PowerPoint Slideshow about 'Emotion and the Brain' - waldemar
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In 1937, Kluver and Bucy identified that animals that had large lesions to their temporal lobe produced a behavioural syndrome that is best characterized as ‘psychic blindness’: An inability to apprehend the motivational or emotional significance of stimuli or events in their environment although they were capable of processing the sensory properties of stimuli.
No manifestation of fear in situations that would normally be expected to elicit fear.
Hyper-orality– any object… even ate their own feces
Sexual deviant behaviour: attempted to copulate with animals who were members of other species
Infantile amnesia: we have little conscious / episodic / declarative memory of the first two years of life (what is your first memory?)
Jacobs and Nadel (1985) argue that the inability to recall memories in early childhood reflects the delayed maturation of the hippocampus (18 to 36 months in humans, while amygdala is mostly developed in embryo).
Memory codes laid down prior to the development of the hippocampus use codes that are indecipherable to the hippocampus or linguistic / symbolic systems.
In contrast, most of the amygdala’s neurons are fully developed earlier in embryonic stages and are fully present at birth.
Thus, the amygdala may be particularly important in early learning and the establishment of affective memories prior to the maturation of cognitive functions mediated by the hippocampus.
Parallel between infantile memories and fear/phobia learning in adults in which stress hormones are released which interfere with the development of long term potentiation in the hippocampus and thus the establishment of memory traces.
Thought questions association cortices before reaching the hippocampus, relative to the amygdala
How do the different routes for transmission of information to the amygdala (which generates emotional responses and is the structure responsible for emotional learning) help to resolve the dispute between Zajonc and Lazarus?
The amygdala is reciprocally connected to many of the structures previous mentioned that are involved in higher cognitive processing. What is the implication of this observation for other theories we have studied in the class so far?
Emotional perception is represented more in the posterior areas of the cerebral cortex, and expression and experience more in the anterior regions.
With that said, there are two basic theories of the laterality of emotional processes within the brain: One that assumes right hemisphere superiority for all emotional processing, and one that divides hemispheric specialization according to valence.
The right hemisphere of the brain seems to be specialized for emotional expression: in most right handed individuals facial expressions are more salient on the left side of the face.
Patients with RH damage have difficulty recognizing facial expressions of emotion
Split Brain patients: sever the corpus callosum: can recognize emotionally salient events when presented to the LVF. E.g. Gazzaniga (1988) showed SB patients a film of a person being thrown on to a fire to their LVF. The patient could not describe what it was they saw, but could not verbally describe what it was they saw since language depends on LH function. However, the patient reported feeling scared and jumpy and nervous, which they attributed to the presence of the experimenter or the room.
Limbic system and the right hemisphere do not operate in terms of symbolic linguistic representation, yet cross-hemispheric connections do exist (e.g., anterior commissure)
Thus, information about the general emotional tone of the scene was conveyed to the left hemisphere, which could verbalize a general feeling of anxiety/uneasiness.
This example is interesting given our previous readings about cognitive labeling theories of emotion: The experience set up an evaluative need that was then attributed to situational cues (the room, the experimenter).
Chimeric Faces scene did not reach the LH, but the processing of the fear-related stimulus probably involved limbic system structures that are below the level of the severed callosum.
Right Hemisphere => perceiving emotion scene did not reach the LH, but the processing of the fear-related stimulus probably involved limbic system structures that are below the level of the severed callosum.
When normals are shown a ‘Chimeric face’, they most often report that the face with the lip upturned on the right side (left from the viewer’s perspective) looks more happy, and the face with right lip turned downwards looks more sad.
When pictures are flashed briefly with unilateral visual field presentation, recognition of emotional expressions is better for faces presented in the left visual field.
Tucker & Frederick (1989) have noted that the right cerebral cortex has closer connections with the amygdala than the left cerebral cortex.
Emotional Experience scene did not reach the LH, but the processing of the fear-related stimulus probably involved limbic system structures that are below the level of the severed callosum.
The Valence hypothesis: Emotional experience is lateralized in the cerebral cortex
Left hemisphere is specialized for the experience of positive emotion, and the right hemisphere is specialized for the experience of negative emotion.
Davidson’s variation of the Valence hypothesis posits that approach / withdrawal tendencies are a precursor to the laterality of emotional experience by valence.
Lateralization of responses is thought to represent an effective means of reducing competitive interactions between these two fundamental response processes.
