- Email: [email protected]
P9.4 Cognitive event-related potentials: method for testing features of working memory using the Sternberg memory task
S102 loss, which leads to disabilities too. Correlations with PASAT, MMSE and education lead to consider P300 as a handle marker of cognitive impairment in MS. P9.4 Cognitive event-related potentials: method for testing features of working memory using the Sternberg memory task M. Krbot1 , A.B. Sefer1 , M. Cifrek2 , K. Krbot3 , V. Isgum4 1 University of Zagreb, Zagreb, Croatia, 2 University of Zagreb, Faculty of Electrical Engineering and Computing, Zagreb, Croatia, 3 University of Zagreb, School of Medicine, Zagreb, Croatia, 4 University Hospital Zagreb, Zagreb, Croatia Introduction: Different kinds of cognitive impairments have specific influence on a working memory. Most of the methods used in a routine cognitive testing of a working memory are behavioral methods and these methods could sometimes be submissive to the influence of patients. Objectives: The aim of our research is to establish reliable and quantitative neurophysiological method appropriate for patients with different kinds of cognitive impairments in order to test features of the working memory. Therefore we performed modified Sternberg memory task. Methods: Twenty-one (14 male and 7 female) healthy right handed adults with no auditory impairments participated in the study. In the Sternberg experiment, sets of two or four digits were acoustically presented to subjects. After the last item in the set, the target digit (probe) was presented. Participants had to indicate whether the probe did (positive probe) or did not (negative probe) belong to the presented set by pressing appropriate buttons. Results of the study are cognitive auditory eventrelated potentials and associated reaction times. Results: Obtained results show that the increase of the memory set size would elicit the increase of the reaction time and the increase of the latency of the specific component of event-related potentials (P300 the cognitive component). The activity in the period in which participants rehearse the previously presented set is stronger expressed for the set consisted of less digits (two). The amplitude of the cognitive component is greater for the positive probe than for the negative probe and the latency of the cognitive component is greater for the negative probe. Conclusions: Findings coming out of this research show that cognitive event-related potentials are an appropriate method for testing features of the working memory. They are in accordance with the presently accepted theory. These findings are being used in order to make a clinical diagnostic method appropriate for patients with different kinds of cognitive impairments. P9.5 Effects of repetitive transcranial magnetic stimulation of the primary motor cortex on the early and late components of CNV and motor reaction time in normal subjects E. Vecchio1 , V. De Vito Francesco1 , F. Giovanni1 , C. Serpino1 , M. Delussi1 , M. de Tommaso1 1 Neurological Clinic, Policlinico, University of Bari, Bari, Italy Introduction: The early and late components of the Contingent Negative Variation (CNV) express the arousal and preparative attention preceding a voluntary movement. Objectives: The aim of the study was to evaluate the effects of inhibition of the motor cortex induced by 1 Hz rTMS on the early and late components of the CNV and on the motor reaction time in normal subjects. Methods: Seven healthy subjects were evaluated. The rTMS was delivered over the hand motor cortex of the left hemisphere. We obtained the CNV in the 3 conditions (basal, after magnetic trans-cranial stimulation, after sham stimulation). We performed an automatic analysis of the amplitude of the early CNV in the time interval 550 750 ms, and of the late CNV in the time interval 2700 3000 in the 3 conditions. Results: The amplitude of the early and late CNV appeared to be significantly higher when the left motor cortex was inhibited by low frequency TMS modulation, compared to the sham and basal conditions. The reaction time appeared to be reduced in the condition of inhibition of the motor cortex, even if not significantly. Conclusion: The inhibition of the motor cortex seems to cause an increase in the amplitude of both the the early and late components of the CNV. This would suggest that in normal subjects, the attention and the arousal preceding the voluntary movement are increased by the temporary inhibition of the motor cortex. This experimental model is interesting for the evaluation of the cognitive mechanisms able to compensate the reduced function of the motor cortex.
