8.pdf

08 February 2024 15:57 Notes Main Ideas Cognitive + affective neuroscience Cognition = thoughts, perceptions, awareness, mental actions Affect = feelings, emotions, moods, attitudes What are emotions? Not easily defined Emotions refer to the combination of ○ (1) physiological responses ○ (2) changes...

08 February 2024 15:57 Notes Main Ideas Cognitive + affective neuroscience Cognition = thoughts, perceptions, awareness, mental actions Affect = feelings, emotions, moods, attitudes What are emotions? Not easily defined Emotions refer to the combination of ○ (1) physiological responses ○ (2) changes in behaviour ○ (3) subjective feelings. Emotions are immediate responses to specific objects or situations; moods are diffuse and long-lasting emotional states. Emotions allow humans (and other animals) to adapt and react to events of biological and/or personal significance Notes Role of the amygdala S.M.’s deficits suggest a critical role of the amygdala in fear processing. May support discrete theories of emotions. Deficits not because S.M. does not have emotions. ○ Deficits specific to fear; other emotions are felt. Deficits also not because S.M. does not know what fear is. ○ Able to describe situations that elicit fear. ○ Experienced fearful situations herself (e.g., vicious dog during childhood, criminal attacks). S.M does recognise fear S.M. can detect briefly presented fearful faces, just like controls, despite not having amygdala Experiment: press left/right button according to the location of the emotional face Discrimination ability S.M's ability to detect location of the emotional face was within the normal range for fear, anger and threat Classification of emotions Categorial theories ○ Small set (4-9) of basic emotions that are discrete, innate and universal. ○ Usually anger, disgust, fear, happiness, sadness and surprise. ○ Differ from more complex emotions that are learned and shaped by context Dimensional theories Dimensional theories contrast with categorical theories. According to such theories, emotions are points in a complex space formed of continuous dimensions. The dimensions are usually arousal (intensity of emotion) and valence (relative pleasantness). Implications The amygdala not needed for fast, unconscious fear detection. Goes against the idea of a ‘low road’ subcortical pathway for processing emotions involving the amygdala. However, fMRI and other work does support a role of the amygdala in unconscious emotional processing Affective blindsight Stroke patient with bilateral damage to primary visual cortex. Able to correctly guess which emotion is displayed on faces shown to blind fields (unconscious emotion perception). Increased fMRI activity in right amygdala for emotional faces relative to neutral faces, especially fear Patient S.M First described in 1994 Full bilateral amygdala lesion due to a genetic disorder (Urbach-Wiethe disease). Amygdala: Complex, densely connected subcortical structure with multiple nuclei. Role of amygdala unresolved Are the amygdala associated with unconscious or conscious fear processing? S.M.’s brain may have re-organised since illness, learned fear during childhood, or have atypical performance. The existence of multiple (amygdala) emotion pathways in humans and other animals is debated Need evidence from multiple sources Recognising face expressions When asked to rate expressions on a 0 (not at all) to 5 (very much) scale, S.M. recognizes happy, surprised, angry, disgust, and sad expressions. But specific deficit in recognizing fearful expressions Time course of the amygdala Single neuron recordings in epilepsy patients indicate relatively late visual processing in the amygdala Notes Amygdala revisited Amygdala responses may not be automatic but reflect higher-level processing. When instructed to pay attention to eyes, S.M. becomes normal at recognising fearful faces (Adolphs et al., 2005, Nature). The amygdala also respond to positive stimuli and arousal (e.g. Ball et al., 2009, Journal of Neuroscience Methods). The amygdala may play a broad role in emotions and be important for detecting salience and relevance of events Evidence for salience When searching for face-house pairs (T1-T2), detection is better when houses are salient (carry the prospect of shock). The larger fMRI activity is in right amygdala, the more likely salient pairs are detected Beyond the amygdala In addition to the amygdala, other brain regions contribute to the processing of emotions. These include the limbic