Apractic agraphia in a patient with normal praxis

Most right-handed crossed aphasics are not apractic. They usually have agraphia characterized by misspellings but retain the ability to write well-formed graphemes. We describe a right-handed patient with a right parietal lesion who was aphasic and not apractic. He was unable to write any formed graphemes despite a relatively preserved ability to spell aloud. We postulate that praxis and writing are dissociated in this patient because the motor engrams for praxis were located in his left hemisphere and the engrams for writing were in his right hemisphere. In addition, he comprehended commands for limb motor activities (praxis) far better than he comprehended other speech. This suggests that in this patient the areas used to comprehend limb motor commands may be anatomically distinct from areas important in comprehending other aspects of speech.     

Regional cerebral blood flow patterns during verbal and nonverbal auditory activation

Current views of the relationship between audition and cerebral function suggest that increases in regional cerebral blood flow (rCBF) would occur in the superior, mid, and posterior portions of the temporal lobes, and that these changes would be more lateralized to the left hemisphere for a verbal than a nonverbal auditory task. We measured rCBF using the xenon inhalation technique in a group of healthy subjects during three conditions: (1) resting baseline, (2) auditory verbal activation (listening for word meaning), and (3) auditory nonverbal activation (listening for reduction of intensity in a series of noise bursts). Both verbal and nonverbal conditions produced highly significant increases in rCBF over the left posterior Sylvian region with a trend for verbal activation to evoke a wider area of flow increase than the nonverbal task.     

The advantages of mathematical modeling over traditional methods in the analysis of category clustering

A mathematical model for the analysis of category clustering is developed and testd. The model, which can be applied to categories of any size, is an extension of a two-item statistical model developed by Batchelder and Riefer (Psychological Review, 1980, 87, 375–397), and is equivalent to their model when categories consist of two items. The model is based on a current theory of clustering which postulates that the learning of a list of category items occurs on different hierarchical levels. Two category list-learning experiments are presented, and the data from these experiments are analyzed using the general statistical model. The first experiment reveals that the probabilities of storing and retrieving a cluster increase with category size, while the learning of items as singletons decreases. The effects of within-category spacing indicate that the storage of clusters decreases while cluster retrievability increases with an increase in input spacing. In the second experiment, the storage and retrieval of clusters are shown to be unaffected by whether the presentation of items is uncued or cued with the name of the category. However, the association of items decreases and the learning of items as singletons increases with uncued presentation. In the final sections, the general statistical model is compared to other methods for the measurement of category clustering. The model is shown to be superior to numerical indices of clustering, since these measures are not based on any theory of clustering, and because unitary measures cannot capture the multiprocess nature of categorized recall. The model is also argued to have certain advantages over other mathematical models that have been applied to category clustering, since these models cannot account for situations in which a portion of the items are clustered while others are learned singularly.     

Perceptual interference and hemispheric specialization

Two experiments evaluated the effect of stimuli presented at fixation on the recognition of faces or random shapes presented to the left or right visual half-field (VF). Increasing the processing demands of the center stimulus produced a large, linear decrease in recognition from both VFs for both faces and shapes. Recognition of random shapes was decreased more in the right visual field by center digits and in the left VF by center faces and shapes. In addition, interference was found between the VF faces and the center digits to the left of fixation. It was concluded that differences in the processing capacity of the two hemispheres are a function of the verbal-nonverbal nature of the stimuli at a later stage in processing but that the two hemispheres may also differ along other perceptual dimensions at an earlier stage of visual recognition.     

Shift of visual field preference for Hebrew words in native speakers learning to read

Lateralization for Hebrew words was tested in both the visual and auditory modalities in Israeli children learning to read their native language, Hebrew. A left visual field preference for tachistoscopically presented words was found in the second graders in contrast to a right visual field preference for the same words in the third graders. Children in both grades showed a right ear dominance for similar words presented dichotically. These data suggest right hemisphere involvement in acquiring reading skills of a native language.     

Cerebral lateralization in bilinguals: Methodological issues

The literature on lateralization for language in bilinguals manifests two apparent contradictions. Some papers demonstrate differences in lateralization between bilinguals and monolinguals; others demonstrate none. In studies with exclusively bilingual subjects, some papers demonstrate differences between the lateralization for the two languages, while others demonstrate none. This paper discusses the range of methodological parameters which must be borne in mind when conducting or evaluating studies of lateralization for language in bilinguals. These include issues of subject selection, language and stimulus selection, testing procedures, data analysis, and interpretation of results.     

Selective involvement of the auditory-verbal modality in an acquired communication disorder: Benefit from sign language therapy

A 39-year-old female suffered bitemporal infarctions and exhibited an unusual behavioral syndrome of muteness and impaired auditory comprehension, with milder aphasic deficits in reading and writing. The anatomic basis of this modality-selective communication disorder appeared to involve both peripheral perceptual and motor as well as “central” language mechanisms. The patient's ability to communicate was greatly aided by instruction in Amerind and Ameslan Sign Language, in which she learned more than 100 signs. Patients whose acquired language deficits spare modalities of input or output may be ideal candidates for sign language therapy.     

