11/75. Actors but not scripts: the dissociation of people and events in retrograde amnesia.We describe our further investigations of the retrograde amnesia in a single case. R.F.R. became globally amnesic following an attack of herpes simplex encephalitis. He could generate and recognize superordinate level information about the vast majority of proper names including the names of people but he was very impaired at giving information about what had "happened" to these same individuals. He could also provide detailed information about family friends but he could not recall salient major personal episodes in which these same individuals had been involved. knowledge of people appears to be represented in a different way to that of events, even when a singular event has provided the main or only opportunity for learning about the individual.- - - - - - - - - - ranking = 1keywords = information (Clic here for more details about this article) |
12/75. Is there an upper limit of intracranial pressure in patients with severe head injury if cerebral perfusion pressure is maintained?Authors of recent studies have championed the importance of maintaining cerebral perfusion pressure (CPP) to prevent secondary brain injury following traumatic head injury. Data from these studies have provided little information regarding outcome following severe head injury in patients with an intracranial pressure (ICP) greater than 40 mm Hg, however, in July 1997 the authors instituted a protocol for the management of severe head injury in patients with a glasgow coma scale score lower than 9. The protocol was focused on resuscitation from acidosis, maintenance of a CPP greater than 60 mm Hg through whatever means necessary as well as elevation of the head of the bed, mannitol infusion, and ventriculostomy with cerebrospinal fluid drainage for control of ICP. Since the institution of this protocol, nine patients had a sustained ICP greater than 40 mm Hg for 2 or more hours, and five of these had an ICP greater than 75 mm Hg on insertion of the ICP monitor and later experienced herniation and expired within 24 hours. Because of the severe nature of the injuries demonstrated on computerized tomography scans and their physical examinations, these patients were not aggressively treated under this protocol. The authors vigorously attempted to maintain a CPP greater than 60 mm Hg with intensive fluid resuscitation and the administration of pressor agents in the four remaining patients who had developed an ICP higher than 40 mm Hg after placement of the ICP monitor. Two patients had an episodic ICP greater than 40 mm Hg for more than 36 hours, the third patient had an episodic ICP greater than of 50 mm Hg for more than 36 hours, and the fourth patient had an episodic ICP greater than 50 mm Hg for more than 48 hours. On discharge, all four patients were able to perform normal activities of daily living with minimal assistance and experience ongoing improvement. Data from this preliminary study indicate that intense, aggressive management of CPP can lead to good neurological outcomes despite extremely high ICP. Aggressive CPP therapy should be performed and maintained even though apparently lethal ICP levels may be present. Further study is needed to support these encouraging results.- - - - - - - - - - ranking = 0.33333333333333keywords = information (Clic here for more details about this article) |
13/75. Computed cranial tomography, magnetic resonance imaging and single photon emission computed tomography in hemorrhagic shock and encephalopathy syndrome: a report of three cases.Three different neuro-imaging studies were performed in 3 infants with hemorrhagic shock and encephalopathy syndrome (HSE). Areas of cerebral infarction were noted on CT. Single photon emission computed tomography (SPECT) showed decreased perfusion in these areas in one infant. magnetic resonance imaging (MRI) also identified the areas of infarction, noted on CT, but provided additional information showing non-haem iron deposition in the thalami and basal ganglia.- - - - - - - - - - ranking = 0.33333333333333keywords = information (Clic here for more details about this article) |
14/75. Drawing from childhood experience: constructional apraxia and the production of oblique lines.We report the performance of two patients (ECR and RA) with constructional apraxia on a drawing task previously used to test the development of planning abilities in children. patients and controls were required to produce both oblique and horizontal/vertical lines that formed a right angle. Planning demands were manipulated across conditions by providing additional spatial information to constrain the drawing. Both patients produced drawings that were less accurate than controls. In addition, ECR was particularly poor at producing oblique lines compared to both RA and controls, even under conditions with minimal planning demands. This pattern of performance is qualitatively similar to that of children under eight years (see Broderick and Laszlo, 1988). Taken together these results provide further evidence that constructional apraxia is not a unitary disorder (with differential performance between patients) and that those differences are not necessarily related to laterality of damage (as both patients had right-hemisphere lesions). We argue for a more quantitative approach to the study of drawing abilities in neuropsychological testing in order to facilitate a finer grained analysis of the disorder and of comparison between patients.- - - - - - - - - - ranking = 0.33333333333333keywords = information (Clic here for more details about this article) |
15/75. Background and initial case studies into the effects of prospective memory training.Two preliminary case studies are presented introducing the technique of Prospective memory Training (PMT) as a potential means to manage severe memory impairments. PMT involves repetitive administration of prospective memory tasks in which the patient is asked to initiate a specific action at a future designated time. Background information relevant to the concept of prospective memory is presented. Possible theoretical foundations for PMT are also discussed.- - - - - - - - - - ranking = 0.33333333333333keywords = information (Clic here for more details about this article) |
16/75. Selective lower-case letter ideational dysgraphia.A case study of a man with a selective ideational dysgraphia for lower-case letters is described. His spelling skills were only very mildly impaired and there was no evidence of other praxic or visuoconstructional impairments. The findings are discussed in the context of information processing models. It is suggested that the representation of upper- and lower-case letters must be fairly independent.- - - - - - - - - - ranking = 0.33333333333333keywords = information (Clic here for more details about this article) |
