Subcortical structures in aphasia. An analysis based on (F-18)-fluorodeoxyglucose, positron emission tomography, and computed tomography.

Subcortical structural damage that includes the anterior and posterior internal capsule, caudate, thalamus, lenticular nuclei, and insula has been shown to cause aphasias. A critical question that has not been resolved is whether the role of these structures on behavior is a direct one or whether it is indirect through the cortex. We have used pathway analysis to evaluate computed tomography, glucose metabolic, and language data from 47 aphasic patients to answer this question. For fluency (from the Western Aphasia Battery), subcortical structural damage had direct and indirect (through frontal lobe) effects on the behavior. For a comprehension task (sequential commands), subcortical damage had no direct effect and only a slight indirect effect through the temporal lobe. Thus, both direct and indirect effects of subcortical damage can be demonstrated for specific behavioral measures.

Temporoparietal cortex in aphasia. Evidence from positron emission tomography.

Forty-four aphasic patients were examined with (F18)-fluorodeoxyglucose positron emission tomography in a resting state to determine whether consistent glucose metabolic abnormalities were present. Ninety-seven percent of subjects showed metabolic abnormalities in the angular gyrus, 89% in the supramarginal gyrus, and 87% in the lateral and transverse superior temporal gyrus. Pearson product moment correlations were calculated between regional metabolic measures and performance on the Western Aphasia Battery. No significant correlations were found between the Western Aphasia Battery scores and right hemisphere metabolic measures. Most left hemisphere regions correlated with more than one score from the Western Aphasia Battery. Temporal but not frontal regions had significant correlations to the comprehension score. The left temporoparietal region was consistently affected in these subjects, suggesting that common features in the aphasias were caused by left temporoparietal dysfunction, while behavioral differences resulted from (1) the extent of temporoparietal changes, and (2) dysfunction elsewhere in the brain, particularly the left frontal and subcortical areas.

Voice discrimination and recognition are separate abilities.

Studies of brain-damaged subjects indicate that recognizing a familiar voice and discriminating among unfamiliar voices may be selectively impaired, and thus that the two are separate functions. Familiar voice recognition was impaired in cases of damage to the right (but not the left) hemisphere, while impaired unfamiliar voice discrimination was observed in cases with damage to either hemisphere.

Phonagnosia: a dissociation between familiar and unfamiliar voices.

A dissociation between facial recognition and facial discrimination is well known, but investigations of "phonagnosia" (impairment of voice recognition and discrimination) have not been pursued. Using familiar and unfamiliar voices as stimuli, a marked difference between the ability to recognize familiar voice and the ability to discriminate between unfamiliar voices was identified in five patients, and a sixth showed a severe impairment in both tasks. Clinical and radiologic findings in these cases suggest that recognition of familiar voices is impaired by damage to inferior and lateral parietal regions of the right hemisphere, whereas impairment of voice discrimination abilities is associated with temporal lobe damage of either hemisphere. This dissociation of recognition and discrimination of the human voice suggests that these two functions are mediated by different brain structures and may contribute differentially clinical syndromes.

Rags to riches: our increasing appreciation of cognitive and communicative abilities of the human right cerebral hemisphere.

Studies of right hemisphere abilities have grown from focusing on visuospatial and facial recognition in the 1950s to covering a broad spectrum of human behavior. The emergence of better understanding of auditory specializations, affective/emotional functions, personal relevance, idiosyncratic lexical organization, and the various aspects of language use--communicative pragmatics--is briefly reviewed.

Preserved recognition of familiar personal names in global aphasia.

Recognition of proper and common nouns was compared in four patients diagnosed with global aphasia secondary to ischemic left-hemisphere infarction. For proper noun recognition, subjects matched the spoken or written name of a famous person to a photograph, and for common nouns, subjects were tested on standardized and special word recognition tests. As expected, common noun recognition was severely compromised in the aphasic patients. In contrast, familiar personal names, despite their greater length and complexity, were recognized equally well by aphasic and normal control subjects. The right hemisphere may mediate the ability to recognize personally familiar names, as it may be specialized for establishing personally relevant environmental stimuli.

Cerebral laterality for famous proper nouns: visual recognition by normal subjects.

Lexical processing has long been associated with left-hemisphere function, especially for infrequently occurring words. Recently, however, persons with severe aphasia, including word-recognition deficits, were observed to recognize familiar proper nouns. Further, some patients suffering right-hemisphere damage were poorer at identifying famous names than left-hemisphere-damaged subjects. These observations point to the possibility that some property of the right hemisphere provides an advantage for the processing of familiar or personally relevant stimuli. To investigate this possibility, we conducted split-visual-field studies in which we manipulated stimulus sets, recognition task, and exposure duration. Greater accuracy in the right visual field was found for common nouns and unknown proper nouns, and famous proper nouns were overall more accurately recognized. Performance for famous nouns in the two visual fields was not significantly different when the task required categorization into famous or nonfamous and when stimuli most highly rated as familiar were used. These findings support our proposals that (1) both hemispheres can process famous proper nouns and (2) the right hemisphere is specialized for personal relevance.

