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Autonomic Response Measurement — JE LeDoux | ReplicateScience

Experiments/Autonomic Response Measurement

Source Paper

Subcortical efferent projections of the medial geniculate nucleus mediate emotional responses conditioned to acoustic stimuli

JE LeDoux, A Sakaguchi, DJ Reis

Journal of Neuroscience • 1984

Autonomic Response Measurement

behavioralratNot specified

Objective: Identify the afferent link in the neural pathway mediating emotional responses to acoustic stimuli by measuring autonomic and behavioral responses to conditioned acoustic stimuli during extinction trials

Materials & Equipment Checklist

5 items

Gather these items before starting the experiment. Check off items as you prepare.

Equipment2

Mean arterial pressure measurement device

Not specified • Not specified • Not specified • Not mentioned

Heart rate measurement device

Not specified • Not specified • Not specified • Not mentioned

Materials3

HRP (Horseradish Peroxidase)

Not specified • Not specified • Not specified • Not mentioned

Electric footshock

Not specified • Not specified • Not specified • Not mentioned

Pure tone acoustic stimulus

Not specified • Not specified • Not specified • Not mentioned

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Protocol Steps

1

Anterograde neuroanatomical tracing

Inject HRP into medial geniculate nucleus (MG) to define the rat auditory cortex through anterograde neuroanatomical tracing studies

Not specifiedNot specified

Note: This step identifies anatomical connections between MG and auditory cortex

View evidence from paper

“The rat auditory cortex was defined through anterograde neuroanatomical tracing studies involving the injection of HRP into MG”

2

Lesion placement

Place lesions in either the auditory cortex, medial geniculate nucleus (MG), or inferior colliculus

Not specifiedNot specified

Note: Different groups received lesions in different brain regions for comparison

View evidence from paper

“Lesions were then placed in the auditory cortex or in MG”

3

Recovery period

Allow rats to recover following lesion placement before behavioral testing

10 to 20 daysNot specified

Note: Recovery period allows for stabilization of lesion effects

View evidence from paper

“After 10 to 20 days the rats were subjected to classical fear conditioning trials”

4

Classical fear conditioning

Conduct classical fear conditioning trials involving the pairing of a pure tone with electric footshock

Not specifiedNot specified

Note: Pure tone serves as conditioned stimulus; electric footshock serves as unconditioned stimulus

View evidence from paper

“the rats were subjected to classical fear conditioning trials involving the pairing of a pure tone with electric footshock”

5

Extinction trials with autonomic measurement

Present the acoustic conditioned emotional stimulus (pure tone) during extinction trials without footshock while measuring mean arterial pressure, heart rate, freezing duration, and drink suppression

Not specifiedNot specified

Note: No footshock is presented during extinction trials; this is when conditioned responses are measured

View evidence from paper

“presentation during extinction trials (no footshock) of the acoustic conditioned emotional stimulus were measured”

6

Measure autonomic responses

Record changes in mean arterial pressure and heart rate elicited by presentation of the acoustic conditioned emotional stimulus

Not specifiedNot specified

Note: Autonomic responses are measured during extinction trials

View evidence from paper

“Changes in mean arterial pressure and heart rate and the duration of immobilization were measured”

7

Measure behavioral responses

Record the duration of immobilization (freezing) and drink suppression elicited by presentation of the acoustic conditioned emotional stimulus

Not specifiedNot specified

Note: Behavioral responses are measured during extinction trials

View evidence from paper

“the duration of immobilization (freezing) and drink suppression elicited by presentation during extinction trials”

View Abstract

The purpose of this study was to identify the afferent link in the neural pathway which mediates emotional responses coupled to auditory stimuli. We evaluated whether autonomic and behavioral responses elicited by acoustic conditioned emotional stimuli are based on afferent information derived from the auditory cortex or from the auditory thalamic relay station, the medial geniculate nucleus (MG), in rats. The rat auditory cortex was defined through anterograde neuroanatomical tracing studies involving the injection of HRP into MG. Lesions were then placed in the auditory cortex or in MG. After 10 to 20 days the rats were subjected to classical fear conditioning trials involving the pairing of a pure tone with electric footshock. Changes in mean arterial pressure and heart rate and the duration of immobilization (“freezing”) and drink suppression elicited by presentation during extinction trials (no footshock) of the acoustic conditioned emotional stimulus were measured. Auditory cortex lesions did not affect the magnitude of the mean arterial pressure or heart rate conditioned responses nor the duration of freezing or drink suppression. In contrast, lesions of MG suppressed the magnitude of both the autonomic and somatomotor (behavioral) conditioned emotional responses but did not affect either autonomic or somatic responses elicited by the footshock unconditioned stimulus. Lesions of the inferior colliculus, the primary source of afferent input to MG, replicated the effects of MG lesions. These findings demonstrate that lesions of MG and lower auditory centers, but not lesions of the auditory cortex, block autonomic and behavioral conditioned emotional responses coupled to acoustic stimuli and indicate that subcortical rather than cortical efferents of MG sustain these responses. Our concurrent observation that MG projects to several subcortical areas (central and lateral amygdala; caudate-putamen; ventromedial hypothalamus) involved in emotional behavior and autonomic function suggests hypotheses concerning subsequent links in this emotional processing pathway.