A hierarchy of temporal receptive windows in our brains

Here is the abstract from a fascinating study by Hasson et al. on how our visual system assembles time narratives - as during watching a movie - followed by part of one of the figures from the paper:

Real-world events unfold at different time scales and, therefore, cognitive and neuronal processes must likewise occur at different time scales. We present a novel procedure that identifies brain regions responsive to sensory information accumulated over different time scales. We measured functional magnetic resonance imaging activity while observers viewed silent films presented forward, backward, or piecewise-scrambled in time. Early visual areas (e.g., primary visual cortex and the motion-sensitive area MT+) exhibited high response reliability regardless of disruptions in temporal structure. In contrast, the reliability of responses in several higher brain areas, including the superior temporal sulcus (STS), precuneus, posterior lateral sulcus (LS), temporal parietal junction (TPJ), and frontal eye field (FEF), was affected by information accumulated over longer time scales. These regions showed highly reproducible responses for repeated forward, but not for backward or piecewise-scrambled presentations. Moreover, these regions exhibited marked differences in temporal characteristics, with LS, TPJ, and FEF responses depending on information accumulated over longer durations (~36 s) than STS and precuneus (~12 s). We conclude that, similar to the known cortical hierarchy of spatial receptive fields, there is a hierarchy of progressively longer temporal receptive windows in the human brain.


Figure- Maps are shown on inflated (top) and unfolded (bottom) left and right hemispheres. White outlines mark the main regions in which responses were not time reversible. Anatomical abbreviations: ITS, inferior temporal sulcus; LS, lateral sulcus; STS, superior temporal sulcus; TPJ, temporal parietal junction; CS, central sulcus; IPS, intraparietal sulcus. Several higher-order visual areas were functionally defined based on their responses to faces (red outlines), objects (blue outlines), and houses (green outlines). Functionally and anatomically defined cortical areas: V1, primary visual cortex; MT+, MT complex responsive to visual motion; PPA, parahippocampal place area; FFA, fusiform face area; LO, lateral occipital complex responsive to pictures of objects; STS-face, area in superior temporal sulcus responsive to faces.

Anxiety: fear in seach of a cause

The title of this post is a pithy definition that Patricia Pearson gives in her recent book, "A BRIEF HISTORY OF ANXIETY... Yours and Mine", reviewed by William Grimes in the NY Times. From that review some clips:

Everywhere and nowhere, anxiety... In many cases it is the fear of fear itself, a free-floating, nebulous entity that, like a mutant virus, feeds on any available host. Reason is powerless against it. Ms. Pearson argues, in fact, that rationalism, intended to banish superstition and fear, has instead removed one of the most effective weapons against anxiety, namely religious faith and ritual.

...the worship of reason and science, by encouraging the notion that human beings can control their environment, has created a terrible fault line in the modern psyche, although not all societies suffer equally. Mexicans have lots to worry about but don’t. The World Mental Health Survey, conducted in 2002, found that only 6.6 percent of Mexicans had ever experienced a major episode of anxiety or depression. Meanwhile, to their north, 28.8 percent of the American population has been afflicted with anxiety, the highest level in the world. Mexicans who move to the United States adapt, becoming more anxious.

Depressing news: antidepressants don't work?

In the April issue of Nature Reviews Neuroscience, Claudia Wiedemann reviews reactions to a meta analysis by Kirsch et al. of data on antidepressant drugs submitted to the Food and Drug Administration that resulted in the licensing of four of the most commonly prescribed antidepressants: the selective serotonin reuptake inhibitors (SSRIs) Prozac, Seroxat, Effexor and Serzone. For anything but the most severe depression, there was no difference between the drugs and placebos. Kirsch suggests that there is little reason to prescribe anti-depressant medication to any but the most severely depressed patients. The conclusion of the study:

Drug–placebo differences in antidepressant efficacy increase as a function of baseline severity, but are relatively small even for severely depressed patients. The relationship between initial severity and antidepressant efficacy is attributable to decreased responsiveness to placebo among very severely depressed patients, rather than to increased responsiveness to medication.

