Biomedical subjects
D Tranel
Publications and source records attributed to D Tranel.
Impulsive Homicide Associated With an Arachnoid Cyst and Unilateral Frontotemporal Cerebral Dysfunction.
A 65-year-old man with no past history of violent or criminal behavior abruptly strangled his wife after she scratched his face during a domestic argument. He appeared emotionally blunted and lacked insight into the motivations for his violent actions. The presence of left-sided cerebral dysfunction was initially suggested by subtly decreased dexterity of his dominant right hand. A magnetic resonance image (MRI) revealed a large arachnoid cyst centered in his left Sylvian fissure that effaced ventral frontal, anterior temporal and insular cortical gyri. The left middle cerebral artery was displaced relative to an earlier study, providing indirect evidence that the cyst had enlarged during his adult life. Neuropsychological testing indicated generally intact cognitive abilities except for mild impairment on tests of prospective memory and executive functions. He was found to have intermittently decreased EEG amplitude in the left fronto-temporal region. Positron emission tomography (PET) revealed significantly reduced resting glucose metabolism in the left frontal and temporal lobes. He was also found to have pathological diminution of autonomic responses to affectively charged visual stimuli, a phenomenon previously reported in patients with ventromedial frontal lobe injury and acquired disturbances of social conduct. In light of these findings, we suggest that his violent behavior represents stimulus-bound aggression, triggered by a novel physical threat and unchecked by learned social restraints owing to the presence of ventral prefrontal dysfunction.
Double dissociation of conditioning and declarative knowledge relative to the amygdala and hippocampus in humans.
A patient with selective bilateral damage to the amygdala did not acquire conditioned autonomic responses to visual or auditory stimuli but did acquire the declarative facts about which visual or auditory stimuli were paired with the unconditioned stimulus. By contrast, a patient with selective bilateral damage to the hippocampus failed to acquire the facts but did acquire the conditioning. Finally, a patient with bilateral damage to both amygdala and hippocampal formation acquired neither the conditioning nor the facts. These findings demonstrate a double dissociation of conditioning and declarative knowledge relative to the human amygdala and hippocampus.
Fear and the human amygdala.
We have previously reported that bilateral amygdala damage in humans compromises the recognition of fear in facial expressions while leaving intact recognition of face identity (Adolphs et al., 1994). The present study aims at examining questions motivated by this finding. We addressed the possibility that unilateral amygdala damage might be sufficient to impair recognition of emotional expressions. We also obtained further data on our subject with bilateral amygdala damage, in order to elucidate possible mechanisms that could account for the impaired recognition of expressions of fear. The results show that bilateral, but not unilateral, damage to the human amygdala impairs the processing of fearful facial expressions. This impairment appears to result from an insensitivity to the intensity of fear expressed by faces. We also confirmed a double dissociation between the recognition of facial expressions of fear, and the recognition of identity of a face: these two processes can be impaired independently, lending support to the idea that they are subserved in part by anatomically separate neural systems. Based on our data, and on what is known about the amygdala's connectivity, we propose that the amygdala is required to link visual representations of facial expressions, on the one hand, with representations that constitute the concept of fear, on the other. Preliminary data suggest the amygdala's role extends to both recognition and recall of fearful facial expressions.
Impaired recognition of emotion in facial expressions following bilateral damage to the human amygdala.
Studies in animals have shown that the amygdala receives highly processed visual input, contains neurons that respond selectively to faces, and that it participates in emotion and social behaviour. Although studies in epileptic patients support its role in emotion, determination of the amygdala's function in humans has been hampered by the rarity of patients with selective amygdala lesions. Here, with the help of one such rare patient, we report findings that suggest the human amygdala may be indispensable to: (1) recognize fear in facial expressions; (2) recognize multiple emotions in a single facial expression; but (3) is not required to recognize personal identity from faces. These results suggest that damage restricted to the amygdala causes very specific recognition impairments, and thus constrains the broad notion that the amygdala is involved in emotion.
How reliable are occipital asymmetry measurements?
In vivo occipital asymmetry (OA) measurements have been used to infer functional asymmetries such as language dominance. We investigated the degree of correlation between OA measurements derived by the same rater from different scans of the same subject. We used magnetic resonance (MR) and computerized axial tomography (CT) to study correlations between MR:MR, CT:CT and CT:MR. The highest intrasubject correlation was for MR:MR (r = 0.79). The CT:CT value was similar (r = 0.78) and the CT:MR correlation was slightly lower (r = 0.72). The findings indicate that the reliability of occipital asymmetry measurements is modest at best, setting a low ceiling on the valid use of this variable to infer other indexes.
