Biomedical subjects

Valentina Moro

Publications and source records attributed to Valentina Moro.

5 recordsLinked to original sources

PubMed2006

Mapping implied body actions in the human motor system.

The human visual system is highly tuned to perceive actual motion as well as to extrapolate dynamic information from static pictures of objects or creatures captured in the middle of motion. Processing of implied motion activates higher-order visual areas that are also involved in processing biological motion. Imagery and observation of actual movements performed by others engenders selective activation of motor and premotor areas that are part of a mirror-neuron system matching action observation and execution. By using single-pulse transcranial magnetic stimulation, we found that the mere observation of static snapshots of hands suggesting a pincer grip action induced an increase in corticospinal excitability as compared with observation of resting, relaxed hands, or hands suggesting a completed action. This facilitatory effect was specific for the muscle that would be activated during actual execution of the observed action. We found no changes in responsiveness of the tested muscles during observation of nonbiological entities with (e.g., waterfalls) or without (e.g., icefalls) implied motion. Thus, extrapolation of motion information concerning human actions induced a selective activation of the motor system. This indicates that overlapping motor regions are engaged in the visual analysis of physical and implied body actions. The absence of motor evoked potential modulation during observation of end posture stimuli may indicate that the observation-execution matching system is preferentially activated by implied, ongoing but not yet completed actions.

Adult↗

PubMed2005

Gravitational influences on reference frames for mapping somatic stimuli in brain-damaged patients.

Previous studies have shown that the manipulation of body position in space can modulate the manifestations of visual neglect. Here, we investigated in right brain-damaged patients (RBD) the possible influence of gravitational inputs on the capability to detect tactile stimuli delivered to hands positioned in ipsilesional or contralesional space. RBD patients (with or without impairments in detecting contralesional stimuli under single and double stimulation conditions) and healthy control subjects were tested in a tactile detection task in which gravitational (upright vs. supine) and hand position (anatomical vs. crossed) variables were orthogonally varied. The postural manipulation of the entire body turned out to influence the degree of tactile detection. In particular, RBD patients with tactile deficits detected a significantly higher number of left-sided stimuli in the supine posture than in the upright posture. Moreover, crossing of hands improved the ability of RBD patients with tactile deficits in detecting stimuli delivered to their left contralesional hand. The beneficial effect of lying supine was independent of the spatial position of the hands, thus suggesting that the improvement of performance dependent upon entire-body posture and that dependent upon crossing hands may rely upon separate mechanisms.

Aged↗

PubMed2004

Dissociation between taste and tactile extinction on the tongue after right brain damage.

In patients with right brain damage (RBD) or left brain damage (LBD) and healthy subjects, tactile and three basic gustatory stimuli (sour, salty, bitter) were applied to the left or right hemitongues or to both hemitongues simultaneously. Tactile stimuli were detected and localized by verbal report, whereas gustatory stimuli were identified by pointing to the corresponding name on cards bearing the names of the three tastes. In the tactile test, 9 of 18 RBD patients showed extinction of left hemitongue stimuli, whereas the remaining RBD patients, 9 LBD patients and 14 healthy subjects detected virtually all stimuli in all conditions. In the gustatory test, healthy subjects outperformed the two brain damaged groups which nevertheless responded well above chance and did not differ from one another. Unexpectedly, the nine RBD patients with left hemitongue tactile extinction showed no gustatory extinction, since performance did not differ significantly between the two hemitongues on both unilateral and bilateral stimulations. To account for these findings, some evidence suggests that the tongue representation is bilateral in both modalities, but predominantly ipsilateral in the gustatory modality and predominantly contralateral in the tactile modality. The RBD patients with left hemitongue tactile extinction were those with more marked symptoms of left-sided extinction in the visual and auditory modalities, making it likely that their brain damage was also responsible for left lingual tactile extinction. The absence of left gustatory extinction in those patients can be attributed to the predominant channelling of left hemitongue taste inputs into the intact left hemisphere.

Aged↗

PubMed2004

Changes in spatial position of hands modify tactile extinction but not disownership of contralesional hand in two right brain-damaged patients.

Somatic misperceptions and misrepresentations, like supernumerary phantom limb and denial of ownership of a given body part, have typically been reported following damage to the right side of the brain. These symptoms typically occur with personal or extrapersonal neglect and extinction of left-sided stimuli, suggesting that all these different symptoms may be linked to the same neural substrate. In the present research, we tested two right brain-damaged (RBD) patients to find out whether changing the position of the hands in space influences tactile extinction and denial of ownership to the same extent. Results showed that manipulation of the spatial position of the hands reduces tactile extinction but leaves denial of ownership of the left hand unaffected. Such a dissociation suggests that delusional misperceptions may be independent from somatic neglect and that representation of hands in space and attribution of ownership are dynamically mapped in at least partly separate neural substrates.

Aged↗

PubMed2003

Temporary and permanent signs of interhemispheric disconnection after traumatic brain injury.

The corpus callosum is frequently damaged by closed head traumas, and the resulting deficits of interhemispheric communication may vary according to the specific position of the lesion within the corpus callosum. This paper describes a single case who suffered a severe traumatic brain injury resulting in a lesion of the posterior body of the corpus callosum. Among the classical symptoms of interhemispheric disconnection, left hand anomia, left upper limb ideomotor dyspraxia, left visual field dyslexia and dysnomia, and left ear suppression in a dichotic listening task were observed shortly after the injury but recovered completely or almost completely with the passage of time. The only symptom of interhemispheric disconnection which was found to persist more than 4 years after the injury was an abnormal prolongation of the crossed-uncrossed difference in a simple visuomotor reaction time task. This prolongation was comparable with that observed in subjects with complete callosal lesions or agenesis. The results suggest that the posterior body of the corpus callosum may be an obligatory interhemispheric communication channel for mediating fast visuo-motor responses. The transient nature of other symptoms of interhemispheric disconnection suggests a relatively wide dispersion of fibers with different functions through the callosal body, such that parts of them can survive a restricted lesion and allow functional recovery of hemispheric interactions. An assessment of the evolution in time of symptoms of interhemispheric disconnection following restricted callosal lesions may reveal fine and coarse features of the anatomo-functional topography of the corpus callosum.

Adult↗