Bilateral skin temperature,handedness, and the biofeedback control of skin temperature

There are differences in physiological variables when they are recorded from the left and right side of the body simultaneously. In some cases, handedness has been found to have a significant relationship to bilateral differences. The present study examined the relationship between handedness and baseline heart rate and skin temperature, as well as bilateral differences in skin temperature during visual and auditory biofeedback. Subjects were 32 college females, 24 right-handed and 8 left-handed. Recordings of heart rate and skin temperature from both the dominant and the nondominant hand were made during baseline and during the 10-min experimental session while subjects attempted to warm their dominant hand. Both groups showed significantly increased skin temperature during the experimental session. No prominent bilateral differences in skin temperature were found. These results do not support bilateral differences as a generalizable construct.This work was supported in part by funds provided by The University of North Carolina at Charlotte.     

Effect of ambient temperature on the thermal profile of the human forearm,hand, and fingers

Forearm, hand, and finger skin temperatures were measured on the right and left sides of seven resting men. The purpose was to determine the bilateral symmetry of these segmental temperature profiles at ambient temperatures from 10 to 45°C. Thermistors placed on the right and left forearms, hands, and index fingers were used to monitor the subjects until equilibration was reached at each ambient temperature. Additionally, thermal profiles of both hands were measured with copper-constantan thermocouples. During one experimental condition (23°C ambient), rectal, ear canal, and 24 skin temperatures were measured on each subject. Average body and average skin temperatures are given for each subject at the 23°C ambient condition. Detailed thermal profiles are also presented for the dorsal, ventral, and circumferential left forearm, hand, and finger skin temperatures at 23°C ambient. No significant differences were found between the mean skin temperatures of the right and left contralateral segments at any of the selected ambient temperatures.     

Bilateral Asymmetry of Skin Conductance Responses During Auditory and Visual Tasks

Bilateral skin conductance (SC) was recorded while dextral subjects engaged in tasks designed to differentially engage the right (RH) and left (LH) hemispheres. Subjects compared strings of speech sounds (LH) and musical chords (RH). They also decided whether written words rhymed (LH) and viewed pictures of faces in a continuous recognition paradigm (RH). SCRs in the right hand were larger during the chords task than the syllables task. The left hand did not differ for the two stimuli. In the visual experiment a comparable effect was obtained in males only. SCRs in the left hand were larger for rhymes than faces; the right hand did not differentiate between stimuli. Sex differences in laterality are considered. Subjects who were more equally balanced in awareness of the two sides of their bodies and subjects with familial sinistrals were more likely to show task appropriate SC changes. Using rote repetition and visual imagery as mnemonics did not affect SC asymmetries.     

Degree of language lateralization determines susceptibility to unilateral brain lesions

Language is considered a function of either the left or, in exceptional cases, the right side of the brain. Functional imaging studies show, however, that in the general population a graded continuum from left hemispheric to right hemispheric language lateralization exists. To determine the functional relevance of lateralization differences, we suppressed language regions using transcranial magnetic stimulation (TMS) in healthy human subjects who differed in lateralization of language-related brain activation. Language disruption correlated with both the degree and side of lateralization. Subjects with weak lateralization (more bilaterality) were less affected by either left- or right-side TMS than were subjects with strong lateralization to one hemisphere. Thus in some people, language processing seems to be distributed evenly between the hemispheres, allowing for ready compensation after a unilateral lesion.     

The prevalence of absence of the palmaris longus muscle in the Bahraini population

Absence of the palmaris longus muscle has been well documented in several populations at a prevalence rate ranging between 2.2 and 63.9% which varies according to race, sex, and side of the body. There is little documentation of the prevalence of absence of this muscle from populations in the Arabian Gulf region. We examined 1,043 subjects, 3-85 years old, from the Kingdom of Bahrain for the presence or absence of the palmaris longus muscle using the conventional test for the presence of this muscle. Statistical analyses investigated the association of muscle absence with sex, hand dominance, and laterality. The palmaris longus muscle was absent in 36.8% of subjects. Bilateral absence (19%) was more common than unilateral absence (17.9%) with preponderance in female subjects. The muscle was absent more often on the left side than the right (P = 0.003). In the right upper limbs the muscle was absent in female subjects more than male subjects (P = 0.031). This study reaffirms that there is population variation in the frequency of absence of the palmaris longus muscle. The tendon of the palmaris longus bifurcated at the wrist in 7.1% of subjects, with male subjects showing this feature more frequently than female subjects in the right hand (P = 0.037) and the left hand (P = 0.030). This has not been reported before. The clinical significance of our findings is discussed.     

