Indelibility of Subcortical Emotional Memories Joseph E. LeDoux Lizabeth Romanski Andrew Xagorasis Laboratory of Neurobiology Cornell University Medical College Summarized by Shauna Overgaard

Ivan Pavlov Conditioned Reflexes Conditioned Stimulus (CS) Conditioned Stimulus (CS) Unconditioned Stimulus (US) Classical Conditioning Unconditioned Stimulus (US) Classical Conditioning

LeDoux et al. 1984,1985,1986,1987, 1988 Classical conditioning is mediated by projections from the thalamus to the amygdala.

Affect Occurs after cognition in a sequential processing chain. or At least some aspect of emotional processing are organized in parallel to cortical functions. At least some aspect of emotional processing are organized in parallel to cortical functions.

Is this Rule or Exception?

Triune Brain Paul MacLean

Question and Findings Q: Is visual fear conditioning, like auditory fear conditioning, mediated subcortically? A: 1.Visual conditioning does not depend upon the integrity of the visual cortex. 2.Emotional memories established in the absence of the visual cortex persisted (resisted extinction) for unusually long periods of time.

Locations of Auditory and Visual Cortices

Auditory Pathway Nolte, The Human Brain: An Introduction to its Functional Anatomy, 5th Ed

The pathway of electric signals on the optic nerve to the visual cortex.

Typical Lesion of Visual Cortex LeDoux, J, Romanski, L, & Xagoraris, A (1989). Indelibility of subcortical emotional memories. Journal of Cognitive Science. 1,

What did LeDoux Do? Four groups of rats were given visual cortex lesions (VC) or sham operation (SH). Twenty days later, rats were given either paired (P) or random (R) presentations of the CS (flashing light) and US (foot shock). SH VC SH VC P n=11 R n=6 P n=10 R n=5

Method Cont. Fear Conditioning: the suppression of drinking by the CS Basal Lick Rate: time elapsed in completing 5 licks upon box entrance and 100 licks before CS presentation. Licking During CS: the difference between the latency to complete 100 licks before and after the onset of the CS.

The difference in time to complete 100 licks before and after the onset of the CS. LeDoux, J, Romanski, L, & Xagoraris, A (1989). Indelibility of subcortical emotional memories. Journal of Cognitive Science. 1,

Results Visual Cortex lesions did not interfere with acquisition: - With onset of the CS, SH and VC given P training stopped drinking. - SH and VC given R training continued drinking. - SH and VC given R training continued drinking. Visual fear conditioning is mediated by subcortical sensory pathways.

Results Cont. With each administration of the extinction test the CS suppressed licking less in the sham operated group than in the visual cortex lesioned group. The performance of the lesioned group, did not change significantly over the course of 5 tests. LeDoux, J, Romanski, L, & Xagoraris, A (1989). Indelibility of subcortical emotional memories. Journal of Cognitive Science. 1,

Results Cont. Extinction was greatly prolonged, if not prevented, by cortical ablation.

Why no extinction? Amygdala: Performs primary role of formation and storage/processing and memory of emotional reactions. Thalamus:

Implications Lesions of visual cortex may prolong extinction by preventing the relay of visual inputs to areas such as the frontal cortex and/or hippocampus. Emotional memories established in the absence of sensory cortex, probably by way of thalamo-amygdala projections, are relatively indelible. Emotional behavior may extinguish, but the underlying association is not lost.