1. Mental Synthesis theory:
the mechanism of imagining novel objects involves temporal SYNCHRONIZATION
of independent neuronal ensembles.
Synchronization
no enhanced connections
The neuronal ensembles encoding those novel objects cannot synchronize on their own
since the parts forming those novel images have never been seen together and
therefore have no enhanced connections between them.
Six years ago I proposed that the mechanism of mental synthesis involves active SYNCHRONIZATION of independent neuronal ensembles.
Thus, the apple neuronal ensemble is actively synchronized with the dolphin neuronal ensemble,
and the two disparate objects are perceived together for the first time.
This is the central dogma of the mental synthesis theory. There is no direct prove of this hypothesis, but there are many indirect experiments consistent with this hypothesis.
Psychologists use the term mental synthesis to describe the process in which visual imagery is used to combine separate components into new, never-before-seen configurations (reviewed by Pearson & Logie, 2000).
Asynchronously firing neuronal ensembles
Perceived as two different objects
Synchronously firing neuronal ensembles
Perceived as one morphed image

2. The lateral prefrontal cortex as a puppeteer
PFC Puppeteer
Puppets in the posterior cortex
A major role of the lateral prefrontal cortex is to “manufacture” novel images by pulling neuronal ensembles into working memory and synchronizing them in time. These “manufactured” novel images allow humans to simulate the future and form the basis for such functions as language and reasoning.
While the central role of the lateral prefrontal cortex in planning and decision-making has been recognized for several decades, the specific neurological mechanism of those functions has been understood only in general terms. Planning and decision-making are thought to rely on such lateral prefrontal cortex functions as working memory and “time-integration”(Fuster JM, 2008), but specifics of time-integration are lacking. Current models of the lateral prefrontal cortex do not explicitly talk about synchronization of independent neuronal ensembles as a specific mechanism of planning and decision-making in humans. This monograph is the attempt to pinpoint a specific neurological mechanism responsible for visual planning and decision-making. Rather than describing the process in general terms of “time-integration,” the model proposed in this monograph offers synchronization of independent neuronal ensembles as the tentative mechanism of mental synthesis organized by the lateral prefrontal cortex.
By pulling the strings, the prefrontal cortex changes the firing phase of the retrieved neuronal ensembles thus synchronizing them into new mental constructs (Hipp, 2011; Sehatpour, 2008). In this process, the lateral prefrontal cortex synthesizes novel mental objects, mediates visual planning and visual problem solving.
Mental Synthesis
Synchronization

3. Lateral PFC
Since the lateral prefrontal cortex plays such a central role in mental synthesis in humans, it would be interesting to see if a homologous brain area was present in other animals.
The lateral prefrontal cortex is present in all primates but is absent in other animals including other mammals (Striedter GF, 2005; Petrides, 2002).
The lateral PFC is predominantly involved in time integrating and organizing functions (Fuster JM, 2008), such as working memory and mental synthesis.

4. Striedter GF, 2005: “Nonprimate mammals do have a PFC, but it apparently consists of only two major regions, rather than three as in primates. The two conserved prefrontal regions are the orbital prefrontal region, whose neurons respond preferentially to external stimuli that are likely to be rewarding or otherwise significant (Tremblay, 1999; Schoenbaum, 2001), and the anterior cingulate cortex, which mainly process information about the body’s internal state (Nauta, 1971; Luu, 2003). Collectively, these two regions contribute to what we might call the “emotional” aspect of decision making (Damasio, 1994; Dias, 1996; Allman, 2001). The third prefrontal region, which is generally known as the lateral, or granular prefrontal cortex, is apparently unique to primates (Preuss, 1995) and is concerned mainly with the “rational” aspects of decision making. Its neurons respond less rapidly than orbitofrontal neurons to rewarding stimuli and are more selective for the physical attributes of the stimuli, such as their spatial location (Wallis, 2003). Without those lateral prefrontal neurons, primates become less able to retrieve and manipulate information about objects in the outside world (Owen, 1999). In the context of decision making, this probably means that the lateral prefrontal cortex helps primates to consider alternative interpretations of external objects and to construct alternative scenarios of how to interact with them. ... The notion of the lateral prefrontal cortex being a primate innovation originated with Brodmann and has recently been championed by Todd Preuss (1995a). Central to their argument is that small celled granular layer that characterizes the lateral prefrontal cortex in primates is lacking in most other mammals. This finding does indeed suggest that the lateral PFC is unique to primates.”