LeDoux’s Research Program / Rationale scene did not reach the LH, but the processing of the fear-related stimulus probably involved limbic system structures that are below the level of the severed callosum.
Evidence from brain damaged patients:
Left frontal lesions are associated with a catastrophic/depressive reaction
Right frontal lesions are associated with an indifferent/euphoric reaction
Robinson (1984): patients who suffered left hemisphere strokes were more likely to suffer from depression than those with right hemisphere strokes.
Effect stronger when lesion was closer to the frontal pole
Studies of the behaviour of brain damaged individuals thought to reflect the functioning of intact hemisphere.
Depressed individuals show decrease in left frontal activation, as measured by EEG
Left frontal hypoactivation and hypometabolism in depressed individuals as measured by PET and SPECT especially in the anterior cingulate gyrus
Bench et al. (1996) showed that this asymmetry resolved upon successful antidepressant therapy
Wada Test result of not differentiating between: anterior versus posterior; emotional perception, expression, and experience; or to take into account a stress-diathesis model (lesion represents vulnerability)
Wada Test: Unilateral injection of Sodium Amytal into the carotid artery: functional hemispherectomy
Preoperative assessment of language and memory function in individuals who are candidates to receive psychosurgery for intractable temporal lobe epilepsy
Left side injection = anesthetization of the left hemisphere, resulting in observation of the function of the right hemisphere… catastrophic depressive reaction characterized by crying, pessimism, worries of the future, and guilt.
Right side injection = euphoric reaction characterized by a lack of apprehension, smiling, laughing, optimism, and a sense of well-being.
Consistent with brain-damage results.
Evidence from non-clinical populations result of not differentiating between: anterior versus posterior; emotional perception, expression, and experience; or to take into account a stress-diathesis model (lesion represents vulnerability)
Diamond and colleagues (1976) used special contact lenses to present different types of emotionally salient films: pleasant, humorous, unpleasant, or horrific.
Films presented to the right hemisphere (LVF) were rated as more horrific and unpleasant than the same films presented to the left hemisphere (RVF).
Wittling and Pfluger (1993) found that right hemisphere presentation of unpleasant films was related to an increase in salivary cortisol levels (stress response).
EEG studies result of not differentiating between: anterior versus posterior; emotional perception, expression, and experience; or to take into account a stress-diathesis model (lesion represents vulnerability)
Davidson et al. (1990) had participants watch positive and negative film clips and took unobtrusive video recordings of their facial expressions.
Expressions of disgust, were associated with greater right frontal activation, while expressions of happiness were associated with greater left frontal activation.
Also, remember the results from the assigned reading (Duchenne smile paper): Duchenne smiling was associated with more left-sided anterior temporal and parietal activation than other smiles. Other smiles were associated with more right frontal activity than baseline.
Affective style: Emotionality trait result of not differentiating between: anterior versus posterior; emotional perception, expression, and experience; or to take into account a stress-diathesis model (lesion represents vulnerability)
Personality variable (trait) that results in a propensity to react in positive or negative ways to stimuli and events
Tomarken et al. (1992) found that subjects who sustained an asymmetric pattern of activation over a three-week period reported increased generalized positive affect, and less negative affect compared to those with stable right anterior activity
Wheeler et al. (1993) showed that patterns of sustained asymmetrical cerebral activation (as measured by EEG) predicted reactions to emotionally evocative films.
Greater right frontal activation was associated with reports of more negative affect in response to the negative emotional film clips compared to subjects with stable left frontal activation who reported more intense positive affect to positive film clips.
Unilateral Hemispheric Activation result of not differentiating between: anterior versus posterior; emotional perception, expression, and experience; or to take into account a stress-diathesis model (lesion represents vulnerability)
Schiff and Lamon (1989) showed that contraction of the right hand of face resulted in feelings of aggressive well-being, while contractions of the left hand or face resulted in more negative emotion, as assessed with a semi-clinical interview.
The sensory and motor fibers from the hand and lower 2/3 of the face connect to the contralateral cerebral hemisphere, and thus these results are consistent with the valence hypothesis.
Mainly zygomaticus major contraction. Is this a problem? Why?
A PET investigation showed activation in the contralateral anterior cingulate gyrus two minutes following the cessation of a set of unilateral contractions in an area associated with the motivational and emotional consequences of pain and vibrotactile stimulation.
Mechanism may be the spreading of activation from these regions to those associated with biasing emotional functions (i.e., attention). This is consistent with the observation that the effects of the contractions are usually found with implicit or ambiguous stimuli, not self-report.