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Results for “Functional Laterality”

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PubMed2003

Pre- and postoperative intracarotid amytal procedure: an assessment of validity.

The intracarotid amytal procedure (IAP) was used twice to assess the suitability of three male patients for two successive neurosurgical procedures to relieve intractable temporal lobe epilepsy. First an amygdalohippocampectomy was performed, then further tissue was removed in a temporal lobe resection because their seizures had failed to remit. Repetition of the IAP following amygdalohippocampectomy when there was a known excision allowed inferences to be made regarding its validity in assessing lateralization of language functioning, memory functioning, and lateralization of seizure focus. The procedure was found to be reliable in assessing both language dominance and adequacy of memory functioning of the hemisphere contralateral to the lesion site. The procedure's third function of lesion lateralization was valid for identifying the known neurosurgical lesion. However, it was less successful in corroborating the lateralization of seizure focus before amygdalohippocampectomy. Differences in cognitive outcome between the two neurosurgical procedures are discussed.

Adult↗

PubMed2005

Laterality of manual function in foraging and positional behavior in wild indri (Indri indri).

This research is based on the idea that some prosimian species are good models in which to test certain postulates of the "postural origins" theory proposed by MacNeilage and colleagues [Behavioral and Brain Sciences 10:247-303, 1987] to explain the evolution of hand preference within the order Primates. We investigated manual laterality in 16 wild indris (eight males and eight females, living in four social groups) in their habitat, the Madagascan tropical rain forest. Data were collected on two spontaneous behaviors: "branch-reach," an action that occurs during foraging, and "higher support," a posture typical of clingers and leapers. A total of seven subjects were significantly lateralized for branch-reach (two showed a right preference, and five showed a left preference). Four subjects were significantly lateralized for higher support, and all of them showed a right-hand preference. Most of the indris we studied showed no preference. Our research suggests that indri are at "level 1 of laterality" in the classification framework proposed by McGrew and Marchant [Yearbook of Physical Anthropology 40:201-232, 1997]. The data presented here are not discordant with the "postural origins" theory, as lateralized subjects are often in the direction predicted by MacNeilage and colleagues [Behavioral and Brain Sciences 10:247-303, 1987], but they are the minority.

Animals↗

PubMed1997

Perspectives on the role of the lateral pterygoid muscle and the sphenomandibular ligament in temporomandibular joint function.

The lateral pterygoid muscle plays an important role in the movement of the mandible and has been studied from several points of view, including structural and functional anatomy. What matters clinically is the relative position of the muscle fibers attached medially to the mandibular condyle. In the following study, we observed not only the attachment of the lateral pterygoid muscle fibers to the articular disk, but also the relative position of the mandibular condyle to a base line set up on the mandibular condyle. According to our observations, the lateral pterygoid muscle fibers attach to the articular disk at the inner point of the medial pole. Based on this finding, we can say that the muscle fibers can both draw the articular disk anteriorly and balance it by supporting it posteriorly. That is to say, the lateral pterygoid muscle has two actions: to elevate the articular disk anteriorly and to support the articular disk. Furthermore, the sphenomandibular ligament has continuity with the articular disk tissue medially. This relationship suggests that the ligament fibers attached to the articular disk draw the disk posteriorly in its course of mandibular closing, thus enabling the articular disk to move smoothly.

Adult↗

PubMed1996

Functional MRI of lateral occipitotemporal cortex during pursuit and motion perception.

We performed functional imaging with a conventional 1.5-T magnetic resonance scanner in 9 normal subjects. We used a gradient-echo technique to examine changes in signal between periods when subjects viewed a stationary black-and-white grating, a moving grating, and when they followed a moving spot. We located image pixels with significant differences between the viewing conditions. In 7 subjects, these occurred in the lateral occipitotemporal cortex, a region previously identified as a putative human homologue of the motion-sensitive middle temporal area (MT, or V5) of monkeys. Signal intensity was greater during pursuit of the moving dot than during viewing of the moving grating with the eyes still, despite the fact that the moving grating generated more retinal image motion. In contrast, signal intensity in striate cortex was least during pursuit of the moving dot. These findings suggest that the lateral occipitotemporal cortex has extraretinal signals during pursuit. Such signals may include attentional input, corollary eye movement information, or even a pursuit command. Extraretinal signals suggest that the lateral occipitotemporal cortex may contain a human homologue not only of MT but also of other components of the monkey V5 complex, such as the medial superior temporal area.

Adult↗

PubMed1990

Lateralization of syringeal function during song production in the canary.

