Neuropsychology of expression perception:Neuropsychology of expression perception:

What brain structures are involved in emotional processing?

What facial information is used to recognise expression?

Illustrations are copyright of Carter, R. (1998) "Mapping the Mind", Weidenfeld & Nicolson; and J.G. Csernansky, John Hopkins Centre for Imaging Science.

Subcortical structures involved in emotional processing:

Cingulate gyrus

Basal ganglia:

Striatum: Caudate nucleus + putamen

Globus pallidus

Limbic "system":

Hypothalamus, hippocampus, anterior thalamus, cingulate cortex, mamillary body, amygdala.

Globus pallidus

Subcortical structures:

Amygdala - involved in learning emotional significance of information, and in providing an instinctive, emotional response. Damage in animals produces Kluver-Bucy syndrome (hypersexuality, hyperorality, lack of fear responses).

Hippocampus - involved in memory; provides contextual information for interpreting a stimulus' emotional significance.

Hypothalamus - physiological responses (fright or flight).

Anterior cingulate - integrates evaluation of emotional experience with episodic memory.

Cortical structures involved in emotion perception:

medial

Frontal lobes’ connections to other brain regions:

Damasio (1985):

“Understanding the prefrontal lobe depends upon knowledge of the company it keeps, that is its afferent and efferent connections”.

What facial information is used to encode expression?

Etcoff and Magee (1992), Calder et al (1996):

Emotion perception of morphed faces shows categorical perception effects.

Calder, Young, Keane and Dean (2000) :

Anger, fear and sadness are more easily recognised from top half of the face.

Happiness and disgust are more easily recognised from the bottom half.

Surprise is equally recognisable from both top and bottom halves.

Ekman and Friesen (1976):

6 basic emotions recognised cross-culturally, each expression produced by distinct musculatures.

Happiness

Surprise

Disgust

Fear

Sadness

Anger

Problems : posed facial expressions

(a) are easier to recognize than genuine expressions.

(b) lack all of the "facial action units" in genuine expressions.

(c) are less symmetrical (review in Davis and Gibson 2000).

The Composite Effect and expression perception:

Identification of expresssion of upper face half is slower with (a) (aligned happy) than (b) (misaligned happy); and faster with (c) (the veridical angry face) than (d) (misaligned angry).

Effects disappear with inversion.

Expression perception involves first-order configural processing.

Recognition and expression perception are largely independent (expression judgements for composites are unaffected by their component faces' identities, and vice versa).

Individual features have a role to play too.

Calder, Young, Keane and Dean (2000), White (2000):

Same composite effects as with recognition, suggesting expression perception involves configural processing.

Laterality differences in emotional processing:

Left hemisphere Right hemisphere

Speech production and comprehension

Linguistic prosody Affective prosody

Prefrontal damage

catastrophic reaction

"la belle indifference"; euphoria, anosognosia

Evaluation of emotion (linking it to verbal meaning)

Experience of emotion

Facial expression

Left side of face (controlled by RH) is more expressive.

Greater L than R prefrontal cortical activity -> positive affect

Greater R than L prefrontal cortical activity -> negative affect.

Hemispheric differences in emotional processing?

Three views -

(a) RH dominance theories: RH dominant for processing all emotional signals (Bowers, Bauer and Heilman 1993).

(b) “Valence" theories: LH and RH make qualitatively different contributions: e.g. negative vs positive valence (Dilberman and Weingartner 1986), or approach vs avoidance/withdrawal tendencies (Davidson 1992).

(c) Independent basic emotions (e.g. anger, fear, disgust, etc.) are supported by different brain regions (compatible with a or b).

Hemispheric differences in emotional processing?

Silberman and Weingartner (1986): RH and LH lesions lead to impaired evaluation of negative and positive valence emotions respectively.

Davidson (1993): EEG in normal subjects during behaviour shows more activity in left- and right-anterior regions for approach-related (e.g. happiness) and avoidance-related (e.g. fear or disgust) expressions respectively.

Anderson et al (2001):

Most research suggests global RH specialisation for evaluation and generation of facial expressions. But, also evidence that LH and RH make distinct contributions to emotional communication.

