Encoding specificity in the alcoholic Korsakoff patient

A previous attempt to improve amnesic Korsakoff patients' retention of individual words resulted in only moderate improvement and, then, only under restricted conditions. It appeared that this occurred because the patients “forget” the instructed analysis of the word as well as the word itself. Consequently, the two experiments reported here sought to provide feature (Experiment 1) or associated (Experiment 2) cues at both input and output. In this manner relatively good performance was obtained, but only when semantic cues were “strongly” associated to the target words. Implications for an encoding specificity interpretation are drawn from these results.     

Recall failure following successful generation and recognition of responses by alcoholic Korsakoff patients

Amnesic Korsakoff patients and controls were presented with twelve words, each shown individually in the presence of a weak associate. They were then asked to freely associate to 12 other words that were strong associates of the to-be-remembered (TBR) words. The Korsakoff patients generated, and were able to recognize, as many of the TBR words as the controls. Yet, in spite of this recognition ability, these same patients were subsequently unable to recall the critical TBR words when the weak cues were again presented. A follow-up study found that the same recognition results could be obtained with Korsakoffs months after initial presentation suggesting that the patients might initially have “recognized” the most highly associated words simply because they represented the most probable choices. Intermediate association prompts failed to generate correct responses. It was hypothesized that the Korsakoff patients cannot restructure their semantic associative hierarchy during input in such a way as to become sensitized to other than the strongest associates as prompts during recall.     

Speech prosody in Broca's aphasia

Because speech prosody is thought to be impaired in Broca's aphasia, we conducted three experiments using Broca's aphasics and nonneurological control subjects in order to determine to what extent this statement is accurate. Using three acoustic measures of speech prosody—sentence-final fundamental frequency (F₀) fall, F₀ declination, and sentence-final lengthening—we found that some aspects of prosody were spared while others were abnormal. All Broca's aphasics, regardless of degree of impairment, exhibited sentence-final F₀ fall. F₀ declination was present in simple sentences but was absent over longer domains; moreover, the amount of declination was correlated with the degree of linguistic impairment. Sentence-final lengthening was clearly absent in Broca's aphasia; in fact, sentence-terminal words were actually shorter than their sentence-initial and medial counterparts.     

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.     

Verbal retention deficits in aphasic and amnesic patients.

Five different groups of patients (aphasics, alcoholic Korsakoffs, nondominant hemisphere patients, alcoholics, and control patients) were asked to detect either repeated letters, repeated words, rhyming words, or words from the same category during the reading of a list. It was discovered that the number of intervening words had a greater effect on the aphasics for all conditions than it did for the other groups. However, when the rate of presentation was slowed, the aphasics showed considerable improvement while the other groups maintained their same level of performance. The Korsakoff patients were impaired only on the semantic task (same category inclusion) and did not improve at the slower presentation rate. An interpretation based on speed and level of information processing abilities is given.     

Mechanisms underlying writing and speech in aphasia

As a parallel to the dual decoding concept for processing of written language we proposed that phonological encoding does not necessarily occur in writing and that the phonemic and graphemic subsystems can be independent on the one-word level. This hypothesis was tested by comparing oral and written performance in a picture-naming task in Broca's and Wernicke's aphasics. In addition, the residual tacit knowledge of the orthographic properties of the names of the pictures was examined with a multiple-choice recognition task. The principal finding is that Broca's aphasics who were better in written than in oral naming showed more graphemically and semantically motivated errors than aphasics who were better in oral than in written naming, the latter producing more phonemically motivated errors. This result supports the dual encoding concept for writing on the singleword level, implying a direct route from the mental lexicon to the graphemic system in parallel with a route mediated by the phonemic system. Multiple-choice recognition was found to be superior to both oral and written performance in both Broca's and Wernicke's aphasics.     

Preservation of orthographic knowledge in aphasia

A simple untimed lexical decision task was designed to test implicit letter recognition in aphasic patients. Half of the nonwords used in this task were orthographically regular pronounceable pseudowords, and half were orthographically irregular unpronounceable letter strings. Twenty-five randomly chosen aphasic patients with mild to severe degrees of aphasia participated in the study. Although only six of the patients performed the lexical decision task successfully, all 25 demonstrated the ability to distinguish orthographically regular from irregular letter strings and, by implication, the ability to recognize and make use of the identities of written letters.     

