Biomedical subjects

Osvaldas Ruksenas

Publications and source records attributed to Osvaldas Ruksenas.

6 recordsLinked to original sources

PubMed2006

Identification of partially presented meaningless patterns: effect of completeness and distinctiveness.

The role of parts versus that of wholes in a visual perception has been debated for a century as two opposite approaches, namely, an analytic and holistic. In two psychophysical experiments we investigated whether the stimulus completeness or distinctiveness is essential for identification of the partially presented patterns under brief presentation conditions. For this purpose, a special class of stimuli was constructed in such a way that the patterns could be divided into informative and redundant parts. The first experiment clearly demonstrated the importance of the redundant part for effective pattern identification for the majority of subjects. The second experiment revealed the direct dependence of identification accuracy of the patterns on their completeness (2, 3, 4, 5, or 6 elements). Familiarisation of subjects with the test stimuli influenced the strength of this dependence.

Adult↗

PubMed2006

Effects of risperidone on auditory information processing in neuroleptic-naive patients with schizophrenia spectrum disorders.

Early effects of risperidone (2.5 +/- 1 mg/day) on auditory information processing were investigated in 9 neuroleptic naive patients with schizophrenia spectrum disorders and 9 healthy controls by using event-related potentials (ERPs). ERPs were elicited during active auditory "oddball" paradigm and were recorded before and after two weeks of treatment. Baseline P3 latencies were significantly delayed in patient group. Risperidone treatment did not change P3 amplitudes and latencies. However, P2 amplitudes were reduced in parallel with the clinical improvement measured by Positive and Negative Syndrome Scale (PANSS). Although risperidone did not change neural bases of active attention after two weeks of treatment, the reduction of P2 amplitude suggests that risperidone may affect auditory information processing in patients with schizophrenia spectrum disorders who never have been exposed to antipsychotic treatment.

Adolescent↗

PubMed2006

Transcranial magnetic stimulation: the method and application.

Transcranial magnetic stimulation is a noninvasive method for stimulation of brain that is based on the ability of magnetic field to penetrate skull and brain meninges, subsequently inducing electric current in the brain tissues that produces neuronal depolarization and generation of action potentials. Moreover, transcranial magnetic stimulation has effects on neurochemical and synaptic processes in neurons. Due to its easy use and relatively fair side effects, nowadays, transcranial magnetic stimulation is widely used in neurosciences and medicine. The main areas of transcranial magnetic stimulation application are: 1) the investigation of cortical and spinal excitability, 2) the investigation of neuronal plasticity, 3) the investigation of neuronal connectivity, 4) functional mapping, and 5) the treatment of some neurological and psychiatric disorders. Transcranial magnetic stimulation alone or in combination with other noninvasive neuroimaging (PET--positron emission topography, MRI--magnetic resonance imaging) and neurofunctional (EEG--electroencephalography, ERP--event-related potentials, fMRI--functional magnetic resonance imaging) methods allows conducting research on brain functions. Thus, transcranial magnetic stimulation is suitable as a diagnostic tool in neurologic and neuropsychiatric brain research.

Action Potentials↗

PubMed2005

Effects of olanzapine on auditory P300 and mismatch negativity (MMN) in schizophrenia spectrum disorders.

We investigated effects of olanzapine (5-10 mg/day) on passive and active attention in 11 patients with schizophrenia spectrum disorders and 15 healthy controls by using auditory evoked potentials (AEPs) mismatch negativity (MMN) and P300. AEPs were elicited during active and passive auditory "oddball" paradigms before, after 2 weeks and 4 weeks of olanzapine treatment. Baseline P300 amplitudes, but not MMN, were significantly reduced in patients compared with controls. Although clinical signs improved significantly measured by Positive and Negative Syndrome Scale (PANSS), olanzapine had no significant effects on latencies and amplitudes of MMN and P300. Thus, olanzapine does not have effects on active and passive attention in patients with schizophrenia spectrum disorders. Four weeks olanzapine treatment may be insufficient for the improvement of cognitive dysfunction in terms of inability to focus on relevant stimuli in these patients.

Adolescent↗

PubMed2005

Does electroconvulsive therapy (ECT) affect cognitive components of auditory evoked P300?

Electroconvulsive therapy (ECT), as a treatment tool for psychiatric disorders, is believed to be safe and effective. Nevertheless, it has a negative impact on cognitive functioning, especially on memory, causing both retrograde and anterograde amnesia. However, ECT effects on more subtle stages of information processing are not studied enough. Event-related potentials, and especially P300, are thought to reflect physiology of cognition. Thus, we aimed to evaluate the effects of ECT treatment on parameters of endogenous components (N2, P3) of the P300 potential. Seventeen patients suffering from schizophrenia, schizoaffective disorder and recurrent depressive disorder participated at the study. After the course of ECT, significant increase of N2 amplitude in parietal midline region and prolongation of P3 latency in frontal midline region, of which the magnitude positively correlated with the number of ECT procedures, have been obtained.

Adult↗

PubMed2003

Evaluation of new MMN parameters in schizophrenia.

ERPs could be helpful in the objectification of many psychological measures. In the last few decades one of the most commonly used ERPs has been the mismatch negativity (MMN) potential. It may be used to detect cognitive dysfunction in patients suffering from schizophrenia, dementia, depression, and can also be successfully applied in treatment monitoring. Nevertheless, changes of MMN parameters (prolongation of latency or reduction of amplitude) are not sufficiently specific to help to diagnose particular diseases. In this study we looked for more strict and specific MMN characteristics selective for schizophrenia. Fifteen healthy human subjects and twelve suffering from schizophrenia spectrum disorders were studied. Two new parameters were considered: the speed of ascending part of MMN slope (SAS) and the half area of the MMN wave. These two measures could differentiate the early stages of cognitive processing disturbances in schizophrenia spectrum disorders.

Adolescent↗