Brain interleukin asymmetries and paw preference in mice

The two sides of the brain are differently involved in the modulation of immune responses as demonstrated by lesion and behavioral approaches. To study the interactions between cerebral cortex cytokines and brain lateralization, three groups of BALB/c mice were selected on the basis of their performance in the paw preference test (left-pawed, ambidextrous and right-pawed) and the levels of interleukin-1beta and interleukin-6 were measured in the two cerebral cortices after an intraperitoneal saline or lipopolysaccharide. Generally, right cortices had higher interleukin-1beta and interleukin-6 levels than left cortices for both saline and lipopolysaccharide-treated mice. A strong correlation between the levels of interleukin-1beta and interleukin-6 in right and left cortices and behavioral lateralization was observed. For the saline-treated mice: in their left cortices, interleukin-1beta levels were higher for ambidextrous mice than for right-pawed mice (P<0.05); in their right cortices, interleukin-6 levels were higher for ambidextrous mice than for right-/left-pawed mice, and right-pawed mice have higher levels of interleukin-6 than left-pawed mice (P<0.01). In their left cortices, interleukin-6 levels are higher for left-pawed mice than for both ambidextrous and right-pawed mice (P<0.01). In their left cortices, interleukin-6 levels are higher for left-pawed mice than for both ambidextrous and right-pawed mice (P<0.01). The quadratic curve equations showed that the levels of interleukin-1beta and interleukin-6 in the right/left cortices had a highly significant correlation with paw preference scores in both normal and lipopolysaccharide-treated mice. In conclusion, the present report demonstrated that the basal levels of interleukin-1beta and interleukin-6 were higher in the right cortex than left cortex in mice. There was a strong correlation between the levels of interleukin-1beta and interleukin-6 and behavioral lateralization, and cytokine asymmetries had a strong correlation with the direction and the intensity of behavioral lateralization.     

Left hand, but not right hand, reaching is sensitive to visual context

Recently, it has been reported that grasping with the left hand is more vulnerable to visual size illusions than grasping with the right hand. The present study investigated whether this increased sensitivity of the left hand for visual context extends to reaching. Left- and right-handed participants reached for targets embedded in two different visual contexts with either left or right hands. Visual context was manipulated by presenting targets either in a blank field or within an array of placeholders marking possible target locations. Regardless of handedness, the presence of placeholders affected left hand, but not right hand, reaching by improving end-point accuracy and reducing movement speed. Furthermore, left hand reaching was more accurate for far than near targets, whereas right hand reaching showed the opposite pattern. We discuss two possible hemispheric lateralization accounts of these findings.     

Guidance of visual direction by topographical vibrotactile cues on the torso

Vibration on localised areas of skin can be used to signal spatial orientation, multi-directional motion and also to guide arm and hand movements. This study investigated the possibility that vibration at loci on the skin might also be used to cue gaze direction. Eight subjects made eye or (head + eye) gaze saccades in the dark cued by vibration stimulation at discrete loci spaced on a horizontal contour across the chest. Saccade and gaze amplitudes, latencies, and directions were analysed. In the first experiment, performed without training, subjects could only use vibration cues to direct their gaze in cardinal directions and gross quadrature. There was a high variability in the relationship between locus on the trunk and gaze direction in space, both within and between subjects. Saccade latencies ranged from 377 to 433 ms and were related to the loci of vibration; the further from the body midline the quicker the response. Since the association of skin loci with gaze direction did not appear intuitive a sub-group of four subjects were retested after intensive training with feedback until they attained criterion on midline ≡ 0° and 15 cm (to right/left of midline) ≡ 45° gaze shifts right and left. Training gave a moderate improvement in directional specificity of gaze to a particular locus on the skin. Gaze direction was linearly rescaled with respect to skin loci but variability and saccade latencies remained high. The uncertainty in the relationship between vibration locus and gaze direction and the prolonged latencies of responses indicate circuitous neuronal processing. There appears to be no pre-existing stimulus-response compatibility mapping between loci on the skin and gaze direction. Vibrotactile cues on the skin of the trunk only serve a gross indication of visual direction in space.     