5. What is so special about primates?
55-million-year-old primate fossil in Chinadubbed Archicebus Achilles
Separated from the rest of mammals some 70 million years ago.
The mammalian ancestors of primates were small nocturnal animals who spent most of their time underground. Following the demise of dinosaurs some 66 million years ago, the competition for aboveground resources diminished and primates evolved into diurnal arboreal animals.
Primates came to occupy the evolutionary niche that heavily depends on vision rather than olfaction for food search and predator avoidance. Reliance on an enhanced sense of vision became the defining feature of all primates.

6. most primate-typical features reflect the development of the visual system:
primate eyes evolved to a more frontally placed position (presumably to improve depth perception)
Primates also acquired an additional color receptor to better differentiate red from green

7. Some people (2.4% of males) still have two color receptors.UV IR
Most mammals, including dogs and cats, have only two different kinds of color receptors.
Why?
A remote vertebrate ancestor of all mammals possessed 4 color receptors- most fish, reptiles and birds still have 4 color receptors
However nocturnal mammalian ancestors lost two of four cones in the retina at the time of dinosaurs  all mammals, with the exception of some primates still have only 2 color receptors.
Some primates (including apes) have acquired the third color receptors.
Some people (2.4% of males) still have two color receptors. UV IR
actual
Most placental mammals, from which primates evolved 70 million years ago, have only two different kinds of color receptors. These receptors have peak sensitivity in the blue and in the yellow-green regions of the spectrum. Thus, most placental animals, including dogs and cats, cannot distinguish green and red colors. The additional color receptor acquired by primates helped them to select ripe fruit, which tends to be red or orange against the background of green leaves (Osorio D, 1996; Regan BC, 2001) as well as to pick out the young leaves, which tend to be red in Africa (Dominy NJ, 2001) and are more nutritious and digestible.
Perceived

8. Primates primarily use vision to direct skilled movements, as well as to search for food and avoid predators.
Rodents can also grasp and manipulate objects using the tips of their digits, however rodents are much less visual. Their skilled movements are primarily directed by the sense of touch and olfaction: rats without vision are able to locate and reach for food as quickly as they did before being blinded, but rats without olfaction, who therefore rely more on vision, are significantly slower (Whishaw, 2003).

9. Primates occupied the “fine-branch niche”
Collecting ripe fruits and leaves, and hunting for insects.
Primates also acquired more direct corticospinal projections (connections between the cortical neurons and the motor neurons in the spinal cord, which increase fine control over muscles)
an additional cortical area (called the ventral premotor cortical area) specialized for arm and mouth movements (Preuss, 1996).
Furthermore, the control of hand and foot movement benefitted from an increased somatosensory cortex, which, in primates, added several cortical areas that have no homologues in non-primates.
Striedter concludes: “diverse evolutionary changes in the visual, motor and somatosensory systems all interacted to give early primates exceptionally good hand-eye coordination, which must have come in handy in the fine-branch niche”.

10. A primate’s survival in the “fine-branch niche” depended on its ability to visually detect predators, prey, and edible objects.
Consequently, primates were under constant evolutionary pressure to recognize those objects faster and from a greater distance.
Visually identifying ripe fruits, leaves, and insects relies on a primate’s ability to separate those objects from the background and from other objects.
Fruits are normally hidden under leaves, leaves in the rainforest merge into thick foliage, and insects tend to camouflage their appearance.
Predators are also often camouflaged and therefore merge into the background.
Furthermore fruits, leaves, insects, and predators often remain motionless, and visual detection of motionless objects is significantly more difficult than detection of moving objects.