Neuroanatomical correlates of electrodermal skin conductance responses.
We studied the electrodermal skin conductance responses (SCRs) of 36 subjects with well-characterized lesions in various regions of the cerebral hemispheres. Several lesion loci were consistently associated with defective electrodermal responding: the ventromedial frontal region (right and left), the right inferior parietal region, and the anterior cingulate gyrus (right and left). Our findings provide direct information regarding neural correlates of skin conductance responses in humans.
Type II diabetes and cognitive function. A population-based study of Native Americans.
OBJECTIVE: To explore the relationship between type II diabetes and cognitive function in older Native Americans and to assess the effects of other selected risk factors for cognitive dysfunction on this relationship. RESEARCH DESIGN AND METHODS: Cognitive function was assessed in 80 diabetic and 81 nondiabetic Native Americans who were 45-76 years of age in a cross-sectional population-based sub-study of the Strong Heart Study. Thirteen cognitive function tests were administered during a personal interview. Information about six other risk factors for cognitive dysfunction, including depressive symptoms, physical function, alcoholism, current alcohol use, hypertension, and myocardial infarction, was ascertained from interviews and from abstraction of medical records. RESULTS: Diabetes was associated with impairment on only two tests of cognitive function: verbal fluency (P = 0.004) and similarities (P = 0.010). Depressive symptoms were related to verbal fluency (P = 0.004), but did not explain the diabetes-related difference in performance. The effects of hypertension, depressive symptoms, and current alcohol use explained the diabetes-related performance difference on similarities. Cognitive function was not related to metabolic control (HbA1c level). CONCLUSIONS: We found little evidence that type II diabetes in this population of Native Americans is associated with decrement in cognitive function. Some of the cognitive impairment previously attributed to diabetes may be related, at least in part, to the influence of other risk factors. This should be considered in the design of future studies in other populations.
Assessment of higher-order visual function.
Ophthalmologists and neuro-ophthalmologists may be confronted with patients whose complaints go beyond problems with acuity or clarity of vision, raising the question of defects affecting higher-order aspects of visual function, such as reading, recognition, imagery, and visuospatial and visuoconstructional abilities. Standard neuro-ophthalmologic procedures are not designed to measure these functions. This article overviews several neuropsychological procedures that were designed to measure higher-order visual function, and proposes brief adaptations of these procedures that could be used in the office of the ophthalmologist or neuro-ophthalmologist, to provide economical, sensitive screening tests for detecting defects in reading, recognition, imagery, and other complex visual functions.
"Acquired sociopathy": the development of sociopathic behavior following focal brain damage.
Explore the source record for details and available documents.
Nouns and verbs are retrieved with differently distributed neural systems.
In a task designed to elicit the production of verbs, the patients known as AN-1033 and Boswell consistently produced the correct target words, performing no differently from normal controls. However, in a similar task designed to elicit the production of nouns, both patients performed quite defectively, and their scores were many SDs below those of controls. Language processing was otherwise normal--i.e., there were no impairments in grammar, morphology, phonetic implementation, or prosody; reading and writing were normal. In a third patient (KJ-1360), we obtained the reverse outcome--i.e., retrieval of common and proper nouns was preserved, but verb retrieval was defective. Together, the findings in the three patients constitute a double dissociation between noun and verb retrieval. In AN-1033 and Boswell, the lesions are located outside the so-called language areas (left frontoparietal operculum, posterior temporal region, inferior parietal lobule), where damage is associated with aphasia. The region of damage shared by the two patients is in left anterior and middle temporal lobe. This sector of left hemisphere contains systems for the retrieval of nouns that denote concrete entities. We propose that those systems are not essential for the retrieval of verbs and not involved in the vocal implementation of word forms. Those systems perform a two-way lexical-mediation role for concrete nouns and promote the reconstruction of a word form after the processing of sensory-motor characteristics of the entity denoted by that word. The findings in patient KJ-1360, whose lesion is in left premotor cortex, suggest that equivalent mediation systems for verbs are located in the left frontal region.
Acquired agraphia caused by focal brain damage.
