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V Csépe

Publications and source records attributed to V Csépe.

At least 19 recordsLinked to original sources
PubMed2001

Impaired speech perception in aphasic patients: event-related potential and neuropsychological assessment.

The mismatch negativity component (MMN) of auditory event-related potentials (ERP) was recorded in four aphasic patients and in age, gender and education matched controls. The MMN changes elicited by tone, vowel, voicing stop consonant and place-of articulation contrasts were recorded over both hemispheres. The results of MMN amplitude, latency and distribution differences between aphasics and controls were analyzed in detail. An extensive neuropsychological investigation was performed in order to highlight the assumed dissociation and possible interactions between the impaired acoustic/phonetic perception and deficient comprehension in aphasic patients. Our principal finding was that MMN elicited by pitch deviations is not enough sensitive to distinguish between patients and age-matched controls. The MMN elicited by consonant contrasts was found to be the most vulnerable in aphasic patients investigated. The MMN elicited by voicing ([ba:] vs. [pa:]) and place-of-articulation ([ba:] vs. [ga:]) could be characterized by total lack, distorted or very limited distribution and correlated with the patients' performance shown in the behavioral phoneme discrimination task. The magnitude of the deficient phoneme (vowel and consonant contrasts) processing shown by MMN anomalies was proportionally related to the non-word discrimination and did not interact with the word discrimination performance. The impact of deficient speech sound processing on higher level processes may depend on the type of aphasia, while the presence of perceptual deficits in processing acoustic/phonetic contrasts seems to be independent of the type of aphasia.

Adult↗
PubMed1999

Auditory evoked potentials reflect serotonergic neuronal activity--a study in behaving cats administered drugs acting on 5-HT1A autoreceptors in the dorsal raphe nucleus.

A valid indicator of central serotonergic neurotransmission would be useful for various diagnostic and psychopharmacological purposes in psychiatry. However, known peripheral serotonergic measures only partially reflect serotonergic function in the brain. Previous findings suggest that the intensity dependence of auditory evoked potentials (AEPs) is closely related to central serotonergic activity. The present study examines the effects of microinjection of a 5-HT1A agonist (8-OH-DPAT) and a 5-HT1A antagonist (spiperone) into the dorsal raphe nucleus (DRN) on AEP recorded epidurally from the primary and secondary auditory cortex in behaving cats. We found a stronger intensity dependence only of AEP from the primary auditory cortex after 8-OH-DPAT, which inhibits the firing rate of serotonergic DRN neurons, and a weaker intensity dependence after spiperone, which increases serotonergic cell firing, as compared to baseline measurements. These results demonstrate that the intensity dependence of AEP is inversely related to serotonergic neuronal activity and that it may be a promising tool for assessing central serotonergic function in humans (e.g., identifying patients with low serotonergic neurotransmission).

8-Hydroxy-2-(di-n-propylamino)tetralin↗
PubMed1999

Pre-attentive detection of vowel contrasts utilizes both phonetic and auditory memory representations.

Event-related brain potentials (ERP) were recorded to infrequent changes of a synthesized vowel (standard) to another vowel (deviant) in speakers of Hungarian and Finnish language, which are remotely related to each other with rather similar vowel systems. Both language groups were presented with identical stimuli. One standard-deviant pair represented an across-vowel category contrast in Hungarian, but a within-category contrast in Finnish, with the other pair having the reversed role in the two languages. Both within- and across-category contrasts elicited the mismatch negativity (MMN) ERP component in the native speakers of either language. The MMN amplitude was larger in across- than within-category contrasts in both language groups. These results suggest that the pre-attentive change-detection process generating the MMN utilized both auditory (sensory) and phonetic (categorical) representations of the test vowels.

Acoustic Stimulation↗
PubMed1999

Brain responses reveal the learning of foreign language phonemes.

Learning to speak a new language requires the formation of recognition patterns for the speech sounds specific to the newly acquired language. The present study demonstrates the dynamic nature of cortical memory representations for phonemes in adults by using the mismatch negativity (MMN) event-related potential. We studied Hungarian and Finnish subjects, dividing the Hungarians into a naive (no knowledge of Finnish) and a fluent (in Finnish) group. We found that the MMN for a contrast between two Finnish phonemes was elicited in the fluent Hungarians but not in the naive Hungarians. This result indicates that the fluent Hungarians developed cortical memory representations for the Finnish phoneme system that enabled them to preattentively categorize phonemes specific to this language.

