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Latent EEG characteristics of the brain development via photic driving reaction in normal children and neurologic patients
156
Symposium abstracts / International Journal of Psychophysiology 69 (2008) 139–205
Interaction between central and peripheral levels of writing process organization in primary school children M.M. Bezrukikh Russian Academy of Education, Institute of Developmental Physiology, Moscow, Russia The question of central regulation of writing and correlation between central and peripheral levels of movement regulation during writing is still unresolved. There are different approaches to this process; however, the concept of hierarchical organization of the system regulating the movements in question suggested by N.A. Bernstein, which presupposes interaction between brain structures at different levels, is beyond question. Electrical activity (EA) of brain zones involved in movement organization (EEG) and working muscles (EMG) was analyzed to assess interaction between central and peripheral levels of voluntary movement regulation during writing. Coherence analysis of biopotentials of different cortical zones and working muscles (surface flexor and common extensor of the fingers) was performed in 6–7 and 9–10-year old-children. The phenomenon of EEG and EMG synchronization was detected at rest and during preparation for writing, which is believed to reflect interaction between cortical and peripheral levels and provide postural components. It should be noted, that interrelation between brain and muscle biopotentials and its restructuring at different stages of preparation for movements differs significantly in children depending on age and stage of skill acquisition. However, in both age groups correlation between biopotentials of the cortex (irrespective of zone and hemisphere) and agonist muscles is higher than between those of the cortex and antagonist muscles. Another peculiarity to be noted is that an increased number of children with correlation between biopotentials of the frontal cortex and muscles detected in the group with higher level of skill acquisition. At the age of 6–7 more than 70% of the children studied show “connection” between biopotentials of muscles and occipital and central cortical zones, while only 23% show peaks of EA coherence between frontal zone and muscles. At the age of 9–10 the process of joint functional “tuning” during preparation for movement involves frontal cortical zones. Distinct peaks of EA coherence between cortex and muscles predominantly in the alpha-range are noted in 81% of children. As the child develops interlevel interaction restructuring is minimized and interaction between frontal and central cortical zones and muscles is increased during preparation for writing. During writing both at 6–7 and 9–10 years interlevel interaction undergoes restructuring — coherence of electrical activity of brain and both muscles (agonist and antagonist) is decreased significantly in θ, α and β-ranges. However, interaction between brain cortex and muscles is lower in children than in adults, which appears to be related to immaturity of the central mechanisms of graphical movements.
doi:10.1016/j.ijpsycho.2008.05.393 Human brain maturation and ability to recognize and express emotions: A study of preschool aged children A.A. Mekler a, E.V. Vishnevetskaya b Institute of Human Brain Russian Academy of Sciences, Laboratory of Positron-Emission Tomography, Saint Petersburg, Russia b Southern Ural State University, Department of Psychology, Cheliabinsk, Russia
a
Developing child's brain becomes more and more complex with aging. This can be shown by the methods of deterministic chaos theory and fractal analysis, such as estimating of correlation dimension of reconstructed attractor (D2) of EEG or fractal dimension of EEG curve. There are investigations where it is shown, that age increases correlation dimension. Also increasing of EEG's complexity appears as increasing of its fractal dimension. So, we can consider EEG's complexity as a brain maturation index. Therefore we can study the relationship between the brain maturation and different psychic functions. In present work we attempted to find out relationship between brain maturation and emotional competence (ability to recognize and express emotions) in the group of preschoolers — 4–6 years old children, 92 persons. We estimated EEG's complexity, calculating its D2 value. Electroencephalograms were recorded using 19 scalp electrodes according to international system “10–20” and shorted ears electrodes as a reference.
