Prestimulation-induced modulation of the P300 component of event related potentials accompanying startle in children.
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.
Sugawara
M
M
Department of Psychology, Iwate National University, Morioka, Japan.
Sadeghpour
M
M
De Traversay
J
J
Ornitz
E M
EM
D000161:Acoustic Stimulation; D001289:Attention Deficit Disorder with Hyperactivity / Q000503:physiopathology; D001767:Blinking / Q000502:physiology; D001921:Brain / Q000502:physiology*; D002648:Child; D004569:Electroencephalography; D004576:Electromyography; D004775:Enuresis / Q000503:physiopathology; D005071:Evoked Potentials / Q000502:physiology*; D006801:Humans; D008297:Male; D009132:Muscles / Q000502:physiology; D011930:Reaction Time / Q000502:physiology; D013216:Reflex, Startle / Q000502:physiology*