Crossed aphasia: analysis of four cases

Data from the Rehabilitation Institute of Chicago was used to contrast a sample of 358 aphasics with data from a Boston aphasia and aging study (L. Obler, M. Albert, H. Goodglass, and F. Benson, Brain and Language, 6, 318–322, 1978). Unlike the females, Chicago males showed remarkable similarity to the Boston male sample for the Broca, Wernicke, and Global groups with ratios of approximately four Broca's to every two Wernicke's and Global aphasics. Similar to the Boston Sample, Wernicke's aphasics were 11.6 years older (p < .001) than Broca's aphasics.     

Correlations of glucose metabolism and structural damage to language function in aphasia

Studies of aphasic patients using [18F]fluorodeoxyglucose positron computed tomographs have shown areas of metabolic depression in the left hemisphere larger than the area of infarction noted on CT. To evaluate these metabolic differences in relationship to language abnormalities, 11 patients had metabolic scans, CT, and were administered the Boston Diagnostic Aphasia Battery and the Porch Index of Communicative Ability. Correlation analyses were computed between metabolic, CT, and language data. CT demonstrated reliable correlations of speaking, oral reading, and repetition to Wernicke' area, consistent with current anatomic language models, while metabolic data from areas posterior, inferior, and superior to the traditional Wernicke's area and the head of the caudate nucleus also had reliable correlations with aphasic language function. The utilization of both structural and metabolic brain measures may improve our understanding of the anatomy of language as related to aphasia.     

Auditory evoked potentials and sex-related differences in brain development

Auditory evoked potentials (AEPs) were obtained to probe tones which were delivered during the presentation of complex verbal and nonverbal auditory stimulation to 3-month-old infants. Significant sex-dependent AEP amplitude asymmetries were found. Females produced higher-amplitude responses from the left hemisphere and males produced higher-amplitude responses from the right hemisphere during both the verbal and nonverbal presentations. No significant AEP asymmetries were obtained in an independent group of infants that received only the probe tones. These findings are consistent with theories and behavioral data suggesting differences between males and females in the development of language and spatial functions.     

The emergence of representation in search: Understanding the hider as an independent agent

Corrigan's results point the way toward a reconceptualization of how the development of representation affects search. The child does not cognitively recreate the invisible displacements of the object. Instead she seems to understand that the hider is an independent agent who can use simple hiding strategies that the child does not directly perceive. This representational skill for search, we propose, is one realization of a general representational capacity that emerges late in the second year. The general capacity is defined structurally as the ability to coordinate two sensorimotor systems into a single skill. Although there seem to be some discontinuities in the emergence of the representational capacity, its development is mostly gradual and continuous.     

Semantic aphasia: A neglected entity

Three cases of semantic aphasia are reported. Computerized brain tomography showed bilateral temporo-parieto-occipital junction hemorrhages in one patient, and left parieto-occipital junction infarctions in the other two patients. The auditory comprehension defect of the three patients was characterized by preserved understanding of single words and impaired understanding of grammatically complex constructions. It is suggested that this comprehension defect reflects an inability to fully grasp the meaning of words and grammatical constructions imbued with spatial or quasi-spatial significance. Each of the three patients showed a complex spatial disorder that included constructional apraxia, spatial agnosia, and elements of Gerstmann's syndrome. The aphasic as well as the spatial disorder of semantic aphasics may be manifestations of a common defect in the perception of spatial relationships produced by left temporo-parieto-occipital region damage.     

Numerical taxonomy of aphasia

Two hundred consecutively seen aphasics, 142 of them with infarcts, were examined by tests of fluency, comprehension, repetition, naming, and information content. The language scores were subjected to a minimum variance clustering algorithm separately for the total and for the infarct groups. The latter generated 10 clusters on a dendrogram. Attribute analysis of each cluster provided a clinically meaningful profile of language performance for these groups. The degree of correlation of most computer generated clusters with clinically recognized groups was high, and the homogeneity of some of the clusters is striking. An exception appears to be “conduction aphasia,” which is bimodally distributed. One of these clusters, with high fluency and low comprehension scores, was renamed “afferent conduction” aphasia, and the other, with lower fluency and higher comprehension, was renamed “efferent conduction” aphasia. The Principal Components Analysis was used to evaluate the discriminatory value of language characteristics, and the Nearest Neighbor Network Analysis was used to evaluate the significance of clustering. The dendrogram for all aphasics showed a less specific and less homogenous six clusters.     

