Biomedical subjects

Brigitte Röder

Publications and source records attributed to Brigitte Röder.

5 recordsLinked to original sources

PubMed2002

Crossmodal and intermodal attention modulate event-related brain potentials to tactile and auditory stimuli.

An increasing number of animal and human studies suggests that different sensory systems share spatial representations in the brain. The aim of the present study was to test whether attending to auditory stimuli presented at a particular spatial location influences the processing of tactile stimuli at that position and vice versa (crossmodal attention). Moreover, it was investigated which processing stages are influenced by orienting attention to a certain stimulus modality (intermodal attention). Event-related brain potentials (ERPs) were recorded from 15 participants while tactile and auditory stimuli were presented at the left or right side of the body midline. The task of the participants was to attend to either the auditory or to the tactile modality, and to respond to infrequent double-stimuli of either the left or right side. Results showed that spatial attention modulated both early and late somatosensory and auditory ERPs when touch and tones were relevant, respectively. Moreover, early somatosensory (N70-100, N125-175) and auditory (N100-170) potentials, but not later deflections, were affected by spatial attention to the other modality, suggesting bi-directional crossmodal links between hearing and touch. Additionally, ERPs were modulated by intermodal selection mechanisms: stimuli elicited enhanced negative early and late ERPs when they belonged to the attended modality compared to those that belonged to the unattended modality. The present results provide evidence for the parallel influence of spatial and intermodal selection mechanisms at early processing stages while later processing steps are restricted to the relevant modality.

Acoustic Stimulation↗

PubMed2002

Influence of visual information on the auditory median plane of the head.

When determining the position of sounds, people perceive their subjective auditory median plane of the head (SAMP) displaced towards the side to which the head is turned. The present study investigated the influence of visual input on this effect. A group of congenitally blind and two groups of sighted adults, one with eyes open, one with eyes closed, adjusted the location of a tone presented through headphones in such a way that they perceived it to originate at their SAMP, both with the head straight ahead and turned 60 degrees to the right. While both sighted groups showed a reliable SAMP displacement in the 60 degrees condition, the congenitally blind did not. It is speculated that the blind have learned to integrate proprioceptive information more precisely contributing to superior auditory localization skills.

Adaptation, Physiological↗

PubMed2002

Assessing the effect of posture change on tactile inhibition-of-return.

If a peripheral target follows an ipsilateral cue with a stimulus-onset-asynchrony (SOA) of 300 ms or more, its detection is delayed compared to a contralateral-cue condition. This phenomena, known as inhibition-of-return (IOR), affects responses to visual, auditory, and tactile stimuli, and is thought to provide an index of exogenous shifts of spatial attention. The present study investigated whether tactile IOR occurs in a somatotopic vs an allocentric frame of reference. In experiment 1, tactile cue and target stimuli were presented to the index and middle fingers of either hand, with the hands positioned in an uncrossed posture (SOA 500 or 1,000 ms). Speeded target detection responses were slowest for targets presented from the cued finger, and were also slower for targets presented to the adjacent finger on the cued hand than to either finger on the uncued hand. The same pattern of results was also reported when the index and middle fingers of the two hands were interleaved on the midline (experiment 2), suggesting that the gradient of tactile IOR surrounding a cued body site is modulated by the somatotopic rather than by the allocentric distance between cue and target.

Adolescent↗

PubMed2002

Brain activation modulated by the comprehension of normal and pseudo-word sentences of different processing demands: a functional magnetic resonance imaging study.

Recent data from lesion and brain imaging studies have questioned the well-established assumption of a close functional-anatomic link between syntax and Broca's area and semantics and Wernicke's area. In the present study we used functional magnetic resonance imaging (fMRI) to investigate the neuroanatomical correlates of semantic and syntactic functions and possible interdependencies between the related brain systems. In a completely crossed design we varied syntactic processing demands (easy vs difficult to process word order sequences) and the meaningfulness of sentences (real- vs pseudo-word sentences). In comparison to a backward speech condition we found an activation of the left perisylvian region, including the left inferior frontal cortex and the left superior and middle temporal gyri. Semantic in contrast to pseudo-word sentences elicited a stronger activation in both the anterior and the posterior perisylvian cortex. Syntactic difficulty had its strongest effect within the left inferior frontal region and this effect was more pronounced for semantic than nonsemantic speech. These results suggest that semantic and syntactic language functions are mediated by partly specialized brain systems but that there nevertheless exists a substantial functional overlap of the involved brain structures.

Adult↗

PubMed2002

Speech processing activates visual cortex in congenitally blind humans.

Neurophysiological recordings and neuroimaging data in blind and deaf animals and humans suggest that perceptual functions may be organized differently after sensory deprivation. It has been argued that neural plasticity contributes to compensatory performance in blind humans, such as faster speech processing. The present study employed functional magnetic resonance imaging (fMRI) to map language-related brain activity in congenitally blind adults. Participants listened to sentences, with either an easy or a more difficult syntactic structure, which were either semantically meaningful or meaningless. Results show that blind adults not only activate classical left-hemispheric perisylvian language areas during speech comprehension, as did a group of sighted adults, but that they additionally display an activation in the homologueous right-hemispheric structures and in extrastriate and striate cortex. Both the perisylvian and occipital activity varied as a function of syntactic difficulty and semantic content. The results demonstrate that the cerebral organization of complex cognitive systems such as the language system is significantly shaped by the input available.

Adult↗