Biomedical subjects

Elena V Mnatsakanian

Publications and source records attributed to Elena V Mnatsakanian.

4 recordsLinked to original sources

PubMed2004

Familiar-face recognition and comparison: source analysis of scalp-recorded event-related potentials.

OBJECTIVE: We studied the event-related potentials elicited by categorical matching of faces. The purpose was to find cortical sources responsible for face recognition and comparison. METHODS: Nineteen healthy volunteers participated in the study. Each trial began with one of the two cues (S1) followed by consecutive pictures (S2 and S3). Each picture was a photograph of a familiar face with a superimposed abstract dot pattern. One cue directed attention to compare faces and another to compare patterns. 128-channel electroencephalogram was recorded. Spatio-temporal multiple dipole source models were generated using Brain Electromagnetic Source Analysis 2000, for the window of 80-600 ms from S3 onset. RESULTS: The obtained model for face recognition and comparison contained 8 dipoles explaining 97% of grand average and about 90% of individual data and showing temporal and spatial separation of sources: in the frontal region, in the occipital cortex, and in the bilateral medial temporal and inferotemporal regions. Different faces elicited larger components than same person's faces around 400 ms, mainly explained by frontal dipoles. CONCLUSIONS: The sources in our models estimate the activity common for both Face task conditions (the recognition of a familiar person) and also differential activity, related to the match/mismatch item processing.

Adult↗

PubMed2003

Matching of familiar faces and abstract patterns: behavioral and high-resolution ERP study.

Electrical scalp-recorded components peaking approximately 350-400 ms were reported to be sensitive to both repetition/priming effects and face familiarity. We studied the categorical matching of familiar faces and compared it to the matching of abstract patterns. Nineteen healthy volunteers participated in the study. Each trial began with one of the two cues (S1) followed by consecutive pictures (S2 and S3). Each picture was a photograph of a familiar face with a superimposed abstract dot pattern. One cue directed attention to compare faces and another to compare patterns. Participants were asked to respond by pressing different buttons. A 128-channel EEG was recorded. Analysis was done for the 600-ms window from the S3 onset, for correct performance. The face comparison was better and faster than the pattern comparison. In the Face task, match/mismatch differences were local in 200-250 ms and large and widespread in 270-550 ms. In the Pattern task, differences were found in 30-270 ms, while on longer latencies they were lesser than those in the Face task. Priming was observed in the Face task as shorter reaction times and reduced N400-like components (both in prefrontal and parietal regions) for the same items as compared to the different ones. In the Pattern task, the results were more controversial.

Adult↗

PubMed2003

Functional specialization in the human frontal cortex observed during task anticipation.

The purpose was to evaluate whether a scalp-recorded slow potential will show specificity during the anticipation of different types of visual tasks. One of the tasks required the comparison of pairs of familiar faces, and the other was the comparison of abstract dotted patterns. Each trial began with one of the two cues (S1) followed by consecutive pictures (S2 and S3). Faces and patterns were superimposed, and the switching between tasks depended on the cue. The ERP analysis was done for the time window between S1 (cue) and S2 presentations. The major differences between tasks were found in the anterior scalp regions starting at 700 ms from S1 onset. During Pattern task anticipation, the proposed sources in the right frontal area were more anterior, inferior and lateral than those in Face task. The task-specific slow electric potentials may indicate the functional specialization for attentive anticipation in the human frontal lobe.

Adult↗

PubMed2002

Task-specific expectation is revealed in scalp-recorded slow potentials.

The contingent negative variation (CNV) is known as an electrical manifestation of expectancy, readiness and attention. The purpose of this study was to evaluate whether slow potentials recorded from the human scalp during the expectation to perform different tasks or during the expectation of the second stimulus in the pair demonstrate specificity regarding the type of visual stimuli. Participants were nineteen healthy adults. Each trial began with one of the two cues (S1) followed by consecutive pictures (S2 and S3). Each picture of this pair was a photograph of a familiar face with superimposed abstract dot pattern. One cue directed attention to compare faces and another to compare patterns. EEG was recorded with a 128-channel net. Slow potentials following S1 and S2 presentation (SP1 and SP2) are reported here for Face and Pattern tasks. The duration of each segment of the trial was 1500 ms from the stimulus onset, and here the last 1000 ms was analyzed. Statistical comparisons of amplitudes and current density mapping were performed. Within the same task, SP1-SP2 differences were complex, implying multiple dissimilarities in the processes during the two expectation periods. Slow potentials in SP1 differed between the tasks mostly in the anterior recording sites in 700-1500 ms. These latencies corresponded to the late CNV (or stimulus preceding negativity, SPN) showing task-specificity during SP1. For SP2, the differences were located centrally in 500-900 ms, the period that reflects the superimposition of processes generating the early CNV and the late positive complex. Task-specific differences appeared only in SP1.

Adult↗