Language lateralization and handedness: Estimates based on clinical data

The suggestion that the cerebral representation of language is bilateral in at least some left handers relies on using the proportion of aphasics found in available clinical samples of sufferers of unilateral brain damage as a valid estimate of the probability that aphasia will occur following unilateral brain damage. This results in an overestimate of this probability since the clinical sample includes only cases with both unilateral brain damage and clinical symptoms and excludes cases with unilateral brain damage without clinical symptoms. With adjustment for this overestimate the clinical data are consistent with unilateral cerebral representation of language in left handers.     

Pooling peripheral information: Averages versus extreme values

Suppose, as an idealization, that sensory intensity is coded in peripheral channels as identical Poisson pulse trains with intensity parameter a power function of signal intensity. Discrimination models based on either an average count computed over a fixed time or an average time computed for a fixed count per channel have difficulty in fitting the Weber function ($\text{ΔI}\text{I}$ versus I) if the free parameters are constrained to ranges determined from other experiments (magnitude estimation, reaction time). Here we study a different decision rule, namely, the most extreme observation in either the counting or timing mode. Our extremum-counting model, but not two timing ones, accounts very nicely for the Weber function. However, the ROC curves for these extremum models, which agree in shape with data of Green and Luce, yield estimates for the intensity parameter which are much larger than predicted by the power function growth used to calculate ΔI and about twice as large as those estimated from reaction time data collected in the same experiment.     

Naloxone and cold-water swim analgesia: Parametric considerations and individual differences

The role of endogenous opioids in the mediation of stress-induced analgesia has been studied using the opiate antagonist naloxone to reduce or eliminate the response. While the analgesic responses following some stressors are reduced by naloxone, other stressors, like cold-water swims, are altered minimally. However, in the case of inescapable foot shock analgesia, the temporal, numerical, and spatial arrangement of the shocks are critical parameters in determining whether naloxone is capable of altering the analgesic state. In assessing parametric variations of naloxone antagonism of cold-water swim analgesia, five experiments were performed. The first experiment showed that naloxone antagonized the analgesic response following a 3.5-min swim in a 15°C bath, but not in baths of 8°C and 2°C. The second experiment demonstrated dose-dependent antagonism of analgesia induced by 2°C swims for 2.5 and 3.5 min; shorter durations failed to increase thresholds. The third experiment indicated that naloxone decreased 2°C, 3.5-min swim analgesia when the pain test occurred 30 min after stress; longer intervals failed to produce analgesia. The fourth experiment showed that the temporal relationship between injections and swims had little bearing on resultant effects. Finally, since it appeared that naloxone decreased analgesia induced by the 2°C, 3.5-min swim in some animals, but not others, the fifth experiment found that the degree of naloxone antagonism was correlated with the magnitude of the analgesic response induced in individual animals. These results are discussed in terms of opioid and nonopioid mechanisms subserving pain inhibition.     

What the classical aphasia categories can't do for us, and why

A good deal of activity in contemporary aphasia research goes under the label "neurolinguistics." What characterizes this enterprise is, among other things, its goal of identifying neurally realized computational subsystems that support language processing. In this essay the thesis is put forward that this goal will not be served by the continued exploitation of the classical (Wernicke-Lichtheim) taxonomic categories. These categories, it is argued, cannot by virtue of their "polytypic" structure support the relevant neurolinguistic generalizations.     

Nature of spelling errors in transcortical sensory aphasia: A case study

The nature and extent of spelling errors in a patient with transcortical sensory aphasia were investigated. The two experimental conditions required the patient to spell monosyllabic and polysyllabic words both verbally and in written form. Analysis of the spelling errors revealed partially preserved knowledge of the visual image of a word as a whole, as well as preserved knowledge of temporal order. Our patient's error patterns in both conditions were more similar than dissimilar. These findings in conjunction with results reported in the literature indicate that patients exhibiting different aphasia syndromes use separate spelling strategies.     

