* Dr Vicky Payne’s excellent blogs here –
* Although the information provided in this article is for dog owners, it is also relevant for cat owners. Additional information for cat owners can also be found at the following ICC resources -
What is fear?
A definition of fear is ‘a normal, appropriate and graded response of an organism to a potentially harmful stimulus’. Fear is a primitive, but complex state consisting of several clearly defined components including (1) a reflexive, defensive behaviour (so called ‘fight/flight’), (2) an emotional/feeling state, (3) a physiological state leading to physical arousal, mental alertness and the release of ‘stress hormones’ through the hypothalamic-pituitary-adrenal axis (HPA), the neuroendocrine complex responsible for the ‘stress’ response (LeDoux, 1996; COAPE, 2013).
Of all the emotional (feeling) states, good and bad, we humans and other animals can experience, fear has been THE most studied of them all by a long way (Panksepp 2005). The reason for this is a simple one; within the world-wide human population up to 30% (one in three) of us will suffer an anxiety disorder of some sort at some time in our lifetimes (McManus, 2007). The numbers coming back from pet behaviour councillors suggest that up to 20% (one in five) of the dogs they see have behaviour problems related to fear, including noise, separation, people, other dogs, handling, places, car travel etc. (Blackwell et al.; 2013, Wan et al., 2012).
Figure 1 is a schematic of how the brain processes sensory information, a sound in this case, but the process is the same for other stimuli such as light and touch.
It is worth noting here that this is the basic plan for all mammals and probably some other classes of animals too. To see how all this works, let’s look at an example of a dog’s experience of a compound stimulus such as a firework going off. After the incoming sound and light flash have been collected and converted into nerve impulses via the ears and eyes they are conducted to the thalamus, which is the brain’s primary ‘switchboard’ for all sensory data. The thalamus then relays this information to the respective areas of the cerebral cortex. The cerebral cortex is divided into separate areas for sound, vision, kinaesthetic (touch, pressure, hot cold) sensations etc. and these areas are where much of memory is stored. The job of the cerebral cortex is to compare each component of this new sensory event (the sound and the light flash along with other details of the dog’s surroundings at the time) with past information of similar bangs, flashes and surroundings the dog has stored as memories. The cerebral cortex then come up with a representation of what has just been experienced and it is at this point that the dog actually becomes aware of the firework exploding. This is when the dog is able to choose an appropriate (operant) behaviour.
However, this is only half of the story.
At the same time as relaying the sensory information to the cerebral cortex, the thalamus also relays it to the amygdala, a small structure deep inside the brain. This route to the amygdala from the thalamus is much faster than the route to the cerebral cortex so the amygdala starts processing first. The amygdala is the storehouse for emotionally charged memories and is specifically involved in the processing of information about primary reinforcers and punishers. In fact, the amygdala is the first part of the brain’s memory systems to develop and begins storing emotional memories as rough blue prints very early on in life, even before other areas such as the hippocampus and the cerebral cortex are functionally mature. It is interesting to note here that humans continue to use the amygdala as a primary processor of much information right up to early adulthood – one reason why teens are so emotional and moody! Furthermore, amygdala memory is primitive and unconscious and in humans it would appear that some traumatic events early in an infant’s life, before they have words for or rational thoughts about their experiences, can re-emerge as confusing and disturbing emotional ‘feelings’ later in life.
Back to our dog!
Like the cerebral cortex, the amygdala compares the data it has received with stored information of past events. The method of comparison is associative – when one key element of the current experience appears similar to some past event, the amygdala can call this a match, even though the current experience may be only slightly similar. The amygdala then triggers the same emotions (feelings) and behavioural response (along with the periaqueductal grey) it learned during the previous event, even though this may now be out of date and inappropriate. However, in a real emergency, the amygdala’s rapid response, activation of FIGHT-FLIGHT etc. could be a matter of life or death “The Difference Between The Quick and the Dead”. All this happens long before the cerebral cortex has finished processing its copy of the setting-off-of-the-firework event and long before the dog is even consciously aware of it! (for more details see LeDoux, 1996; Panksepp, 1998).