11. Can you find a camouflaged frog amongst the dead leaves in this illustration from the 2015 Johnston Club calendar?

12. http://www. dailymail. co
A Leopard conceals herself in vegetation at the base of a tree in Kruger National Park, Transvaal, South Africa

13. http://www. dailymail. co
A wolf peering out from behind a tree trunk in an autumn Montana forest

16. What part of the brain is the primary source of top-down attentional control in object perception?

17. What part of the brain is the primary source of top-down attentional control in object perception?
Meet our old friend the prefrontal cortex. The prefrontal cortex is involved in the maintenance of goal-related information as well as in attentional selection and focus shifting (Fuster JM, 2008).
To succeed in an environment where prey and predators were often motionless, camouflaged, and partially hidden, primates had to rely heavily on their prefrontal cortex to interpret ambiguous sensory input throughout the 70 million years of their evolution.
The prefrontal cortex of diurnal arboreal animals, who relied on their sense of vision to detect prey and predator from afar, was under constant evolutionary pressure to improve its ability to actively steer perception to coordinate subjective goals with objective reality.

18. Primates primarily detect predators and prey visually
THE SNAKE DETECTION THEORY (LYNNE A. ISBELL, 2009)
Species
Primates exposed to greater predation by venomous snakes acquired a better visual system compared to primates not exposed to venomous snakes (Isbell LA, 2009).
Prosimians in Madagascar
New World monkeys of South America (platyrrhines)*
Old World monkeys and apes (catarrhines)
Homo habilis
Modern Humans
Immobile Predators
But primates are special.
Primates primarily detect predators and prey visually.
Lynne Isbell, a Professor of Anthropology at University of California, Davis, proposed a compelling theory of the evolution of primates. She noticed that snakes were the first of the major predators of primates and that the snakes are usually camouflaged and immobile and, therefore, difficult to detect. She also noted that primates exposed to greater predation by snakes acquired a better visual system. Prosimians in Madagascar that have never coexisted with venomous snakes have the least developed visual system among primates. New World monkeys of South America that have had interrupted exposure to venomous snakes have a better visual system. Old World monkeys and apes that have had continuous coexistence with venomous snakes for over 60 million years have an even better visual system.
Visual System
interrupted exposure to venomous snakes
continuous coexistence with venomous snakes for over 60 million years
*The last exposure of the New World monkeys of South America (platyrrhines) to rattlesnakes lasted for only three million years

19. Recall: some animals cannot visually detect a still object even when it is unambiguous
To locate an immobile prey, most predators use smell or others senses (e.g. infrared radiation), not vision.
For these reptiles it was evolutionarily “easier” to acquire this additional system rather than to develop computational support for the existing visual sensory input.
Visual primates, on the other hand, “chose” to expand their computational system in order to improve detection of motionless ambiguous objects.
Only few snakes can detect infrared radiation: A python (top) and rattlesnake illustrating the positions of the pit organs. Red arrows point to the pit organs; Black arrow point to the nostril.

20. The Mental Synthesis theory (Vyshedskiy, 2008) extends the Snake Detection theory to the evolution of hominins
Species
Prosimians in Madagascar
New World monkeys of South America (platyrrhines)
Old World monkeys and apes (catarrhines)
Homo habilis
Modern Humans
Immobile Predators
The Mental Synthesis theory extends the Snake Detection theory to the evolution of hominins. The theory observes that hominins foraging in the savanna were exposed to an even greater range of immobile stalking predators …
Visual System
Hominins foraging in the savanna were exposed to an even greater range of IMMOBILE STALKING predators…

21. but then increased significantly in two major growth spurts:
the brain volume increased relatively slowly in australopiths from 350 cm3 to 450 cm3 over 3.5 million years,
but then increased significantly in two major growth spurts:
around 1.8 million years ago and
about 100,000 years ago

22. The lateral prefrontal cortex underwent the greatest transformation under this evolutionary pressure.

23. Different brain areas are scaled up differently:
the volume of the olfactory bulb in humans is only 30% as large as would be expected in a primate brain of our size,
the volume of V1 is only 60% as large as expected.
Remarkably, the volume of Brodmann area 10 (frontopolar cortex) is nearly 200% as large as expected for a primate brain of our size.
Because neural tissue is metabolically expensive, changes in relative proportions of different brain areas are likely to be behaviorally adaptive. Accordingly, paleoneurobiologists often deduce that the survival benefit provided by the olfactory sense did not change or has reduced in hominins, while the survival benefit provided by Brodmann area 10, has increased significantly.