Tail-pinch hyperalgesia and analgesia: Test-specific opioid and nonopioid actions

Reactivity to noxious stimuli in rats is altered following acute exposure to tail-pinch. However, while our laboratory has reported that tail-pinch produces hyperalgesia as measured by the flinch-jump test and attenuates analgesic responses following morphine and cold-water swims, others have found that tail-pinch elicits an opioid-sensitive analgesia on the hot plate test and a nonopioid-sensitive analgesia on the writhing test. The first experiment of the present study examined whether tail-pinch altered responses on two somatic pain tests and showed that tail-pinch significantly decreased both jump thresholds and tail-flick latencies. In assessing whether tail-pinch hyperalgesia on the jump test was mediated by endogenous opioids, the second experiment indicated that low (0.1 and 0.5 mg/kg) doses of naloxone eliminated tail-pinch hyperalgesia by selectively lowering control thresholds and a high (10 mg/kg) dose of naloxone eliminated tail-pinch hyperalgesia by selectively increasing thresholds following tail-pinch. Further, the third experiment showed that morphine-tolerant rats (10 mg/kg morphine daily over 14 days) did not exhibit tail-pinch hyperalgesia on the 15th day, an effect attributable to a selective lowering of control thresholds. The fourth experiment was a direct replication of the observation that tail-pinch produces analgesia on the writhing test which is not antagonized by naloxone. These results demonstrate that the pain test employed and the amount of prior tail-pinch experience are critical variables in determining the direction of tail-pinch effects upon pain perception in rats.     

Gerstmann syndrome without aphasia: a longitudinal study

A case of "pure" and complete Gerstmann syndrome resulting from a focal vascular lesion in the posterior parietal area of the left hemisphere and not associated with aphasic disorder or general mental impairment is described. The initial symptom presentation of this patient supported the concept of the autonomous nature of the Gerstmann aggregate but longitudinal findings suggested that these symptoms did not in fact represent a coherent syndrome.     

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 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.     

Production deficits in aphasia: A voice-onset time analysis

An experimental study was conducted to examine phonetic and phonemic deficits in the speech production of aphasics. Subjects included four Broca's aphasics, four Conduction aphasics, five Wernicke's aphasics, one nonaphasic dysarthric patient, and four normal controls. The subjects read a list of words containing word-initial stop consonants which were subsequently measured acoustically for voice-onset time. The results showed that Broca's aphasics exhibit a more severe production disorder than Conduction aphasics who in turn exhibit a more severe disorder than Wernicke's aphasics, in accord with clinical observations. In addition, although Broca's aphasics produced both phonetic and phonemic errors, the results showed that they have a pervasive phonetic disorder which affects their correct target productions as well as the total number of phonetic errors produced. This deficit however seems to be a speech deficit rather than a low-level motor control problem. In contrast, the Wernicke's aphasics show a deficit characterized by isolated phonemic mistargeting errors. Finally, the pattern of productions for the Conduction aphasics indicates that some patients show a predominantly phonetic disorder similar to the Broca's aphasics and others show predominantly a phonemic disorder similar to the Wernicke's aphasics.     

The lexicon and sentence generation in aphasia

The experiment tested a prediction, derived from the lexicalist model of grammar (J. Bresnan 1978, in M. Halle, J. Bresnan, & G. A. Miller (Eds.), Linguistic theory and psychological reality, Cambridge, Mass.: MIT Press, pp. 1–59), that difficulty in accessing a verb from the lexicon should impair the generation of the associated to-complement clause while not significantly affecting the generation of word-independent constructions such as questions. Four aphasic subjects with word-finding difficulties but relatively high BDAE ratings on grammatical ability were examined. A modified story completion paradigm was used to elicit the favored constructions. Consistent with the hypothesis, all subjects showed greater difficulty in generating to-complements.