Barks Blog

Creating new and better associations for dogs on leash when exposed to fearful/stressful stimuli is crucial, as it is better for all involved for the dog to be less stressed and less fearful. The goal is potentially a positive association is created, or at least less stress. When this can be achieved via counter conditioning and desensitizing dogs to these intrinsic stimuli, and many times they can be, then life is better for the humans and the dogs that have stress when on leash. This is something that, among dog trainers knowledgeable in the ways of DS/CC, is widely known.

What is less known, is how the process of counter conditioning affects the neurological processing that leads to behavioral and emotional changes, be they towards the dog feeling less fear and stress, or perhaps a positive conditioned emotional response. This blog will discuss the topic of the neurological benefits that accompany counter conditioning and desensitizing dogs when on leash.

It will also ask questions along the way and at the end. Please, anyone in the neuroscience community that may read this blog, I would greatly appreciate any insights and or answers you can supply. If there are additions, subtractions, clarifications, links, etc…all can be added or subtracted to have this blog be as accurate as it can, please let me know. Thank you. Let’s begin.

Stress hormones are reduced when desensitization and counter conditioning is applied.
Stress hormones can have a deleterious effect and impede learning and memory. These neurological “insults” that occur over time, from stress and fear, damage critical neurons and connectors, which can cause many negative side effects cognitively, behaviorally, and within the dog’s immune system.

When dogs are on leash they do not have their flight response, and that makes for some intrinsic stressors on leash. If the dog has a history of being stressed or fearful and lunging and barking at stimuli, the stress is increased by proximity, intensity and duration of exposure to the stimuli. Often there will be an inordinate number of events on leash that will trigger some levels of fear and stress that result in reactivity or perhaps the dog shutting down. The main issue with reactive dogs is the environment always carries the potential of stress being increased, that means an influx of “fight flight”, and dog’s cannot flee on leash, unless the handler runs with the dog when they want to flee or beforehand.

I have found that general counter conditioning for dogs on leash to all sudden environmental contrasts (SEC) reduces stress and raises the reliability of cue recognition significantly. In addition, dogs with a pathology of stress, fearful over threshold reactions to various stimuli will, in time, habituate more so than not, if a proactive counter conditioning protocol is applied as a preventative. This is a process to reduce stress and fear or as a general supportive measure for events on leash that may trigger stress, fear, frustration, even excitability in very pro social dogs can benefit from the procedure of counter conditioning when on leash.

The pro social dog learns, it is more efficient to relax and take food treats for watching people, after all dogs cannot meet everyone, and learning to relax and simply be “paid” for watching people pass at an appropriate distance has helped many young, excited dogs I’ve worked with.

While there is never a zero reduction of stress hormones, and there is always a potential the dog could react over threshold, or freeze up and shut down, as there is a need for these behaviors, after all they are there or a reason, however, there can be a leveling, a homeostasis can be achieved, and that will translate to less stress and a less reactive dog.

Amygdala, Hippocampus, Stress and Long Term Memory
From his lecture at Stamford University on The Limbic System, Dr. Robert Sapolsky illustrates how chronic stress causes growth in the amygdala, one of the main areas that processes stress and fear. Long term chronic stress can shrink the hippocampus, which measures levels of glucocorticoids, and is in large part how the stress response is “turned off”. The hippocampus is also a big factor in long term memory recall and learning. This part of the brain, does lots of work in the processing of learning and memory, two areas related to behavior that we want an animal to feel good about, and an area of the brain we want to be in as healthy a state as possible.

The hippocampus is a main area in mediating surprise and startle, which is a large part of leash reactivity. Along with mediating startle and sudden environmental changes, the hippocampus is also a work horse for habituation and learning, i.e. less stress or more stress, depending on the health and history of the hippocampus.