Sampling rate was 250 s− 1, band range — 0.16–70 Hz. During EEG recording subjects were in the state of relaxed wakefulness with opened eyes. We have used for analysis artifact free cuts of EEG recordings, which durability was 16 s (4000 samples). Calculations were performed with unit lag and Theiler's window, which size was estimated by means of space-time separation plot (Mekler A.A., 2007). D2 was calculated for every EEG channel. Emotional competence was evaluated according to special procedure including tests on mimic and pantomimic recognition and expression, graphic expression and vocal recognition and expression of emotions (Vishnevetskaya E.V., Shakurova Z.A., 2006). Due to nonnormal statistical data distribution we used index of cograduation to find out relationship between EEG's complexity and children's emotional competence. It was found that there is direct relation between ability to recognize emotions and D2 in T3 and C3 leads. Ability to express emotions directly relates with D2 in Fz, C3, P3 and O1 leads. Then we have split group under study into three subgroups: 4, 5 and 6 years old. In the subgroups of 4 and 6 years old children there was no relationship between emotional competence and D2. But in the subgroup of 5 years old children it was in the leads Fp1, T3, T5 and P3 — for emotion recognition only. This indicates that in the age of 5 there is reorganization in the brain structures, which provide the ability to recognize and express emotions.
doi:10.1016/j.ijpsycho.2008.05.394 Prenatal hypoxia affects amyloid metabolism and formation of cognitive functions in postnatal ontogenesis of rats I.A. Zhuravin a, N.M. Dubrovskaya a, N.N. Nalivaeva b, A.J. Turner b I.M. Sechenov Institute of Evolutionary Physiology and Biochemistry, RAS, St Petersburg, Russia b University of Leeds, Leeds, United Kingdom
a
Rats subjected to hypoxia (3 h, 7% O2) on 13–14th days of embryogenesis (E13–E14) demonstrated, compared to controls, a delay in physiological development and impaired learning and memory correlated with the changes in the activity of the cholinergic system and the system of biogenesis of cyclic nucleotides as well as with neurodegenerative processes (an increased number of pathologically changed neurons and glial cells, a decreased population of neurons) in the cortex, basal ganglia and hippocampus. In these animals we have found changes in metabolism of amyloid precursor protein (APP) in the cortex and striatum and decreased content of its soluble form produced via restricted proteolysis of APP by a specific metalloprotease, alpha-secretase. The latter represents the non-amyloidogenic pathway of APP cleavage. These changes could underlie memory impairment during later life and were in agreement with memory impairment observed after i.c. injections of an inhibitor of alpha-secretase, batimastat. Moreover, both in the cortex and striatum of animals subjected to prenatal hypoxia there was a decreased expression of some enzymes participating in degradation of the toxic amyloid peptide, formed from APP via its amyloidogenic processing. The principal new data on the role of amyloid-degrading enzymes (ADE) in functioning of the neuronal cells and the brain have been obtained. It was found that expression of ADE increases during the first month of animal postnatal life but then decreases with age. Hypoxia on E13.5 and acute hypoxia in adult rats resulted in a decrease of ADE in all brain structures analysed. Our data testify that prenatal hypoxia, specifically in the period of formation of the neuronal crest, leads to structural changes in the nervous tissue and in APP metabolism which manifest themselves during the lifespan of animals. In humans the risk of development of neurodegeneration and cognitive disorders might increase with age. Supported by grants of RAS “Fundamental Sciences to Medicine” and Saint Petersburg Scientific Center, RBRF (06-04-48414).