24. Brodmann measured the PFC size as percent of the total cortex using the cytoarchitectonic method:
29% of in humans,
17% in the chimpanzee,
11.5% in the gibbon and the macaque,
8.5% in the lemur,
7% in the dog, and
3.5% in the cat
Semendeferi K, 2001 (using a precise cytoarchitectonic method): neuronal density in human Brodmann area 10 was around half of that of other primates  Brodmann area 10 in humans has a significantly greater portion of its volume dedicated to connections between neurons
Conclusion: Humans’ Brodmann area 10 is nearly 200% as large as expected for a primate brain of our size and that increase in size is due to greater number of connections and myelination (Schoenemann PT, 2005)
differences in behavior amongst species are generally reflected in differences in their cortical maps.
For example, echolocating bats have greatly expanded cortical areas dedicated to processing of auditory signals (in the ghost bat Macroderma gigas this cortical area accounts for more than half the cortex),
whereas primarily subterranean mole species have markedly reduced visual cortical areas (Krubitzer L, 1995).
Among modern humans, the volume of the white matter in the prefrontal cortex has been found to be positively correlated with at least one cognitive task known to be mediated by the prefrontal cortex: the Stroop test, which tests the ability to extract and focus on relevant cues in the face of distractors (Schoenemann PT, 2000).

25. Greater differential myelination
Slower conduction velocity
Slower conduction velocity
Faster conduction velocity
Faster conduction velocity
Some fibers are myelinated with up to a hundred layers of myelin while OTHERS are myelinated with just a few layers.
Faster conduction velocity
Faster conduction velocity

26. These connections must be fine-tuned to become synchronous.
Thus, the synchronization mechanism poses a serious challenge that every human needs to solve during development:
These connections must be fine-tuned to become synchronous.
We don’t actually know how the prefrontal cortex synchronizes its connections
but in other systems that have been studied, synchronicity is achieved by changes in the conduction velocity along the connecting fibers.
Without a mechanism that could equalize transit times, the signal from the prefrontal cortex would arrive to its targets in the posterior cortex at different times.
This synchronization mechanism poses a serious challenge that every human needs to solve during development:
These connections must be fine-tuned to become synchronous.

27. More myelin -> faster conduction velocity
Less myelin -> slower conduction velocity
To summarize, the current consensus is that MYELINATION is the primary factor producing uniform conduction time.
Longer fibers are wrapped with many extra layers of myelin to increase the conduction velocity.
Hypothesis: myelination is the primary factor producing uniform conduction time throughout the cortex

28. The lateral prefrontal cortex as a puppeteer
PFC Puppeteer
Puppets in the posterior cortex
A major role of the lateral prefrontal cortex is to “manufacture” novel images by pulling neuronal ensembles into working memory and synchronizing them in time. These “manufactured” novel images allow humans to simulate the future and form the basis for such functions as language and reasoning.
While the central role of the lateral prefrontal cortex in planning and decision-making has been recognized for several decades, the specific neurological mechanism of those functions has been understood only in general terms. Planning and decision-making are thought to rely on such lateral prefrontal cortex functions as working memory and “time-integration”(Fuster JM, 2008), but specifics of time-integration are lacking. Current models of the lateral prefrontal cortex do not explicitly talk about synchronization of independent neuronal ensembles as a specific mechanism of planning and decision-making in humans. This monograph is the attempt to pinpoint a specific neurological mechanism responsible for visual planning and decision-making. Rather than describing the process in general terms of “time-integration,” the model proposed in this monograph offers synchronization of independent neuronal ensembles as the tentative mechanism of mental synthesis organized by the lateral prefrontal cortex.
By pulling the strings, the prefrontal cortex changes the firing phase of the retrieved neuronal ensembles thus synchronizing them into new mental constructs (Hipp, 2011; Sehatpour, 2008). In this process, the lateral prefrontal cortex synthesizes novel mental objects, mediates visual planning and visual problem solving.
Mental Synthesis
Synchronization

29. - DANIEL J. POVINELLI (20min, 2013) - https://www. youtube. com/watch
- Herbert S. Terrace - Nim Chimpsky DVD