- Emory University, Neuroscience, Post-DocRadboud University Nijmegen, Donders Centre for Cognition, Post-Docadd
- Neuroscience, Cognitive Neuroscience, Evolution, Primatology, Anthropology, Network Analysis, and 19 moreDTI - Diffusion Tensor Imaging, Chimpanzees, White Matter Architecture, Diffusion MRI Tractography, Temporal Lobe, Neuroanatomy, Cytoarchitecture, Language, Phylogenetics, Embodied Cognition, Abstraction, Conceptual Knowledge, Semantic Information, Feminist Theory, Human Evolution, Biological Anthropology, Genealogy, Science and Technology Studies, and Gender and Women's Studiesedit
- My work focuses on evolutionary neuroanatomy using diffusion tractography to compare the cortico-cortical connectivity of association areas in humans, chimpanzees, and macaques.edit
Research Interests:
Understanding the phylogeny of the human brain requires an appreciation of brain organization of our closest animal relatives. Neuroimaging tools such as magnetic resonance imaging (MRI) allow us to study whole-brain organization in... more
Understanding the phylogeny of the human brain requires an appreciation of brain organization of our closest animal relatives.
Neuroimaging tools such as magnetic resonance imaging (MRI) allow us to study whole-brain organization in species which
can otherwise not be studied. Here, we used diffusion MRI to reconstruct the connections of the cortical hemispheres of the
chimpanzee. This allowed us to perform an exploratory analysis of the grey matter structures of the chimpanzee cerebral
cortex and their underlying white matter connectivity profiles. We identified a number of networks that strongly resemble
those found in other primates, including the corticospinal system, limbic connections through the cingulum bundle and fornix,
and occipital–temporal and temporal–frontal systems. Notably, chimpanzee temporal cortex showed a strong resemblance
to that of the human brain, providing some insight into the specialization of the two species’ shared lineage.
Neuroimaging tools such as magnetic resonance imaging (MRI) allow us to study whole-brain organization in species which
can otherwise not be studied. Here, we used diffusion MRI to reconstruct the connections of the cortical hemispheres of the
chimpanzee. This allowed us to perform an exploratory analysis of the grey matter structures of the chimpanzee cerebral
cortex and their underlying white matter connectivity profiles. We identified a number of networks that strongly resemble
those found in other primates, including the corticospinal system, limbic connections through the cingulum bundle and fornix,
and occipital–temporal and temporal–frontal systems. Notably, chimpanzee temporal cortex showed a strong resemblance
to that of the human brain, providing some insight into the specialization of the two species’ shared lineage.
Research Interests:
The temporal lobe is a morphological specialization of primates resulting from an expansion of higher-order visual cortex that is a hallmark of the primate brain. Among primates, humans possess a temporal lobe that has significantly... more
The temporal lobe is a morphological specialization of primates resulting from an expansion of higher-order visual cortex that is a hallmark of the primate brain. Among primates, humans possess a temporal lobe that has significantly expanded. Several uniquely human cognitive abilities, including language comprehension, semantic memory, and aspects of conceptual processing, are represented in the temporal lobe. Understanding how the temporal lobe has been modified and reorganized in the human lineage is crucial to understanding how it supports human cognitive specializations. Identifying these structural modifications requires a direct comparison with other primates, with special attention to our closest relatives, the chimpanzees. Comparative examination of data from architectonics, tract tracing, and newer imaging methodologies suggests modifications to external morphology (gyri and sulci), preferential expansion of association areas, and elaboration of white matter fasciculi, distinguishing the human temporal lobe from those of Old World monkeys. Chimpanzees and humans share some of these features of cortical expansion, although more research is needed in order to elucidate whether humans possess simply a large hominoid temporal lobe or whether important reorganization has happened since our divergence from chimpanzees.