Alcoholic Korsakoff patients' retrieval from semantic memory

Alcoholic Korsakoff patients' rate of retrieval from semantic memory was investigated. It was found that their rate of retrieval from “lexical” semantic memory was nearly normal, but their rate of retrieval from “conceptual” semantic memory was impaired. In addition, an attempt to “prime” their lexical semantic memory by requesting the same category to be searched on adjacent trials met with failure. It was concluded that Korsakoff patients' lexical storage is probably organized normally, but their conceptual organization is not. Parallels with these patients' episodic memory impairments are discussed and possible interactions between episodic and semantic memory are proposed.     

Sensitivity to lexical denotation and connotation in brain-damaged patients: A double dissociation?

Sets of words can be grouped in terms of their denotation (cold and warm both refer literally to temperature) or in terms of their connotation (cold and warm connote remoteness and intimacy, respectively). To assess whether these two facets of meaning are dissociable, unilaterally left- and right-hemisphere-damaged patients were presented with word triads and asked to group together the two words that were closest in meaning. Right-hemisphere-damaged patients showed a preserved sensitivity to denotation, and a selective insensitivity to connotative facets of meanings. In contrast, left-hemisphere-damaged patients exhibited a preserved sensitivity to connotation as well as a selective insensitivity to denotative aspects of meanings. Inasmuch as normal control subjects displayed a flexible sensitivity to both denotative and connotative aspects of meaning, the results suggest that unilateral brain damage selectively curtails use of one or the other major aspect of word meaning.     

The role of the right hemisphere in the apprehension of complex linguistic materials

To secure information on which aspects of linguistic functioning might be mediated by the nondominant hemisphere, a test battery assessing sensitivity to narrational and humorous materials was administered to a population of right-hemisphere-damaged patients, as well as relevant control groups of normal, aging, and aphasic individuals. While elementary linguistic functioning was adequate, the right-hemisphere-injured groups exhibited consistent difficulties in respecting the boundaries of a fictive entity, assessing the plausibility of elements within a story or joke, selecting the appropriate punch line for a joke, and integrating elements of a story into a coherent narrative. Certain elements—specifically emotional content and noncanonical facts injected into a narrative—also posed characteristic difficulties for these patients. The results suggest that, in contrast to the other populations, right-hemisphere patients exhibit special difficulties in processing complex linguistic entities and in utilizing the surrounding context as they assess linguistic messages.     

Time for auditory processing of object names by aphasics

Ten Wernicke's and ten Broca's aphasics were compared with normal controls and brain-damaged nonaphasics with respect to the time required for the auditory decoding of object names. This value was obtained by using a subtraction method with two reaction time determinations, one of which included an auditory processing phase while the other did not. The overall mean of approximately 200 msec for Broca's aphasics did not differ significantly from the normal, while the mean of 650 msec for the Wernicke aphasics was much slower. All groups responded more quickly to high-frequency than low-frequency words and all but the Wernicke aphasics improved in the second trial block over their performance in the first trial block.     

Reversal operations after brain damage

The ability to perform reversals—that is, the appreciation of the relationship between original and transformed states of knowledge—is critical to human thought processes. In order to assess whether a number of “special-purpose processors” are responsible for reversal operations, depending on the particular context in which the reversal is couched, or whether a single “core processing mechanism” subserves a critical aspect of reversal operations regardless of the specific context, patients with localized brain damage were asked to solve eight reversal problems. Visual and auditory reversals mediated by linguistic and non-linguistic symbol systems were presented. The findings demonstrate that patients with insult to the anterior portion of the right hemisphere encounter more difficulty performing reversals than patients with right posterior insult, Broca's aphasics, and fluent aphasics. This is regardless of the symbol system mediating the reversal, regardless of the modality of presentation, and regardless of the amount of available processing time. Subjects with insult to the posterior region of the left hemisphere or the right hemisphere also exhibit some difficulty solving reversal problems, although their difficulties appear modality specific. These data lend support to the claim that a core processing mechanism may play a critical role in the performance of reversal operations.     

The nature of the phonological disorder in conduction aphasia

Sequences of attempts to name pictured objects were used to examine phonological dysfunction in three diagnostic subgroups of aphasia. A prevalence of "phonologically-oriented sequences" (i.e., those sequences that contained only attempts with a phonological resemblance to the target word) was found to be a diagnostic criterion for conduction aphasia. When compared to a group of Broca's (n = 7) and Wernicke's (n = 5) aphasics, all the conduction aphasics (n = 6) produced proportionately more of such phonologically-oriented sequences on a picture naming test. An examination of the phonologically-oriented sequences produced by the conduction aphasics indicates that speech production in conduction aphasia involves dysfunction at an early stage of sound-encoding. The theoretical implications of this view are discussed.     

