Peggy Mason | University of Chicago (original) (raw)

Papers by Peggy Mason

Annals of Internal Medicine, Jan 28, 2020

bioRxiv (Cold Spring Harbor Laboratory), Jul 3, 2022

Helping another in distress can be motivated by either affective or cognitive empathy, with the l... more Helping another in distress can be motivated by either affective or cognitive empathy, with the latter commonly believed to be restricted to humans and possibly other apes. Here, we found evidence for rodent helping that occurs in the absence of affective cues. We employed a paradigm in which a free rat can open the door to a restrainer containing a trapped rat. When the trapped rat was treated with the anxiolytic midazolam, the helping behavior exhibited by the free rat was diminished but did not extinguish. Correspondingly, midazolam-treated trapped rats still released themselves when given the opportunity, albeit at longer latencies than controls, evidence that midazolam only partially reduced the distress experienced by trapped rats. To test whether helping could occur for a rat who exhibited no affect, trapped rats were immobilized by general anesthesia or heavy sedation. Surprisingly, rats opened the door to restrainers containing these immobilized rats and pulled the incapacitated rats out of the restrainer, pushing them away from the arena center. The same solicitous behavior was observed when an anesthetized rat was simply placed in the center of the arena, without being confined within a restrainer. We speculate that the cognitive dissonance of immobile rats, at odds with predictive expectations of rat behavior built up over a lifetime, motivated solicitous behavior including helping. To block affective behavioral displays without associated dissonant cues of immobility, metyrapone, a drug that selectively blocks corticosterone synthesis, was administered to trapped rats. Under such circumstances, little helping behavior occurred. In sum, rats may be motivated either by affect or by cognitive dissonance, the latter comprising a rudimentary form of cognitive empathy. .

Brain Research, Sep 1, 1997

he effect of intrathecally administered [D-Ala2,N-Me-Phe4,Gly5-ol]-enkephalin (DAMGO) on withdraw... more he effect of intrathecally administered [D-Ala2,N-Me-Phe4,Gly5-ol]-enkephalin (DAMGO) on withdrawal latencies evoked by noxious heat applied to either cervical or lumbar dermatomes was studied in awake rats. Administration of DAMGO to the lumbar intrathecal space produces a dose-dependent suppression of withdrawals evoked by noxious thermal stimulation in either lumbar or cervical dermatomes. Administration of the same doses of DAMGO to the cervical spinal cord produces a suppression of withdrawals evoked by stimulation in cervical but not lumbar dermatomes. Control experiments provide evidence that the drugs administered intrathecally to either enlargement do not spread to the other enlargement.

Anesthesiology, May 1, 1996

Behaviors of several laboratory animals can be modeled as sequences of stereotyped behaviors, or ... more Behaviors of several laboratory animals can be modeled as sequences of stereotyped behaviors, or behavioral motifs. However, identifying such motifs is a challenging problem. Behaviors have a multi-scale structure: the animal can be simultaneously performing a small-scale motif and a large-scale one (e.g. chewing and feeding). Motifs are compositional: a large-scale motif is a chain of smaller-scale ones, folded in (some behavioral) space in a specific manner. We demonstrate an approach which captures these structures, using rat locomotor data as an example. From the same dataset, we used a preprocessing procedure to create different versions, each describing motifs of a different scale. We then trained several Hidden Markov Models (HMMs) in parallel, one for each dataset version. This approach essentially forced each HMM to learn motifs on a different scale, allowing us to capture behavioral structures lost in previous approaches. By comparing HMMs with models representing different null hypotheses, we found that rat locomotion was composed of distinct motifs from second scale to minute scale. We found that transitions between motifs were modulated by rats' location in the environment, leading to non-Markovian transitions. To test the ethological relevance of motifs we discovered, we compared their usage between rats with differences in a high-level trait, prosociality. We found that these rats had distinct motif repertoires, suggesting that motif usage statistics can be used to infer internal states of rats. Our method is therefore an efficient way to discover multi-scale, compositional structures in animal behaviors. It may also be applied as a sensitive assay for internal states. Preprint. Under review.

