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Dorsal vs Posterior and Ventral vs Anterior

Dorsal vs Posterior and Ventral vs Anterior


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From prior reading, I thought that Dorsal is the same as Posterior and Ventral is the same as Anterior. However, when I checked in google images for these anatomical terms for a horse (just to strengthen my concept), i found that Dorsal is not the same as Posterior and Ventral is not the same as Anterior.

How is this possible? I have checked many websites but all state that Dorsal is the same as Posterior and Ventral is the same as Anterior. Am I going wrong somewhere?


Short Answer

This page on wikipedia gives a good synopsis of these concepts.

The confusion lies in the fact that many websites on anatomy discuss/describe/define these terms in relation to humans. However, in quadrupeds and fish (and birds), Anterior/Posterior lies orthogonal to Ventral/Dorsal and are instead synonymous with Cranial(Rostral)/Caudal. Examining the etymologies of the 4 terms in question will demonstrate why there seems to be an inconsistency in their usage:

Ventral -> "belly" side Dorsal -> "back" side Anterior -> "before" or "toward the front" Posterior -> "after" or coming after (opposite to) the anterior

Based on the body orientation of the organism (often associated with forms of locomotion), these terms can sometimes overlap (as in bipedal humans) but often lie perpendicular to each other (as in quadrupeds, fish and most birds).

  • A note about quadrupedalism (as summarized on Wikipedia [my emphasis added]):

    Although the words quadruped and tetrapod are both derived from terms meaning "four-footed", they have distinct meanings. A tetrapod is any member of the taxonomic unit Tetrapoda (which is defined by descent from a specific four-limbed ancestor) whereas a quadruped actually uses four limbs for locomotion.


Long Answer

Think of ventral (Latin venter = "belly") as being associated with the belly side (with belly referring to "swelling" or "inflating") -- or typically the side of the organism containing the digestive and respiratory organs. Dorsal (from Latin dorsum meaning "back") refers to the body region/"side" opposite that of ventral (and typically called the "back").

Anterior (from Latin ante meaning "before" or "in front of") refers to the "front" of the organism (i.e., the part of the organism you'd encounter 1st or before other body regions). Posterior (from Latin, comparative of posterus ("following") from post- meaning "after") is the opposite and refers to the part of the organism encountered "after" (or opposite) the anterior side.

Depending on the orientation of the organism, these terms may be synonymous in some instances but be orthogonal in other instances).

Sometimes anterior/posterior would be synonymous with ventral/dorsal, as is the case in humans or other bipedal organisms.

In other instances (e.g., in quadrupeds, fish or birds), posterior/anterior lies relatively orthogonal to the dorsal/ventral orientation. In these cases, dorsal/ventral is instead synonymous with superior (from Latin superior, comparative of superus "that is above," from super "above") and inferior (from Latin inferus meaning "low" or "below").

  • Often in these cases, anterior/posterior are instead associated with caudal/cranial (common alternatives for cranial include cephalic or rostral). Caudal (from Latin cauda meaning "tail") refers to the tail side of the organism (i.e., the side associated with coccygeal vertebrae or sometimes simply the side of the organism where waste is excreted). Conversely, cranial (Greek kranion = "skull") or cephalic (from Latin cephalicus, from Greek kephalikos, from kephalē meaning "head") refer to the side of the organism containing the head. Rostral (referring to rostrum from Latin meaning "beak") is another synonym for cranial and refers to being "situated or occurring near the front end of the body, especially in the region of the nose and mouth or (in an embryo) near the hypophyseal region."

Some notes:

  • This English.SE question addresses etymology of the suffix "-erior."

  • You can find a pretty good list of anatomical etymologies here, here, here, or by simply searching "[word of interest] etymology" in Google.

  • Also, this Bio.SE post addresses anatomical terminology usage in plants and body organs.


More generally, a frontal plane always divides an organism into ventral/dorsal.

Although these terms differ between shapes/orientations of organisms, using such terms for more specific body parts (e.g., heads or feet) are not always as inconsistent.

  • For example, anatomical positional terminology for brains is consistent across organisms.

One final note:

This approach to anatomical positional terminology only works with bilaterally symmetrical organisms. See here for terminology usage for other organisms.


Dorsal vs posterior y ventral vs anterior

De la lectura anterior, pensé que Dorsal es lo mismo que Posterior y Ventral es lo mismo que Anterior. Sin embargo, cuando revisé en google imágenes estos términos anatómicos para un caballo (solo para fortalecer mi concepto), descubrí que Dorsal no es lo mismo que Posterior y Ventral no es lo mismo que Anterior.