Poster presentations: Poster session 9. Event related potentials P9.6 Auditory lexical-semantic processing differences in young children with autism spectrum disorders: an ERP study G. Zito1 , F. Bianchi di Castelbianco1 , G. Lucci2 , M. Di Renzo3 Istituto di Ortofonologia, Centro Diagnosi e Valutazione, Rome, Italy, 2 Universit` a degli Studi di Roma “Foro Italico”, Piazza L. De Bosis 15, Rome, Italy, 3 Istituto di Ortofonologia, Rome, Italy
1
Introduction: Autism spectrum disorders (ASDs) encompass conditions characterized by pervasively compromised social interaction capabilities, verbal and nonverbal communication deficits and stereotyped behaviour. Several electrophysiological studies showed decreased amplitudes of cognitive brain responses related to information processing, especially in language and communication abilities. Very little is known about the neural correlates of the auditory processing in young ASDs patients during word listening. Objectives: To examine whether auditory event-related potentials (ERPs) associated with cognitive word processing are better modulated by a semantic factor (words vs. pseudowords) and/or by an environmental expected to have a facilitating effect vs. factor (familiar voice unfamiliar voice). Methods: ERPs were recorded from 24 ASDs children (19 M, 5 F; age 6.1±2.6) through 19 channels standard EEG; 18 normally developing children (10 M, 8 F; age 6.3±2.6) served as controls (NC). Each subject underwent passive auditory listening of 15 digitally recorded words and pseudo-words both pronounced by a familiar (mother) or unfamiliar female voice, in four trials. ANOVAs on both ERPs latency and amplitudes were performed. Results: A reliable positive ERPs component was found 200 300 ms after the word onset on medial frontal sensor (Fz). Its latency was delayed in ASDs children (300 ms, p = 0.002) compared to NC (235 ms) for all conditions except for the words heard from an unfamiliar voice (255 ms ASDs, 266 ms NC), which did not differ. Regarding the amplitude, ASDs children showed a larger response (8 vs. 4 mV; p = 0.001) than controls in all conditions except for the familiar words (5.8 mV). Conclusion: Word processing would be differently modulated by environmental and semantic factors in ASDs children. Maternal voice did not show the expected facilitating effect. Additional studies are necessary to rule out the influence of environment upon these neurophysiological features. P9.7 Evoked potentials of spontaneous movements: delayed preparation in Parkinson’s disease patients A.B. Sefer1 , M. Krbot1 , M. Cifrek2 , S. Telarovic3 , V. Isgum3 1 University of Zagreb, Zagreb, Croatia, 2 University of Zagreb, Faculty of Electrical Engineering and Computing, Zagreb, Croatia, 3 University Hospital Zagreb, Zagreb, Croatia Introduction: Movement-related evoked potentials (MREPs) represent an activity that occurs mostly in brain motor areas during a movement execution. This activity emerges about 1.5 s before a movement onset and represents movement planning, preparation and execution. A spontaneous movement execution has been shown to be impaired in Parkinson’s disease (PD) patients, causing changes in their MREPs. Objectives: The aim of our study is to provide a new diagnostic tool for PD using MREPs. Considering the inconsistency of results of previously performed studies in this field, we realized the importance of choosing the group of PD patients that is as homogeneous as possible, considering patient’s age, disease severity, medication intake and other factors that might influence MREPs. Methods: Two groups of participants, PD patients (8 males, 2 females; all right onset PD; age 55.7+/-5.3) and healthy controls (10 males, 1 female; age 23.45+/-0.68), were asked to perform spontaneous thumb movements repeated every 5 10 s. Electroencephalogram (EEG) was recorded and evoked potentials were extracted. Results: PD patients showed the later onset of the beginning of MREPs, known as the Bereitschaftspotential (BP) or readiness potential (RP). The BP latency delay was observed for an affected hand, but not for a healthy hand. Conclusions: This study confirmed that MREPs are influenced by PD. We were able to distinguish PD patients’ MREPs from healthy controls’ MREPs. We were also able to distinguish the side of the body affected by the disease within the PD group. Further work implies establishing normative data for MREPs of PD patients and age matched healthy controls. In future