Comprehension of familiar phrases by left- but not by right-hemisphere damaged patients.

Single words, familiar phrases (idioms and speech formulas), and novel sentences (matched to the familiar phrases in length, frequency, and structure) were selected for a picture-matching auditory comprehension task and administered to left- and right-brain damaged (LBD, RBD) subjects. The groups did not differ in single word comprehension. A 2 x 2 ANOVA revealed opposite patterns on the two other tasks, with LBD subjects performing worse on novel than familiar phrases, and RBD subject impaired on familiar phrase but not on novel sentence comprehension. The role of grammatical/referential vs. holistic/inferential meaning in left and right hemisphere function is discussed.

Hemispheric specialization for voice recognition: evidence from dichotic listening.

To measure lateralization of voice recognition abilities in normal subjects, listeners identified both the speaker (a famous male) and the word spoken on each trial in a dichotic listening paradigm. The voice identification task resulted in a zero ear advantage, which differed significantly from the significant right ear advantage found for word identification. This suggests that voice and word information, although carried in the same auditory signal, engage different cerebral mechanisms.

A case report of pathological rule-governed syllable intrusion.

A detailed analysis of a unique speech disturbance, marked by the frequent appearance in the speech stream of a meaningless intrusive syllable, is presented. Following a lengthy thoracic surgery, an American English speaking patient began to speak with non-English prosodic patterns, which evolved to a conspicuous intrusion in his speech of the syllable /sis/. This syllable and its variants were attached to words in a manner which conformed to the regular phonological rules in English (for formation of plural, possessive, and third person singular morphemes). The distribution and frequency of the intrusive syllable are described, and possible explanations for the abnormal occurrence of this particular syllable are discussed.

Influence of language structure on brain-behavior development.

Lack of exposure to specific sensory patterns during critical periods of development can result in a lack of responsiveness to those stimuli in adulthood. The present study extends these observations to native speakers of Japanese, a language which does not contain the contrastive /r/ and /l/ sounds present in English. Both electrophysiological (P3 event-related evoked potential) and behavioral results indicate deficient or absent discrimination of /r/ versus /l/ sounds in Japanese adults compared to native speakers of English. Thus, language structure appears to provide a subtle yet measurable effect on specific aspects of brain development and function.

The neurology of proverbs.

Although proverb tests are commonly used in the mental status examination surprisingly little is known about either normal comprehension or the interpretation of proverbial expressions. Current proverbs tests have conceptual and linguistic shortcomings, and few studies have been done to investigate the specific effects of neurological and psychiatric disorders on the interpretation of proverbs. Although frontal lobes have traditionally been impugned in patients who are "concrete", recent studies targeting deficient comprehension of non literal language (e.g. proverbs, idioms, speech formulas, and indirect requests) point to an important role of the right hemisphere (RH). Research describing responses of psychiatrically and neurologically classified groups to tests of proverb and idiom usage is needed to clarify details of aberrant processing of nonliteral meanings. Meanwhile, the proverb test, drawing on diverse cognitive skills, is a nonspecific but sensitive probe of mental status.

Disturbances of the temporal organization of speech following bilateral thalamic surgery in a patient with Parkinson's disease.

This report summarizes a detailed analysis of the speech of a 45-yr-old man who had become dysarthric following bilateral thalamic surgery for the relief of symptoms of Parkinson's disease. His speech was characterized by a rapid rate and a mild-to-moderate articulatory deficit. Intelligibility was markedly reduced. The rapid rate was found to be the result of decreased syllable durations rather than to changes in pause or phrase patterns. Decreased syllable durations resulted from abnormal shortening of vowels. Consonant releases were found to be prolonged. This distorted temporal relationship among speech segments was considered to be an important factor in the patient's poor intelligibility and partially explained why uniform electronic expansion of his speech resulted in only negligible increase in intelligibility. It is hypothesized that this speech disturbance results from the interaction of central "metronomic" abnormality with a peripheral neuromotor articulatory impairment.

Personal relevance and the human right hemisphere.

