NEUROSCI 101 Lecture Notes - Lecture 9: Parahippocampal Gyrus, Lingual Gyrus, Fusiform Gyrus

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17 May 2016
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Weekly Paper:
Herz et. al (2004): Neuroimaging evidence for the emotional potency of odor-evoked memories
1. Emotional odor affected the amygdala and hippocampus.
2. Herz et al (2004) administered the odors to subjects using an olfactometer.
3. Herz et al. used control odor, control visual stimulus, experimental visual stimulus and
an air puff as controls to prove that odor had the largest emotional influence on memory.
Methods:
participants: 5 healthy R-handed females subjects who identified a positive, personal
memory about a perfume
● fMRI:
experimental odor (EO): 5 specific perfume identified by each subject
control odor (CO): generic perfume
experimental visual (EV): color photographs of experimental perfumes
control visual (CV): color photographs of control perfume
higher activation in the medial temporal lobe (amygdala, hippocampus, parahippocampal
gyrus) and decreased activation in lingual gyrus, fusiform gyrus and middle occipital
gyrus when presented with EO as compared to CO/EV/CV
increased activation in parahippocampual gyrus and amygdala and in thalamus and
cerebellum in EO compared to CO
air puff is given if subject is at a resting state (not responding to stimuli/goal driven
behaviors/not thinking about anything), but after the puff they might be thinking “oh my,
that Chanel No. 1 smells amazing”
Improvements:
subjective experience of an odor memory is more emotional than alternate sensations
(visions)
emotional responses plotted on arousal vs valence, but in this study they only
measure arousal
skin tests can also measure emotional responses (ie in lie detectors)
rather than presenting a visual stimulus of the perfume bottle, researchers could
have given subjects specific images of the situation in which they were wearing
this perfume (ie restaurant they went on a bad date with, or workplace
environment), but this may introduce more confounding variables since each
person’s situation is different
very small sample size, researchers denounced insignificant results as “false”
since there weren’t enough participants and the ones that agreed with the study
as “true”
priming was used at the very start: “give me an odor you recognize, and give me
the specific memory associated with it” - thinking ONLY of this and not natural
thoughts
could choose both left and right handed participants, since other studies say that
handedness is associated with sensory perception
administer generic pictures to see emotional response, ask them to smell
perfumes, and then ask them if this evoked a specific memory: gets rid of priming
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subjective experience of emotional potency of odor-evoked memory is correlated with
activation in amygdala during recall
Organization of the Olfactory System
three types of olfactory receptor cells detach from the glomerulus down to the nasal
epithelium bone (cribiform bone plate), where they dangle downward to meet odorant
molecules that bind to them
humans have a relatively weak olfactory system, since we have only 80 types of
receptors (we lost 400 over evolution)
pattern separation in the olfactory bulb: receptors have specific categories of
scents they bind well to (ex. sweet/orange/rose, bitter, goat-like)
mature neurons are sufficient to encode familiar features but not novel features, however
young neurons are capable of encoding all inputs
neurogenesis occurs in the olfactory bulb in addition to the hippocampus
“The amygdala but not the hippocampus is involved in pattern separation based
on reward value”: used lower sucrose receptors to discriminate b/w sweet tastes,
lesioning the amygdala interferes with this ability to discriminate b/w sweet tastes
labeled lines: olfactory bulb projects to piniform cortex, which projects directly into
entorhinal cortex of hippocampus, which is connected to the thalamus
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