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Biomedical subjects

N Smania

Publications and source records attributed to N Smania.

26 records · Page 2Linked to original sources
PubMed1997

Influence of stimulus salience and attentional demands on visual search patterns in hemispatial neglect.

Seventy-five left and right brain-damaged patients, with or without hemispatial neglect, and 40 age-matched control subjects were tested on cancellation tasks with two different visual textures modeled after Julesz (1981). In one condition ("preattentive"), target elements segregated easily from background elements and were perceived effortlessly. In the other ("attentive"), target elements did not segregate easily and could be detected only after prolonged focal scrutiny. Both controls and patients were more accurate and faster on the preattentive than attentive texture. However, only neglect patients were disproportionately impaired on the attentive texture, thus suggesting that unilateral neglect is exacerbated by the low visual salience of the stimuli and a higher engagement of focal attention. Thus, a simple bedside test may help to tell apart the level of visual information processing maximally impaired in neglect patients.

Analysis of Variance↗
PubMed1997

Visuomotor imagery and rehabilitation of neglect.

OBJECTIVE: To assess the effectiveness of visuomotor imagery training in the rehabilitation of unilateral neglect. DESIGN: Before-after trial. Behavioral analysis of single cases. SETTING: Neurologic rehabilitation unit of a university hospital. PATIENTS: Two patients with acquired brain injury who were suffering from severe and long-lasting unilateral neglect consequent to large lesions of cortical and subcortical right-brain. INTERVENTION: A behavioral training program consisting of visual and movement imagery exercises. Forty experimental sessions, each lasting 50 minutes, were delivered. MAIN OUTCOME MEASURES: Six neuropsychological tests evaluating unilateral neglect: seven "functional" tests assessing neglect behavior under daily life conditions; a questionnaire (filled out by the patients' relatives) concerning the patients' disability in the family context attributable to neglect. All the outcome measures were recorded at three different times: before, soon after, and 6 months after the end of the experimental training. RESULTS: The visuomotor "imagery training" ameliorated the deficit in performance related to neglect in both patients. All the outcome measures (neuropsychological and functional tests and the questionnaire) were positively influenced by the treatment. Moreover, the improvement was stable over a 6-month period, suggesting that the treatment had a long-term effect. CONCLUSIONS: The results show the possible effectiveness of a training method based on visuomotor imagery in diminishing impairment and functional disability associated with contralateral neglect.

Activities of Daily Living↗
PubMed1997

Spatio-temporal properties of the pattern of evoked phantom sensations in a left index amputee patient.

In a left index finger amputee, appropriate stimulation of skin areas of the remnant left fingers or left lower face evoked veridical sensations as well as sensations localized to the phantom finger. Five months after the amputation, there was a systematic correspondence between positions of digital and facial stimuli and positions of stimuli felt on the phantom. More than 3 years after the amputation, orderly maps of the phantom index on the ipsilateral fingers were still detected. By contrast, poorly organized facial maps were present only contralaterally to the amputation. The maps on the remnant fingers are likely to acquire stability because they are systematically activated during manipulations performed with the mutilated hand. The disorganization of facial maps may be related to their irrelevance for behavioral control in everyday life conditions.

Adult↗
PubMed1996

Disownership of left hand and objects related to it in a patient with right brain damage.

We describe a woman with right brain damage who denied the ownership of her left hand and of extracorporeal objects (e.g. rings) which were worn on the left hand itself. When the same objects were worn on the right hand or were held by the examiner, the patient correctly recognized them as her own. Other personal objects unrelated to the left hand (e.g. pins, earrings, comb) were always correctly recognized as her own. Thus, by inference, the mental image of one's body may include inanimate objects which had been in contact or in close proximity with the body itself. These findings provide, for the first time, experimental support to the speculative notion of an extended body schema.

Aged↗
PubMed1996

Implicit redundant-targets effect in visual extinction.

Patients with left visual extinction as a result of unilateral right hemisphere damage were tested on a redundant-targets effect paradigm (RTE). LED-generated brief flashes were lateralized either to the left or to the right visual hemifield or presented bilaterally. Subjects were asked to press a key as fast as possible following either unilateral or bilateral stimuli and immediately afterwards to report on the number of stimuli presented. As previously found in normal subjects, bilateral stimuli were responded to faster than unilateral ones, and this was evidence of a RTE. The main thrust of this study was that extinction patients showed a RTE not only for correctly perceived bilateral stimuli but also in trials in which they extinguished the stimulus on the field contralateral to the lesion. This result is compatible with a preserved processing of the extinguished input at least up to the stage at which it may interact with the input from the normal side to yield a speeded motor response. Interestingly, the implicit redundancy gain of extinction patients was found to fit a coactivation (i.e. neural) rather than a probabilistic model.

Aged↗
PubMed1996

Input and response determinants of visual extinction: a case study.

We have studied a patient, CZ, with contralateral visual extinction due to a large ischaemic frontal-parietal-temporal lesion in the right hemisphere. We found that manipulation of intensity of the visual stimulus had little effect while an increase in eccentricity substantially increased extinction rate. An important factor was represented by the hemifield of stimulus presentation: when double stimuli were presented to the contralesional (left) hemifield, the leftmost stimulus was consistently extinguished while when stimuli were presented to the ipsilesional (right) hemifield, extinction was absent. Such effect was specific to hemifield rather than to head- and trunk-defined hemispace. Manipulation of response-related variables affected extinction to a large extent: In particular, the use of nonverbal responses diminished extinction considerably. This suggests that an important component of extinction may be represented by an impaired access of visual information to the left hemisphere. Finally, the RT results confirmed previous evidence of an ipsilesional attentional bias favouring the rightmost stimuli both in the contralesional and in the ipsilesional hemifield.

Brain Ischemia↗
PubMed1995

Sensory and spatial components of somaesthetic deficits following right brain damage.

We instructed patients with right brain damage (RBD) and somatosensory extinction, hemispatial neglect, or both to verbally report light touches delivered to the left hand, to the right hand, or simultaneously to both hands in two experimental situations. In the "anatomic" situation, each hand was in its homonymous hemispace; in the "crossed" one, each hand was held across the corporeal midline, in its heteronymous hemispace. Under both single and the double stimulation conditions, RBD patients detected stimuli delivered to the contralesional hand with lower accuracy in the anatomic than in the crossed position. This result suggests that somaesthetic deficits can be due not only to sensory but also to attentional factors, depending on the spatial position of the hands. Processing of sensory information in primary areas should not be influenced by the hemispatial position of the stimulated body part. These results suggest that somaesthetic deficits may stem not only from damage of primary sensory areas, as classically held, but also from damage of higher-order areas where information about stimuli, body parts, and extrapersonal space is integrated. Finally, the results show that sensory and attentional components of the deficit can be dissociated by using a very simple clinical test.

Aged↗