Eugen Diesch

A perceptual interference account of acquisition difficulties for non-native phonemes

This article presents an account of how early language experience can impede the acquisition of non-native phonemes during adulthood. The hypothesis is that early language experience alters relatively low-level perceptual processing, and that these changes interfere with the formation and adaptability of higher-level linguistic representations. Supporting data are presented from an experiment that tested the perception of English /r/ and /l/ by Japanese, German, and American adults. The underlying perceptual spaces for these phonemes were mapped using multidimensional scaling and compared to native-language categorization judgments. The results demonstrate that Japanese adults are most sensitive to an acoustic cue, F2, that is irrelevant to the English /r/-/l/ categorization. German adults, in contrast, have relatively high sensitivity to more critical acoustic cues. The results show how language-specific perceptual processing can alter the relative salience of within- and between-category acoustic variation, and thereby interfere with second language acquisition.

Topographic and Temporal Indices of Vowel Spectral Envelope Extraction in the Human Auditory Cortex

The audirory-evoked neuromagnetic field elicited by single vowel formants and two-formant vowels was recorded under active listening conditions using a 37-channel magnetometer. There were three single formants with formant with a formant frequency of 200, 400, and 800 Hz, another single fromant with a fromant frequency of 2600 Hz, and three vowels that were constructed by linear superimposition of the high-onto one of the low-frequency formants. P50m and N100m latency values were inversely correlated with the formant frequency of single location was obtained along the postero-anterior axiz, which is orthogonal to the well-established latero-medial tonotopic gradient. Regardless of whether single formants or first formants of vowels were considered N100m sources were more anterior and sustained field sources wre more posterior for higher-frequency than for lower-frequency formants. The velocity of the apparent posterior-to-anterior movement across cortical sorface of N100m sources first reported by Rogers et al. [Rogers, R.L., Papanicolaou, A.C., Baumann, S.B., Saydjari,C., & Eisenberg, H.M. (1990). Neuromagnetic evidence of a dynamic excitation pattern generating the N100 auditory response. Electroencephalography and Clinical Neurophy-siology,77,237-240] decreased as a function of latency. The amount of deceleration was positively correlated with formant frequency. responses to the vowels were superadditive, indicating that the processes elicited by the constituents of composite stumuli interact at one or more stages of the afferent auditory pathway. Such interaction may account for the absence of a lateral-to-medial tonotopic mapping of first formant frequency. The source topography found may reflect activity in auditory fields adjacent to AI with the strenght of the contribution varying with formant frequency. Altematively, it may reflect sharpness-of-tuning and inhbitory response-area asymmetry gradients along isofrequency stripes within AI. Either alternative may be interpreted in terms of a sprctral blurring mechanism that abstracts spectral envelope information form the details of spectral composition, an important step towards the formation of invariant phonetic percepts.

Multiple frequency steady-state evoked magnetic field mapping of digit representation in primary somatosensory cortex.

Magnetic source imaging of multiple frequency steady-state somatosensory evoked responses was examined using a 151-channel magnetoencephalography (MEG) system and a dual-channel electrical stimulator. Somatotopy of digit representation was studied in healthy subjects and effects of injury-related cortical plasticity in patients with unilateral transections of the median or the ulnar nerve. Dipole source locations exhibited somatotopic order with overlap between neighboring digits. In two of three nerve injury patients evidence for cortical reorganization was found. The location of sources related to digits neighboring deafferented digits was changed and their dipole moments were enlarged by comparsion with the sources related to contralateral homologue control digits. As a basis for magnetic source imaging, the recording of multiple frequency somatosensory steady-state evoked responses may be a viable and time saving alternative to the recording of transient evoked responses.Magnetic source imaging of multiple frequency steady-state somatosensory evoked responses was examined using a 151-channel magnetoencephalography (MEG) system and a dual-channel electrical stimulator. Somatotopy of digit representation was studied in healthy subjects and effects of injury-related cortical plasticity in patients with unilateral transections of the median or the ulnar nerve. Dipole source locations exhibited somatotopic order with overlap between neighboring digits. In two of three nerve injury patients evidence for cortical reorganization was found. The location of sources related to digits neighboring deafferented digits was changed and their dipole moments were enlarged by comparsion with the sources related to contralateral homologue control digits. As a basis for magnetic source imaging, the recording of multiple frequency somatosensory steady-state evoked responses may be a viable and time saving alternative to the recording of transient evoked responses.

The magnetic mismatch field elicited by words and phonological non-words

THE speech-evoked magnetic mismatch field was measured using a 49-channel gradiometer. The standard stimuli were words in one condition and phonological non-words in another condition. The deviants were nonwords throughout. The equivalent current dipole fitted to the mismatch field was deeper inside the brain and its dipole moment was stronger for non-word than word standards. The factor structure of field amplitude, source dipole moment, and depth suggested that the lexicality conditions differed in source surface area and depth, but not in source current density. This lexicality effect is compatible with a modular rather than an interactive view of the relationship between lexical and phonetic representation.