¿Cómo es esto posible? He revisado muchos sitios web, pero todos afirman que Dorsal es igual a Posterior y Ventral es igual a Anterior. ¿Me estoy equivocando en alguna parte?

Graham Chiu

WYSIWYG ♦


Developmental Biology. 6th edition.

Vertebrate axes do not form from localized determinants in the various blastomeres, as in Drosophila. Rather, they arise progressively through a sequence of interactions between neighboring cells. Amphibian axis formation is an example of regulative development. In Chapter 3, we discussed the concept of regulative development, wherein (1) an isolated blastomere has a potency greater than its normal embryonic fate, and (2) a cell's fate is determined by interactions between neighboring cells. Such interactions are called inductions (see Chapter 6). That such inductive interactions were responsible for amphibian axis determination was demonstrated by the laboratory of Hans Spemann at the University of Freiburg. The experiments of Spemann and his students framed the questions that experimental embryologists asked for most of the twentieth century, and they resulted in a Nobel Prize for Spemann in 1935. More recently, the discoveries of the molecules associated with these inductive processes have provided some of the most exciting moments in contemporary science.

The experiment that began this research program was performed in 1903, when Spemann demonstrated that early newt blastomeres have identical nuclei, each capable of producing an entire larva. His procedure was ingenious: Shortly after fertilizing a newt egg, Spemann used a baby's hair taken from his daughter to lasso the zygote in the plane of the first cleavage. He then partially constricted the egg, causing all the nuclear divisions to remain on one side of the constriction. Eventually, often as late as the 16-cell stage, a nucleus would escape across the constriction into the non-nucleated side. Cleavage then began on this side, too, whereupon Spemann tightened the lasso until the two halves were completely separated. Twin larvae developed, one slightly older than the other (Figure 10.17). Spemann concluded from this experiment that early amphibian nuclei were genetically identical and that each cell was capable of giving rise to an entire organism.

Figure 10.17

Spemann's demonstration of nuclear equivalence in newt cleavage. (A) When the fertilized egg of the newt Triturus taeniatus was constricted by a ligature, the nucleus was restricted to one-half of the embryo. The cleavage on that side of the embryo reached (more. )

However, when Spemann performed a similar experiment with the constriction still longitudinal, but perpendicular to the plane of the first cleavage (separating the future dorsal and ventral regions rather than the right and left sides), he obtained a different result altogether. The nuclei continued to divide on both sides of the constriction, but only one side—the future dorsal side of the embryo—gave rise to a normal larva. The other side produced an unorganized tissue mass of ventral cells, which Spemann called the Bauchst࿌k—the belly piece. This tissue mass was a ball of epidermal cells (ectoderm) containing blood and mesenchyme (mesoderm) and gut cells (endoderm), but no dorsal structures such as nervous system, notochord, or somites (Figure 10.18).

Figure 10.18

Asymmetry in the amphibian egg. (A) When the egg is divided along the plane of first cleavage into two blastomeres, each of which gets one-half of the gray crescent, each experimentally separated cell develops into a normal embryo. (B) When only one of (more. )

Why should these two experiments give different results? One possibility was that when the egg was divided perpendicular to the first cleavage plane, some cytoplasmic substance was not equally distributed into the two halves. Fortunately, the salamander egg was a good place to test that hypothesis. As we have seen in Chapter 7 and above, there are dramatic movements in the cytoplasm following the fertilization of amphibian eggs, and in some amphibians these movements expose a gray, crescent-shaped area of cytoplasm in the region directly opposite the point of sperm entry. This area has been called the gray crescent. Moreover, the first cleavage plane normally splits the gray crescent equally into the two blastomeres. If these cells are then separated, two complete larvae develop. However, should this cleavage plane be aberrant (either in the rare natural event or in an experiment), the gray crescent material passes into only one of the two blastomeres. Spemann found that when these two blastomeres are separated, only the blastomere containing the gray crescent develops normally.

WEBSITE

10.3 Embryology and individuality. One egg usually makes only one adult. However, there are exceptions to this rule, and Spemann was drawn into embryology through the paradoxes of creating more than one individual from a single egg. http://www.devbio.com/chap10/link1003.shtml

It appeared, then, that something in the gray crescent region was essential for proper embryonic development. But how did it function? What role did it play in normal development? The most important clue came from the fate map of this area of the egg, for it showed that the gray crescent region gives rise to the cells that initiate gastrulation. These cells form the dorsal lip of the blastopore. The cells of the dorsal lip are committed to invaginate into the blastula, thus initiating gastrulation and the formation of the notochord. Because all future amphibian development depends on the interaction of cells rearranged during gastrulation, Spemann speculated that the importance of the gray crescent material lies in its ability to initiate gastrulation, and that crucial developmental changes occur during gastrulation.