doi:10.1016/j.ijpsycho.2008.05.395 Latent EEG characteristics of the brain development via photic driving reaction in normal children and neurologic patients V.V. Lazarev, M.A. Genofre, A. Pontes, L.C. De Azevedo Oswaldo Cruz Foundation, Fernandes Figueira Institute, Rio de Janeiro, Brazil
Symposium abstracts / International Journal of Psychophysiology 69 (2008) 139–205
The EEG driving response to the intermittent photic stimulation (IPS) can enhance the manifestation of latent oscillators not present in the spontaneous EEG. This can provide additional neurophysiological information regarding normal brain development and its pathological alterations. In the present work, this reaction to 11 fixed IPS frequencies (3–24 Hz) were studied in 57 normal children and adolescents and 95 neurologic patients, aged 5–18 years. The topographic characteristics of photic driving proved to be particularly sensitive to the brain maturation. The occurrence of the driving peaks in the spectra of the 12 non-visual areas increased with the age. EEG coherence among these leads at the IPS frequencies and at their harmonics also positively correlated with the age. This means that the brain maturation is normally accompanied by gradual increase in the photic driving reactivity in the anterior cortical areas. In the occipital visual areas, children and adolescents, in contrast to adults, showed similar strong driving responses to the theta IPS frequencies. On the other hand, spontaneous EEG spectra of adolescents were similar to those of adults and differed from those of children by the absence of any peak in the theta band. In this way, the driving reactivity revealed one additional stage of “latent theta oscillators” in the development of the brain electrical activity not apparent in the resting state. In general, the driving amplitude in the delta and theta bands correlated with the age negatively. In 57 patients with partial epilepsy, the number of driving peaks in the spectra of non visual areas was reduced showing a likely delay in brain maturation as well as the effect of the antiepileptic drugs. This interpretation was based on lower driving characteristics in 24 naïve patients in comparison with normal subjects and on the expressed reductions in the driving peaks number and in coherence at the IPS frequencies in 10 naïve patients after a course of treatment with Carbamazepine. Fourteen autistic boys free of drug treatment, with relatively intact verbal and intellectual functions, showed reduced right-side driving reactivity and lower intrahemispheric driving coherence predominantly at the alpha and beta frequencies, probably due to some deficit in right hemisphere activation.
doi:10.1016/j.ijpsycho.2008.05.396 SYMPOSIUM 12: Psychophysiological and Clinical Aspects of Drug-EEG-ERP Interactions Chair: Márk Molnár (Hungary) Effects of the hallucinogenic 5-HT2A agonist psilocybin on object completion in humans F.X. Vollenweider, D. Hell, M. Kometer University of Zurich, University Hospital of Psychiatry, Zurich, Switzerland Background: The preferential serotonin-2A agonist psilocybin is known for its ability to produce a model psychosis including visual hallucinations that mimics some of the signs and symptoms of insipient schizophrenia. Recent studies of visual processing in schizophrenia have indicated disturbances in object completion (Gestalt perception) associated with alterations in the N170 component. Methods: To further elucidate the role of 5-HT2A receptors in illusionary contour processing the effect of psilocybin (115 µg/ and 215 µg/kg vs placebo) on object completion has been assessed using Kanizsa figures and EEG/ERP technique in normal volunteers (n = 16). Kanizsa triangles are stimuli that have been shown to cause significantly increased N170 amplitude responses relative to control stimuli due to the presence of illusory contours and the induced gestalt perception of form. Results: We found that psilocybin dose-dependently impaired object completion associated with a preferential reduction of the N170 amplitude to the Kanizsa relative to Non-Kanizsa stimuli in occipital cortex (V1/V2 and/or LOC). This finding was supported by an additional behavioural visual detection task wherein Kanizsa triangles and real triangles were embedded within fields of distracters. Moreover, the overall reduction of the N170 amplitude in the Kanizsa and the non-Kanizsa condition correlated with the degree of psilocybin-induced visual hallucinations. Conclusion: Given that similar findings were found in schizophrenic patients the present results suggest that a disruption of the serotonergic neurotransmission, particularly at the level the 5-HT2A receptor, may underlay the aberrant object completion found in schizophrenia.
