Emotions and biophysiology Seminar 3

Today’s questions How does the brain create emotions? (Or does it?) Note: There are other similar questions, e.g., what are the emotional networks (“neural pathways”) in the brain, how does the body contribute to emotional experiences, etc. But I will not cover these. If you want to learn about these, take “Affective Neuroscience”

Golden rules about brains in psychology Every psychological process involves the brain Philosophers may disagree (dualist vs. materialist) The question is, what does “involve” really mean? When you read brain articles on emotion, always ask: are the experiments performed on humans or animals? Very often, articles don’t make it clear whether the particular conclusion is derived from animals or human research. A general rule is, when it is overly specific, it probably is from animal studies.

How can you tell whether research is from animals or humans? Here’s a general heuristic Overly specific – from animal models General – from human models

Example During fear conditioning, the conditioned stimulus (CS) and unconditioned stimulus (US) are relayed to the lateral nucleus of the amygdala (LA) from thalamic and cortical regions of the auditory and somatosensory systems, respectively. As shown in Fig. 3, the CS inputs enter the dorsal subregion of the LA, where interactions with the US induce plasticity in two functional cell types (so-called 'trigger' and 'storage' cells). CS information is then transmitted through further stations in the LA to the central nucleus of the amygdala (CE). Interactions between the lateral and central amygdala are more complex than illustrated, and involve local-circuit connections (see main text). The LA also communicates with the CE by way of connections with other amygdala regions (not shown), but the direct pathway seems to be sufficient to mediate fear conditioning. CG, central grey; LH, lateral hypothalamus; PVN, paraventricular hypothalamus. Medina et al. Parallels between cerebellum- and amygdala-dependent conditioning. Nat Neurosci Rev.

Why is this heuristic generally true? The AMG has many layers. FMRI (for humans) does not have such a fine spatial resolution to distinguish Lat AMG vs. Central AMG activation. Only single cell recordings can do that, and that is unethical to do in humans

Part 1 The “emotional” brain

The limbic system A collection of structures thought to be involved in emotion processes Limbic structures: olfactory bulbs, hippocampus, hypothalamus, amygdala, anterior thalamic nuclei, fornix, columns of fornix, mammillary body, septum pellucidum, habenular commissure, cingulate gyrus, parahippocampal gyrus, limbic cortex, and limbic midbrain areas. A concept that is often found in many readings

Image from Wikipedia

Does the limbic system exist? Some neuroscientists (Annette Schirmer, Joseph LeDoux) oppose the limbic system concept altogether For a system to exist, there must be a demarcation of its boundaries System :: Boundaries Countries :: Borders

Does the limbic system exist? Grounded mainly in historical concepts of brain anatomy that are no longer accepted as accurate What boundaries are we talking about? Neuroanatomical? Functional? Cell shape, cell content, projections patterns?

The concept of boundaries In politics Geographical borders Non-distinct Distinct Functional India EU, NATO, etc. Present-day Syria India, Pakistan, etc. In brains Neuroanatomical Non-distinct Distinct Functional Unified system ? Separate system

Does the limbic system exist? If emotion depends on cognition (in neocortex) which depends on hippocampus (in “limbic” system), where is the boundary of the limbic system? The boundaries are so unclear such that one can say the whole brain is the limbic system (Remember a general principle of science: “something that explains everything explains nothing”) Nevertheless, many people still use the term – it is imprecise, but useful (?)

Moving on from the limbic system Part 2 Moving on from the limbic system

9 years ago, I learnt these: Fear  Amygdala (AMG) Disgust  Anterior insular Anger  Orbital frontal cortex (OFC) Sadness  Anterior cingulate cortext (ACC)

Two views about brains  emotions Locationist view: discrete emotions originate from specific brain regions Constructionist models: discrete emotions are constructed of general brain networks Lindquist et al. (2015). The brain basis of emotion: A meta-analytic review. Brain Beh Sci.