Motor and linguistic aspects of writing were evaluated in 31 subjects with focal damage in 1 of 3 regions of the left hemisphere: (1) dorsolateral frontal lobe sparing primary motor cortex (group FL), (2) parietal lobe (group PL), or (3) temporal lobe (group TL). A standard procedure was used to evaluate writing for grapheme formation, spatial arrangement, spelling, word selection, grammar, and perseveration. It was predicted that agraphia would be observed in all 3 groups, and that the most severe impairments would be associated with frontal lobe damage, particularly in aspects of writing dependent on sequencing (grapheme formation, spelling, and grammar). It was found that agraphia was common in all groups, particularly in the acute epoch, and that all groups showed considerable recovery of writing by the chronic epoch. Few differences were found between groups. However, the FL group was impaired on spelling and grammar relative to the PL group in the acute epoch and impaired on grammar relative to the TL group in the chronic epoch. The findings are consistent with the notion that writing relies on a distributed neuroanatomical network, which acts in concert to link fragments of visuomotor activity with component linguistic elements.
Cross-modal associations and the human amygdala.
The role of the human amygdala in cross-modal associations was investigated in two subjects: SM-046, who had bilateral damage circumscribed to the amygdala; and the patient known as Boswell, whose damage in both temporal lobes includes the amygdala and surrounding cortices. Neither subject was impaired on Tactile-Visual or Visual-Tactile cross-modal tasks using the Arc-Circle test, suggesting that the amygdala is not involved in cross-modal associations involving perceptually "equivalent" basic stimulus properties. On the other hand, the results are compatible with the amygdala's involvement in higher-order associations between exteroceptive sensory data and interoceptive data concerned with correlated somatic states.
Knowledge systems.
The primate brain appears to store knowledge in widely distributed neural systems. Recent evidence suggests that these systems are specialized with respect to their capacity for supporting acquisition and retrieval of different domains and levels of knowledge.
Neurology of language.
A host of recent investigations and new theoretical models have advanced our understanding of the neural underpinnings of speech and language in humans. The application of positron emission tomography (PET) techniques to the investigation of language has provided corroborating evidence regarding the role of left hemisphere structures previously associated with language, together with some intriguing new findings. Innovative ideas regarding the ontogeny of language have come from studies of deaf infants who appear to babble with signs in much the same way that hearing infants babble vocally. A number of investigators have focused on the controversial syndrome known as progressive aphasia, and new evidence has supported the importance of this syndrome from both diagnostic (e.g. providing clues regarding neuropathology) and scientific (e.g. yielding information about the organization of lexical access structures in left temporal lobe) perspectives.
Neuropsychological assessment.
The aging population of the United States and many other countries guarantees that disorders common in elderly persons will continue to become more prevalent. In the past decade or so, we already have witnessed the beginning of this trend, with the rapid rise in the number of patients with degenerative dementia, especially Alzheimer's disease. On another track, sophisticated and timely medical and surgical interventions have produced a growing number of patients who survive serious head injury. These patients are typically young, and may live for many decades after their brain injury. In both examples, a core feature of the condition is impaired cognition and behavior; that is, defects in higher-level capacities such as memory, intellectual function, language, and decision-making. Neuropsychological assessment cannot be viewed as a luxury in cases such as these but rather, as a vital component of the neurodiagnostic evaluation. The neuropsychologist uses a set of standardized instruments to measure cognition and behavior in a comprehensive and precise manner, yielding rich information that may assist in accurate diagnosis, prudent management, and optimal rehabilitation. The neuropsychological examination may provide the only means with which to detect alterations in brain function, as in cases of mild head injury or low-level toxic exposure, which may not be revealed through other procedures. Finally, neuropsychological assessment will continue to play a key role in the scientific programs that are dedicated to advancing our understanding of the neural substrates of complex behavior.
Dissociated verbal and nonverbal retrieval and learning following left anterior temporal damage.
A subject with circumscribed damage to mesial and nonmesial risk anterior temporal structures (which included the left entorhinal cortex and hippocampus and the left anterolateral association cortices) maintains accurate nonverbal records of past experiences, and acquires accurate new nonverbal records. However, he has a severe defect in the retrieval and acquisition of specific verbal tags denoting those records. This dissociation is revealed by standard neuropsychological tasks, and by experimental probes focused on (1) retrieval of previously learned verbal and nonverbal entities; and (2) acquisition of new visuoverbal relationships. The results extend our current understanding of the manner in which mesial and nonmesial structures in the anterior temporal lobe contribute to the formation and storage of verbal and nonverbal records.
What has been rediscovered in "Rediscovering tactile agnosia"?
Explore the source record for details and available documents.