Adult↗
PubMed1997

Auditory-evoked potentials as indicator of brain serotonergic activity--first evidence in behaving cats.

Due to the increasing importance of the central serotonergic neurotransmission for pathogenetic concepts and as a target of pharmacotherapeutic interventions in psychiatry, reliable indicators of this system are needed. Several findings from basic and clinical research suggest that the stimulus intensity dependence of auditory evoked potentials (AEP) may be such an indicator of behaviorally relevant aspects of serotonergic activity (Hegerl and Juckel 1993, Biol Psychiatry 33:173-187). In order to study this relationship more directly, epidural recordings over the primary and secondary auditory cortex were conducted in chronically implanted cats under intravenous (i.v.) administration of drugs influencing the serotonergic and other modulatory systems (8-OH-DPAT, m-CPP, ketanserin, DOI, apomorphine, atropine, clonidine). The intensity dependence of the cat AEP component with the highest functional similarity to this of the N1/P2-component in humans was significantly changed by influencing 5-HT1a and 5-HT2 receptors, but not 5-HT1c receptors. This serotonergic modulation of the intensity dependence was only found for the primary auditory cortex which corresponds to the known different innervation of the primary and secondary auditory cortex by serotonergic fibers. Our study supports the idea that the intensity dependence of AEP could be a valuable indicator of brain serotonergic activity; however, this indicator seems to be of relative specificity because at least cholinergic effects on the intensity dependence were also observed.

Animals↗
PubMed1997

Mismatch field to tone pairs: neuromagnetic evidence for temporal integration at the sensory level.

The mismatch field (MMF) to minor pitch changes in two experimental conditions was studied. Standard tones of 1000 Hz and deviant tones of 1050 Hz both of 50 ms duration were delivered in single tone condition. Paired tones of the same duration were used in the paired tone condition. The standard tone pair consisted of two 1000 Hz tones, whereas the deviant tone pair was composed of a 1000 Hz tone in the first position and a 1050 Hz tone in the second position with a silent interval of 15 ms between the two. Standards of 90% and deviants of 10% probability were presented in random order and with a randomized interstimulus interval between 600 and 900 ms. The source analysis showed a more lateral location for the MMF obtained in the paired tone condition (MMF.P) compared to the MMF elicited by the single deviants (MMF.S). The source location of both the MMF.P and MMF.S turned out to be significantly anterior relative to the sources of the M100. The increased stimulus repetition in the paired tone condition (two times more stimuli than in the single tone condition) lead to a strong suppression of the field amplitude and of the dipole moment of the M100, while this effect could not be seen for the MMF. The data demonstrate a fundamental difference between the processes reflected by the M100 and the MMF: while the M100 represents the processing of every individual tone, the MMF reflects the change detection of the paired stimuli as unitary events, forming a perceptual group. The different sources of the MMF.P and MMF.S also support an integrated processing of the paired stimuli.

Acoustic Stimulation↗
PubMed1996

Intensity dependence of auditory evoked potentials in behaving cats.

The intensity dependence of auditory evoked potentials (AEPs) recorded epidurally over the primary (AI) and secondary (AII) areas of the auditory cortex was studied in behaving cats during wakefulness, sleep and anesthesia. Four kHz tones of 50, 60, 70, and 80 dB SPL, presented in random order every 2 +/- 0.2 s by a bone conductor, elicited clear changes of the AEP amplitudes with increasing stimulus intensity, but individual components displayed different response curves. AEP components from the AI region showed saturation of their amplitude with stimulus intensity (P13, P34) or no amplitude increase (N19), while amplitude and intensity were linearly related in the AII area. The intensity dependence of the first positive component (P12/P13) was consistently stronger for the AEP recorded from the AI than from the AII area, while later components exhibited no difference between AI and AII. During slow wave sleep, the intensity dependence of this first positive component increased in the two areas, while that of later components decreased. Pentobarbital anesthesia abolished almost all later components and depressed the intensity dependence of the first positive component both in the AI and AII area. These results indicate that (I) clear intensity dependence of AEP exists in the cat auditory cortex and (2) this intensity dependence, especially that of the first positive AEP component, shares functional similarities to the human augmenting/reducing phenomenon in the auditory modality concerning regional differences and sleep-waking cycle.