The canary (Serinus canaria) vocal organ, the syrinx, has two separate sound sources, one in the cranial end of each bronchus. Previous investigations of whether song syllables are produced unilaterally or bilaterally have provided two contradictory results, as one researcher suggested that almost all syllables are produced by the left side of the syrinx alone, whereas another researcher suggested that both sides contribute similarly to all syllables. Our experiments, which involved unilateral bronchus plugging followed later by denervation of the ipsilateral syringeal muscles, attempted to resolve this disagreement. The males with right bronchus plugs, singing on the left side of the syrinx alone, produced nearly normal songs, whereas the birds with left bronchus plugs, singing on the right side, sang quite poorly. Interpretation of these data is difficult because it is not clear how syringeal function would be affected if the airflow rate through the intact side is increased above normal, nor is it known if the bird can compensate for bronchus occlusion. Nonetheless, we suggest that in male canaries most syllables are normally sung by the left side alone, with some syllables being produced by the right side alone and some being sung by both sides together. Right nerve section had little effect on the right-bronchus-plugged males' ability to sing, but the repertoires of the left-plugged males were altered after left nerve section, indicating the possibility that signals carried by the left nerve exert an influence on the contralateral side.

Animals↗

PubMed1982

Lateralization of sensory and motor functions in human neonates.

Lateral differences in some motor and sensory functions were examined in 89 full-term normal newborns, 2 to 4 days old. They were divided in two groups, according to the cerebral dominance in the family: Group A (70 subjects), offspring of right-handed parents and siblings, and Group B (19 subjects), with at least one parent or sibling left-handed or ambidextrous. Only subjects of Group A showed a marked tendency to spend more time with the head to right as opposed to the left, to turn right after release from the midline position, to have their heads right 5 min. later, to lead with the right leg on the placing response. The two groups were significantly different from each other on these tests. Differences were not observed for stepping, tactile responses, asymmetrical tonic neck reactions in either of the two groups. The results confirm the existence of lateral differentiations of neurological functions in the newborn and stress the presence of genetic factors in these phenomena.

Dominance, Cerebral↗

PubMed2006

Functional specializations in lateral prefrontal cortex associated with the integration and segregation of information in working memory.

Control processes are thought to play an important role in working memory (WM), by enabling the coordination, transformation, and integration of stored information. Yet little is known about the neural mechanisms that subserve such control processes. This study examined whether integration operations within WM involve the activation of distinct neural mechanisms within lateral prefrontal cortex (PFC). Event-related functional magnetic resonance imaging was used to monitor brain activity while participants performed a mental arithmetic task. In the integration (IN) condition, a WM preload item had to be mentally inserted into the last step of the math problem. This contrasted with the segregation (SG) condition, which also required maintenance of the WM preload while performing mental arithmetic but had no integration requirement. Two additional control conditions involved either ignoring the preload (math only condition) or ignoring the math problem (recall only condition). Left anterior PFC (Brodmann's Area [BA] 46/10) was selectively engaged by integration demands, with activation increasing prior to, as well as during the integration period. A homologous right anterior PFC region showed selectively increased activity in the SG condition during the period in which the math problem and preload digit were reported. Left middorsolateral PFC regions (BA 9/46) showed increased, but equivalent, activity in both the SG and IN conditions relative to both control conditions. These results provide support for the selective role of lateral PFC in cognitive control over WM and suggest more specific hypotheses regarding dissociable PFC mechanisms involved during the integration and segregation of stored WM items.

Adolescent↗

PubMed2002

[The evaluation of lateralized frontal lobe function in the patients with autistic or attention deficit/hyperactivity disorder].

The prefrontal lobes are involved in two functionally distinct cognitive selection mechanisms: processing based on internal representation, such as planning (context-dependent reasoning) and exploratory processing of novel cognitive situations (context-independent reasoning). On the basis of this working hypothesis, a cognitive bias task (CBT; Goldberg, 1994), designed as an activation procedure representing contextual reasoning, was used to explore developmental disorders of lateralization in the frontal lobes in autistic disorder and attention deficit/hyperactivity disorder (ADHD). The subjects included 3 patients with autistic disorder, 4 with ADHD. Ten normal right-handed males served as controls. In CBT, a high score indicated consistency of choice: a context dependent selection bias, and a low score showed independent selection bias. The autistic group showed a score significant lower than those in controls (p < 0.01). The ADHD group had also a lower score. These findings implicate a deficit in the development of hemispheric specialization in the symptoms of these developmental disorders.

Attention Deficit and Disruptive Behavior Disorder↗

PubMed2005

Maths performance as a function of sex, laterality, and age of pubertal onset.