Differing perception of facial expressions in the East and West

Nagourney describes a study in the March issue of The Journal of Personality and Social Psychology reinforcing previous work showing that Westerners are more likely to see emotions as individual feelings while East Asians see them as inseparable from the feelings of the group. Many researchers have suggested that East Asians take a more holistic view of the world. Here is the abstract of the Masuda et al. article:

Two studies tested the hypothesis that in judging people's emotions from their facial expressions, Japanese, more than Westerners, incorporate information from the social context. In Study 1, participants viewed cartoons depicting a happy, sad, angry, or neutral person surrounded by other people expressing the same emotion as the central person or a different one. The surrounding people's emotions influenced Japanese but not Westerners' perceptions of the central person. These differences reflect differences in attention, as indicated by eye-tracking data (Study 2): Japanese looked at the surrounding people more than did Westerners. Previous findings on East-West differences in contextual sensitivity generalize to social contexts, suggesting that Westerners see emotions as individual feelings, whereas Japanese see them as inseparable from the feelings of the group.

Heritability of cooperative behavior

A study of the behaviors of monozygotic versis dizygotic twins (i.e. 'identical' vs. 'non-identical' twins) in a classical cooperation game yields evidence for genetic influences on yet another of our behaviors - how trusting we are:

Although laboratory experiments document cooperative behavior in humans, little is known about the extent to which individual differences in cooperativeness result from genetic and environmental variation. In this article, we report the results of two independently conceived and executed studies of monozygotic and dizygotic twins, one in Sweden and one in the United States. The results from these studies suggest that humans are endowed with genetic variation that influences the decision to invest, and to reciprocate investment, in the classic trust game. Based on these findings, we urge social scientists to take seriously the idea that differences in peer and parental socialization are not the only forces that influence variation in cooperative behavior.

Our results are complementary to work on the neurological and hormonal substrates of behavior in the trust game and other similar social dilemma games...Enhanced oxytocin levels have been documented in subjects who received a monetary transfer that reflected an intention of trust, and later work has demonstrated that exogenously administered oxytocin increases trust. Scholars have also documented associations between cortisol and trust. These hormonal studies, therefore, indicate that further study of polymorphisms of CYP11B1, OXTR, and other genes involved in the expression and regulation of these hormones may explain part of the genetic effect on cooperation. In fact, one research team has already identified a polymorphism in the AVPR1a gene that is associated with related behavior in the dictator game.

Neuroimaging shows use of self thoughts to infer others' mental states

Jenkins et al. offer a fascinating study of how we infer the mental states of others (mentalize), making use of a phenomenon (repetition suppression) that I had not been aware of before. Here I've done a cut/paste/edit from the abstract and article to try to outline the basic idea, and also show the central figure:

One useful strategy for inferring others' mental states (i.e., mentalizing) may be to use one's own thoughts, feelings, and desires as a proxy for those of other people (This approach to social cognition is alternately described as "simulationist," "projectionist," or "self-referential".) A dorsal aspect of the medial prefrontal cortex has been associated with mentalizing about people perceived to be dissimilar from oneself, whereas a more ventral aspect of medial prefrontal cortex (vMPFC) has been linked to mentalizing about those perceived to be similar. Critically, this vMPFC region also has been observed repeatedly during tasks that require participants to introspect about their own mental experiences, suggesting a connection between tasks that require self-referential thought and those that require inferences about the mental states of similar others.

Because such techniques integrate neural activity across hundreds of thousands of neurons, activation of the same brain voxel by different tasks might occur because each activates distinct, but neighboring or interdigitated, neuronal populations. In this way, two tasks could possibly coactivate the same brain voxel despite engaging different sets of neurons that subserve disparate cognitive processes.