Research Interests:
Vesicular glutamate transporters (VGLUTs) reuptake glutamate into synaptic vesicles at excitatory synapses. VGLUT2 is localized in the cortical terminals of neuronal somas located in the main sensory nuclei of the thalamus. Thus,... more
Vesicular glutamate transporters (VGLUTs) reuptake glutamate into synaptic vesicles at excitatory synapses. VGLUT2 is localized in the cortical terminals of neuronal somas located in the main sensory nuclei of the thalamus. Thus, immunolabeling of cortex with antibodies to VGLUT2 can reveal geniculostriate terminal distributions in species in which connectivity cannot be studied with tract-tracing techniques, permitting broader comparative studies of cortical specializations. Here, we used VGLUT2 immunohistochemistry to compare the organization of geniculostriate afferents in primary visual cortex in hominid primates (humans, chimpanzees, and an orangutan), Old World monkeys (rhesus macaques and vervets), and New World monkeys (squirrel monkeys). The New and Old World monkeys had a broad, dense band of terminal-like labeling in cortical layer 4C, a narrow band of labeling in layer 4A, and additional labeling in layers 2/3 and 6, consistent with results from conventional tract-tracing studies in these species. By contrast, although the hominid primates had a prominent layer 4C band, labeling of layer 4A was sparse or absent. Labeling was also present in layers 2/3 and 6, although labeling of layer 6 was weaker in hominids and possibly more individually variable than in Old and New World monkeys. These findings are consistent with previous observations from cytochrome oxidase histochemistry and a very small number of connectivity studies, suggesting that the projections from the parvocellular layers of the lateral geniculate nucleus to layer 4A were strongly reduced or eliminated in humans and apes following their evolutionary divergence from the other anthropoid primates.
Research Interests:
We examined intraspecific relationships in the eastern fox squirrel (Sciurus niger) and the eastern gray squirrel (S. carolinensis) using sequence variation in a portion of the mitochondrial DNA cytochrome-b gene and part of the D-loop in... more
We examined intraspecific relationships in the eastern fox squirrel (Sciurus niger) and the eastern gray squirrel (S. carolinensis) using sequence variation in a portion of the mitochondrial DNA cytochrome-b gene and part of the D-loop in the control region. These closely related species are codistributed temperate forest obligates that have similar generation time and population ecologies. For both species, we documented high haplotype diversity, low nucleotide variation, and several groups of divergent haplotypes. However, there is a general lack of spatial structure in maternal lineages within each species. For S. carolinensis, we observed a pattern of population genetic structure that suggests the presence of at least 2 distinct refugial populations that evolved in isolation during the Pleistocene (approximately 98.3–266.3 thousand years ago [kya]) and subsequently expanded to the species' current range following the last glacial maximum. For S. niger, the genetic structure was much less pronounced, with fewer strongly diverged haplotypes. This finding suggests that eastern fox squirrels persisted in either a single population in a glacial refugium or as several refugial populations that maintained gene flow throughout the Pleistocene. For both species, there is evidence that scattered populations were present in multiple, small refugia close to the Laurentide Ice Sheet, allowing rapid range expansion following glacial recession. Taken together, our results indicate that S. niger and S. carolinensis underwent multiple episodes of genetic divergence during isolation in glacial refugia, followed by range expansion and contact that resulted in admixture of divergent maternal lineages within each species during interglacials. Examination of our data further indicates that the most recent range expansion in both species occurred within the past 12–20 kya.
Research Interests:
Background and Purpose: Ivermectin is a common anthelmintic drug, widely used in laboratory rodents for treatment of pinworm and mite infestations. We evaluated the action of ivermectin on sensitive behavioral tasks in mice during... more
Background and Purpose: Ivermectin is a common anthelmintic drug, widely used in laboratory rodents for treatment of pinworm and mite infestations. We evaluated the action of ivermectin on sensitive behavioral tasks in mice during treatment for mites within a barrier facility.
Methods: A total of 21 (5 males, 16 females) mice (129/SvEv) were used for measuring body weight, open field locomotor activity, and rotarod motor coordination. For acoustic startle and prepulse inhibition, 20 C57BL/6J and 29 AKR/J mice were studied. For the Morris water task, the same 20 C57BL/6J mice were studied. Ivermectin (0.08% sheep drench) was administered in the drinking water of the home cage for 8 weeks. Control groups received normal tap water in identical bottles.
Results: Ivermectin did not affect general health, body weight, motor coordination, swimming behavior, or spatial learning in several inbred strains of mice. However, it induced a small but significant effect on some sensitive behaviors.
Conclusions: A cautious approach to initiating ivermectin treatment in mice should be used for sensitive behavioral experiments.
