Costanza Papagno

Unawareness of disease following lesions of the right hemisphere: Anosognosia for hemiplegia and anosognosia for hemianopia

Unawareness of motor and visual-field defects was investigated in 97 right brain-damaged subjects. Both kinds of anosognosia were found to be double-dissociated from more elementary neurological disorders and from personal and extra-personal neglect. The relationships between anosognosia and unilateral neglect are discussed and allusion is made to the implications concerning the neurological organization of higher control functions.

When long-term learning depends on short-term storage

Abstract Since the 1960s, there has been controversy as to whether long-term learning might depend on some form of temporary short-term storage. Evidence that patients with grossly impaired memory span might show normal learning was, however, particularly problematic for such views. We reexamine the question by studying the learning capacity of a patient, P.V., with a very pure deficit in short-term memory. A series of experiments compare her learning capacity with that of matched controls. The first experiment shows that her capacity to learn pairs of meaningful words is within the normal range. A second experiment examines her capacity to learn to associate a familiar word with an unfamiliar item from another language. With auditory presentation she is completely unable to perform this task. Further studies show that when visual presentation is used she shows evidence of learning, but is clearly impaired. It is suggested that short-term phonological storage is important for learning unfamiliar verbal material, but is not essential for forming associations between meaningful items that are already known. Implications for the possible role of a phonological short-term store in the acquisition of vocabulary by children are discussed.

Phonological short-term memory and foreign-language vocabulary learning

Abstract Data from foreign language vocabulary learning in a short-term memory patient, and native language vocabulary learning in children suggest that the short-term phonological store plays an important role in long-term learning. The present study used articulatory suppression to explore the role of the phonological loop system of working memory in the acquisition by adults of foreign language vocabulary. Experiments 1 and 2 showed that articulatory suppression disrupts the learning of Russian vocabulary, but not native language paired associates, by Italian subjects. Two apparently equivalent experiments, however, using English subjects failed to demonstrate the predicted disruption of Russian vocabulary learning by articulatory suppression. This was shown to be attributable to the greater association value of the Russian words to the English subjects. Two final experiments using English subjects replicated the Italian results, showing a differential disruption of the learning of unfamiliar material, when this comprises either CVC-CVC nonsense items, or Finnish words that were selected to be very dissimilar to English. It is concluded that the phonological loop concept of working memory is used in foreign language vocabulary acquisition, but can be circumvented if the material allows semantic associations to be created.

Dual-task performance in dysexecutive and nondysexecutive patients with a frontal lesion

Patients with defined frontal lobe lesions were assigned to 1 of 2 groups based on whether they showed a behaviorally assessed dysexecutive syndrome or were behaviorally normal. All participants were tested on dual-task performance and on 2 tasks assumed to measure frontal lobe function, the Wisconsin Card Sorting Test and verbal fluency. The dysexecutive group differed significantly from the nondysexecutive in showing impaired capacity for dual-task coordination, but there were no significant differences on the Wisconsin Card Sorting Test and verbal fluency. Results are interpreted in terms of a multicomponent central executive, whose function is linked to, but not coterminous with, the operation of the frontal lobes.

Motor and language DTI Fiber Tracking combined with intraoperative subcortical mapping for surgical removal of gliomas

Preoperative DTI Fiber Tracking (DTI-FT) reconstruction of functional tracts combined with intraoperative subcortical mapping (ISM) is potentially useful to improve surgical procedures in gliomas located in eloquent areas. Aims of the study are: (1) to evaluate the modifications of fiber trajectory induced by the tumor; (2) to validate preoperative DTI-FT results with intraoperative identification of functional subcortical sites through direct subcortical stimulation; (3) to evaluate the impact of preoperative DTI-FT reconstructions in a neuronavigational setup combined with ISM technique on duration and modalities of surgical procedures, and on functional outcome of the patients. Data are available on 64 patients (52 low-grade and 12 high-grade gliomas). DTI-FT was acquired by a 3-T MR scanner with a single-shot EPI sequence (TR/TE 8986/80 ms, b=1000 s/mm) with gradients applied along 32 non-collinear directions. 3D Fast Field Echo (FFE) T1-weighted imaging (TR/TE 8/4 ms) was performed for anatomic guidance. The corticospinal tract (CST), superior longitudinal, inferior fronto-occipital and uncinatus fasciculi were reconstructed. Data were transferred to the neuronavigational system. Functional subcortical sites identified during ISM were correlated with fiber tracts depicted by DTI-FT. In high-grade gliomas, DTI-FT depicted tracts mostly at the tumor periphery; in low-grade gliomas, fibers were frequently located inside the tumor mass. There was a high correlation between DTI-FT and ISM (sensitivity for CST=95%, language tracts=97%). For a proper reconstruction of the tracts, it was necessary to use a low FA threshold of fiber tracking algorithm and to position additional regions of interest (ROIs). The combination of DTI-FT and ISM decreased the duration of surgery, patient fatigue, and intraoperative seizures. Combination of DTI-FT and ISM allows accurate identification of eloquent fiber tracts and enhances surgical performance and safety maintaining a high rate of functional preservation.