This technical limit can now be circumvented by recently developed paradigms that support stronger conclusions regarding the coactivation of the same neurons by different stimuli or different tasks. These techniques rely on an effect known as "repetition suppression," the observation that neural activity in stimulus-sensitive brain regions is typically reduced when a stimulus is repeated

Suppression across two stimuli indicates that the same (or at least a largely overlapping) population of neurons is engaged by both stimuli. For example, a demonstration of repetition suppression for the number "3" when it follows "4" but not when it follows "40" might suggest that a relatively high proportion of the neurons that code for the number "3" also participate in representations of similar numerosities (such as "4"), but not in representations of more distant numerosities.

If (i) repeatedly considering one's own mental states produces repetition suppression in self-sensitive regions such as vMPFC, and (ii) one engages in self-referential processing when considering the minds of similar others, then (iii) repetition suppression also should be observed when perceivers first mentalize about a similar other and then introspect about self.

Consistent with this hypothesis this perceivers spontaneously engage in self-referential processing when mentalizing about particular individuals, vMPFC response was suppressed when self-reflections followed either an initial reflection about self or a judgment of a similar, but not a dissimilar, other. These results suggest that thinking about the mind of another person may rely importantly on reference to one's own mental characteristics.

Here is the basic figure:

Figure legend (click on figure to enlarge it). A region of vMPFC (–6, 45, 3; 47 voxels in extent) was defined from an explicit self-reference task in which judgments of one's own personality characteristics were compared with judgments of another person (i.e., self > other). On a separate task, participants completed a series of paired judgments, in which they introspected about their own preferences and opinions immediately after one of three types of judgments: (i) an initial report about self (self-after-self), (ii) a judgment of a person with the same sociopolitical attitudes as oneself (self-after-similar), or (iii) a judgment of a person with opposing attitudes (self-after-dissimilar). On an equal number of trials, participants considered the identical question for prime and self or a different question across the two phases. The bar graph depicts the BOLD response associated with these self-reports after subtracting out the response associated with the initial judgment (see Methods); values therefore represent the additional BOLD response specifically associated with subsequent judgments of self. For comparison purposes, the figure includes the response in this region to self-reports made in isolation (gray bar). Significant repetition suppression was observed for self-reports that followed either an initial self-report (blue bars) or a judgment of a similar other (red bars), but not judgments of a dissimilar other (green bars). Error bars represent the 95% confidence interval for within-subject designs.

Like many of the cognitive heuristics that typically serve us well, but periodically lead to undesirable or maladaptive behavior, the use of self-reference in mentalizing may be a double-edged sword: a useful strategy for providing rich and accurate insights into the minds of similar individuals, but rife with the potential to exclude those minds assumed at first glance to be different from our own.

Emonomics

Berreby offers an entertaining review of Ariely's new book "Predictably Irrational," which deals with behavioral economics - the experimental study of what people actually do when they buy, sell, change jobs, marry and make other real-life decisions. The book is a concise summary of why today’s social science increasingly treats the markets-know-best model as a fairy tale.

To see how arousal alters sexual attitudes, for example, Ariely and his colleagues asked young men to answer a questionnaire — then asked them to answer it again, only this time while indulging in Internet pornography on a laptop wrapped in Saran Wrap. (In that state, their answers to questions about sexual tastes,, violence and condom use were far less respectable.) To study the power of suggestion, Ariely’s team zapped volunteers with a little painful electricity, then offered fake pain pills costing either 10 cents or $2.50 (all reduced the pain, but the more expensive ones had a far greater effect). To see how social situations affect honesty, they created tests that made it easy to cheat, then looked at what happened if they reminded people right before the test of a moral rule. (It turned out that being reminded of any moral code — the Ten Commandments, the non-existent “M.I.T. honor system” — caused cheating to plummet.)

A bit of piano...

