Impulse Related Aggression A Neurological & Behavioural Review

Understanding Impulse Control Disorders That Relate To Aggression

Dogs commonly exhibit anxiety related disorders. The common disorders which are related to anxiety are often associated with aggression and fear aggression. Dogs who are aggressive through fear will want to increase the distance between the trigger(s) and themselves with the motivating operation to reduce fear. You will often see a fearful animal withdraw whilst he is giving threats and they will only be aggressive when they have no other option. They may chase from behind, those they fear and nip them when they have the opportunity. Impulse control related aggression is different. It used to be called dominance aggression. We no longer use dominance based techniques in understanding behaviour, for many reasons, but mainly, because it does not have much clinical use in identifying and treating the problem see: Dogs Are Not Pack Animals.

Dogs have evolved through a domestication process which means that their behaviour has adjusted accordingly. Domesticated dogs now have a much larger window in their critical periods, please see Evolution Domestication & Cognition- The Biology Of Dogs

Dominance Aggression (outdated): 

“The disposition of an individual to assert control in dealing with others. Animal Behavior. high status in a social group, usually acquired as the result of aggression, that involves the tendency to take priority in access to limited resources, as food, mates, or space”Impulse Control Aggression (the current expression): By Mayo Clinic Staff. Intermittent explosive disorder involves repeated, sudden episodes of impulsive, aggressive, violent behavior or angry verbal outbursts in which you react grossly out of proportion to the situation.

Identification Of Impulse Control Aggression 

Dogs that display impulse related aggression will not withdraw from the social situation. They seem to seek them out and approach the object of concern. This is a distance decreasing task. They appear to have a compulsion towards this behaviour. The impulsive behaviour is often characterised as abnormal, out of context and disproportionate to the situation. This will be exhibited towards anyone who tries to passively or actively control the behaviour. If the dog intensifies his response when any passive or active correction or interruption of the behaviour occurs with confirm this diagnosis. The difference between this and fearfully aggressive dogs who act out of context is that these dogs initiate this interaction and it may be towards a human that is not the focus and the reaction is inappropriate given the human behaviour that seemed to bring about this behaviour.

It may seem that the behaviour comes out of nowhere and unrelated to the current context. Impulse related aggression is a paradox. Rather than finding out more information from the context and getting information from the environment which could help them to remain calm, they act in a way that actually increases their anxiety. Impulsive behaviours appear to have an element of pleasure. The purpose of the behaviour could be to increase arousal but there is often a compulsive component to it and the organism generally engages in the behaviour to decrease this conflict of internal and external conflict. This is often an attempt to decrease the dysphoria. So the compulsion of the behaviour is an attempt to alleviate anxiety but the impulse is directed by the desire to obtain the pleasure from arousal. There is an inability to inhibit or delay these behaviours. As this behaviour is practiced the impulses become compulsive and the compulsive behaviours can become impulsive or reinforced as some kind of habit.

We have developed the essential trainers resource pack for vets, professionals, rescues etc which contains information/schedules to educate dog owners on how to recognise, treat and prevent behaviour problems (there are over 25 posters and handouts now plus a free children colouring book and word quiz): Essential Training Resource Guide

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Factors That Relate To Impulse Control Aggression

The frequency of impulse control aggression has been somewhat reduced by people not breeding from lines that appear to be affected by this trait. This is why it is so important for people to choose a good breeder and to make sure you can see both parents. People often talk about Cocker rage, this is thought to be related to a genetic disorder which is a characteristic in the red cocker’s. It was apparent in show type red and some black cocker’s. There is little evidence (if any) on this condition but it has been bred out by selective breeding. Some texts suggest it is due to an increased expression of dopamine which could implicate that this is a genetically inherited condition.

