Startle Amplitude and Fear in an Acoustic Startle Paradigm: Lesions to the Brachium of the Inferior Colliculus or the Lateral Tegmental Tract

In 2 experiments, startle amplitude and startle stimulus-induced freezing (an index of fear) were measured in an acoustic startle response (ASR) paradigm in rats. Lesions to lateral tegmental tract (LTG), a pathway medial to brachium of the inferior colliculus (BIC), significantly decreased freezing...

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Bibliographic Details
Published in:Behavioral neuroscience 2001-04, Vol.115 (2), p.477-492
Main Authors: Leaton, Robert N, Brucato, Frederic H
Format: Article
Language:English
Subjects:
Acoustic Reflex
Anatomical correlates of behavior
Animal
Animal behavior
Animals
Auditory Perception - physiology
Behavioral psychophysiology
Biological and medical sciences
Brain
Brain Mapping
Experiments
Fear
Fear & phobias
Fear - physiology
Fundamental and applied biological sciences. Psychology
Inferior Colliculi - physiology
Inferior Colliculus
Male
Nerve Net - physiology
Neural Inhibition - physiology
Neural Pathways - physiology
Neurology
Psychology. Psychoanalysis. Psychiatry
Psychology. Psychophysiology
Rats
Rats, Long-Evans
Reflex, Startle - physiology
Startle Reflex
Tegmentum Mesencephali - physiology
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Summary:In 2 experiments, startle amplitude and startle stimulus-induced freezing (an index of fear) were measured in an acoustic startle response (ASR) paradigm in rats. Lesions to lateral tegmental tract (LTG), a pathway medial to brachium of the inferior colliculus (BIC), significantly decreased freezing and produced a persistent 5-fold increase in ASR amplitude compared with sham-operated controls. Lesions to BIC increased both ASR amplitude (2-fold) and freezing. Neither BIC nor LTG lesions affected startle amplitude when startle was elicited by a brief footshock stimulus. Characteristics of the lesion effects were tested with manipulations of interstimulus interval, stimulus intensity, and prepulse inhibition. The data suggest (a) an ascending pathway medial to BIC that carries the fear-inducing dimensions of an acoustic stimulus and (b) a descending pathway that provides tonic inhibition of the sensory input to the ASR circuitry.
ISSN:0735-7044
1939-0084
DOI:10.1037/0735-7044.115.2.477