Lecture 4: Emotions & Neurophysiology

What is Neurophysiology?

It studies the interaction between the brain and body through the nervous system

The nervous system consists of:

• Central nervous system – the brain and the spinal chord
• Ganglion cells - cells that connect peripheral with central nervous system
• Peripheral nervous system - Nerves connecting organs, muscles & spinal cord

Acetylcholine (Ach):

• Neurotransmitter (transmits signals from cell to cell)
• Located in:
  • central nervous system, acting as a neuromodulator (most abundant neurotransmitter)
  • peripheral nervous system to activate muscles
• Transmits signals between motor nerves and skeletal muscles
• Alterations in the receptors found in: Parkinson and Alzheimer's diseases, schizophrenia, depression, epilepsy, diabetes, respiration disorders, some immunological disorders
• Nicotine exerts its biological effects through nicotinic acetylcholine receptors. In ex-smokers, nicotinic receptors take over a month to normalize.

Autonomic nervous system:

• Composed by the sympathetic and parasympathetic nervous system
• Sympathetic: fight or flight
• Parasympathetic: rest and digest
• Artery: only sympathetic
• Bladder: controlled by both systems. There is inhibition from the frontal lobe, but the limbic-system takes over when scared

Physiological example measures:

• Pupillometry
• Skin Conductance (Galvanic, electrodermal)
• Heart rate, Variability (HRV, IBI)
• Blood pressure (systolic, diastolic)
• Startle response, blinks (EMG)
• Respiration

Why study physiology in neuroscience and psychology?

• to understand how the brain controls the body (and vice versa)
• because physiological signals may serve as objective measures of cognition & emotion

Unconscious body effect

• Test strength of visual masks on subjective (was there a spider?) and objective measures (SCR) in phobic persons
• Unconscious stimuli can alter physiological response

Emotions & Physiology

The eyes

• Salient contrast between pupil, iris, and sclera (eye white) suggests purpose
• Both sympathetic and parasympathetic
• The iris has two muscles: the sphincter pupillae (decreases pupil size) and the dilator pupillae (increases pupil size)
• With the constriction of the pupils, acetylcholine is released
• With the dilation of pupils noradrenaline/norepinephrine is released
• What dilated pupils could mean – something stimulating:
  • “I’m interested in what’s happening”
  • “I’m attracted to something”
  • “I have confidence”…
• What constricted pupils could mean:
  • “I’m bored”
  • “My mind is not working very hard”
  • “I’m disgusted”…

Skin conductance

• Skin resistance changes because of sympathetic activation of endocrine sweat glands
• A patient with impaired amygdala has no skin conductance response to a conditioned stimulus, but he/she does for an unconditioned stimulus
• Skin conductance response increases with fear, anger, or sexual arousal
• Skin conductance response differs for left and right hand (lateralization)

Heart rate variability

• Heart is innervated by both parasympathetic and sympathetic systems
• Acceleration in heart rate leads to release of noradrenaline/norepinephrine
• Deceleration in heart rate leads to release of Acetylcholine
• Fast changes in heart rate are induced by the parasympathetic system
• Slow changes in heart rate by sympathetic
• Incoherent heart rate rhythm pattern means stressful attitudes and emotions, like anxiety
• Coherent heart rate rhythm pattern means positive attitudes and emotions, like appreciation

Temperature

• Functional infrared thermal imaging is non-invasive, and can measure perspiration, cutaneous and subcutaneous temperature variations, blood flow, cardiac pulse, as well as metabolic breathing patterns 
• Two biological mechanisms enable thermal observation of affective nature: subcutaneous vasoconstriction (see the blue nose) and emotional sweating (similar to SCR measure)

Emotions and muscles

• Physiological advantages for the expresser – the wrinkled nose prevents inspiration of potentially harmful particles – are enhanced when the movements are made early.
• Not all facial muscles appear simultaneously during facial expressions, but develop over time supporting a hierarchical biologically-basic to socially-specific information over time.
• Response of muscles in face occur in two stages:

• Early -->approach vs. avoidance (Evolution)
• Late -->  distinguish six “cognitively-controlled” emotions