Sex differences and the asymmetry of specific and non-specific electrodermal responses

Phasic electrodermal conductance responses were bilaterally recorded from 30 subjects (15 males and 15 females). After a 5-min adaptation period subjects were presented with two series of ten 80-dB tones each, with a 4-min rest period between the two series. Data from sinistrals, ambidextrous, and from subjects with familial sinistrality were excluded from statistical analysis. Males displayed more asymmetry between hands both in their non-specific and specific responses, with larger skin conductance responses on the left hand. Females showed a less marked asymmetry, with larger skin conductance responses on the right hand. Similar results were found in skin conductance levels. It was concluded that sex differences are an important variable in the study of electrodermal asymmetry.     

Bilateral Electrodermal Activity, Lateralized Cerebral Processing and Sex

The present study involved the assessment of systematic differences between skin conductance measures recorded bilaterally and concomitantly from 59 right-handed subjects while they were exposed to three types of stimuli. The stimuli were 5 min each of: a quiet period, a period of music, and a period of listening to a series of paragraphs. The music and paragraph conditions served, respectively, as operational definitions of right and left hemisphere tasks. Sex and genetic handedness were also assessed. Results showed that subjects with a family history of sinistrality gave more frequent SCRs on the left hand than on the right hand under the verbal condition, while those with entirely dextral families showed no left-right differentiation. In addition, musical stimulation produced more frequent responses in males than females, while the reverse was true for verbal stimuli. Finally, tonic SCL was higher on the right hand in males and on the left in females. Stimulation intended for a specific hemisphere did not produce significantly greater electrodermal activity on the contralateral hand.     

Responsiveness patterns and handedness differences in bilateral electrodermal asymmetry.

The aim of the present study was to examine the relationship between subjects' handedness and electrodermal asymmetry when subjects were divided according to their electrodermal Responsiveness Patterns, obtained during a stimulus-free period. Skin conductance was bilaterally recorded in a sample of 48 subjects (24 dextrals and 24 sinistrals) during the performance of two tasks (watching a film and listening to neutral tones). Subjects were divided into four groups of 12 subjects each (dextral right-hand responders, dextral left-hand responders, sinistral right-hand responders and sinistral left-hand responders). No differences were found between dextral and sinistral subjects. Orientation of electrodermal asymmetry in each Responsiveness Patterns remained constant throughout the two conditions: right-hand responders showed higher electrodermal activity on their right hand, while left-hand responders showed higher electrodermal activity on their left hand. In addition, left-hand responders showed a slower habituation rate on their left hand than on their right hand, whereas right-hand responders showed no significant differences between hands.     

Lateralization in motor facilitation during action observation: a TMS study

Action observation facilitates corticospinal excitability. This is presumably due to a premotor neural system that is active when we perform actions and when we observe actions performed by others. It has been speculated that this neural system is a precursor of neural systems subserving language. If this theory is true, we may expect hemispheric differences in the motor facilitation produced by action observation, with the language-dominant left hemisphere showing stronger facilitation than the right hemisphere. Furthermore, it has been suggested that body parts are recognized via cortical regions controlling sensory and motor processing associated with that body part. If this is true, then corticospinal facilitation during action observation should be modulated by the laterality of the observed body part. The present study addressed these two issues using TMS for each motor cortex separately as participants observed actions being performed by a left hand, a right hand, or a control stimulus on the computer screen. We found no overall difference between the right and left hemisphere for motor-evoked potential (MEP) size during action observation. However, when TMS was applied to the left motor cortex, MEPs were larger while observing right hand actions. Likewise, when TMS was applied to the right motor cortex, MEPs were larger while observing left hand actions. Our data do not suggest left hemisphere superiority in the facilitating effects of action observation on the motor system. However, they do support the notion of a sensory-motor loop according to which sensory stimulus properties (for example, the image of a left hand or a right hand) directly affect motor cortex activity, even when no motor output is required. The pattern of this effect is congruent with the pattern of motor representation in each hemisphere.     