doi:10.1016/j.ijpsycho.2008.05.397
157
Auditory evoked potentials as indicator of brain serotonin system and as predictor of pharmacotherapeutic response in psychiatric patients I. Uhl, G. Juckel Ruhr University, Department of Psychiatry, Bochum, Germany Predictors of treatment response to serotonergic versus non-serotonergic, e.g. noradrenergic, antidepressants are of considerable clinical relevance. Such a prediction of treatment response could help to reduce the number of patients receiving weeks or even months of unsuccessful treatment. Several studies imply that the effectiveness of selective serotonin reuptake inhibitors (SSRI) can be predicted successfully by using the loudness dependence of auditory evoked potentials (LDAEP), which denotes change in the amplitudes in response to different stimulus intensities. Up to now, LDAEP is one of the best validated indicators of the central serotonergic system. The aim of the present study was to investigate whether or not LDAEP also allows the differential prediction of treatment response to serotonergic versus noradrenergic antidepressants. A randomized prospective study was conducted on thirty-five unmedicated in-patients with a DSM-IV diagnosis of major depression (42.5 ± 10.8 years old; 13 male, 22 female, 28.9 ± 5.7 on Hamilton Depression Rating Scale (HDRS)). Before the treatment started, electrophysiological recordings were performed. After that, the patients were treated either with the SSRI citalopram or with the noradrenaline reuptake inhibitor (NARI) reboxetine for four weeks. ANOVA revealed that responders to the citalopram treatment (50% improvement on HDRS) were characterized by a strong LDAEP at baseline, and responders to reboxetine by a weak LDAEP. Non-responders to citalopram or reboxetine showed inverse LDAEP characteristics, respectively. This finding demonstrates differential prediction of response to different classes of antidepressants. Patients with an initially strong LDAEP rather seem to respond to a serotonin-agonistic antidepressant; patients with a weak LDAEP will more likely benefit from a non-serotonergic, e.g. noradrenergic, antidepressant. If these results were replicated in a larger sample, the simple method of evaluating the LDAEP before the start of an antidepressive treatment could be introduced broadly. LDAEP measurement could replace the current trial and error principle of antidepressant treatment and thus support physicians in their clinical work.
doi:10.1016/j.ijpsycho.2008.05.398 Effect of valproate and lamotrigine in patients with idiopathic generalized epilepsy revealed by LORETA analysis I. Kondakor a, P. Piros b, M. Bessenyei c, K. Hollody d, M. Toth e, B. Clemens b County Teaching Hospital, Department of Neurology, Kecskemet, Hungary b Kenezy Gyula Memorial Hospital, Neurological Department, Debrecen, Hungary c Kenezy Gyula Memorial Hospital, Department of Child Neurology and Psychiatry, Debrecen, Hungary d University of Pecs, Department of Pediatrics, Pecs, Hungary e University of Pecs, Department of Neurology, Pecs, Hungary
a
Purpose. Anatomical localization of the cortical effect of valproate (VPA) and lamotrigine (LTG) in patients with idiopathic generalized epilepsy (IGE). Methods. 34 patients with untreated IGE were investigated. EEG was recorded in the untreated condition and during monotherapy, three months later, when VPA (15 patients) or LTG (19 patients) treatment abolished the seizures. 19-channel EEG was recorded, and a total of 2 min artifact-free, waking EEG was processed to low resolution electromagnetic tomography (LORETA ) analysis. Activity (that is, current source density, amper/meters squared) was computed in four frequency bands (delta, theta, alpha, beta), for 2394 voxels that represented the cortical gray matter and the hippocampi. Separately for the two subpopulation (patients on VPA and LTG therapy), group differences between the untreated and treated conditions were computed for the four bands and all voxels by multiple t-tests for interdependent datasets. Uncorrected p b 0.01 values were accepted as statistically significant, and were projected to cortical anatomy according to the coordinates of the Talairach Brain Atlas. Results. Statistically significant changes (decrease of activity) emerged in the delta, theta and the alpha bands. In the patients with VPA, VPA decreased delta and theta activity in the entire frontal cortex, insula, anterior temporal cortex and hippocampus, and in the anterior part of the parietal cortex in the delta and theta bands. In the patients with LTG, theta activity decreased in a