I thought I would punctuate the stream of 'serious' posts with a paste from my piano recordings, this being "Three Fantastic Dances" by Shostakovitch:

Most popular consciousness articles for February

From the ASSC downloads archive:
1. Koriat, A. (2006) Metacognition and Consciousness. In: Cambridge handbook
of consciousness. Cambridge University Press, New York, USA.http://eprints.assc.caltech.edu/175/
2. Sagiv, N. and Ward, J. (2006) Crossmodal interactions: lessons from synesthesia. In: Visual Perception, Part 2. Progress in Brain Research,
Volume 155.http://eprints.assc.caltech.edu/224
3. Seth, A.K. and Baars, B.J. (2005) Neural Darwinism and Consciousness. Consciousness and Cognition, 14. pp. 140-168.http://eprints.assc.caltech.edu/163/
4. Dehaene, S., Changeux, J.-P., Naccache, L., Sackur, J. and Sergent, C. (2006) Conscious, preconscious, and subliminal processing: a testable taxonomy. Trends in Cognitive Science, 10 (5). pp. 204-211.http://eprints.assc.caltech.edu/20/
5. Gennaro, R. J. (2007) Representationalism, peripheral awareness, and the transparency of experience. Philosophical Studies.http://eprints.assc.caltech.edu/218/

The maturing architecture of the brain's default network

From Raichle and others in the St. Louis group, an interesting story on the development of the brain network we most likely use for introspective mental activity:

In recent years, the brain's "default network," a set of regions characterized by decreased neural activity during goal-oriented tasks, has generated a significant amount of interest, as well as controversy. Much of the discussion has focused on the relationship of these regions to a "default mode" of brain function. In early studies, investigators suggested that, the brain's default mode supports "self-referential" or "introspective" mental activity. Subsequently, regions of the default network have been more specifically related to the "internal narrative," the "autobiographical self," "stimulus independent thought," "mentalizing," and most recently "self-projection." However, the extant literature on the function of the default network is limited to adults, i.e., after the system has reached maturity. We hypothesized that further insight into the network's functioning could be achieved by characterizing its development. In the current study, we used resting-state functional connectivity MRI (rs-fcMRI) to characterize the development of the brain's default network. We found that the default regions are only sparsely functionally connected at early school age (7–9 years old); over development, these regions integrate into a cohesive, interconnected network.


Figure legend - (click on figure to enlarge). Voxelwise resting-state functional connectivity maps for a seed region (solid black circle) in mPFC (ventral: –3, 39, –2). (A) Qualitatively, the rs-fcMRI map for the mPFC (ventral) seed region reveals the commonly observed adult connectivity pattern of the default network. The connectivity map in children, however, significantly deviates from that of the adults. Functional connections with regions in the posterior cingulate and lateral parietal regions (highlighted with blue open circles) are present in the adults but absent in children. (B) These qualitative differences between children and adults are confirmed by the direct comparison (random effects) between adults and children. mPFC (ventral) functional connections with the posterior cingulate and lateral parietal regions are significantly stronger in adults than children.

Analogies between cultural and genetic evolution - the case of polynesian canoes

Rogers and Ehrlich, in an open access article, have made an important contribution to understanding cultural evolution. Here are some clips from an accompanying commentary by Stephen Shennan, followed by the article abstract. The link to the article takes you to pictures of the canoe features studied.

In the most general terms, parallel mechanisms for inheritance, mutation, selection, and drift act on culture as they do on genes...In the case of culture, the inheritance mechanism is social learning: People learn ways to think and act from others...natural selection can also act on cultural attributes, in the sense that those individuals who inherit or acquire certain cultural attributes may have a greater probability of surviving and/or reproducing than those who do not; as a result, those cultural attributes will become increasingly prevalent. For example, it is clear that, in many parts of the world, adopting an agricultural rather than a hunting-and-gathering way of life led to greater reproductive success; as a result, the cultural traits that characterize agriculture spread and, in some cases, subsequently influenced genetic evolution [e.g., the ability to digest lactose]...It is also important to look at things from what Dawkins called "the meme's eye-view," the perspective of the cultural attributes themselves...in the case of the canoe attributes analyzed by Rogers and Ehrlich, these culturally transmitted features are the data that archaeologists and anthropologists have available...What Rogers and Ehrlich have done is make progress in this area by showing that variation that is believed to be under selection is patterned differently from other variation that is believed not to be under selection, or at least not in the same way. It seems to be more conservative and, therefore, under negative selection. Perhaps more surprisingly, they find that there is no correlation at all in the similarities between island groups in terms of functional canoe variation and the similarities based on symbolic variation. One might have expected some correlation, either because both would be affected by the distance between the islands, or because the process of island colonization by groups in canoes would have brought both their functional and their symbolic attributes. The fact that selection appears to have been sufficiently powerful to overwhelm evidence of descent history is extremely interesting and confirms the importance of regarding cultures not as hermetically sealed entities, a bit like species, but as bundles of distinct packages of traits affected by different forces