The ventrotegmental (VTA) is in the Frontal Cortex area of the brain, this is where “anticipation of rewards” and dopamine flourish, this is where the “empowerment of the behavior” to “get the reward” is particularly processing these outcomes in training, and when that training and learning is in a stressful environment such as leash reactive events, this processing of rewards and behavioral outcomes are crucial for what is known as LPT or Long Term Potentiation.

In his lecture from October 28th 2009 At the NIH Lecture series, Dr. Sapolsky illustrates how with chronic stress, the amygdala expands and the hippocampus atrophies, thus leaving the brain in a state of generalized fear when triggered by stimulus known to cause fear and aggression. Thus, LPT is enhanced and fear is learned more readily. Dogs already generalize fear easily as they are an amygdaloidal centric creature. There is already intrinsic stressors when a dog is on leash. It would stand to reason that approaches that reduce stress will be helpful in the dog’s learning not just that the stimulus is not to be feared, but how to behave in the presence of stress.

Sapolsky goes on to state that the frontal cortex sends messages to the amygdala, in essence trying to shut it down, and for the animal, or humans, for that matter to do the right thing when it is the more challenging thing, and this also speaks to the Premack principal.

With proactive counter conditioning and desensitization, the hippocampus, and amygdala, stay healthier, and receive less and less “neuro-insults”. Additionally, counter conditioning has shown that a “reverse” growth, or shrinking back to normal sized areas can occur, and stress reduction by way of D/CC promotes neuron growth not death. This can be achieved when interventions of counter conditioning and desensitization are implemented. fMRI imagining for these positive changes to brain areas has been seen in other animals when tested, so it stands to reason it would with dogs.

Sapolsky details it is possible to “enhance cognition” during stress if there is a way to block (lessen) the stress hormones (glucocorticoids), and enhance other functions that are beneficial to learning (PFC processing, dopamine, estrogen) by manipulating the environments and implementing desensitization and counter conditioning this can be achieved. Sapolsky goes on to state that when this “blocking of stress hormones (glucocorticoids)”, is achieved the animal will learn better during stress and how to handle stress better. (habituate = hippocampus doing its job more efficiently = Dog staying under threshold more so than not).

When there are too many glucocorticoids the hippocampus slows down neurogenesis. When there is a proactive approach to decrease stress and fear with desensitization and counter conditioning, studies have shown you can have a hippocampus learning better during stress, and making more neurons, not damaging them, as the hippocampus is not flooded with GLC’s but “protective secretions” of other neurochemicals. This maps to more habituation, better learning in times of stress, and less and less stress by the dog. Humans just need to formulate a plan and do the work. When they do, better results will occur.

Neurogenesis (Wikipedia) is the process by which nervous system cells, known as neurons, are produced by neural stem cells. Neural stem cells have the potential to produce many different types of neurons. They include neuroepithelial cells (NEPs), stem cells, radial glial cells (RGCs), basal progenitors (BPs), subventricular zone astrocytes, and subgranular zone radial astrocytes, among others. Neurogenesis is most active during embryonic development, but continues throughout adult life.

Neuroplasticity
There is a fantastic research paper entitled Old Dogs Learning New Tricks: Neuroplasticity Beyond the Juvenile Period by Angeline S. Lillard and Alev Erisir.
In its simplest form, neuroplasticity is how malleable the brain is in terms of neuronal changes in connectivity. This neuroplasticity is enhanced by enriching stress free, low stress, or good stressors as environmental influences.

One thing that has been discovered and verified is, repeated motor or cognitive activity can also drive neuro-plastic changes. This is regardless of the source, and when the source is the interventions of humans working towards addressing the associative, predictive values (antecedents) of sudden changes in the environment, to create better associations, and condition “parallel operant sequences” as they occur, there is a change in neural activity, and it leads to a reorganization of neural circuits. This can map to long lasting functional change (LPT). This translates to less and less reactivity, perhaps none if the protocols are started early and often enough in the dog’s life, or perhaps counter conditioning will result in a counter conditioned response that results in a disengagement from the stressful/fearful stimuli. After all many dogs learn that the stimulus is the cue, and they start to self-disengage from the stimuli looking to the hander for reinforcement. When there are less insults to neurons and less stress on the immune system, the dog will learn more efficiently and habituate sooner rather than later. It is simply predicated on the humans having a plan to counter condition the dog when on leash.

