-vis more preserved remote memories. We administered a picture naming task in which the episodic period of the pictures and whether the pictured items were unique to one period or commonly used across periods were varied. Groups of younger adults (N=40), healthy older adults (N=20) and older adults with AD (N=18) were asked to name drawings of objects in four conditions: dated unique, contemporary unique, dated common, and contemporary common. The results indicated that all participants named items that were common to both episodic periods more successfully than items unique to one period. An interaction was observed such that the healthy older and AD groups were more successful in retrieving names of objects presented in the dated compared to contemporary unique conditions, whereas the younger adults showed the reverse pattern. These results indicate that naming ability is affected both by the cumulative frequency of using an item over a lifetime and by when an item was first acquired. The findings support a theoretical stance which proposes an enduring reciprocal link between semantic and episodic memory. This theoretical relationship has practical implications for the development of intervention strategies when interacting with persons who have AD.     

Effects of semantic cues on mathematical modeling: Evidence from word-problem solving and equation construction tasks

Mathematical solutions to textbook word problems are correlated with semantic relations between the objects described in the problem texts. In particular, division problems usually involve functionally related objects (e.g., tulips-vases) and rarely involve categorically related objects (e.g., tulips-daisies). We examined whether middle school, high school, and college students use object relations when they solve division word problems (WP) or perform the less familiar task of representing verbal statements with algebraic equations (EQ). Both tasks involved multiplicative comparison statements with either categorically or functionally related objects (e.g., "four times as many cupcakes [commuters] as brownies [automobiles]"). Object relations affected the frequency of correct solutions in the WP task but not in the EQ task. In the latter task, object relations did affect the structure of nonalgebraic equation errors. We argue that students use object relations as "semantic cues" when they engage in the sense-making activity of mathematical modeling.     

How semantic organisation influences primary school children’s working memory

The present study focuses on the semantic organisation of material in working memory. We developed a new measure in which students memorised unrelated words from lists. In our study, we manipulated the association between words in the lists. The material was organised so as to elicit a semantic organisation (categorical and thematic). The task was then administered to a group of 6–10-year-old children. The semantic organisation of the material prompted a better recall, which depended on the type of semantic organisation. In the same vein, the number of intrusion errors was influenced by the semantic links between words and was higher when words in the list were associated categorically. These results seemed to depend partly on the participants’ age, being evident only in the younger children.     

False working memories? Semantic distortion in a mere 4 seconds

False memories are well-established, episodic memory phenomena: Semantically related associates are confidently and erroneously remembered as studied items. We report four experiments yielding similar effects in a working memory paradigm. Four semantically related words were retained over a brief interval. Whether or not the interval was filled with a math verification task, semantically related lures were mistakenly recognized as members of the memory set and took longer to reject than did unrelated negative probes. In a short-term recall task, semantic intrusions exceeded other errors (e.g., phonemic). Our results demonstrate false memory effects for a subspan list when a mere 4 sec was given between study and test. Such rapid semantic errors presumably result from associative processing, may be related to familiarity-based proactive interference in working memory, and are consistent with recent models that integrate short- and long-term memory processes.     

Aging and the intrusion superiority effect in visuo-spatial working memory

This study investigated the active component of visuo-spatial working memory (VSWM) in younger and older adults testing the hypotheses that elderly individuals have a poorer performance than younger ones and that errors in active VSWM tasks depend, at least partially, on difficulties in avoiding intrusions (i.e., avoiding already activated information). In two experiments, participants were presented with sequences of matrices on which three positions were pointed out sequentially: their task was to process all the positions but indicate only the final position of each sequence. Results showed a poorer performance in the elderly compared to the younger group and a higher number of intrusion (errors due to activated but irrelevant positions) rather than invention (errors consisting of pointing out a position never indicated by the experiementer) errors. The number of errors increased when a concurrent task was introduced (Experiment 1) and it was affected by different patterns of matrices (Experiment 2). In general, results show that elderly people have an impaired VSWM and produce a large number of errors due to inhibition failures. However, both the younger and the older adults' visuo-spatial working memory was affected by the presence of activated irrelevant information, the reduction of the available resources, and task constraints.     

A motor isolation effect: When object manipulability modulates recall performance

Previous studies suggested that the language production architecture is recruited during verbal retention, and others proposed that spatial memory relies on the oculomotor system. The objective of the present study was to investigate the role of the motor system in object memory, by examining the effect of objects' affordances on retention. In a serial recall task, we manipulated the manipulability of objects to retain in memory. We used an isolation paradigm where we isolated the manipulability level of one object from the list. We showed that recall performance improved for the isolated object (Experiment 1) and that this advantage was abolished when participants were required to perform motor suppression during the task (Experiment 2). In Experiment 3, we showed that the abolition of the motor isolation effect in Experiment 2 was not due to an effect of distraction since motor suppression was shown not to interfere with a semantic isolation effect. It is argued that motor affordances play a role in object memory, but only when the motor characteristics of an object allow discriminating it from the other objects in the list.     

Decline in working memory updating through ageing: intrusion error analyses

The present research examines the decline in working memory updating through age. Two experiments compared groups of participants in different age ranges (young-old, 55-65 years, old, 66-75 years and old-old, more than 75 years and, in Experiment 2 only, young, 20-30 years). Memory updating tasks were administered, which required participants to remember the smallest items in each list. To perform the task correctly, participants had to update information efficiently, reducing interference from items no longer relevant. Intrusion errors were computed and in the first experiment these were described as "intrusions of irrelevant items" (immediate exclusion) and "intrusions of once relevant items" (delayed exclusion). The oldest adults performed worse in memory updating and made a greater number of intrusion errors of once relevant information. In the second experiment results showed that increases in memory load (number of items that had to be remembered) and updating demand (number of potentially relevant items) impaired performance. The oldest adults had greater difficulty when the task demand was increased. Furthermore, they produced a higher number of intrusion errors, particularly when the updating demand was increased. It therefore appears that elderly people have specific difficulty in updating information in working memory by excluding irrelevant information.     

The deterioration of semantic memory in Alzheimer's disease.

Semantic memory impairment is a common feature of dementia of the Alzheimer type (DAT). Recent research has shown that patients with DAT are more impaired (relative to non-demented controls) in generating exemplars from a particular semantic category (e.g., animals) than words beginning with a particular letter, exhibit an altered temporal dynamic during the production of category exemplars, are impaired on confrontation naming tasks and make predominantly superordinate or semantically related errors, consistently misidentify the same objects across a variety of semantic tasks, and have alterations in multi-dimensional scaling models of their semantic network that are indicative of a loss of concepts and associations. These results are consistent with the view that Alzheimer's disease results in a breakdown in the organization and structure of semantic knowledge as neurodegeneration spreads to the association cortices that presumably store semantic representations.     

Dimension-based working memory-driven capture of visual selection

We studied attentional capture by dimensional cueing of visual objects. Participants received two dimension cues, one relevant for a memory test and the other relevant for an attention test. Performance in the attention task was impaired on incongruent trials (i.e., when the relevant dimensions for memory and attention did not match) relative to congruent trials. Dimensional cueing effects were enhanced when the cued dimension was held “online” in working memory through the trial, compared to when the cued dimension did not have to be held in memory. The findings demonstrate that dimensional cueing of visual selection can occur in a largely automatic manner, with working memory exerting a strong modulatory influence. We discuss the implications of these findings for understanding the interaction between memory and attention.