The model for Dasein put forward so far is, though established from an evolutionary point of view, of an "ideal" philosophical process. So that we may understand how the human mind works, and in turn come to further understand the pure model, we shall now see how this model is represented in the functional neuroanatomy of the brain. There are two important points to consider before we detail the correlates: Firstly, the brain was a product of evolution, and as such was developed through gradual outgrowing, reshaping and repositioning of the interconnections within its structure. Thus, what was evolved first tends to be not discarded but adapted where necessary and incorporated into the new scheme of things. Take for example the vestigial tail in the apes, or the remnant bone structure of ancient hands in the flippers of aquatic mammals. In the brain this has had the similar effect of creating a mass of interconnections that, though elegant in execution as the rest of nature tends to be appreciated, is not the logically simplest way to achieve the end product. Secondly, and related to this point, evolution has "hard-wired" many "instinctive" neural pathways that, though certainly a benefit for living organisms trying to survive and procreate, are equally certainly not a necessity to becoming self-aware. The visual and auditory senses pass through the lateral and medial geniculate nuclei on their way to the cortex, these connections allowing Dasein to turn its head, "instinctively" on a pre-conscious level, towards sudden noises. No doubt a benefit should a lion step on a twig, but something that could be just as left to conscious decision in a synthetic instance of Dasein. These two points, together, tend to make the biological, evolutionarily derived, model of Dasein an order more complex than it need be. Overview  If we casually inspect the human brain from afar, what we can mostly see from the sides and top is the cortex. The cortex is like a covering, that encapsulates the evolutionarily older parts at the centre of the brain. To the bottom right of the picture, we can see the cerebellum, this part of the brain deals with motor control, fine tuning and memory of movement. It is not concerned with the higher functions of motor control, and as such shall not be a part of the following discussion. Just below the cerebellum we can see a small "tail", which is the beginning of the emergent spinal cord. There are other nerves that leave the brain (eg. the optic nerves) that have been removed from this specimen. The cortex is just 2-4 mm in thickness, and contains millions of cortical columns. These are thought to be the functional units of the cortex, collections of approximately 60,000 neurons acting together. They are good candidates for the functional unit of Interpretation. On Translating the model The foundation of the model proposed in this site is the continuous Anticipation and Making-Present that forms the Temporal loop. This cycle of Interpretation is the basic unit of flow, where Interpretation is the basic function, in Dasein. In the brain, the cortex is the only site where this can take place. Cortical tissue is neuron dense, has massive interconnection and exhibits neuroplasticity (for example, through Hebbian modifications), and so accords to the monism, materialism and mutation definition of Entities given earlier. If the Entities are to be found in the cortex, then, since the manner of their definition and retrieval is Interpretation, then this function too must be a part of the cortex. In all respects, the cortex is the very definition of the Entity/Interpretation symbiosis we defined as a product of evolution. That the cortex is also the historically most recent adaptation further supports this conclusion. Now, the cortex does not exhibit behaviour as simple as the loop described. It has regions of distinct functionality; some to deal with senses, some motor action, some speech, some planning and so on. Not only that, but simply from a topological point of view there is no great loop of neurons shaped like a doughnut. In order to reconcile the philosophical model with the natural one we need to execute more than one Temporal loop. Before we proceed to divide up the cortex, we need to first establish the equivalence of one and many Temporal loops. Consider the follow diagram.  On the left is the Temporal Cycle as we derived it, senses merged into a single cycle. On the right we have two cycles, each a product of primarily a single sense yet able to incorporate information from another sense by exchange of post Interpretive data from the Now (or similar Entity state). If the flow of information between the two Nows is total, then the two systems are logically equal; they have identical input and, through the Potentiality-for-Being, if the Interpretation of each respective sense is performed in the same way then they shall have identical output. In a system free of energy constraints, total information exchange would be ideal and equivalent to the mono-loop. In a system governed by energy constraints this ideal is likely to be compromised, resulting in approximation and loss of resolution in Interpretation. That the mono-loop is computationally equivalent to the multi-loop system, in principle and structure if not in the accuracy of execution, allows us to split up the senses as the biological model of Dasein does, and apply the philosophical concept of the Temporal Cycle to the brain. Basic neuroanatomy  Sight originates in the retina and travels via the thalamus to the primary visual cortex (V1), situated at the back of the occipital lobe. Sound originates in the cochlear and travels via the thalamus to the primary auditory cortex (A1) near the top of the temporal lobe. Touch originates in receptors in the skin from all over the body and travels via the thalamus to the primary somatosensory cortex (S1) at the front of the parietal lobe. Bordering S1 anteriorly (towards the front) is the primary motor cortex (M1) located at the back of the frontal lobe. Though distinct from the other primary cortices in that it is not a sense and is the origin of motor action, the primary motor cortex cycle has similar functions to the others. Note at this stage the broad distinction made between the anterior and posterior halves of the cortex; the frontal lobe being primarily concerned with action, the parietal, temporal and occipital lobes being concerned with sensory representation of the world. The Cycles - Weak Derivative Interpretation  So, the visual cortex begins to spot patterns such as lines, angles, movements, regions of colour and so on, the results of these Interpretations being passed on in two main projections; the dorsal and ventral streams. The dorsal uses this information to Interpret, with respect to Entities held within its Interpretive functions, the nature of locations of Entities within the field of vision, it is often called the "where" stream. The ventral stream uses this information to Interpret the nature of quiddity, what Entities are present in the field of view, it is often called the "what" stream. Likewise, the auditory cortex determines what sound Entities are present, and the somatosensory cortex where the body is in relation to