Poster presentations: Poster session 9. Event related potentials P9.6 Auditory lexical-semantic processing differences in young children with autism spectrum disorders: an ERP study G. Zito1 , F. Bianchi di Castelbianco1 , G. Lucci2 , M. Di Renzo3 Istituto di Ortofonologia, Centro Diagnosi e Valutazione, Rome, Italy, 2 Universit` a degli Studi di Roma “Foro Italico”, Piazza L. De Bosis 15, Rome, Italy, 3 Istituto di Ortofonologia, Rome, Italy
1
Introduction: Autism spectrum disorders (ASDs) encompass conditions characterized by pervasively compromised social interaction capabilities, verbal and nonverbal communication deficits and stereotyped behaviour. Several electrophysiological studies showed decreased amplitudes of cognitive brain responses related to information processing, especially in language and communication abilities. Very little is known about the neural correlates of the auditory processing in young ASDs patients during word listening. Objectives: To examine whether auditory event-related potentials (ERPs) associated with cognitive word processing are better modulated by a semantic factor (words vs. pseudowords) and/or by an environmental expected to have a facilitating effect vs. factor (familiar voice unfamiliar voice). Methods: ERPs were recorded from 24 ASDs children (19 M, 5 F; age 6.1±2.6) through 19 channels standard EEG; 18 normally developing children (10 M, 8 F; age 6.3±2.6) served as controls (NC). Each subject underwent passive auditory listening of 15 digitally recorded words and pseudo-words both pronounced by a familiar (mother) or unfamiliar female voice, in four trials. ANOVAs on both ERPs latency and amplitudes were performed. Results: A reliable positive ERPs component was found 200 300 ms after the word onset on medial frontal sensor (Fz). Its latency was delayed in ASDs children (300 ms, p = 0.002) compared to NC (235 ms) for all conditions except for the words heard from an unfamiliar voice (255 ms ASDs, 266 ms NC), which did not differ. Regarding the amplitude, ASDs children showed a larger response (8 vs. 4 mV; p = 0.001) than controls in all conditions except for the familiar words (5.8 mV). Conclusion: Word processing would be differently modulated by environmental and semantic factors in ASDs children. Maternal voice did not show the expected facilitating effect. Additional studies are necessary to rule out the influence of environment upon these neurophysiological features. P9.7 Evoked potentials of spontaneous movements: delayed preparation in Parkinson’s disease patients A.B. Sefer1 , M. Krbot1 , M. Cifrek2 , S. Telarovic3 , V. Isgum3 1 University of Zagreb, Zagreb, Croatia, 2 University of Zagreb, Faculty of Electrical Engineering and Computing, Zagreb, Croatia, 3 University Hospital Zagreb, Zagreb, Croatia Introduction: Movement-related evoked potentials (MREPs) represent an activity that occurs mostly in brain motor areas during a movement execution. This activity emerges about 1.5 s before a movement onset and represents movement planning, preparation and execution. A spontaneous movement execution has been shown to be impaired in Parkinson’s disease (PD) patients, causing changes in their MREPs. Objectives: The aim of our study is to provide a new diagnostic tool for PD using MREPs. Considering the inconsistency of results of previously performed studies in this field, we realized the importance of choosing the group of PD patients that is as homogeneous as possible, considering patient’s age, disease severity, medication intake and other factors that might influence MREPs. Methods: Two groups of participants, PD patients (8 males, 2 females; all right onset PD; age 55.7+/-5.3) and healthy controls (10 males, 1 female; age 23.45+/-0.68), were asked to perform spontaneous thumb movements repeated every 5 10 s. Electroencephalogram (EEG) was recorded and evoked potentials were extracted. Results: PD patients showed the later onset of the beginning of MREPs, known as the Bereitschaftspotential (BP) or readiness potential (RP). The BP latency delay was observed for an affected hand, but not for a healthy hand. Conclusions: This study confirmed that MREPs are influenced by PD. We were able to distinguish PD patients’ MREPs from healthy controls’ MREPs. We were also able to distinguish the side of the body affected by the disease within the PD group. Further work implies establishing normative data for MREPs of PD patients and age matched healthy controls. In future