system, midbrain regions, medial temporal lobe and prefrontal cortex Prefrontal cortex Damage to the prefrontal cortex (e.g., Phineas Gage) can lead to changes in personality and emotions. Damasio’s somatic marker hypothesis. - Emotions guide behaviour and decision making. - Emotions lead to somatic markers which are processed in ventromedial prefrontal cortex. The prefrontal cortex has a regulatory role in emotion. - May send bias signals to other regions to guide behaviour and achieve goals Amygdala in healthy people In controls, fmri responses in the amygdala to fearful faces depend on awareness Amygdala originally linked to fear, but likely plays a more general role in emotional processing (e.g., salience). Emotions also rely on other brain regions, notably the prefrontal cortex. There is no one-to-one mapping between specific emotions and specific brain regions. Still unclear whether categorical or dimensional theories best describe emotions. PSYC0031 Cognitive Neuroscience Page 1 Multivariate analysis Are mental proce Univariate fMRI analy Univariate analys Multivariate fMRI ana Multivariate anal Prefrontal amygdala relation The data showed an inverse relationship between activity in prefrontal cortex and activity in the amygdala. Reappraisal may cause the prefrontal cortex to down-regulate activity in emotion-processing systems. Up- and down- regulation In another study, people increased or decreased their emotional response to aversive scenes. More prefrontal activity in both cases; more amygdala activity with up-regulation and less with down-regulation. Suggests a general regulatory role for the prefrontal cortex - positive emotions (“approach”) - and right hemisphere on negative - emotions (“avoidance”). - Based on frontal alpha EEG asymmetries Emotion specificity Question: Do different emotions have unique neural substrates? Some evidence for category-specific brain activity Summary Meta-analyses Inconsistent resu Perhaps univaria Current trend is t Pattern classifica Evidence for cognitive control Participants shown negative and neutral photos. Photos either just had to be attended or reappraised by changing their meaning, followed by a 1-4 (weak-strong) emotion rating. Prefrontal asymmetries Initially, right hemisphere thought to be specialized for processing emotions. - Based on patients with unilateral cortical damage. More recently, valence hypothesis: - Left hemisphere focuses on Drawing face expressions S.M. also shows a specific fear deficit when asked to draw faces from memory Caveat Few studies dire Meta-analyses a Decoding the brain One approach is Then apply this k Decoding emotions Multivariate anal For example: Wa ○ Meta-analy ○ Emotional Liu et al. (2023) Multivariate anal Interactions betw Some common a Discrete or dimensio Brain regions ma Still debated whe ○ Discrete: S ○ Dimension Notes ectly contrast multiple emotion categories. are a solution: integrate data across studies to find consistent patterns of emotion-related brain activity. ults and no simple one-to-one mapping between a given brain structure and given emotion. ate, localisation-focused fMRI analyses do not provide the correct level of explanation? to employ multivariate computations to assess large-scale brain networks that underlie emotions. ation analyses. approach esses represented in groups of voxels rather than individual voxels? yses ses average activity across voxels alyses lyses identify consistency in activity patterns s to identify activity patterns that differentiate conditions (classifiers). knowledge: assess which classifier occurs on a trial to predict the condition lyses suggest that activation patterns, rather than discrete brain regions, are related to emotions ager et al. (2015), PLoS Computational Biology ysis across 148 studies to identify classifiers that differentiate anger, disgust, fear, happiness and sadness. categories distributed across distinct brain systems rather than single regions lyses used to examine functional connectivity patterns of six basic emotions. ween distributed brain regions found to explain facial expression recognition. areas (e.g., occipital cortex, fusiform gyrus); others specific (e.g., amygdala for fear). onal? ay process different aspects of an emotion rather than specific emotions. ether activation patterns are best explained by discrete or dimensional emotion theories. For example: Saarimäki et al. (2016), Cerebral Cortex. al: Bush et al. (2018), Scientific Reports PSYC0031 Cognitive Neuroscience Page 2