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Biomedical subjects

Susanne Leiberg

Publications and source records attributed to Susanne Leiberg.

7 recordsLinked to original sources
PubMed2006

BOLD adaptation in vibrotactile stimulation: neuronal networks involved in frequency discrimination.

The present functional magnetic resonance imaging (fMRI) study investigated human brain regions subserving the discrimination of vibrotactile frequency. An event-related adaptation paradigm was used in which blood-oxygen-level-dependent (BOLD) responses are lower to same compared with different pairs of stimuli (BOLD adaptation). This adaptation effect serves as an indicator for feature-specific responding of neuronal subpopulations. Subjects had to discriminate two vibrotactile stimuli sequentially applied with a delay of 600 ms to their left middle fingertip. The stimulus frequency was in the flutter range of 18-26 Hz. In half of the trials, the two stimuli possessed identical frequency (same), whereas in the other half, a frequency difference of +/-2 Hz was used (diff). As a result, BOLD adaptation was observed in the contralateral primary somatosensory cortex (S1), precentral gyrus, superior temporal gyrus (STG); ipsilateral insula as well as bilateral secondary somatosensory cortex and supplementary motor area. When statistically comparing the BOLD time courses between same and diff trials in these cortical areas, it was found that the vibrotactile BOLD adaptation is initiated in the contralateral S1 and STG simultaneously. These findings suggest that the cortical areas responsive to the frequency difference between two serially presented stimuli sequentially process the frequency of a vibrotactile stimulus and constitute a putative neuronal network underlying human vibrotactile frequency discrimination.

Adaptation, Physiological↗
PubMed2006

Effects of memory load on cortical oscillatory activity during auditory pattern working memory.

The present magnetoencephalography study investigated memory load-dependent changes in cortical oscillatory activity during a modified auditory version of the Sternberg paradigm. Twelve subjects were presented with test stimulus sets of 1-3 syllables spoken in a natural female voice. After an 800-ms delay period, a probe syllable was presented and subjects had to judge whether the probe had been included in the preceding test set. Compared to a non-memory-control task, memory trials elicited an increase of beta activity over right temporal regions and an increase of alpha activity over right middle prefrontal cortex at the end of the delay phase. Monotonic increases in spectral amplitude as a function of memory load were revealed for the beta band over right temporal sensors and the alpha band over right frontal sensors during the delay period. The results demonstrate the relevance of both beta and alpha oscillations for the memorization of multiple stimuli. The former may be associated with the representation of task-relevant stimulus features, while the latter may reflect the top-down control of these representations.

Acoustic Stimulation↗
PubMed2006

Gamma-band activity dissociates between matching and nonmatching stimulus pairs in an auditory delayed matching-to-sample task.

Electro- and magnetoencephalography studies have suggested that increased gamma-band activity (GBA) is a correlate of activated neural stimulus representations. In this study, a delayed matching-to-sample paradigm for auditory spatial information was employed to investigate the role of magnetoencephalographic gamma-band activity in the differentiation between matching and nonmatching stimulus pairs. Twelve subjects made same-different judgments about the lateralization angle of pairs of filtered noise stimuli (S1 and S2) presented with 0.8-s delays. One half of the subjects had to respond to matching stimulus pairs, the other half to nonmatching stimulus pairs. Cortical oscillatory activity in the memory task was compared to a control task requiring the detection of background noise intensity changes. Memory-related GBA increases were revealed over midline parietal areas in the middle of the delay phase and during the presentation of S2 and over frontocentral areas at the end of the delay phase. This replicated previous findings. In addition, nonmatching trials were associated with increased GBA over right parietal areas in response to S2. The midline parietal GBA increase during S2 in the memory condition may have reflected the representation of S1 needed for a comparison between S1 and S2. When S1 and S2 were identical, no further representation was required. In contrast, for nonmatching pairs, a second representation was activated over right parietal areas.

Adult↗
PubMed2006

The multiple facets of empathy: a survey of theory and evidence.

Empathy is the ability to perceive and understand other people's emotions and to react appropriately. This ability is a necessary prerequisite for successful interpersonal interaction. Empathy is a multifaceted construct including low-level mechanisms like emotional contagion as well as high-level processes like perspective-taking. The ability to empathize varies between individuals and is considered a stable personality trait: some people are generally more successful in empathizing than others. In this chapter we will first present different conceptualizations of the construct of empathy, and refer to empathy-regulating processes as well as to the relationship between empathy and social behavior. Then, we will review peripheral physiological and brain imaging studies pertaining to low- and high-level empathic processes, empathy-modulating processes, and the link between empathy and social behavior. Further, we will present evidence regarding interindividual differences in these processes as an important source of information for solving the conundrum of how the comprehension of others' emotions is achieved by our brains.

Brain↗
PubMed2005

Cortical oscillatory activity during spatial echoic memory.

In human magnetoencephalogram, we have found gamma-band activity (GBA), a putative measure of cortical network synchronization, during both bottom-up and top-down auditory processing. When sound positions had to be retained in short-term memory for 800 ms, enhanced GBA was detected over posterior parietal cortex, possibly reflecting the activation of higher sensory storage systems along the hypothesized auditory dorsal space processing stream. Additional prefrontal GBA increases suggested an involvement of central executive networks in stimulus maintenance. The present study assessed spatial echoic memory with the same stimuli but a shorter memorization interval of 200 ms. Statistical probability mapping revealed posterior parietal GBA increases at 80 Hz near the end of the memory phase and both gamma and theta enhancements in response to the test stimulus. In contrast to the previous short-term memory study, no prefrontal gamma or theta enhancements were detected. This suggests that spatial echoic memory is performed by networks along the putative auditory dorsal stream, without requiring an involvement of prefrontal executive regions.

Acoustic Stimulation↗
PubMed2002

The Obsessive-Compulsive Inventory: development and validation of a short version.

This article reports on the development of a revised version of the Obsessive-Compulsive Inventory (OCI; E. B. Foa, M. J. Kozak, P. Salkovskis, M. E. Coles, & N. Amir, 1998), a psychometrically sound, theoretically driven, self-report measure. The revised OCI (OCI-R) improves on the parent version in 3 ways: It eliminates the redundant frequency scale, simplifies the scoring of the subscales, and reduces overlap across subscales. The reliability and validity of the OCI-R were examined in 215 patients with obsessive-compulsive disorder (OCD), 243 patients with other anxiety disorders, and 677 nonanxious individuals. The OCI-R, which contains 18 items and 6 subscales, has retained excellent psychometric properties. The OCI-R and its subscales differentiated well between individuals with and without OCD. Receiver operating characteristic (ROC) analyses demonstrated the usefulness of the OCI-R as a diagnostic tool for screening patients with OCD, utilizing empirically derived cutscores.

Adult↗