CT scan and neuropsychological correlates of Alzheimer's disease and Huntington's disease

"Cortical" and "subcortical" dementia syndromes differ in areas of primary neuropathology and clinical characteristics. Conventional CT scan interpretation, visual inspection of pictures, has not been useful in studying dementia. Recent studies of the digitally stored CT attenuation values have found systematic variations with normal aging and aphasia subtypes. In this study of numerical CT scan information in four Alzheimer's Disease and two Huntington's Disease patients, a double dissociation of frontal and temporal lobe density values was found, and a significant correlation was found between left temporal lobe density and verbal ability measures in the Alzheimer's Disease patients.     

Altered patterns of word associations in dementia and aphasia

The word associations of 38 demented, 17 aphasic, and 22 normal subjects were studied. Both normal and brain-injured subjects appear to make judgments about the grammatical class of the word stimulus. Certain stimulus words (especially nouns and adjectives) elicit paradigmatic responses whereas other words (especially verbs and adverbs) elicit syntagmatic responses. The mechanism producing syntagmatic responses seems relatively resistant to deterioration in dementia or aphasia. However, in dementia the mechanism that generates paradigmatic responses becomes progressively less efficient (possibly due to a loss of semantic markers) and consequently more random (idiosyncratic) responses emerge. Perseverative responses, inhibited in normal subjects, are more prevalent in dementia. Anomic aphasics show a pattern of word associations similar to that of subjects with mild dementia. Broca's aphasics, while making fewer paradigmatic associations than normals, retain enough self-monitoring mechanisms so that few idiosyncratic and perseverative responses are made while more null responses occur. Wernicke's aphasics show a marked shift away from a paradigmatic word association strategy, possibly due to an inability to access semantic markers or a true loss of these markers. Metalinguistic deficits (i.e., a failure to adopt an appropriate strategy) may also contribute to this shift away from paradigmatic associations. Furthermore, a disruption of self-monitoring mechanisms in Wernicke's aphasia leads to an increase in perseverative and idiosyncratic responses.     

Neurolinguistic analysis of verbal utterances in patients with focal lesions of frontal lobes

Verbal utterances of 105 patients have been analyzed. Six groups of subjects were examined including patients with left dorsolateral frontal lesions, left orbitofrontal lesions, right frontal lobe lesions, posterior aphasics, posterior brain-damaged patients without aphasia, and a matched control group. Results indicate that the left frontal lobe is involved in organization of linguistic information. Its dorsolateral part seems to be concerned with forming the sequential pattern of an utterance, and the orbital part with the directed development of a narrative. It is conceivable that the right frontal lobe is important for the global, nonlinguistic organization of information to be uttered.     

额叶在启动效应中的作用机制：对额叶损伤病人颜色命名和词命名任务的分析

以额叶损伤病人为被试,探讨在知觉型联想启动和知觉启动中,额叶的作用及其内在机制。实验任务包括颜色命名和词命名任务,以及相应的再认任务。结果表明,额叶损伤病人在颜色命名和词命名任务中,对旧词和重组颜色词的命名时间都没有明显差别,联想启动和颜色启动效应受损,但轻度记忆损伤病人与正常对照组之间的再认成绩相似。相关分析发现联想启动和颜色启动与额叶的多项功能有中度相关。这表明,额叶参与了知觉型联想启动效应和知觉启动,并且与其抑制和注意等执行功能有关。     

Turn-taking and speech act patterns in the discourse of senile dementia of the Alzheimer's type patients

Conversational discourse patterns of 11 normal elderly and 11 senile dementia of the Alzheimer's type (SDAT) patients engaged in dyadic interaction with an examiner were examined. Differences in word usage, turn taking, and speech act production were investigated both for the two-subject groups and for the examiner's conversations with each group. Compensatory shifts in discourse by participants are identified. For the subject, differences were shown on words per turn with SDAT subjects speaking in shorter turns and in nonverbal responses with SDAT subjects using this strategy more frequently. Speech act categories of Requestives and Assertives also differed with SDAT subjects using more Requestives and fewer Assertives. The SDAT subjects had significantly more occurrences of unintelligible utterances. For the examiner, words per turn differed with the examiner using shorter turns with SDAT subjects. No differences were shown in the examiner's patterns of speech act usage, nonverbal responses, or intelligibility. In general, these results indicate significant discourse differences in the words per turn level for all participants and speech act levels of conversation for SDAT subjects. They also indicate generally maintained interaction patterns by speakers so that the discourse genre of conversation is sustained. The pattern of compensatory shifts in discourse suggests retained flexibility in the communication system of early and mid stage SDAT patients.     

Phrenological studies of aphasia before Broca: Broca's aphasia or Gall's aphasia?