Journal of Neurophysiology, Jul 1, 2004

The ventromedial medulla is implicated in a variety of functions including nociceptive and cardio... more The ventromedial medulla is implicated in a variety of functions including nociceptive and cardiovascular modulation and the control of thermoregulation. To determine whether single microinjections into the ventromedial medulla elicit changes in one or multiple functional systems, the GABA A receptor antagonist bicuculline was microinjected (70 nl, 5-50 ng) into the ventromedial medulla of lightly anesthetized rats, and cardiovascular, respiratory, and nociceptive measures were recorded. Bicuculline microinjection into either the midline raphe or the laterally adjacent reticular nucleus simultaneously increased interscapular brown adipose tissue temperature, heart rate, blood pressure, expired [CO 2 ], and respiration rate and elicited shivering. Bicuculline microinjection also decreased the noxious stimulus-evoked changes in heart rate and blood pressure, decreased the frequency of heat-evoked sighs, and suppressed the cortical desynchronization evoked by noxious stimulation. Although bicuculline suppressed the motor withdrawal evoked by noxious tail heat, it enhanced the motor withdrawal evoked by noxious paw heat, evidence for specifically patterned nociceptive modulation. Saline microinjections into midline or lateral sites had no effect on any measured variable. All bicuculline microinjections, midline or lateral, evoked the same set of physiological effects, consistent with the lack of a topographical organization within the ventromedial medulla. Furthermore, as predicted by the isodendritic morphology of cells in the ventromedial medulla, midline bicuculline microinjection increased the number of c-fos immunoreactive cells in both midline raphe and lateral reticular nuclei. In summary, 70-nl microinjections into ventromedial medulla activate cells in multiple nuclei and elicit increases in sympathetic and somatomotor tone and a novel pattern of nociceptive modulation.

bioRxiv (Cold Spring Harbor Laboratory), Mar 17, 2016

American Journal of Physiology-regulatory Integrative and Comparative Physiology, Nov 1, 2009

The raphe magnus (RM) participates in opioid analgesia and contains pain-modulatory neurons with ... more The raphe magnus (RM) participates in opioid analgesia and contains pain-modulatory neurons with respiration-related discharge. Here, we asked whether RM contributes to respiratory depression, the most prevalent lethal effect of opioids. To investigate whether opioidergic transmission in RM produces respiratory depression, we microinjected a mu-opioid receptor agonist, DAMGO, or morphine into the RM of awake rodents. In mice, opioid microinjection produced sustained decreases in respiratory rate (170 to 120 breaths/min), as well as heart rate (520 to 400 beats/min). Respiratory sinus arrhythmia, indicative of enhanced parasympathetic activity, was prevalent in mice receiving DAMGO microinjection. We performed similar experiments in rats but observed no changes in breathing rate or heart rate. Both rats and mice experienced significantly more episodes of bradypnea, indicative of impaired respiratory drive, after opioid microinjection. During spontaneous arousals, rats showed less tachycardia after opioid microinjection than before microinjection, suggestive of an attenuated sympathetic tone. Thus, activation of opioidergic signaling within RM produces effects beyond analgesia, including the unwanted destabilization of cardiorespiratory function. These adverse effects on homeostasis consequent to opioid microinjection imply a role for RM in regulating the balance of sympathetic and parasympathetic tone.

Social Neuroscience, Apr 1, 2010

The Journal of Neuroscience, Jan 12, 2005

Elsevier eBooks, 2018

Abstract Empathy refers to the communication of affect or experience between individuals. One pos... more Abstract Empathy refers to the communication of affect or experience between individuals. One possible outward manifestation of empathy is helping. Here we describe the development of a novel paradigm to test for helping in rats. Potential helper rats are allowed to freely roam in an arena where a rat is trapped in a centrally located Plexiglas restrainer. Hour-long experimental sessions are repeated for 12days. Over progressive days, rats open the restrainer door with increasing consistency and at a decreasing latency. Door-opening does not require that the free rat have the opportunity to play with the released rat. It is also of value to the free rat, on a par with highly palatable food, and is socially selective. Furthermore, door opening behavior is blocked by treatment with a benzodiazepine anxiolytic, demonstrating that door opening is emotionally motivated. Despite the many positive virtues of empathic helping, empathy and helping can also produce antisocial consequences.

HZS, Conception and design, Acquisition of data, Analysis and interpretation of data, Drafting or... more HZS, Conception and design, Acquisition of data, Analysis and interpretation of data, Drafting or revising the article IB-AB, Conception and design, Drafting or revising the article PM, Conception and design, Analysis and interpretation of data, Drafting or revising the article .