In 1918, Spemann demonstrated that enormous changes in cell potency do indeed take place during gastrulation. He found that the cells of the early gastrula were uncommitted, but that the fates of late gastrula cells were determined. Spemann demonstrated this by exchanging tissues between the gastrulae of two species of newts whose embryos were differently pigmented (Figure 10.19). When a region of prospective epidermal cells from an early gastrula was transplanted into an area in another early gastrula where the neural tissue normally formed, the transplanted cells gave rise to neural tissue. When prospective neural tissue from early gastrulae was transplanted to the region fated to become belly skin, the neural tissue became epidermal (Table 10.1). Thus, these early newt gastrula cells were not yet committed to a specific fate. Such cells are said to exhibit conditional (i.e., regulative or dependent) development because their ultimate fates depend on their location in the embryo. However, when the same interspecies transplantation experiments were performed on late gastrulae, Spemann obtained completely different results. Rather than differentiating in accordance with their new location, the transplanted cells exhibited autonomous (or independent, or mosaic) development. Their prospective fate was determined, and the cells developed independently of their new embryonic location. Specifically, prospective neural cells now developed into brain tissue even when placed in the region of prospective epidermis, and prospective epidermis formed skin even in the region of the prospective neural tube. Within the time separating early and late gastrulation, the potencies of these groups of cells had become restricted to their eventual paths of differentiation. Something was causing them to become determined to epidermal and neural fates. What was happening?

Figure 10.19

Determination of ectoderm during newt gastrulation. Presumptive neural ectoderm from one newt embryo is transplanted into a region in another embryo that normally becomes epidermis. (A) When the tissues are transferred between early gastrulas, the presumptive (more. )

Table 10.1

Results of tissue transplantation during early- and late-gastrula stages in the newt.


Anatomy diagram source

The ventral surfaces of the body include the chest abdomen shins palms and soles. It is made up of the thoracic cavity and the abdominopelvic cavity.

Spinal Arterial Anatomy Neuroangio Org

Ventral of or relating to the underside of an organism or that side which is normally directed downwards in the usual stance or resting position.

What does ventral mean in anatomy. The upper side of a leaf is known as the adaxial surface. Being or located near on or toward the lower surface of an animal as a quadruped opposite the back or dorsal surface. Try jira for free.

Situated on or toward the lower abdominal plane of the body. If talking about the skull the dorsal side is the top. Ventral can mean closer to the abdomen below or the bottom surface of an object such as ventral surface of the tongue bottom side.

One tool is enough to track issues release great software. The abdominopelvic cavity is further divided into the abdominal cavity and pelvic cavity but there is no physical barrier between the two. The feedback you provide will help us show you more relevant.

Being or located near on or toward the front or anterior part of the human body. Ventral is a term of location used in anatomy which means the anterior part of the body frontbelly and dorsal means the posterior part back. Equivalent to the front or anterior in humanscompare dorsal1def 2.

Of or relating to the belly. Pertaining to the front or anterior of any structure. These two terms used in anatomy and embryology refer to back dorsal and front or belly ventral of an organism.

In bipedal primates such as humans the ventral side is the front which would become the underside if a four legged gait were assumed. Asked in human anatomy and physiology what is the medical term. Of or designating the lower or inner surface of a structure.

Ventral body cavity the ventral body cavity is a human body cavity that is in the anterior front aspect of the human body. Medical definition of ventral. Ventral nearest to or facing toward the axis of an organ or organism.

The ventral surfaces of the body include the chest abdomen shins palms and soles. You dismissed this ad. Of or relating to the venter or belly.

Biological science biology the science that studies living organisms. The dorsal from latin dorsum meaning back surface of an organism refers to the back or upper side of an organism.

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What Does Dorsal Mean In Anatomy

From the latin venter meaning belly. Relating to the back or posterior of a structure.

Anatomy Of The Xenopus Brain Diagrams Showing A Dorsal View

Pertaining to the front or anterior of any structure.

What does dorsal mean in anatomy. Dorsal of an animal the part that normally occurs uppermost. Situated on or toward the upper side of the body equivalent to the back or posterior in humans. A few of the dorsal areas regarding the human anatomy will be the back bottom calves as well as the knuckle side of the hand.