Donald Hebb proposed the concept of synapse strengthening back in the 1940’s and 50’s. He discovered; when an axon of cell A is near enough to excite cell B and repeatedly or persistently takes part in firing it, some growth process or metabolic change takes place on one or both cells such that cell A’s efficiency, as one of the cells firing B is increased.

A large part of the neural landscape and the physical attributes that accompany all dogs when on leash is visual and auditory stimuli.

The temporal lobe communicates with the hippocampus and plays a key role in the formation of explicit long-term memory modulated by the amygdala. Sound is processed in large part by the Medial Geniculate Nucleus. Sounds processing is less precise then visual processing.

When dogs are on leash they are met with a multitude of auditory stimuli, traffic, wind, humans, sounds from all spectrums from low rumbles to high pitches, when humans start issuing a “mark & pay, or a “yes” (Click) and treat, protocol for auditory stimuli, it increases the chances the dog will not react over threshold upon those events occurring. Often the preceding auditory antecedents to traffic, people, children especially, and dogs, are appearing first as auditory events, and those should be counter conditioned.
Auditory
Adjacent areas in the superior, posterior, and lateral parts of the temporal lobes are involved in high-level auditory processing. The temporal lobe is involved in primary auditory perception, such as hearing, and holds the primary auditory cortex.[6] The primary auditory cortex receives sensory information from the ears and secondary areas process the information into meaningful units such as speech and words.[6] The superior temporal gyrus includes an area (within the lateral fissure) where auditory signals from the cochlea first reach the cerebral cortex and are processed by the primary auditory cortex in the left temporal lobe.

All visual events on leash have some auditory stimulus attached as discussed in the above section, the auditory stimuli being reinforced with food pairing is crucial for complete counter conditioning, obviously, there will be events that include little or no audio due to the nature of the stimulus, a person behind a glass door, or perhaps the dog and handler are far from another dog, and they just have a visual for the stimulus, but most events have audio, and always remember that ambient audio is attached to these events, even if the audio attached the stimulus is not part of the package.

With visual stimuli many times there are multiple pieces of stimuli to a “package”, or in the environment as the counter conditioning event is occurring. This is what makes the counter conditioning of a dog on leash in a public space so challenging.

For example, when counter conditioning traffic many times it is the audio that the dog orients to first, then they see the traffic. By issuing reinforcements (marking YES & issuing Food), for the sound the visual is less stressful and both parts of the stimulus package are conditioned.

Many times, there will be competing stimuli that if not paid for may also go along for the ride in the “unsafe” determination many dogs make to other dogs, traffic, or people.
For example, if the dog is fearful of traffic, and when they see the traffic pass, and are fearful, and then they see a person, both can go along in the associative stream. When all pieces of stimuli are marked and paid for the better the dog does overall with the entire environment. When the dog is not counter conditioned they may end up being flooded (shutdown) or reactive at people, dogs, traffic, sounds, etc…a generalized fear and stress can build up due to simply being overwhelmed.

Visual
The areas associated with vision in the temporal lobe interpret the meaning of visual stimuli and establish object recognition. The ventral part of the temporal cortices appear to be involved in high-level visual processing of complex stimuli such as faces (fusiform gyrus) and scenes (parahippocampal gyrus). Anterior parts of this ventral stream for visual processing are involved in object perception and recognition.

General counter conditioning maps towards stress reduction.