The Journal of Neuroscience, Jan 25, 2006

Recent evidence suggests that neurons in the medullary raphe are critical to the activation of br... more Recent evidence suggests that neurons in the medullary raphe are critical to the activation of brown adipose tissue (BAT), the major source of nonshivering heat production in the rat. Yet it is unclear which medullary raphe cells participate in cold defense and how participating cells contribute to BAT activation. Therefore, we recorded extracellularly from raphe cells during three thermoregulatory challenges that evoked an increase in BAT temperature in anesthetized rats: central cold, ambient cold, or intracerebroventricular prostaglandin E 2 (PGE 2) injection. Physiologically identified serotonergic (p5HT) cell discharge increased in response to cold or PGE 2 administration and was positively correlated with BAT temperature. However, none of the 147 physiologically identified nonserotonergic (non-p5HT) cells recorded responded to thermoregulatory challenges that evoked an increase in BAT temperature. To test for modulation of BAT activation by non-p5HT cells that are either excited (ON cells) or inhibited (OFF cells) by noxious cutaneous stimulation, noxious stimuli were applied during evoked BAT temperature increases. Noxious stimulation suppressed BAT activation, suggesting that cells inhibited by noxious stimulation facilitate spinal circuits controlling BAT. To test whether medullary OFF cells modulate BAT activity, the-opiate receptor agonist (D-Ala 2 , N-Me-Phe 4 , Gly-ol 5)-enkephalin (DAMGO) was microinjected into the raphe magnus, a manipulation that selectively activates OFF cells. DAMGO microinjection blocked noxious stimulation-evoked suppression of PGE 2-induced BAT temperature increases. Thus, both p5HT and non-p5HT OFF cells in the medullary raphe facilitate BAT activation in response to cold challenge or pyrogen.

arXiv (Cornell University), Jul 11, 2017

Behaviors of several laboratory animals can be modeled as sequences of stereotyped behaviors, or ... more Behaviors of several laboratory animals can be modeled as sequences of stereotyped behaviors, or behavioral motifs. However, identifying such motifs is a challenging problem. Behaviors have a multi-scale structure: the animal can be simultaneously performing a small-scale motif and a large-scale one (e.g. chewing and feeding). Motifs are compositional: a large-scale motif is a chain of smaller-scale ones, folded in (some behavioral) space in a specific manner. We demonstrate an approach which captures these structures, using rat locomotor data as an example. From the same dataset, we used a preprocessing procedure to create different versions, each describing motifs of a different scale. We then trained several Hidden Markov Models (HMMs) in parallel, one for each dataset version. This approach essentially forced each HMM to learn motifs on a different scale, allowing us to capture behavioral structures lost in previous approaches. By comparing HMMs with models representing different null hypotheses, we found that rat locomotion was composed of distinct motifs from second scale to minute scale. We found that transitions between motifs were modulated by rats' location in the environment, leading to non-Markovian transitions. To test the ethological relevance of motifs we discovered, we compared their usage between rats with differences in a high-level trait, prosociality. We found that these rats had distinct motif repertoires, suggesting that motif usage statistics can be used to infer internal states of rats. Our method is therefore an efficient way to discover multi-scale, compositional structures in animal behaviors. It may also be applied as a sensitive assay for internal states. Preprint. Under review.

arXiv (Cornell University), Jul 11, 2017

To effectively connect animal behaviors to activities and patterns in the nervous system, it is i... more To effectively connect animal behaviors to activities and patterns in the nervous system, it is ideal have a precise, accurate, and complete description of stereotyped modules and their dynamics in behaviors. In case of rodent behaviors, observers have identified and described several stereotyped behaviors, such as grooming and lateral threat. Discovering behavioral repertoires in this way is imprecise, slow and contaminated with biases and individual differences. As a replacement, we propose a framework for unbiased, efficient and precise investigation of rat locomotor activities. We propose that locomotion possesses multiscale dynamics that can be well approximated by multiple Markov processes running in parallel at different spatial-temporal scales. To capture motifs and transition dynamics on multiple scales, we developed a segmentation-decomposition procedure, which imposes explicit constraints on timescales on parallel Hidden Markov Models (HMM). Each HMM describes the motifs and transition dynamics at its respective timescale. We showed that the motifs discovered across timescales have experimental significance and space-dependent heterogeneity. Through statistical tests, we show that locomotor dynamics largely conforms with Markov property across scales. Finally, using layered HMMs, we showed that motif assembly is strongly constrained to a few fixed sequences. The motifs potentially reflect outputs of canonical underlying behavioral output motifs. Our approach and results for the first time capture behavioral dynamics at different spatial-temporal scales, painting a more complete picture of how behaviors are organized.