Dorsaladj a hanging usually of rich stuff at the back of a throne or of an altar or in any similar position. Some of the dorsal surfaces of the body are the back buttocks calves and the knuckle side of the hand. Relating to the straight back or posterior of a structure.

Botany of or on the surface of an organ or part. Anatomy of toward on in or near the back or upper surface of an organ part or organism. Ventral is as opposed to dorsal.

Medical definition of dorsal. As opposed to the ventral or front of the structure. See also dorsiventral leaf.

Of a plant of or situated on the side of an organ that is directed away from the axis. These two terms used in anatomy and embryology refer to back dorsal and front or belly ventral of an organism. For a more complete listing of terms used in medicine for spatial orientation.

Situated on or toward the posterior plane in humans or toward the upper plane in quadrupeds. Dorsaladj pertaining to the surface naturally inferior as of a leaf. The back of an animal is called the dorsal surface.

As opposed to the ventral or forward associated with the structure. The dorsal from latin dorsum meaning back surface of an organism refers to the back or upper side of an organism. The ventral surfaces of the body include the chest abdomen shins palms and soles.

Dorsaladj pertaining to the surface naturally superior as of a creeping hepatic moss. If talking about the skull the dorsal side is the top. Of relating to or situated at the back or dorsum.

Dorsal synonyms dorsal pronunciation dorsal translation english dictionary definition of dorsal. In primates in the upright position the dorsal surface is directed backwards. By sherman matlock report definition.

For a more complete listing of terms used in medicine for spatial orientation.

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Medial and Lateral

Imagine a line in the sagittal plane, splitting the right and left halves evenly. This is the midline. Medial means towards the midline, lateral means away from the midline.

  • The eye is lateral to the nose.
  • The nose is medial to the ears.
  • The brachial artery lies medial to the biceps tendon.

[caption align="aligncenter"] Fig 1.0 - Anatomical terms of location labelled on the anatomical position.[/caption]

Vertebrate Axis Formation

Even as the germ layers form, the ball of cells still retains its spherical shape. However, animal bodies have lateral-medial (toward the side-toward the midline), dorsal-ventral (toward the back-toward the belly), and anterior-posterior (toward the front-toward the back) axes. As the body forms, it must develop in such a way that cells, tissues, and organs are organized correctly along these axes.

Figure (PageIndex<1>): Body axes: Animal bodies have three axes for symmetry: anterior/posterior (front/behind), dorsal/ventral (back/belly), and lateral/medial (side/middle).

How are these established? In one of the most seminal experiments ever to be carried out in developmental biology, Spemann and Mangold took dorsal cells from one embryo and transplanted them into the belly region of another embryo. They found that the transplanted embryo now had two notochords: one at the dorsal site from the original cells and another at the transplanted site. This suggested that the dorsal cells were genetically programmed to form the notochord and define the dorsal-ventral axis. Since then, researchers have identified many genes that are responsible for axis formation. Mutations in these genes leads to the loss of symmetry required for organism development. Many of these genes are involved in the Wnt signaling pathway.

In early embryonic development, the formation of the primary body axes is a crucial step in establishing the overall body plan of each particular organism. Wnt signaling can be implicated in the formation of the anteroposterior and dorsoventral axes. Wnt signaling activity in anterior-posterior development can be seen in several organisms including mammals, fish, and frogs. Wnt signaling is also involved in the axis formation of specific body parts and organ systems that are a part of later development. In vertebrates, sonic hedgehog (Shh) and Wnt morphogenetic signaling gradients establish the dorsoventral axis of the central nervous system during neural tube axial patterning. High Wnt signaling establishes the dorsal region while high Shh signaling indicates in the ventral region. Wnt is also involved in the dorsal-ventral formation of the central nervous system through its involvement in axon guidance. Wnt proteins guide the axons of the spinal cord in an anterior-posterior direction. Wnt is also involved in the formation of the limb dorsal-ventral axis. Specifically, Wnt7a helps produce the dorsal patterning of the developing limb.


