Biomedical subjects

M G Van Erp

Publications and source records attributed to M G Van Erp.

4 recordsLinked to original sources

PubMed1998

Impaired early visual processing in disorganised schizophrenia.

Topographic differences in flash/pattern shift VEP data are evaluated in paranoid (n: 38), disorganized (n: 23) and residual (n: 23) schizophrenic subtypes and compared to normal controls. Increased early P1 and a restricted diffusion of the late P2 responses suggest dopaminergic over- and cholinergic underactivity in paranoid and residual schizophrenia. A distinctive pattern N145 reflects well-preserved attentional resources in the paranoid subtype. Latency increase and amplitude decrease of the pattern N145 concur with abnormal antisaccades documented in disorganized behaviour. VEP-data might help differentiate between schizophrenic subtypes.

Adult↗

PubMed1997

Auditory information processing in schizophrenia.

Early N1P2 and late N2P3 responses generated in an auditory oddball paradigm are topographically compared in three psychiatric patient groups. In schizophrenia N1 and N2 amplitude is comparable with dementia and significantly decreased with respect to affective disorder. In contrast, P3 amplitude does not allow discriminating schizophrenia from affective disorder but is significantly diminished in dementia. The late N2P3 response shows a topographic effect along the fronto-occipital axis. Schizophrenia is characterized by an iCNV and N2 maximum over the frontal planes and a compound P3 lacking distinct frontal and parietal components. The findings are discussed in reference to literature data and current hypotheses/theories concerning information processing. Our findings favour an important dysfunction of automatic processing including early selection in schizophrenia.

Adult↗

PubMed1997

Facilitation of early and masking of late cortical responses in dementia.

Topographic differences in longlatency SSEP and flash VEP data are compared in 3 different psychiatric patient groups. Differences between schizophrenia and affective disorder are restricted to somatosensory P100 amplitude gradients along the antero-posterior axis. In contrast EP-differences between psychiatric patients and dementia are prominent, encompassing both late and early (< 100 ms) responses. Our flash P 2 and somatosensory P 3 data are in accordance with previous findings. Multi-modal positive responses with a latency of 40-80 ms are significantly increased in dementia. This facilitation suggests cortical dysfunction and/or subcortical gating impairment.

Adult↗

PubMed1990

Voltage-dependent action of valproate on potassium channels in frog node of Ranvier.

The influence of the anti-epileptic drug, valproate, on K conductance (gK) was investigated in voltage-clamped Ranvier nodes of Xenopus laevis. A double pulse method was used in order to eliminate the effect of accumulation of potassium ions in the perinodal space, thus enabling the determination of the 'true' magnitude of gK. Valproate (2.4 mM) had a voltage-dependent action on the magnitude of gK. With small step depolarizations more negative than about -50 mV, valproate increased gK (20 ms after the step) to approximately 12% of the maximal gK, an increase which disappeared due to a relatively rapid (less than 200 ms) inactivation process. However, with step depolarizations more positive than about -50 mV, valproate markedly reduced gK (20 ms after the step) at greater depolarizations, with a maximum of about 40% of the maximal gK. Moreover, at these voltages gK was inactivated completely (less than or equal to 10 s), whereas under control conditions the inactivation was only partial. Both the temporary increase and the steady state decrease of gK could contribute to an anti-epileptic effect by increasing the action potential threshold and by preventing excessive depolarizations of the nerve during epileptic seizures, respectively.

Animals↗