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T Radil

Publications and source records attributed to T Radil.

136 records · Page 8Linked to original sources
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Mismatch negativity (MMN) for sequences of auditory and visual stimuli: evidence for a mechanism specific to the auditory modality.

ERPs to sequences of standard and deviant sinusoidal 100 msec tone pips, high-contrast sinusoidal gratings and to their simultaneously presented combinations were recorded. Mismatch negativity (MMN), an ERP component elicited by deviant stimuli, was estimated for the different stimulus sequences in order to find out whether it reflects modality-specific processes or non-specific attentive phenomena. In addition to the auditory modality, we studied whether the mismatch response could be evoked by a deviant visual stimulus in a visual sequence or by a deviant stimulus in either modality. The results show that only auditory stimuli produced the mismatch response, suggesting that MMN is not a manifestation of a general attentional mechanism but is probably specific to the auditory modality.

Acoustic Stimulation↗
PubMedDate not supplied

The effect of AVP and DGAVP on the exploratory activity of rats.

The effects of [8-L-arginine] vasopressin (AVP) and desglycinamide [8-L-arginine] vasopressin (DGAVP) were tested on the exploratory activity of adult male rats in a novel environment. The inherited individual differences in the non-specific excitability level of the animals were ascertained prior to the drug administration and the rats were then distributed evenly into the experimental groups. One half of each groups contained the less excitable and the other the more excitable animals. The peptides or saline were injected every other day--altogether 4 times--in a dose of 5 micrograms/kg/ml subcutaneously, 40 min before starting the experiments. The exploratory activity in the novel environment was observed for 15 min. AVP and DGAVP, which differ in their peripheral endocrine activities, had opposite effects on the behavior in a novel environment: AVP, with its wide spectrum of peripheral effects, decreased the exploratory activity, whereas DGAVP, with minimal peripheral effects, increased the exploratory activity slightly. This basic response to the administration of peptides was influenced by the type of inherent non-specific excitability level. The depressive action of AVP was more pronounced in the more excitable rats, whereas DGAVP significantly stimulated the less excitable animals. It is concluded that the inhibitory effect of AVP is mainly due to its peripheral endocrine, especially hemodynamic, effects, whereas DGAVP is supposed to increase arousal, which is responsible for differences in the animals' performance with regard to their inherited non-specific excitability levels.

Animals↗
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On population aspects of group disasters: an evolutionary view.

Simple mathematical models were constructed (using a DEC PDP 11/40 computer) to evaluate the probable significance of differences between individuals in adaptive reserve--survival time (modelled as "failure rate")--for group survival and of basic population parameters (fertility and mortality) for the gradual compensation of group size/age distribution of a population after an acute group disaster. The results indicate that reversion to prehuman biological regulative mechanisms probably occurs, and that after short-lasting group disasters the time-course for compensation (normalization) of population size and age distribution (when probable values of fertility and mortality were considered) is prolonged.

Concentration Camps↗
PubMedDate not supplied

Pre-attentive discriminability of sound order as a function of tone duration and interstimulus interval: a mismatch negativity study.

The present study addressed the pre-attentive processing of sound order. Event-related potentials were recorded from reading subjects while they were presented with pairs of two tones differing from each other in frequency (1000 vs. 1500 Hz). The within-pair (silent) interstimulus interval (ISI) was, in separate blocks, varied between 0 and 245 ms to determine the minimum separation in time needed for detecting the reversed order of the two frequencies. In standard tone pairs (p = 0.9), the frequencies were in an ascending order, whereas in the deviant pairs (p = 0.1), their order was reversed. Tone durations of 5 and 20 ms were employed in separate experiments. With the 20-ms stimulus duration, the change-specific mismatch negativity (MMN) component was elicited with all within-pair ISIs employed (0, 10, 30, 90 ms). With the 5-ms stimulus duration, however, MMN was elicited only with the 245-ms ISI but not with 95-ms or shorter ISIs. These results show that increased stimulus duration considerably improves perceiving the order of two tones at the pre-attentive level. They also indicate that the accuracy of the processing of temporal information can be probed with MMN. This finding, together with the fact that MMN elicitation does not require the subject's voluntary attention, suggests that MMN might be used in the assessment of temporal processing deficits in clinical disorders in which patients are not motivated or able to give their verbal or motor response.

Acoustic Stimulation↗
PubMedDate not supplied

Apomorphine does not influence olfactory thresholds in Parkinson's disease.

In order to verify the presumed dopaminergic basis of olfactory dysfunction in Parkinson's disease (PD), we studied olfactory functions in 12 PD patients (mean age 60.1 yrs, mean duration of PD 9.0 yrs, mean Hoehn and Yahr score 2.8) before and after apomorphine (APO) administration. Amylacetate (banana smell) in 12 sequential dilutions (in 50% steps) was used for the examination of olfactory thresholds. The testing showed no significant differences in any olfactory parameters before and after APO. Furthermore, when analysing the subgroup of 7 hyposmic PD patients, we also found no significant differences before and after APO. We therefore believe that olfactory dysfunction in PD is not dependent on dopamine deficiency.

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