Temporal lobe white matter asymmetry and language laterality in epilepsy patients.

Recent studies using diffusion tensor imaging (DTI) have advanced our knowledge of the organization of white matter subserving language function. It remains unclear, however, how DTI may be used to predict accurately a key feature of language organization: its asymmetric representation in one cerebral hemisphere. In this study of epilepsy patients with unambiguous lateralization on Wada testing (19 left and 4 right lateralized subjects; no bilateral subjects), the predictive value of DTI for classifying the dominant hemisphere for language was assessed relative to the existing standard-the intra-carotid Amytal (Wada) procedure. Our specific hypothesis is that language laterality in both unilateral left- and right-hemisphere language dominant subjects may be predicted by hemispheric asymmetry in the relative density of three white matter pathways terminating in the temporal lobe implicated in different aspects of language function: the arcuate (AF), uncinate (UF), and inferior longitudinal fasciculi (ILF). Laterality indices computed from asymmetry of high anisotropy AF pathways, but not the other pathways, classified the majority (19 of 23) of patients using the Wada results as the standard. A logistic regression model incorporating information from DTI of the AF, fMRI activity in Broca\u27s area, and handedness was able to classify 22 of 23 (95.6%) patients correctly according to their Wada score. We conclude that evaluation of highly anisotropic components of the AF alone has significant predictive power for determining language laterality, and that this markedly asymmetric distribution in the dominant hemisphere may reflect enhanced connectivity between frontal and temporal sites to support fluent language processes. Given the small sample reported in this preliminary study, future research should assess this method on a larger group of patients, including subjects with bi-hemispheric dominance

Hair Whorls in the Dog (Canis familiaris), Part II: Asymmetries

In horses and cattle, hair whorls have been shown to act as a structural marker of reactivity and behavioral lateralization. Few studies on canine whorls have been reported and none have assessed whorl position or direction of flow. This study describes the distribution and characteristics of whorl in each of 10 regions in which whorls are typically located in dogs. Hair whorls were assessed in dogs (n = 120) and were recorded as clockwise or counterclockwise in the cephalic, cervical (dorsal, lateral, ventral), thoracic and brachial axillary, chest, shoulders, elbows, abdominal, and ischiatic regions. Bilateral whorls, including brachial axillary, elbow, abdominal and ischiatic whorls, rotated in opposing directions, allowing the dog\u27s overall hair coat to be symmetrical. Cephalic, brachial axillary, and ischiatic whorls were consistent in their direction; cephalic and ischiatic whorls were clockwise on the right side of the body, and counterclockwise on the left, whereas right brachial axillary whorls were counterclockwise and left were clockwise. The central chest whorl was predominantly counterclockwise (91.21%). Direction of whorls was associated with several factors, including coat length, coat thickness, sex and source of the dog

Hair Whorls in the Dog (Canis familiaris), Part II: Asymmetries

In horses and cattle, hair whorls have been shown to act as a structural marker of reactivity and behavioral lateralization. Few studies on canine whorls have been reported and none have assessed whorl position or direction of flow. This study describes the distribution and characteristics of whorl in each of 10 regions in which whorls are typically located in dogs. Hair whorls were assessed in dogs (n = 120) and were recorded as clockwise or counterclockwise in the cephalic, cervical (dorsal, lateral, ventral), thoracic and brachial axillary, chest, shoulders, elbows, abdominal, and ischiatic regions. Bilateral whorls, including brachial axillary, elbow, abdominal and ischiatic whorls, rotated in opposing directions, allowing the dog\u27s overall hair coat to be symmetrical. Cephalic, brachial axillary, and ischiatic whorls were consistent in their direction; cephalic and ischiatic whorls were clockwise on the right side of the body, and counterclockwise on the left, whereas right brachial axillary whorls were counterclockwise and left were clockwise. The central chest whorl was predominantly counterclockwise (91.21%). Direction of whorls was associated with several factors, including coat length, coat thickness, sex and source of the dog

Isolation and Genetic Characterization of Mother-of-Snow-White, a Maternal Effect Allele Affecting Laterality and Lateralized Behaviors in Zebrafish

In the present work we report evidence compatible with a maternal effect allele affecting left-right development and functional lateralization in vertebrates. Our study demonstrates that the increased frequency of reversed brain asymmetries in a zebrafish line isolated through a behavioral assay is due to selection of mother-of-snow-white (msw), a maternal effect allele involved in early stages of left-right development in zebrafish. msw homozygous females could be identified by screening of their progeny for the position of the parapineal organ because in about 50% of their offspring we found an altered, either bilateral or right-sided, expression of lefty1 and spaw. Deeper investigations at earlier stages of development revealed that msw is involved in the specification and differentiation of precursors of the Kupffer's vesicle, a structure homologous to the mammalian node. To test the hypothesis that msw, by controlling Kupffer's vesicle morphogenesis, controls lateralized behaviors related to diencephalic asymmetries, we analyzed left- and right-parapineal offspring in a “viewing test”. As a result, left- and right-parapineal individuals showed opposite and complementary eye preference when scrutinizing a model predator, and a different degree of lateralization when scrutinizing a virtual companion. As maternal effect genes are expected to evolve more rapidly when compared to zygotic ones, our results highlight the driving force of maternal effect alleles in the evolution of vertebrates behaviors