Symposium abstracts / International Journal of Psychophysiology 69 (2008) 139–205
Interaction between central and peripheral levels of writing process organization in primary school children M.M. Bezrukikh Russian Academy of Education, Institute of Developmental Physiology, Moscow, Russia The question of central regulation of writing and correlation between central and peripheral levels of movement regulation during writing is still unresolved. There are different approaches to this process; however, the concept of hierarchical organization of the system regulating the movements in question suggested by N.A. Bernstein, which presupposes interaction between brain structures at different levels, is beyond question. Electrical activity (EA) of brain zones involved in movement organization (EEG) and working muscles (EMG) was analyzed to assess interaction between central and peripheral levels of voluntary movement regulation during writing. Coherence analysis of biopotentials of different cortical zones and working muscles (surface flexor and common extensor of the fingers) was performed in 6–7 and 9–10-year old-children. The phenomenon of EEG and EMG synchronization was detected at rest and during preparation for writing, which is believed to reflect interaction between cortical and peripheral levels and provide postural components. It should be noted, that interrelation between brain and muscle biopotentials and its restructuring at different stages of preparation for movements differs significantly in children depending on age and stage of skill acquisition. However, in both age groups correlation between biopotentials of the cortex (irrespective of zone and hemisphere) and agonist muscles is higher than between those of the cortex and antagonist muscles. Another peculiarity to be noted is that an increased number of children with correlation between biopotentials of the frontal cortex and muscles detected in the group with higher level of skill acquisition. At the age of 6–7 more than 70% of the children studied show “connection” between biopotentials of muscles and occipital and central cortical zones, while only 23% show peaks of EA coherence between frontal zone and muscles. At the age of 9–10 the process of joint functional “tuning” during preparation for movement involves frontal cortical zones. Distinct peaks of EA coherence between cortex and muscles predominantly in the alpha-range are noted in 81% of children. As the child develops interlevel interaction restructuring is minimized and interaction between frontal and central cortical zones and muscles is increased during preparation for writing. During writing both at 6–7 and 9–10 years interlevel interaction undergoes restructuring — coherence of electrical activity of brain and both muscles (agonist and antagonist) is decreased significantly in θ, α and β-ranges. However, interaction between brain cortex and muscles is lower in children than in adults, which appears to be related to immaturity of the central mechanisms of graphical movements.
doi:10.1016/j.ijpsycho.2008.05.393 Human brain maturation and ability to recognize and express emotions: A study of preschool aged children A.A. Mekler a, E.V. Vishnevetskaya b Institute of Human Brain Russian Academy of Sciences, Laboratory of Positron-Emission Tomography, Saint Petersburg, Russia b Southern Ural State University, Department of Psychology, Cheliabinsk, Russia
a
Developing child's brain becomes more and more complex with aging. This can be shown by the methods of deterministic chaos theory and fractal analysis, such as estimating of correlation dimension of reconstructed attractor (D2) of EEG or fractal dimension of EEG curve. There are investigations where it is shown, that age increases correlation dimension. Also increasing of EEG's complexity appears as increasing of its fractal dimension. So, we can consider EEG's complexity as a brain maturation index. Therefore we can study the relationship between the brain maturation and different psychic functions. In present work we attempted to find out relationship between brain maturation and emotional competence (ability to recognize and express emotions) in the group of preschoolers — 4–6 years old children, 92 persons. We estimated EEG's complexity, calculating its D2 value. Electroencephalograms were recorded using 19 scalp electrodes according to international system “10–20” and shorted ears electrodes as a reference.