Counter conditioning a leash reactive dog allows the brain to assemble internal resources more efficiently, by responding to environmental stimuli with a new suite of behaviors, and a new processing of information when met with stimuli on leash, these can be reinforced simply by the leash handler using an event marker (YES/CLICK) and rewarding the dog with high value food for under threshold responses/behaviors in a “suite,” or a range of behaviors that can be classified as “under threshold” for that individual dog. Even if the dog is over threshold and has an event that is classified as “reactive”, the handler should “pay through the event” create distance, reassure the dog, issue food if possible, and mitigate the environment in the moment, “pad” as much as can be padded. Real life training is sometimes messy, even with the cleanest of plans and world class mechanics. Then re tool for the next event. Performance Feedback Revision, as Dr. Susan Freidman says.

Neural circuits and cortical maps come in three distinctions, excitatory, inhibitory, or modulatory. Multiples of these circuits create “cortical maps” of organized receptors or “motor fields” for a given function.

All behavior has a function, and many times the leash reactive dog is struggling with associating stimuli on leash due to their not having a flight response to enact, and that causes some intrinsic stress. When the dog has a generalized fear, or inordinate stress, what is needed is a proactive plan to reduce the stress, even with medications, a plan will enhance the processes of the brain to reorganize and build new neuron connections and strengthen existing connections. When neurons are strengthening towards less stress and the dog is learning the world is safe, or there are alternatives to reacting to achieve reinforcements, the dog will do better and better. It is binary.

Unmasking
This is a special case of changes to existing circuits when excitation of a neuron is reduced, mitigating its inhibitory influence onto other neurons, within the same sensory map. The result can be an instant increase of activity in those other neurons,
Unmasking is thought of as a “widening of the functional response area”.

This functional change is immediate, and it is sustained if the responsible stimulus is maintained: however, no hard-structural changes occurs in neural circuits, making unmasking a special case of neuroplasticity. Unmasking is an extreme instance if a normal function of neural circuits adapting to fluctuations in sensory input. These changes are only permanent to neuroplasticity, not neurodevelopment.

Sensitive and Critical Periods of Development

Sensitive and Critical periods are times when a change in environmental input from what is normal for the organism leads to consequential changes in the brain and behavior, when that same input during a different developmental period would likely lead to much less or even no change at all. Such periods are critical when a specific development must occur or it never would occur at all, and sensitive when it simply requires more input later to change. Neuroplasticity Beyond the Juvenile Period by Angeline S. Lillard and Alev Erisir.

Puppies in their critical development period which ends at week 21 (5 months) are well known to benefit from enriched environments and positive social experiences with humans and other dogs, what many people are not instructed to do is proactively counter condition puppies to sudden changes in the environment, but they should as that can be crucial for habituation to novel stimuli and that will pay big behavioral dividends as the dog develops into adolescence.

As has been illustrated in this blog, the hippocampus is a major player in habituation, learning, mediating startle and sudden changes in the environment, by proactively counter conditioning and working to reduce stress, the puppy will be learning more efficiently during stress. Thus, the puppy develops better coping mechanisms and better neurological processing of stressful or fearful events. Often, people report that dogs are behaviorally “more challenging” during adolescence. By having an acute awareness to a puppies environment and implementing a overly proactive counter conditioning protocol, many challenges and fears that arrive for dogs in adolescence could be avoided or drastically decreased.

Adolescence, is roughly from 5 months through to a year, then the juvenile phase of development occurs, and the dog is roughly “socially mature” around 2-3 years of age, larger breeds/mixes mature a bit longer. One of the most challenging times for canine development is adolescence, this is due to a proliferation of neurological development during the “teen years”. As the brain changes in adolescence it “prunes” neuronal structures and connections, thus forming the mature adult dog brain somewhere between 2 – 3 years of age. Remember all dogs are a study of one, and environments play a huge role in the development of dogs.

This sensitive/adolescence period is a time many people report their dog has “forgotten” cues, “tunes out”, and is more challenging than when they were puppies.

This is due a new load of neural activity. Many times, puppies “come out of their shell”, or develop more confidence in their adolescent and juvenile phase, and this can be a time when leash reactivity starts occurring.