Differential activation of face memory encoding tasks in alcohol-dependent patients compared to healthy subjects: An fMRI study

It has been hypothesized that the right hemisphere of the brain is more sensitive to alcohol-related damage than the left hemisphere. The present study tested this hypothesis, using functional MRI to determine whether the pattern for right hemispheric activity is different for alcohol-dependent patients, compared to normal healthy individuals. Two different types of memory encoding tasks were performed separately: word and face encoding for both alcohol-dependent patients and normal healthy volunteers. The data for the normal volunteers indicate that the left prefrontal region is more active during word encoding, whereas the right parahippocampal region is more active during face encoding. The results for the patient data, however, demonstrated left lateralization in the prefrontal area during word encoding, while right lateralization in the parahippocampal region during face encoding was not observed. Therefore, alcoholism appears to have no influence on left hemispheric activity, since the activation pattern was similar to that observed for normal healthy persons. However, the absence of right hemispheric lateralization in alcohol-dependent patients is consistent with the hypothesis that the right hemisphere is more vulnerable to alcohol-related damage than the left hemisphere.     

Differential Effects of Left versus Right Monaural Biofeedback for Heart Rate Increase

Cerebral lateralization in the voluntary increase of heart rate was investigated in a biofeedback experiment involving 20 right-handed female subjects randomly assigned to one of two groups: right or left ear input of stimulus and biofeedback information. The stimulus was a 1000 Hz tone which signalled the start and duration of 30 20-sec training trials. Feedback was a click presented every time an interbeat interval was shorter than a criterion established through a shaping schedule. A monetary bonus provided additional reinforcement at the end of each trial. Subjects given right ear feedback increased their heart rate significantly more than subjects given left ear feedback. The largest difference between the group means (7 bpm) was recorded after the first 20 training trials. The results are discussed in terms of hemispheric perceptual and functional differences.     

Interference asymmetry involving concurrent tasks performed by native American students

It is assumed that Native Americans are right‐hemisphere dominant and therefore need special teaching techniques. This study examined the language and spatial lateralization of monolingual English‐speaking Native American students by means of the cognitive‐manual dual‐task model. The results revealed the following asymmetric interference: greater right‐hand disruption while reading, greater left‐hand disruption while solving spatial problems, fewer words read while tapping with the right hand, and fewer spatial problems solved while tapping with the left hand. However, the “good” Native American students had normal (left‐hemisphere language/right‐hemisphere spatial) lateralization, whereas the “poor” students had atypical lateralization for righthanders, primarily involving both left‐hemisphere language and left‐hemisphere spatial function. The neurological consequence of crowding language and spatial processing into the same hemisphere is discussed. Two major conclusions are that the Native American students of this study were not right‐hemisphere dominant, and that nonnormal language/special lateralization resulted in learning problems, possibly suggesting a new subclassification within the special education/handicapping condition of learning disabilities.     