Acoustic Stimulation↗
PubMed1995

Correlation dimension changes accompanying the occurrence of the mismatch negativity and the P3 event-related potential component.

The aim of this study was to apply recently developed mathematical tools of chaos theory to the analysis of event-related potentials (ERPs) recorded in paradigms in which the mismatch negativity (MMN) and the P3 component appeared. A new method, the point correlation dimension (PD2i), was used for data analysis, which is more accurate than other algorithms for the calculation of the correlation dimension (D2), which latter is a measure of the complexity of the generator(s) responsible for producing the analyzed time series, i.e., the EEG. ERPs were recorded from Fz, Cz and Pz in 6 subjects. With respect to baseline, the PD2i decreased significantly both during the event-related potentials in which the MMN and also in which the P3 was present, but the pattern and magnitude of this decrease was different between these two situations. The pattern of PD2i changes during the occurrence of deviant stimuli eliciting the MMN suggests the presence of a frontal MMN generator. The conspicuous PD2i decrease during the occurrence of the P3 wave may support the "context closure" hypothesis concerning its functional significance.

Acoustic Stimulation↗
PubMed1995

On the origin and development of the mismatch negativity.

This review summarizes a number of findings related to the generation, development, and diagnostic value of mismatch negativity (MMN). The animal analogue of MMN to frequency contrast can be observed in the primary and secondary auditory cortical and also in the association cortical recordings. It is shown that subcortical sensory specific and archicortical structures may also contribute to the processes involved. The results are more complex than would be predicted by the notion that only the primary system plays an active role in the comparison processes reflected by the MMN that and the nonprimary pathway acts only as a modulating influence. The fundamental nature of the brain functions reflected by MMN is suggested by the demonstration of MMN in sleep and anesthesia, though in limited conditions. The postnatal development of automatic stimulus comparison, as indexed by MMN, presents an isochronicity, contrary to other evoked potential components whose development is not complete until puberty. Thus, the MMN provides a stable measure for electrophysiological assessment of auditory perception. This possible diagnostic value of the MMN is shown in studies of aphasics which emphasize the nature of perceptual deficits in the processing various speech and nonspeech stimuli.

Anesthesia↗
PubMed1990

Steady-state responses from the cat auditory cortex.

Responses to 350 ms trains of clicks with 10-100 Hz repetition rate were recorded from the auditory cortices of six cats. Click trains of 30-50 and 90-100 Hz elicited a clear steady-state response (SSR) in awake state. SSRs were small or absent below 30 Hz and in 60-70 Hz stimulus range. In slow wave sleep the optimal rate to elicit SSR shifted towards lower frequencies. 90 Hz SSR was largest in paradoxical sleep. SSRs were strongly suppressed by barbiturate anesthesia. The amplitude of the SSR from the medial geniculate body (MGB) in two cats gradually decreased from 20 to 100 Hz and was more resilient to barbiturate anesthesia than the cortical SSRs. Only low amplitude or no SSRs could be recorded from vertex, visual and association cortices and from the hippocampus in control recordings. The results suggest different generation mechanisms for SSRs recorded from cat auditory cortex and MGB. Human auditory SSRs resemble cat auditory cortical SSRs more than those recorded from cat MGB. The results imply that auditory SSRs in humans are generated in the cortex.

Acoustic Stimulation↗
PubMed1988

Intracortical auditory evoked potentials during classical aversive conditioning in cats.

Auditory evoked potentials (EPs) were recorded simultaneously from six different depths of the auditory cortex of freely moving cats. In a classical aversive learning paradigm the change of the pitch of regularly given acoustic stimuli served as warning signal. With conditioning the amplitude of a middle latency negative component increased and its latency decreased. Based on laminar analysis of EP profiles we propose that the observed EP changes were generated within the upper cortical layers and reflected a temporary aurousal reaction induced by the signal as a result of discrimination learning. For the description of this effect the term "learned aversive arousal" is suggested.

Animals↗
PubMed1988

Effect of atropine on intracortical evoked potentials during classical aversive conditioning in cats.

In this article, intracortical evoked potentials (EPs) were recorded simultaneously from six different depths of the auditory cortex of freely moving cats. The effect of (a) different states of vigilance and that of atropine, (b) classical aversive conditioning, and (c) the effect of atropine during conditioning was studied on the intracortical EP profiles. Atropine induced EP changes that were similar to those seen in slow wave sleep. During classical aversive conditioning signal stimuli elicited a middle-latency negative EP component which was localized to the superficial cortical layers. Atropine (2 mg/kg body weight) did not abolish the appearance of this component but only increased its latency. It is proposed that the cholinergic part of the ascending activating system did not play an essential role in its generation.