itself. Now, if any one region of the cortex is performing a certain "type" of Interpretation, of a "whatness" or a "whereness", it must, once performed, send this information on to another region of the brain. The streams or projections we have just been looking at all pass on their information to many parts of the brain, both cortical and subcortical. But it is when those Interpretive products are passed on to other cortical regions that we begin to see emergent functions; for the cortex begins to make derivative Interpretations. Let us take the ventral stream as an example. To begin with it receives from the primary visual cortex Interpreted data such as lines, colours and movement and Interprets this in terms of Entities, and by so doing may recognise "forms" in the visual field. These forms accord with Entities of certain colour, shape and size. In turn, this information is passed on and Interpreted within the next cortical region that may match the forms to Entities of the next derivative, objects. Forms of brown, slightly shiny, may been Interpreted in the following derivative as "wood" should their appearance match the qualities of the Entity. This process is, by the definitions laid down earlier, a form of derivative weak Interpretation, and its product is what we termed as "the Now". In each projection, by following through these weak derivative Interpretations, the stream shall arrive at Entities representative of our highest conceptions; sounds as words, sights as objects, relative location and position of the self and objects around us in the world. However, in the brain there are two other functions occurring at the same time; there is convergence of the senses, producing hybrid representations of reality, and the Anticipation and Making-Present vital for the Temporal loop. The Cycles - Sensory Convergence So within the diagram above we have the three primary sensory cortices and their projections of weak derivative Interpretation through the cortex where they, at some point, eventually Interpret Entities of the highest order that the mind is able to comprehend. These projections are also, however, projecting towards other regions of sensory Interpretation, and this begins to result in sensory convergence. Convergence entails the function of inter-sensory Interpretation; the ability to link the related properties of Entities encountered within the world. In the temporal lobe the ventral stream and the auditory stream converge; if one sees a lion, the roar can be "recalled". If one hears a lion, its visage can be "recalled". The sound and sight of high-order Entities are thus intrinsically linked. In the parietal lobe the dorsal and somatosensory streams converge; the position of the body, in form and within the world, is related relatively to all that is seen to Be within-the-world around oneself. The result of sensory convergence is twofold. Firstly, there is a significant evolutionary benefit if the senses work together. Should sight be mentally unlinked to sound we would experience shock every time thunder follows lightning. In a more practical sense, for both fight or flight the integration of sight with sound and bodily position within-the-world is obviously far more desirable than a mind that is forced to react to each sense on an individual basis. Secondly, concerning the eventual consciousness of Dasein, this convergence of information serves to centre the Being-in-the-World of all Entities on Dasein itself. In the Temporal Cycle we explored how in motor action Dasein effects the World and the They, and in so sensing the reactions to its own actions builds an Entity of self. The audio-visual and somato-visual syntheses respectively correlate the voice and bodily action of Dasein with the World in which it exists. Thus giving relative definition to Dasein itself as an Entity within the World-image it constructs. This becomes vital, as we shall see later, for the phenomenal sensation of perception experienced by Dasein. The Cycles - Anticipation of the Now At some point within the Interpretive process outlined so far, from the weak derivative Interpretations through to sensory convergence, Dasein begins to perform Temporal Interpretation. Whether concerning the lowest or highest order of Entities within the streams, the cortex can project each Entity into a possible future with respect to the Now of related Entities. The principle diagram on which our original philosophical considerations were based only depicts a single, all encompassing, Anticipatory Interpretation. We have, above, broken this down into separate cycles for each of the sensory streams, and we shall now break it down further. Rather than bring all the Nows of one hybrid-sense together for Anticipation, the biological architecture and evolutionary logic determine that Anticipation is performed in parallel at disparate regions of the brain. The nature of the Being of an Entity is such that it is defined by its interconnections, and the physical topography of the brain is such that related Entities shall tend to be closer to each other than unrelated Entities. Thus, by taking and Anticipating a small, local region of cortex, Anticipation can be performed on regions of Entities which are functionally and concernfully related, and so produce a Potentiality-for-Being without having to Interpret with respect to every Entity at its disposal. The Cycles - Making-Present of the Potentiality-for-Being Having fractured our cycle we are now in the position of having to determine what happens to the hundreds or thousands of Potentialities-for-Being that have been created. In all cases the Potentiality-for-Being may have two functions, two primary destinations, the relative importance of each function being determined by the nature of the Entity at hand. Firstly, an un-Interpreted Potentiality, one that has not been Made-Present, can be sent to the frontal cortex where its state as a possibility of the future may be used in planning motor action. This area of the brain is the centre for goal orientated movement planning, selection and execution. Secondly, the potentiality may be Made-Present and, as previously defined, must be Interpreted alongside a related sense. Yet at this point within the cortex the direct sensory inputs are far removed, both physically and conceptually. Instead the Potentiality-for-Being needs to be Interpreted with respect to the Now it has been derived from, and thence proceed to the thalamus, and possibly the frontal cortex. The thalamus acts as a monitoring point, a region where the status of Interpretation from all over the brain can be checked and coordinated. It is here that both the response to unfulfilled Potentilities-for-Being, Shock, and Attention Control are effected in response to the Made-Present afferents. The frontal cortex too has use of the Made-Present Potentialities, for in planning action the product of the Making-Present will give information on the current state of Dasein's Being-in-the-World and which Potentialities have not been fulfilled. There are other regions of the posterior cortices that play vital roles, concerned with language and declarative memories, which we shall attend to later. Created 9th October 2008 Last revised 30th October 2008 |