Proceedings of The Royal Society B: Biological Sciences, Nov 8, 2017

Well over 90% of studies in biomedical sciences are performed on single animals. While knowledge ... more Well over 90% of studies in biomedical sciences are performed on single animals. While knowledge of the genetics, development and physiology of single individuals accrues, an understanding of the biological mechanisms by which individuals interact has barely budged. Yet many of society's greatest problems derive from an inability of humans to get along with each other. Studies in social neuroscience are primarily observational and rarely employ subjects who physically interact. Thus, social interaction represents a largely unexplored frontier of biology. The neuroscience that underlies social behaviour and interactions can and should be studied using the scientific method. However, a workable and objective definitional framework of sociality is needed for scientific progress in this field. Here we propose a definition that uses a test of independence from the presence of others. The null hypothesis is that a behaviour is independent from the influence of others. Rejection of this null hypothesis means that the actions of an individual depend on the actions of one or more other individuals. This definition has the advantages of not being contaminated by moral judgements or biases in favour of pro-social behaviour, and of being applicable to a wide range of physiological processes. The definition of a social behaviour proposed here says nothing regarding the valence of the behaviour with respect to others. Thus, a behaviour that is influenced by the presence of others may benefit, harm, or have no effect on others. It is hoped that this definitional framework for sociality will facilitate our understanding of the origins and mechanisms of social behaviour among animals including humans as well as offer efficacious approaches to social disorders such as autism.

Annals of Internal Medicine, Jan 28, 2020

bioRxiv (Cold Spring Harbor Laboratory), Jul 3, 2022

Helping another in distress can be motivated by either affective or cognitive empathy, with the l... more Helping another in distress can be motivated by either affective or cognitive empathy, with the latter commonly believed to be restricted to humans and possibly other apes. Here, we found evidence for rodent helping that occurs in the absence of affective cues. We employed a paradigm in which a free rat can open the door to a restrainer containing a trapped rat. When the trapped rat was treated with the anxiolytic midazolam, the helping behavior exhibited by the free rat was diminished but did not extinguish. Correspondingly, midazolam-treated trapped rats still released themselves when given the opportunity, albeit at longer latencies than controls, evidence that midazolam only partially reduced the distress experienced by trapped rats. To test whether helping could occur for a rat who exhibited no affect, trapped rats were immobilized by general anesthesia or heavy sedation. Surprisingly, rats opened the door to restrainers containing these immobilized rats and pulled the incapacitated rats out of the restrainer, pushing them away from the arena center. The same solicitous behavior was observed when an anesthetized rat was simply placed in the center of the arena, without being confined within a restrainer. We speculate that the cognitive dissonance of immobile rats, at odds with predictive expectations of rat behavior built up over a lifetime, motivated solicitous behavior including helping. To block affective behavioral displays without associated dissonant cues of immobility, metyrapone, a drug that selectively blocks corticosterone synthesis, was administered to trapped rats. Under such circumstances, little helping behavior occurred. In sum, rats may be motivated either by affect or by cognitive dissonance, the latter comprising a rudimentary form of cognitive empathy. .

Brain Research, Sep 1, 1997

he effect of intrathecally administered [D-Ala2,N-Me-Phe4,Gly5-ol]-enkephalin (DAMGO) on withdraw... more he effect of intrathecally administered [D-Ala2,N-Me-Phe4,Gly5-ol]-enkephalin (DAMGO) on withdrawal latencies evoked by noxious heat applied to either cervical or lumbar dermatomes was studied in awake rats. Administration of DAMGO to the lumbar intrathecal space produces a dose-dependent suppression of withdrawals evoked by noxious thermal stimulation in either lumbar or cervical dermatomes. Administration of the same doses of DAMGO to the cervical spinal cord produces a suppression of withdrawals evoked by stimulation in cervical but not lumbar dermatomes. Control experiments provide evidence that the drugs administered intrathecally to either enlargement do not spread to the other enlargement.

