Animal Assisted Therapy (AAT) involves using certified therapy animals as tools to aid in a therapeutic
program. AAT has been used in a variety of settings including hospitals, schools, nursing homes, and
therapeutic clinics and with patients with mental health (i.e. depression, anxiety), physical health (pain
management) and cognitive differences  (i.e. dementia, autism). AAT may help relax, motivate, and improve
executive function in patients and has been shown to increase performance outcomes related to executive
function tasks (Gee et al., 2009, 2010) and decrease volatility in emotionally compromised and typical
individuals (Kotrschal & Ortbauer, 2003; Walsh et al., 1995).

Research has shown that language impaired and typical preschoolers adhere more appropriately to instructions
when modeling a therapy dog compared to an adult or a stuffed animal and made fewer errors when completing
object categorization tasks when with a therapy dog (Gee et al., 2009, 2010). These findings reinforce previous
findings that a dog in the classroom may positively impact social cohesion and improve teaching conditions by
decreasing behavioral extremes and hyperactivity (Kotrschal & Ortbauer, 2003).

These studies showed that when simply in the presence of, and not necessarily interacting with a therapy dog,
some change in higher level executive cortical function was taking place that improved task outcomes, however,
the researchers had no explanation as to what or where those cortical change were occurring. Some researchers
have theorized that subcortical regions of the brain release more oxytocin (popularly referred to as the “love
hormone”) and-or phenylethylamine (similar to the effect of eating chocolate) after positive human-animal
interactions may alter subcortical functions (Beetz et al., 2012; Odendaal & Lehmann, 2000), but this would not
explain the improvement in executive function.

Research into equine therapy and children with autism spectrum disorder revealed that there were significant
increases in expressive and receptive language functions/outcomes in the experimental group as compared to the
control group not receiving equine therapy (Kwon et al., 2019; Peters et al., 2020). One explanation for the
improvement in language function and decreases in hyperactivity and irritability may have been due to a
reduction in cortisol (stress hormone) levels in the experimental group (Pan et al., 2019). Again though, the
hypothalamic-pituitary-adrenal (HPA) axis that controls cortisol production is primarily based in and affects
subcortical regions of the brain.

Evidence that animals activate regions of the brain that are responsible for raw emotions and feelings (i.e. the
limbic system – specifically the amygdala and hypothalamus) have been shown in studies using fMRI (Fang et
al., 2016). Dogs often elicit positive emotions and reduce stress in many people and PET imaging studies
showed reduced activation in thalamic regions indicating reduction in the release of cortisol (Sugawara et al.,
2012).

The cortico(prefrontal)-limbic circuit is integral to emotional processing and regulation (Comte et al., 2016) and
is achieved primarily in the dorsolateral prefrontal cortex (DLPFC, BA46). Also, DLPFC (BA46) has been
shown to be active when regulating emotions in speech during verbal fluency tasks using fMRI (Okada et al.,
2003), fNIRS (Matsuo et al., 2002), and SPECT (Audenaert et al., 2002). DLPFC (BA46) is highly connect with
Broca’s area (BA44-45) and both areas have been consistently shown to be active in children and adults during
verbal fluency tasks. No studies, however, have shown activation in executive regulatory functions or speech
control areas related to the presence of or interaction with an animal.

Therefore, in the current study we sought to determine if the presence of a therapy dog effects the prefrontal
cortico-limbic circuit connectivity and activation of the prefrontal (BA46) and premotor speech areas of the
brain during a speech task (verbal fluency task) using fNIRS.

Methods:
9 neurotypical female participants were recruited between the ages of 18-35, 7 met inclusion criteria. Data on
brain activation and verbal fluency task performance were collected across 3 study conditions: (1) in the
presence of (in contact with) a certified therapy dog, (2) in the presence of (in contact with) a stuffed animal
version of the therapy dog, and (3) a no therapy dog or stuffed animal dog present (control) randomly selected
over 15 trials (5 per condition). 1-minute data collection window to complete verbal fluency task with 1-minute
rest.
The phonemic Verbal fluency tasks, scored on a modified Controlled Oral word Association Test (COWAT),
consisted of 15 letters randomly assigned to each condition. Bilateral cortical activation patterns in the
prefrontal, and perisylvian region (i.e., BA44 Broca’s area, BA46 DLPFC) were acquired using a continuous
functional Near-Infrared Spectroscopy (fNIRS) system; accurate to within 5mm of target substrate.
Results:
Verbal fluency test results showed no difference between conditions (p=.672) as expected. fNIRS data were
analyzed using a “Z-score of change” and t-tests comparisons across conditions per placement. Activation of 2
of 3 probes placed within DLPFC (BA46) were significantly higher with the therapy dog than control (p=.041,
p=.008, p=.098).

Conclusions:
Previous studies have struggled to determine the neurophysiological reasons why children with autism have
significantly increased expressive language and new words spoken when engaged in AAT (Gabriels et al.,
2015). Our findings may help explain why these improvements occurs; DLPFC shows increased activation with
the dog present, directly inputs emotional regulation for speech to Broca’s Area. Furthermore, psychology
research has shown that patients with depression have significantly suppressed DLPFC, but normalizes with
medical treatment (Taylor et al., 2022), resulting in a monotone voice with reduced rate of speech (France et al.,
2000). Our findings that a therapy dog significantly increases activation of DLPFC without the use of
medication may provide new avenues of treatment to improve outcomes in this patient population.

Although this study was limited by the small N and minor issues with cap placement, our study showed that
fNIRS is a viable investigatory tool to identify patterns of cortical activation related to emotional processing and
expressive language. We are currently developing several follow-up studies to determine if these findings are
consistent in typically developing children as compared to children with autism in which verbal output is
reduced.