Un article très intéressant sur les liens entre spatialisation des perceptions, structures neurologiques, religiosité et tendances politiques.
En voici un extrait :
The piecing together of the data from numerous lesion studies and visual experiments led to a break down in the conventional view that the brain constructs a single view of space. Rather, it seems to construct more specific versions of space that optimize the simultaneous execution of various categories of behaviors. And according to Previc, it has constructed four spatial realms: the peripersonal (PrP); the ambient extrapersonal (AeP) ; the focal extrapersonal (FcE); and the action extrapersonal (AcE). (See Previc’s The Neuropsychology of 3-D Space, 1998, Psychological Bulletin, Vol 124.)
Previc’s four realms of space are depicted in the diagram below (excerpted from Fred Previc’s The role of extrapersonal brain systems in religious activity, 2006, Conciousness and Cognition 15).
The yellow field in the above diagram represents the well-known concept of peripersonal (PrP) space, which is the space within our grasp. The neurology surrounding peripersonal space is interesting, as it supports the control of the upper limbs. In primates, these limbs are positioned in the lower visual field. There is a distinctive downward bias of the peripersonal visual field, as can be easily be seen in the disproportionate time we spend manipulating objects that are beneath eye level.
The peripersonal system also has a distinctive neuroanatomy and neurochemistry, one that runs right into our theory of political orientation. Previc describes the neuroanatomy of the peripersonal system as « mainly housed in the dorsal cortical networks extending from the dorsal visual pathways through the lateral and medial portions of the parietal lobe and finally into the superior-lateral portions of the frontal lobe ».
Interestingly, the right hemisphere has a greater role in the management of the peripersonal system. The PrP system is also associated with the greater role of both noradrenaline and serotonin in its neurochemical management. Noradrenaline and serotonin are distributed asymmetrically in the right hemisphere, and the regular readers of this web site will immediately see the connection to political-religious disposition.
We have previously proposed an elevated influence of the right hemisphere and both the noradrenergic and serotonergic systems in liberal cognitive styles and behavior. Does this mean that liberalism is more oriented towards the peripersonal system than conservatism? This is probable. But this isn’t the only space that seems to be favored by liberals, as we also suspect a stronger orientation towards ambient extrapersonal space.
Ambient Extrapersonal Space: where the liberals are?
Extrapersonal space is the area outside our immediate grasp, and as organisms increase in complexity, they devote proportionately more neurology to its analysis. In Previc’s theory, there are three functional realms of extrapersonal space.
Previc’s ambient extrapersonal space (AmE), depicted as the green field in diagram 1, is essentially the brain’s version of gravitational space, which supports the orientation and posture of the body in the earth’s gravitational field. As such, it is largely responsible for the movement of the lower limbs. Previc’s AmE space starts where PrP space ends, about 2 meters from the body, and « extends to the outermost boundaries of the visual field » that « lie outside our frame of motion ».
Driving an automobile provides an excellent example, as maintaining velocity and lanekeeping are predominately the function of AmE space. AmE functionality also includes the stabilization of the perceptual world, allowing the other visual systems to function more efficiently. And like peripersonal space, there is a downward bias towards the lower visual field.
While the sense of vision predominates in the AmE realm, both vestibular (balance) and proprioceptive (body position) inputs complement visual inputs. Interestingly, vestibular and proprioceptive inputs also participate in the functioning of the PrP system. The AmE system is not very concerned about details, as « spatial orientation can easily be maintained despite considerable optical degradation ».
The AmE system employs dorsal visual pathways that course through the parietal lobe, and has a distinctive neurochemistry dependent on noradenergic and serotonergic transmission. This links it to its sister spatial system, the PrP, and further, links it to liberal political-religious orientations via the elevated adaptation of noradrenaline, serotonin, and the right hemisphere. Are the nonreligious liberals more oriented towards peripersonal and ambient extrapersonal space than the religious conservatives? Based on Previc’s theories, this is highly probable. But first, where do god and the conservatives live?
Focal Extrapersonal Space
When it comes to god, the real action of Previc’s religious theories start with the action extrapersonal system and its close cousin, the focal extrapersonal system (FcE). The FcE just happens to be the only spatial system associated with retinotopic coordinates. Retinotopy is the mapping of locations in the visual field onto the cortical surface of the brain. As such, the focal extrapersonal system is the most limited in scope (see the red area in diagram 1), but the most important in visual search, and the critical functions of object and facial recognition.
As opposed to the dorsal orientation of the PrP and AmE systems, the FcE system runs « ventrally through the occipital-temporal pathways and finally on into the lateral and medial-basal portions of the frontal lobe ». The FcE is dominated by visual inputs confined to the central 30 degrees of the visual field. The FcE is directed towards distant space, but can focus on objects within peripersonal space as well.
Unlike the downward bias of the PrP and AmE systems, the FcE has a strong bias towards the upper visual field. The FcE system is where motion, local form, and depth processing prevail. But what makes the FcE system particularly relevant to political-religious disposition is its reliance on dopaminergic transmission. In fact, key dopaminergic pathways of the FcE system run right through the inferior temporal lobe–a key region implicated in religious disposition and political conservatism.
Action Extrapersonal Space
Previc’s action extrapersonal space, AcE, « uses mainly visual and auditory information to enable us to orient, navigate, and interact in topographical space ». It also orients to targets, and is « closely involved with episodic memory for places and events ». AcE integrates visual, auditory, proprioceptive, and vestibular inputs « concerning the movement of the head in space », and shares common temporal-occipital neural substrates with the FcE, along with coursing through the politically-hot orbitofrontal cortex.
Like its sister system, the FcE, the AcE system is biased toward the upper visual field. « Attentional neglect of upper, distant space is a frequent sequel to inferior temporal lobe damage ». As previously noted, there is a strong relationship between the temporal lobe and religious disposition. According to Previc’s theory, it is the action extrapersonal system that is most closely linked with religiosity.
Unlike the retinotopic coordinate system utilized by the FcE, AcE space is gaze-centered, dependent on the position of the head in space. Neurons in the hippocampus are activated by the space upon which gaze is directed. AcE space is interesting in that it completely maps a 360 degree surround, using auditory cues to handle the space behind the head. The AcE system extends from the outer boundary of peripersonal space, about 2 meters, to about 30 meters.
And like the FcE system, dopaminergic neurotransmission prevails in the AcE. In fact, Previc has not only constructed a theory of the dopaminergic origins of religiosity, he has also constructed a theory linking dopamine with human evolution. And all this from studying the way the brain maps space.