Memory recollection is crucial for all dogs, and this is related to many areas of the brain. Dogs operate largely from working memory. This can be enhanced as any other processes of the brain are by away of helping the dog through stressful events, be they leash reactive or general stress associated with life in the hectic 21st century.

The dorsolateral prefrontal cortex is heavily interconnected with a variety of other cortical brain regions, sending and receiving inputs to/from most sensory brain regions, as well as subcortical brain regions like the basal ganglia.
Also, the frontal cortex is known to handle “executive functions”, a catch-all term for a cluster of higher cognitive skills, such as: working memory maintenance, attention set-shifting (update a behavior when the rules change on you), reward evaluation, motor planning. Dogs have a small frontal cortex, hence one reason dogs can easily be cognitively “tripped up” by distractions.

Another aspect of the frontal cortex is sending signals to the amygdala and convincing it that it is not worth it to be fearful, it is also the area of the brain that deals with decisions, and outcomes when there is a struggle between “do the right thing” verses “do the wrong thing”, in the case with dogs, where it is fight, flight, freeze, it is “do the thing that is less stressful”, and you will get better reinforcements, food, distance, praise/reassurances.

This is all enhanced, and fast tracked when the handler of leash reactive dogs implement desensitization and counter conditioning. The opposite occurs when there are fear and pain based approaches to suppress behaviors, the dog will react more or if not at all, or less, it’s due to the dog shutting down and being in learned helplessness.

In Changing Fear: The Neurosecretory of Emotion Regulation by Catherine A. Hartley and Elizabeth Phelps, discuss how “active coping” can attenuate a learned fear response. By using various “mental strategies” and a “performance of behaviors”, the fear memory can be disrupted. Anyone that has done any form of counter conditioning knows this can be achieved proactively with dogs by way of D/CC, while this research is directed at humans changing fear, dog brains are good analogs for human brains, and vice versa. When humans are issuing the YES&TREAT routine for SEC to dogs on leash, they are proactivity helping the dog actively cope with the stress.

Active coping should hopefully translate into extinction. Extinction refers to the gradual decrease in the expression of the conditioned response (CR), (lunging, barking, freezing) that occurs when the conditioned stimulus (CS) (dogs/humans/traffic) is presented without the reinforcement of the unconditioned stimulus (US) (Food)

Extinction does not erase fearful memories, the original CS-US association is intact. It can reemerge if there is a context shift (renewal), or reinforcements drop, or the stimulus is too sudden, too intense, this original memory can occur with the passing of time as well, known as spontaneous recovery.

By now even the cursory interest in cognition and fear familiarize the inquisitor with the amygdala. The lateral nucleus of the amygdala (LA) is considered what is coding the associations between the CS and US related sensory inputs.

When the CS is present, the LA excites the central nucleus (CE), which controls passive forms of expression of the CR through descending projections to the brainstem and the hypothalamus.
In dogs, the hypothalamus is a central processer in predation, stalking, goal directed behaviors, focus and attention.
This knowledge has led researchers to investigate functional changes during extinction.

Research suggests there is interactions between the amygdala, the ventrotegmental pre frontal cortex, and the hippocampus, which supports acquisition, storage, retrieval, and contextual modulation of fear extinction.
It is precisely this “contextual modulation” that is enhanced by way of proactive counter conditioning for dogs on leash.

Dogs already possess the ability to easily generalize fear, and due to the small frontal cortex, and less executive functions than humans, many times dog simply get the associations wrong and they are not in danger despite what their biology is suggesting,
this is where proactive counter conditioning helps tremendously to reduce stress and create better associations for the dog; regardless of where they’re on the fear spectrum when on leash, all dogs process stimuli with the same regions of the brain, because all dogs need some level of extinction in terms of fear or stress related behaviors and negative emotional responses when on leash.