Sampling rate was 250 s− 1, band range — 0.16–70 Hz. During EEG recording subjects were in the state of relaxed wakefulness with opened eyes. We have used for analysis artifact free cuts of EEG recordings, which durability was 16 s (4000 samples). Calculations were performed with unit lag and Theiler's window, which size was estimated by means of space-time separation plot (Mekler A.A., 2007). D2 was calculated for every EEG channel. Emotional competence was evaluated according to special procedure including tests on mimic and pantomimic recognition and expression, graphic expression and vocal recognition and expression of emotions (Vishnevetskaya E.V., Shakurova Z.A., 2006). Due to nonnormal statistical data distribution we used index of cograduation to find out relationship between EEG's complexity and children's emotional competence. It was found that there is direct relation between ability to recognize emotions and D2 in T3 and C3 leads. Ability to express emotions directly relates with D2 in Fz, C3, P3 and O1 leads. Then we have split group under study into three subgroups: 4, 5 and 6 years old. In the subgroups of 4 and 6 years old children there was no relationship between emotional competence and D2. But in the subgroup of 5 years old children it was in the leads Fp1, T3, T5 and P3 — for emotion recognition only. This indicates that in the age of 5 there is reorganization in the brain structures, which provide the ability to recognize and express emotions.
doi:10.1016/j.ijpsycho.2008.05.394 Prenatal hypoxia affects amyloid metabolism and formation of cognitive functions in postnatal ontogenesis of rats I.A. Zhuravin a, N.M. Dubrovskaya a, N.N. Nalivaeva b, A.J. Turner b I.M. Sechenov Institute of Evolutionary Physiology and Biochemistry, RAS, St Petersburg, Russia b University of Leeds, Leeds, United Kingdom
a
Rats subjected to hypoxia (3 h, 7% O2) on 13–14th days of embryogenesis (E13–E14) demonstrated, compared to controls, a delay in physiological development and impaired learning and memory correlated with the changes in the activity of the cholinergic system and the system of biogenesis of cyclic nucleotides as well as with neurodegenerative processes (an increased number of pathologically changed neurons and glial cells, a decreased population of neurons) in the cortex, basal ganglia and hippocampus. In these animals we have found changes in metabolism of amyloid precursor protein (APP) in the cortex and striatum and decreased content of its soluble form produced via restricted proteolysis of APP by a specific metalloprotease, alpha-secretase. The latter represents the non-amyloidogenic pathway of APP cleavage. These changes could underlie memory impairment during later life and were in agreement with memory impairment observed after i.c. injections of an inhibitor of alpha-secretase, batimastat. Moreover, both in the cortex and striatum of animals subjected to prenatal hypoxia there was a decreased expression of some enzymes participating in degradation of the toxic amyloid peptide, formed from APP via its amyloidogenic processing. The principal new data on the role of amyloid-degrading enzymes (ADE) in functioning of the neuronal cells and the brain have been obtained. It was found that expression of ADE increases during the first month of animal postnatal life but then decreases with age. Hypoxia on E13.5 and acute hypoxia in adult rats resulted in a decrease of ADE in all brain structures analysed. Our data testify that prenatal hypoxia, specifically in the period of formation of the neuronal crest, leads to structural changes in the nervous tissue and in APP metabolism which manifest themselves during the lifespan of animals. In humans the risk of development of neurodegeneration and cognitive disorders might increase with age. Supported by grants of RAS “Fundamental Sciences to Medicine” and Saint Petersburg Scientific Center, RBRF (06-04-48414).