Methods: A total of 21 (5 males, 16 females) mice (129/SvEv) were used for measuring body weight, open field locomotor activity, and rotarod motor coordination. For acoustic startle and prepulse inhibition, 20 C57BL/6J and 29 AKR/J mice were studied. For the Morris water task, the same 20 C57BL/6J mice were studied. Ivermectin (0.08% sheep drench) was administered in the drinking water of the home cage for 8 weeks. Control groups received normal tap water in identical bottles.
Results: Ivermectin did not affect general health, body weight, motor coordination, swimming behavior, or spatial learning in several inbred strains of mice. However, it induced a small but significant effect on some sensitive behaviors.
Conclusions: A cautious approach to initiating ivermectin treatment in mice should be used for sensitive behavioral experiments.
Research Interests:
Sciurus niger (Rodentia: Sciuridae) is a large tree squirrel which inhabits the southeastern portion of North America. Currently there are ten recognized subspecies which are distinguished based on differences in morphology and ecology.... more
Sciurus niger (Rodentia: Sciuridae) is a large tree squirrel which inhabits the southeastern portion of North America. Currently there are ten recognized subspecies which are distinguished based on differences in morphology and ecology. While molecular work has been undertaken for a few subspecies of S. niger, the patterns of genetic differentiation of the entire species have yet to be examined. This study attempts to characterize the genetic structure of S. niger in order to help determine the validity of current subspecies designations and offer insight into the post-glacial colonization patterns of the species. A 296 base pair fragment of the mitochondrial control region (d- loop) was sequenced from 55 specimens of S. n. vulpinus, 13 samples of S. n. niger, and 13 samples of S. n. rufiventer. Fifteen previously reported haplotypes (Lance et al. 2003) representing S. n. cinereus, S. n. rufiventer, and S. n. vulpinus were incorporated into the analysis. Additionally, a data set of 89 sequences generated at the Van Den Bussche Laboratory of Molecular Systematics and Conservation Genetics were added to this data
set. These sequences included representatives of the following 8 subspecies: S. n. bachmani, S. n. cinereus, S. n. limitis, S. n. ludovicianus, S. n. niger, S. n. rufiventer, S. n. subauratus, and S. n. vulpinus. The compiled data set of 258 individuals belonging to 8 subspecies yielded 125 unique haplotypes, indicating extremely high levels of diversity in the control region. Several tree-based methods recovered two distinct shallow clades which do not correspond to geographic regions or subspecies. A parsimony-based minimum spanning network revealed two haplotype clusters which correspond to the two clades found in the tree-based methods. The haplotypes are closely linked in a star- shaped phylogenetic network; several of the most frequent haplotypes were internal, while the majority were unique to single populations and presented distal positions in the network. Overall there was a lack of genetic structure amongst populations with most of the variance explained by within population genetic diversity. Despite poor branch support, the congruent recovery of the two S. niger clades via both clustering-based and optimality criterion-based methods supports the separation of haplotypes into two major haplogroups. These results indicate that the currently recognized subspecies based on alpha taxonomic characters are not concordant with the mitochondrial history of S. niger. Instead, my findings suggest that the control region haplotype distribution in fox squirrels may be the result of repeated and rapid habitat expansions/retractions during glacial events in the Pleistocene. The shallow divergence between haplotypes across wide geographic distances suggest that the patterns of morphological and ecological differentiation the we observe within S. niger may have occurred much more recently than previously thought.
set. These sequences included representatives of the following 8 subspecies: S. n. bachmani, S. n. cinereus, S. n. limitis, S. n. ludovicianus, S. n. niger, S. n. rufiventer, S. n. subauratus, and S. n. vulpinus. The compiled data set of 258 individuals belonging to 8 subspecies yielded 125 unique haplotypes, indicating extremely high levels of diversity in the control region. Several tree-based methods recovered two distinct shallow clades which do not correspond to geographic regions or subspecies. A parsimony-based minimum spanning network revealed two haplotype clusters which correspond to the two clades found in the tree-based methods. The haplotypes are closely linked in a star- shaped phylogenetic network; several of the most frequent haplotypes were internal, while the majority were unique to single populations and presented distal positions in the network. Overall there was a lack of genetic structure amongst populations with most of the variance explained by within population genetic diversity. Despite poor branch support, the congruent recovery of the two S. niger clades via both clustering-based and optimality criterion-based methods supports the separation of haplotypes into two major haplogroups. These results indicate that the currently recognized subspecies based on alpha taxonomic characters are not concordant with the mitochondrial history of S. niger. Instead, my findings suggest that the control region haplotype distribution in fox squirrels may be the result of repeated and rapid habitat expansions/retractions during glacial events in the Pleistocene. The shallow divergence between haplotypes across wide geographic distances suggest that the patterns of morphological and ecological differentiation the we observe within S. niger may have occurred much more recently than previously thought.
