Emotion -Neurophysiology

What is emotion?

The James-Lange TheoryThe physiological changes are emotion, if they are removed, the emotion will go with them.Seems like a backward idea

The Cannon-Bard TheoryEmotional experience can occur independently of emotional expressionEmotions can be experienced even if physiological changes cannon not be sensedThere is not a reliable correlation between the experience of emotion and the physiological state of the body

A comparison of two theories

Neural Basis of Emotion

Limbic Systeman “emotion system” lyingon the medial wall of the brain that links the cortexwith the hypothalamus

the mediator of emotiona flawed and inadequate theory of the emotionalbrain

Neural basis of fear

Fear conditioningA form of Pavlovian(classical) conditioningInvolves the presentation of a noxious unconditioned stimulus(US), at the end of the occurrence of a relatively neutral conditioned stimulus(CS)Studies of fear conditioning have successfully indentified the neural system

Cellular Mechanism Involved in Fear Conditioning

CS-US ConvergencePhysiological Plasticity induced by CS-US pairingLTP and The AmygdalaPharmacological Similarity of LTP and Fear Conditioning

CS-US Convergence

Every cell that responded to auditory stimuli also responded to the US

The lateral nucleus of the amygdala is a site of CS-US convergence

Physiological Plasticity induce by CS-US pairing

Plasticity has been found throughout the fear conditioning circuitry:

-in the auditory thalamic areas-in the auditory cortex-in the lateral, basolateral and central

nuclei of the amygdala.

Plasticity in different locations serves different functions:

-in sensory structures could make stimulus processing more efficient

- in motor systems could make the execution of the responses more efficient

-in the amygdala could represent the integrative aspects of learning

LTP and The Amygdala

LTP ( long-term potentiation )Several properties

- experience dependent and synapse specific- cooperativity- associativity- stable and long lasting

Amygdalacrucial site of conditioningplays a central role in neural circuit of fear conditioning

amygdala

Pharmacological Similarity of LTP and Fear Conditioning LTP does not occur if the NMDA channel

is blocked, the expression of LTP is not affected by NMDA blockade.Blockade of NMDA receptors in the lateral/basal amygdala interferes with the acquisition but not the expression of Pavlovian fear conditioning to a CS or to contextual stimuli

Extinction of Conditioned Fear

Extinction of conditioned fear does not occur passively, but is an active process.

Cortical lesions can interfere with extinction.

Extinction is prolonged by damage to the medial prefrontal cortex.

Conditioned Fear and Instrumental Action

lesions of the amygdala interfere with the acquisition of avoidance responsessepto-hippocampal system is importantamygdala is less important and probably unnecessary for the long-term maintenance of well-trained avoidance responses the instrumental aspects of avoidance may require connections between the amygdala and the ventral striatum for their acquisition and expression

Implication of the Neural Basis of Fear for Understanding Emotion

Cognitive-emotional interactions

Conscious versus unconscious processes in emotion

Volitional control emotion

Cognitive-emotional interactions

Dependence of emotional processing (appraisal) on cognitionIf cognition is defined broadly, emotional processing by the amygdala is highly dependent on cognitive processing.If cognitive processing is defined narrowly, emotion is not necessarily dependent on prior cognitive processing .

Emotional influences on cognition

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amygdala influences on cortical cognitive processing

SENSORY CORTEX

(PRIMARY)

SENSORY CORTEX

(ASSOCIATION)

PERIRHINAL CORTEX

HIPPOCAMPAL FORMATION

N.BASAUS

AMYGDALA

Is emotional processing cognitive processing?

? ? ?

Early pioneers of cognitive science did not view emotion as a cognitive

Appraisal involves information processing. Therefore emotion is cognition

Conscious VS Unconscious Processes in Emotion

fear from running away

or

run from the bear out of fear (conscious emotion)

Volitional Control Emotion

Emotional respondents-effortless and automatic-are controlled by unconscious appraisalprocesses

-include behavioral and visceral responses-are not learned

Emotional operant-are learned through instrumental conditioning procedure

Conclusion

Although the focus on fear conditioning has its limits, it has proven valuable as a research strategy and can help us see emotions in a different light.