The Rogers and Ehrlich abstract:

It has been claimed that a meaningful theory of cultural evolution is not possible because human beliefs and behaviors do not follow predictable patterns. However, theoretical models of cultural transmission and observations of the development of societies suggest that patterns in cultural evolution do occur. Here, we analyze whether two sets of related cultural traits, one tested against the environment and the other not, evolve at different rates in the same populations. Using functional and symbolic design features for Polynesian canoes, we show that natural selection apparently slows the evolution of functional structures, whereas symbolic designs differentiate more rapidly. This finding indicates that cultural change, like genetic evolution, can follow theoretically derived patterns.

Amazing Images...

From the Wellcome Image Awards Gallery:

A new brain book...

The new book "Brain Rules" looks interesting, it appears to be an enlightened self-help manual based on basics of brain function.

Our motor adaptation as a process of reoptimization.

Because I'm a classical pianist and am continually trying to optimize the motor performance involved, I'm fascinated by articles like this one by Izawa et al. They oppose the common assumption that the goal of motor adaptation is to compensate for some perturbation by returning to a previous baseline condition assumed to be optimal. Here is their abstract:

Adaptation is sometimes viewed as a process in which the nervous system learns to predict and cancel effects of a novel environment, returning movements to near baseline (unperturbed) conditions. An alternate view is that cancellation is not the goal of adaptation. Rather, the goal is to maximize performance in that environment. If performance criteria are well defined, theory allows one to predict the reoptimized trajectory. For example, if velocity-dependent forces perturb the hand perpendicular to the direction of a reaching movement, the best reach plan is not a straight line but a curved path that appears to overcompensate for the forces. If this environment is stochastic (changing from trial to trial), the reoptimized plan should take into account this uncertainty, removing the overcompensation. If the stochastic environment is zero-mean, peak velocities should increase to allow for more time to approach the target. Finally, if one is reaching through a via-point, the optimum plan in a zero-mean deterministic environment is a smooth movement but in a zero-mean stochastic environment is a segmented movement. We observed all of these tendencies in how people adapt to novel environments. Therefore, motor control in a novel environment is not a process of perturbation cancellation. Rather, the process resembles reoptimization: through practice in the novel environment, we learn internal models that predict sensory consequences of motor commands. Through reward-based optimization, we use the internal model to search for a better movement plan to minimize implicit motor costs and maximize rewards.

Relativity of space, time and magnitude representation in our brains

Here are some simple and elegant experiments that shows how relativistic our time sense is. Our two cerebral hemispheres expand (right hemisphere) or contract (left hemisphere) time perception when acting alone, and then let magnitude cues in the stimulus influence perceived time when acting together. Vicario et al. investigated whether duration judgments of digit visual stimuli were biased depending on the side of space where the stimuli were presented (i.e. to which hemisphere) and on the magnitude of the stimulus itself:

Different groups of healthy subjects performed duration judgment tasks on various types of visual stimuli. In the first two experiments visual stimuli were constituted by digit pairs (1 and 9), presented in the centre of the screen or in the right and left space. In a third experiment visual stimuli were constituted by black circles. The duration of the reference stimulus was fixed at 300 ms. Subjects had to indicate the relative duration of the test stimulus compared with the reference one. The main results showed that, regardless of digit magnitude, duration of stimuli presented in the left hemispace is underestimated and that of stimuli presented in the right hemispace is overestimated. On the other hand, in midline position, duration judgments are affected by the numerical magnitude of the presented stimulus, with time underestimation of stimuli of low magnitude and time overestimation of stimuli of high magnitude. These results argue for the presence of strict interactions between space, time and magnitude representation on the human brain.