Hemispheric differences for verbal and nonverbal stimuli in Japanese- and English-speaking subjects assessed by Tsunoda's method

This investigation compared the performance of Japanese- and English-speaking subjects on T. Tsunoda's DAF key-tapping task, which he purports assesses cerebral dominance for language (1975, Brain and Language, 2, 152–170). Twenty-three native speakers of Japanese and 23 English-speaking subjects were employed in this study. Each subject was administered the DAF key-tapping task utilizing the vowel /a/ and a 1000-Hz pure tone. The results revealed an effect of intensity, whereby an increase in DAF/SAF ratios resulted in an increase in performance disruption. No differences were observed between the two language groups, ears, or between the 1000-Hz pure tone and the vowel /a/. Only 15.5% of the subjects showed the hypothesized right ear advantage for the tone when subjected to an analysis similar to Tsunoda's. All other subjects revealed variable degrees of advantage to either ear, to the same ear, or to to neither ear. It was concluded that no significant functional auditory asymmetry was observed for either group, suggesting that the DAF key-tapping task may not be a sensitive procedure to determine cerebral dominance for language among normals.     

Interhemispheric alpha asymmetry and imagery mode

Interhemispheric alpha activity was measured while subjects were engaged in covertly imaging familiar pictorial material using three imagery modes: “shapes and colors,” “words,” or both. The results showed suppression of alpha activity in the hemisphere which is primarily involved in the cognitive mode being used by the subject.     

The use of averaged electroencephalic response techniques in the study of auditory processing related to speech and language

This paper reviews a number of studies done by the authors and others, who have utilized various averaged electroencephalic response (AER) techniques to study speech and language processing. Pertinent studies are described in detail. A relatively new AER technique, auditory brainstem responses (ABR), is described and its usefulness in studying auditory processing activity related to speech and language is outlined. In addition, a series of ABR studies, that have demonstrated significant male—female differences in ABR auditory processing abilities, is presented and the relevance of these data to already established differences in male—female language, hearing, and cognitive abilities is discussed.     

Looking where you listen: visual cues and auditory attention

In the non-laboratory environment, we are generally able to see the source of the sounds to which we are attending. In a preliminary examination of how and to what degree we might use this visual information, subjects shadowed one of two female voices when able to see the persons speaking (Experiment I) or when able to see, and thus precisely localize, the auditory loudspeakers (Experiment II). Selective performance was improved by being able to see the lip movements of the people whose voices were heard, and by being able to localize visually the sources of the voices.     

Gestural impairment and gestural ability in aphasia: A review

Studies of gestural ability in aphasic subjects have found impairment of gestural expression and comprehension, with a close relationship between severity of aphasia and degree of gestural impairment. A few investigators have correlated gestural ability with specific language functions or subcategories of aphasia. Reading appears to correlate better with gestural recognition than does auditory comprehension. Despite the general findings of gestural impairment in aphasia, successes have been reported with gestural training including artificial language techniques, pantomime, Amerind, and American Sign Language. Future studies of gestural therapy in aphasia should examine specific language deficits in order to identify those aphasic individuals who can benefit from gestural training.     

The development of visual and auditory selective attention using the central-incidental paradigm

Analogous auditory and visual central-incidental learning tasks were administered to 24 second-, fourth-, and sixth-grade and college-age subjects to study the effects of modality of presentation on memory for central and incidental stimulus materials. There was no strong evidence to indicate that modality of presentation was an important factor in the development of selective attention. Central task learning increased with age for both auditory and visual presentations; incidental learning declined at the oldest age level for both auditory and visual tasks. The serial position analysis revealed that the observed developmental increase in recall performance was due primarily to differences in the initial serial positions. The use of active strategies for focusing attention on the relevant stimulus materials seemed to be the crucial determinant of level of performance.     

A comparison of dichotic and visuo-acoustic competition in hemispherectomized patients

Following hemispherectomy, patients performing dichotic listening tasks have great difficulty reporting items presented to the ear ipsilateral to their intact hemisphere. One possible cause is an attentional imbalance which, when competing inputs are received from both sides of space, restricts the patient's attention to the stimulus contralateral to his remaining hemisphere. If this explanation is true, then a similar ipsilateral ear decrement should occur when a competing visual stimulus is presented in the contralateral field. In the present study, however, hemispherectomy patients easily reported a digit presented to the ear ipsilateral to their intact hemisphere despite the concurrent presentation of a visual digit to their contralateral field.     

Prediction as a means of inducing tolerance

Female subjects were exposed individually to the attitude item responses of a similar or dissimilar stranger. They were asked either to copy down the stranger's attitudes or to predict (with accurate feedback) how the stranger answered each item. Predict subjects were found to be more tolerant of the dissimilar stranger than were Copy subjects, while both groups were equally attracted to the similar stranger. It was suggested that training people to anticipate disagreements may be a useful way of fostering tolerance.     

Some theorems in haploscopic vision

Three formal hypotheses are specified concerning the combination of neural signals from the two eyes. The hypotheses are (1) that a large uniform light presented to the opposite eye has no effect (independence), (2) that all information from one eye relevant to a given percept (for example, brightness) is encoded by a single neural signal (isolation), and (3) the mutually exclusive and exhaustive alternative to isolation (interaction). Though independence or isolation often has been claimed or simply assumed to hold, these hypotheses imply specific empirical relationships. These relationships are derived for brightness and for equilibrium colors. In addition, one model consistent with the interaction hypothesis is developed. The isolation hypothesis is important for generalizing results from monocular experiments to normal binocular vision. If it is false, monocular results can reflect a combination of one eye's neural signals that never occurs with binocular stimuli.     

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.