Animals↗
PubMed1987

Evoked potential correlates of stimulus deviance during wakefulness and sleep in cat--animal model of mismatch negativity.

Auditory evoked potentials (EPs) elicited by standard (STs) and deviant tones (DTs) of different probabilities were studied in freely moving cats during wakefulness and sleep. A large double peaked negativity, so-called mismatch negativity (MMN), was evoked by the unattended low probability DTs. The EPs recorded from the AI and AII areas of the auditory cortex showed more dynamic changes than the vertex and association cortical responses. The amplitude of the MMN was inversely proportional to the probability of DTs. The latency of the MMN showed dependence both on the location of the recording site and on the probability of DTs. During slow wave sleep (SWS) the MMN of increased latency could be evoked only at the lowest probabilities. The cortical distribution of the MMN changed in the SWS.

Animals↗
PubMed1987

Effects of signal probability on sensory evoked potentials in cats.

The present experiment was designed to follow the evoked potential (EP) changes recorded from the association cortex and A II area of the auditory cortex and from the vertex of the freely moving cat. The EPs elicited by clicks of different probabilities used as warning stimuli during aversive conditioning were analyzed. It was found that the EPs recorded from the auditory cortex and the vertex showed different changes during the aversive conditioning to the rare clicks of 3 and 10% probabilities. The N50 and P100 components of the auditory cortical (A II area) EPs increased significantly at both signal probabilities. On the vetex and association cortical EPs, elicited by the rare signals, a broadly distributed positivity, the P250 wave could be detected. The amplitude increase of the P250 was inversely proportional to the used probability of the signal.

Acoustic Stimulation↗
PubMed1986

Laminar analysis of intracortical auditory evoked potentials during the wakefulness-sleep cycle in the cat.

Click-elicited evoked potentials (EPs) were recorded simultaneously in six different depths of the auditory cortex of freely moving cats during the wakefulness-sleep cycle. Chronically implanted multielectrodes designed especially for this purpose were used. The clicks were given through a bone conductor and middle ear muscles were cut to keep the acoustic input constant. The EPs recorded in different cortical depths changed in different ways during the wakefulness-sleep cycle as evidenced by both the early and middle latency components. The amplitude of the middle latency components was the largest in slow wave sleep (SWS) in all cortical depths. The early deep negative wave was the smallest in paradoxical sleep (PS) probably indicating a reduced sensory input. In the aroused state a negative component of approximately 60 ms appeared localized to the superficial layers. The lack of a true phase reversal of the early components, their independently changing amplitudes and the homogeneous polarity of the later waves in the different cortical depths do not support the idea of simple dipole processes that could explain their generation.

Animals↗
PubMed1986

Evoked potential components in the layers of the auditory cortex of the cat.

The intracortical distribution of evoked potentials was studied by seven-contact multielectrodes implanted into the primary auditory cortex of freely moving cats. The aim of the study was to compare the intracortical profiles of the responses evoked by click stimuli and by electrical stimulation of the medial geniculate body in different states of alertness and in Nembutal anesthesia. Only the early surface positive component showed phase reversal in the depth of the cortex. The middle latency components which were faithful indicators of vigilance appeared without phase reversal. Nembutal wiped out these components. A negative component of about 50 ms latency appeared in the attentive animal which had the highest amplitude close to the surface and decreased toward the depth indicating that it was generated in the most superficial layers of the cortex. The stimulation of the last nucleus of the specific auditory pathway elicited evoked potential patterns including also the middle latency components, which were closely similar to those induced by click stimuli.

Animals↗
PubMed1986

Comparison of evoked potential changes during classical and instrumental conditioning in cats.

The waveform changes of cortical evoked potentials to click conditioned stimuli were analyzed by a complex computer program developed for sorting nonhomogeneous series of evoked potentials. The changes of evoked responses manifested themselves mainly in the middlelatency waves, while the first components showed only a slight fluctuation during the whole conditioning. A late negative component of 40-50 ms latency was clearly related to the attentive state of the animal. The evoked potentials with increased negative component appeared in different sequences in 'the two conditioning paradigms and in the different phases of the learning process.

Animals↗