Hair Whorls in the Dog (Canisfamiliaris). I. Distribution

Hair whorl characteristics were assessed in the domestic dog (Canis familiaris) in the regions of cephalic, cervical (dorsal, ventral, and lateral), thoracic and brachial axillary regions, the chest, shoulders, elbows, ventral abdominal region, and on the caudal thighs (ischiatic). They were classified as simple or tufted, and their position was recorded as the distance between their centers and bony landmarks within each region. The distribution of whorls was explored in a cohort of domestic dogs (N = 120) comprising a variety of breeds and cross‐breeds, sourced from shelters (N = 60) and the general public (N = 60). Whorls observed in the majority of dogs in this cohort typically occurred on the chest, brachial axillary region, elbows, and ischiatic region. Atypical whorls were present in fewer than 20% of the population, and included those on the head (cephalic), cervical regions (dorsal, ventral, and lateral), shoulders, thoracic axillary region, and on the ventral abdominal region. The majority of whorls on dogs were classified as simple. In contrast, those located on the elbows and the majority of chest whorls were tufted. The presence and position of whorls were often associated with several variables including coat length and thickness, and the sex and source of the dog. The palpation and hair‐cluster method of whorl assessment described in this article is best suited to dogs with short‐to‐medium coat lengths. The current methodology developed to assess hair whorl characteristics provides a framework for future investigations into any associations between hair whorl characteristics and other canine traits such as temperament

Quantifying cerebral asymmetries for language in dextrals and adextrals with random-effects meta analysis

Speech and language-related functions tend to depend on the left hemisphere more than the right in most right-handed (dextral) participants. This relationship is less clear in non-right handed (adextral) people, resulting in surprisingly polarized opinion on whether or not they are as lateralized as right handers. The present analysis investigates this issue by largely ignoring methodological differences between the different neuroscientific approaches to language lateralization, as well as discrepancies in how dextral and adextral participants were recruited or defined. Here we evaluate the tendency for dextrals to be more left hemisphere dominant than adextrals, using random effects meta analyses. In spite of several limitations, including sample size (in the adextrals in particular), missing details on proportions of groups who show directional effects in many experiments, and so on, the different paradigms all point to proportionally increased left hemispheric dominance in the dextrals. These results are analyzed in light of the theoretical importance of these subtle differences for understanding the cognitive neuroscience of language, as well as the unusual asymmetry in most adextrals

An investigation into the validation of pedometers to detect foreleg steps in horses (Equus caballus) at walk and trot

Background: Current research, surrounding motor laterality at a population level in horses, indicates that in order to stand with the left forelimb in advance of the other, it is achieved by taking a greater amount of steps with the left foreleg than the right foreleg (McGreevy & Thomson 2006; McGreevy et al. 2007); suggesting that pedometers could effectively estimate asymmetry of forelimb locomotion in grazing horses. This novel method of detecting forelimb preference also reduces the likelihood of operator influence and provides an inexpensive objective measure of vertical movement which has the advantage of scoring large sample sizes, avoids single-day anomalies by recording over multiple days and overcomes logistical challenges (Vincent & Sidman 2003; Chan et al. 2005; Silva et al. 2010; Warren-Smith & McGreevy 2010). However in order to determine the reliability and validity of this novel measure the relationship between pedometer data and those derived from direct observation will first need to be assessed (Warren-Smith and McGreevy 2010). Objectives: To determine: (1) if pedometers accurately record equine steps at walk and trot, when compared to video analysis, (2) if alternative positioning of these pedometers affected the accuracy of step detection when compared to video analysis. Method: Five horses each wearing a Yamax Digiwalk SW-200 (spring lever arm pedometer) and a Yamax Power Walker PW-610/611 (piezoelectric pedometer) positioned on the left foreleg (LF), left scapular (LS), chest (C), right scapular (RS) and right foreleg (RF) walked and trotted on a 20m circle 10 times on each rein to yield 100 results for each gait. Video recorded by GoPro Hero 3 Black edition camera positioned on the girth facing the forefeet using the following settings: 180 degree field of view, 720p, 120fps. Both visual and audio data were captured and recorded. Results: Kruskal-Wallis Test on the deviation from actual number of steps per unit for each type of pedometer and the position of the pedometer compared to the actual number of steps taken by both forelegs determined that there is a significant difference (H1= 340.31; P<0.0001) between readings in walk and also in trot (H1 = 483.49; P<0.0001). A further Kruskal-Wallis Test on the deviation from actual number of steps per unit for each type of pedometer and the position of the pedometer compared to the actual number of steps taken by individual forelegs determined that there is a significant difference (H = 403.36; p<0.0001) at walk and also at trot (H = 477.10; p<0.0001). Conclusion: In summary, the analysis of the pedometer data compared to video analysis indicate that pedometers are not useful for scoring forelimb movements in horses at walk and trot, regardless of positioning

Upper Limb Asymmetries in the Utilization of Movement-related Sensory Feedback.