The history of aphasia is usually taken to begin with Broca's (1861a,b) discovery of the correlation of aphemia with damage to the posterior inferior portion of the frontal lobes and the subsequent relation to left hemisphere. That there were prior, even biblical, references to aphasia is not in dispute, nor that, according to Benton and Joynt (1960), almost all the clinical forms of aphasia had been described prior to 1800. The significance of Broca's case studies, therefore, lies in the association of motor aphasia with focal pathology in the frontal lobe. This paper examines the status of aphasia localization prior to Broca, and, specifically, the extent to which Broca's discovery may have been anticipated by the phrenologists.     

额叶参与对新异联系的启动效应——来自脑损伤病人的证据

对新异联系的启动效应是内隐记忆的一种形式,又称联想启动。采用知觉辨认任务,探讨额叶损伤与联想启动的关系。25例额叶损伤病人及18例匹配的正常被试参与实验。结果表明,额叶受损病人辨认旧词对与重组词对的正确率没有明显差别;而且,轻度记忆损伤的额叶病人再认成绩正常,但联想启动值低于对照组,内隐记忆和外显数、坚持性反应数和语词流畅性等有中度相关。这些结果提示,额叶不仅与情节记忆、工作记忆等外显记忆有关,也参与了以非相关词对为材料的联想启动。     

Affective aprosodia from a medial frontal stroke

BACKGROUND AND OBJECTIVES: Whereas injury to the left hemisphere induces aphasia, injury to the right hemisphere's perisylvian region induces an impairment of emotional speech prosody (affective aprosodia). Left-sided medial frontal lesions are associated with reduced verbal fluency with relatively intact comprehension and repetition (transcortical motor aphasia), but persistent affective prosodic defects associated with right medial frontal lesions have not been described. METHODS: We assessed the prosody of a man who sustained a right medial frontal cerebral infarction seven years prior. RESULTS: While propositional speech expression was normal including syntactic prosody, the patient was impaired at expressing emotions using prosody. His comprehension and repetition of prosody were also impaired but less so than expression. CONCLUSIONS: Right medial frontal lesions can induce an affective aprosodia that primarily impairs expression.     

Implications of memory and language dysfunction in the naming deficit of senile dementia

Young normals, elderly normals, and patients with either mild-to-moderate or severe senile dementia of the Alzheimer type (SDAT) were administered several tests of language function and remote memory. On all of the language tests examined, elderly normals exhibited a mild, nonsignificant performance decrement relative to the young normals. Advanced SDAT patients were markedly impaired on all of the tests. Early dementia patients were most impaired, relative to aged normals, on tests of object naming, category instance fluency, and remote memory. The deficit was smaller on the WAIS vocabulary subtest, on selecting the name of a visually presented object, and on recalling the function of an object. Early SDAT patients were least impaired in selecting the picture of an object after its name had been provided and in selecting objects that belong to a specified functional category. The results are consistent with the notion that the language dysfunction in early SDAT is due to a deficit in semantic memory function in which general, categorical information remains available whereas information about specific attributes becomes less accessible. The object naming test might be useful in the assessment of treatment effects upon SDAT because of its sensitivity and specificity to dementia, its high face validity, and its independence of recent memory.     

Memory and executive function impairments after frontal or posterior cortex lesions

Free recall and recognition, memory for temporal order, spatial memory and prospective memory were assessed in patients with frontal lobe lesions, patients with posterior cortex lesions and control subjects. Both patient groups showed equivalent memory deficits relative to control subjects on a range of free recall and recognition tasks, on memory for temporal order and on a prospective memory task. The patient groups also performed equivalently on the spatial memory task although only patients with frontal lobe lesions were significantly impaired. However, the patients with frontal lobe lesions showed an increased false alarm rate and made more intrusion errors relative not only to the control subjects, but also to the patients with poster or cortex lesions. These memory problems are discussed in relation to deficits in executive function and basic memory processes.     

Picture-naming in aphasia

The distribution of picture-naming errors for Broca's aphasics (n = 9), Wernicke's aphasics (n = 9), conduction aphasics (n = 9), frontal anomics (n = 7), and posterior anomics (n = 9) was examined to determine the diagnostic power of error types in picture-naming. Negated responses were associated with Broca's aphasia, whole-part errors ("hose" for nozzle) were associated with frontal anomia, and poor phonemic cuing was associated with Wernicke's aphasia. In addition, the relative distribution of the three most prominent naming errors-phonemic errors, semantic errors, and multiword circumlocutions-tended to distinguish the two anomic subgroups from the other aphasia subgroups. Anomic aphasics produced the fewest phonemic errors and the most multiword circumlocutions; this pattern suggests minimal word-production difficulty in anomic aphasia relative to the other aphasia syndromes. Despite such group differences, the overall picture indicates that there is considerable similarity among aphasia syndromes in terms of picture-naming behavior.     