Anesthesiology, May 1, 1996

Behaviors of several laboratory animals can be modeled as sequences of stereotyped behaviors, or ... more Behaviors of several laboratory animals can be modeled as sequences of stereotyped behaviors, or behavioral motifs. However, identifying such motifs is a challenging problem. Behaviors have a multi-scale structure: the animal can be simultaneously performing a small-scale motif and a large-scale one (e.g. chewing and feeding). Motifs are compositional: a large-scale motif is a chain of smaller-scale ones, folded in (some behavioral) space in a specific manner. We demonstrate an approach which captures these structures, using rat locomotor data as an example. From the same dataset, we used a preprocessing procedure to create different versions, each describing motifs of a different scale. We then trained several Hidden Markov Models (HMMs) in parallel, one for each dataset version. This approach essentially forced each HMM to learn motifs on a different scale, allowing us to capture behavioral structures lost in previous approaches. By comparing HMMs with models representing different null hypotheses, we found that rat locomotion was composed of distinct motifs from second scale to minute scale. We found that transitions between motifs were modulated by rats' location in the environment, leading to non-Markovian transitions. To test the ethological relevance of motifs we discovered, we compared their usage between rats with differences in a high-level trait, prosociality. We found that these rats had distinct motif repertoires, suggesting that motif usage statistics can be used to infer internal states of rats. Our method is therefore an efficient way to discover multi-scale, compositional structures in animal behaviors. It may also be applied as a sensitive assay for internal states. Preprint. Under review.

Journal of Neurophysiology, Jul 1, 2004

The ventromedial medulla is implicated in a variety of functions including nociceptive and cardio... more The ventromedial medulla is implicated in a variety of functions including nociceptive and cardiovascular modulation and the control of thermoregulation. To determine whether single microinjections into the ventromedial medulla elicit changes in one or multiple functional systems, the GABA A receptor antagonist bicuculline was microinjected (70 nl, 5-50 ng) into the ventromedial medulla of lightly anesthetized rats, and cardiovascular, respiratory, and nociceptive measures were recorded. Bicuculline microinjection into either the midline raphe or the laterally adjacent reticular nucleus simultaneously increased interscapular brown adipose tissue temperature, heart rate, blood pressure, expired [CO 2 ], and respiration rate and elicited shivering. Bicuculline microinjection also decreased the noxious stimulus-evoked changes in heart rate and blood pressure, decreased the frequency of heat-evoked sighs, and suppressed the cortical desynchronization evoked by noxious stimulation. Although bicuculline suppressed the motor withdrawal evoked by noxious tail heat, it enhanced the motor withdrawal evoked by noxious paw heat, evidence for specifically patterned nociceptive modulation. Saline microinjections into midline or lateral sites had no effect on any measured variable. All bicuculline microinjections, midline or lateral, evoked the same set of physiological effects, consistent with the lack of a topographical organization within the ventromedial medulla. Furthermore, as predicted by the isodendritic morphology of cells in the ventromedial medulla, midline bicuculline microinjection increased the number of c-fos immunoreactive cells in both midline raphe and lateral reticular nuclei. In summary, 70-nl microinjections into ventromedial medulla activate cells in multiple nuclei and elicit increases in sympathetic and somatomotor tone and a novel pattern of nociceptive modulation.

bioRxiv (Cold Spring Harbor Laboratory), Mar 17, 2016

American Journal of Physiology-regulatory Integrative and Comparative Physiology, Nov 1, 2009

The raphe magnus (RM) participates in opioid analgesia and contains pain-modulatory neurons with ... more The raphe magnus (RM) participates in opioid analgesia and contains pain-modulatory neurons with respiration-related discharge. Here, we asked whether RM contributes to respiratory depression, the most prevalent lethal effect of opioids. To investigate whether opioidergic transmission in RM produces respiratory depression, we microinjected a mu-opioid receptor agonist, DAMGO, or morphine into the RM of awake rodents. In mice, opioid microinjection produced sustained decreases in respiratory rate (170 to 120 breaths/min), as well as heart rate (520 to 400 beats/min). Respiratory sinus arrhythmia, indicative of enhanced parasympathetic activity, was prevalent in mice receiving DAMGO microinjection. We performed similar experiments in rats but observed no changes in breathing rate or heart rate. Both rats and mice experienced significantly more episodes of bradypnea, indicative of impaired respiratory drive, after opioid microinjection. During spontaneous arousals, rats showed less tachycardia after opioid microinjection than before microinjection, suggestive of an attenuated sympathetic tone. Thus, activation of opioidergic signaling within RM produces effects beyond analgesia, including the unwanted destabilization of cardiorespiratory function. These adverse effects on homeostasis consequent to opioid microinjection imply a role for RM in regulating the balance of sympathetic and parasympathetic tone.