Is Preoperative Functional Magnetic Resonance Imaging Reliable for Language Areas Mapping in Brain Tumor Surgery? Review of Language Functional Magnetic Resonance Imaging and Direct Cortical Stimulation Correlation Studies

OBJECTIVELanguage functional magnetic resonance imaging (fMRI) has been used extensively in the past decade for both clinical and research purposes. Its integration in the preoperative imaging assessment of brain lesions involving eloquent areas is progressively more diffused in neurosurgical practice. Nevertheless, the reliability of language fMRI is unclear. To understand the reliability of preoperative language fMRI in patients operated on for brain tumors, the surgical studies that compared language fMRI with direct cortical stimulation (DCS) were reviewed. METHODSArticles comparing language fMRI with DCS of language areas were reviewed with attention to the lesion pathology, the magnetic field, the language tasks used pre- and intraoperatively, and the validation modalities adopted to establish the reliability of language fMRI. We tried to explore the effectiveness of language fMRI in gliomas. RESULTSNine language brain mapping studies compared the findings of fMRI with those of DCS. The studies are not homogeneous for tumor types, magnetic fields, pre- and intraoperative language tasks, intraoperative matching criteria, and results. Sensitivity and specificity were calculated in 5 studies (respectively ranging from 59% to 100% and from 0% to 97%). CONCLUSIONThe contradictory results of these studies do not allow consideration of language fMRI as an alternative tool to DCS in brain lesions located in language areas, especially in gliomas because of the pattern of growth of these tumors. However, language fMRI conducted with high magnet fields is a promising brain mapping tool that must be validated by DCS in methodological robust studies.

Intraoperative subcortical language tract mapping guides surgical removal of gliomas involving speech areas

OBJECTIVESubcortical stimulation can be used to identify functional language tracts during resection of gliomas located close to or within language areas or pathways. The objective of the present study was to investigate the feasibility of the routine use of subcortical stimulation for identification of language tracts in a large series of patients with gliomas and to determine the influence that subcortical language tract identification exerted on the extent of surgery and on the appearance of immediate and definitive postoperative deficits. METHODSSubcortical stimulation for language tract identification was systematically used during surgical removal of 88 gliomas (44 high-grade and 44 low-grade gliomas) involving language pathways. Procedures were performed during asleep/awake craniotomy. Subcortical stimulation was continuously alternated with surgical resection in a back-and-forth fashion. Language performances were tested by neuropsychological language evaluation preoperatively and at 3, 30, and 90 days after surgery. RESULTSLanguage tracts were identified in 59% of patients, with differences according to tumor location but not according to histological grade. Language tract identification influenced the ability to reach a complete tumor removal in low-grade gliomas, in which tracts were documented inside the peripheral mass of the tumor. Identification of language tracts was associated with a higher occurrence of transient postoperative deficits (67.3% of cases), but a low occurrence of definitive morbidity (2.3% of cases). A pattern of typical language disturbances related to the phonological and semantic system can be identified according to tumor location, with preservation being important for the maintenance of language integrity. CONCLUSIONOur study supports the routine use of subcortical stimulation for language tract identification as a reliable tool for guiding surgical removal of gliomas in or in close proximity to language areas or pathways.

Verbal Short-term Memory and Vocabulary Learning in Polyglots

Polyglot and non-polyglot Italian subjects were given tests assessing verbal (phonological) and visuo-spatial short-term and long-term memory, general intelligence, and vocabulary knowledge in their native language. Polyglots had a superior level of performance in verbal short-term memory tasks (auditory digit span and nonword repetition) and in a paired-associate learning test, which assessed the subjects’ ability to acquire new (Russian) words. By contrast, the two groups had comparable performance levels in tasks assessing general intelligence, visuo-spatial short-term memory and learning, and paired-associate learning of Italian words. These findings, which are in line with neuropsychological and developmental evidence, as well as with data from normal subjects, suggest a close relationship between the capacity of phonological memory and the acquisition of foreign languages.

What is the role of the uncinate fasciculus? Surgical removal and proper name retrieval

The functional role of the uncinate fasciculus is still a matter of debate. We examined 44 patients submitted to awake surgery for removal of a left frontal or temporal glioma. In 18 patients, the removal included the uncinate fasciculus. We compared patients with or without removal on a series of neuropsychological tasks, performed at different time intervals: pre-surgery, in the first week after surgery and 3 months after surgery. Functional magnetic resonance and diffusion tensor imaging, fibre-tracking techniques were performed before surgery. At the last examination, patients with uncinate removal were significantly impaired in naming of famous faces and objects as compared with patients without removal. We further divided patients according to the site of the tumour (either frontal or temporal). At the follow-up, patients with a temporal glioma who underwent uncinate removal had the worst loss of performance in famous face naming. In addition, on the same task, the group with a frontal glioma that underwent resection of the frontal part of the uncinate performed significantly worse than the group with a frontal glioma but without uncinate removal. In conclusion, the resection of the uncinate fasciculus, in its frontal or temporal part, has long-lasting consequences for famous face naming. We suggest that this fibre tract is part of a circuitry involved in the retrieval of word form for proper names. Retrieval of conceptual knowledge was intact.

Improvement of left visuo-spatial hemineglect by left-sided transcutaneous electrical stimulation.

The effects of transcutaneous electrical stimulation on left visuo-spatial hemineglect, assessed by a visuo-motor exploratory task (letter cancellation), were investigated in patients with right hemisphere lesions. In Experiment 1 left neck stimulation temporarily improved the deficit in 13 out of 14 patients (93%), while stimulation of the right neck had no positive effects, worsening exploratory performance in nine patients (64%). Experiment 2 showed that left neck stimulation temporarily improved neglect also when head movements were prevented by a chin-rest. In Experiment 3, stimulation of both the left hand and left neck had comparable positive effects on visuo-spatial hemineglect. These results are interpreted in terms of: (1) non-specific activation of the right hemisphere, contralateral to the stimulation side; (2) specific directional effects of left somatosensory stimulation on the egocentric co-ordinates of extra-personal space, which in neglect patients are distorted towards the side of the brain lesion.