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Prestimulation-induced modulation of the P300 component of event related potentials accompanying startle in children
M Sugawara1, M Sadeghpour, J De Traversay
1Department of Psychology, Iwate National University, Morioka, Japan.
Insights
Prestimulation affects the P300 brainwave similarly to the startle blink reflex. This suggests that brainstem mechanisms, rather than higher cortical evaluation, primarily modulate early sensory processing.
Area of Science:
- Neuroscience
- Cognitive Neuroscience
- Psychophysiology
Background:
- The P300 event-related potential (ERP) is typically observed during cognitive tasks.
- Loud auditory stimuli elicit P300 with similar latency and scalp distribution, even in non-task contexts.
- The startle blink reflex is modulated by prestimulation, but its effect on the P300 is less understood.
Purpose of the Study:
- To investigate if inhibitory and facilitatory prestimulation affect the P300 similarly to the startle blink.
- To determine the influence of specific prestimulation intervals on P300 amplitude and latency.
Main Methods:
- EEG recordings were obtained from 93 boys (including those with ADHD and/or enuresis).
- Participants underwent three prestimulation conditions: 4000 msec sustained tone (facilitation), 120 msec interval (inhibition), and 60 msec interval (latency facilitation).
- Repeated measures analyses of variance were used to analyze startle and P300 responses.
Main Results:
- A 4000 msec tone facilitated both startle and P300 amplitude.
- A 120 msec prestimulation interval inhibited both startle and P300 amplitude.
- A 60 msec prestimulation interval facilitated startle onset latency and P300 peak latency (shorter latencies).
Conclusions:
- Non-startling prestimulation modulates the vertex-recorded P300 elicited by startling stimuli, mirroring startle blink modulation.
- This suggests that brainstem inhibitory pathways influence P300, indicating a
- bottom-up
- sensory processing mode.
- The P300 in this context appears to follow startle modulation rules, not task-based cortical evaluation.
Abstract:
Positive EEG deflections with the latency and scalp distribution of the P300 accompany startle in response to loud auditory stimuli in a non-task context. The purpose of this investigation is to determine if inhibitory and facilitatory prestimulation would have effects on the P300 similar to those on the startle blink. Prestimulation conditions were chosen to induce startle amplitude facilitation (4000 msec sustained tone), startle amplitude inhibition (120 msec prestimulation interval), and startle onset latency facilitation (60 msec prestimulation interval). Ninety-three boys (including normals and those with ADHD and/or enuresis) from a startle modulation study had EEG recordings of sufficient quality to provide data for the current study. Repeated measures analyses of variance demonstrated startle amplitude and P300 amplitude facilitation following the 4000 msec tone, startle amplitude and P300 amplitude inhibition following the 120 msec prestimulation interval, and startle onset latency and P300 peak latency facilitation (shorter latencies) following the 60 msec prestimulation interval. Hence, the vertex-recorded P300 elicited by startling stimuli was modulated by non-startling prestimulation in a manner that paralleled that of modulation of the brain-stem generated startle blink. Startle inhibition by prestimulation is mediated by an inhibitory pathway in the mesopontine lateral tegmentum. This brain-stem circuitry has a similar effect on the P300 even though the latter may be generated in more rostral structures. Alternatively, this automatically elicited P300 may represent a limbic or cortical reflection of the sensory processing taking place in the brain-stem. Either interpretation suggests a "bottom-up" as contrasted with a "top-down" mode of sensory processing. This P300 obeys the rules of startle modulation by brain-stem mechanisms rather than indexing cortical evaluation of stimuli for task relevance, stimulus probability, and prior uncertainty.