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The Amygdala, Arousal and Memory: From Lesions to Neuroimaging
Uppsala universitet, Humanistisk-samhällsvetenskapliga vetenskapsområdet, Samhällsvetenskapliga fakulteten, Institutionen för psykologi.
2009 (engelsk)Doktoravhandling, med artikler (Annet vitenskapelig)
Abstract [en]

Emotional events are better remembered than neutral events. But what are the mechanisms behind this memory enhancing effect? It seems that they depend on the arousal level at the moment we experience the event to be remembered.

The first study of the present thesis mapped the brain areas that changed their activity in a highly arousing situation in subjects with snake or spider phobia. Looking at pictures of their feared object engaged the amygdala, situated in the medial temporal lobe. This area has previously been demonstrated to be necessary for fear reactions. Here, the novel question was what other brain areas the amygdala engages when the brain is in a state of high arousal. Results suggest that the amygdala recruits other limbic and cortical areas known to be involved in motor behavior and object recognition. In contrast, when subjects watched fear-relevant but non-phobic pictures, amygdala activity was negatively correlated to the anterior cingulate cortex suggesting cortical inhibition.

The final two studies aimed at explaining the physiological brain mechanisms behind arousal enhancement of memory. In the first one, epileptic patients with medial temporal lobe resections including the amygdala were compared to healthy controls on a recognition memory task where the pictures to be remembered varied in arousal intensities. Results suggested that the anterior medial temporal lobe including the amygdala is necessary for arousal enhancement of memory because the enhancement effect was abolished in resectioned patients.

The last study related inter-individual differences in bodily arousal to amygdala-parahippocampal interaction. Results suggest that the beneficial effects of emotion on memory depend on arousal regulating mechanisms of the amygdala that in turn affects parahippocampal activity.

Collectively, results suggest that the amygdala is regulating changes in arousal states of the brain and body during distressful situations. Further, arousal in turn determines memory strength through gating amygdala influences on the parahippocampal cortex. Thus, the amygdala is a node both in a fear and a memory network and arousal influences the amygdala to prepare for action and to enhance memory. This seems evolutionary sound.

 

sted, utgiver, år, opplag, sider
Uppsala: Acta Universitatis Upsaliensis , 2009. , s. 53
Serie
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Social Sciences, ISSN 1652-9030 ; 48
HSV kategori
Forskningsprogram
Psykologi
Identifikatorer
URN: urn:nbn:se:uu:diva-98978ISBN: 978-91-554-7447-8 (tryckt)OAI: oai:DiVA.org:uu-98978DiVA, id: diva2:201860
Disputas
2009-04-17, Sal X, Universitetshuset, Uppsala, 10:15 (engelsk)
Opponent
Veileder
Tilgjengelig fra: 2009-03-27 Laget: 2009-03-05 Sist oppdatert: 2010-12-09bibliografisk kontrollert
Delarbeid
1. Disentangling the web of fear: amygdala reactivity and functional connectivity in spider and snake phobia
Åpne denne publikasjonen i ny fane eller vindu >>Disentangling the web of fear: amygdala reactivity and functional connectivity in spider and snake phobia
Vise andre…
2009 (engelsk)Inngår i: Psychiatry Research: Neuroimaging, ISSN 0925-4927, E-ISSN 1872-7506, Vol. 172, nr 2, s. 103-108Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

The objective was to study effects of fear on brain activity, functional connectivity and brain-behavior relationships during symptom provocation in subjects with specific phobia. Positron emission tomography (PET) and (15)O water was used to measure regional cerebral blood flow (rCBF) in 16 women phobic of either snakes or spiders but not both. Subjects watched pictures of snakes and spiders serving either as phobic or fear-relevant, but non-phobic, control stimuli depending on phobia type. Presentation of phobic as compared with non-phobic cues was associated with increased activation of the right amygdala and cerebellum as well as the left visual cortex and circumscribed frontal areas. Activity decreased in the prefrontal, orbitofrontal and ventromedial cortices as well as in the primary somatosensory cortex and auditory cortices. Furthermore, amygdala activation correlated positively with the subjective experience of distress. Connectivity analyses of activity in the phobic state revealed increased functional couplings between voxels in the right amygdala and the periamygdaloid area, fusiform gyrus and motor cortex. During non-phobic stimulation, prefrontal activity correlated negatively with amygdala rCBF, suggesting a phobia-related functional decoupling. These results suggest that visually elicited phobic reactions activate object recognition areas and deactivate prefrontal areas involved in cognitive control over emotion-triggering areas like the amygdala, resulting in motor readiness to support fight or flight.

Emneord
Specific phobia, anxiety, fear-circuit, PET, subjective experience
HSV kategori
Identifikatorer
urn:nbn:se:uu:diva-98987 (URN)10.1016/j.pscychresns.2008.11.004 (DOI)000265779800003 ()19321315 (PubMedID)
Tilgjengelig fra: 2009-03-05 Laget: 2009-03-05 Sist oppdatert: 2017-12-13bibliografisk kontrollert
2. Arousal enhanced memory retention is eliminated following temporal lobe resection
Åpne denne publikasjonen i ny fane eller vindu >>Arousal enhanced memory retention is eliminated following temporal lobe resection
2010 (engelsk)Inngår i: Brain and Cognition, ISSN 0278-2626, E-ISSN 1090-2147, Vol. 73, nr 3, s. 176-179Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

The amygdala, situated in the anterior medial temporal lobe (MTL), is involved in the emotional enhancement of memory. The present study evaluated whether anterior MTL-resections attenuated arousal induced memory enhancement for pictures. Also, the effect of MTL-resections on response latencies at retrieval was assessed. Thirty-one patients with unilateral MTL-resections (17 left, 14 right) together with 16 controls participated in a forced choice memory task with pictorial stimuli varying in arousal. Response latencies increased with stimulus arousal in controls but not in patients. This was paralleled by attenuated recognition memory for moderately and highly arousing pictures in MTL-resectioned patients as compared to healthy controls. However, patients and controls did not differ in memory performance for non-arousing pictures. These results suggest that the MTL is necessary for arousal induced memory enhancement.

Emneord
Amygdala, Emotion, IAPS pictures, Medial temporal lobe, Response latency
HSV kategori
Identifikatorer
urn:nbn:se:uu:diva-98986 (URN)10.1016/j.bandc.2010.04.009 (DOI)000280020300004 ()
Tilgjengelig fra: 2009-03-05 Laget: 2009-03-05 Sist oppdatert: 2017-12-13bibliografisk kontrollert
3. Arousal gates amygdala interaction with the parahippocampal cortex during encoding of phobic pictures
Åpne denne publikasjonen i ny fane eller vindu >>Arousal gates amygdala interaction with the parahippocampal cortex during encoding of phobic pictures
Vise andre…
(engelsk)Artikkel i tidsskrift (Annet vitenskapelig) Submitted
Identifikatorer
urn:nbn:se:uu:diva-98991 (URN)
Tilgjengelig fra: 2009-03-05 Laget: 2009-03-05 Sist oppdatert: 2011-01-11bibliografisk kontrollert

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