Neural correlates of mental transformations of the body-in-space.

Abstract

Regional cerebral blood flow was measured with positron emission tomography in human subjects during the performance of a task requiring mental rotation of their hand and a perceptually equivalent control task that did not require such a process. Comparison of the distribution of cerebral activity between these conditions demonstrated significant blood flow increases in the superior parietal cortex, the intraparietal sulcus, and the adjacent rostralmost part of the inferior parietal lobule. These findings demonstrated that, in the human brain, there is a specific system of parietal areas that are involved in mental transformations of the body-inspace.Patients with lesions of the parietal region of the brain exhibit various disturbances of body knowledge (1-3). Large parietal lesions give rise to classical syndromes such as right-left disorientation (1-3) and autotopagnosia, a deficit in localizing body parts in relation to the whole body (4-6). These syndromes are most often associated with lesions of the left hemisphere. Similarly, epileptic manifestations that accompany parietal-lobe tumors can result in disturbances of the body image, such as absence or displacement of a part of the body, transformation of a limb into a mechanical object, the phantom appearance of a third limb, and the personification of a body part (3). These intriguing phenomena are assumed to result from an impairment in the "body schema" (1-3) that traditional neurological thinking ascribed to the posterior parietal cortex (7).There is some evidence, based on single-cell recording studies with nonhuman primates, that neuronal activity in the cortex of the superior parietal lobule (area PE) and its rostrally adjacent cortex surrounding the anteriormost part of the intraparietal sulcus (area PF) codes the position and orientation of body parts in relation to each other (8, 9). We hypothesize that these areas, within the broader neural network in which they are embedded, are the essential components underlying body awareness.This neural system constantly receives information about changing states from the skin and the joints and builds, on this basis, a dynamic and plastic mental representation of the body-in-space. The body is thus placed in a continuous interactive relation with the external world. This dynamic interaction allows for the simulation of continuous spatiotemporal trajectories of body motion and specifies how one's future posture causally depends on one's current posture.

Imaging a cognitive model of apraxia: The neural substrate of gesture‐specific cognitive processes

“…Hence, our data are not in contradiction with, but refine, gesture observation and simulation studies suggesting that a similar dorsal network may be involved for visually-perceived novel and familiar gestures when the aim of the visual perception is to imitate [Decety et al, 1997;Grèzes et al, , 1999. Activation of the dorsal network during imitation is consistent with studies showing that the parietal cortex houses transformational processes linking perception to action [Andersen et al, 1997;Freund, 2001;Goodale and Haffenden, 1998;Goodale and Milner, 1992], participates in sensorimotor integration by maintaining an internal representation of the body's state as predicted by computational models ], and is involved in mental transformations of the body-inspace [Bonda et al, 1995[Bonda et al, , 1996a.…”

Perceptual aberrations impair mental own-body transformations.

“…Thus, the patients showed high activity in the right angular gyrus when they experienced being the agent of their actions, whereas this activation in healthy controls is only seen when agency is allocated to another person. The role of this brain region in self and bodily processing is further supported by functional imaging studies in healthy individuals (Astafiev, Stanley, Shulman, & Corbetta, 2004;Bonda, Petrides, Frey, & Evans, 1995;Calvert, Campbell, & Brammer, 2000;Lobel, Kleine, Bihan, Leroy-Willig, & Berthoz, 1998;Uddin, Kaplan, Molnar-Szakacs, Zaidel, & Iacoboni, 2005) and by patients with focal brain lesions (e.g., Apperly, Samson, Chiavarino, & Humphreys, 2004;Scepkowski & Cronin-Golomb, 2003;Semenza, 1988).…”

Mental Imagery for Full and Upper Human Bodies: Common Right Hemisphere Activations and Distinct Extrastriate Activations

“…Behavioural, neuropsychological, and neuroimaging studies suggest that processing human bodily stimuli involves brain regions that are at least partially different from those sub-serving the processing of noncorporeal objects (Ionta et al 2010;Wraga et al 2005;Creem et al 2001;Bonda et al 1995;Parsons 1987a, b). With respect to neural mechanisms, neuropsychological findings suggest that the left hemisphere might be dominant for the processing of body parts (Schwoebel and Coslett 2005;Guariglia et al 2002;Sirigu et al 1991;Ogden 1985), although own body illusions and deficits in corporeal awareness have been linked primarily to the right hemisphere Berlucchi and Aglioti 1997).…”