As you can see in Figure 1 the prefrontal cortex has connections running between the cerebral cortex and the amygdala. What the prefrontal cortex does is to take the information given to it by the amygdala and the cerebral cortex about an incoming event and then it negotiates between them in order to decide the best course of action. Essentially, its job is to modulate, override and inhibit inappropriate and out of date responses coming from the amygdala.
When we work with a fearful dog and, through counter-conditioning and desensitisation, teach him not to be frightened of something, what we are actually doing is reprogramming his prefrontal cortex to over-ride the old fear response generated in the amygdala. The prefrontal cortex then needs to over-ride the amygdala response every time the dog encounters that fearful situation again in the future – this is an active, not a passive process.
Evolution has shaped the brain in such a way that the fast and dirty amygdala response to life’s events works alongside the slow and detailed response of the cerebral cortex to keep an organism healthy and able to reproduce, but out of trouble when necessary (LeDoux, 1996). Figure 2 is a plate from Charles Darwin's The Expression of the Emotions in Man and Animals, published in 1872, showing the emotion of fear.
For wild animals that are, on the whole, able to freely move around in the environments in which they evolved, this setup works reasonably well.
This is not the case for dogs though. They have to put up with living along-side us in often really complex and diverse human environments, with all its technology, work schedules, festivals, rituals, celebrations, dramas and tragedies.
Everyone knows that during the critical phases of development puppies begin to react fearfully to novel stimuli, hence the importance of breeders implementing a robust ‘stress immunisation programme’ for their puppies (Coppinger and Coppinger, 2001; Scott and Fuller, 1965) (Also see the Kennel Club / Dog’s Trust Puppy Plan for more details http://www.thepuppyplan.com). But actually, the wiring up of the sensory processing circuits (see Figure 1) starts even earlier than this.
Nature – Nurture.
Some breeds / types of dogs are more reactive than others and we know this is inherited; good breeders try to avoid rearing puppies with these traits. On the other hand we also know that a dog’s reactive sensitivity to stressors can also be influenced by its prenatal and neonatal environment, including the emotional wellbeing of the dam.
Another important structure not shown in Figure 1, but vital for the formation of new memories, is the hippocampus.
What the hippocampus does is to take new, incoming sensory information and knit its various auditory, visual, kinaesthetic etc. components together (a process called consolidation) before passing them back to the cerebral cortex for storage. Storing memories this way allows a dog to remember relationships between the different elements of his memories such as the order in which they occurred and the context. The hippocampus also consolidates emotional memory prior to its storage in the amygdala, and it is particularly sensitive to aversive experiences. The hippocampus facilitates the learning of conditioned fear, and importantly packages up other contextual cues, such as elements of the surroundings that can also become conditioned stimuli, before consolidating the memory in the amygdala.
This explains why conditioned fear to a specific event generalises so readily.
The upshot of all this is that prenatal stress can cause damage to several areas of the brain including the amygdala and the hippocampus resulting in increased sensitivity of the HPA and overall fearfulness later in life. Inevitably therefore, some dogs start out in life with a brain already prewired to develop fear-related behaviour problems. (For a full discussion see Adee Schoona and Berntsenb, 2011; Battaglia, 2009; Braastad, 1998; Brunton and Russell, 2010; BSAVA, 2009; Duffy and Serpell, 2009; Gazzanoa, 2008; Gregory, 2004; Haussmann et al., 2011; Jia et al., 2010; Kapoor et al., 2006; Kapoor and Matthews, 2011; Leroy et al., 2009; Lord, 2012; Maccari et al., 2003; Martínez-Téllez et al., 2009; Möhler et al., 2006; Mychasiuk et al, 2012; Phillips, 2002; Rice et al., 2007; Vallée et al., 1997; Volodina, 2012; Weinstock, 2008; Welberg and Seckl, 2013; Yang et al., 2006; Yeh et al., 2012).
In Part 2 of this 4-part blog, we continue by taking a close look at anxiety, an abnormal and maladaptive response that becomes a serious behaviour problem for many dogs, and some cats too.
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Images used in this article
1. Schematic of how the brain processes sensory information. Copyright © COAPE, 2017.
2. Plate VII from Charles Darwin's The Expression of the Emotions in Man and Animals showing Fear. By Unknown; Guillaume Duchenne [Public domain], via Wikimedia Commons.
Available with the publication of the final part of this 4-part series of articles.