Human Paleoneurology and the Evolution of the Parietal Cortex

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Rachel Golden
5 years ago
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PARIETAL LOBE The Parietal Lobes develop at about the age of 5 years. They function to give the individual perspective and to help them understand space, touch, and volume.

The Central Sulcus Is a valley that marks the differenciation between lobes. The Central Sulcus is easily identified.

1 PARIETAL LOBE The Parietal Lobes develop at about the age of 5 years. They function to give the individual perspective and to help them understand space, touch, and volume. The location of the parietal lobes is delineated by specific landmarks. The central sulcus separates the parietal lobe from the frontal lobe. The Central Sulcus Is a valley that marks the differenciation between lobes. The Central Sulcus is easily identified. In addition to marking the perimeter of the lobe the Central Sulcus has specific functions. Just as the central sulcus separates the parietal lobe from the frontal lobe, the parietooccipital sulcus separates the parietal lobe from the occipital lobe..they are the superior (top section) parietal lobule, the inferior (lower section) parietal lobule and the intraparietal (middle section) sulcus.

Human Paleoneurology and the Evolution of the Parietal Cortex Homo sapiens is characterized by larger parietal bones and, according to the paleoneurological evidence, also by larger parietal lobes.

2 Human Paleoneurology and the Evolution of the Parietal Cortex Homo sapiens is characterized by larger parietal bones and, according to the paleoneurological evidence, also by larger parietal lobes. The dorsal elements of the posterior parietal cortex (superior parietal lobules, precuneus, and intraparietal sulcus) may be involved in these morphological changes. This parietal expansion was also associated with an increase in the corresponding vascular networks, and possibly with increased heat loads. Only H. sapiens has a specific early ontogenetic stage in which brain form achieves such globular appearance. In adult modern humans, the precuneus displays remarkable variation, being largely responsible for the longitudinal parietal size. The precuneus is also much more expanded in modern humans than in chimpanzees. Parietal expansion is not influenced by brain size in fossil hominids or living primates. Therefore, our larger parietal cortex must be interpreted as a derived feature. Spatial models suggest that the dorsal and anterior areas of the precuneus might be involved in these derived morphological variations. These areas are crucial for visuospatial integration, and are sensitive to both genetic and environmental influences. This article reviews almost 20 years of my collaborations on human parietal lobe evolution, integrating functional craniology, paleoneurology, and evolutionary neuroanatomy.. SOURCE:

Contribution of the posterior parietal cortex in reaching, grasping, and using objects and tools Neuropsychological and neuroimaging data suggest a differential contribution of posterior parietal

3 Contribution of the posterior parietal cortex in reaching, grasping, and using objects and tools Neuropsychological and neuroimaging data suggest a differential contribution of posterior parietal regions during the different components of a transitive gesture. Reaching requires the integration of object location and body position coordinates and reaching tasks elicit bilateral activation in different foci along the intraparietal sulcus. Grasping requires a visuomotor match between the object's shape and the hand's posture. Lesion studies and neuroimaging confirm the importance of the anterior part of the intraparietal sulcus for human grasping. Reaching and grasping reveal bilateral activation that is generally more prominent on the side contralateral to the hand used or the hemifield stimulated. Purposeful behavior with objects and tools can be assessed in a variety of ways, including actual use, pantomimed use, and pure imagery of manipulation. All tasks have been shown to elicit robust activation over the left parietal cortex in neuroimaging, but lesion studies have not always confirmed these findings. Compared to pantomimed or imagined gestures, actual object and tool use typically produces activation over the left primary somatosensory region. Neuroimaging studies on pantomiming or imagery of tool use in healthy volunteers revealed neural responses in possibly separate foci in the left supramarginal gyrus. In sum, the parietal contribution of reaching and grasping of objects seems to depend on a bilateral network of intraparietal foci that appear organized along gradients of sensory and effector preferences. SOURCE:

The parietal lobe and the vestibular system. The vestibular cortex differs in various ways from other sensory cortices. It consists of a network of several distinct and separate temporoparietal areas.

The entire network is multisensory (in particular, vestibular, visual, and somatosensory).