doi:10.1016/j.ijpsycho.2008.05.395 Latent EEG characteristics of the brain development via photic driving reaction in normal children and neurologic patients V.V. Lazarev, M.A. Genofre, A. Pontes, L.C. De Azevedo Oswaldo Cruz Foundation, Fernandes Figueira Institute, Rio de Janeiro, Brazil
Symposium abstracts / International Journal of Psychophysiology 69 (2008) 139–205
The EEG driving response to the intermittent photic stimulation (IPS) can enhance the manifestation of latent oscillators not present in the spontaneous EEG. This can provide additional neurophysiological information regarding normal brain development and its pathological alterations. In the present work, this reaction to 11 fixed IPS frequencies (3–24 Hz) were studied in 57 normal children and adolescents and 95 neurologic patients, aged 5–18 years. The topographic characteristics of photic driving proved to be particularly sensitive to the brain maturation. The occurrence of the driving peaks in the spectra of the 12 non-visual areas increased with the age. EEG coherence among these leads at the IPS frequencies and at their harmonics also positively correlated with the age. This means that the brain maturation is normally accompanied by gradual increase in the photic driving reactivity in the anterior cortical areas. In the occipital visual areas, children and adolescents, in contrast to adults, showed similar strong driving responses to the theta IPS frequencies. On the other hand, spontaneous EEG spectra of adolescents were similar to those of adults and differed from those of children by the absence of any peak in the theta band. In this way, the driving reactivity revealed one additional stage of “latent theta oscillators” in the development of the brain electrical activity not apparent in the resting state. In general, the driving amplitude in the delta and theta bands correlated with the age negatively. In 57 patients with partial epilepsy, the number of driving peaks in the spectra of non visual areas was reduced showing a likely delay in brain maturation as well as the effect of the antiepileptic drugs. This interpretation was based on lower driving characteristics in 24 naïve patients in comparison with normal subjects and on the expressed reductions in the driving peaks number and in coherence at the IPS frequencies in 10 naïve patients after a course of treatment with Carbamazepine. Fourteen autistic boys free of drug treatment, with relatively intact verbal and intellectual functions, showed reduced right-side driving reactivity and lower intrahemispheric driving coherence predominantly at the alpha and beta frequencies, probably due to some deficit in right hemisphere activation.
doi:10.1016/j.ijpsycho.2008.05.396 SYMPOSIUM 12: Psychophysiological and Clinical Aspects of Drug-EEG-ERP Interactions Chair: Márk Molnár (Hungary) Effects of the hallucinogenic 5-HT2A agonist psilocybin on object completion in humans F.X. Vollenweider, D. Hell, M. Kometer University of Zurich, University Hospital of Psychiatry, Zurich, Switzerland Background: The preferential serotonin-2A agonist psilocybin is known for its ability to produce a model psychosis including visual hallucinations that mimics some of the signs and symptoms of insipient schizophrenia. Recent studies of visual processing in schizophrenia have indicated disturbances in object completion (Gestalt perception) associated with alterations in the N170 component. Methods: To further elucidate the role of 5-HT2A receptors in illusionary contour processing the effect of psilocybin (115 µg/ and 215 µg/kg vs placebo) on object completion has been assessed using Kanizsa figures and EEG/ERP technique in normal volunteers (n = 16). Kanizsa triangles are stimuli that have been shown to cause significantly increased N170 amplitude responses relative to control stimuli due to the presence of illusory contours and the induced gestalt perception of form. Results: We found that psilocybin dose-dependently impaired object completion associated with a preferential reduction of the N170 amplitude to the Kanizsa relative to Non-Kanizsa stimuli in occipital cortex (V1/V2 and/or LOC). This finding was supported by an additional behavioural visual detection task wherein Kanizsa triangles and real triangles were embedded within fields of distracters. Moreover, the overall reduction of the N170 amplitude in the Kanizsa and the non-Kanizsa condition correlated with the degree of psilocybin-induced visual hallucinations. Conclusion: Given that similar findings were found in schizophrenic patients the present results suggest that a disruption of the serotonergic neurotransmission, particularly at the level the 5-HT2A receptor, may underlay the aberrant object completion found in schizophrenia.
