Phenomenology Life and Simplexity Jean-Luc Petit Université de Strasbourg.
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Transcript of Phenomenology Life and Simplexity Jean-Luc Petit Université de Strasbourg.
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Phenomenology Life and Simplexity Jean-Luc Petit Universit de Strasbourg Slide 2 Plan 1.The complexity of reality 2.Complexity a threat to the living being 3.Simplexity: getting us out of predicament 4.Natural science and phenomenology 5.Constitution Theory a framework for simplexity 2 Slide 3 Plan 1.The complexity of reality 2.Complexity a threat to the living being 3.Simplexity: getting us out of predicament 4.Natural science and phenomenology 5.Constitution Theory a framework for simplexity 3 Slide 4 Palimpseste du Monastre de Ste Catherine, Mt Sina (IVe s) 4 Slide 5 5 Stars cradle Fly brain Slide 6 6 Slide 7 7 Slide 8 Reaction of Belousov-Zhabotinsky Oxydoreduction of citric acid into a carbonic gas in which concentrations of bromate /bromure pass alternatively below and above a critical value under the influence of an autocatalytic coupling of states of the two substances, either oxidized or reduced. Periodicity of colour changes observed by Boris Belousov in a study of metabolism of glucose (1950) 8 Slide 9 Emergence in a network: u, v in same component because there is a path from u to v. x, y in distinct components : no path. If one adds m random connections between the n nodal points of the network, as soon as m goes beyond n/2, a giant component develops, until it encloses all the nodes. An abstract mathematical model of the phase transitions and the appearance of structures out of chaos in dynamic physical or biological systems. T. Bohman, Science 323 (2009) 9 Slide 10 Complex System = not completely aleatory nor completely regular. Brain: a mix of anatomical segregation and functional integration. G. Tononi et al, TICS 2/12 (1998) 10 Slide 11 Plan 1.The complexity of reality 2.Complexity a threat to the living being 3.Simplexity: getting us out of predicament 4.Natural science and phenomenology 5.Constitution Theory a framework for simplexity 11 Slide 12 A. Berthoz: Nous vivons cartels entre de nombreuses identits qui nous placent dans un entrelacs de toiles daraignes sociales et psychologiques Lhomme daujourdhui est un Thse perdu dans un labyrinthe Slide 13 E. Rolls The Brain and Emotion (1999) Thalamus Striatum Basal Ganglia Cerebral Cortex Globus Pallidus Substantia Nigra Subthalamic n. Multiplicity of functional loops in the brain apparently incompatible with the stability of functioning of circuits 13 Slide 14 Plan 1.The complexity of reality 2.Complexity a threat to the living being 3.Simplexity: getting us out of predicament 4.Natural science and phenomenology 5.Constitution Theory a framework for simplexity 14 Slide 15 The inventary of simplex solutions F: 'X is an ingenious solution invented in the course of evolution to simplify (reduce the dimensions of) the problem posed by the complexity of the environment.' F is then the general formula for drawing up an inventory of the remarkable features of living organisms but a list still does not amount to a theory. How does one get from a list to a Theory of simplexity? 15 Slide 16 A tool-box of simplifying Principles 'A simplex process, Berthoz tells us, is a process regulated by several principles... This list of principles is designed to provide a framework, inevitably incomplete and debatable, for specifying the concept of simplexity (4)'. Only, this list knows no end: 'it is impossible to describe all the simplifying principles evolution has put in place: we discover more of them every day (73)'. In the end, no procedure can be excluded: 'Evolution seems to have used any means available, adopting unpredictable paths, utilizing all the tools that physics and chemistry made available, with the sole end in view of simplifying (38)'. 16 Slide 17 17 Motor equivalence in gaze We can move our gaze by moving the eye or by moving the eye and the head or even by moving the whole body : For that the gaze movement needs to be coded sufficiently generally to be realized by any part of the body. The gaze movement is coded in a variable of velocity that is transformed in a signal of position according to the internal model controling the movement of the chosen limb. A retinotopic model map where each neuron is represented by its receptive field: The displacement of target in outer space is predicted by the change of activity in the map as a gaze-velocity signal is updated after the oculomotor command. No need of a higher cognitive spatial map to track the movement of targets in space. Proc. Natl. Acad. Sci. USA, 88, 9653 (1991) Slide 18 18 Making a detour in tracking tasks: Instead of trying to continuously control the unpredictably changing position of a moving target Subjects intermittently minimize a composite variable s (a mixture of position, speed and acceleration) using a feedback (corrective) and feedforward (estimative) strategy in order to compensate for the unknown dynamics of the limbs- object system keeping it within the limits of one dimension. The hand movement needed for that correction might be a simple ballistic movement with a stereotyped cinematic profile. Biol. Cybern. 