Biomedical subjects

Luigi Pizzamiglio

Publications and source records attributed to Luigi Pizzamiglio.

11 recordsLinked to original sources

PubMed2006

Neural bases of personal and extrapersonal neglect in humans.

Human awareness of left space may be disrupted by cerebral lesions to the right hemisphere (hemispatial neglect). Current knowledge on the anatomical bases of this complex syndrome is based on the results of group studies that investigated primarily the best known aspect of the syndrome, which is visual neglect for near extrapersonal (or peripersonal) space. However, another component-neglect for personal space-is more often associated with, than double-dissociated from, extrapersonal neglect, especially, in chronic patients. The present investigation aimed at exploring the anatomical substrate of both extrapersonal and personal neglect by using different advanced methodological approaches to lesion-function correlation. Fifty-two right ischaemic patients were submitted to neuropsychological assessment and in-depth MRI evaluation. The borders of each patient's lesion were delimited onto its own high-resolution anatomical image and then submitted to an automated spatial normalization algorithm. Besides conventional lesion density plots and subtraction analysis, region-based statistical analyses were performed on percentage values of the lesioned tissue also using a new parcellation of the white matter (WM). Data were finally submitted to voxelwise statistical analysis using a recently proposed method (voxel-based lesion-symptom mapping). Results converged in showing that awareness of extrapersonal space is based on the integrity of a circuit of right frontal (ventral premotor cortex and middle frontal gyrus) and superior temporal regions, whereas awareness of personal space is rooted in right inferior parietal regions (supramarginal gyrus, post-central gyrus and especially the WM medial to them). Common but less crucial regions for both neglect sub-types were located in the temporo-peri-Sylvian cortex. We suggest that extrapersonal space awareness critically involves a ventral circuit recently described for the exogenous allocation and reorienting of attention in space. Disruption of personal space awareness, instead, seems to be due to a functional disconnection between regions important for coding proprioceptive and somatosensory inputs, and regions coding more abstract egocentric representations of the body in space. In conclusion, present data strongly support a segregation of personal and extrapersonal spatial awareness in humans, both from a functional and an anatomical point of view.

Adult↗

PubMed2006

Development of a rehabilitative program for unilateral neglect.

PURPOSE: The aim of the present paper is to review several studies which assessed the validity of a visuo-spatial training for the rehabilitation of neglect patients. In addition two peripheral stimulations (TENS and Optokinetic Stimulation) have been studied to assess the improvements of neglect disorders when used in combination with the visuo-spatial training. Also we analyzed the potential effect of training for attention on neglect and, viceversa, the effect of visuo-spatial training on attentional impairments. METHODS: the goals have been investigated by both group studies and descriptions of single cases. RESULTS: The visuo-spatial training produced significant improvements on the performance of neglect patients which generalized to every day living situations: the results showed to be stable over time and had positive effects on a variety of other neurological impairments. It was also shown that the improvements are confined to tasks involving spatial exploration of extrapersonal space, but did not extend to other neglect disorders, such as representational and personal neglect. The use of peripheral stimulations, at variance with other studies in the literature, did not add any advantage as compared to the improvements produced by the visuo-spatial training. No transfer between training for neglect and attention was observed. CONCLUSIONS: the present review pointed out that neglect disorders can be improved in a clinically meaningful way: the studies described also showed some limitations and proposed the need of further researches in order to extend the improvements to several other aspects of the neglect syndrome.

Animals↗

PubMed2005

When space merges into language.

We present data from right brain-damaged patients, with and without spatial heminattention, which show the influence of hemispatial deficits on spoken language processing. We explored the findings of a previous study, which used an emphatic stress detection task and suggested spatial transcoding of a spoken active sentence in a 'language line'. This transcoding was impaired in its initial portion (the subject-word) when the neglect syndrome was present. By expanding the original methodology, the present study provides a deeper understanding of the level of spoken language processing involved in the heminattentional bias. To ascertain the role played by syntactic structure, active and passive sentences were compared. Sentences comprised of musical notes and of a sequence of unrelated nouns were also compared to determine whether the bias was manifest with any sequence of events (not only linguistic ones) deployed over time, and with a sequence of linguistic events not embedded in a structured syntactic frame. Results showed that heminattention exerted an influence only when a syntactically structured linguistic input (=sentence with agent of action, action and recipient of action) was processed, and that it did not interfere when a sequence of non-linguistic sounds or unrelated words was presented. Furthermore, when passing from active to passive sentences, the heminattentional bias was inverted, suggesting that heminattention primarily involves the logical subject of the sentence, which has an inverted position in passive sentences. These results strongly suggest that heminattention acts on the spatial transcoding of the deep structure of spoken language.