A fiery piano performance...

This makes me cringe..... On March 8, pianist Yosuke Yamashita donned a fireproof suit and played a burning piano on a beach in Ishikawa prefecture. The improvised jazz performance went for about 10 minutes until the flames rendered the piano silent.

In Most Species, Faithfulness Is a Fantasy

This post has the title of a great article by Natalie Angier in the NYTimes Science section. Elliot Spitzer was doing nothing that hasn't been done by males and females of thousands of other species - representatives of every taxonomic twig on the great tree of life.

Even the “oldest profession” that figured so prominently in Mr. Spitzer’s demise is old news. Nonhuman beings have been shown to pay for sex, too. Reporting in the journal Animal Behaviour, researchers from Adam Mickiewicz University and the University of South Bohemia described transactions among great grey shrikes, elegant raptorlike birds with silver capes, white bellies and black tails that, like 90 percent of bird species, form pair bonds to breed. A male shrike provisions his mate with so-called nuptial gifts: rodents, lizards, small birds or large insects that he impales on sticks. But when the male shrike hankers after extracurricular sex, he will offer a would-be mistress an even bigger kebab than the ones he gives to his wife — for the richer the offering, the researchers found, the greater the chance that the female will agree to a fly-by-night fling.

In another recent report from the lubricious annals of Animal Behaviour entitled “Payment for sex in a macaque mating market,” Michael D. Gumert of Hiram College described his two-year study of a group of longtailed macaques that live near the Rimba ecotourist lodge in the Tanjung Puting National Park of Indonesia. Dr. Gumert determined that male macaques pay for sex with that all-important, multipurpose primate currency, grooming. He saw that, whereas females groomed males and other females for social and political reasons — to affirm a friendship or make nice to a dominant — and mothers groomed their young to soothe and clean them, when an adult male spent time picking parasites from an adult female’s hide, he expected compensation in the form of copulation, or at the very least a close genital inspection. About 89 percent of the male-grooming-female episodes observed, Dr. Gumert said in an interview from Singapore, where he is on the faculty of Nanyang Technological University, “were directed toward sexually active females” with whom the males had a chance of mating.

Influence of language on brain activity underlying perceptual decisions

Following up on my Feb. 22 post on the same topic, I pass on the abstract of work by Tan et al., showing that language-processing areas of the brain are directly involved in visual perceptual decisions:

Well over half a century ago, Benjamin Lee Whorf [Carroll JB (1956) Language, Thought, and Reality: Selected Writings of Benjamin Lee Whorf (MIT Press, Cambridge, MA)] proposed that language affects perception and thought and is used to segment nature, a hypothesis that has since been tested by linguistic and behavioral studies. Although clear Whorfian effects have been found, it has not yet been demonstrated that language influences brain activity associated with perception and/or immediate postperceptual processes (referred hereafter as "perceptual decision"). Here, by using functional magnetic resonance imaging, we show that brain regions mediating language processes participate in neural networks activated by perceptual decision. When subjects performed a perceptual discrimination task on easy-to-name and hard-to-name colored squares, largely overlapping cortical regions were identified, which included areas of the occipital cortex critical for color vision and regions in the bilateral frontal gyrus. Crucially, however, in comparison with hard-to-name colored squares, perceptual discrimination of easy-to-name colors evoked stronger activation in the left posterior superior temporal gyrus and inferior parietal lobule, two regions responsible for word-finding processes, as demonstrated by a localizer experiment that uses an explicit color patch naming task. This finding suggests that the language-processing areas of the brain are directly involved in visual perceptual decision, thus providing neuroimaging support for the Whorf hypothesis.