After extinction is achieved, contextual information has a critical function in terms of which memory will be retrieved, the extinction memory or the fear memory?
Research evidence suggest that the hippocampal projections to the vmPFC and the amygdala mediate the context dependent expression of extinction. (Fanselow 2000, Ji and Maren 2005).

Should the hippocampus receive too many neurological insults, and not be working efficiently, there could be impaired contextual reinstatement if the CR is after the unconditioned stimulus (US) presentations. (Wilson et al 1995).

The hippocampus plays a big role before or after extinction learning, one suggestion is that the hippocampus controls in large part the context specific modulation of both fear expression and CS evoked activity in the LA (lateral amygdala), which leads to a greater responding in the non-extinction context than in the extinction context.
There is strong evidence that the hippocampus, through communications with the vmPFC and the amygdala, regulates the contextual modulation of fear expression during extinction retrieval.

Now what does this mean for handlers of leach reactive dogs? Generalization of fear is easy for dogs, generalization of other responses and the ensuing behaviors are more challenging to generalize. This why many people report “the dog is trained well at the house, but when we leave the house, it is like the dog forgets what he learned”. Nope, dogs just get distracted by all manner of stimuli, add in fear or stress and the dog is trying very hard to determine if they are safe or not, many things for a dog contained on leash, are associated by the dog as “stressful” or “fearful” when they are not at all, and by issuing counter conditioning (YES &TREAT, MARK & PAY), and or creating distances (helping the dog obtain “flight”, away from stress/fear), the human is helping the dog by reducing stress and creating a better association, this will map towards better responses under threshold when the context shifts, and it shifts, often and suddenly when on leash, and as was indicated by the research listed above, the hippocampus controls in large part the context specific modulation of both fear expression and CS evoked activity in the LA (lateral amygdala), which leads to a greater responding in the non-extinction context than in the extinction context.

By issuing proper counter conditioning and distance mitigation, humans are bolstering the chances of the dog responding under threshold and making a new and better association.
When humans use fear and pain to suppress the dog’s reactivity, they run a very high risk the dog will respond over threshold in and out of the context the dog was issued the aversive, any change in the environment is considered a “context shift”. Now think about how much occurs second to second on a leash walk.

What sort of brain do you want the dog to develop, one that learns they are safe, or a brain that learns everything is fearful and possibly painful? It really is up to us humans t work towards stress reduction in our dogs as much as we reasonably can.

All dogs with leash reactivity should be considered a study of one. This is especially important to remember as there are many micro components of the leash reactive events, add in the dog’s age, and stage of neurological development, their pathology, and the ensuing behavioral changes, and it is easy to see each dog will have its own signature behavior suite in response to stimuli on leash. This response suite will be largely predicated on the distance, duration and type of stimuli that the dog may orient to and or react towards. Always factor in the human’s mechanics and timing of reinforcement in the form of distance and high value food rewards, as that is the biggest variable of all, and the one that is most easily changed, but sadly overlooked in far too many assessments of the dog.

One thing is certain, as I have worked with 1000’s of dogs in various contexts that have or could have resulted in leash reactivity, once the human handler starts the Hybrid Approach and issues a marker (YES/Clicker) and starts reinforcing the dog for sudden environmental contrasts with high value food, regardless of what they are responding to or how the dog feels about the sudden changes, the dog does better overall in terms of stress reduction and adherence to general training cues over time. This is a day to day endeavor, there is no magic fix. Once the dog has less stress, they do better, and that is the whole point of training and counter conditioning dogs that have a stress/fear response to sudden environmental stimuli when on leash, to help dogs feel and do better in this hectic world alongside humans when on leash.

In these times when we have an abundance of information on how brans process stress, develop, and expand or atrophy, it is high time we started to look towards this information to help dogs develop and build better neurons, as that will only help, no matter the training, counter conditioning, or what sort of lifestyle the dog is leading, better neurological health is always a plus.