OPINION article

Frank Krueger 1,2 * † , Gabriele Bellucci 3 † , Pengfei Xu 4,5,6 and Chunliang Feng 7 *
  • 1 Department of Psychology, George Mason University, Fairfax, VA, United States
  • 2 School of Systems Biology, George Mason University, Fairfax, VA, United States
  • 3 Max Planck Institute for Biological Cybernetics, T࿋ingen, Germany
  • 4 Shenzhen Key Laboratory of Affective and Social Neuroscience, Center for Brain Disorders and Cognitive Sciences, Shenzhen University, Shenzhen, China
  • 5 Center for Neuroimaging, Shenzhen Institute of Neuroscience, Shenzhen, China
  • 6 Great Bay Neuroscience and Technology Research Institute, Kwun Tong, Hong Kong
  • 7 Guangdong Provincial Key Laboratory of Mental Health and Cognitive Science, Center for Studies of Psychological Application, School of Psychology, South China Normal University, Guangzhou, China

Social norms represent a fundamental grammar of social interactions, as they refer to shared expectations about behaviors of one's social group members (Bicchieri, 1990, 2005 Santos et al., 2018). Based on these expectations, particularly accurate predictions about another person's future behavior are possible𠅎stablishing the preconditions for cooperative interactions. Overall, group prosperity is enhanced when all members comply with social norms (i.e., norm compliance). However, social norms need to be enforced by sanctioning violators (i.e., norm enforcement). For instance, expectations of compliance with a norm of reciprocity may help overcome the fear of being betrayed by a social partner. As cooperation allows for better collective solutions than those attained by self-interested individuals, social groups are interested in enforcing compliance with social norms by their members, and developing tools for successful recognition of norm violators (Fehr and Schurtenberger, 2018). Thus, a fragile balance between incentives for norm enforcement and deterrents for sanctions of violators is required for a well-functioning society.

Interactive economic games, such as the trust game (TG) (Berg et al., 1995) and the ultimatum game (UG) (Güth et al., 1982), provide reliable experimental settings for the investigation of motivational, affective, and socio-cognitive processes involved in social norm compliance and enforcement (Corradi-Dell➬qua et al., 2016 Feng et al., 2017 Engelmann et al., 2019 Krueger and Meyer-Lindenberg, 2019). Based on the learned and internalized social norms, an agent's reciprocal behavior is determined by the evaluation of the expected or experienced kindness of a partner by weighting the partner's intentions (i.e., the underlying motivation in performing an action) and the action outcomes (i.e., positive or negative consequences of an action for oneself and others) (Falk and Fischbacher, 2006).

Recent work has shown that individuals integrate this information into their beliefs about another person's character traits for reliable predictions of the other's most likely behavior in a new social interaction (Krueger et al., 2009 Bellucci et al., 2019b Dorfman et al., 2019). Hence, reliably estimating the kindness/unkindness of a partner facilitates norm compliance (i.e., positive reciprocity) or norm enforcement (i.e., negative reciprocity) across contexts and time. Importantly, the ability to learn from feedback about a partner's intentions and action outcomes heavily hinges on the degree to which feedback information violates one's priors and expectations (Fouragnan et al., 2013 Dorfman et al., 2019 Bellucci and Park, 2020). The ability to detect expectancy violations might even counteract biases in belief updating about another person's benevolence or malevolence.

Integrating neuroimaging data from economic games across a plethora of neuroimaging studies via coordinate-based meta-analyses (Feng et al., 2015 Bellucci et al., 2017a)—in combination with task-based and task-free functional connectivity analyses (Gurevitch et al., 2018)—has revealed the right anterior insula (R AI) as a candidate brain region for detection of norm deviations in trusting (i.e., trust game) and fairness-related (i.e., ultimatum game) interactions (Krueger et al., 2008 Bellucci et al., 2018). Representing a posterior-to-anterior remapping of interoceptive signals within the insular cortex, the R AI takes a crucial role in salience detection across multiple domains, whereas the posterior insular cortex mediates sensorimotor processes (Craig, 2009). Being part of the salience network (SAN), two functionally distinct brain regions within the R AI𠅊 dorsal AI (dAI) and ventral AI (vAI) cluster—have been identified Kelly et al., 2012 Chang et al., 2013 Wager and Barrett, 2017). Whereas the R dAI act as a switch that exerts direct influences on the central executive network (CEN, i.e., cognitive control system, including high-order executive functions Seeley et al., 2007 Bressler and Menon, 2010 Menon, 2011 Sheffield et al., 2015 and the default-mode network (DMN, i.e., social cognition system, including autobiographical memory, self-monitoring, and theory of mind Andrews-Hanna et al., 2010 Bressler and Menon, 2010 Menon, 2011), the R vAI exerts direct influence on limbic cortices (which mediate affective processes) (Sridharan et al., 2008 Goulden et al., 2014 Uddin et al., 2014). These AI subregions𠅎ncoding a common currency of aversion—were both found consistently activated for responses to unfair behavior but differently engaged by trust and trustworthiness behaviors (Bellucci et al., 2018). In particular, the dAI was preferentially engaged by trust behavior while the vAI by trustworthiness behavior (Bellucci et al., 2018). We propose that consistent recruitment of the AI during those social behaviors is a signature of their common neural processing related to expectancy violation in the form of deviations from social norms. In particular, social behaviors in the TG and UG, such as trust in unknown partners, trustworthiness during repeated interactions and rejection of unfair offers, imply violations of two fundamental social norms �irness and reciprocation. With this respect, they require evaluations of intentions and outcomes of actions that are aligned with individual expectations in case of compliant behaviors but that deviate from individual expectations in case of violations.