Although scientific researchers and clinicians are often ill-equipped to comment on the concept of identity qua humanistic term, identity claims do happen descriptively and normatively when neuroscientists and neurologists make scientific... more
Although scientific researchers and clinicians are often ill-equipped to comment on the concept of identity qua humanistic term, identity claims do happen descriptively and normatively when neuroscientists and neurologists make scientific claims Variation in human experience is unavoidable – and is in fact, an essential part of our nature. But when experiences stray far enough from the average, they are often labeled as pathological. Here, I will present the case of synesthesia – a nosological category that groups together a suite of atypical variations in the experience of perceptual phenomena, and which was originally believed to be a form of mental illness. Synesthetes are individuals who experience unusual sensory pairings; for example, sounds may evoke colors, tastes may evoke textures, and numbers may evoke spatial representations, to name just a few. After some initial scientific descriptions at the turn of the 20th century, these phenomena were largely forgotten, and reports of sensory “cross chatter” were often dismissed as highly imaginative fabrications, or interpreted as symptoms of schizophrenia. More recently, several contemporary neuroscientists have reintroduced to the scientific community as an interesting neurological “condition”, rather than a distressing pathology. However, this new label still implicates synesthetes as distinctly different from “neurotypical” non-synesthetes. In this paper, I will critically examine the claim that synesthesia is a non-normal form of human variation. First, I will discuss the perceptual and neurological features of synesthesia, including firsthand subjective reports of synesthetic phenomena. Although synesthetic experiences blur the usually rigid boundaries of perceptual modalities and conceptual categories in ways that seem arbitrary, I will argue that synesthetic experience offers a new framework for understanding how non-synesthete, or “normal” perceptual and conceptual processing are constituted. Indeed, I will propose that although different from normal perception, synesthetic perceptions may be the manifestation of an extreme end of a continuum of human variation, in which implicit cross-sensory linkages “break through” into explicit perception. Finally, I will discuss how implicit synesthetic processes in non-synesthetes may impact explicit cognitive processes – suggesting that the “abnormal” condition of synesthesia is in fact a normal, integral part of internal mental states across the continuum of variation.
Vesicular glutamate transporters (VGluTs) reuptake glutamate into synaptic vesicles at excitatory synapses. Antibodies for VGluT2 are a useful marker for cortical terminals arising from sensory nuclei of the thalamus. Thus, immunolabeling... more
Vesicular glutamate transporters (VGluTs) reuptake glutamate into synaptic vesicles at excitatory synapses. Antibodies for VGluT2 are a useful marker for cortical terminals arising from sensory nuclei of the thalamus. Thus, immunolabeling of sensory cortex allows for the examination of likely geniculostriate terminal distributions in species in which connectivity cannot be studied with tract-tracing techniques, permitting broader comparative studies of cortical specializations. We investigated the organization of geniculostriate afferents in primary visual cortex (V1) in humans, chimpanzees, Old World monkeys, and New World monkeys. Cryopreserved occipital lobe tissue sections containing V1 from humans (n=6), chimpanzees (Pan troglodytes; n=4), an orangutan (Pongo pygmaeus), rhesus macaques (Macaca mulatta; n=3), a cynomolgus monkey (Macaca fascicularis), vervets (Cercopithecus aethiops; n=3), and squirrel monkeys (Saimiri sciureus; n=3) were immunoreacted with antibodies for VGluT2. All species exhibited dense, terminal-like labeling in layer 4C and layer 6, consistent with known distributions of geniculocortical projections in primates. In addition, all the hominoid primates_chimpanzees, the orangutan, and humans showed a reduction of terminal-like labeling in layer 4A, being sparse to absent in comparison to the dense, intermittent distribution seen in the New World and Old World monkeys. These findings are consistent with previous observations of modifications to V1 layer 4A in humans and chimpanzees following the evolutionary split between hominoids and other primates. Human tissue sections had an additional reduction of staining in layer 6. These results confer additional support for the use of VGluT2 antibody as a means to identify cortical areas in other modalities that receive projections from thalamic sensory relay nuclei.