Locationist view A particular emotion is consistently and specifically associated with an increased activity in a brain region

Pictorially, this is what it means Fear AMG Or this: Fear AMG1 AMG2 AMG3 But not this: Fear AMG V1 OFC

It also implies… AMG Fear But not this AMG Fear Disgust Sadness

Evidence for locationist view for Fear-AMG Rats: Electrical stimulation of AMG  startle response Humans: Fear-conditioned tones  AMG activation AMG lesions  impaired ability to perceive fear expressions (in voice, face, etc.) Clinical anxiety associated with hyperactive AMG

Problem 1: AMG is activated in many non-fear situations The AMG is activated in the processing of fear, happy, sad, and angry facial expression What do all these faces have in common? They signal ambiguity in the environment.

Problem 2: AMG is not always activated during fear Most fMRI experiments manipulate fear by exposing participants to fear-inducing stimuli, e.g. snakes, fear facial expressions, etc. When people are asked to recall fearful situations, AMG activation is absent Damasio et al. (2000). Subcortical and cortical brain activity during the feeling of self-generated emotions. Nature Neuroscience.

Problem 3: What does “involve” mean? Processing of fearful stimuli ≠ phenomenological experience of fear When you say a brain is “involved” in fear, what do you mean? “Involve” = causes one to experience fear? [causality] = is an outcome of fear? [correlation] Damasio et al. (2000). Subcortical and cortical brain activity during the feeling of self-generated emotions. Nature Neuroscience.

How do you reconcile the findings claiming fear  AMG? Current thinking is that AMG plays a vigilance monitoring role. Vigilance for…possible threat. Evidence AMG neurons are active when stimuli is Novel Unusual Unpredictable Whalen. (1998). Fear, vigilance, and ambiguity: Initial neuroimaging studies of the human amygdala. Curr Dir Psychol Sci.

Let’s look at another example: disgust-insula Evidence for locationist view for disgust-insula Neurodegenerative diseases affecting insula (Huntington’s/Parkinson’s)  diminished disgust response to foul odors  less accurate perception of disgust facial expressions

Problems with the locationist disgust-insula view Fear, sadness, happiness also activates insula - perhaps less strongly Visceral sensations (gastric distention, orgasm, etc.) also activate insula activation Lane et al. (1997). Neuroanatomical correlates of happiness, sadness, and disgust. Am J Psychiatry Wager (2002). Functional neuroanatomy of emotion: A meta-analysis of emotion activation studies in PET and fMRI. NeuroImage Craig (2009). How do you feel — now? The anterior insula and human awareness. Nat Rev Neuroscience.

So what does the insula do? Interoception – awareness of bodily states

We can go on and on… Fear  Amygdala (AMG) Disgust  Anterior insular Anger  Orbital frontal cortex (OFC) Sadness  Anterior cingulate cortext (ACC)

But there is a more general problem We can only examine a few “classical” emotions. What about other emotions? (We will examine jealousy on Thurs) Even if the locationist view could be correct, you would need x brain areas for x emotions So if there is a culture that doesn’t experience emotion k, people of this culture don’t have brain area k?

But here’s the constructionist view Emotions are constructed from various pieces of information that the brain receives This information can originate from somatosensory organs (e.g., body, vision, odors) Or from self-generated events (e.g., appraisals)

Part 3 Unsolved mysteries

Mystery 1 Constructionist models (see similar terms e.g., “binding problem”) suggests that there is a specific region where things come together (“constructed”). But where is this place? Does this place exist? Do you need this place?

Mystery 2 Emotion research using biophysiological methods often use visual stimuli Faces (greyscale, with hair remove) IAPS (may be gray scale or not, which actually also affects the measurement) Are you studying emotion processing, emotional experiences, or…?

Choice of stimuli Choice of stimuli to induce emotion also depends on the dependent variable (recall Week 1 L2) EEG: Good temporal resolution, poor spatial resolution fMRI: Good spatial resolution, poor temporal resolution HR, SCR: …

Ultimate mystery for neuroscience https://www.youtube.com/watch?v=C5DfnIjZPGw (9:19)

Take home messages Limbic system is probably a wrong concept Locationist view of emotions is probably wrong. The hard problem is intractable. Does it mean affective neuroscience is worthless? NO!