The contributing factors are genes, sex, endocrine, neurological and environmental. The impulsive and compulsive aspects of behaviour seem to have some neurological component. This seems to be related to inhibitory neurotransmitters eg Serotonin and GABA (gamma aminobutyric acid). Also the excitatory neurotransmitters norepinephrine, glutamate and dopamine. There is also evidence which suggests that there is a dysfunction of the limbic and prefrontal cortex (the areas that interplay in regulation of complex cognitive functioning, emotions and behaviours). Without corticol control there is striatal overdrive (a group of brain structures involved in movement, cognition, eye movement and voluntary movement it also receives input from thalamic regions, substantia nigra, amygdala and hippocampus). Increased activity in the frontal lobe is thought to characterise the compulsion and decreased frontal activity characterises the impulsive brain activity (hyper and hypo respectively).

Dogs who display this type of condition seem to struggle with their caregivers because of their need to control all aspects of the environment. This is not because the dogs are being dominant or aggressive. It is due to the fact that they get their essential environmental information from these types of interactions. They seem unable to take the cues about the environment by sitting back and observing. They are unable to distance themselves from things that concern them. Most people have not done anything to have caused such behaviour. The reactions seem to depend on the relationships and his threshold for activity. The key is to understand the behavioural patterns which will mean that his behaviour becomes less unpredictable. It is important that we do not blur the lines between dogs that are confident and are just being assertive. These dogs will read environmental cues and be able to demonstrate some control over their impulses. If the behaviour is disproportionate, out of context and “abnormal” then it is likely to be impulse control related aggression.

A dog that displays this type of impulse control aggression will often exhibit threatening type behaviours if there is a threat to his immediate social context. He will use aggressive activities (such as grabbing, mouthing and biting) in order to get information from the apparent changes in social context. He will not understand how these behaviours are being received by you. It is important to recognise all social triggers no matter how subtle they seem so that they can be aborted. These dogs get a response from their behaviour by provoking and getting responses to their behaviour. Dr Karen Overall defines two types of impulsive behaviours, one that is truly impulsive and the other is when the dog becomes more impulsive when his attempts at addressing his own anxiety by controlling people’s actions fail. 

A great webinar series worth watching is from Dog-Ibox Series Donna Hill. This gives some great tips and ideas to help attenuate this as a potential problem using positive reinforcement training.

For some dogs, the rule structure that you have in place is causing the pathology and sometimes this is harming the dog. This is because he is trying a set of rules and his anxiety makes more sense of the situation. Instead we need to teach him more about what will happen next.

Treatment for this type of disorder is often difficult and certainly in humans it has been difficult to standardise. Interventions can occur at symptom or behavioural level. These are aimed at reducing impulse and compulsivity. The behavioural strategies seem to be the most effective for long-term treatment. Predominantly applied behaviour (or ABA).

Biological Factors Relating To Impulse Aggression

We cannot escape from the fact that all animals have an inborn response tendency towards a limited suite of behavioural strategies. The cortical areas of the brain help to modulate the more primitive responses. We need to understand these mechanisms and the more primitive limbic system to help understand how the modulation of aggression occurs. Please see our brand new course on Emotional Contagion & Empathy, The Neural Mechanisms & Evidence In Dog Behaviour

Applied Behaviour Analysis (ABA) looks at how the organism’s behaviour is functionally related to his environment.  It is often said that ABA does not consider the emotional state of the animal. Well, it does! We need to understand how the animals neural and hormonal systems play a role in mediated the functions of those relationships. Using ABA techniques it is possible to show how the function of cognitive capacities integrates with the mechanisms explained when looking at neural systems. The analysis of function is like a sketch of the mechanisms and then when you add the mechanisms you are able to integrate it with the levels of explanations available to you. Here is a brief outline of the brain regions and what they do. Below, there is an image of a brain and its regions to help you visualise this.

