Biomedical subjects

Margot J Taylor

Publications and source records attributed to Margot J Taylor.

3 recordsLinked to original sources

PubMed2003

Developmental changes in distinguishing concurrent auditory objects.

Children have considerable difficulties in identifying speech in noise. In the present study, we examined age-related differences in central auditory functions that are crucial for parsing co-occurring auditory events using behavioral and event-related brain potential measures. Seventeen pre-adolescent children and 17 adults were presented with complex sounds containing multiple harmonics, one of which could be 'mistuned' so that it was no longer an integer multiple of the fundamental. Both children and adults were more likely to report hearing the mistuned harmonic as a separate sound with an increase in mistuning. However, children were less sensitive in detecting mistuning across all levels as revealed by lower d' scores than adults. The perception of two concurrent auditory events was accompanied by a negative wave that peaked at about 160 ms after sound onset. In both age groups, the negative wave, referred to as the 'object-related negativity' (ORN), increased in amplitude with mistuning. The ORN was larger in children than in adults despite a lower d' score. Together, the behavioral and electrophysiological results suggest that concurrent sound segregation is probably adult-like in pre-adolescent children, but that children are inefficient in processing the information following the detection of mistuning. These findings also suggest that processes involved in distinguishing concurrent auditory objects continue to mature during adolescence.

Acoustic Stimulation↗

PubMed2002

Inversion and contrast polarity reversal affect both encoding and recognition processes of unfamiliar faces: a repetition study using ERPs.

Using ERPs in a face recognition task, we investigated whether inversion and contrast reversal, which seem to disrupt different aspects of face configuration, differentially affected encoding and memory for faces. Upright, inverted, and negative (contrast-reversed) unknown faces were either immediately repeated (0-lag) or repeated after 1 intervening face (1-lag). The encoding condition (new) consisted of the first presentation of items correctly recognized in the two repeated conditions. 0-lag faces were recognized better and faster than 1-lag faces. Inverted and negative pictures elicited longer reaction times, lower hit rates, and higher false alarm rates than upright faces. ERP analyses revealed that negative and inverted faces affected both early (encoding) and late (recognition) stages of face processing. Early components (N170, VPP) were delayed and enhanced by both inversion and contrast reversal which also affected P1 and P2 components. Amplitudes were higher for inverted faces at frontal and parietal sites from 350 to 600 ms. Priming effects were seen at encoding stages, revealed by shorter latencies and smaller amplitudes of N170 for repeated stimuli, which did not differ depending on face type. Repeated faces yielded more positive amplitudes than new faces from 250 to 450 ms frontally and from 400 to 600 ms parietally. However, ERP differences revealed that the magnitude of this repetition effect was smaller for negative and inverted than upright faces at 0-lag but not at 1-lag condition. Thus, face encoding and recognition processes were affected by inversion and contrast-reversal differently.

Brain↗

PubMed2002

Non-spatial attentional effects on P1.

OBJECTIVE: It has been suggested that P1, the earliest endogenous visual potential, is influenced primarily by spatial location. However, we have found that attention to non-spatial visual features can affect both the latency and amplitude of this component. METHODS: A series of studies are reviewed, starting with 4 using simple geometric forms, and either serial presentation of single stimuli or presentation of stimulus arrays followed by two studies using natural complex images. RESULTS: With simple stimuli, latency and amplitude effects are seen on the P1, but differ among the paradigms, depending on the demands of the task. The data further showed a facilitation effect and that binding occurs in parallel with single feature processing. For complex stimuli we found P1 shorter to faces than inverted faces, eyes or non-face stimuli, and larger to animal than non-animal pictures. The above effects were present in children as well as in adults. CONCLUSIONS: These findings demonstrate that very early stages of processing can be modified by top-down attentional influences across a range of ages and experimental paradigms, concordant with visual processing models showing very rapid and dispersed activation with feedback at early cortical levels.

Age Factors↗