Cortex orbitofrontal | EPFL Graph Search

The orbitofrontal cortex (OFC) is a prefrontal cortex region in the frontal lobes of the brain which is involved in the cognitive process of decision-making. In non-human primates it consists of the association cortex areas Brodmann area 11, 12 and 13; in humans it consists of Brodmann area 10, 11 and 47. The OFC is functionally related to the ventromedial prefrontal cortex. Therefore, the region is distinguished due to the distinct neural connections and the distinct functions it performs. It is defined as the part of the prefrontal cortex that receives projections from the medial dorsal nucleus of the thalamus, and is thought to represent emotion, taste, smell and reward in decision making. It gets its name from its position immediately above the orbits in which the eyes are located. Considerable individual variability has been found in the OFC of humans. A related area is found in rodents. The OFC is divided into multiple broad regions distinguished by cytoarchitecture, including brodmann area 47/12, brodmann area 11, brodmann area 14, brodmann area 13, and brodmann area 10. Four gyri are split by a complex of sulci that most frequently resembles a "H" or a "K" pattern. Extending along the rostro-caudal axis, two sulci, the lateral and orbital sulci, are usually connected by the transverse orbital sulcus, which extends along a medial-lateral axis. Most medially, the medial orbital gyrus is separated from the gyrus rectus by the olfactory sulcus. Anteriorly, both the gyrus rectus and the medial part of the medial orbital gyrus consist of area 11(m), and posteriorly, area 14. The posterior orbital gyrus consists mostly of area 13, and is bordered medially and laterally by the anterior limbs of the medial and lateral orbital sulci. Area 11 makes up a large part of the OFC involving both the lateral parts of the medial orbital gyrus as well as the anterior orbital gyrus. The lateral orbital gyrus consists mostly of area 47/12. Most of the OFC is granular, although the caudal parts of area 13 and area 14 are agranular.

Dynamics of brain function in preterm-born young adolescents

Lorena Gonçalves de Alcântara e Freitas Krikler

Preterm birth is a major risk factor for neurodevelopment impairments often only appearing later in life. The brain is still at a high rate of development during adolescence, making this a promising window for intervention. It is thus crucial to understand the mechanisms of altered brain function in this population. The aim of this thesis is to investigate how the brain dynamically reconfigures its own organisation over time in preterm-born young adolescents. Research to date has mainly focused on structural disturbances or in static features of brain function in this population. However, recent studies have shown that brain activity is highly dynamic, both spontaneously and during performance of a task, and that small disruptions in its complex architecture may interfere with normal behaviour and cognitive abilities. This thesis explores the dynamic nature of brain function in preterm-born adolescents in three steps: First, we investigate changes in spontaneous brain activity over time using a resting-state paradigm. Here, we study how the variability of the blood oxygenation level dependent signal (BOLD), a measure previously linked to cognitive performance, develops in a preterm- and a term-born groups. We find that preterm participants show an altered trajectory of BOLD variability development during early adolescence. We also show that the dynamic patterns of co-activation with the dorsal anterior cingulate cortex (ACC), a key node of the salience network, also develop differently between the preterm and control groups. Secondly, we examine task-driven changes in brain activation. To this end, we select a reality filtering task known to engage the orbitofrontal cortex (OFC), a region that is particularly vulnerable in the preterm. We find that, although the preterm group is able to perform the task successfully, OFC activation is significantly higher in the control participants. Finally, inspired by the successful field of dynamic functional connectivity which has mainly flourished in resting-state paradigms, we develop a novel method to look into task-driven modulations of brain connectivity in a time-resolved way. We then apply this new approach to a third data set involving a movie watching and emotion regulation task. We find several subtle but significant seed; task; and group effects that characterise each of the dynamic co-activation patterns. In short, we introduce a method for time-resolved evaluation of task-driven changes in brain connectivity and provide evidence of altered brain dynamics in preterm-born young adolescents. Our results thus highlight the importance of considering the dynamic aspects of brain function when studying clinical populations.

EPFL2020

Differential impact of polysialyltransferase ST8SiaII and ST8iaIV knockout on social interaction and aggression

Maria del Carmen Sandi Perez, Reto Bisaz, Cristina Marquez Vega, Martina Fantin

Previous studies using neuronal cell adhesion molecule (NCAM) -/- knockout (KO) mice provided evidence for a role of NCAMs in social behaviors. However, polysialic acid (PSA), the most important post-translational modification of NCAM, was also absent in these mice, which makes it difficult to distinguish between the specific involvement of either PSA or NCAM in social interactions. To address this issue, we assessed two lines of mice deficient for one of the two sialyltransferase enzymes required for the polysialylation of NCAM, sialyltransferase-X (St8SiaII or STX) and polysialyltransferase (ST8SiaIV or PST), in a series of tests for social behaviors. Results showed that PST KO mice display a decreased motivation in social interaction. This deficit can be partly explained by olfactory deficits and was associated with a clear decrease in PSA-NCAM expression in all brain regions analyzed (amygdala, septum, bed nucleus of the stria terminalis and frontal cortices). STX KO mice displayed both a decreased social motivation and an increased aggressive behavior that cannot be explained by olfactory deficits. This finding might be related to the reduced anxiety-like behavior, increased locomotion and stress-induced corticosterone secretion observed in these mice. Moreover, STX KO mice showed mild increase of PSA-NCAM expression in the lateral septum and the orbitofrontal cortex. Altogether, these findings support a role for PSA-NCAM in the regulation of social behaviors ranging from a lack of social motivation to aggression. They also underscore STX KO mice as an interesting animal model that combines a behavioral profile of violence and hyperactivity with reduced anxiety-like behavior.

Wiley-Blackwell2010

Dynamics of brain function in preterm-born young adolescents

Lorena Gonçalves de Alcântara e Freitas Krikler

EPFL2020