  • Prefrontal cortex (PFC) Orbital OPFC and the ventromedial VMPFC- Inhibit limbic regions responsible for aggression (cortex areas not identified on schematic below)
  • The anterior cingulate cortex is thought to be involved in evaluating stimuli and its utility relating to response of the individual.
  • Amygdala responds to threatening or charged stimuli
  • The brain regions work together in a network or connectome and they signal to other nodes in the system such as the hypothalamus.
  • The hypothalamus is involved in initiating motor action & modulating hormonal systems
  • Impulse control aggression is characterised by an unstable affect modulation and then this triggers a cascade of responses to the perceived provocation.
  • This article is useful and is part of our puppy instructor course: Somatosensory Development, The Psychobiological Substrates Of Attachment & Learning In The Critical Period.

Images from: Brain Hack PFC who have a brilliant explanation on this subject.

FrontalRegions 1-s2.0-S0890856712000433-gr1


The Neurotransmission System

The system that has received most study is the serotonin (neuromodulator) system. The main finding is that the cerebrospinal fluid (CSF) has lower concentrations of 5-hydroxyindole acetic acid (5-HIAA). This is a serotonin metabolite and this is common in patients with violent behaviour (Asberg et al 1976)

  • The serotonin systems modulates inhibitory areas in PFC
  • The serotonin system modulates inhibitory areas in anterior cingulate cortex (ACC)
  • The PFC and ACC have been reported as the  areas important in modulating aggression
  • Example case study of Phineas Gage who had damage to his OFC and VMFC and could not inhibit his aggression and social judgment.
  • New et al 1998 showed that damage to frontal temporal regions leads to irritability and angry outbursts
  • Evidence shows that any impairment or reduction in the PFC inhibition or the excitatory circuits in areas such as amygdala is associated with aggression
  • Reduced gray matter Raine et al 2000 associated with autonomic deficits and aggression
  • Decrease blood flow and glucose metabolism in PFC associated with aggression
  • New et al 2002 suggested that there is a disconnection between the inhibitory and limbic systems involved in aggression generation and this is responsible for the disinhibition of aggression.
  • This could be related to low serotonin activity which modulates the PFC and the over activation of the limbic system.
  • Serotonin effects PFC via the 5HT2A receptors. These increased PFC activity by innervating the inhibitory interneurons (Mann et al 1992)
  • This leads to an upregulation (through DNA transcription factors) of the 5-HT2 receptor. It was suggested by Siever et al 2002 that there was an increase binding to this receptor and that was found in patients with impulse related externally directed aggression. The pathophysiology of this system could use more characterisation. To find out seminars on the Neuroscience Of Behaviour Seminars
What About Catecholamines?

The role of dopamine, noradrenaline and growth hormone have all been implicated in the facilitation of aggressive behaviour. This area is not as well studied as the serotonin system.

Here is a brief summary:
  • The receptors involved in noradrenaline and dopamine systems have been implicated in aggressive behaviour
  • A reduction in the presynaptic concentrations of their biological substrates and the sensitivity of the post synapses could be a factor in irritability and stress
  • Growth hormone and its response to clonidine (a drug used to treat high blood pressure and anxiety) has been positively correlated with irritability
  • These articles look at the neuroscience of resilience Neural Mechanisms Of Resilience & Its Role In Dog Training
Hormones & Related Elements (HRE)

Vasopressin is a hormone which acts on the retention of water by the kidneys and  it increases blood pressure. It also plays an important role in memory and behaviour. CSF and VP are positively correlated in aggression. Using an antagonist has been shown to decrease aggression.

Steroids such as testosterone and cholesterol (a sterol type compound) have been linked to aggression. Low cholesterol is linked with aggression in humans and primates. The sex hormones are modulators important in helping animals build resilience to stress and moderating learning (plasticity). Oxytocin, frequently called the “love” hormone, is responsible for bonding and is also implicated in aggression, particularly in females.

