Motivation and emotion

Motivation

Purposeful, goal-directed behaviour

Emotion

Cognitive interpretation of subjective feelings

Behaviour

Reflects neural activity, sensory needs, evolutionary influences and environmental learning

Sensory deprivation

Illustrates that the brain seeks stimulation

Innate releasing mechanisms (IRMs)

Inborn triggers for adaptive responses that support survival, feeding, escape and reproduction

·      E.g. kittens react defensively to a threatening cat posture

Environmental influences

·      Skinner: consequences shape behaviour and reinforcement increases the likelihood that a behaviour will recur

·      Learned taste aversion: food taste becomes associated with subsequent illness which changes later food choice

Regulatory vs non-regulatory behaviour

Homeostasis

Maintaining essential bodily variables within a narrow range

Key neural circuits in motivation

1.        Hypothalamus/pituitary

2.        Limbic system

3.        Frontal lobes

Limbic and frontal regions together

Project to the hypothalamus - linking emotional significance and cognitive control with bodily responses

Hypothalamus

·      Links nervous and endocrine systems via pituitary

·      Influences hormone release, circadian rhythms, food intake, fear, defence and sexual behaviour

·      Different hypothalamic stimulation sites evoke different goal-directed responses

·      Communicates with pituitary via neural connections and releasing hormones carried in blood

·      Endocrine output is influenced by feedback loops, neural input and experience

Hypothalamic regions

1.        Lateral

2.        Medial

3.        Periventricular

Medial forebrain bundle (MFB)

Connects brainstem/limbic systems with forebrain regions and contributes to motivated behaviours including eating, sex and addiction

Feedback loops

Regulate when neural activity or hormone release starts/stops

·      E.g. suckling → tactile input → hypothalamic oxytocin release → milk let-down

·      Experience can alter hypothalamic neurons

·      Oxytocin-producing cells enlarge during lactation

Limbic system

·      Interconnected structures including amygdala, hippocampal formation and cingulate cortex

·      Connections to hypothalamus coordinate emotion, memory, motivation and physiological responses

Frontal cortex

·      Reasoning, planning and self-control shape whether and how motivated behaviour is expressed

·      Orbitofrontal regions participate in food-related decisions

Eating

·      Both homeostatic and rewarding

·      Hypothalamic signals interact with digestive information, cognitive expectations, learned associations and dopamine-mediated reward

Thinking about food

·      Activate reward systems and increase hunger

-              Larned taste aversion can reduce consumption

·      Amygdala and orbital prefrontal cortex influence food preference

-              Amygdala damage can abolish taste-aversion learning

Clinical associations

·      Obesity research considers DLPFC-related self-control and dopamine responses

·      Anorexia nervosa research links food choices with dorsal striatum and frontostriatal habit circuits

Drinking

Regulatory behaviour associated with hypothalamic homeostatic control

Gonodal hormones

·      Developmental gonadal hormones influence differentiation of sex-related neural circuits

·      Adult gonadal hormones influence sexual behaviour

-              In rats, ovarian hormone changes are linked with changes in hippocampal dendritic spines

Sexual behaviour structures

Mesolimbic pathway

Dopaminergic projections begin in the ventral tegmental area (VTA) of midbrain and involve nucleus accumbens, amygdala, hippocampus and medial prefrontal regions

·      Linked to reward and pleasure

Olds and Milner (1954)

Rats repeatedly pressed a lever for electrical stimulation of particular brain sites - demonstrating strong reinforcement by brain stimulation

Wanting

Incentive motivation to obtain a reward

Liking

Pleasure/evaluation when receiving it

 

**Both usually co-occur but can dissociate and involve partly separable systems

Limbic system

Interconnected brain structures involved in emotion, motivation and memory.

·       Structures: Amygdala, hippocampus, cingulate cortex and hypothalamus

·       Integrates emotional and motivational information to influence behaviour

·       Communicates with the prefrontal cortex and hypothalamus to coordinate behavioural and physiological responses

Amygdala

Bilateral groups of nuclei deep in medial temporal lobes involved in fear, anxiety, anger, emotional memories and decisions

·      Stimulation evokes fear and aggression

·      Connections to hypothalamus and prefrontal cortex link emotion with bodily responses and regulation

Emotion

1.        Autonomic responses: heart rate, hypothalamus

2.        Subjective feelings: fear, amygdala/frontal regions

3.        Cognitions: interpretations in cerebral cortex

James–Lange account

Bodily/autonomic changes occur first and the brain interprets these as emotion

Somatic marker hypothesis

Emotion-related bodily signals guide decisions

·      Spinal cord injury may blunt reported emotional intensity

-              Higher lesions are described as having greater effect

·      Supports a contribution of bodily feedback

Bilateral amygdala damage

Reduced fear, hyperorality, hyperphagia, hypersexuality and memory difficulties