1/168. Confabulation and delusional misidentification: a four year follow-up study.We describe a patient, AZ, who showed, in addition to an amnesic syndrome which eventually improved, longstanding confabulation and delusional misidentification following bilateral frontal and right temporal post-traumatic lesions. Confabulation appeared in personal recollections and on long-term verbal memory testing. Misidentification concerned mainly his wife and house. During the four year follow-up AZ's confabulation progressively shrinked so as to become restricted to verbal memory tasks. By contrast, misidentification persisted. General semantic memory was unimpaired throughout, while performance on frontal tests was initially poor and partly improved in time. We argue that confabulation and misidentification, though often intermingled and occurring after similar lesion pattern, should be considered as different neuropsychological entities.- - - - - - - - - - ranking = 1keywords = contrast (Clic here for more details about this article) |
2/168. Impairment of social and moral behavior related to early damage in human prefrontal cortex.The long-term consequences of early prefrontal cortex lesions occurring before 16 months were investigated in two adults. As is the case when such damage occurs in adulthood, the two early-onset patients had severely impaired social behavior despite normal basic cognitive abilities, and showed insensitivity to future consequences of decisions, defective autonomic responses to punishment contingencies and failure to respond to behavioral interventions. Unlike adult-onset patients, however, the two patients had defective social and moral reasoning, suggesting that the acquisition of complex social conventions and moral rules had been impaired. Thus early-onset prefrontal damage resulted in a syndrome resembling psychopathy.- - - - - - - - - - ranking = 1.3379749544044keywords = sensitivity (Clic here for more details about this article) |
3/168. A paradoxical improvement of misreaching in optic ataxia: new evidence for two separate neural systems for visual localization.We tested a patient (A. T.) with bilateral brain damage to the parietal lobes, whose resulting 'optic ataxia' causes her to make large pointing errors when asked to locate single light emitting diodes presented in her visual field. We report here that, unlike normal individuals, A. T.'s pointing accuracy improved when she was required to wait for 5 s before responding. This counter-intuitive result is interpreted as reflecting the very brief time-scale on which visuomotor control systems in the superior parietal lobe operate. When an immediate response was required, A. T.'s damaged visuomotor system caused her to make large errors; but when a delay was required, a different, more flexible, visuospatial coding system--presumably relatively intact in her brain--came into play, resulting in much more accurate responses. The data are consistent with a dual processing theory whereby motor responses made directly to visual stimuli are guided by a dedicated system in the superior parietal and premotor cortices, while responses to remembered stimuli depend on perceptual processing and may thus crucially involve processing within the temporal neocortex.- - - - - - - - - - ranking = 33.023255971395keywords = visual (Clic here for more details about this article) |
4/168. Unconscious activation of visual cortex in the damaged right hemisphere of a parietal patient with extinction.Visual extinction is a sign classically associated with right parietal damage. The patient can see a single stimulus presented in the ipsilesional or contralesional visual field, but is characteristically unaware of the same contralesional stimulus during simultaneous stimulation of both fields. The ipsilesional stimulus is said to 'extinguish' the contralesional stimulus from awareness during bilateral stimulation, perhaps due to a pathological bias in attention towards the ipsilesional side. Recent psychophysical evidence suggests that, although extinguished stimuli are not consciously seen, they may undergo residual processing and exert implicit effects on performance. However, the neural structures mediating such residual processing for extinguished stimuli remain unknown. Here we studied the neural activity evoked by an extinguished visual stimulus, using event-related functional MRI (fMRI), in a patient with circumscribed right inferior parietal damage and profound left-sided extinction. Monochrome objects (faces or houses) were presented in the left or right field, either unilaterally or bilaterally on each trial, with the patient indicating by button press whether he saw an object on the left, the right or on both sides. He usually saw only the right object on bilateral trials, yet the fMRI data showed activation of visual cortex contralateral to the extinguished left stimulus on these trials (compared with right-only stimulation), in both striate and early extrastriate areas of the right hemisphere. This activity had a similar location and time-course to that resulting from a single stimulus in the left versus right visual field. Cortical pathways involved in the normal processing of a single seen stimulus can thus still be activated by an unseen, extinguished stimulus after right parietal damage. Comparison of fMRI responses for faces versus houses revealed some category-specific activation for extinguished stimuli in right fusiform regions, but only at low statistical threshold. These results are discussed in terms of theoretical accounts for parietal extinction and, more generally, for the neural substrates of visual awareness.- - - - - - - - - - ranking = 49.534883957092keywords = visual (Clic here for more details about this article) |
5/168. Visually misguided reaching in Balint's syndrome.A patient with bilateral parietal damage leading to Balint's syndrome was tested on his ability to reach to, and to describe the locations of visual targets. RM was better at reaching to targets than he was at describing the locations of the same targets. Moreover, he was better at reaching to targets when he could not see them, compared to when he was reaching with visual guidance. In a final experiment, we found that RM showed strong inhibition of responses to non-target items, even though he had a poor representation of their location in depth. As a result of intact inhibition and impaired depth representation, he ignored both target and non-target items in a given direction. These results suggest that in RM a disturbed visual representation of space disrupts an otherwise relatively intact reaching control system.- - - - - - - - - - ranking = 16.511627985697keywords = visual (Clic here for more details about this article) |
