- Email: [email protected]
An evaluation of P50 suppression methodologies
252
Abstracts / International Journal of Psychophysiology 77 (2010) 239–287
press after other types of stimuli. EEG was recorded by a 19-channel Electrocap with electrodes attached according to 10-20 system. Button signal was registered to control the reaction time and the amount of mistakes during test execution. EEG was processed using common average montage. Separation of independent components was performed by INFOMAX algorithm automatically in WinEEG. Spatial filters were constructed using the database (249 healthy subjects of age from 18 to 40) and were used to separate eight independent components with the greatest amplitude. Independent components were averaged separately by groups of schizophrenics and healthy subjects (20 age-matched participants). Statistical analysis was performed using t-test for independent groups. Independent components' topographies were determined by means of sLORETA. Behavioral data analysis concluded that schizophrenics made more omission mistakes compared to healthy subjects. Analysis for independent components of ERPs from probe Go revealed that the amplitude of components with latency around 300 ms significantly decreased in the group of schizophrenics. This component is generated in the parietal area and is thought to be connected with action engagement. Analysis for independent components of ERPs from probe NoGo revealed that schizophrenics had significantly greater amplitude of early component generated in the left posterior temporal area and significantly smaller amplitude of components with latency around 400 ms, which was generated in the anterior cingulate cortex and was likely connected with action monitoring. Also, schizophrenics had a significantly smaller amplitude for the component of ERPs from second stimulus in probe Novel, which was generated in the central area and was likely connected with novelty reaction. The most prominent decrease was observed for the independent component with latency around 300 ms of ERPs from probe NoGo. According to sLORETA this component is generated in the premotor area and is supposed to be connected with action suppression. The similar amplitude changes were revealed during individual data analysis. This observation suggests there is a possibility of using these methods for early diagnosis of schizophrenia.
doi:10.1016/j.ijpsycho.2010.06.064
An evaluation of P50 suppression methodologies Anna Dalecki, Rodney J. Croft, Stuart J. Johnstone Brain and Behaviour Research Institute and School of Psychology, University of Wollongong, Australia Reduced P50 suppression in schizophrenia is reported to be an endophenotype for the disorder. However, the utility of the P50 suppression index in schizophrenia research is limited by several unresolved methodological issues. These include (i) the failure to demonstrate that P50 suppression can be reliably measured, (ii) unknown effects of time-on-task on P50 suppression, and (iii) the long duration of the P50 suppression recording session; due in part to the long inter-pair interval typically employed in the paired-click paradigm. The present study addressed these issues. Methods: The P50 suppression ratios of 20 healthy undergraduate students were measured in a paired-click paradigm. A total of 750 click-pairs were presented with a constant (500 ms) interval between the first and second stimuli, and one of five inter-pair intervals (1, 3, 5, 7 and 9 s) between successive pairs of clicks. This allowed for the estimation of within-session reliability, the temporal course of P50 suppression over the 78 min recording, and the effect of varying the duration of the inter-pair interval on the P50 suppression ratio. Results: Intraclass correlation coefficients (ICC) estimated the within-session reliability of P50 suppression at ICC = .441 (p = .001). Results indicated that the magnitude of the P50 suppression ratio
increased by 39% over the 78 minute recording. Varying the duration of the inter-pair interval had no effect on the P50 suppression ratio. Conclusions: The implications of these results for the design for P50 suppression studies are discussed. In particular, these results highlight the need to take time-on-task effects into account when recording P50 suppression in a long paradigm. Furthermore, the duration of the inter-pair interval was reduced from 9 to 1 s without affecting the magnitude of P50 suppression. It is thus concluded that the inter-pair interval can be shortened in the paired-click paradigm, considerably reducing P50 suppression recording time.