When interacting with a stranger in a one-shot TG, in which the investor interacts only once with a trustee, investors feel compelled to comply with a fairness norm and share some fair amount with the trustee. However, the probability that the trustee, whose reputation and past social behavior are supposedly unknown, betrays trust in these circumstances is not negligible. Behavioral studies have repeatedly shown that individuals in these situations worry about a hypothetical, but not much unlikely, defection to occur (Mccabe et al., 1998 Bohnet and Zeckhauser, 2004 Ashraf et al., 2006 Bohnet et al., 2008 Aimone and Houser, 2011, 2013). Individuals might hence begin prospecting to decide whether to trust, for instance, by thinking about what would be most likely that the partner thinks about compliance with a reciprocity norm, and about the reasons for which the partner would consider convenient to violate this norm—processes that likely require the recruitment of the dAI. In iterative interactions, on the contrary, individuals are likely to base their trust decisions on what they have learned from the partner over multiple encounters, switching to a more automatic, knowledge-based decision-making process involving social affiliation regions (Krueger et al., 2007). This is further consistent with the absence of AI signaling during iterative trust decisions with the same partner (Bellucci et al., 2017a).

Reciprocation of trust requires similar evaluations of norm-deviant behaviors by the trustee in a multi-round TG. The concerns that investors have from a second-person perspective, trustees have those from a first-person perspective. In particular, trustees have to weigh the advantages and disadvantages of a cooperative and non-cooperative response to the investor's kind behavior. Also, as the amount of money entrusted by investors in the TG is multiplied by a predetermined factor (usually, tripled), trustees are in an advantageous situation in which defection lures with its convenience. However, defection also implies the violation of a reciprocation norm that will enforce inequality in the payoff distribution between investors and trustees. Hence, trustees might feel guilty of taking advantage of their situation and might fear of what the partner could think of them, especially in iterative interactions where future encounters loom and the importance of a good reputation is more pressing. These aversive feelings are likely encoded in the vAI. On the contrary, in circumstances of low external incentives, such as during reciprocal decisions in single interactions where concerns about what others might think and the pressure of social norm compliance are absent, cognitive control might be required to enact reciprocity. This nicely chimes with the recruitment of dorsolateral prefrontal regions during trustworthiness behavior in single and anonymous interactions (Knoch et al., 2006 Van Den Bos et al., 2011 Nihonsugi et al., 2015).

The receiver in the UG, who faces an unfair offer from the proposer, is in a situation that likely elicits similar psychological processes to those evoked by both investors' and trustees' concerns in the TG. On the one hand, the receiver is confronted with an actual violation of the fairness norm perpetrated by the proposer who sent an unfair offer. Unfair offers elicit negative feelings (e.g., increases in skin conductance activity) in receivers who respond by rejecting the offer. Since the unfair offer implies an actual inequal outcome in resource distributions (given that unfair offers are generally lower than one-third of the resources available to proposers), the receiver might be concerned about the inequality derived from the norm violation. Outcome inequality might hence evoke negative feelings in the receiver that support negative reciprocity via recruitment of the vAI. On the other hand, however, high rejection rates and increased skin conductance activity have been observed only for unfair offers proposed by a human partner, but not for unfair offers generated by computers (Sanfey et al., 2003 Van 'T Wout et al., 2006). These results suggest that the receiver in the UG is further concerned about the intentions of the proposer and is determined to forgo immediate benefits to enforce a fairness norm via a rejection of the offer, which likely recruits the dAI.

Hence, consistent activations of the AI in all these behaviors likely refer to general signaling of violations of expectations about actions that deviate from social norms. However, given the different activation patterns of the dAI and vAI, we here propose an overarching framework in which the R AI—part of the salience network (SAN)—recruits other large-scale brain networks to determine the appropriate reciprocal behavior (via the central-executive network, CEN) based on evaluations about the partner's kindness (via the default-mode network, DMN) (Krueger and Hoffman, 2016 Bellucci et al., 2019a). Hereby, the R AI subregions play a crucial role in signaling how a deviation has occurred, in particular, because of an intentional action (R dAI) or due to an action outcome (R vAI Figure 1).