Social Neuroscience, Apr 1, 2010

The Journal of Neuroscience, Jan 12, 2005

Elsevier eBooks, 2018

Abstract Empathy refers to the communication of affect or experience between individuals. One pos... more Abstract Empathy refers to the communication of affect or experience between individuals. One possible outward manifestation of empathy is helping. Here we describe the development of a novel paradigm to test for helping in rats. Potential helper rats are allowed to freely roam in an arena where a rat is trapped in a centrally located Plexiglas restrainer. Hour-long experimental sessions are repeated for 12days. Over progressive days, rats open the restrainer door with increasing consistency and at a decreasing latency. Door-opening does not require that the free rat have the opportunity to play with the released rat. It is also of value to the free rat, on a par with highly palatable food, and is socially selective. Furthermore, door opening behavior is blocked by treatment with a benzodiazepine anxiolytic, demonstrating that door opening is emotionally motivated. Despite the many positive virtues of empathic helping, empathy and helping can also produce antisocial consequences.

HZS, Conception and design, Acquisition of data, Analysis and interpretation of data, Drafting or... more HZS, Conception and design, Acquisition of data, Analysis and interpretation of data, Drafting or revising the article IB-AB, Conception and design, Drafting or revising the article PM, Conception and design, Analysis and interpretation of data, Drafting or revising the article .

The Journal of Neuroscience, Jan 25, 2006

Recent evidence suggests that neurons in the medullary raphe are critical to the activation of br... more Recent evidence suggests that neurons in the medullary raphe are critical to the activation of brown adipose tissue (BAT), the major source of nonshivering heat production in the rat. Yet it is unclear which medullary raphe cells participate in cold defense and how participating cells contribute to BAT activation. Therefore, we recorded extracellularly from raphe cells during three thermoregulatory challenges that evoked an increase in BAT temperature in anesthetized rats: central cold, ambient cold, or intracerebroventricular prostaglandin E 2 (PGE 2) injection. Physiologically identified serotonergic (p5HT) cell discharge increased in response to cold or PGE 2 administration and was positively correlated with BAT temperature. However, none of the 147 physiologically identified nonserotonergic (non-p5HT) cells recorded responded to thermoregulatory challenges that evoked an increase in BAT temperature. To test for modulation of BAT activation by non-p5HT cells that are either excited (ON cells) or inhibited (OFF cells) by noxious cutaneous stimulation, noxious stimuli were applied during evoked BAT temperature increases. Noxious stimulation suppressed BAT activation, suggesting that cells inhibited by noxious stimulation facilitate spinal circuits controlling BAT. To test whether medullary OFF cells modulate BAT activity, the-opiate receptor agonist (D-Ala 2 , N-Me-Phe 4 , Gly-ol 5)-enkephalin (DAMGO) was microinjected into the raphe magnus, a manipulation that selectively activates OFF cells. DAMGO microinjection blocked noxious stimulation-evoked suppression of PGE 2-induced BAT temperature increases. Thus, both p5HT and non-p5HT OFF cells in the medullary raphe facilitate BAT activation in response to cold challenge or pyrogen.

arXiv (Cornell University), Jul 11, 2017

Behaviors of several laboratory animals can be modeled as sequences of stereotyped behaviors, or ... more Behaviors of several laboratory animals can be modeled as sequences of stereotyped behaviors, or behavioral motifs. However, identifying such motifs is a challenging problem. Behaviors have a multi-scale structure: the animal can be simultaneously performing a small-scale motif and a large-scale one (e.g. chewing and feeding). Motifs are compositional: a large-scale motif is a chain of smaller-scale ones, folded in (some behavioral) space in a specific manner. We demonstrate an approach which captures these structures, using rat locomotor data as an example. From the same dataset, we used a preprocessing procedure to create different versions, each describing motifs of a different scale. We then trained several Hidden Markov Models (HMMs) in parallel, one for each dataset version. This approach essentially forced each HMM to learn motifs on a different scale, allowing us to capture behavioral structures lost in previous approaches. By comparing HMMs with models representing different null hypotheses, we found that rat locomotion was composed of distinct motifs from second scale to minute scale. We found that transitions between motifs were modulated by rats' location in the environment, leading to non-Markovian transitions. To test the ethological relevance of motifs we discovered, we compared their usage between rats with differences in a high-level trait, prosociality. We found that these rats had distinct motif repertoires, suggesting that motif usage statistics can be used to infer internal states of rats. Our method is therefore an efficient way to discover multi-scale, compositional structures in animal behaviors. It may also be applied as a sensitive assay for internal states. Preprint. Under review.