77, 381 (1997) Slide 19 19 Deciding where to look Self-initiated (not externally cued) eye movements between alternatively possible targets rely on the prefrontal cortical areas of decision-making in behavior. Decision condition: subjects are free to decide the direction of the forthcoming saccade. Dorsolateral prefontal cortex active in decision condition not in case of imposed saccades. Task: fMRI results: Neuroreport 18(12) (2007) Slide 20 20 Catching a falling ball thanks to an internal model of gravity: The brain triggers hand movement based on the visual image of the object complemented by an implicit knowledge of the acceleration effect of gravity. In the shuttle (0 g) the anticipatory movement occured earlier than on earth. Prediction of movement is simplified by an internalization of laws of physics making possible to simulate moving objects in the world with the body. Nature Neurosc. 4, 7 (2001) --- Lag of time-to-contact visual estimation (1g) --- Precocious TTC based on internal model (0g) Anticipatory biceps EMG response (0g) Slide 21 21 Head stabilization for top-down control of locomotion: The task of coordinating the degrees of liberty of the limbs in walking is organized from the head not the feet. The head is used as a mobile inertial platform freeing the body from the ground. Head kinematics video recorded and reconstructed by computer (10 sj). Exp. Brain Res (1990) 82, 97-106 Slide 22 22 Different brain areas for egocentric and allocentric strategies in spatial location: Orienting oneself in space supposes an ability to change point of view: from refering to oneself to taking an object or a landmark in the environment as frame of reference. Egocentration activates a network including: parietal (1) occipital (2) and frontal (3, 4) areas. Allocentration activates a partly different network including also occipito-temporal (7, 9) areas. J Cogn. Neurosci., 169 (2004) Tasks : 1) Which garbage can is closer to you? 2) Which can is closer to the red ball? 3) Which can is closer to the front of palace? Slide 23 Perspective taking : two mental imagery strategies for embodiment of the other a: Reflection Symmetry : A tilts on his left when B tilts on his right and vice versa as if A saw himself in a mirror. b: Rotation Symmetry : A tilts on his left when B tilts on his left as if disembodying and adopting Bs perspective. c: experimental setting: Subject on a ground trace in line with the rope of the acrobate. d: goniometer recording the tiltings of the bar. e: video of avatar acrobate tilting on his right (or left: f). Brain & Cognition (2009) 23 Slide 24 Plan 1.The complexity of reality 2.Complexity a threat to the living being 3.Simplexity: getting us out of predicament 4.Natural science and phenomenology 5.Constitution Theory a framework for simplexity 24 Slide 25 25 'Any science has to replace, or economize on, experience, by reproducing, or prefiguring, facts in the form of thoughts, such reproductions being more readily available than experience itself, and therefore capable of replacing the latter in many respects (452)... Science can itself therefore be regarded as a minimal task, consisting in representing the facts in the most complete manner possible and with the least expenditure of thought (E. Mach, Die Mechanik in ihrer Entwickelung, 1883, 461)'. 'This would-be principle is nothing less than an attempt at an ultimately rational explanatory principle, the mere grouping together of an entire complex of evolutionary facts in advance of any ideal reduction to elementary facts and laws, and this whether or not any such reduction will ever be realizable (Husserl 1913, IX, .55).' Slide 26 Formation of neuronal groups on the computer: A : initial state of part (12 x 6) of a network of 144 excitatory cells and 2448 synaptic connections. = cell = synaptic connection, colors = strength of synaptic connection B : state after hand surface stimulation (activation of 3x3 receptors) : formation of neuronal groups by reinforcing connections between neighboring cells and weakening connections between distant cells. C : enlargement of B part including groups et : Blue borders of weak connections protecting groups from encroachment by other groups. Interface / corresponds to the frontier between palm and back of hand. J. Pearson et al., The J. of Neuroscience (1987) A Dynamic Model of Morphogenesis The cortical map of a hand simulated 26 Slide 27 27 Recanzone et al., J. of Neurophysiology (1992) Receptive Fields of 3b neurons located on trained hand (monkeys with improved performances) 3b RFs on controlateral hand Plasticity of hand functional organization induced by stimulation Slide 28 28 ///// : back of hand representation : loss of response Median nerve transsection deprives the cortex of palm entries D1-D2 Stages of reorganization: (1)Silence of some cortical regions; new responses in bac