Figure 1. Framework: Role of R dAI and R vAI in Reciprocity. Based on social norms, an agent's reciprocal behavior is determined by evaluating the expected or experienced kindness/unkindness of a partner's normative action: the intention as the underlying motivation and the outcome as the consequence of the action. The R AI (part of SAN) recruits other large-scale networks to determine the appropriate reciprocity (e.g., lPFC via CEN) based on kindness evaluations (e.g., mPFC via DMN). The R AI subregions play a crucial role in signaling deviations from expectations on outcomes (R vAI) and intentions (R dAI) of an action, facilitating norm compliance (positive reciprocity), and norm enforcement (negative reciprocity). The vAI signals violations of expected outcomes (disadvantageous vs. advantageous outcome inequality) that elicit aversive feelings (anger vs. guilt). The dAI signals violations of expected intentional behaviors (actual vs. hypothetical betrayal) that evoke social-cognitive processes (attribution vs. inference) [Note that brain image adopted from Uddin (2015)]. R, right SAN, Salience Network PI, Posterior Insula AI, Anterior Insula vAI, Ventral Anterior Insula dAI, Dorsal Anterior Insula DMN, Default-mode Network mPFC, Medial Prefrontal Cortex CEN, Central-executive Network, lPFC, Lateral Prefrontal Cortex O+, Positive Outcome O-, Negative Outcome I-, Negative Intention I+, Positive Intention.

We propose that the SAN detects (vAI) and generates an aversive experience based on the salience of the social norm violation and provides an emotional signal (amygdala) encoding the severity of outcome related to the norm violation (Buckholtz et al., 2008). The DMN anchored in the medial prefrontal cortex (mPFC) integrates the outcome (via the ventromedial PFC's inter-network connectivity with SAN) and the intention (via the dorsomedial PFC's intra-network connectivity with the temporoparietal junction, TPJ) of the norm violation into an assessment of kindness (Krueger et al., 2009). The CEN anchored in lateral PFC (lPFC) converts the kindness signal from the DMN into an appropriate reciprocal behavior that fits the norm violation. Previous work has demonstrated that connectivity between the mPFC and lPFC was associated with evaluations of norm violations for appropriate punishment decisions (Bellucci et al., 2017b).

Therefore, in the social settings of the economic paradigms here considered, the vAI likely represents forms of violations of an expected outcome such as outcome inequalities (i.e., less- vs. more-than-equal) that elicit negative feelings via co-activation of the limbic network (e.g., amygdala). In particular, less-than-equal outcomes refer to a situation of disadvantageous inequality that triggers negative feelings such as anger and envy (due to a negative outcome for the self), which support norm enforcement in the form of negative reciprocity (e.g., punishment). On the contrary, more-than-equal outcomes refer to situations of advantageous inequality that likely triggers different negative feelings such as guilt (due to a positive outcome for the self), which compel to norm compliance in the form of positive reciprocity (e.g., cooperation).

The dAI, instead, likely represents forms of violations of an expected intentional behavior such as betrayal (both actual and hypothetical) that elicit social-cognitive processes via co-activation of the default-mode network. In particular, actual deviant behaviors prompt to retrospection on the intentionally perpetrated betrayal that triggers socio-cognitive processes such as attribution of bad intentions, thereby promoting norm enforcement in the form of negative reciprocity (e.g., punishment). On the contrary, hypothetical deviant behaviors prompt to prospection on a possible intentional betrayal that triggers socio-cognitive processes such as inferences on the other's intentions, thereby supporting norm compliance in the form of positive reciprocity (e.g., trust).

Given the proposed neuropsychological model, some predictions for other recently reported activation patterns associated with social normative behaviors are possible. For instance, social interactions in which some form of expectancy violation is involved might require recruitment of the AI. For the classical Prisoner's Dilemma game, where two players can decide to cooperate or betray each other, both parties�ting in their own self-interests𠅌hoose often to protect themselves at the expense of the other player thereby, producing the worst outcome for both parties by non-reciprocation of cooperation (Peterson, 2015). A neuroimaging study employing an iterated version of the Prisoner's Dilemma game showed greater activation in R dAI during unreciprocated compared to reciprocated cooperation when both players were informed about the outcome of each trial game (but not during their decisions) (Rilling et al., 2008). Another study revealed that depressed compared to healthy individuals reported higher levels of negative feelings (i.e., betrayal, guilt) during this game. Across all players, the R vAI was more activated comparing outcomes, where one of the players cooperated and the other defected, with outcomes, where both players either cooperated or defected (Gradin et al., 2016).