Adult↗

PubMed2005

Representational neglect and navigation in real space.

Topographical orientation relies on several cognitive strategies adopted by humans to move within the environment. In the present study, we investigate whether mental representation disorders affect specific cognitive mechanisms subserving human orientation. In order to differentiate distinct cognitive mechanisms involved in topographical orientation, we created a human version of the well-known "Morris Water Maze" and tested left and right brain damaged patients in a place-learning task. The test required the subjects to explore an experimental room in which no visual cues were present, find a target location, and then reach it in different conditions. The ability to memorize target locations in short- and long-term memory was also assessed. We found that all participants were able to reach the target location by using idiothetic cues (vestibular inputs, motor efferent copy, etc.). On the other hand, when starting position changed and re-orientation was necessary to reach the target location, in order to compute a new trajectory, only patients affected by representational neglect got lost. These results provide the first neuropsychological evidence of involvement of mental representation in a specific cognitive process allowing humans to reach a target place from any location in the environment.

Adult↗

PubMed2005

Analyzing aphasia data in a multidimensional symptom space.

The utility of single-case vs. group studies has been debated in neuropsychology for many years. The purpose of the present study is to illustrate an alternative approach to group studies of aphasia, in which the same symptom dimensions that are commonly used to assign patients to classical taxonomies (fluency, naming, repetition, and comprehension) are used as independent and continuous predictors in a multivariate design, without assigning patients to syndromes. One hundred twenty-six Italian-speaking patients with aphasia were first classified into seven classic aphasia categories, based on fluency, naming, auditory comprehension, and repetition scales. There were two goals: (1) compare group analyses based on aphasia types with multivariate analyses that sidestep classification and treat aphasic symptoms as continuous variables; (2) present correlation-based outlier analyses that can be used to identify individuals who occupy unusual positions in the multivariate "symptom space." In the service of the first goal, group performance on an external validation measure (the Token Test) was assessed in three steps: analyses of variance based on aphasia type, regressions using the same cut-offs for fluency, naming, comprehension and repetition as independent but dichotomous predictors, and regressions using the same subscales as continuous predictors (with no cut-offs). More variance in Token Test performance was accounted for when symptoms were treated as continuous predictors than with the other two methods, though use of independent but dichotomous predictors accounted for more variance than aphasia taxonomies. Thus, if we by-pass classical taxonomies and treat patients as points in a multidimensional symptom space, better predictions are obtained. Outlier analyses show that group results depend on heterogeneity among patients, which can be used as a search tool to identify potentially interesting dissociations. Hence this multivariate group approach is complementary to and compatible with single-case methods.

Aphasia↗

PubMed2004

The use of optokinetic stimulation in rehabilitation of the hemineglect disorder.

The aim of this study was to investigate whether it is possible to strengthen the rehabilitation of spatial hemineglect by combining standard training for spatial scanning with optokinetic stimulation. A simple randomized design was used: one group of neglect patients was treated with a combination of the two techniques, and a second group received only the standard treatment. Both treatments were given for six consecutive weeks and produced significant improvements. However, addition of the optokinetic stimulation did not improve the patients' performance. Also, none of the independent variables (i.e., presence/absence of hemianopia) predicted the positive effect occasionally observed in individual patients.

Aged↗

PubMed2004

Reference frames for spatial cognition: different brain areas are involved in viewer-, object-, and landmark-centered judgments about object location.

Functional magnetic resonance imaging was used to compare the neural correlates of three different types of spatial coding, which are implicated in crucial cognitive functions of our everyday life, such as visuomotor coordination and orientation in topographical space. By manipulating the requested spatial reference during a task of relative distance estimation, we directly compared viewer-centered, object-centered, and landmark-centered spatial coding of the same realistic 3-D information. Common activation was found in bilateral parietal, occipital, and right frontal premotor regions. The retrosplenial and ventromedial occipital-temporal cortex (and parts of the parietal and occipital cortex) were significantly more activated during the landmark-centered condition. The ventrolateral occipital-temporal cortex was particularly involved in object-centered coding. Results strongly demonstrate that viewer-centered (egocentric) coding is restricted to the dorsal stream and connected frontal regions, whereas a coding centered on external references requires both dorsal and ventral regions, depending on the reference being a movable object or a landmark.