Quantitative CT scan studies in aphasia. I. Infarct size and CT numbers

Infarct si?e (number of 1-mm² pixels in the lesion) on CT scans of 30 aphasia patients was obtained with a semiautomated computer program. The mean number of lesion pixels present per slice containing lesion was approximately 500 for mild aphasias (transcortical motor and conduction), 700 for Wernicke's, 1000 for Broca's, 1500 for mixed, and 2000 for globals. These differences were significant for $\text{11}\text{15}$ of the group pairwise comparisons. When lesion locus was controlled for in the anterior/posterior plane, 73–100% of the aphasia patients were correctly classified as to type of aphasia by a discriminant analysis utilizing only the number of lesion pixels present on two CT slices. Different slice combinations were used for different aphasia group comparisons. There was a significant correlation between severity of aphasia and lesion size. There was a significant correlation between lesion size and the CT numbers in the lesion. This type of analysis may be useful to predict the prognosis for recovery potential in aphasics who have CT scans performed at 2 months poststroke.     

The relation between gesture and language in aphasic communication

Effective communication in aphasia depends not only on use of preserved linguistic capacities but also (and perhaps primarily) on the capacity to exploit alternative modalities of communication, such as gesture. To ascertain the capacity of aphasic patients to use gesture in their spontaneous communication, informally structured interviews were conducted with two Wernicke's aphasics and two Broca's aphasics, as well as with four normal controls. The performances of the patient groups were compared on the physical parameters of gesture, the points in the communication where gestures occurred, and several facets of the semantics and pragmatics of gesture. Generally speaking, the gestures of the aphasics closely paralleled their speech output: on most indices, the performance of the Wernicke's aphasics more closely resembled that of the normal controls. Wernicke's aphasics differed from normals in the clarity of their language and gestures: While individual linguistic units were often clear, the relation among units was not. In contrast, the Broca's aphasics equaled or surpassed the normal controls in the clarity of their communications. The results offer little support for the view that aphasic patients spontaneously enhance their communicative efficacy through the use of gesture; these findings can, however, be interpreted as evidence in favor of a “central organizer” which controls critical features of communication, irrespective of the modality of expression.     

Aphasics' selective deficits in appreciating grammatical agreements

This study attempted to dissociate in aphasic patients different aspects of grammatical capacity. Subjects were asked to evaluate sentences containing violations of agreements between pronouns and verbs. Agreements which are considered primarily structural in nature were violated (e.g., a surface object case like “them” placed in a surface subject sentential slot) while other violated agreements seemed to involve both structural and semantic information (e.g., lack of agreement between a pronoun and a verb in terms of the number of people performing the act). These violations were couched in one of three types of sentential frames which varied in terms of syntactic complexity (e.g., active declarative vs. passive syntactic voices). The results revealed that Broca's aphasics found agreement violations difficult to detect in complex syntactic frames. They were quite successful at detecting even violations of the largely structural “case” type of agreement, however, when couched in simpler syntactic frames. Fluent aphasics encountered more difficulty detecting violations of agreements involving both semantic and structural information than agreements which were primarily structural in nature, that is, regardless of the syntactic frame. These unique performance profiles suggest that Broca's aphasics may be agrammatic only with respect to certain aspects of a sentence's structure, and that fluent aphasics may also experience some selective—but different—grammatical deficits.     

Surprise but not coherence: Sensitivity to verbal humor in right-hemisphere patients

Verbal humor deficits were investigated in right-hemisphere-damaged patients. It was hypothesized that the appreciation of jokes presupposes two elements: sensitivity to the surprise element entailed in the punch line of a joke and apprehension of the coherence which results when the punch line has been integrated with the body of the joke. The possible dissociation between these elements was tested by asking subjects to select from four alternatives the appropriate ending to a joke. Right-hemisphere patients exhibited a selective attraction to endings which contained an element of surprise but which were not otherwise coherent with the body of the joke. This finding suggests that right-hemisphere patients have difficulty in integrating content across parts of a narrative and confirms the psychological reality of the proposed distinction between the surprise and coherence elements of humor processing.     

A note on temporal relations between language and gestures

The initiation of the spontaneous gestures of Wernicke's aphasics was analyzed in relation to shifts in semantic content between the syntactic boundaries of main clauses and embedded clauses. Gestures proved more likely to arise at the initial boundaries of embedded clauses when these were semantically discontinuous with the main clause than when these were semantically related to the main clause. Spontaneous gestures may signal underlying shifts in semantic intention, thereby reflecting the difficulties encountered by Wernicke's aphasics in maintaining a coherent stream of thought across syntactic boundaries.