arXiv (Cornell University), Jul 11, 2017

To effectively connect animal behaviors to activities and patterns in the nervous system, it is i... more To effectively connect animal behaviors to activities and patterns in the nervous system, it is ideal have a precise, accurate, and complete description of stereotyped modules and their dynamics in behaviors. In case of rodent behaviors, observers have identified and described several stereotyped behaviors, such as grooming and lateral threat. Discovering behavioral repertoires in this way is imprecise, slow and contaminated with biases and individual differences. As a replacement, we propose a framework for unbiased, efficient and precise investigation of rat locomotor activities. We propose that locomotion possesses multiscale dynamics that can be well approximated by multiple Markov processes running in parallel at different spatial-temporal scales. To capture motifs and transition dynamics on multiple scales, we developed a segmentation-decomposition procedure, which imposes explicit constraints on timescales on parallel Hidden Markov Models (HMM). Each HMM describes the motifs and transition dynamics at its respective timescale. We showed that the motifs discovered across timescales have experimental significance and space-dependent heterogeneity. Through statistical tests, we show that locomotor dynamics largely conforms with Markov property across scales. Finally, using layered HMMs, we showed that motif assembly is strongly constrained to a few fixed sequences. The motifs potentially reflect outputs of canonical underlying behavioral output motifs. Our approach and results for the first time capture behavioral dynamics at different spatial-temporal scales, painting a more complete picture of how behaviors are organized.

Proceedings of The Royal Society B: Biological Sciences, Nov 8, 2017

Well over 90% of studies in biomedical sciences are performed on single animals. While knowledge ... more Well over 90% of studies in biomedical sciences are performed on single animals. While knowledge of the genetics, development and physiology of single individuals accrues, an understanding of the biological mechanisms by which individuals interact has barely budged. Yet many of society's greatest problems derive from an inability of humans to get along with each other. Studies in social neuroscience are primarily observational and rarely employ subjects who physically interact. Thus, social interaction represents a largely unexplored frontier of biology. The neuroscience that underlies social behaviour and interactions can and should be studied using the scientific method. However, a workable and objective definitional framework of sociality is needed for scientific progress in this field. Here we propose a definition that uses a test of independence from the presence of others. The null hypothesis is that a behaviour is independent from the influence of others. Rejection of this null hypothesis means that the actions of an individual depend on the actions of one or more other individuals. This definition has the advantages of not being contaminated by moral judgements or biases in favour of pro-social behaviour, and of being applicable to a wide range of physiological processes. The definition of a social behaviour proposed here says nothing regarding the valence of the behaviour with respect to others. Thus, a behaviour that is influenced by the presence of others may benefit, harm, or have no effect on others. It is hoped that this definitional framework for sociality will facilitate our understanding of the origins and mechanisms of social behaviour among animals including humans as well as offer efficacious approaches to social disorders such as autism.

Proceedings of the 19th International Congress of Phonetic Sciences, Melbourne, Australia 2019, 2019

Perceptual recalibration is the lasting effect of adjustments in category boundaries as a result ... more Perceptual recalibration is the lasting effect of adjustments in category boundaries as a result of non-auditory stimuli, including speech imagery [12], i.e. silent and imagined articulations. The present study examines perceptual recalibration from speech imagery in American English sibilants and asks what role haptic feedback and the recruitment of the motor system play in perceptual recalibration. We compare a control group to Kim, a woman with a unique congenital neuropathy who lacks all somatosensa-tion. The results of this study find evidence for perceptual recalibration from both silent and imagined articulations in the control group, but no evidence for recalibration in either condition for Kim. These findings suggest that perceptual recalibration from speech imagery may require the activation of haptic sensations even when the articulators are immobile.