17/75. The dissociation of anterograde and retrograde amnesia in a patient with herpes encephalitis.Establishing the precise relationship between anterograde amnesia (AA) and retrograde amnesia (RA) has implications for psychological and neuroanatomical models of memory. Many patients have been described who demonstrate AA in conjunction with RA or who demonstrate AA with little, or no apparent, RA. Intact anterograde memory in conjunction with deficits on tasks of retrograde memory is rarely encountered. In this paper, we describe a young female patient (LD) whose RA is extremely severe when contrasted with her mild to moderate deficits on tasks of verbal anterograde memory. In addition, on tests of episodic and semantic autobiographical memory, LD appeared more impaired in her recall of specific episodes than of factual information about her past. The importance of this dissociation in RA for the episodic-semantic distinction and the possible role of visual imagery in recalling remote episodic events are discussed.- - - - - - - - - - ranking = 0.33333333333333keywords = information (Clic here for more details about this article) |
18/75. A deficit in discriminating gaze direction in a case with right superior temporal gyrus lesion.The superior temporal sulcus (STS) region is well recognized as being heavily involved in detecting and discriminating gaze. Lesions confined to this area are quite rare in humans, and so the research has mainly depended on animal studies and functional neuroimaging in normal human subjects. We report one such rare case, a 54-year-old Japanese female with a possible congenital s anomaly who, after a cerebral hemorrhage, demonstrated a lesion almost completely confined to the entire right superior temporal gyrus (STG). In the subacute phase, the patient showed evidence of left hemispatial neglect, from which she gradually recovered. In the chronic phase, she showed a puzzling difficulty in obtaining eye-contact. We have conducted, in conjunction with conventional neuropsychological evaluations, experimental assessment of her ability in gaze cognition. Her performance on neuropsychological testing demonstrated no compromise in intellect, memory, or language skills, and a close-to-full recovery from neglect. On gaze cognition experiments, she was repeatedly shown to perceive left gaze as straight, and to a lesser degree, straight gaze as right. We suggest that the function of the STG in detecting gaze, together with the directional information it receives from earlier visual areas, may be associated, when damaged, with this deficit in detecting contra-directional gaze. We have demonstrated for the first time that a single circumscribed lesion to the STG results in both gaze processing deficit and concurrent aberrant gaze behavior of the victim herself, implicating a mechanism within the STG as an interface between gaze of others and gaze of self.- - - - - - - - - - ranking = 0.33333333333333keywords = information (Clic here for more details about this article) |
19/75. Specific retinotopically based magnocellular impairment in a patient with medial visual dorsal stream damage.We report here retinotopically based magnocellular deficits in a patient with a unilateral parieto-occipital lesion. We applied convergent methodologies to study his dorsal stream processing, using psychophysics as well as structural and functional imaging. Using standard perimetry we found deficits involving the periphery of the left inferior quadrant abutting the horizontal meridian, suggesting damage of dorsal retinotopic representations beyond V1. Retinotopic damage was much more extensive when probed with frequency-doubling based contrast sensitivity measurements, which isolate processing within the magnocellular pathway: sensitivity losses now encroached on the visual central representation and did not respect the horizontal meridian, suggesting further damage to dorsal stream retinotopic areas that contain full hemi-field representations, such as human V3A or V6. Functional imaging revealed normal responses of human MT to motion contrast. Taken together, these findings are consistent with a recent proposal of two distinct magnocellular dorsal stream pathways: a latero-dorsal pathway passing to MT and concerned with the processing of coherent motion, and a medio-dorsal pathway that routes information from V3A to the human homologue of V6. Anatomical evidence was consistent with sparing of the latero-dorsal pathway in our patient, and was corroborated by his normal performance in speed, direction discrimination and motion coherence tasks with 2D and 3D objects. His pattern of dysfunction suggests damage only to the medio-dorsal pathway, an inference that is consistent with structural imaging data, which revealed a lesion encompassing the right parieto-occipital sulcus.- - - - - - - - - - ranking = 0.33333333333333keywords = information (Clic here for more details about this article) |
20/75. The fusiform face area is not sufficient for face recognition: evidence from a patient with dense prosopagnosia and no occipital face area.We tested functional activation for faces in patient D.F., who following acquired brain damage has a profound deficit in object recognition based on form (visual form agnosia) and also prosopagnosia that is undocumented to date. Functional imaging demonstrated that like our control observers, D.F. shows significantly more activation when passively viewing face compared to scene images in an area that is consistent with the fusiform face area (FFA) (p < 0.01). Control observers also show occipital face area (OFA) activation; however, whereas D.F.'s lesions appear to overlap the OFA bilaterally. We asked, given that D.F. shows FFA activation for faces, to what extent is she able to recognize faces? D.F. demonstrated a severe impairment in higher level face processing--she could not recognize face identity, gender or emotional expression. In contrast, she performed relatively normally on many face categorization tasks. D.F. can differentiate faces from non-faces given sufficient texture information and processing time, and she can do this is independent of color and illumination information. D.F. can use configural information for categorizing faces when they are presented in an upright but not a sideways orientation and given that she also cannot discriminate half-faces she may rely on a spatially symmetric feature arrangement. Faces appear to be a unique category, which she can classify even when she has no advance knowledge that she will be shown face images. Together, these imaging and behavioral data support the importance of the integrity of a complex network of regions for face identification, including more than just the FFA--in particular the OFA, a region believed to be associated with low-level processing.- - - - - - - - - - ranking = 1keywords = information (Clic here for more details about this article) |
| <- Previous || Next -> |