Sex differences in math/spatial performance demand explanations. Within the biological view, the complexity and number of variables make the explanation difficult at best. Laterality and age of pubertal onset have been investigated prominently in this context but rarely considered as interactions in the same study. Some 468 college subjects with SAT MATH (SAT M) scores were divided into 12 groups defined by sex, laterality, and age (early, middle, and late) of pubertal onset. Significant main effects for sex and age of onset emerged, as did an interaction between lateral preference and pubertal onset. Generally males outperformed females. The combination of maleness, sinistrality, and early maturation was associated with high SAT M scores. Sinistrality and late maturation among females predicted very poor math performance.

Adolescent↗

PubMed2005

Structural and functional asymmetry of lateral Heschl's gyrus reflects pitch perception preference.

The relative pitch of harmonic complex sounds, such as instrumental sounds, may be perceived by decoding either the fundamental pitch (f0) or the spectral pitch (fSP) of the stimuli. We classified a large cohort of 420 subjects including symphony orchestra musicians to be either f0 or fSP listeners, depending on the dominant perceptual mode. In a subgroup of 87 subjects, MRI (magnetic resonance imaging) and magnetoencephalography studies demonstrated a strong neural basis for both types of pitch perception irrespective of musical aptitude. Compared with f0 listeners, fSP listeners possessed a pronounced rightward, rather than leftward, asymmetry of gray matter volume and P50m activity within the pitch-sensitive lateral Heschl's gyrus. Our data link relative hemispheric lateralization with perceptual stimulus properties, whereas the absolute size of the Heschl's gyrus depends on musical aptitude.

Acoustic Stimulation↗

PubMed2002

Stimulus-response functions of the lateral dorsal striatum and regulation of behavior studied in a cocaine maintenance/cue reinstatement model in rats.

RATIONALE: To investigate potential neurocognitive mechanisms underlying drug-seeking and drug-taking behavior, the effects of reversible lidocaine-induced inactivation of the lateral dorsal striatum (DST) on behavior studied in a drug maintenance/cue reinstatement model were evaluated. This region of the DST was investigated because it selectively regulates stimulus-response learning that is disrupted by 10 microg of bilaterally infused lidocaine. METHODS: Rats ( n=6) were trained to self-administer 1 mg/kg per infusion cocaine under a second-order schedule of drug delivery. The effects of bilateral lidocaine (30-100 microg) inactivation of the lateral DST were evaluated during drug maintenance tests as well as during tests in which responding was reinstated by cocaine-associated cues presented in combination with a cocaine priming injection. The lower 10 microg dose was used to examine the effects of lidocaine on reinstatement of responding induced by presentation of cues alone. RESULTS: During drug maintenance tests, drug-seeking behavior was significantly increased after inactivation by 100 microg lidocaine. The number of infusions earned did not change. During cue-induced reinstatement tests preceded by a cocaine priming injection, 100 microg lidocaine significantly decreased both drug-seeking behavior and the number of infusion-paired light deliveries earned. During reinstatement tests with cues presented alone, inactivation of the lateral DST by 10 microg lidocaine did not influence either behavior. CONCLUSIONS: These findings suggest that stimulus-response functions of the lateral DST may regulate the dose-related effects of self-administered cocaine because the lidocaine-induced changes in behavior during the maintenance and cocaine priming tests resembled the effects of exposure to increasingly lower doses of cocaine, respectively. Given the lack of an effect of lidocaine during the cues-alone tests, the lateral DST does not appear to regulate drug-seeking behavior per se (i.e., responding maintained by drug-associated cues at times when drug is not available).

Acoustic Stimulation↗

PubMed1996

Visuomotor functions of the lateral pre-motor cortex.

Recent studies have provided new insights into the visuomotor functions of the dorsal and ventral regions of the lateral pre-motor cortex. Anatomical and physiological investigations in non-human primates have demonstrated that these regions have differing patterns of cortical connectivity and distinctive neuronal responses. Brain-imaging techniques and lesion studies have begun to probe the functions of homologous regions in humans.

Animals↗

PubMed1985

Adaptation of spatial modulation transfer functions via nonlinear lateral inhibition.

Adaptation, or change of shape of spatial modulation transfer functions (MTFs) on change of mean luminance level, occurs in visual interneurone and human psychophysical observations. Generally the bandwidth decreases and relative low frequency attenuation decreases as mean luminance decreases. Here it is shown how these changes in MTFs can be accounted for by nonlinear lateral inhibition based on spatial distributions of efficacy of voltage controlled synaptic conductance variation.