Some pathophysiological aspects of vibration-induced white finger

Summary The level of sympathetic nervous activity was assessed by evaluating cardiovascular responses to a cold test in 63 vibration-exposed workers (50 subjects without vibration white finger (VWF) and 13 subjects at stages 1 and 2 of VWF) and in 41 controls. Blood pressure, heart rate, systolic time intervals and the skin temperature of the third finger of the right hand were monitored throughout the cold test period. Basal urinary excretion of free catecholamines and platelet aggregation indices both in vitro and in vivo were also determined in all subjects. Systolic time intervals such as electromechanical systole index (QS₂I) and left ventricular ejection time index (LVETI) were found to be shorter in the vibration-exposed workers with and without VWF than in the controls, both at rest and during cold exposure and recovery (p<0.001). A significant inverse relationship between urinary free catecholamines and the duration of LVETI was observed under resting conditions (p<0.03). The recovery rate of the basal finger skin temperature after local cooling was slower in vibration workers with VWF than in those without VWF (p<0.05) and in the controls (p<0.001). Platelet aggregation indices were similar in all groups studied. The results suggest that the level of sympathetic nervous activity is higher in vibration-exposed workers than in controls. In subjects with VWF, sympathetic hyperactivity in combination with local factors such as vibration-induced hyperresponsiveness to cold of the digital vessels may be responsible for finger blanching attacks. The normal platelet aggregation tests, moreover, indicate that stages 1 and 2 of VWF are characterized by vascular disorders of functional origin.     

The Relationship between Exposure to Missiles and PTSD Symptoms as a Function of Hemispheric Preference in Israelis

Recent research proposes that left hemispheric lateralization (HL) may protect against the effects of life events on mental distress. This study extends these findings by examining the protective role of left HL in the relationship between war threat (missile exposure) and PTSD symptoms. A sample of 186 Israelis, exposed to missile attacks, completed brief scales of self-reported missile exposure, a subjective and a neuropsychological HL measure, and of PTSD symptoms. The sample was split into right HL and left HL individuals on both HL measures. Self-reported missile exposure was positively associated with PTSD symptoms in right HL, but not in left HL individuals on both HL measures. These results replicate, extend our previous results and suggest that left HL may even protect against the effects of severe life threatening events. Results are discussed in relation to neuropsychological and neurophysiological differences between the hemispheres.     

Orienting in Schizophrenia: Habituation to Auditory Stimuli of Constant and Varying Intensity in Patients High and Low in Skin Conductance Responsivity

Groups of schizophrenics and normal controls were exposed to different series of tones of constant (80dB) and variable intensity (60, 80, and 100 dB). Measurements included bilateral skin conductance, finger pulse volume, and heart rate. Both groups were split on the common median in skin conductance response to constant intensity tones to form matched patient and control groups of low and high responsivity. The low and high responsive schizophrenic groups were more clearly separated than the two control groups in rate of spontaneous skin conductance fluctuations, skin conductance magnitudes, and skin conductance levels, primarily because of generalized hyperactivity in high responsive patients. This pattern was clearest for the most intense tone and left hand recordings. High responsive schizophrenics also showed larger response amplitudes, shorter rise and recovery times, and a smaller ratio of elicited to spontaneous responses, than high responsive controls. Finger pulse volume responses recorded from the left hand were smaller in the patient groups, whereas patients and controls did not differ in right hand recordings. High skin conductance responsive subjects showed more heart rate deceleration than low responsive subjects, and schizophrenics had more decelerative responses than controls.     

Body temperature set-point and the conscious perception of skin temperature in obese women

Summary Obese and control women were immersed in a bath of water kept at 37° C. Oral temperature was measured. The subjects left hand was placed outside the bath for the local application of thermal stimuli between 20° and 45° C, subjects reporting the most pleasant temperature. The lower oral temperatures and lower levels of skin temperature rated as pleasant by obese women as compared with women of normal body weight or less suggests that in obesity the setpoint of body temperature is lowered.     

The Brentano illusion influences goal-directed movements of the left and right hand to the same extent

Recently, Gonzalez et al. (J Neurophys 95:3496–3501, 2006) reported that movements with the left hand are more susceptible to visual size illusions than are those with the right hand. We hypothesized that this might be because proprioceptive information about the position of the left hand is less precise. If so, the difference between the hands should become clearer when vision of the hand is removed so that subjects can only rely on proprioception to locate their hand. We tested whether this was so by letting right-handed subjects make open-loop pointing movements within an illusory context with and without vision of their hand. On average, the illusion influenced the left and the right hand to the same extent, irrespective of the visibility of the hand. There were some systematic differences between the hands within certain regions of space, but these were not consistent across subjects. We conclude that there is no fundamental difference between the hands in susceptibility to the Brentano illusion.