Electroencephalography and Clinical Neurophysiology, 1995
Recent studies from our laboratory have resulted in the identification of an event-related potent... more Recent studies from our laboratory have resulted in the identification of an event-related potential (ERP) correlate of a visual memory process. This memory process is reflected by a reduction in the voltage of the visual memory potential (VMP) to repeated pictures of unfamiliar faces compared te novel pictures of faces. In the current experiment we used unfamiliar and famous faces in an identical repetition priming paradigm, while the subject differentially recognized famous from non-famous faces. Significant differences in response times were obtained between primed and unprimed familiar faces, but not between primed and unprimed unfamiliar faces. The VMP was reduced to primed unfamiliar faces and significantly diminished to primed familiar faces compared to unprimed stimuli. Priming was typically reflected by a reduction of the VMP at the occipito-temporal region, whereas recognition resulted in a diminution of the VMP at both the occipito-temporal region and at the frontal region. These data support the involvement of differential neural systems for priming and recognition of visual stimuli.
In this paper, we propose three new measures for topographic studies of event related potentials ... more In this paper, we propose three new measures for topographic studies of event related potentials (ERP) called the surface energy (SE), its density (SED) and the distance of surface energy density fields (DSED) based on the entire scalp current density (SCD) field. These measures have a specific physical meaning, are free of the reference electrode and any physical conductive model of the head. They capture not only spatial properties, but also continuous time elements present and smeared in the original scalp potential records. They provide a common base for comparisons of recorded potentials among different time points, subjects, regions on the scalp, or experimental conditions. We also construct a statistical inference based on these new measures, and provide an application to human event-related potentials in a visual short-term memory experiment.
In our previous studies, we have demonstrated an ERP correlate of visual memory with a modified d... more In our previous studies, we have demonstrated an ERP correlate of visual memory with a modified delayed matching-to-sample paradigm using a series of nonsense line drawings or faces as stimuli. In this experiment, we employed pictures of objects to determine whether the ERP can reflect the object recognition process and whether visual stimuli with a verbal label would result in a different topographic distribution from past topography obtained with visual stimuli without a verbal label. The results of this study suggest that the amplitude of the ERP component (c247) to repeated (primed) pictures of common objects was significantly decreased as compared to the unrepeated (unprimed) pictures; the latency for the peak of c247 was decreased for the repeated compared to the unrepeated, and the response time was also significantly shorter to the repeated picture stimuli than to the unrepeated; the topographical distribution of c247 was mainly located in the occipitotemporal areas of the brain. However, the source energy density map showed that the topographic involvement of the brain regions to the c247 was different in the matching and nonmatching trials.
P300 recordings were made from males at high risk (HR) for alcoholism and low-risk (LR) controls,... more P300 recordings were made from males at high risk (HR) for alcoholism and low-risk (LR) controls, participating in a visual go/no go reaction time paradigm. The go (button press) and no go (inhibit response) stimuli were large and small forms of the same letters. The LR group had significantly larger go than no go P300 amplitudes in the central, parietal, and temporal regions; the HR group manifested no response differences in any region. In the LR group compared to the HR group, both go and no go response amplitudes were larger over the entire head; no group differences in latencies were observed in any region. Surface energy magnitudes paralleled P300 amplitudes and were also larger in the LR group during both go and no go trials. Our findings indicate that HR individuals manifest widespread P300 amplitude deficits while performing a simple information-processing paradigm. These deficits, which may reflect genetic influences, preceded the onset of alcoholism and may function as a phenotypic marker for its development.
Electroencephalography and Clinical Neurophysiology, 1995
Recent studies from our laboratory have resulted in the identification of an event-related potent... more Recent studies from our laboratory have resulted in the identification of an event-related potential (ERP) correlate of a visual memory process. This memory process is reflected by a reduction in the voltage of the visual memory potential (VMP) to repeated pictures of unfamiliar faces compared te novel pictures of faces. In the current experiment we used unfamiliar and famous faces in an identical repetition priming paradigm, while the subject differentially recognized famous from non-famous faces. Significant differences in response times were obtained between primed and unprimed familiar faces, but not between primed and unprimed unfamiliar faces. The VMP was reduced to primed unfamiliar faces and significantly diminished to primed familiar faces compared to unprimed stimuli. Priming was typically reflected by a reduction of the VMP at the occipito-temporal region, whereas recognition resulted in a diminution of the VMP at both the occipito-temporal region and at the frontal region. These data support the involvement of differential neural systems for priming and recognition of visual stimuli.
In this paper, we propose three new measures for topographic studies of event related potentials ... more In this paper, we propose three new measures for topographic studies of event related potentials (ERP) called the surface energy (SE), its density (SED) and the distance of surface energy density fields (DSED) based on the entire scalp current density (SCD) field. These measures have a specific physical meaning, are free of the reference electrode and any physical conductive model of the head. They capture not only spatial properties, but also continuous time elements present and smeared in the original scalp potential records. They provide a common base for comparisons of recorded potentials among different time points, subjects, regions on the scalp, or experimental conditions. We also construct a statistical inference based on these new measures, and provide an application to human event-related potentials in a visual short-term memory experiment.
In our previous studies, we have demonstrated an ERP correlate of visual memory with a modified d... more In our previous studies, we have demonstrated an ERP correlate of visual memory with a modified delayed matching-to-sample paradigm using a series of nonsense line drawings or faces as stimuli. In this experiment, we employed pictures of objects to determine whether the ERP can reflect the object recognition process and whether visual stimuli with a verbal label would result in a different topographic distribution from past topography obtained with visual stimuli without a verbal label. The results of this study suggest that the amplitude of the ERP component (c247) to repeated (primed) pictures of common objects was significantly decreased as compared to the unrepeated (unprimed) pictures; the latency for the peak of c247 was decreased for the repeated compared to the unrepeated, and the response time was also significantly shorter to the repeated picture stimuli than to the unrepeated; the topographical distribution of c247 was mainly located in the occipitotemporal areas of the brain. However, the source energy density map showed that the topographic involvement of the brain regions to the c247 was different in the matching and nonmatching trials.
P300 recordings were made from males at high risk (HR) for alcoholism and low-risk (LR) controls,... more P300 recordings were made from males at high risk (HR) for alcoholism and low-risk (LR) controls, participating in a visual go/no go reaction time paradigm. The go (button press) and no go (inhibit response) stimuli were large and small forms of the same letters. The LR group had significantly larger go than no go P300 amplitudes in the central, parietal, and temporal regions; the HR group manifested no response differences in any region. In the LR group compared to the HR group, both go and no go response amplitudes were larger over the entire head; no group differences in latencies were observed in any region. Surface energy magnitudes paralleled P300 amplitudes and were also larger in the LR group during both go and no go trials. Our findings indicate that HR individuals manifest widespread P300 amplitude deficits while performing a simple information-processing paradigm. These deficits, which may reflect genetic influences, preceded the onset of alcoholism and may function as a phenotypic marker for its development.
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