Adaptation, Physiological↗

PubMed1979

Functional organization of lateral geniculate cells following removal of visual cortex in the newborn kitten.

When the visual cortex of a newborn kitten is removed, most neurons in the dorsal lateral geniculate nucleus degenerate, but a small population of large cells is spared. Electrophysiological recording revealed that detailed visual topography in the nucleus is abnormal and that single cells have unusually large receptive fields. These results suggest that optic axons deprived of their normal synaptic targets rearrange their connections to converge on local surviving neurons.

Animals↗

PubMed1985

Laterality of dopamine function and neuroleptic action in the amygdala in the rat.

Rats selected according to turn preference in an open field were categorised as showing left or right hemispheric dominance (turning to right or left respectively). Dopamine was persistently infused into the central area of the left or right amygdala of animals showing left or right hemispheric dominance. Infusion was effected for 9 days by Alzet osmotic minipumps, implanted subcutaneously, which delivered 25 micrograms/24 hr of dopamine via chronically-indwelling, stereotaxically-located injection units. Dopamine caused marked and consistent hyperactivity only when infused into the left amygdala when the right hemisphere was dominant. This hyperactivity developed during the first day of infusion and persisted throughout the 9-day infusion period. Both (-)sulpiride and fluphenazine, injected unilaterally into the amygdala, antagonised the hyperactivity caused by infusion of dopamine into the left amygdala in animals with right hemispheric dominance. This antagonism could be effected both from the infused amygdala [5-50 pg (-)sulpiride, 25-100 pg fluphenazine] and from the contralateral amygdala [100-250 pg (-)sulpiride, 25-100 pg fluphenazine]. Thus, a laterality was shown for the action of dopamine in the amygdala of the rat. In contrast, neuroleptic agents failed to show an exclusive laterality of action, but were able to act in either hemisphere to antagonise the effects of dopamine injected into the left amygdala. Interhemispheric biochemical differences "within-animals" could not be shown, although differences were seen between rats having right or left hemispheric dominance.(ABSTRACT TRUNCATED AT 250 WORDS)

Amygdala↗

PubMed1988

Differential sensitization to amphetamine and stress responsivity as a function of inherent laterality.

With repeated administrations, rodents become increasingly sensitive to the stimulant properties of amphetamine, a phenomenon termed sensitization. Rats differentiated on the basis of their preferred direction of rotation following peripheral administration of amphetamine were found to differ in their sensitization to amphetamine in two different behavioral paradigms. Rats which displayed leftward rotational biases developed greater sensitization and greater hormonal response to stress following sensitization.

Adrenocorticotropic Hormone↗

PubMed1992

Functional localization and lateralization of human olfactory cortex.

Anatomical and physiological investigations in monkeys indicate that olfaction is subserved by several cortical regions. But the areas implicated in the human olfactory system have not been definitively identified by functional criteria. Behavioural evidence has suggested that laterally specialized mechanisms for odour processing may exist, but the neuroanatomical substrate remains unknown. We used positron emission tomography to study the cortical representation of human olfactory processing by comparing cerebral blood flow changes evoked during olfactory stimulation with those of a control task. We report here significant cerebral blood flow increases at the junction of the inferior frontal and temporal lobes bilaterally, corresponding to the piriform cortex, and unilaterally, in the right orbitofrontal cortex. The results complement and extend previous data implicating these regions in olfactory processing, and indicate that a functional asymmetry exists in the human brain favouring the right orbitofrontal area in olfaction.

Cerebrovascular Circulation↗

PubMed2005

Muscular mitochondrial function in amyotrophic lateral sclerosis is progressively altered as the disease develops: a temporal study in man.

We performed repeated analysis of mitochondrial respiratory function in skeletal muscle (SM) of patients with early-stage sporadic amyotrophic lateral sclerosis (SALS) to determine whether mitochondrial function was altered as the disease advanced. SM biopsies were obtained from 7 patients with newly diagnosed SALS, the same 7 patients 3 months later, and 7 sedentary controls. Muscle fibers were permeabilized with saponin, then skinned and placed in an oxygraphic chamber to measure basal and maximal adenosine diphosphate (ADP)-stimulated respiration rates and to assess mitochondrial regulation by ADP. We found that the maximal oxidative phosphorylation capacity of muscular mitochondria significantly increased, and muscular mitochondrial respiratory complex IV activity significantly decreased as the disease advanced. This temporal study demonstrates for the first time that mitochondrial function in SM in human SALS is progressively altered as the disease develops.

Aged↗