4 The parietal lobe and the vestibular system. The vestibular cortex differs in various ways from other sensory cortices. It consists of a network of several distinct and separate temporoparietal areas. Its core region, the parietoinsular vestibular cortex (PIVC), is located in the posterior insula and retroinsular region and includes the parietal operculum. The entire network is multisensory (in particular, vestibular, visual, and somatosensory). The peripheral and central vestibular systems are bilaterally organized; there are various pontomesencephalic brainstem crossings and at least two transcallosal connections of both hemispheres, between the PIVC and the motion-sensitive visual cortex areas, which also mediate vestibular input. Structural and functional vestibular dominance characterizes the right hemisphere in right-handers and the left hemisphere in left-handers. This explains why right-hemispheric lesions in right-handers more often generally cause hemispatial neglect and the pusher syndrome, both of which involve vestibular function. Vestibular input also contributes to cognition and may determine individual lateralization of brain functions such as handedness. Bilateral organization is a major key to understanding cortical functions and disorders, for example, the visual-vestibular interaction that occurs in spatial orientation. Although the vestibular cortex is represented in both hemispheres, there is only one global percept of body position and motion. SOURCE:

Unilateral spatial neglect after posterior parietal damage. Unilateral spatial neglect is a disabling neurologic deficit, most frequent and severe after right-hemispheric lesions.

5 Unilateral spatial neglect after posterior parietal damage. Unilateral spatial neglect is a disabling neurologic deficit, most frequent and severe after right-hemispheric lesions. In most patients neglect involves the left side of space, contralateral to a right-hemispheric lesion. About 50% of stroke patients exhibit neglect in the acute phase. Patients fail to orient, respond to, and report sensory events occurring in the contralateral sides of space and of the body, to explore these portions of space through movements by action effectors (eye, limbs), and to move the contralateral limbs. Neglect is a multicomponent higher-level disorder of spatial awareness, cognition, and attention. Spatial neglect may occur independently of elementary sensory and motor neurologic deficits, but it can mimic and make them more severe. Diagnostic tests include: motor exploratory target cancellation; setting the midpoint of a horizontal line (bisection), that requires the estimation of lateral extent; drawing by copy and from memory; reading, assessing neglect dyslexia; and exploring the side of the body contralateral to the lesion. Activities of daily living scales are also used. Patients are typically not aware of neglect, although they may exhibit varying degrees of awareness toward different components of the deficit. The neural correlates include lesions to the inferior parietal lobule of the posterior parietal cortex, which was long considered the unique neuropathologic correlate of neglect, to the premotor and to the dorsolateral prefrontal cortices, to the posterior superior temporal gyrus, at the temporoparietal junction, to subcortical gray nuclei (thalamus, basal ganglia), and to parietofrontal whitematter fiber tracts, such as the superior longitudinal fascicle. Damage to the inferior parietal lobule of the posterior parietal cortex is specifically associated with the mainly egocentric, perceptual, and exploratory extrapersonal, and with the personal, bodily components of neglect. Productive manifestations, such as perseveration, are not a correlate of posterior parietal cortex damage. SOURCE:

Differential Effects of Parietal and Cerebellar Stroke in Response to Object Location Perturbation A study was done to contrast impairments in reach-to-grasp coordination, in response to object

6 Differential Effects of Parietal and Cerebellar Stroke in Response to Object Location Perturbation A study was done to contrast impairments in reach-to-grasp coordination, in response to object location perturbation, in patients with right parietal and cerebellar lesions, in order to further elucidate the role of each area in reach-to-grasp coordination. Sixteen chronic stroke participants (eight with right parietal lesions and eight with cerebellar lesions) were matched in age (mean = 61 years; standard deviation = 12) and hand dominance with 16 healthy controls. Hand and arm movements were recorded during unperturbed baseline trials and unpredictable trials in which the target was displaced to the left or right or remained fixed.as a result Cerebellar patients had a slowed response to perturbation with anticipatory hand opening, an increased number of aperture peaks and disruption to temporal coordination, and greater variability. Parietal participants also exhibited slowed movements, with increased number of aperture peaks, but in addition, increased the number of velocity peaks and had a longer wrist path trajectory due to difficulties planning the new transport goal and thus relying more on feedback control. Patients with parietal or cerebellar lesions showed some similar and some contrasting deficits. The cerebellum was more dominant in controlling temporal coupling between transport and grasp components, and the parietal area was more concerned with using sensation to relate arm and hand state to target position. SOURCE:

FRONTAL LOBE. Central Sulcus. Ascending ramus of the Cingulate Sulcus. Cingulate Sulcus. Lateral Sulcus

FRONTAL LOBE. Central Sulcus. Ascending ramus of the Cingulate Sulcus. Cingulate Sulcus. Lateral Sulcus FRONTAL LOBE Central Ascending ramus of the Cingulate Cingulate Lateral Lateral View Medial View Motor execution and higher cognitive functions (e.g., language production, impulse inhibition, reasoning