Chimpanzee are the animals most closely related to humans, and therefore understanding how the two species resemble, and differ from, one another is crucial for understanding the evolutionary specializations of the brain. Chimpanzee... more
Chimpanzee are the animals most closely related to humans, and therefore understanding how the two species resemble, and differ from, one another is crucial for understanding the evolutionary specializations of the brain. Chimpanzee neuroanatomy is very poorly known, however - in part because, like humans, they cannot be studied with invasive techniques. The development of noninvasive neuroimaging, and in particular diffusion-tensor imaging (DTI), which can track fiber pathways, has made direct studies of chimpanzees possible and, consequently, more detailed comparisons of humans, chimpanzees, and other nonhuman primates. The acuity of these comparisons depends on how well one can track cortical connections and localize cortical areas in chimpanzees with DTI. To evaluate the potential of DTI, we performed probabilistic tractography on in vivo chimpanzee DTI scans to localize two major cortical landmarks: 1) the auditory core, a primary sensory area with major inputs from the thalamus; and 2) the MT+ complex, a multimodal association area. Based on recent comparative myeloarchitectonic studies (Glasser et al., 2011, Soc. Neurosci. Abstr. 290.05; Hackett et al., 2001, J. Comp. Neurol. 441:197-222), we hypothesized that 1) the auditory core of the chimpanzee would be localized in Heschl’s gyrus; and 2) the MT+ complex would be localized in the posterior part of the superior temporal sulcus (STS). Methods. We drew region-of-interest (ROI) masks that included the hypothesized locations of the two landmark regions on MT+ on T1-weighted images with 0.8-mm isotropic resolution. ROI masks were also drawn on known inputs to the auditory core (medial geniculate nucleus) and area MT (intraparietal sulcus (IPS), primary visual cortex (V1), and area V2. Probabilistic tractography software within FSL (www.fmrib.ox.ac.uk/fsl) was used to track cortico-cortical and subcortical connections in diffusion-weighted scans acquired with 1.8 mm isotropic resolution with 60 gradient directions and b values of 0, 1000s/mm2. Results. First, MGN projections to cortex were localized in Heschl's gyrus, indicative of the auditory core. Second, tracts from IPS and V1/V2 converged in a small gyrus buried in the posterior STS, indicative of a macaque-like position of area MT+ rather than in a human-like position, corroborating MT+ localization by Glasser and co-workers (2011). We conclude that DTI and probablistic tractography can contribute to the construction of a detailed map of chimpanzee cortical organization.
Geordi LaForge's VISOR from the Star Trek: TNG series is emblematic as a vision for future scientific breakthroughs in both human sensory replacement and sensory enhancement. How do these iconic roles measure up against current... more
Geordi LaForge's VISOR from the Star Trek: TNG series is emblematic as a vision for future scientific breakthroughs in both human sensory replacement and sensory enhancement. How do these iconic roles measure up against current neuroscientific understandings of visual processing, and the likely realities of visual-technological interfaces? First, recent advances in bionic eyes, including both retinal and cortical implants will be examined and compared to the features of Geordi's VISOR. How is the putative neural interface of the VISOR similar or different from current approaches to visual prostheses? Second, the enhancement of visual perception from the VISOR will be discussed in the context of known features of visual processing. What is the plausibility of cortical processing of non-visible forms of electromagnetic radiation? What, if any, kinds of sensory enhancement are possible? Lastly, the viability and likelihood of a VISOR-like prosthesis being realized will be explored.
The past decade has seen scientists come closer to realizing the dream of artificial intelligence (AI). The character of Data in Star Trek: The Next Generation was prescient in many ways. However, recent developments in neuroscience,... more
The past decade has seen scientists come closer to realizing the dream of artificial intelligence (AI). The character of Data in Star Trek: The Next Generation was prescient in many ways. However, recent developments in neuroscience, cognitive psychology, and artificial intelligence have uncovered new understandings into both the theory and engineering of AI, some of which contradict the TNG schema. In this talk, I will discuss examples of Data's personality traits and functioning and compare these to our current knowledge: how well does this model hold up? Further, I will speculate whether an android like Data is in our future.