doi:10.1016/j.ijpsycho.2010.06.065
Neurophysiological studies of sensory gating in schizophrenia: Clinical relevance and promises in the search for pharmacologic and non-pharmacologic interventions Zeinab S. Elbaz Mount Sinai School of Medicine, Dept of Psychiatry, New York, USA Learning objectives: At the conclusion of this session, the participant will be able to recognize the role sensory gating abnormalities play in the pathophysiology of schizophrenia, their neurobiological mechanisms, and the potential utility of neurophysiological tests as a useful screening tool of new candidate antipsychotic medications. Methods: Integrating the most recent research and clinical data on the subject using PubMed and Medline database. Discussion: Sensory gating abnormalities are trait-linked markers of vulnerability to schizophrenia disorders seen across the spectrum and are amenable to linkage studies. They also have state-related contributions associated with the level of psychosis and neurocognitive deficits. We are bombarded continually with sensory information in multiple modalities, as well as the information that our memory system has stored. The dramatic symptoms of schizophrenia can be viewed as maladaptive attempts to integrate abnormal sensory and information input. Schizophrenia patients exhibit significant loss of inhibition on a variety of neurophysiological tests, such as prepulse inhibition of the startle response and P50 gating. The functional significance of these inhibitory failures is that individuals cannot apportion attentional resources to salient or more important stimuli. These techniques measure the non-volitional physiological responses of human subjects in a specific paradigm, often where cognitive processes are manipulated using various tasks. A parallel series of studies in humans implicated the alpha 7 nicotinic acetylcholine receptor in the physiology of P50 auditory gating. This inhibitory process is mediated by enhancing the release of GABA leading to the decrease of glutamate. The alpha nicotinic agonist DMXBA can enhance auditory sensory gating in animal models. DMXBA is well-tolerated in humans and a new study in persons with schizophrenia has found that DMXBA enhances both P50 auditory gating and cognition. A case report by Rosse and Deutsch, 2002, found that adjuvant galantamine, the anticholinestrase inhibitor and allosteric nicotinic receptor modulator, improved the scores on the assessment of negative symptoms. Conclusion: Contrary to our intuitive understanding, perceptions are not precise copies of the world around us. Information is edited in stages; the output is rarely the same as its input. Information may be amplified or attenuated. The neurophysiological evidence for defective inhibitory pathways in schizophrenia not only will help with identifying the neurobiological mechanisms in schizophrenia, but will also change
Abstracts / International Journal of Psychophysiology 77 (2010) 239–287
press after other types of stimuli. EEG was recorded by a 19-channel Electrocap with electrodes attached according to 10-20 system. Button signal was registered to control the reaction time and the amount of mistakes during test execution. EEG was processed using common average montage. Separation of independent components was performed by INFOMAX algorithm automatically in WinEEG. Spatial filters were constructed using the database (249 healthy subjects of age from 18 to 40) and were used to separate eight independent components with the greatest amplitude. Independent components were averaged separately by groups of schizophrenics and healthy subjects (20 age-matched participants). Statistical analysis was performed using t-test for independent groups. Independent components' topographies were determined by means of sLORETA. Behavioral data analysis concluded that schizophrenics made more omission mistakes compared to healthy subjects. Analysis for independent components of ERPs from probe Go revealed that the amplitude of components with latency around 300 ms significantly decreased in the group of schizophrenics. This component is generated in the parietal area and is thought to be connected with action engagement. Analysis for independent components of ERPs from probe NoGo revealed that schizophrenics had significantly greater amplitude of early component generated in the left posterior temporal area and significantly smaller amplitude of components with latency around 400 ms, which was generated in the anterior cingulate cortex and was likely connected with action monitoring. Also, schizophrenics had a significantly smaller amplitude for the component of ERPs from second stimulus in probe Novel, which was generated in the central area and was likely connected with novelty reaction. The most prominent decrease was observed for the independent component with latency around 300 ms of ERPs from probe NoGo. According to sLORETA this component is generated in the premotor area and is supposed to be connected with action suppression. The similar amplitude changes were revealed during individual data analysis. This observation suggests there is a possibility of using these methods for early diagnosis of schizophrenia.