Adult↗

PubMed2003

Between language and space: a cross-domain interaction.

We document for the first time the effect of a spatial deficit on an spoken language task. Right brain-damaged patients with and without neglect were administered a task of emphatic stress. Patients listened to 60 subject-verb-object sentence pairs. The emphatic stress could be placed on the subject, on the verb or on the object word. Patients had to judge whether the two sentences were same or different for the position of the emphatic stress. The judgements were more impaired in patients with neglect and when the stress was placed at the beginning of the sentence (on the subject word), that is to say, at the leftmost location of a hypothetical spatial representation of the heard sentence. We hypothesize that auditory language undergoes a spatial transcoding, and that this transcoding is affected by the presence of a spatial bias like that observed in patients with neglect.

Acoustic Stimulation↗

PubMed2003

The right hemisphere involvement in the processing of morphologically derived words.

It is widely documented that the left hemisphere is dominant in all complex linguistic tasks, including the processing of inflectional morphology. Both in Italian and in other languages, patients with brain damage with a selective deficit in derivational morphology have never been reported. Here we present the unusual case of two patients with very similar right-hemisphere lesions, who in the absence of aphasic disorders showed a selective inability in producing derivational morphology. Although both patients were unimpaired in producing verb infinitives, they both showed a selective deficit in producing nouns derived from verbs. This difficulty was not present in deriving nouns from other grammatical categories, such as adjectives. Interestingly, both patients mostly substituted the derived noun with the past participle of the verb. This pattern of results documents for the first time a right-hemisphere contribution in the domain of derivational morphology.

Aged↗

PubMed2003

Cortical modulation of whole body movements in brain-damaged patients.

The aim of the present study was to assess whether the consistent bias in reproducing distances and lengths on visual tasks that characterizes hemispatial neglect is also present when whole body displacements have to be calculated and reproduced. Two different experiments were proposed to participants with right brain lesions and neglect syndrome (RN+), right (RN-) and left brain lesions (LN-) without neglect and to participants without brain damage (C). In Experiment 1, participants actively reproduced passive linear displacements in the same or in a different direction. This task could be performed using only vestibular and somatosensory input, since no relevant visual input was available. In Experiment 2, relevant visual information had to be integrated with vestibular and somatosensory information in order to make the active reproduction. In Experiment 1, all brain-damaged groups reproduced the horizontal displacements similarly to the control group and without any spatial asymmetry. In Experiment 2, when vestibular, somatosensory and visually remembered information was required to produce an integrated mental representation, RN+ processed contralesional displacements differently from ipsilesional ones. Rectilinear displacements of the whole body in space were not affected by focal left and right brain lesions, suggesting that the computation of nonvisual information can be accomplished by brain structures different from those involved in spatial visual processes. However, when body displacements in space required a mental representation based on visual and nonvisual sensory information, a significant asymmetry appeared only in patients with hemispatial neglect. Some attempts are made to identify the neural substrates involved in this integration.

Aged↗

PubMed2003

Quantifying dissociations in neuropsychological research.

Double dissociations play an important role in neuropsychology, but they are often identified through subjective estimates of "high" versus "low" performance, without considering the probability that such an outcome might have occurred by chance. To determine whether two measures "come apart" in an interesting way in brain-damaged patients, it is important to know the degree to which variance in one measure can be predicted by variance in the other. This study introduces a statistical procedure to determine the probability of a double dissociation when the correlation between measures is taken into account. Different quantitative definitions of dissociations were compared in two large samples of neurological patients, and applied to four pairs of measures (two for language, two for hemispatial neglect) with different degrees of intercorrelation (ranging from +.21 to +.84). If the correlation between measures is not taken into account, large numbers of dissociated cases may be missed, especially for measures that are highly correlated. There are also qualitative differences between methods in the identity of those individuals who meet each definition.

Adolescent↗