Figure legend (Click on figure to enlarge it). Brain activations elicited by color perception and explicit color naming. (A and B) Areas showing significant activation during perceptual discrimination of easy-to-name colors in comparison with perceptual discrimination of hard-to-name colors. A and B are lateral view and axial sections, respectively. Two regions of greatest interest are the left posterior superior temporal gyrus (BA 22; x = –57, y = –38, z = 18) and the left inferior parietal lobule (BA 40; x = –61, y = –32, z = 27). (C and D) Percentage BOLD signal change (± SEM) at voxels of maximal difference between the two color-discrimination conditions in the two regions of interest. (E and F) Areas showing significant activation in explicit color naming against color word naming as baseline. E and F are lateral view and axial sections, respectively. The left posterior superior temporal gyrus and the left inferior parietal lobule are critically engaged by the color naming task.

Reality getting to you?

Perhaps try escaping into one of these devices? (I don't think I'll go there just yet....)

The brain and emotion-laden images: two pathways

A collaborative study has considered several models that might explain why our behavior can be rapidly influenced by an emotional stimulus (a snake like shape that we jump away from) before the stimulus has been fully processed (and we realize that it is a coil of rope). Information influences action before perception is complete. The data can only be accounted for by a two-pathway architecture by which emotional visual information proceeds more directly via one pathway to the amygdala (and thus influences action) and at the same time more slowly by the second conventional visual pathway that establishes the perception of the actual nature of the stimulus. I'm showing here the abstract and then the basic figure describing the models.

Visual attention can be driven by the affective significance of visual stimuli before full-fledged processing of the stimuli. Two kinds of models have been proposed to explain this phenomenon: models involving sequential processing along the ventral visual stream, with secondary feedback from emotion-related structures ("two-stage models"); and models including additional short-cut pathways directly reaching the emotion-related structures ("two-pathway models"). We tested which type of model would best predict real magnetoencephalographic responses in subjects presented with arousing visual stimuli, using realistic models of large-scale cerebral architecture and neural biophysics. The results strongly support a "two-pathway" hypothesis. Both standard models including the retinotectal pathway and nonstandard models including cortical–cortical long-range fasciculi appear plausible.

Tested models. (Click on image to enlarge) a, Basic components of the generic model, including all the possible types of connections used in this report, within and between two connected regions. Top, Cortical regions are modeled as three layered columns with three types of neuronal populations (pyramidal, excitatory spiny, and inhibitory interneurons), connected through intrinsic and extrinsic (feedforward and backward) connections. Bottom, The dynamics is mathematically expressed at the level of neural populations and is defined by nonlinear differential equations in which the change of state of each unit dxi/dt depends on its current state xi(t); thalamic inputs ui(t); average firing rate of afferents S(xj(t – {delta}ij)); transmission delays {delta}ij; forward, backward, and intrinsic effective connectivity matrices CF, CB, Ci, and other parameters. The MEG signal M is assumed to be related to the local average current density x generated by pyramidal populations through a linear forward model M = GX. b, Lateral, mesial, and ventral views of the mapping of the regions of interest common to all models on a reference cortical tessellation [for color code, see c (top row)]. c, Schematic representation of the architecture of the tested models. All the models share the same basic layout (see text). Null model, Simple feedforward model. Model 1, Adjunction of connectivity modulation. Model 2 (2-stage model), Adjunction of local feedbacks. Model 3 (2-stage model), Adjunction of long-range feedbacks from structures of the AAS (anterior affective system). Model 4 (2-pathway model), Adjunction of a direct subcortical retinotectal short-cut pathway to the AAS. Model 5 (2-pathway model), Alternative short-cut pathways to the AAS via the inferior longitudinal and frontal–occipital fasciculi. Model 6 (2-pathway model), Combination of models 4 and 5. Orange circles, "Synapses" at which modulation by emotional competence of the stimuli is implemented.