doi:10.1016/j.ijpsycho.2010.06.064
An evaluation of P50 suppression methodologies Anna Dalecki, Rodney J. Croft, Stuart J. Johnstone Brain and Behaviour Research Institute and School of Psychology, University of Wollongong, Australia Reduced P50 suppression in schizophrenia is reported to be an endophenotype for the disorder. However, the utility of the P50 suppression index in schizophrenia research is limited by several unresolved methodological issues. These include (i) the failure to demonstrate that P50 suppression can be reliably measured, (ii) unknown effects of time-on-task on P50 suppression, and (iii) the long duration of the P50 suppression recording session; due in part to the long inter-pair interval typically employed in the paired-click paradigm. The present study addressed these issues. Methods: The P50 suppression ratios of 20 healthy undergraduate students were measured in a paired-click paradigm. A total of 750 click-pairs were presented with a constant (500 ms) interval between the first and second stimuli, and one of five inter-pair intervals (1, 3, 5, 7 and 9 s) between successive pairs of clicks. This allowed for the estimation of within-session reliability, the temporal course of P50 suppression over the 78 min recording, and the effect of varying the duration of the inter-pair interval on the P50 suppression ratio. Results: Intraclass correlation coefficients (ICC) estimated the within-session reliability of P50 suppression at ICC = .441 (p = .001). Results indicated that the magnitude of the P50 suppression ratio
increased by 39% over the 78 minute recording. Varying the duration of the inter-pair interval had no effect on the P50 suppression ratio. Conclusions: The implications of these results for the design for P50 suppression studies are discussed. In particular, these results highlight the need to take time-on-task effects into account when recording P50 suppression in a long paradigm. Furthermore, the duration of the inter-pair interval was reduced from 9 to 1 s without affecting the magnitude of P50 suppression. It is thus concluded that the inter-pair interval can be shortened in the paired-click paradigm, considerably reducing P50 suppression recording time.
doi:10.1016/j.ijpsycho.2010.06.065
Neurophysiological studies of sensory gating in schizophrenia: Clinical relevance and promises in the search for pharmacologic and non-pharmacologic interventions Zeinab S. Elbaz Mount Sinai School of Medicine, Dept of Psychiatry, New York, USA Learning objectives: At the conclusion of this session, the participant will be able to recognize the role sensory gating abnormalities play in the pathophysiology of schizophrenia, their neurobiological mechanisms, and the potential utility of neurophysiological tests as a useful screening tool of new candidate antipsychotic medications. Methods: Integrating the most recent research and clinical data on the subject using PubMed and Medline database. Discussion: Sensory gating abnormalities are trait-linked markers of vulnerability to schizophrenia disorders seen across the spectrum and are amenable to linkage studies. They also have state-related contributions associated with the level of psychosis and neurocognitive deficits. We are bombarded continually with sensory information in multiple modalities, as well as the information that our memory system has stored. The dramatic symptoms of schizophrenia can be viewed as maladaptive attempts to integrate abnormal sensory and information input. Schizophrenia patients exhibit significant loss of inhibition on a variety of neurophysiological tests, such as prepulse inhibition of the startle response and P50 gating. The functional significance of these inhibitory failures is that individuals cannot apportion attentional resources to salient or more important stimuli. These techniques measure the non-volitional physiological responses of human subjects in a specific paradigm, often where cognitive processes are manipulated using various tasks. A parallel series of studies in humans implicated the alpha 7 nicotinic acetylcholine receptor in the physiology of P50 auditory gating. This inhibitory process is mediated by enhancing the release of GABA leading to the decrease of glutamate. The alpha nicotinic agonist DMXBA can enhance auditory sensory gating in animal models. DMXBA is well-tolerated in humans and a new study in persons with schizophrenia has found that DMXBA enhances both P50 auditory gating and cognition. A case report by Rosse and Deutsch, 2002, found that adjuvant galantamine, the anticholinestrase inhibitor and allosteric nicotinic receptor modulator, improved the scores on the assessment of negative symptoms. Conclusion: Contrary to our intuitive understanding, perceptions are not precise copies of the world around us. Information is edited in stages; the output is rarely the same as its input. Information may be amplified or attenuated. The neurophysiological evidence for defective inhibitory pathways in schizophrenia not only will help with identifying the neurobiological mechanisms in schizophrenia, but will also change