Brain damage can selectively disrupt or distort information and ability across the range of human behaviors. One domain that has not been considered as an independent attribute consists of acquisition and maintenance of personal relevant entities such as "familiar" faces, persons, voices, names, linguistic expressions, handwriting, topography, and so on. In experimental studies of normal mentation, personal relevance is revealed in studies of emotion, arousal, affect, preference and familiarity judgments, and memory. Following focal brain damage, deficits and distortions in the experience of personal relevance, as well as in recognizing formerly personally relevant phenomena, are well known to occur. A review and interpretation of these data lead to a proposal that the right hemisphere has a special role in establishing, maintaining, and processing personally relevant aspects of the individual's world.

The identification of affective-prosodic stimuli by left- and right-hemisphere-damaged subjects: all errors are not created equal.

Impairments in listening tasks that require subjects to match affective-prosodic speech utterances with appropriate facial expressions have been reported after both left- and right-hemisphere damage. In the present study, both left- and right-hemisphere-damaged patients were found to perform poorly compared to a nondamaged control group on a typical affective-prosodic listening task using four emotional types (happy, sad, angry, surprised). To determine if the two brain-damaged groups were exhibiting a similar pattern of performance with respect to their use of acoustic cues, the 16 stimulus utterances were analyzed acoustically, and the results were incorporated into an analysis of the errors made by the patients. A discriminant function analysis using acoustic cues alone indicated that fundamental frequency (FO) variability, mean FO, and syllable durations most successfully distinguished the four emotional sentence types. A similar analysis that incorporated the misclassifications made by the patients revealed that the left-hemisphere-damaged and right-hemisphere-damaged groups were utilizing these acoustic cues differently. The results of this and other studies suggest that rather than being lateralized to a single cerebral hemisphere in a fashion analogous to language, prosodic processes are made up of multiple skills and functions distributed across cerebral systems.

Expletives: neurolinguistic and neurobehavioral perspectives on swearing.

Severe aphasia, adult left hemispherectomy, Gilles de la Tourette syndrome (GTS), and other neurological disorders have in common an increased use of swearwords. There are shared linguistic features in common across these language behaviors, as well as important differences. We explore the nature of swearing in normal human communication, and then compare the clinical presentations of selectively preserved, impaired and augmented swearing. These neurolinguistic observations, considered along with related neuroanatomical and neurochemical information, provide the basis for considering the neurobiological foundation of various types of swearing behaviors.

Idiomatic versus literal interpretations of ditropically ambiguous sentences.

"Ditropically" ambiguous sentences (each having both a literal and an idiomatic interpretation) were prepared for listener's discrimination judgments, and for silent readers' rankings on an "idiomaticity" scale. Listeners were unable to discriminate the literal from the idiomatic versions when presented with randomized single sentences excised from paragraph contexts. There was a bias toward interpreting the sentences as idioms, which correlated with rankings of each sentence for its likelihood of idiomatic use. Listeners were easily able to identify the literal and the idiomatic versions of the same ditropic sentences presented in pairs or singularly, when speakers sought purposively to convey the contrasting meanings.

Voice perception deficits: neuroanatomical correlates of phonagnosia.

Voice perception (recognition of familiar voices and discrimination of unfamiliar voices) was studied in brain-damaged patients and normal controls. Left- and right-brain-damaged subjects were tested on familiar voices (25 famous males) and 26 pairs of unfamiliar voices. Deficits in recognizing familiar voices were significantly correlated with right-hemisphere damage; discrimination of unfamiliar voices was worse in both clinical groups than in normal controls. Computerized tomographic scans indicated that an intact right parietal-lobe was present in all cases of normal voice recognition, while right parietal-lobe damage was significantly correlated with a deficit in voice recognition. Temporal-lobe damage of either hemisphere was associated with a voice discrimination deficit.

Disambiguation of ditropic sentences: acoustic and phonetic cues.

In a previous study, we demonstrated that listeners were highly successful in identifying the intended meaning of spoken ditropic sentences (those which may carry either a literal or an idiomatic meaning) when speakers were instructed to convey the distinction. The present communication reports on acoustic and phonetic analyses carried out with the goal of identifying cues that distinguished the literal and idiomatic utterances. Certain prosodic differences were observed. Literal utterances were systematically longer than idioms. This was partly due to increased use of pauses, as well as to increased duration of major lexical items. Moreover, literal sentences were typically characterized by greater numbers of pitch contours (discernible rise-fall excursions of fundamental frequency) and open junctures than were idiomatic utterances. In addition to suprasegmental contrasts, articulatory distinctions--corresponding to lento-allegro phonological rules--were also observed. These distinctions directly reflect the structural differences intrinsic to the two types of utterances. A literal sentence is formulated by the organization of constituent words and phrases. Idioms, on the other hand, are holistic units, largely nontransparent to syntactic structure or the usual meaning of the lexical members.