Addendum’s and Questions.
Below are some other areas of interest that support reducing stress and using counter conditioning and desensitization for leash reactive dogs. If any of the readers of this blog have information on these subjects please share. Thanks!

Myelination.
Myelin is a fatty tissue that wraps around axons, as a sheath, and permits faster transmission of neuro signals. This is a lifelong neuro plastic process, and enriched environments are known to create more Myelin, this has been shown in both animals (Markham and Greenough, 2004) and humans (Ullen and Collegues2005).

Two studies have shown that working memory training impacts white matter (Myelin). (Loveden 2010) and (Johansen – Berg 2010).

Seeing as dogs are operating largely from, working memory, supporting the learning process by way of proactive counter conditioning, learning/teaching or positively reinforced repetitions will increase Myelination (speed of learning).

Myelination is a dynamic process that occurs all through life, and by changing the speed of neural transmissions, myelin can modulate neural synchronicity and thus efficiency in adaptation to environmental changes. (Neuroplasticity Beyond the Juvenile Period by Angeline S. Lillard and Alev Erisir).

Now place this in the context of a dog that is being positively trained and counter conditioned to fear or stress on leash, every day in some way, to build resiliency.

Spontaneous Recovery is a phenomenon of learning and memory that was first named and described by Ivan Pavlov in his studies of classical (Pavlovian) conditioning. In that context, it refers to the re-emergence of a previously extinguished conditioned response after a delay. Such a recovery of “lost” behaviors can be observed within a variety of domains.

The research of Bouton and Moody has done an excellent job at detailing what occurs neurologically over temporal contexts (time) and it’s resulting in spontaneous recovery. I have released a video discussing this called Cognition and Memory. Link below.

Spontaneous Recovery as it relates to dogs, my question is…
Seeing as the pre-frontal cortex / basil ganglia “loop” has a role in “memory consolidation”. (associations to CS and US). There is a pathway between the basil ganglia and amygdala inside the neo cortex.

Q_ Is this where spontaneous recovery occurs in part?

The Caudate Nucleus also has a role in “fear related memories” and “voluntary movement”, which is related to freezing up, and no true flight response when on leash.
The Cerebral Cortex has a role in “storing” memory of aversive conditioned responses and “inhibitory functions”, again we see the flight/freeze responses are related to this area or cognitive processing fearful/stressful events.

Q_ what further research has been done on spontaneous recovery that looks at these areas of the cognition that could be potentially related to spontaneous recovery?

Resources

Old Dogs Learning New Tricks: Neuroplasticity Beyond the Juvenile Period by Angeline S. Lillard and Alev Erisir.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3956134/

Changing Fear: The Neurosecretory of Emotion Regulation by Catherine A. Hartley and Elizabeth Phelps
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3055445/#!po=13.4259
The Limbic System Lecture by Dr. Robert Sapolsky https://www.youtube.com/watch?v=CAOnSbDSaOw

Stress and Plasticity in the Limbic System https://www.ncbi.nlm.nih.gov/pubmed/14584827

Dude, Where’s My Prefrontal Cortex? https://nautil.us/issue/15/turbulence/dude-wheres-my-frontal-cortex

Dr. Robert Sapolsky October 28th 2009 At the NIH Lecture series Stress and Societies https://www.youtube.com/watch?v=XvMQQsyPirM

Cognition & Memory – Leash Reactivity https://www.youtube.com/watch?v=3iyjdBKYRGY&t=43s

Counter Conditioning Leash Reactive Dogs https://www.youtube.com/watch?v=OMLrYaoxNOs&t=16s

Counter Conditioning Dogs To Other Dogs On Leash https://www.youtube.com/watch?v=XMLVmiZKlug&t=43s

Counter Conditioning Dogs to Traffic and Humans On Wheels https://www.youtube.com/watch?v=7LOFbaEhVNY&t=23s

Dog Life Episode 6 Counter Conditioning Leash Reactivity https://www.youtube.com/watch?v=HSbFpgbfD3A&t=6s