Biomedical subjects

Nadia Bolognini

Publications and source records attributed to Nadia Bolognini.

5 recordsLinked to original sources

PubMed2005

Visual search improvement in hemianopic patients after audio-visual stimulation.

One of the most effective techniques in the rehabilitation of visual field defects is based on implementation of oculomotor strategies to compensate for visual field loss. In the present study we develop a new rehabilitation approach based on the audio-visual stimulation of the visual field. Since it has been demonstrated that audio-visual interaction in multisensory neurons can improve temporally visual perception in patients with hemianopia, the aim of the present study was to verify whether a systematic audio-visual stimulation might induce a long-lasting amelioration of visual field disorders. Eight patients with chronic visual field defects were trained to detect the presence of visual targets. During the training, the visual stimulus could be presented alone, i.e. unimodal condition, or together with an acoustic stimulus, i.e. crossmodal conditions. In the crossmodal conditions, the spatial disparity between the visual and the acoustic stimuli were systematically varied (0, 16 and 32 degrees of disparity). Furthermore, the temporal interval between the acoustic stimulus and the visual target in the crossmodal conditions was gradually reduced from 500 to 0 ms. Patients underwent the treatment for 4 h daily, over a period of nearly 2 weeks. The results showed a progressive improvement of visual detections during the training and an improvement of visual oculomotor exploration that allowed patients to efficiently compensate for the loss of vision. More interesting, there was a transfer of treatment gains to functional measures assessing visual field exploration and to daily-life activities, which was found stable at the 1 month follow-up control session. These findings are very promising with respect to the possibility of taking advantage of human multisensory capabilities to recover from unimodal sensory impairments.

Acoustic Stimulation↗

PubMed2005

Visual localization of sounds.

Circumscribed hemispheric lesions in the right hemisphere have been shown to impair auditory spatial functions. Due to a strong crossmodal links that exist between vision and audition, in the present study, we have hypothesized that multisensory integration can play a specific role in recovery from spatial representational deficits. To this aim, a patient with severe auditory localization defect was asked to indicate verbally the spatial position where the sound was presented. The auditory targets were presented at different spatial locations, at 8 degrees, 24 degrees, 40 degrees, 56 degrees to either sides of the central fixation point. The task was performed either in a unimodal condition (i.e., only sounds were presented) or in crossmodal conditions (i.e., a visual stimulus was presented simultaneously to the auditory target). In the crossmodal conditions, the visual cue was presented either at the same spatial position as the sound or at 16 degrees or 32 degrees, nasal or temporal, of spatial disparity from the auditory target. The results showed that a visual stimulus strongly improves the patient's ability to localize the sounds, but only when it was presented in the same spatial position of the auditory target.

Acoustic Stimulation↗

PubMed2005

Audiovisual integration in patients with visual deficit.

In the present study, we investigated the possibility that bimodal audiovisual stimulation of the affected hemifield can improve perception of the visual events in the blind hemifield of hemianopic patients, as it was previously demonstrated in neglect patients. Moreover, it has been shown that "hetero-modal" and "sensory-specific" cortices are involved in cross-modal integration. Thus, the second aim of the present study was to examine whether audiovisual integration influences visual detection in patients with different cortical lesions responsible of different kinds of visual disorders. More specifically, we investigated cross-modal, audiovisual integration in patients with visual impairment due to a visual field deficit (e.g., hemianopia) or visuospatial attentional deficit (e.g., neglect) and patients with both hemianopia and neglect. Patients were asked to detect visual stimuli presented alone or in combination with auditory stimuli that could be spatially aligned or not with the visual ones. The results showed an enhancement of visual detection in cross-modal condition (spatially aligned condition) comparing to unimodal visual condition only in patients with hemianopia or neglect; by contrast, the multisensory integration did not occur when patients presented both deficits. These data suggest that patients with visual disorders can enormously benefit the multisensory integration. Moreover, they showed a different influence of cortical lesion on multisensory integration. Thus, the present results show the important adaptive meaning of multisensory integration and are very promising with respect to the possibility of recovery from visual and spatial impairments.

Acoustic Stimulation↗

PubMed2004

"Acoustical vision" of below threshold stimuli: interaction among spatially converging audiovisual inputs.

Crossmodal spatial integration between auditory and visual stimuli is a common phenomenon in space perception. The principles underlying such integration have been outlined by neurophysiological and behavioral studies in animals; this study investigated whether the integrative effects observed in animals also apply to humans. In this experiment we systematically varied the spatial disparity (0 degrees, 16 degrees, and 32 degrees) and the temporal interval (0, 100, 200, 300, 400, and 500 ms) between the visual and the auditory stimuli. Normal subjects were required to detect visual stimuli presented below threshold either in unimodal visual conditions or in crossmodal audiovisual conditions. Signal detection measures were used. An enhancement of the perceptual sensitivity (d') for luminance detection was found when the audiovisual stimuli followed a simple spatial and temporal rule, governing multisensory integration at the neuronal level.

Acoustic Stimulation↗

PubMed2002

Enhancement of visual perception by crossmodal visuo-auditory interaction.

Neurophysiological studies have shown in animals that a sudden sound enhanced perceptual processing of subsequent visual stimuli. In the present study, we explored the possibility that such enhancement also exists in humans and can be explained through crossmodal integration effects, whereby the interaction occurs at the level of bimodal neurons. Subjects were required to detect visual stimuli in a unimodal visual condition or in crossmodal audio-visual conditions. The spatial and the temporal proximity of multisensory stimuli were systematically varied. An enhancement of the perceptual sensitivity (d') for luminance detection was found when the audiovisual stimuli followed a rather clear spatial and temporal rule, governing multisensory integration at the neuronal level.

Adult↗