Biomedical subjects

S C Etlinger

Publications and source records attributed to S C Etlinger.

10 recordsLinked to original sources

PubMed1999

Selection of actions in the basal ganglia-thalamocortical circuits: review and model.

The paper reviews the 20-year experience of recording impulse activity of neurons in the basal ganglia-thalamocortical circuits. These recordings were made from patients with Parkinson's disease who failed to respond to conventional medical treatment and who had undergone stereotaxic neurosurgery. When taken together, the results show that: (1) the basal ganglia-thalamocortical circuits become active only when a stimulus is attended or when a movement is voluntarily implemented, i.e. they are involved in the process of selection of an appropriate sensory stimulus for advanced processing and in the process of selection of an appropriate motor action for achieving a certain goal; (2) neuronal circuits responsible for assessment actions and for motor acts are segregated; (3) inhibitory opponent neuronal mechanisms are implemented for initiating and suppressing inappropriate actions; and (4) preparation to make different assessment actions (attentional set) is associated with different preparatory activities. To explain these findings a hypothesis of action programming has been formulated. According to it, the whole of human behavior is divided into separate sensory-motor-cognitive actions, while the brain in turn is divided into separate systems playing different roles in the organization of actions. The system for action selection that includes the basal ganglia-thalamic circuits plays a critical role in initiation of, preparation for, and suppression of these actions. The neuronal mechanisms for the system for action selection including mapping of actions, 'winner takes all' operations in the striatum, disinhibition and inhibition process in the thalamus are suggested and discussed.

Attention↗

PubMed1997

Human multiunit activity related to attention and preparatory set.

The impulse activity of 183 multiunits was recorded from the premotor cortex, the caudate nucleus, the globus pallidus and the thalamus in 15 Parkinson's disease patients bearing inert gold electrodes implanted for diagnosis and therapy. The patients performed a task in which stimulus triplets (each consisting of two informational and one trigger stimulus) were presented. The patients initiated or inhibited actions (naming or counting) depending on the particular informational stimuli, thus allowing discrimination between different components of multiunit responses associated with attention and preparatory set and with disengagement from these states. The data indicate the existence of two overlapping circuits: one responsible for preparation for and assessment of the behavioral meaning of the stimulus and the other responsible for preparation for and performance of verbal action.

Adult↗

PubMed1993

Theodor Meynert's contribution to classical 19th century aphasia studies.

Carl Wernicke (1848-1905) is traditionally considered the first to have described the features of, and the brain pathology underlying, impaired auditory comprehension and related symptoms. Although Wernicke (1874) clearly and repeatedly indicates his indebtedness to Theodor von Meynert (1833-1892), this is usually understood as an acknowledgment that Meynert taught Wernicke neuroanatomy (Eggert, 1977); Wernicke's own words in part support this interpretation. A more sophisticated historical analysis notes that, prior to Wernicke, both Johann Schmidt in 1871 and Charlton Bastian in 1869 had described the concept of receptive aphasia, but neither had supported their analyses with autopsy evidence as did Wernicke, thus not dislodging Wernicke's claim of priority. However, a virtually unknown work by Theodor von Meynert, published in 1866, has recently been rediscovered by us ["Ein Fall von Sprachstörung, anatomisch begründet." Medizinische Jahrbücher. XII Band der Zeitschrift der K. K. Gesellleschaft der Arzte in Wien, 22. Jahr. Pp. 152-189]. In this paper Meynert analyzes the anatomical basis for localizing the comprehension of language in the superior temporal gyrus, he argues that lesions in this area should (by analogy to Broca's earlier observations on language expression) cause impairments in language comprehension, and he presents a case of receptive aphasia with autopsy evidence of destruction of the superior temporal gyrus in the left hemisphere. The patient's aphasia was classic; impaired auditory comprehension, and fluent speech with paraphasias. It is clear that Meynert should be given historical credit for his work.

Aphasia↗

PubMed1993

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.

Brain↗

PubMed1991

Human depth ERP in a visual threshold recognition task.

Event-related potentials (ERPs) were recorded from the globus pallidus, the N. ventro-lateralis thalami and adjacent areas in parkinsonian patients bearing gold electrodes for diagnosis and therapy. The patients participated in a recognition task in which visual stimuli (digits) were presented at threshold durations. The ERPs from each single recording site, as separate histograms and then in combination as composite histograms across all recording sites ('profiles of reactions' and 'profiles of reaction differences'), were computed for 3 response types (correct, non-recognition, and incorrect). Four groups of depth-ERP components (N100, P200, N300, P300) were observed. The N100 was not found to be affected by the quality of recognition, manifest in type of response, while the later components were, but each in its own way. A comparison of these data with those of multiunit activity recorded from these same sites (see Bechtereva et al. 1990) shows that the pattern of the depth N100 and P200 components with reference to the 3 types of response have no observable counterparts in the impulse activity manifestations of subcortical neuronal populations, while the depth N300 and P300 are indeed associated with the neuronal impulse activity. This in turn supports the hypothesis concerning multiple (including subcortical) generators of the P300.

Adult↗

PubMed1990

In search of cerebral error detectors.

Multiunit activity was recorded from 124 different subcortical sites in 10 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 so chosen that in about half the trials the patient failed to recognize the digit correctly. Peristimulus time histograms (PSTHs) for each neuronal population as well as profiles of reactions for all neuronal populations were calculated and statistically analysed, separately for the cases of correct, incorrect, and non-recognition. There are at least 3 groups of neuronal populations, each associated with one temporally separate neurophysiological process involved in the performance of the psychological recognition task. They can be differentiated by the parameters' 'onset' and 'peak' latency. This in itself suggests that they may be related to different psychological processes involved in the task's performance, the earlier components in feature detection and/or evaluation operations concerning the stimulus; the later components, presumably, in processes related to initiation of the actual response. By scanning the individual PSTHs, we found one neuronal population which might be considered an error detector. This population reacted robustly in the early stages of information processing (100-500 ms post-stimulus) only in the case of non-optimal behavior, suggesting that it might somehow be related to signalling an error.

Adult↗

PubMed1989

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.

Adult↗

PubMed1986

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 potential's 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.

Adolescent↗

PubMedDate not supplied

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.

Adult↗

PubMedDate not supplied

Event-related neuronal responses in the human strio-pallido-thalamic system. II. Cognitive functions.

Multiunit activity was recorded from the strio-pallido-thalamic system in the same parkinsonian patients (as described in the previous paper) who bore gold electrodes for diagnosis and therapy. The patients voluntarily participated in various tasks designed to study neuronal correlates of cognitive functions: "odd-omissions," "short-term memory," "cued bimodal," "assessment," and "dual-stage delayed response" tasks. Preparatory-related activities were found in multiunits reacting to sensory cues. In a few multiunits these activities depended upon the specific features of the stimuli that were anticipated for evaluation. The most striking characteristic of stimulus-related activity was the suppression of the multiunit responses when the stimuli become behaviourally meaningless. The hypothesis of action programming is discussed: the loop, including the cortex, neostriatum, pallidum and appropriate parts of the thalamus, is involved in the selection of actions, thus providing the organization of sequential behaviour.

Adult↗