In addition to this lateralization of some functions, the low-level representations also tend to represent the contralateral side of the body. Each agent had access to the structure of each grid-world on each trial in the form of a transition function T(s, A, s′). This transition function defined the probability of transitioning from location s to location s′ having made the cardinal movement A. As movement in the grid-worlds was deterministic, this probability was always either one or zero. This was done to mirror human participants who have access to visual information indicating a spatial relationship between states as well as the locations of goals and the presence of barriers. We note that the spatial planning component of this task was intended to be simple for human participants.
If this is the case, it could help interpret our finding that the variability/asymmetry correlation was stronger for thickness than for surface area or local gyrification. If variations in cortical thickness have greater experience-based plasticity than do surface area variations, then its stronger association with asymmetry would implicate greater experiential effects on thickness asymmetry. A, B Number of times each goal was selected by the independent, joint and meta computational agents in test contexts 1 & 2 , which shared the low-popularity transition function, and in test contexts 3 & 4 , which shared the high-popularity transition function. C, D Like the independent agent, subjects chose goal A more frequently than the other goals across both contexts. However, the form of clustering assumed in these models introduces normative challenges that may prevent them from scaling to ecological problems.
This second approach is similar to traditional anatomical methods, but eliminates the need for human identification of anatomical regions and manual measurements. However, the sulcal boundaries used to parcellate the cortex may not represent the optimal means to reveal regions with differing asymmetries, as values are summed or averaged across all vertices/voxels within each region. Asymmetry of function is a hallmark feature of brain organization in the human cortex. It is sometimes claimed that structural cerebral asymmetries are small and of minor significance compared to strong and prominent functional asymmetries (e.g., Wey et al., 2014). If so, then one would need to argue that functional asymmetries arise primarily from differing patterns of brain activity that are subserved by similar anatomical substrates (e.g., differing functional connectivity networks – see Wey et al., 2014).
Subjects were instructed that each context was paired with a single mapping and a single rewarded goal location and asked to use their left-hand and right-hand to navigate. Subjects were instructed that the shared color of the agent and goal cued the mapping and the value of the goals and that this relationship was constant across all trials with the same color. As an additional memory cue in experiment 2, each trial was labeled with a “room number” consistent with its context and all trials in a context within the experiment shared the same pattern of walls.
It is not well understood how human learners generalize component knowledge in reinforcement learning tasks. If humans learners decompose task structures into rewards and transitions and act adaptively, then we would expect their generalization behavior to vary between a joint and compositional strategy as the statistics of the task environment changes. Previous models have considered how agents and animals can cluster “latent states” across multiple contexts that share task statistics in both Pavlovian and instrumental learning settings .
The temporal pole is located between the frontal and occipital poles, and sits in the anterior part of middle cranial fossa in each temporal lobe. Cell bodies of the sensory cash aisle reviews neurons of the spinal nerves are located in ________. The vital centers for the control of heart rate, respiration, and blood pressure are located in the ________.
However, the size and direction of asymmetry varies over regions, over the metrics of cortical structure, and across individuals. Such variability is to be expected for a complex biological system such as the human brain. Second, the differing regional organization of the three cortical metrics implies that there are multiple, only partially overlapping, maps of structural asymmetry.
We examined 68 cortical parcellations that had acceptable concordances with manual measurements (Destrieux et al., 2010)2. The individual surfaces are nonlinearly warped back into individual subject space prior to analyses (Destrieux et al., 2010). Three additional studies employed varying methods to investigate point-to-point cortical thickness asymmetries across the entire adult brain. Luders et al. examined 60 young adults and observed thicker left than right cortex in the ACC, anterior temporal and prefrontal cortex, precentral and supramarginal gyri. Rightward thickness asymmetries were observed in the IFG, lateral posterior ITG, precuneus and lingual gyrus. Two other investigations examined age-related changes in cortical thickness asymmetry from childhood to late middle age (Plessen et al., 2014; Zhou et al., 2013).
Thus, the meta-generalization agent favors joint or independent clustering to the degree to which it predicts unseen rewards. Is not under close genetic control (Eyler et al., 2014; Chen et al., 2012, 2013). Such findings suggest that the variability/asymmetry association observed in the current study may be a reflection of more experiential sources of variation. It has been reported that cortical thickness has somewhat lower heritability estimates than does surface area (Eyler et al., 2012; Panizzon et al., 2009; but see also Winkler et al., 2010).