6/168. Fulminant radiation-induced necrosis after stereotactic radiation therapy to the posterior fossa. Case report and review of the literature.The problem of radiation-induced necrosis of normal brain surrounding the target area has been a major catalyst for the development of stereotactically focused radiation therapy. According to current opinion, the effects of stereotactic irradiation are confined to the region targeted. The authors present a case in which the administration of a conventional dose of stereotactically focused irradiation for treatment of a pilocytic astrocytoma produced fulminant necrosis that necessitated a combination of intensive surgical and medical management, after which the patient improved over the course of 1 year. Concomitant with his improvement, the initially remarkable findings on magnetic resonance imaging gradually resolved. In this presentation the authors emphasize the need to evaluate alternatives carefully before a decision is made to administer therapeutic irradiation. Furthermore, they explore the roles that target, host, and dosage factors play in hypersensitivity to radiation injury, the detection of these factors before treatment, and the administration of radioprotective agents. With the growing use of stereotactically focused irradiation as a primary treatment modality for a variety of neurosurgical conditions, it is important to be cognizant of its uncommon but potentially lethal side effects. A cooperative multicenter database in which the outcomes and morbidity following stereotactic irradiation are recorded is essential to the detection of relatively uncommon but severe complications such as those observed in this case.- - - - - - - - - - ranking = 1.3379749544044keywords = sensitivity (Clic here for more details about this article) |
7/168. A neuropsychological outcome study of a child's left pericallosal arteriovenous malformation with occult fornix lesion.Pericallosal arteriovenous malformations are rarely reported, particularly in children. Moreover, few arteriovenous malformation studies report thorough neuropsychological outcome data for assessing post-surgical functioning. This case report provides a longitudinal study of a boy who initially presented for neuropsychological testing at the age of 8 years and 1 month, following polyvinyl alcohol embolization, two craniotomies and resections and stereotactic radiosurgery for a pericallosal arteriovenous malformation involving nearly all of the corpus callosum. Follow-up magnetic resonance imaging also indicated absence of the left fornix. Functioning has been assessed over 7 years. Neuropsychological measures identified a consistent pattern of verbally mediated cognitive and memory deficits, with relatively spared visual perceptual and visual motor functioning. No evidence of a split-brain syndrome was found. The findings are consistent with insult to dominant hemisphere language and memory systems, provide an interesting example of neurodevelopmental compensation for significant early brain insult, and may provide insight into functions subserved by the fornix.- - - - - - - - - - ranking = 11.007751990465keywords = visual (Clic here for more details about this article) |
8/168. Phonology and neuropsychology of the English past tense.The double dissociation between the regular and irregular past tense in English has been explained in terms of dual and single mechanism accounts. In previous research we have argued that problems with the regular past tense in patients with left inferior frontal damage arise from morpho-phonological parsing difficulties [Trends in cognitive science 2 (1998) 428]. This claim has recently been challenged by a single mechanism connectionist account which argues that a general phonological processing deficit causes the poor performance on the regular past tense, with morphological factors playing no explicit role [Proceedings of the National Academy of Sciences 96 (1999) 7592]. We used a speeded judgement task with four patients who have documented difficulties with the regular past tense to contrast the claims made by these different approaches. We compared patients' ability to detect the difference between the past tense and stem of regular (hugged/hug) and irregular (taught/teach) past tense verbs, as well as matched "pseudo" pairs (trade/tray and port/peach). These real word conditions were accompanied by matched sets of non-words (e.g. nugged/nug). patients' latencies to the regular past tense real word-pairs were consistently slower than in any other condition. To test for a general phonological processing deficit, we conducted several tests of phonological processing ability. The results show that the patients had a range of difficulties in phonological processing, from very mild to severe. This did not correlate with their performance on the speeded judgement task. We interpret this pattern of results as support for a specialised morpho-phonological processing mechanism which can be dissociated from other phonological processes and which is used directly in the processing of the regular past tense in a dual-mechanism system.- - - - - - - - - - ranking = 1keywords = contrast (Clic here for more details about this article) |
9/168. Orthodontic treatment in handicapped children: report of four cases.Mentally and physically handicapped children show in the orofacial system motor-sensitivity disturbances and malocclusions of varying severity. These dysfunctions affect the breathing and speech ability and inhibit the food intake. Myotherapeutic exercises for strengthening of lip and tongue muscles and orthodontic treatment of the malocclusions help provide esthetic and functional improvements in these patients. The limited compliance necessitates a differentiated procedure during the diagnostic and therapeutic process and demands compromises in some cases.- - - - - - - - - - ranking = 1.3379749544044keywords = sensitivity (Clic here for more details about this article) |
10/168. The use of visual feedback in establishing normal vocal intensity in two mildly retarded adults.A voice-activated relay was used to provide visual feedback of vocal amplitude for two subjects who habitually used very soft voices. The relay system caused a light to go on when vocal intensity was 65 dB SPL or greater. Both subjects demonstrated significant increases in their use of normal vocal intensity. One subject was able to transfer this progress to spontaneous conversational settings. Though some difficulties in generalization and automatization were evident, this system is recommended for use with persons exhibiting functional intensity deficiences.- - - - - - - - - - ranking = 27.519379976162keywords = visual (Clic here for more details about this article) |
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