Alves et al (2009):

Left visual field bias for happiness and fear, RVF bias for neutral faces.

Bourne, 2009:LVF bias (RH) for all six emotions.Strength of lateralisation varied across different emotions - positive emotions more strongly lateralised than negative emotions.

Role of individual brain structures in emotional processing:

Evidence that different emotions are supported by individual brain structures:

Adolphs et al (1994, 1995), Calder et al (1996), Scott et al (1997), Broks et al (1998), Sprengelmeyer et al (1999): bilateral amygdala lesions impair perception of facial expressions of fear.

Breiter et al (1996), Morris et al (1996): neuroimaging studies show amygdala is activated during presentations of fearful expressions.

Philips et al (1997), Calder et al (2001), Krolak-Salmon et al (2003): insula is important for recognition of disgust.

Role of the amygdala in emotional processing:

Anderson et al (2001):

Compared facial expression ratings for 6 basic emotions, in R and L anterior temporal lobectomy patients and normal controls.

Evaluation of avoidance/withdrawal expressions (esp. fear) was impaired by right lobectomy, but not by left lobectomy.

Suggests RH is generally associated with processing emotions associated with avoidance/withdrawal.

Within RH, areas are specialised for processing specific related (negative) emotions.

This specialisation is both cortical and subcortical.

Amygdala is more responsive to facial expressions than to non-facial social stimuli (Adolphs and Tranel 2003):

Scenes shown for each emotion, with and without faces. Patients with bilateral amygdala damage

(a) benefited less from inclusion of faces than did other groups,

(b) were better at identifying anger in face-absent scenes, than in face-present scenes (vice versa for brain-damaged controls).

Bilateral amygdala patients often mistook anger for smiles.

(+ve score = face aided interpretation)

Effects of ageing on expression perception (Calder et al 2003):

Recognition accuracy for Ekman and Friesen photos.

Five age-groups, 20-70.

Linear decrease in recognising fear and sadness; some improvement in recognising disgust.

Decrease in fear recognition perhaps related to (normal) age-related changes in temporal lobe (amygdala/hippocampus).

Insula (underlies disgust perception) shows fewer age-changes.

Basal ganglia and emotion perception:

Basal ganglia are extensively connected with prefrontal and limbic cortical areas as well as motor cortex.

BG lesions affect cognition and emotion processing, as well as motor behaviour.

Sprengelmeyer et al (2003): untreated Parkinson's Disease patients worse than treated PD patients on tests of expression perception (even though latter's PD was more advanced).

Dujardin et al (2004): compared early untreated PD patients and healthy controls, on rating subtle facial expressions, tests of executive function, visuospatial perception, depression and anxiety.

PD patients significantly impaired in decoding expressions (angry, sad and disgusted) and in executive function.

In PD, nigrostriatal dopaminergic depletion leads not only to motor and cognitive disturbances but also to emotional information processing deficits.

Ventral striatum and anger perception (Calder et al 2004):

Three groups, various tests (including Ekman pictures...):

Normal controls.

VS group: four patients with damage to ventral striatum (ventral caudate, ventral putamen, and nucleus accumbens) 3 LH damage, one RH damage.

BG group: three patients with damage to more dorsal basal ganglia.

VS group specifically impaired on recognising (and experiencing) anger.

Total number of impairments (relative to controls) on 4 tests of emotion recognition

Ventral striatum and emotion perception (Lawrence et al 2002):

Administered sulpiride (a dopamine D2-class receptor antagonist) to healthy males.

Selectively disrupted recognition of facial expressions of anger; preserved recognition of other emotions.

D2 receptors are localised in the ventral striatum - hence implies this region is involved in anger perception.

(NB: Parkinson's Disease disrupts other receptor families too including D1–D5 receptors - may explain why Dujardin et al (2004) observed more widespread impairment of emotion perception in PD patients).

Conclusions:

Overall, evidence supports RH dominance hypothesis; but also different components of the limbic system play important roles in emotional processing -

amygdala - fear perception;

ventral striatum - anger perception;

insula - disgust perception.