Structural changes of the corpus callosum in tinnitus

Objectives: In tinnitus, several brain regions seem to be structurally altered, including the medial partition of Heschls gyrus (mHG), the site of the primary auditory cortex. The mHG is smaller in tinnitus patients than in healthy controls. The corpus callosum (CC) is the main interhemispheric commissure of the brain connecting the auditory areas of the left and the right hemisphere. Here, we investigate whether tinnitus status is associated with CC volume. Methods: The midsagittal cross-sectional area of the CC was examined in tinnitus patients and healthy controls in which an examination of the mHG had been carried out earlier. The CC was extracted and segmented into subregions which were defined according to the most common CC morphometry schemes introduced by Witelson (1989) and Hofer and Frahm (2006). Results: For both CC segmentation schemes, the CC posterior midbody was smaller in male patients than in male healthy controls and the isthmus, the anterior midbody, and the genou were larger in female patients than in female controls. With CC size normalized relative to mHG volume, the normalized CC splenium was larger in male patients than male controls and the normalized CC splenium, the isthmus and the genou were larger in female patients than female controls. Normalized CC segment size expresses callosal interconnectivity relative to auditory cortex volume. Conclusion: It may be argued that the predominant function of the CC is excitatory. The stronger callosal interconnectivity in tinnitus patients, compared to healthy controls, may facilitate the emergence and maintenance of a positive feedback loop between tinnitus generators located in the two hemispheres.

Is the effect of tinnitus on auditory steady-state response amplitude mediated by attention?

Objectives: Auditory steady-state response (ASSR) amplitude enhancement effects have been reported in tinnitus patients. As ASSR amplitude is also enhanced by attention, the effect of tinnitus on ASSR amplitude could be interpreted as an effect of attention mediated by tinnitus. As N1 attention effects are significantly larger than those on the ASSR, if the effect of tinnitus on ASSR amplitude were due to attention, there should be similar amplitude enhancement effects in tinnitus for the N1 component of the auditory-evoked response. Methods: MEG recordings which were previously examined for the ASSR (Diesch et al., 2010a) were analyzed with respect to the N1m component. Like the ASSR previously, the N1m was analyzed in the source domain (source space projection). Stimuli were amplitude-modulated (AM) tones with one of three carrier frequencies matching the tinnitus frequency or a surrogate frequency 1½ octave above the audiometric edge frequency in controls, the audiometric edge frequency, and a frequency below the audiometric edge. Single AM-tones were presented in a single condition and superpositions of three AM-tones differing in carrier and modulation frequency in a composite condition. Results: In the earlier ASSR study (Diesch et al., 2010a), the ASSR amplitude in tinnitus patients, but not in controls, was significantly larger in the (surrogate) tinnitus condition than in the edge condition. Patients showed less evidence than controls of reciprocal inhibition of component ASSR responses in the composite condition. In the present study, N1m amplitudes elicited by stimuli located at the audiometric edge and at the (surrogate) tinnitus frequency were smaller than N1m amplitudes elicited by sub-edge tones both in patients and controls. The relationship of the N1m response in the composite condition to the N1m response in the single condition indicated that reciprocal inhibition among component N1m responses was reduced in patients compared against controls. Conclusions: In the present study, no evidence was found for an N1-amplitude enhancement effect in tinnitus. Compared to controls, reciprocal inhibition is reduced in tinnitus patients. Thus, as there is no effect on N1m that could potentially be attributed to attention, it seems unlikely that the enhancement effect of tinnitus on ASSR amplitude could be accounted for in terms of attention induced by tinnitus.

Contextual modulation of pain in masochists: involvement of the parietal operculum and insula.

Abstract Pain can be modulated by contextual stimuli, such as emotions, social factors, or specific bodily perceptions. We presented painful laser stimuli together with body-related masochistic visual stimuli to persons with and without preferred masochistic sexual behavior and used neutral, positive, and negative pictures with and without painful stimuli as control. Masochists reported substantially reduced pain intensity and unpleasantness in the masochistic context compared with controls but had unaltered pain perception in the other conditions. Functional magnetic resonance imaging revealed that masochists activated brain areas involved in sensory-discriminative processing rather than affective pain processing when they received painful stimuli on a masochistic background. The masochists compared with the controls displayed attenuated functional connectivity of the parietal operculum with the left and right insulae, the central operculum, and the supramarginal gyrus. Masochists additionally showed negative correlations between the duration of interest in masochistic activities and activation of areas involved in motor activity and affective processing. We propose that the parietal operculum serves as an important relay station that attenuates the affective-motivational aspects of pain in masochists. This novel mechanism of pain modulation might be related to multisensory integration and has important implications for the assessment and treatment of pain.

Cross‐language tests of the perceptual magnet effect for /inverted are/ and /l/

Recent experiments by Iverson and Kuhl have suggested that the perceptual organization of the American English /inverted are/ and /l/ categories is strongly influenced by category goodness. American adult listeners exhibit a perceptual magnet effect characterized by low sensitivity and perceptual clustering near the best exemplars of /inverted are/ and /l/ and high sensitivity and stretched perceptual distances near the worst exemplars. The present study compares the responses of native German and English speakers to evaluate whether the representation of these categories is influenced by language experience. In separate experiments, natural phonemes of adult German (/inverted are/ and /l/) and American (/inverted are/ and /l/) speakers were recorded, and synthesized American English /inverted are/ and /l/ tokens were identified, discriminated, rated for category goodness, and rated for similarity by both groups of subjects. The results demonstrate that German listeners prefer, produce, and have perceptua...

Visual search in arrays with single and multiple objects: Differences and overlap of activation in the human attention system

If subjects search for a target that differs from distracters just in terms of a conjunction of elementary visual features, search time increases with the number of distracters. By contrast, search time is independent of the number of distracters if the target carries a unique visual feature. This indicates the necessity of spatial attention for feature binding (1). Theoretically, the binding problem arises during exposure to multiple visual objects. Therefore, Luck et al. have proposed that spatial attention is only employed in conjunction search if subjects are presented with arrays containing multiple visual objects (2). Using fMRI, we have previously delineated a cortical attention network for conjunction search (3). In the present study, we investigated whether areas of this network would also display attentional modulation during a conjunction search in displays containing only one visual object.