doi:10.1016/j.ijpsycho.2008.05.397
157
Auditory evoked potentials as indicator of brain serotonin system and as predictor of pharmacotherapeutic response in psychiatric patients I. Uhl, G. Juckel Ruhr University, Department of Psychiatry, Bochum, Germany Predictors of treatment response to serotonergic versus non-serotonergic, e.g. noradrenergic, antidepressants are of considerable clinical relevance. Such a prediction of treatment response could help to reduce the number of patients receiving weeks or even months of unsuccessful treatment. Several studies imply that the effectiveness of selective serotonin reuptake inhibitors (SSRI) can be predicted successfully by using the loudness dependence of auditory evoked potentials (LDAEP), which denotes change in the amplitudes in response to different stimulus intensities. Up to now, LDAEP is one of the best validated indicators of the central serotonergic system. The aim of the present study was to investigate whether or not LDAEP also allows the differential prediction of treatment response to serotonergic versus noradrenergic antidepressants. A randomized prospective study was conducted on thirty-five unmedicated in-patients with a DSM-IV diagnosis of major depression (42.5 ± 10.8 years old; 13 male, 22 female, 28.9 ± 5.7 on Hamilton Depression Rating Scale (HDRS)). Before the treatment started, electrophysiological recordings were performed. After that, the patients were treated either with the SSRI citalopram or with the noradrenaline reuptake inhibitor (NARI) reboxetine for four weeks. ANOVA revealed that responders to the citalopram treatment (50% improvement on HDRS) were characterized by a strong LDAEP at baseline, and responders to reboxetine by a weak LDAEP. Non-responders to citalopram or reboxetine showed inverse LDAEP characteristics, respectively. This finding demonstrates differential prediction of response to different classes of antidepressants. Patients with an initially strong LDAEP rather seem to respond to a serotonin-agonistic antidepressant; patients with a weak LDAEP will more likely benefit from a non-serotonergic, e.g. noradrenergic, antidepressant. If these results were replicated in a larger sample, the simple method of evaluating the LDAEP before the start of an antidepressive treatment could be introduced broadly. LDAEP measurement could replace the current trial and error principle of antidepressant treatment and thus support physicians in their clinical work.
doi:10.1016/j.ijpsycho.2008.05.398 Effect of valproate and lamotrigine in patients with idiopathic generalized epilepsy revealed by LORETA analysis I. Kondakor a, P. Piros b, M. Bessenyei c, K. Hollody d, M. Toth e, B. Clemens b County Teaching Hospital, Department of Neurology, Kecskemet, Hungary b Kenezy Gyula Memorial Hospital, Neurological Department, Debrecen, Hungary c Kenezy Gyula Memorial Hospital, Department of Child Neurology and Psychiatry, Debrecen, Hungary d University of Pecs, Department of Pediatrics, Pecs, Hungary e University of Pecs, Department of Neurology, Pecs, Hungary
a
Purpose. Anatomical localization of the cortical effect of valproate (VPA) and lamotrigine (LTG) in patients with idiopathic generalized epilepsy (IGE). Methods. 34 patients with untreated IGE were investigated. EEG was recorded in the untreated condition and during monotherapy, three months later, when VPA (15 patients) or LTG (19 patients) treatment abolished the seizures. 19-channel EEG was recorded, and a total of 2 min artifact-free, waking EEG was processed to low resolution electromagnetic tomography (LORETA ) analysis. Activity (that is, current source density, amper/meters squared) was computed in four frequency bands (delta, theta, alpha, beta), for 2394 voxels that represented the cortical gray matter and the hippocampi. Separately for the two subpopulation (patients on VPA and LTG therapy), group differences between the untreated and treated conditions were computed for the four bands and all voxels by multiple t-tests for interdependent datasets. Uncorrected p b 0.01 values were accepted as statistically significant, and were projected to cortical anatomy according to the coordinates of the Talairach Brain Atlas. Results. Statistically significant changes (decrease of activity) emerged in the delta, theta and the alpha bands. In the patients with VPA, VPA decreased delta and theta activity in the entire frontal cortex, insula, anterior temporal cortex and hippocampus, and in the anterior part of the parietal cortex in the delta and theta bands. In the patients with LTG, theta activity decreased in a