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。     

Writing errors by normal subjects

Writing is a complex process requiring visual memory, attention, phonological and semantic operations, and motor performance. For that reason, it can easily be disturbed by interfering with attention, memory, by interfering subvocalization, and so on. With 16 female third-year students (23.4 +/- 0.8 yr.) from the University of Trieste, we investigated the production of errors in three experimental conditions (control, articulatory suppression, and tapping). In the articulatory suppression condition, the participants produced significantly more linguistic impairments (such as agrammatism, unrelated substitutions, sentence omissions, and semantically deviant sentences), which are similar to linguistic impairments found in aphasia. On the tapping condition there were more perseverations, deletions, and substitutions of both letters and words. These data suggest that writing is not an automatic skill. Only after many years of experience and practice of processing information (through cortical to subcortical channels) can writing be considered an automatic skill. Limited experimental conditions can disrupt the writing system of normal subjects, probably interfering with the cortical to subcortical loops, and link normality to pathology.     

Effects of level of retrieval success on recall-related frontal and medial temporal lobe activations

Brain dedicated single photon emission computed tomography (SPECT) was used to compare the neuroactivation produced by the cued recall of response words in a set of studied word pairs with that produced by the cued retrieval of words semantically related to unstudied stimulus words. Six of the 12 subjects scanned were extensively trained so as to have good memory of the studied pairs and the remaining six were minimally trained so as to have poor memory. When comparing episodic with semantic retrieval, the well-trained subjects showed significant left medial temporal lobe activation, which was also significantly greater than that shown by the poorly trained subjects, who failed to show significant medial temporal lobe activation. In contrast, the poorly trained subjects showed significant bilateral frontal lobe activation, which was significantly greater than that shown by the well-trained subjects who failed to show significant frontal lobe activation. The frontal activations occurred mainly in the dorsolateral region, but extended into the ventrolateral and, to a lesser extent, the frontal polar regions. It is argued that whereas the medial temporal lobe activation increased as the proportion of response words successfully recalled increased, the bilateral frontal lobe activation increased in proportion to retrieval effort, which was greater when learning had been less good.     

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.     

Implicit Memory and the Formation of New Associations in Nondemented Parkinson′s Disease Individuals and Individuals with Senile Dementia of the Alzheimer Type: A Serial Reaction Time (SRT) Investigation

Using the serial reaction time (SRT) task developed by Nissen and Bullemer (1987, Cognitive Psychology, 19, 1–32), implicit memory performance was examined in four groups of subjects: nondemented healthy aged individuals; nondemented Parkinson"s disease individuals; very mildly demented senile dementia of the Alzheimer type (SDAT) individuals; and mildly demented SDAT individuals. The SRT task involved four blocks of a repeated 10-item keypress sequence that tapped general skill development along with a fifth block of a nonrepeated sequence that presumably reflected the impact of switching from a learned set of associations (developed during the first four blocks) to a novel sequence. The increase in response latency from the fourth repeated block to the fifth nonrepeated block was used as the reflection of implicit learning. The results revealed preserved implicit memory performance in the very mildly demented individuals compared to that of the age-matched control individuals. However, the mildly demented SDAT individuals and the nondemented Parkinson"s disease individuals showed reliably less implicit learning, compared to the age-matched control individuals. Differences between the past studies using the SRT task to tap implicit memory performance in SDAT individuals and the present study are discussed in some detail. We conclude that nondemented Parkinson"s disease individuals and mildly demented SDAT individuals produce some deficit in the formation of new associations in implicit memory, as measured by the SRT task.     

Sequential response bias in randomized response sequences: A computer simulation

In this study sequential bias in randomized response sequences is simulated by computer. The computer model assumes that response bias is composed of two components. The first is a repetition avoidance tendency, which is simulated by a memory search through the seven most recently produced responses, and the second is a repetition tendency for the two most recently produced responses. This repetition tendency is assumed to be related to the better availability of recently produced responses. Both processes together give a reasonable approximation of human subjects' data.The results can be explained by the assumption that subjects try to control perseveration tendencies by using a comparison-based memory search mechanism.     

Semantic priming effects, lexical repetition effects, and contextual disambiguation effects in healthy aged individuals and individuals with senile dementia of the Alzheimer type

An experiment is reported that addresses semantic priming effects, lexical repetition effects, and the influence of context on meaning selection for ambiguous words in 32 healthy aged individuals and 32 individuals with Senile Dementia of the Alzheimer Type (SDAT). On each of 232 trials, subjects pronounced each of three words. The four major conditions were concordant (music-organ-piano), discordant (kidney-organ-piano), neutral (ceiling-organ-piano), and unrelated (kidney-ceiling-piano). In order to address lexical repetition effects, target words were repeated across Blocks 1 and 2 but not in Block 3. Analyses of naming latencies indicated that semantic priming effects and lexical repetition effects were slightly larger in SDAT individuals than in healthy aged individuals. More importantly, healthy aged individuals produced normal selective access of the contextually biased meaning whereas SDAT individuals produced evidence consistent with nonselective meaning access. These results are discussed within both an attentional and a connectionist account of homograph disambiguation.