While the preferred arm of right handed individuals has traditionally been viewed as being dominant with respect to motor output, non-preferred arm advantages have recently been described by this laboratory for the matching of target arm positions in the absence of vision. The aim of this dissertation, therefore, was to determine the extent to which this asymmetry reflects arm differences in the utilization of movement-related feedback. To accomplish this, three matching experiments were conducted using servomotor-driven manipulanda devices that recorded elbow position in the horizontal plane. In study 1, a comparison was made between the static position matching abilities of the two arms during visually versus proprioceptively-guided tasks. In this case, non-preferred arm accuracy was found to be enhanced during the proprioceptive task, whereas the preferred arm made smaller errors when targets were visual in nature. In study 2, arm differences in the ability to match proprioceptively-determined target movement speeds were assessed. This study showed that, unlike the sense of arm position, the acuity of dynamic proprioception sense was relatively similar for the two arms, except in the case of average acceleration matching where a non-preferred arm accuracy advantage was seen. Lastly, in the third study, the ability to coordinate both arm position and movement speed proprioceptive information was tested. In this case, absolute matching errors were again smaller for the non-preferred versus preferred arm. Overall, the results of this dissertation lend support to the notion that the two arms rely to different degrees on visual versus proprioceptive feedback. This asymmetry may reflect the roles played by the two arms during the performance of many bimanual activities of daily living where vision guides movements of the preferred arm, while the non-preferred arm plays a more assistive role utilizing primarily proprioceptive feedback.Ph.D.KinesiologyUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/57702/2/dgoble_1.pd

Building an Asymmetrical Brain: The Molecular Perspective

The brain is one of the most prominent examples for structural and functional differences between the left and right half of the body. For handedness and language lateralization, the most widely investigated behavioral phenotypes, only a small fraction of phenotypic variance has been explained by molecular genetic studies. Due to environmental factors presumably also playing a role in their ontogenesis and based on first molecular evidence, it has been suggested that functional hemispheric asymmetries are partly under epigenetic control. This review article aims to elucidate the molecular factors underlying hemispheric asymmetries and their association with inner organ asymmetries. While we previously suggested that epigenetic mechanisms might partly account for the missing heritability of handedness, this article extends this idea by suggesting possible alternatives for transgenerational transmission of epigenetic states that do not require germ line epigenetic transmission. This is in line with a multifactorial model of hemispheric asymmetries, integrating genetic, environmental, and epigenetic influencing factors in their ontogenesis

Why laterality matters in trauma: sinister aspects of memory and emotion

This thesis presents an eclectic mix of studies which consider laterality in the context of previous findings of increased prevalence of Posttraumatic Stress Disorder (PTSD) in male combat veterans with non-consistent right hand preference. Two studies extend these findings not just to civilian populations and women, but to left handers and find that left, rather than mixed, handedness is associated with increased prevalence of PTSD in both general population and clinical samples, and to severity of symptoms in the former. To examine issues relevant to the fear response in healthy populations, a movie excerpt is shown to be theoretically likely to target the emotion of fear and to generate subjective and physiological (skin conductance) responses of fear. The film is used as a laboratory analogue of fear to examine possible differences in left and right handers in memory (for events of the film) and in an emotional Stroop paradigm known to produce a robust and large effect specifically in PTSD. According to predictions based on lateralisation of functions in the brain relevant to the fear response, left handers show a pattern of enhanced memory for visual items and poorer memory for verbal material compared to right handers. Immediately after viewing the film, left handers show an interference effect on the Stroop paradigm to general threat and film words and increased response latency compared to right handers, approaching performance of previously reported clinical samples with PTSD. A novel non-word Stroop task fails to show these effects, consistent both with accounts of interference as language processing effects and compromised verbal processing in PTSD. Unexpected inferior performance of females in memory for the film, contrary to previous literature, may also be amenable to explanations invoking compromised left hemisphere language functions in fear situations. In testing one theory of left handedness as due to increased levels of in utero testosterone, the 2D:4D (second to fourth digit ratio) provides mixed evidence in two samples. A possible association of more female-like digit ratios in males with PTSD is a tentative finding possibly relevant to sex differences in prevalence of PTSD. A critique of existing and inadequate theoretical accounts of handedness concludes the thesis and proposes a modification of the birth stress hypothesis to one specifically considering peri-natal trauma to account for the above findings. This hypothesis remains to be empirically tested