Impulse control aggression in dogs is frequently found in male dogs but it is thought not to be related to testosterone. In dogs, impulse control aggression seems to be prevalent around social maturity about 18-24 months to 12-36 months. This is why it can appear suddenly. Hormones may affect this condition but they do not cause it (it is suggested that low concentrations of testosterone could be a factor).  When female dogs are affected it is often younger, around 8 months and it is thought that the factors related are in utero.

Aggression is modulated by monoamines, neuropeptides and neurosteroids.  Please see the following article Neuroscience Of Puppy Development What Happens In This Critical Period Of Brain Development 

If you want to set your puppy up with the right start, please see our 7 Day Puppy Survival Guide (owner/enthusiast/professional) & if you want to instruct classes we have developed a 10 week instructor course: Puppy Training Classes Instructor Course.

Genes & Impulse Control Aggression

There is some degree of genetic accountability which determines this type of disorder. There is no gene identified to code for aggression. GWAS (genome wide association studies) determined that there were no correlations between specific gene sequences and aggression per se. It is highly likely that we will need to look at the endophenotype and then work backwards to get a more accurate answer. A genome wide project is being carried out on canines and some exciting developments have already taken place. For example, a gene sequence has been identified for AMS (acral mutilation syndrome), which is a rare autosomal recessive genetic disorder of the sensory neuropathy of dogs and results in considerable damage to their extremities. With selective breeding we have already been successful in ruling out these behaviour characteristics and by genetic testing (of the AMS related gene) we should be able to rule this out too. Another reason why it is important to buy from a breeder who health tests their dogs.

Genetic related factors which contribute to aggressive behaviour:
  • Polymorphisms in the genes responsible for regulation of neuromodulators like serotonin could be inherited
  • Genes for the structural organisation of brain regions that are implicated in aggression could be inherited
  • MAO (monoamine oxidase-A) alteration to this gene is linked to impulse aggression
  • Genetic variant of MAO gene is thought to alter the catecholamine metabolism
  • Polymorphisms in serotonin related genes are often linked with aggression

Behavioural modification techniques look to provide alternative ways of channeling the impulses generated in this condition. By looking at the motivating operations, understanding the interplay between psychobiological substrates, neurobiological factors, as well as the environmental triggers, it is possible to treat these conditions.

Helping the organism to employ better coping strategies through environmental predictability and consistency reduces the need for conflict. The current research into the understanding and neurobiological aspects of aggression are going to hold the key to possible prevention and treatment.  

The brain depends on an interplay between many interacting factors to help it mature. Experience dependant processes which are genetically driven need less specific environmental stimulation. In the case of impulse control aggression (in dogs) the primary goal should be to identify his triggers, arrange his environmental antecedents, work with a veterinary behaviourist (See BVBA) to identify any pain related or medical treatment needed. 

Ultimately, it is necessary to work with suitably qualified professionals to help draw up a suitably tailored treatment plan along with appropriate protocols to help his environment become more predictable and thus decreasing his need to aggress.

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References For This Article:

Evenden JL. Varieties of impulsivity. Psychopharmacology (Berl). 1999

Moeller G, Barratt ES, Dougherty DM, et al. Psychiatric aspects of impulsivity.

Grant JE, Potenza MN. Compulsive aspects of impulse-control disorders

Stein DJ, Trestman RL, Mitropoulou V, et al. Impulsivity and serotonergic function in compulsive personality disorder. J Neuropsychiatry Clin Neurosci. 1996

Fineberg NA, Hollander E, Potenza M, et al. Probing compulsive and impulsive behaviours, from animal models to endophenotypes

Hollander E, Rosen J. Impulsivity. J Psychopharmacol. 2000

Coccaro EF. Impulsive aggression: a behavior in search of clinical definition. Harv Res Psychiatry 1998

Stein, DJ, Harvey B, Seedat S, Hollander E. Treatment of impulse-control disorders 2006

Hollander E, Berlin HA. Neuropsychiatric aspects of aggression and impulse-control disorders 2008

Hollander E, Baker BR, Kahn J, et al. Conceptualizing and assessing 2006

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