Female students achieve at significant levels in biomedical sciences (earning 59% of bachelor degrees), but less so in math-intensive STEM fields (earning 18% of degrees in computer science, for example; NCES, 2014). Explanations range... more
Female students achieve at significant levels in biomedical sciences (earning 59% of bachelor degrees), but less so in math-intensive STEM fields (earning 18% of degrees in computer science, for example; NCES, 2014). Explanations range from gender differences in abilities, interests, and motivation to encounters with stereotype and bias in the classroom (see Wang & Degol, 2017, for a review). A sense of belonging in the classroom, engagement and comfort with the material, and self-efficacy predict achievement in STEM fields, particularly for females (e.g., Cheryan et el., 2009). Further, an incremental theory of intelligence (growth mindset as opposed to fixed) predicts persistence and academic achievement in males and females across adolescence in a variety of fields (Rattan et al., 2015). However, recent studies raise doubts about whether a growth mindset predicts achievement in CS1 (introductory computer science; Scott & Ghinea, 2014). It is also not clear how these variables relate to each other among CS1 college students. We measured mindset (Dweck, 2006) and sense of belonging (Good et al., 2012) at the beginning of the semester and total points earned at the end of the semester in 430 college students (190 females) enrolled in CS1 at a highly selective private college. In a subset (N=329, 137 females) we also measured engagement (Authors, 2016), comfort (Wilson & Shrock, 2001), and self-efficacy for programming (Ramalingam & Wiedenbeck, 1998) in the middle and at the end of the semester. Data were collected over three semesters during 2017 and 2018. At the beginning of the course, females scored significantly lower than males on belonging, but similarly on mindset. At midterm (but not end of term) females scored significantly lower on comfort and self-efficacy. There were no gender differences in engagement at any time, and there were no differences in points earned at the end of the term (Table 1). Nine variables were included in a regression model that explained 33% of the variance in points earned (Table 2). Age and growth mindset negatively predicted achievement; engagement at midterm positively predicted achievement as did comfort and self-efficacy at the end of term. These results suggest that although female students felt less belonging, comfort, and self-efficacy at first, they were equally engaged throughout the course, and by the end of term felt equally comfortable and efficacious and achieved equally with males. Questions remain about whether the gender differences observed are related to persistence in the field, despite the equal performance, and whether the age of the students also correlates with an interest in math-intensive fields. Growth mindset was negatively correlated with achievement, and this raises questions for further exploration. Are consistently high-achieving students (perhaps with a belief in their inherent intelligence) more likely to enroll in CS? Does the frequent feedback about success (or failure) of programming attempts in CS courses favor those with a fixed (and positive) view of their abilities? Answers to these questions may lead to pedagogical interventions that enhance learning and persistence in CS for all students.
Research Interests:
What effects do designated spaces for activism in university campuses such as "free speech zones" have on dissent? What kinds of social justice topics are deemed acceptable for discussion? Which ones are threatening? How can we employ... more
What effects do designated spaces for activism in university campuses such as "free speech zones" have on dissent? What kinds of social justice topics are deemed acceptable for discussion? Which ones are threatening? How can we employ creative forms of activism and public scholarship to raise awareness? Using the organizing work around #EmoryCuts as a starting point, graduate student members of the Student Re-visioning Committee (SRC) and the Visual Scholarship Initiative (VSI) at Emory will discuss issues of organizing and activism, exploring creative possibilities for future action and meaningful change on campus.
This talk examined some recent interpretations of the role of the temporal lobe in behavior, as well as how this informs my current dissertation research on temporal lobe structure.
This talk examined what synesthesia is, and what kind of variability exists in the synesthetic population. Synesthesia as a phenomenon appears to exist in a spectrum in terms of intensity of experience as well an axis of variation which... more
This talk examined what synesthesia is, and what kind of variability exists in the synesthetic population. Synesthesia as a phenomenon appears to exist in a spectrum in terms of intensity of experience as well an axis of variation which appears to track from purely sensory up to higher level cognitive/semantic constructs.