Susan C. Etlinger

Brain electrical mechanisms of bilingual speech management: an initial investigation☆

This exploratory study deals with EEG changes in 3 professional interpreters while mentally interpreting from their mother language into foreign languages and vice versa. EEGs were recorded while interpreting and compared with the periods at rest between these periods of interpreting. Significant (P < 0.05) changes of coherence between all pairs of electrodes with respect to the averaged EEG at rest were computed for 5 frequency bands between 4 and 32 Hz. The verbal tasks were control-compared with comparable coherence measures for mental arithmetic and listening to music. Interindividual differences predominated, but certain common characteristics of the EEG measures were also found. The temporal regions were most involved in interpreting and particularly in the uppermost beta band (24-32 Hz). More coherence increases--particularly in the right hemisphere--were found while interpreting into the foreign than into the native language. Coherence changes were found to accumulate in certain regions of the scalp as pivots or focal areas which apparently have functional significance for the task in question as nodal points of information exchange and/or transfer. Such pivots were found in T3 more than in T4 (in the right-handers) and vice versa in a left-hander. Theta and alpha bands behaved differently and did not show such clear-cut differences. The results during mental arithmetic and listening to music were different from the ones while interpreting. The results give support to the conception of the cortex as a network serving the greatest possible divergence and convergence of signals.

Event-related neuronal responses in the human strio-pallido-thalamic system. I. Sensory and motor functions

Multiunit activity was recorded from strio-pallido-thalamic sites in parkinsonian patients bearing gold electrodes for diagnosis and therapy. The patients voluntarily participated in tasks designed to study neuronal correlates of both physical and semantic characteristics of stimuli as well as motor responses. Six modifications of the stimulus-response paradigm were used: visual odd-ball, visual and acoustic odd-ball tasks; tasks in which either the stimulus intensity or the meaning of non-target stimuli varied; single-stage delayed response and dual-stage delayed response tasks, respectively. In each task the patients had to evaluate some of the stimulus characteristics and to respond in a particular way according to the preliminary instructions. Peristimulus time histograms for each multiunit separately as well as profiles of reactions and profiles of reaction differences for the whole set of multiunits were calculated and subjected to statistical analysis. Two functional groups of subcortical neuronal reactions, stimulus-related and response-related activities, were separated. The stimulus-related activities of most multiunits were modality-unspecific. Their most striking feature was dependence on stimulus relevance and also its probability, the strongest reactions observed in response to task relevant stimuli occurring with low probability. The response-related activities occurred prior to initiation of movements, dependent upon the particular action and its probability. The data suggest at least two different and spatially overlapping subcortical channels responsible for goal-directed behaviour: the one related to stimulus assessment and the other to preparation for motor action.

Human thalamic and pallidal neuronal responses to visual stimuli in a threshold recognition task

Multiunit activity was recorded from 80 different subcortical sites in 9 parkinsonian patients bearing gold electrodes for diagnosis and therapy. The patients participated in a visual recognition task in which the stimuli (digits) were presented on a LED matrix at threshold. The exposure times were so chosen that in about half the trials the patient failed to recognize the digit correctly. Peristimulus time histograms for each neuronal population as well as profiles of reactions for the groups of neuronal populations localized in the N. ventro-lateralis thalami and the globus pallidus, respectively, were analysed statistically, contrasting the cases of correct recognition with those of non-recognition. Different types of response, possibly related to different stages of task performance, were separated: an early type with onset latencies ranging from 80 to 160 msec, two middle types with onset latencies ranging from 200 to 300 msec, and a type characterized by slow shifts in the discharge rate beginning 400-600 msec post stimulus. Most of the significant differences in the discharge rate between qualities of recognition were found in the middle-type responses and in the slow shifts, shorter latencies and larger amplitudes accompanying correct recognition.

EEG Aspects of Musical Thinking: listening, imagining and composing

The main aim of this contribution was to demonstrate a way of objectifying various aspects of musical thinking by analysing the continuously running EEG. In this respect, the determination of coherence between the brain‐electric activities at all possible recording sites (i.e., 171, for the 19 electrodes we use), together with power at these sites proved to be a useful method. For data reduction, only statistically significant differences between resting periods (usually 1 min) and periods of musical thinking were considered. This procedure was performed for each of six frequency bands between 1 and 31.5 Hz. The results of both group and individual experiments are reported. In group studies, listening to music involved mainly the temporal regions of both hemispheres, yet in different frequency ranges. The results proved to be specific and clearly differed from those obtained during tasks involving mental arithmetic, silent reading, listening to text and others. Moreover, musically trained subjects produce...

Spontaneous cortical DC-potential shifts: Modulation stereotypy; relationships to higher EEG-frequencies

A description of scalp-recorded, spontaneous, cerebral DC-potential shifts is given independent of other variables (shift stereotypy), in relationship to higher frequencies (theta, alpha 1, alpha 2: 4-13 Hz) and as analyzed pairwise across the median sagittal line (Fz, Cz, Pz) separately according to frequency and condition (relaxation and moderate mental load). Spontaneous DC-shifts are shown to behave unpredictably. Whether measured jointly (up to triads) or as dyad and triad context entropy, the frontal DC-shifts are calculated as being random, whereby their definition as such within the context of the Principle Component Analysis is supported by the analysis of longitudinal registrations. Cross-correlation analysis of the cerebral slow potentials relationship to each of the higher frequencies (theta, alpha 1, alpha 2) reveals it to be highly independent, the highest correlation accounting for merely 11% of the common variance, the average being 9% (R congruent to 0.3). By matching the conjoint activity of the DC-potential between Fz-Cz, Cz-Pz, and Fz-Pz to that of theta, alpha 1, alpha 2 at the same paired sites, the DC-activity is shown to be operating at higher levels of synchronous activity than the higher frequencies, regardless of pairing and/or condition, although the general level of synchronous activity (DC, theta, alpha 1, alpha 2) is remarkably high along the median sagittal line, 75% of the correlation averages of all analysis-pairings being above 0.60.