Further, shame and embarrassment, which emerge from the recognition that one's behavior diverges from a group's expectancies, should elicit activations in the AI. Preliminary evidence aligns with this prediction and suggests that shame and embarrassment elicit activations particularly in the vAI, consistently with the fact that these negative feelings are based on violations caused by the consequences (and not the intentions) of one's behavior (Muller-Pinzler et al., 2015 Zhu et al., 2019). Similarly, punishment and blame, which rely on the recognition of another's deviant behavior, should recruit the AI as well. Previous evidence chimes with this prediction, pointing specifically to the dAI, consistently with the fact that punishment and blame require socio-cognitive processes for understanding reasons and motives of another's wrongdoing (Krueger and Hoffman, 2016 Patil et al., 2017 Bellucci et al., 2020). On the contrary, other social behaviors such as generosity or altruism should activate the AI only if they also involve expectancy violations. Previous work on these behaviors seems to confirm such prediction (Moll et al., 2006 Coll et al., 2017 Karns et al., 2017), showing AI activations only when a form of expectancy violation is involved such as when helping an offender or breaking a promise to cooperate (Baumgartner et al., 2009 David et al., 2017).

Taken together, the AI is an underestimated but essential brain region for understanding human social cognition and its pathophysiological forms in social brain disorders such as schizophrenia and autism (Namkung et al., 2017). Our framework provides a distinctive mapping of the R AI subdivisions that can be employed in future multimodal neuroimaging studies to test hypotheses on the AI functioning in reciprocity. For this reason, our neuropsychological framework contributes to a more comprehensive understanding of this region for basic and clinical neuroscience in which altered processing in AI subdivisions determine different aspects of prevalent brain disorders (e.g., psychosis, autism).


What Is the Difference Between Dorsal and Ventral?

These terms can become confusing when talking about both bipeds and quadrupeds. The terms "dorsal/posterior" and "ventral/anterior" are only interchangeable for creatures that walk on two legs and stand upright. With an animal that stands on four legs, such as a dog, the head is referred to as the anterior and the tail as the posterior, while the back is referred to as dorsal and the belly as ventral. In quadrupeds like the dog, "anterior" and "posterior" are synonymous with the words "cranial" and "caudal."

These terms are more difficult to use with invertebrate and asymmetrical creatures. Due to the wide variety of body shapes prevalent in such creatures, terms are usually borrowed from vertebrate anatomy and additional terms, such as "proximal," are used to clarify location. Proximal literally means "near."

The terms "dorsal" and "ventral" are not applicable to every organism in existence. Amoebae change shape constantly, so such terms are useless when describing them. In elongated organisms like sponges, which attach themselves to a surface, the terms can be used as the sponge has identifiable ends.


What is the Difference Between Posterior and Anterior?

Posterior refers to something that is at the back or on the bottom, while anterior refers to something being in the front or on the top. Generally speaking, posterior and anterior refer to polar opposites. The terms are used most frequently in anatomy, but the terminology can also be used in zoology, anatomy and references to time, among other things.

Each of these two words can trace its roots to the Latin language. The first instance of the words being used is approximately 1535. The word posterior is a comparative of the word posterus, which means “coming after” and a derivative of the word post. The word anterior is a derivative of the word ante, which means “before.”

In zoology, these words typically refer to the tail and nose of certain organisms. In humans and some other animals, the tail is the buttocks and the nose is the head. To lay prone is to lay on one’s back, or posterior end. The anterior end of vertebrates that have very distinct heads might also be referred to as the rostral end — from the Latin for beak, usually used with birds — or the cranial end — from the Greek for brain — or cephalic end — from the Greek for head. In other organisms, posterior and anterior are usually replaced with the words ventral and dorsal, which would mean the belly and the spine.

In the medical world, the words posterior and anterior refer to the position of certain pieces of anatomy within the bodies of organisms. A gland that is anterior to another is in front of it. Anterior muscles would be muscles on the front or anterior side of the body.

Posterior and anterior can also refer to specific or non-specific points in time. An anterior event is one which comes before a certain date or time, just as a posterior event is one which comes after a certain date or time. So an anterior event precedes a posterior event. This application is typically used by referring to posterity, which means generations that follow. A common phrase is “for posterity’s sake,” which means for the sake of generations to come.